首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3127篇
  免费   317篇
  国内免费   6篇
  2023年   12篇
  2022年   31篇
  2021年   52篇
  2020年   29篇
  2019年   36篇
  2018年   51篇
  2017年   44篇
  2016年   87篇
  2015年   154篇
  2014年   155篇
  2013年   173篇
  2012年   237篇
  2011年   232篇
  2010年   151篇
  2009年   126篇
  2008年   168篇
  2007年   172篇
  2006年   165篇
  2005年   140篇
  2004年   161篇
  2003年   111篇
  2002年   108篇
  2001年   72篇
  2000年   60篇
  1999年   90篇
  1998年   39篇
  1997年   36篇
  1996年   27篇
  1995年   22篇
  1994年   25篇
  1993年   20篇
  1992年   52篇
  1991年   40篇
  1990年   41篇
  1989年   30篇
  1988年   38篇
  1987年   29篇
  1986年   29篇
  1985年   19篇
  1984年   16篇
  1983年   13篇
  1982年   12篇
  1980年   13篇
  1979年   13篇
  1977年   15篇
  1976年   12篇
  1975年   10篇
  1974年   10篇
  1973年   11篇
  1972年   10篇
排序方式: 共有3450条查询结果,搜索用时 328 毫秒
991.
992.
993.
Hydrosalpinx (HSP) has been shown to be detrimental to the outcome of assisted reproduction, but little is known of its pathology. This prospective study examined and detailed ultrastructural characterization of HSP of infertile women presenting for assisted reproductive treatments. Both light and electron microscopies were used to characterize HSP. Hematoxylin and eosin staining of HSP showed areas without epithelial cell lining or with abnormalities such as flattening of the epithelial layer and exfoliation of epithelial cells with occasional normal columnar epithelial lining. HSP muscle fibers were atrophic and occasionally replaced by fibrous tissues, or separated by areas of severe edema. Inflammatory cells could be found in hydrosalpinx fluid (HF) in the lumen in areas with flattened to no epithelial cells, without epithelial lining, as well as in dilated blood vessels and/or lymph vessels. Scanning electron microscopy of the epithelial surface revealed epithelial denudation-severe loss of both cilia and microvilli and stomata exuding globular bodies on eroded ampulla surfaces. Severe chronic inflammation and damage to the epithelial lining and musculature of Fallopian tubes and the presence of inflammatory cells provides an explanation for HF formation, and thus for the detrimental effects of HF on reproductive processes and IVF outcome.  相似文献   
994.
Novel cyclopentane analogues of fumagillol were synthesized and their endothelial cell proliferation inhibitory activities were evaluated. The cyclopentane-fumagillol derivatives were synthesized from (-)-2,3-O-isopropylidene-D-erythronolactone via stereoselective glycolate Claisen rearrangement and intramolecular ester enolate alkylation as key steps.  相似文献   
995.
A series of 2a-i were prepared from a lead compound, saucerneol B (1) for evaluating their acyl-CoA: cholesterol acyltransferase inhibitory activities. Compounds 2a-g exhibited the high specificity of hACAT-1 than hACAT-2, whereas 2h and 2i showed very weak inhibitory activities in both hACAT-1 and hACAT-2. Saucerneol B (1) exhibited strong cholesterol-lowering effect in high cholesterol-fed mice.  相似文献   
996.
A series of (E)-phenyl- and -heteroaryl-substituted O-benzoyl- (or acyl)oximes 3a-n were synthesized for evaluating their human lipoprotein-associated phospholiphase A2 (Lp-PLA2) inhibitory activities. The less lipophilic derivatives 3a-c showed the most potent in vitro inhibitory activity on human Lp-PLA2.  相似文献   
997.
Intellectual property rights are essential in today's technology-driven age. A strong intellectual property protection strategy is crucial in the bioinformatics and biochips technology spaces as monetary and temporal resources are tremendous in finding a blockbuster drug or gene therapy, as well as in deploying advanced biosensor and other medical systems. Current problems and intellectual property practice in the genomic space are presented and analyzed. Various strategy and solutions are proposed to guide bioinformatic and biochip companies in forming an aggressive strategy to protect one's intellectual property and competitive positioning.  相似文献   
998.
999.
Ho CL  Mou TY  Chiang PS  Weng CL  Chow NH 《BioTechniques》2005,38(2):267-273
We constructed a mini chamber system that was able to maintain cell culture on a microscope for long periods. It is a modified closed system with medium perfusion and CO2 circulation. The closed CO2 circulation and ample air inside the chamber distinguish it from other closed systems. Using different cell lines, the system was shown to be able to support long-term, time-lapse recording. After 229 hours of time-lapse recording, A2058 cells (a melanoma cell line) became overconfluent but still multiplied. Many CAD cells (a murine neuron-like cell line) still moved their cell bodies and kept their neurite-like processes after 28 days of recording. The entire healing process of a scratch-wounded 124 (a bladder cancer cell line) monolayer can be monitored. Such a modified closed system should find many applications in developmental biology, cell biology, and cancer biology where long-term, time-lapse recording is required or when the health of cells is important.  相似文献   
1000.
Tobias CM  Chow EK 《Planta》2005,220(5):678-688
Analysis of lignification in rice has been facilitated by the availability of the recently completed rice genome sequence, and rice will serve as an important model for understanding the relationship of grass lignin composition to cell wall digestibility. Cinnamyl-alcohol dehydrogenase (CAD) is an enzyme important in lignin biosynthesis. The rice genome contains 12 distinct genes present at nine different loci that encode products with significant similarity to CAD. The rice gene family is diverse with respect to other angiosperm and gymnosperm CAD genes isolated to date and includes one member (OsCAD6) that contains a peroxisomal targeting signal and is substantially diverged relative to other family members. Four closely related family members (OsCAD8A–D) are present at the same locus and represent the product of a localized gene duplication and inversion. Promoter-reporter gene fusions to OsCAD2, an orthologue of the CAD gene present at the bm1 (brown midrib 1) locus of maize, reveal that in rice expression is associated with vascular tissue in aerial parts of the plant and is correlated with the onset of lignification. In root tissue, expression is primarily in the cortical parenchyma adjacent to the exodermis and in vascular tissue.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号