全文获取类型
收费全文 | 7856篇 |
免费 | 653篇 |
国内免费 | 1篇 |
专业分类
8510篇 |
出版年
2023年 | 33篇 |
2022年 | 87篇 |
2021年 | 175篇 |
2020年 | 77篇 |
2019年 | 116篇 |
2018年 | 132篇 |
2017年 | 114篇 |
2016年 | 245篇 |
2015年 | 375篇 |
2014年 | 444篇 |
2013年 | 514篇 |
2012年 | 669篇 |
2011年 | 652篇 |
2010年 | 449篇 |
2009年 | 434篇 |
2008年 | 531篇 |
2007年 | 523篇 |
2006年 | 466篇 |
2005年 | 458篇 |
2004年 | 433篇 |
2003年 | 412篇 |
2002年 | 365篇 |
2001年 | 67篇 |
2000年 | 46篇 |
1999年 | 64篇 |
1998年 | 80篇 |
1997年 | 58篇 |
1996年 | 50篇 |
1995年 | 40篇 |
1994年 | 49篇 |
1993年 | 52篇 |
1992年 | 31篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 19篇 |
1982年 | 8篇 |
1981年 | 15篇 |
1980年 | 6篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有8510条查询结果,搜索用时 15 毫秒
91.
92.
The uptake of bacteria and picoplankton sized fluorescentlylabelled beads was measured off the west coast of the SouthIsland of New Zealand in winter. Phytoflagellates and heterotrophicflagellates showed similar grazing rates on 0.49 µm beads,with mean clearance rates of 1.1 and 1.8 nl ind.1 h1,respectively. Clearance rates for 1.09 µm beads were 0.9nl ind.1 h1 for heterotrophic flagellates and0.5 nl ind.1 h1 for phytoflagellates. Non-loricateciliates had clearance rates of 1.5 µl ind.1 h1for the picoplankton sized particles. The heterotrophic flagellatesshowed no significant difference between clearance rates of0.49 and 1.09 µm particles. Phytoflagellates, however,showed an apparent preference for the smaller particles. Themeasurement of significant grazing by phytoflagellate populationsin the marine environment is important and indicates that weneed to reassess our concepts of food web structure. 相似文献
93.
Anthony Ricciardi Tim M. Blackburn James T. Carlton Jaimie T.A. Dick Philip E. Hulme Josephine C. Iacarella Jonathan M. Jeschke Andrew M. Liebhold Julie L. Lockwood Hugh J. MacIsaac Petr Pyšek David M. Richardson Gregory M. Ruiz Daniel Simberloff William J. Sutherland David A. Wardle David C. Aldridge 《Trends in ecology & evolution》2017,32(6):464-474
94.
95.
Foxl2 gene and the development of the ovary: a story about goat, mouse, fish and woman 总被引:2,自引:0,他引:2
Baron D Batista F Chaffaux S Cocquet J Cotinot C Cribiu E De Baere E De Baeree E Guiguen Y Jaubert F Pailhoux E Pannetier M Vaiman D Vigier B Veitia R Fellous M 《Reproduction, nutrition, development》2005,45(3):377-382
In this review, we describe recent results concerning the genetics of sex determination in mammals. Particularly, we developed the study of the FOXL2 gene and its implication in genetic anomalies in goats (PIS mutation) and humans (BPES). We present the expression of FOXL2 in the ovaries of different species. 相似文献
96.
Bernice Wright Trevor Gibson Jeremy Spencer Julie A. Lovegrove Jonathan M. Gibbins 《PloS one》2010,5(3)
Background
Flavonoid metabolites remain in blood for periods of time potentially long enough to allow interactions with cellular components of this tissue. It is well-established that flavonoids are metabolised within the intestine and liver into methylated, sulphated and glucuronidated counterparts, which inhibit platelet function.Methodology/Principal Findings
We demonstrate evidence suggesting platelets which contain metabolic enzymes, as an alternative location for flavonoid metabolism. Quercetin and a plasma metabolite of this compound, 4′-O-methyl quercetin (tamarixetin) were shown to gain access to the cytosolic compartment of platelets, using confocal microscopy. High performance liquid chromatography (HPLC) and mass spectrometry (MS) showed that quercetin was transformed into a compound with a mass identical to tamarixetin, suggesting that the flavonoid was methylated by catechol-O-methyl transferase (COMT) within platelets.Conclusions/Significance
Platelets potentially mediate a third phase of flavonoid metabolism, which may impact on the regulation of the function of these cells by metabolites of these dietary compounds. 相似文献97.
