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91.
Lucyna Firlej Bogdan Kuchta Michael W. Roth Carlos Wexler 《Journal of molecular modeling》2011,17(4):811-816
The interplay between the torsional potential energy and the scaling of the 1-4 van der Waals and Coulomb interactions determines
the stiffness of flexible molecules. In this paper we demonstrate for the first time that the precise value of the nonbond
scaling factor (SF)—often a value assumed without justification—has a significant effect on the critical properties and mechanisms
of systems undergoing a phase transition, and that, for accurate simulations, this scaling factor is highly dependent on the
system under consideration. In particular, by analyzing the melting of n-alkanes (hexane C6, dodecane C12, tetracosane C24)
on graphite, we show that the SF is not constant over varying alkane chain lengths when the structural correlated transformations
are concerned. Instead, monotonic decrease of SF with the molecular length drives a cross-over between two distinct mechanisms
for melting in such systems. In a broad sense we show that the choice for SF in any simulation containing adsorbed or correlated
long molecules needs to be carefully considered. 相似文献
92.
Dabu B Mironiuc-Cureu M Jardan D Szmal C 《Roumanian archives of microbiology and immunology》2011,70(4):145-148
Treponema denticola has been associated with gingivitis and chronic periodontitis. The aim of this study was to identify Treponema denticola in subgingival samples using PCR technology and to correlate it with clinical diagnosis of subjects. The study was carried out on seventy patients (20-84 years of age; mean age, 45.06 +/- 12.58) of which 22 individuals with no detectable gingivitis or periodontitis, 4 subjects with chronic gingivitis and 44 subjects with chronic periodontitis. Subgingival plaque samples were collected from five sites in each patient. DNA was extracted from the samples using QIAamp DNA Mini Kit (QIAGEN). Treponema denticola and other four periodontopathogens were found using multiplex polymerase chain reaction followed by a reverse hybridization. The relationship between clinical diagnoses and detection of Treponema denticola was determined with Fisher exact test. The results showed significant differences between diagnostic groups regarding subject proportion. Treponema denticola was detected in 2 out of 22 subjects with no detectable gingivitis or periodontitis, 2 out of 4 subjects with chronic gingivitis, and 40 out of 44 subjects with chronic periodontitis. Our findings suggest that Treponema denticola is closely connected to the initiation and progression of periodontal disease. 相似文献
93.
The HAART therapy has improved life expectancy enabling long latency conditions caused by the hepatitis viruses that became the leading cause of death in HIV infected patients. In this study a group of 300 patients aged from 18 to 63 years were selected in order to assess the prevalence and consequences of HIV and the hepatitis B (HBV), C (HCV) and D (HDV) viruses coinfections. Study groups were designed for each coinfection. These groups were in turn divided in case groups formed of coinfected participants and control groups consisting of mono-infected participants. This classification was obtained by testing the participants for the presence of specific infection markers using the ELISA technique. As a result, in regard to the HIV/HBV coinfection the study group consisted of 16 coinfected participants and 114 HBV-infected participants resulting in a prevalence of the coinfection of 14%. In the case of the HIV/HDV coinfection the study group consisted of 5 coinfected participants and 45 HDV-infected participants. The prevalence of the HIV/HCV coinfection was 25% out of the 170 HCV-infected participants. The effect of the coinfections on the expression and levels of the infection markers was analyzed in constrast to those encountered in the case of the mono-infection. The observed changes in the expression of the specific hepatitis markers indicate the impact of the coinfection with HIV on the progression of the hepatitis infections. In addition, the inadequate immune response towards the hepatitis viruses in the case of the coinfected participants leads to the development of cirrhosis and end stage liver disease. 相似文献
94.
