全文获取类型
收费全文 | 2734篇 |
免费 | 248篇 |
专业分类
2982篇 |
出版年
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 36篇 |
2020年 | 23篇 |
2019年 | 36篇 |
2018年 | 58篇 |
2017年 | 43篇 |
2016年 | 86篇 |
2015年 | 115篇 |
2014年 | 136篇 |
2013年 | 147篇 |
2012年 | 201篇 |
2011年 | 198篇 |
2010年 | 151篇 |
2009年 | 142篇 |
2008年 | 178篇 |
2007年 | 166篇 |
2006年 | 133篇 |
2005年 | 130篇 |
2004年 | 134篇 |
2003年 | 140篇 |
2002年 | 129篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 30篇 |
1998年 | 37篇 |
1997年 | 32篇 |
1996年 | 28篇 |
1995年 | 40篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 41篇 |
1991年 | 24篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1975年 | 6篇 |
1972年 | 6篇 |
1970年 | 7篇 |
排序方式: 共有2982条查询结果,搜索用时 15 毫秒
131.
Neuroanatomical Correlates of Intelligence in Healthy Young Adults: The Role of Basal Ganglia Volume
Cosima Rhein Christiane Mühle Tanja Richter-Schmidinger Panagiotis Alexopoulos Arnd Doerfler Johannes Kornhuber 《PloS one》2014,9(4)
Background
In neuropsychiatric diseases with basal ganglia involvement, higher cognitive functions are often impaired. In this exploratory study, we examined healthy young adults to gain detailed insight into the relationship between basal ganglia volume and cognitive abilities under non-pathological conditions.Methodology/Principal Findings
We investigated 137 healthy adults that were between the ages of 21 and 35 years with similar educational backgrounds. Magnetic resonance imaging (MRI) was performed, and volumes of basal ganglia nuclei in both hemispheres were calculated using FreeSurfer software. The cognitive assessment consisted of verbal, numeric and figural aspects of intelligence for either the fluid or the crystallised intelligence factor using the intelligence test Intelligenz-Struktur-Test (I-S-T 2000 R). Our data revealed significant correlations of the caudate nucleus and pallidum volumes with figural and numeric aspects of intelligence, but not with verbal intelligence. Interestingly, figural intelligence associations were dependent on sex and intelligence factor; in females, the pallidum volumes were correlated with crystallised figural intelligence (r = 0.372, p = 0.01), whereas in males, the caudate volumes were correlated with fluid figural intelligence (r = 0.507, p = 0.01). Numeric intelligence was correlated with right-lateralised caudate nucleus volumes for both females and males, but only for crystallised intelligence (r = 0.306, p = 0.04 and r = 0.459, p = 0.04, respectively). The associations were not mediated by prefrontal cortical subfield volumes when controlling with partial correlation analyses.Conclusions/Significance
The findings of our exploratory analysis indicate that figural and numeric intelligence aspects, but not verbal aspects, are strongly associated with basal ganglia volumes. Unlike numeric intelligence, the type of figural intelligence appears to be related to distinct basal ganglia nuclei in a sex-specific manner. Subcortical brain structures thus may contribute substantially to cognitive performance. 相似文献132.
Labarthe MC Halanek N Birchall L Russell N Desel C Todryk S Peters MJ Lucas A Falkenberg FW Dalgleish AG Whelan M Ward SJ 《Cancer immunology, immunotherapy : CII》2006,55(3):277-288
Allogeneic whole tumour cell vaccines are inherently practical compared with autologous vaccines. Cell lines are derived from
allogeneic tumour, grown in bulk and then administered as a vaccine to the patient, following irradiation, which not only
prevents any replication but also enhances antigen presentation. Protection is believed to occur through the presentation
of antigens shared between the syngeneic and allogeneic tumours. Although cytokine-transfected tumour whole cell vaccines
have been used clinically, little data is available comparing the effects of immunomodulatory cytokine-transfection directly
on the same cells when used as both an allogeneic and autologous vaccine. To address this, weakly immunogenic B16-F10 (H-2b) murine melanoma was transfected to secrete either GM-CSF, IL-4 or IL-7. Prophylactic vaccination of both syngeneic C57/BL6
(H-2b) (B6) and allogeneic C3H/Hej (H-2k) (C3H) mice showed the effects of transfected cytokine varied between models. Both GM-CSF and IL-7 significantly (P<0.05) increased the levels of protection within syngeneic B6 mice, but had a diminished effect (P>0.05) within C3H allogeneic mice. Allogeneic B16-F10 cells and syngeneic K1735 cells generated CTL against K1735 suggesting
cross-reactive immunity. Using cells labeled with fluorescent dye we demonstrate that irradiated vaccines, of either syngeneic
or allogeneic origin, appear to generate potent immune responses and fragments of either vaccine remain at the injection site
for up to 9 days. This study shows that protection can be enhanced in vivo by using transfected cytokine, but suggests that
irradiated whole cell vaccines, of either tissue-type, are rapidly processed. This leads to the conclusion that the cytokine
effects are transient and thus transfection with cytokine may be of limited long-term use in situ. 相似文献
133.