Kyle J. Nakamura Johannes S. Gach Laura Jones Katherine Semrau Jan Walter Frederic Bibollet-Ruche Julie M. Decker Laura Heath William D. Decker Moses Sinkala Chipepo Kankasa Donald Thea James Mullins Louise Kuhn Michael B. Zwick Grace M. Aldrovandi 《PloS one》2010,5(3)
Human antibody 4E10 targets the highly conserved membrane-proximal external region (MPER) of the HIV-1 transmembrane glycoprotein, gp41, and has extraordinarily broad neutralizing activity. It is considered by many to be a prototype for vaccine development. In this study, we describe four subjects infected with viruses carrying rare MPER polymorphisms associated with resistance to 4E10 neutralization. In one case resistant virus carrying a W680G substitution was transmitted from mother to infant. We used site-directed mutagenesis to demonstrate that the W680G substitution is necessary for conferring the 4E10-resistant phenotype, but that it is not sufficient to transfer the phenotype to a 4E10-sensitive Env. Our third subject carried Envs with a W680R substitution causing variable resistance to 4E10, indicating that residues outside the MPER are required to confer the phenotype. A fourth subject possessed a F673L substitution previously associated with 4E10 resistance. For all three subjects with W680 polymorphisms, we observed additional residues in the MPER that co-varied with position 680 and preserved charged distributions across this region. Our data provide important caveats for vaccine development targeting the MPER. Naturally occurring Env variants described in our study also represent unique tools for probing the structure-function of HIV-1 envelope. 相似文献
98.
Liu WM Li R Sun JZ Wang J Tsai J Wen W Kohlmann A Williams PM 《Journal of theoretical biology》2006,243(2):273-278
An ideal expression algorithm should be able to tell truly different expression levels with small false positive errors and be robust to assay changes. We propose two algorithms. PQN is the non-central trimmed mean of perfect match intensities with quantile normalization. DQN is the non-central trimmed mean of differences between perfect match and mismatch intensities with quantile normalization. The quantiles for normalization can be either empirical or theoretical. When array types and/or assay change in a study, the normalization to common quantiles at the probe set level is essential. We compared DQN, PQN, RMA, GCRMA, DCHIP, PLIER and MAS5 for the Affymetrix Latin square data and our data of two sets of experiments using the same bone marrow but different types of microarrays and different assay. We found the computation for AUC of ROC at affycomp.biostat.jhsph.edu can be improved. 相似文献
99.
100.
Cell cycle lengths vary widely among different cells within an animal, yet mechanisms of cell cycle length regulation are poorly understood. In the Caenorhabditis elegans embryo, the first cell division produces two cells with different cell cycle lengths, which are dependent on the conserved partitioning-defective (PAR) polarity proteins. We show that two key cell cycle regulators, the Polo-like kinase PLK-1 and the cyclin-dependent kinase phosphatase CDC-25.1, are asymmetrically distributed in early embryos. PLK-1 shows anterior cytoplasmic enrichment and CDC-25.1 shows PLK-1-dependent enrichment in the anterior nucleus. Both proteins are required for normal mitotic progression. Furthermore, these asymmetries are controlled by PAR proteins and the muscle excess (MEX) proteins MEX-5/MEX-6, and the latter is linked to protein degradation. Our results support a model whereby the PAR and MEX-5/MEX-6 proteins asymmetrically control PLK-1 levels, which asymmetrically regulates CDC-25.1 to promote differences in cell cycle lengths. We suggest that control of Plk1 and Cdc25 may be relevant to regulation of cell cycle length in other developmental contexts. 相似文献