全文获取类型
收费全文 | 3285篇 |
免费 | 222篇 |
国内免费 | 1篇 |
专业分类
3508篇 |
出版年
2023年 | 14篇 |
2022年 | 31篇 |
2021年 | 47篇 |
2020年 | 41篇 |
2019年 | 36篇 |
2018年 | 44篇 |
2017年 | 36篇 |
2016年 | 88篇 |
2015年 | 140篇 |
2014年 | 159篇 |
2013年 | 216篇 |
2012年 | 258篇 |
2011年 | 245篇 |
2010年 | 139篇 |
2009年 | 119篇 |
2008年 | 198篇 |
2007年 | 199篇 |
2006年 | 182篇 |
2005年 | 183篇 |
2004年 | 168篇 |
2003年 | 152篇 |
2002年 | 152篇 |
2001年 | 33篇 |
2000年 | 25篇 |
1999年 | 26篇 |
1998年 | 31篇 |
1997年 | 36篇 |
1996年 | 18篇 |
1995年 | 21篇 |
1994年 | 30篇 |
1993年 | 26篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 16篇 |
1974年 | 21篇 |
排序方式: 共有3508条查询结果,搜索用时 15 毫秒
91.
92.
Catherine M. Phillips Audrey C. Tierney Pablo Perez‐Martinez Catherine Defoort Ellen E. Blaak Ingrid M. F. Gjelstad Jose Lopez‐Miranda Malgorzata Kiec‐Klimczak Malgorzata Malczewska‐Malec Christian A. Drevon Wendy Hall Julie A. Lovegrove Brita Karlstrom Ulf Risérus Helen M. Roche 《Obesity (Silver Spring, Md.)》2013,21(1):E154-E161
Objective:
Obesity is a key factor in the development of the metabolic syndrome (MetS), which is associated with increased cardiometabolic risk. We investigated whether obesity classification by BMI and body fat percentage (BF%) influences cardiometabolic profile and dietary responsiveness in 486 MetS subjects (LIPGENE dietary intervention study).Design and Methods:
Anthropometric measures, markers of inflammation and glucose metabolism, lipid profiles, adhesion molecules, and hemostatic factors were determined at baseline and after 12 weeks of four dietary interventions (high saturated fat (SFA), high monounsaturated fat (MUFA), and two low fat high complex carbohydrate (LFHCC) diets, one supplemented with long chain n‐3 polyunsaturated fatty acids (LC n‐3 PUFAs)).Results:
About 39 and 87% of subjects classified as normal and overweight by BMI were obese according to their BF%. Individuals classified as obese by BMI (≥30 kg/m2) and BF% (≥25% (men) and ≥35% (women)) (OO, n = 284) had larger waist and hip measurements, higher BMI and were heavier (P < 0.001) than those classified as nonobese by BMI but obese by BF% (NOO, n = 92). OO individuals displayed a more proinflammatory (higher C reactive protein (CRP) and leptin), prothrombotic (higher plasminogen activator inhibitor‐1 (PAI‐1)), proatherogenic (higher leptin/adiponectin ratio) and more insulin resistant (higher HOMA‐IR) metabolic profile relative to the NOO group (P < 0.001). Interestingly, tumor necrosis factor‐α (TNF‐α) concentrations were lower post‐intervention in NOO individuals compared with OO subjects (P < 0.001).Conclusions:
In conclusion, assessing BF% and BMI as part of a metabotype may help to identify individuals at greater cardiometabolic risk than BMI alone. 相似文献93.
p53 Modulates Notch Signaling in MCF‐7 Breast Cancer Cells by Associating With the Notch Transcriptional Complex Via MAML1 下载免费PDF全文
Jieun Yun Ingrid Espinoza Antonio Pannuti Damian Romero Luis Martinez Mary Caskey Adina Stanculescu Maurizio Bocchetta Paola Rizzo Vimla Band Hamid Band Hwan Mook Kim Song‐Kyu Park Keon Wook Kang Maria Laura Avantaggiati Christian R. Gomez Todd Golde Barbara Osborne Lucio Miele 《Journal of cellular physiology》2015,230(12):3115-3127
94.
95.