Hernandez-Prieto MA Tibiletti T Abasova L Kirilovsky D Vass I Funk C 《Biochimica et biophysica acta》2011,1807(9):1143-1151
The five small CAB-like proteins (ScpA-E) of the cyanobacterium Synechocystis sp. PCC 6803 belong to the family of stress-induced light-harvesting-like proteins, but are constitutively expressed in a mutant deficient of Photosystem I (PSI). Using absorption, fluorescence and thermoluminescence measurements this PSI-less strain was compared with a mutant, in which all SCPs were additionally deleted. Depletion of SCPs led to structural rearrangements in Photosystem II (PSII): less photosystems were assembled; and in these, the Q(B) site was modified. Despite the lower amount of PSII, the SCP-deficient cells contained the same amount of phycobilisomes (PBS) as the control. Although the excess PBS were functionally disconnected, their fluorescence was quenched under high irradiance by the activated Orange Carotenoid Protein (OCP). Additionally the amount of OCP, but not of the iron-stress induced protein (isiA), was higher in this SCP-depleted mutant compared with the control. As previously described, the lack of SCPs affects the chlorophyll biosynthesis (Vavilin, D., Brune, D. C., Vermaas, W. (2005) Biochim Biophys Acta 1708, 91-101). We demonstrate that chlorophyll synthesis is required for efficient PSII repair and that it is partly impaired in the absence of SCPs. At the same time, the amount of chlorophyll also seems to influence the expression of ScpC and ScpD. 相似文献
134.
Claudia Maletzki Saskia Stier Ulrike Gruenert Michael Gock Christiane Ostwald Friedrich Prall Michael Linnebacher 《PloS one》2012,7(12)
Background
Colorectal cancer (CRC) represents a morphologic and molecular heterogenic disease. This heterogeneity substantially impairs drug effectiveness and prognosis. The subtype of mismatch repair deficient (MMR-D) CRCs, accounting for about 15% of all cases, shows particular differential responses up to resistance towards currently approved cytostatic drugs. Pre-clinical in vitro models representing molecular features of MMR-D tumors are thus mandatory for identifying biomarkers that finally help to predict responses towards new cytostatic drugs. Here, we describe the successful establishment and characterization of three patient-derived MMR-D cell lines (HROC24, HROC87, and HROC113) along with their corresponding xenografts.Methodology
MMR-D cell lines (HROC24, HROC87, and HROC113) were established from a total of ten clinicopathological well-defined MMR-D cases (120 CRC cases in total). Cells were comprehensively characterized by phenotype, morphology, growth kinetics, invasiveness, and molecular profile. Additionally, response to clinically relevant chemotherapeutics was examined in vitro and in vivo.Principal Findings
Two MMR-D lines showing CIMP-H derived from sporadic CRC (HROC24: K-raswt, B-rafmut, HROC87: K-raswt, B-rafmut), whereas the HROC113 cell line (K-rasmut, B-rafwt) was HNPCC-associated. A diploid DNA-status could be verified by flow cytometry and SNP Array analysis. All cell lines were characterized as epithelial (EpCAM+) tumor cells, showing surface tumor marker expression (CEACAM+). MHC-class II was inducible by Interferon-γ stimulation. Growth kinetics as well as invasive potential was quite heterogeneous between individual lines. Besides, MMR-D cell lines exhibited distinct responsiveness towards chemotherapeutics, even when comparing in vitro and in vivo sensitivity.Conclusions
These newly established and well-characterized, low-passage MMR-D cell lines provide a useful tool for future investigations on the biological characteristics of MMR-D CRCs, both of sporadic and hereditary origin. Additionally, matched patient-derived immune cells allow for comparative genetic studies. 相似文献135.
