全文获取类型
收费全文 | 38997篇 |
免费 | 2989篇 |
国内免费 | 2908篇 |
专业分类
44894篇 |
出版年
2024年 | 99篇 |
2023年 | 516篇 |
2022年 | 1180篇 |
2021年 | 2159篇 |
2020年 | 1359篇 |
2019年 | 1718篇 |
2018年 | 1726篇 |
2017年 | 1177篇 |
2016年 | 1642篇 |
2015年 | 2401篇 |
2014年 | 2830篇 |
2013年 | 3072篇 |
2012年 | 3580篇 |
2011年 | 3165篇 |
2010年 | 1987篇 |
2009年 | 1617篇 |
2008年 | 1968篇 |
2007年 | 1720篇 |
2006年 | 1586篇 |
2005年 | 1285篇 |
2004年 | 1052篇 |
2003年 | 909篇 |
2002年 | 758篇 |
2001年 | 664篇 |
2000年 | 588篇 |
1999年 | 628篇 |
1998年 | 351篇 |
1997年 | 364篇 |
1996年 | 344篇 |
1995年 | 316篇 |
1994年 | 332篇 |
1993年 | 263篇 |
1992年 | 311篇 |
1991年 | 242篇 |
1990年 | 213篇 |
1989年 | 189篇 |
1988年 | 127篇 |
1987年 | 101篇 |
1986年 | 92篇 |
1985年 | 86篇 |
1984年 | 59篇 |
1983年 | 53篇 |
1982年 | 34篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1976年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Wu S Guilford WJ Chou YL Griedel BD Liang A Sakata S Shaw KJ Trinh L Xu W Zhao Z Morrissey MM 《Bioorganic & medicinal chemistry letters》2002,12(9):1307-1310
A novel potent and selective aminophenol scaffold for fXa inhibitors was developed from a previously reported benzimidazole-based naphthylamidine template. The aminophenol template is more synthetically accessible than the benzimidazole template, which simplified the introduction of carboxylic acid groups. Substitution of a propenyl-para-hydroxy-benzamidine group on the aminophenol template produced selective, sub-nanomolar fXa inhibitors. The potency of the inhibitors is partially explained with the aid of a trypsin complex crystal structure. 相似文献
993.
994.
The aim of this study was to investigate the treatment efficiency of passive vertical-flow wetland filters containing different macrophytes (Phragmites and/or Typha) and granular media with different adsorption capacities. Gravel, sand, granular activated carbon, charcoal and Filtralite (light expanded clay) were used as filter media. Different concentrations of lead and copper sulfate were added to polluted urban stream inflow water to simulate pretreated mine wastewater. The relationships between growth media, microbial and plant communities as well as the reduction of predominantly lead, copper and five-day biochemical oxygen demand (BOD5) were investigated. An analysis of variance showed that concentration reductions (mg l(-1)) of lead, copper and BOD5 were significantly similar for the six experimental wetlands. Microbial diversity was low due to metal pollution and similar for all filters. There appears to be no additional benefit in using adsorption media and macrophytes to enhance biomass performance during the first 10 months of operation. 相似文献
995.
Yee-Peng Chan Min Lu Somnath Dutta Lianying Yan Jennifer Barr Michael Flora Yan-Ru Feng Kai Xu Dimitar B. Nikolov Lin-Fa Wang Georgios Skiniotis Christopher C. Broder 《Journal of virology》2012,86(21):11457-11471
The henipaviruses, Hendra virus (HeV) and Nipah virus (NiV), are paramyxoviruses discovered in the mid- to late 1990s that possess a broad host tropism and are known to cause severe and often fatal disease in both humans and animals. HeV and NiV infect cells by a pH-independent membrane fusion mechanism facilitated by their attachment (G) and fusion (F) glycoproteins. Here, several soluble forms of henipavirus F (sF) were engineered and characterized. Recombinant sF was produced by deleting the transmembrane (TM) and cytoplasmic tail (CT) domains and appending a glycosylphosphatidylinositol (GPI) anchor signal sequence followed by GPI-phospholipase D digestion, appending a trimeric coiled-coil (GCNt) domain (sFGCNt), or deleting the TM, CT, and fusion peptide domain. These sF glycoproteins were produced as F0 precursors, and all were apparent stable trimers recognized by NiV-specific antisera. Surprisingly, however, only the GCNt-appended constructs (sFGCNt) could elicit cross-reactive henipavirus-neutralizing antibody in mice. In addition, sFGCNt constructs could be triggered in vitro by protease cleavage and heat to transition from an apparent prefusion to postfusion conformation, transitioning through an intermediate that could be captured by a peptide corresponding to the C-terminal heptad repeat domain of F. The pre- and postfusion structures of sFGCNt and non-GCNt-appended sF could be revealed by electron microscopy and were distinguishable by F-specific monoclonal antibodies. These data suggest that only certain sF constructs could serve as potential subunit vaccine immunogens against henipaviruses and also establish important tools for further structural, functional, and diagnostic studies on these important emerging viruses. 相似文献
996.
997.
鼻息肉与变态反应之间有密切联系。本文拟报道康克通—A用于鼻息肉摘除术前、后以延迟与防止息肉复发的临疗效观察。 相似文献
998.
继对芝麻矮化坏死病源研究之后,又对普遍发生的芝麻黄花叶病害分离物(YMo—I)进行了系统鉴定。该分离物普遍存在于各芝麻主产区,普通年份发病率为1~5%。YMo—I侵染芝麻引起叶片褪绿及黄绿相间花叶。摩擦接种能够侵染4科12种(品种)植物。局部侵染苋色藜、昆诺藜;系统侵染大豆、花生、望江南、克氏烟等。该病毒能够由桃蚜、花生蚜、大豆蚜以非持久性方式进行传播。ELISA检测其病株种子带毒率为0.5%,但尚未发现种生病苗。病毒在组织汁液中存活期3天;钝化温度55~60℃,稀释限点4×10~(-3)。提纯病毒为弯曲线状粒体,大小约为13×730nm。并有极易凝聚的趋势。病组织中诱导大量典型PVY第一亚组的风轮形和卷筒状细胞质内含体和少数多边形结晶核内含体。血清学上该病毒与花生条纹病毒(PStV)、西瓜花叶病毒—2(MMV—2)密切相关,与花生斑驳病毒、大豆花叶病毒弱相关;与芜菁花叶病毒不相关。但它不侵染WMV—2的寄主—黄瓜,并且该病害田间的发生流行与芝麻、花生的间作方式以及PStV在花生田间的流行密切相关。根据上述结果,YMo—I分离株被鉴定为花生条纹病毒的一芝麻分离株。 相似文献
999.
1000.
应用XTT法检测白细胞介素—Ⅱ的生物学活性 总被引:3,自引:0,他引:3
应用XTT比色法检测IL-2的生物学活性并与MTT法和^3H掺入法进行比较,结果XTT法较上述方法简便易行,结果稳定,重复性好。 相似文献