Mateescu B Batista L Cardon M Gruosso T de Feraudy Y Mariani O Nicolas A Meyniel JP Cottu P Sastre-Garau X Mechta-Grigoriou F 《Nature medicine》2011,17(12):1627-1635
Although there is evidence that redox regulation has an essential role in malignancies, its impact on tumor prognosis remains unclear. Here we show crosstalk between oxidative stress and the miR-200 family of microRNAs that affects tumorigenesis and chemosensitivity. miR-141 and miR-200a target p38α and modulate the oxidative stress response. Enhanced expression of these microRNAs mimics p38α deficiency and increases tumor growth in mouse models, but it also improves the response to chemotherapeutic agents. High-grade human ovarian adenocarcinomas that accumulate miR-200a have low concentrations of p38α and an associated oxidative stress signature. The miR200a-dependent stress signature correlates with improved survival of patients in response to treatment. Therefore, the role of miR-200a in stress could be a predictive marker for clinical outcome in ovarian cancer. In addition, although oxidative stress promotes tumor growth, it also sensitizes tumors to treatment, which could account for the limited success of antioxidants in clinical trials. 相似文献
95.
Species in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, are expected to
be in danger of extinction. We hypothesize according to Kisdi’s theory (Am Nat 159:579–596, 2002) that species in fragmented landscapes with isolated habitats in general tend to possess low dispersal. In order to verify
this hypothesis we studied the movement patterns of Stethophyma grossum, a hygrophilous species of wetlands, by mark–release–recapture techniques in a landscape with scattered suitable habitats
over 3 years. The study focused on the major population in this landscape (site #1) as dispersal behaviour was assumed to
be greatest. Actually, marked individuals of S. grossum were never found in any further suitable habitats in close vicinity to site #1. Despite that the peatland meadow of study
site #1 was all over covered with homogenous vegetation only 6% (1.8 ha) of the whole area (30 ha) were occupied by S. grossum. The mean recapture rate over 3 years amounted to 39% with no significant differences between males and females. Both covered
little distances within their mean range size of 1.8 ha; the median distances were 36.91 m for males and 26.65 m for females.
We confirm the hypothesis that sub-populations of species in longstanding naturally isolated habitats, which habitat conditions
have been stable; evolved low dispersal with little movements which are routine movements to find mating partners or food. 相似文献
96.
Elizabeta?BriskiEmail author Melania?E.?Cristescu Sarah?A.?Bailey Hugh?J.?MacIsaac 《Biological invasions》2011,13(6):1325-1340
The global transhipment of ballast water and associated flora and fauna by cargo vessels has increased dramatically in recent
decades. Invertebrate species are frequently carried in ballast water and sediment, although identification of diapausing
eggs can be extremely problematic. Here we test the application of DNA barcoding using mitochondrial cytochrome c oxidase subunit I and 16S rDNA to identify species from diapausing eggs collected in ballast sediment of ships. The accuracy
of DNA barcoding identification was tested by comparing results from the molecular markers against each other, and by comparing
barcoding results to traditional morphological identification of individuals hatched from diapausing eggs. Further, we explored
two public genetic databases to determine the broader applicability of DNA barcodes. Of 289 diapausing eggs surveyed, sufficient
DNA for barcoding was obtained from 96 individuals (33%). Unsuccessful DNA extractions from 67% of eggs in our study were
most likely due to degraded condition of eggs. Of 96 eggs with successful DNA extraction, 61 (64%) were identified to species
level, while 36% were identified to possible family/order level. Species level identifications were always consistent between
methodologies. DNA barcoding was suitable for a wide range of taxa, including Branchiopoda, Copepoda, Rotifera, Bryozoa and
Ascidia. Branchiopoda and Copepoda were respectively the best and worst represented groups in genetic databases. Though genetic
databases remain incomplete, DNA barcoding resolved nearly double the number of species identified by traditional taxonomy
(19 vs. 10). Notorious invaders are well represented in existing databases, rendering these NIS detectable using molecular
methods. DNA barcoding provides a rapid and accurate approach to identification of invertebrate diapausing eggs that otherwise
would be very difficult to identify. 相似文献
97.
Admixed populations such as African Americans and Hispanic Americans are often medically underserved and bear a disproportionately high burden of disease. Owing to the diversity of their genomes, these populations have both advantages and disadvantages for genetic studies of complex phenotypes. Advances in statistical methodologies that can infer genetic contributions from ancestral populations may yield new insights into the aetiology of disease and may contribute to the applicability of genomic medicine to these admixed population groups. 相似文献
98.
