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   12904篇
  免费   715篇
  国内免费   2篇
  2022年   19篇
  2021年   116篇
  2020年   83篇
  2019年   114篇
  2018年   166篇
  2017年   154篇
  2016年   251篇
  2015年   404篇
  2014年   478篇
  2013年   970篇
  2012年   844篇
  2011年   866篇
  2010年   554篇
  2009年   519篇
  2008年   855篇
  2007年   903篇
  2006年   805篇
  2005年   843篇
  2004年   822篇
  2003年   762篇
  2002年   725篇
  2001年   136篇
  2000年   120篇
  1999年   178篇
  1998年   179篇
  1997年   118篇
  1996年   120篇
  1995年   107篇
  1994年   97篇
  1993年   99篇
  1992年   123篇
  1991年   88篇
  1990年   76篇
  1989年   91篇
  1988年   53篇
  1987年   68篇
  1986年   70篇
  1985年   53篇
  1984年   62篇
  1983年   50篇
  1982年   70篇
  1981年   58篇
  1980年   57篇
  1979年   26篇
  1978年   26篇
  1977年   32篇
  1976年   32篇
  1975年   35篇
  1974年   18篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
PacBio RS II is the first commercialized third-generation DNA sequencer able to sequence a single molecule DNA in real-time without amplification. PacBio RS II’s sequencing technology is novel and unique, enabling the direct observation of DNA synthesis by DNA polymerase. PacBio RS II confers four major advantages compared to other sequencing technologies: long read lengths, high consensus accuracy, a low degree of bias, and simultaneous capability of epigenetic characterization. These advantages surmount the obstacle of sequencing genomic regions such as high/low G+C, tandem repeat, and interspersed repeat regions. Moreover, PacBio RS II is ideal for whole genome sequencing, targeted sequencing, complex population analysis, RNA sequencing, and epigenetics characterization. With PacBio RS II, we have sequenced and analyzed the genomes of many species, from viruses to humans. Herein, we summarize and review some of our key genome sequencing projects, including full-length viral sequencing, complete bacterial genome and almost-complete plant genome assemblies, and long amplicon sequencing of a disease-associated gene region. We believe that PacBio RS II is not only an effective tool for use in the basic biological sciences but also in the medical/clinical setting.  相似文献   
3.
4.
Vascular endothelial cells (ECs) are continuously exposed to shear stress (SS) generated by blood flow. Such stress plays a key role in regulation of various aspects of EC function including cell proliferation and motility as well as changes in cell morphology. Vascular endothelial-protein-tyrosine phosphatase (VE-PTP) is an R3-subtype PTP that possesses multiple fibronectin type III-like domains in its extracellular region and is expressed specifically in ECs. The role of VE-PTP in EC responses to SS has remained unknown, however. Here we show that VE-PTP is diffusely localized in ECs maintained under static culture conditions, whereas it undergoes rapid accumulation at the downstream edge of the cells relative to the direction of flow in response to SS. This redistribution of VE-PTP triggered by SS was found to require its extracellular and transmembrane regions and was promoted by integrin engagement of extracellular matrix ligands. Inhibition of actin polymerization or of Cdc42, Rab5, or Arf6 activities attenuated the SS-induced redistribution of VE-PTP. VE-PTP also underwent endocytosis in the static and SS conditions. SS induced the polarized distribution of internalized VE-PTP. Such an effect was promoted by integrin engagement of fibronectin but prevented by inhibition of Cdc42 activity or of actin polymerization. In addition, depletion of VE-PTP by RNA interference in human umbilical vein ECs blocked cell elongation in the direction of flow induced by SS. Our results suggest that the polarized redistribution of VE-PTP in response to SS plays an important role in the regulation of EC function by blood flow.  相似文献   
5.
6.
7.
8.
9.
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3al) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis.  相似文献   
10.
Cytological observations were made on material from 35 collections taken from 21 populations representing 10 species and 2 genera. Haploid chromosome numbers observed in Nitella were 9, 12, 18, 18, 18, and 18 + 36. Those observed in Chara were 14, 28, 28, and 42. Several data indicate that Nitella transilis is an established polyploid of N. tenuissima. The evaluation of chromosome numbers in respect to hybridization, polyploidy, and sexuality in haplobiontic plants is discussed.  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