Christiane Contino-Pépin Audrey Parat Sandrine Périno Christine Lenoir Michel Vidal Hervé Galons Stephen Karlik Bernard Pucci 《Bioorganic & medicinal chemistry letters》2009,19(3):878-881
The present work deals with the synthesis of a new series of thalidomide derivatives for therapeutic applications. These compounds were evaluated in vitro on a human endothelial cell line EA.hy926 for their antiproliferative potential and in vivo on an experimental animal multiple sclerosis model called EAE as angiogenesis inhibitors. The preliminary results obtained on EAE assays seem to validate that anti-angiogenesis compounds could be promising tools for the treatment of MS. 相似文献
136.
DNA variation at the invertase locus invGE/GF is associated with tuber quality traits in populations of potato breeding clones 总被引:5,自引:0,他引:5 下载免费PDF全文
Li L Strahwald J Hofferbert HR Lübeck J Tacke E Junghans H Wunder J Gebhardt C 《Genetics》2005,170(2):813-821
Starch and sugar content of potato tubers are quantitative traits, which are models for the candidate gene approach for identifying the molecular basis of quantitative trait loci (QTL) in noninbred plants. Starch and sugar content are also important for the quality of processed products such as potato chips and French fries. A high content of the reducing sugars glucose and fructose results in inferior chip quality. Tuber starch content affects nutritional quality. Functional and genetic models suggest that genes encoding invertases control, among other things, tuber sugar content. The invGE/GF locus on potato chromosome IX consists of duplicated invertase genes invGE and invGF and colocalizes with cold-sweetening QTL Sug9. DNA variation at invGE/GF was analyzed in 188 tetraploid potato cultivars, which have been assessed for chip quality and tuber starch content. Two closely correlated invertase alleles, invGE-f and invGF-d, were associated with better chip quality in three breeding populations. Allele invGF-b was associated with lower tuber starch content. The potato invertase gene invGE is orthologous to the tomato invertase gene Lin5, which is causal for the fruit-sugar-yield QTL Brix9-2-5, suggesting that natural variation of sugar yield in tomato fruits and sugar content of potato tubers is controlled by functional variants of orthologous invertase genes. 相似文献
137.
Christiane Liers Caroline Bobeth Marek Pecyna René Ullrich Martin Hofrichter 《Applied microbiology and biotechnology》2010,85(6):1869-1879
The jelly fungus Auricularia auricula-judae produced an enzyme with manganese-independent peroxidase activity during growth on beech wood (∼300 U l−1). The same enzymatic activity was detected and produced at larger scale in agitated cultures comprising of liquid, plant-based
media (e.g. tomato juice suspensions) at levels up to 8,000 U l−1. Two pure peroxidase forms (A. auricula-judae peroxidase (AjP I and AjP II) could be obtained from respective culture liquids by three chromatographic steps. Spectroscopic
and electrophoretic analyses of the purified proteins revealed their heme and peroxidase nature. The N-terminal amino acid
sequence of AjP matched well with sequences of fungal enzymes known as “dye-decolorizing peroxidases”. Homology was found
to the N-termini of peroxidases from Marasmius scorodonius (up to 86%), Thanatephorus cucumeris (60%), and Termitomyces albuminosus (60%). Both enzyme forms catalyzed not only the conversion of typical peroxidase substrates such as 2,6-dimethoxyphenol and
2,2′-azino-bis(3-ethylthiazoline-6-sulfonate) but also the decolorization of the high-redox potential dyes Reactive Blue 5
and Reactive Black 5, whereas manganese(II) ions (Mn2+) were not oxidized. Most remarkable, however, is the finding that both AjPs oxidized nonphenolic lignin model compounds (veratryl
alcohol; adlerol, a nonphenolic β-O-4 lignin model dimer) at low pH (maximum activity at pH 1.4), which indicates a certain ligninolytic activity of dye-decolorizing
peroxidases. 相似文献
138.
