全文获取类型
收费全文 | 7093篇 |
免费 | 1095篇 |
国内免费 | 3742篇 |
出版年
2024年 | 103篇 |
2023年 | 264篇 |
2022年 | 369篇 |
2021年 | 416篇 |
2020年 | 410篇 |
2019年 | 440篇 |
2018年 | 280篇 |
2017年 | 294篇 |
2016年 | 294篇 |
2015年 | 425篇 |
2014年 | 620篇 |
2013年 | 528篇 |
2012年 | 736篇 |
2011年 | 663篇 |
2010年 | 577篇 |
2009年 | 579篇 |
2008年 | 626篇 |
2007年 | 630篇 |
2006年 | 545篇 |
2005年 | 475篇 |
2004年 | 365篇 |
2003年 | 309篇 |
2002年 | 251篇 |
2001年 | 264篇 |
2000年 | 254篇 |
1999年 | 177篇 |
1998年 | 91篇 |
1997年 | 75篇 |
1996年 | 42篇 |
1995年 | 54篇 |
1994年 | 36篇 |
1993年 | 33篇 |
1992年 | 41篇 |
1991年 | 48篇 |
1990年 | 41篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1986年 | 38篇 |
1985年 | 30篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1977年 | 20篇 |
1976年 | 14篇 |
1975年 | 15篇 |
1972年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
R. C. Griffiths S. W. McKechnie J. A. McKenzie 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,62(1):89-96
Summary Mother-offspring data for alcohol dehydrogenase genotypes of a vineyard cellar population of D. melanogaster are best explained by a model that allows 21% of females in the population to mate twice with an 83% level of sperm displacement. A population model with multiple mating and sperm displacement is examined theoretically. A formula for the effective population size is derived under this model. Multiple mating increases the effective population size relative to single mating. 相似文献
3.
Surface markers of a purified peritoneal eosinophil population from Mesocestoides corti-infected BALB/c male mice 总被引:2,自引:0,他引:2
P M Hogarth K M Cruise I F McKenzie G F Mitchell 《Journal of immunology (Baltimore, Md. : 1950)》1980,124(1):406-411
Eosinophils of approximately 95% purity were prepared from the peritoneal cavities of BALB/c male mice infected with larval cestode, Mesocestoides corti. The alloantigenic surface marker phenotype of this cell population was shown to be H-2+Ly4+Ly5+Lyt-1-,2-,3-Ly-6-,7-Ia-Thy-1-TL-. Two of four anti-Lyt-2 sera were positive when tested on purified eosinophils by using the Staphylococcus aureus protein A sheep erythrocyte rosetting method, but absorption studies indicated that this reaction was not due to anti-Lyt-2 antibodies. Eosinophils are therefore Lyt-2-, although some Lyt-2 sera contain additional eosinophil reactive antibodies. A proportion (20 to 40%) of the population of eosinophils was positive for the Fc receptor, but all were negative for the C3 receptor and for surface immunoglobulin. 相似文献
4.
5.
6.
Corinna Richter Ron L. Dy Rebecca E. McKenzie Bridget N.J. Watson Corinda Taylor James T. Chang Matthew B. McNeil Raymond H.J. Staals Peter C. Fineran 《Nucleic acids research》2014,42(13):8516-8526
Clustered regularly interspaced short palindromic repeats (CRISPR), in combination with CRISPR associated (cas) genes, constitute CRISPR-Cas bacterial adaptive immune systems. To generate immunity, these systems acquire short sequences of nucleic acids from foreign invaders and incorporate these into their CRISPR arrays as spacers. This adaptation process is the least characterized step in CRISPR-Cas immunity. Here, we used Pectobacterium atrosepticum to investigate adaptation in Type I-F CRISPR-Cas systems. Pre-existing spacers that matched plasmids stimulated hyperactive primed acquisition and resulted in the incorporation of up to nine new spacers across all three native CRISPR arrays. Endogenous expression of the cas genes was sufficient, yet required, for priming. The new spacers inhibited conjugation and transformation, and interference was enhanced with increasing numbers of new spacers. We analyzed ∼350 new spacers acquired in priming events and identified a 5′-protospacer-GG-3′ protospacer adjacent motif. In contrast to priming in Type I-E systems, new spacers matched either plasmid strand and a biased distribution, including clustering near the primed protospacer, suggested a bi-directional translocation model for the Cas1:Cas2–3 adaptation machinery. Taken together these results indicate priming adaptation occurs in different CRISPR-Cas systems, that it can be highly active in wild-type strains and that the underlying mechanisms vary. 相似文献
7.