Fatigue is often reported after long duration flights. Mild hypobaric hypoxia caused by pressurisation may be involved in this effect through disruption of circadian rhythms, independently of the number of time zones crossed. In this controlled crossover study, we assessed the effects of two levels of hypoxia equivalent to 8000 and 12,000 ft on the circadian rhythm of plasma cortisol, a marker of the circadian time structure. Sixteen healthy young male volunteers (23-39 years) were exposed in a hypobaric chamber for 8 h (08:00-16:00 h) to 8000 ft, followed 4 weeks later to 12,000 ft. Plasma cortisol was assayed during two 24-h cycles (control and hypoxic exposure) every 2h in all subjects. We found a significant change in the pattern of cortisol secretion during both hypoxic exposures, with an initial fall in cortisol followed by a transient rebound, whereas the phase and the 24-h mean level remained unchanged. The change in cortisol pattern followed the alterations in autonomic balance assessed by heart rate variability (HRV) spectral analysis. The normalised high frequencies and the low-to-high frequencies ratio showed a significant shift toward sympathetic dominance with some differences in time course for both altitudes studied. HRV analysis improved the interpretation of cortisol 24-h profiles. Our data, which strongly suggest that prolonged mild hypoxia alters the expression of cortisol circadian rhythm, should be taken into account to interpret secretory rhythm changes after transmeridian flights. 相似文献
99.
Jakóbkiewicz-Banecka J Kloska A Stepnowska M Banecki B Wegrzyn A Wegrzyn G 《Mutation research》2005,578(1-2):175-186
A simple bacterial model for studying effects of human mutations in vivo, when homologous genes exist in bacterial and human cells, is presented. We have constructed Escherichia coli strains bearing different alleles of the metF gene, an ortologue of human MTHFR gene, coding for 5,10-methylenetetrahydrofolate reductase. These strains bear a null mutation in the chromosomal metF gene and different metF alleles on plasmid(s), and thus there are merozygotes mimicking wild-type homozygotes, heterozygotes and recessive mutant homozygotes. The A177V mutantion in metF corresponds to one of the most common MTHFR polymorphism, A222V, which has been shown to be associated with increased levels of homocysteine in plasma that, in turn, causes many serious medical problems. Results of relatively simple and quick experiments with these strains are compatible with previously published reports on effects of the A222V substitution in the product of MTHFR gene. In addition, these results suggest either impairment of formation of heterodimers and/or heterotetramers by wild-type and A177V metF variants or dominance of the wild-type polypepides in such structures. Moreover, positive effects of folic acid and vitamins B2 and B12 on physiology of the mutant cells, suggested on the basis of clinical studies, is confirmed. Therefore, we conclude that the bacterial model described in this report may be a useful tool in studies on human mutations. 相似文献
100.
Wilhelm P Wiede F Meissner A Donhauser N Bogdan C Körner H 《Microbes and infection / Institut Pasteur》2005,7(15):217-1468
The pro-inflammatory cytokine TNF is essential for a protective immune response to some but not all strains of Leishmania major. TNF-deficient mice of a resistant genetic background succumbed rapidly to an infection with L. major BNI. Another member of the TNF superfamily, Fas ligand (FasL), has also been reported to be critical for the immune response to L. major. To test the relative importance of TNF versus FasL for the control of L. major BNI, we infected wildtype C57BL/6 (B6.WT), B6.TNF(-/-), B6.gld and C57BL/6.gld x TNF(-/-) (B6.gld.TNF(-/-)) double-negative mice. Visceral, fatal disease was only observed in B6.TNF(-/-) mice, but not in B6 gld mice. The course of infection and the immune response of B6.gld.TNF(-/-) mice were similar to those of B6.TNF(-/-) mice. B6.gld.TNF(-/-) mice had a high tissue parasite burden and expressed prominent amounts of inducible nitric oxide synthase (iNOS) in the skin, the lymph nodes (LN) and the spleen as previously reported for B6.TNF(-/-) mice, whereas the tissue parasite load and the iNOS expression of B6.gld mice resembled that of B6.WT controls. Neither the TNF- nor the FasL-deficiency exerted a detectable intrinsic effect on the proliferation of T cells. Thus, TNF, but not FasL is essential for the control of L. major BNI. The discrepancy between these and other published data are most likely due to the use of different strains of the pathogen. 相似文献