Christophe Rusniok Elisabeth Couvé Violette Da Cunha Rachida El Gana Nora Zidane Christiane Bouchier Claire Poyart Roland Leclercq Patrick Trieu-Cuot Philippe Glaser 《Journal of bacteriology》2010,192(8):2266-2276
Streptococcus gallolyticus (formerly known as Streptococcus bovis biotype I) is an increasing cause of endocarditis among streptococci and frequently associated with colon cancer. S. gallolyticus is part of the rumen flora but also a cause of disease in ruminants as well as in birds. Here we report the complete nucleotide sequence of strain UCN34, responsible for endocarditis in a patient also suffering from colon cancer. Analysis of the 2,239 proteins encoded by its 2,350-kb-long genome revealed unique features among streptococci, probably related to its adaptation to the rumen environment and its capacity to cause endocarditis. S. gallolyticus has the capacity to use a broad range of carbohydrates of plant origin, in particular to degrade polysaccharides derived from the plant cell wall. Its genome encodes a large repertoire of transporters and catalytic activities, like tannase, phenolic compounds decarboxylase, and bile salt hydrolase, that should contribute to the detoxification of the gut environment. Furthermore, S. gallolyticus synthesizes all 20 amino acids and more vitamins than any other sequenced Streptococcus species. Many of the genes encoding these specific functions were likely acquired by lateral gene transfer from other bacterial species present in the rumen. The surface properties of strain UCN34 may also contribute to its virulence. A polysaccharide capsule might be implicated in resistance to innate immunity defenses, and glucan mucopolysaccharides, three types of pili, and collagen binding proteins may play a role in adhesion to tissues in the course of endocarditis.Several studies have reported that the proportion of infective endocarditis due to Streptococcus gallolyticus has increased during the last decades, concomitantly with a decrease of cases due to oral streptococci (35). S. gallolyticus is now becoming the first cause of infectious endocarditis among streptococci in Europe (16). Furthermore, S. gallolyticus endocarditis is associated with rural residency, suggesting transmission from animals (29). However, the reasons for the emergence of this pathogen remain poorly understood. S. gallolyticus belongs to the Streptococcus bovis group known for more than 60 years to cause endocarditis (45). Recently, the former species S. bovis has been divided into four major species (50, 53). S. gallolyticus corresponds to S. bovis biotype I (mannitol fermentation positive), the closely related species S. pasteurianus to biotype II/2 (mannitol negative and β-glucuronidase positive), and the more distantly related species S. infantarius to biotype II/1 (mannitol negative and β-glucuronidase negative). S. macedonicus, the fourth species, commonly found in cheese, is nonpathogenic and also considered a S. gallolyticus subspecies (53, 62). A majority of endocarditis cases was due, among the formerly S. bovis group, to S. gallolyticus strains (4).Multiple studies have shown that endocarditis due to S. gallolyticus as well as positive blood culture for this species is often associated with gastrointestinal malignancy (4, 6). This association has led to a strong indication for gastrointestinal investigation and endoscopic follow-up in the case of S. gallolyticus infections (66). The association of S. gallolyticus infection with colon cancer is a major but still unsolved issue. It may be just incidental, as the alteration of the digestive mucosa may favor the translocation of the bacteria into the bloodstream. Alternatively, the tumor may contribute to the proliferation of S. gallolyticus in close proximity to the gut epithelium, increasing its probability of translocating through the gut barrier. It has also been suggested that the bacterium itself contributes to carcinogenesis (60, 69). In addition to human disease, S. gallolyticus may also cause diseases in animals, like septicemia in pigeons (19), outbreaks in broiler flocks (11), or bovine mastitis (28).Independent from its association to disease, S. gallolyticus has been isolated as a tannin-resistant bacterium from the feces of different mammalian herbivores, including the koala (48) or the Japanese large wood mouse (52), and it is also a normal inhabitant of the rumen (39). Its resistance to tannins is linked to its tannase activity, a characteristic which also led this bacterium to be named “gallolyticus” as it is able to decarboxylate gallate, an organic acid derived from tannin degradation. S. gallolyticus is also known to express other degradative functions unique among streptococci, like a bile salt hydrolase or an amylase. These properties allow its multiplication outside the animal host, as S. gallolyticus was isolated from a digester fed with shea cake (derived from the nuts of the African tree Vitellaria paradoxa) rich in tannins and aromatic compounds (12). S. gallolyticus is a commensal of the human intestinal tract but remains a rarely detected (2.5 to 15%) low-abundance species (10, 40). In herbivores, overgrowth of S. bovis may become deleterious. For example, ingestion of large amounts of rapidly fermented cereal grains leads to a destabilization of the rumen flora and to the proliferation of acid-tolerant bacteria, including S. gallolyticus. This is accompanied by the overproduction of mucopolysaccharides that stabilize the foam, resulting in feedlot bloat, a significant cause of economical loss (14).Virulence and colonization factors of S. gallolyticus in humans are largely unknown. Studies of the bird host have shown that this Streptococcus species expresses a capsular polysaccharide, and five different serotypes have been described (19). In addition, electron microscopy studies have revealed the presence of fimbria-like structures on the surface of S. gallolyticus. It was hypothesized that capsules and/or fimbriae are involved in virulence (63). S. gallolyticus isolates responsible for endocarditis exhibited heterogeneous patterns of adherence to extracellular matrix (ECM) proteins, which suggests that they produce different surface components (55). Recently, a collagen binding adhesin together with 10 putative ECM binding proteins were identified in the draft genome sequence of a human isolate of S. gallolyticus (54).Here we describe the sequence and analysis of the genome of S. gallolyticus strain UCN34 isolated from a human case of endocarditis associated with colon cancer. Analysis of the predicted proteins revealed unique metabolic and cell surface features among streptococci, which contribute to its adaptation to the rumen and to its ability to cause endocarditis. We showed by comparative genomics that many of the corresponding genes were probably acquired by lateral gene transfer (LGT) from other Firmicutes of the gut microbiota. 相似文献
139.