Sumanta Kumar Pal Yulan Ingrid Lin Bertram Yuh Kara DeWalt Austin Kazarian Nicholas Vogelzang Rebecca A. Nelson 《PloS one》2015,10(8)
Background
Second-line therapy is frequently utilized for metastatic urothelial carcinoma, but there are limited data to guide this approach. While an assessment of overall survival based on registry data may not capture the impact of second- and third-line therapies on clinical outcome, this may be reflected in relative conditional survival (RCS).Methods
Patients with stage IV urothelial carcinoma diagnosed from 1990–2010 were identified from the Surveillance, Epidemiology and End Results (SEER) dataset. The association of clinicopathologic variables with disease specific survival (DSS) was explored through univariate and multivariate analyses. DSS in subgroups divided by time period (1990–2000 v 2001–2010) was compared using the Kaplan-Meier method and log-rank test. One-year RCS at annual landmarks up to 5 years was compared in subgroups divided by time period.Results
Of 261,987 patients diagnosed with urothelial carcinoma from 1990–2010, 3,110 patients met criteria for the current analysis. Characteristics of patients diagnosed between 1990 and 2000 (n = 810) and 2001 to 2010 (n = 2,300) were similar and there was no significant difference in DSS between the two groups. On multivariate analysis, older age (age ≥ 80) was associated with shorter DSS (HR 1.79, 95%CI 1.48–2.15), but no association was found between time period of diagnosis and outcome. One-year RCS improved substantially through successive annual landmarks up to 5 years, but no differences were seen in subgroups divided by time of diagnosis.Conclusions
No difference in RCS was observed amongst patients with stage IV urothelial carcinoma diagnosed from 1990–2000 and 2001–2010. A lack of difference in RCS (more so than cumulative DSS) may reflect a lack of progress in salvage therapies for the disease. 相似文献96.
Pahner I Höltje M Winter S Nürnberg B Ottersen OP Ahnert-Hilger G 《European journal of cell biology》2002,81(8):449-456
Heterotrimeric G-proteins at the plasma membrane serve as switches between heptahelical receptors and intracellular signal cascades. Likewise endomembrane associated G-proteins may transduce signals from intracellular compartments provided they consist of a functional trimer. Using quantitative immunoelectron microscopy we found heterotrimeric G-protein subunits Galpha2, Galpha(q/11), Gbeta2 and Gbeta5 to reside on secretory granules in chromaffin cells of rat adrenal glands.Thus rat chromaffin granules are equipped with functional G-proteins that consist of a specific alpha-, beta- and probably gamma-subunit combination. Serotonin uptake into a crude rat chromaffin granule preparation was inhibited by activated Galphao2 (10 nM) to nearly the same extent as by GMppNp (50 microM) whereas GDPbetaS was ineffective. The data support the idea that vesicular G-proteins directly regulate the transmitter content of secretory vesicles. In this respect Galphao2 appears to be the main regulator of vesicular momoamine transporter activity. 相似文献
97.
Nijholt IM Dolga AM Ostroveanu A Luiten PG Schmidt M Eisel UL 《Cellular signalling》2008,20(10):1715-1724
In diverse neuronal processes ranging from neuronal survival to synaptic plasticity cyclic adenosine monophosphate (cAMP)-dependent signaling is tightly connected with the protein kinase B (PKB)/Akt pathway but the precise nature of this connection remains unknown. In the current study we investigated the effect of two mainstream pathways initiated by cAMP, cAMP-dependent protein kinase (PKA) and exchange proteins directly activated by cAMP (Epac1 and Epac2) on PKB/Akt phosphorylation in primary cortical neurons and HT-4 cells. We demonstrate that PKA activation leads to a reduction of PKB/Akt phosphorylation, whereas activation of Epac has the opposite effect. This effect of Epac on PKB/Akt phosphorylation was mediated by Rap activation. The increase in PKB/Akt phosphorylation after Epac activation could be blocked by pretreatment with Epac2 siRNA and to a somewhat smaller extent by Epac1 siRNA. PKA, PKB/Akt and Epac were all shown to establish complexes with neuronal A-kinase anchoring protein150 (AKAP150). Interestingly, activation of Epac increased phosphorylation of PKB/Akt complexed to AKAP150. From experiments using PKA-binding deficient AKAP150 and peptides disrupting PKA anchoring to AKAPs, we conclude that AKAP150 acts as a key regulator in the two cAMP pathways to control PKB/Akt phosphorylation. 相似文献
98.