急性脑梗死约占全部脑卒中的70%,病死率和致残率高,且极易复发。但目前针对急性脑梗死在时间窗内溶栓、抗凝等治疗手段不能从根本上切实有效地修复受损脑组织,且伴有出血等风险。寻找脑梗死形成发展的原因并予以治疗迫在眉睫。酸中毒是引起缺血性脑损伤的重要机制。大量实验研究表明,酸中毒能加重神经元的缺血性损伤,且其梗死面积与酸中毒的程度直接相关。但缺血产生的酸中毒如何引起神经元损伤的确切机制尚不明确。最近研究发现酸中毒能激活一种在中枢及周围神经中广泛存在的膜通道,即酸敏感离子通道,它对Ca2+通透,能引起细胞内Ca2+超载,同时能激活胞内酶引起细胞内蛋白质、脂类及核酸的降解,加重缺血后脑损伤。本文就酸敏感离子通道1a与脑梗死做一综述。 相似文献
8.
A new protein crosslinking agent, 2,3-dibromopropionyl-N-hydroxysuccinimide ester, has been synthesized and characterized. The potential use of this compound as a temperature-controllable heterobifunctional crosslinking agent has been investigated using model systems and its reactivity compared with that of chlorambucil-N-hydroxysuccinimide ester. The coupling of14C-labeled phenylethylamine to lysozyme has been used to illustrate the feasibility of the use of this crosslinking agent for the synthesis of immunotoxins. 相似文献
9.
Mauro S. Sandrin K. Erin Lovering George Tachas Peter R. Collins Ian F. C. McKenzie 《Immunogenetics》1987,25(5):279-283
Human DNA was transfected into mouse L cells and tk+ HuLy-m2+ (= CD7+) transfectants isolated after growth in hypoxanthine, aminopterin, thymidine medium and repeated cloning. After several cycles of transfection, > 90% of HuLy-m2+ L cells could be detected, by rosetting and by cytofluorography, which showed the transfectants to have a density of CD7 two to five times that found on peripheral blood lymphocytes. Despite this, the 37 kd CD7+ dimer could only be identified with difficulty using cell-surface radioiodination and sodium dodecyl sulfate-polyacrylamide gel electrophoresis techniques. An antiserum was produced (C3H anti-HuLy-m2+ L cells) which, after absorption, was shown to react with HuLy-m2 antigens present on human thymocytes and lymphocytes and on CD7+ transfected L cells.Abbreviations BSA
bovine serum albumin
- DME
Dulbecco's modified Eagle's medium
- EDTA
ethylenediamine-tetraacetate
- HAT
hypoxanthine, aminopterin, thymidine
- HSV
herpes simplex virus
- PBL
peripheral blood lymphocyte
- PBS
phosphate-buffered saline
- RFC
rosette-forming cell
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- tk
thymidine kinase 相似文献
10.
P. Mark Hogarth Margaret L. Hibbs Lisa Bonadonna Bernadette M. Scott Ewa Witort Geoffrey A. Pietersz Ian F. C. McKenzie 《Immunogenetics》1987,26(3):161-168
A cDNA clone encoding the mouse Ly-17+ Fc receptor for IgG, isolated from a myelomonocytic cell line, was sequenced and expression of mRNA and the functional FcR investigated. The receptor is a 301 amino acid transmembrane glycoprotein with two homologous extracellular domains that are also homologous to members of the Ig superfamily. The receptor has four sites of N-linked glycosylation and a long 94 amino acid cytoplasmic tail. Northern analysis, immune complex binding, and serological studies demonstrate that the receptor encoded by the cDNA clone binds mouse IgG1/2b and rabbit IgG complexes. 相似文献