Tran Tinh Hien Nguyen Thi Dung Nguyen Thanh Truong Ninh Thi Thanh Van Tran Nguyen Bich Chau Nguyen Van Minh Hoang Tran Thi Thu Nga Cao Thu Thuy Pham Van Minh Nguyen Thi Cam Binh Tran Thi Diem Ha Pham Van Toi To Song Diep James I. Campbell Elaine Stockwell Constance Schultsz Cameron P. Simmons Clare Glover Winnie Lam Filipe Marques James P. May Anthony Upton Ronald Budhram Gordon Dougan Jeremy Farrar Nguyen Van Vinh Chau Christiane Dolecek 《PloS one》2010,5(7)
Background
The emergence of drug resistant typhoid fever is a major public health problem, especially in Asia. An oral single dose typhoid vaccine would have major advantages. M01ZH09 is a live oral single dose candidate typhoid vaccine containing Salmonella enterica serovar Typhi (Ty2 aroC − ssaV −) ZH9 with two independently attenuating deletions. Studies in healthy adults demonstrated immunogenicity and an acceptable safety profile.Objectives
We conducted a randomised placebo controlled, single-blind trial to evaluate the safety and immunogenicity of M01ZH09 in healthy Vietnamese children aged 5 to 14 years.Methods
Subjects were randomly assigned to receive either a nominal dose of 5×109 CFU of M01ZH09 or placebo and were followed up for 28 days. The primary safety outcome was the proportion of subjects with any adverse event attributed to M01ZH09. The primary immunogenicity endpoint was the proportion of subjects who showed a positive immune response to M01ZH09 in the Salmonella Typhi lipopolysaccharide (LPS) specific serum IgA and IgG ELISA.Principal Findings
One hundred and fifty-one children were enrolled, 101 subjects received M01ZH09 and 50 subjects received placebo. An intention to treat analysis was conducted. There were no serious adverse events and no bacteraemias. In the M01ZH09 group, 26 (26%; 95% CI, 18–5%) of 101 subjects experienced adverse events compared to 11 (22%; 95% CI, 12–36%) of 50 subjects in the placebo group (odds ratio (OR) [95%CI] = 1.23 [0.550–2.747]; p = 0.691). Faecal shedding of S. Typhi (Ty2 aroC − ssaV −) ZH9 was detected in 51 (51%; 95% CI, 41–61%) of 100 M01ZH09 subjects. No shedding was detected beyond day 3. A positive immune response, defined as 70% increase (1.7 fold change) in LPS specific serum IgG (day 14 or 28) and/or 50% increase (1.5 fold change) in LPS specific serum IgA (day 7 or 14) from baseline was detected in 98 (97%; 95% CI, 92–99%) of 101 M01ZH09 recipients and 8 (16%; 95% CI, 7–29%) of 50 placebo recipients. Twenty-eight (100%; 95% CI, 88–100%) of 28 vaccine recipients who were evaluated in the LPS specific IgA ELISPOT assay showed a positive response compared to none of the 14 placebo recipients tested.Conclusions
This was the first phase II trial of a novel oral candidate typhoid vaccine in children in an endemic country. M01ZH09 had an appropriate safety profile and was immunogenic in children.Trial Registration
Controlled-trials.comISRCTN91111837 相似文献140.
Daniel Nobach Manon Bourg Sibylle Herzog Hildburg Lange-Herbst Jorge A. Encarna??o Markus Eickmann Christiane Herden 《PloS one》2015,10(8)