Nitrogen (N) and water additions in the shortgrass steppe change the dominance of plant functional types (PFT) that are characterized by different photosynthetic pathways and phenologies. We aimed to examine monthly patterns of plant N and microbial N storage during the growing season, and to assess whether N fertilization last applied 30 years ago alters the timing and magnitude of N storage. We measured plant biomass and N, and microbial biomass N monthly during the growing season. We found differences in temporal patterns of plant and microbial N storage in the control plots, with microbial storage higher than plant storage in July, and the opposite trend in September. Unlike the control plots, the plots fertilized 30 years ago exhibited overlapping peaks of N storage in plants and microbes in August. Seasonal trends indicated that rainfall was an important control over plant and microbial activity at the beginning of the growing season, and that temperature limited these activities at the end of the growing season. PFT affected the amount of microbial N, which was in general higher under C3 grasses than other PFTs, independent of fertilization. Historical resource additions increased plant biomass and N, but had little effect on microbial N. These results highlight the complexity of the microbial response. Changes in climate that influence precipitation timing will affect the temporal pattern for microbial biomass N, while management practices resulting in altered plant community composition will influence the magnitude of microbial biomass N. 相似文献
99.
Induction of Hsp22 (HspB8) by estrogen and the metalloestrogen cadmium in estrogen receptor-positive breast cancer cells 下载免费PDF全文
Estrogen (E2) plays a critical role in the etiology and progression of human breast cancer. The estrogenic response is complex and not completely understood, including in terms of the involved responsive genes. Here we show that Hsp22 (synonyms: HspB8, E2lG1, H11), a member of the small heat shock protein (sHSP) superfamily, was induced by E2 in estrogen receptor-positive MCF-7 breast cancer cells, resulting in an elevated Hsp22 protein level, whereas it was not induced in estrogen receptor-negative MDA-MB-231 cells. This induction was prevented by the pure anti-estrogen ICI182780 (faslodex, fulvestrant), whereas tamoxifen, a substance with mixed estrogenic and antiestrogenic properties, had no major inhibitory effect on this induction, nor did it induce Hsp22 on its own. Cadmium (Cd) is an environmental pollutant with estrogenic properties (metalloestrogen) that has been implicated in breast cancer. Treatment of MCF-7 cells with Cd also resulted in induction of Hsp22, and this induction was also inhibited by ICI182780. In live MCF-7 cells, Hsp22 interacted at the level of dimers with Hsp27, a related sHSP, as was shown by quantitative fluorescence resonance energy transfer measurements. In cytosolic extracts of MCF-7 cells, most of the E2- and Cd-induced Hsp22 was incorporated into high-molecular mass complexes. In part, Hsp22 and Hsp27 were components of distinct populations of these complexes. Finally, candidate elements in the Hsp22 promoter were identified by sequence analysis that could account for the induction of Hsp22 by E2 and Cd. Taken together, Hsp22 induction represents a new aspect of the estrogenic response with potential significance for the biology of estrogen receptor-positive breast cancer cells. 相似文献
100.
Darío Cruz Juan Pablo Suárez Ingrid Kottke Meike Piepenbring Franz Oberwinkler 《Mycological Progress》2011,10(2):229-238
The genus Tulasnella comprises important orchid mycobionts. Molecular phylogenetic studies on nrITS-5.8S sequences of Tulasnella species previously isolated from mycorrhizas of epiphytic orchids from a tropical Andean forest showed genomic variability
among clones which was difficult to interpret as intra- or interspecific variations or to correlate with described Tulasnella species. To improve this situation, we collected basidiomata of Tulasnella in an Andean forest, studied part of the sequences of fungal ribosomal genes and correlated molecular data with the morphology
of the specimens. Within five basidiomata displaying slight morphological variability, we found inter-specimen nrITS1-5.8S-ITS2
variability corresponding to proportional differences of less than 1% except for one clone with 5.1% divergence. Results indicate
that the slightly variable basidiomata should be considered as one species, which is morphologically tentatively assigned
to the Tulasnella pruinosa complex. However, comparison of nrITS1-5.8S-ITS2 sequences, including sequences of T. pruinosa from other origins, indicate that Tulasnella sp. is only distantly related to the T. pruinosa specimens included in the analyses. Sequences of all morphologically similar and taxonomically well-identified species are
required to decide whether the basidiomata analyzed in the present study represent a new species. The new sequences are rather
similar to sequences obtained previously from mycorrhizae of epiphytic orchids of the same area indicating mycorrhizal potential
of this fungus. 相似文献