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   10324篇
  免费   1033篇
  国内免费   785篇
  2023年   143篇
  2022年   153篇
  2021年   545篇
  2020年   405篇
  2019年   457篇
  2018年   437篇
  2017年   318篇
  2016年   450篇
  2015年   651篇
  2014年   815篇
  2013年   795篇
  2012年   985篇
  2011年   833篇
  2010年   564篇
  2009年   461篇
  2008年   499篇
  2007年   529篇
  2006年   430篇
  2005年   359篇
  2004年   325篇
  2003年   257篇
  2002年   218篇
  2001年   185篇
  2000年   163篇
  1999年   161篇
  1998年   74篇
  1997年   76篇
  1996年   77篇
  1995年   56篇
  1994年   70篇
  1993年   56篇
  1992年   87篇
  1991年   66篇
  1990年   53篇
  1989年   58篇
  1988年   44篇
  1987年   43篇
  1986年   35篇
  1985年   40篇
  1984年   15篇
  1983年   20篇
  1981年   6篇
  1980年   10篇
  1979年   18篇
  1978年   10篇
  1976年   9篇
  1975年   6篇
  1974年   8篇
  1970年   11篇
  1968年   9篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
2.
3.
4.
The trophic structure of benthic communities in the Sea of Okhotsk and Bering Sea was analyzed based on the results of macrobenthic survey catches conducted in the Far Eastern seas in the 2000s. The production of trophic levels and entire communities was determined. It was shown that production of benthic communities is still at a high level and has almost not changed since the 1980s. The arrangement of the communities of some shelf areas by productivity characteristics was made.  相似文献   
5.
Weilan Ye 《The EMBO journal》2014,33(8):786-787
Since metastatic lesions of solid tumors are the major cause of mortality in cancer patients, understanding the molecular mechanisms of metastasis is of paramount importance. Although extensive knowledge has been accumulated regarding the early steps in metastasis—starting with the departure of cancer cells from their primary sites, to their transit through the hematogenous and/or lymphatic systems, and ending with their entrance into the parenchyma of distant organs—it is difficult if not impossible to translate such knowledge into medicine due to the challenge of identifying patients with only primary tumors but otherwise pristine organs. In other words, autopsy studies indicate that a large proportion of patients already harbor dormant, undetectable micrometastases at the time of cancer diagnosis (Hensel et al, 2013 ). Accordingly, stopping tumor cell dissemination is too late for these patients. Therefore, understanding the survival and outgrowth of micrometastases may hold greater promise to combat metastatic disease.  相似文献   
6.
Yang  Su-Rong  Sun  Huan-Xin  Hu  Zhen-Zhen  Wang  Si-Heng  Sun  Hui  Xue  Yin-Jia  Ye  Chen-Bo 《Sleep and biological rhythms》2017,15(1):57-65
Sleep and Biological Rhythms - Chronic sleep deprivation (SD) is an overwhelming problem in young students. Firstly, we investigated whether different levels of pre-training SD had effects on...  相似文献   
7.
8.
Herein, we describe a case study into the population dynamics of in vitro selection, using RNA-cleaving DNAzymes as a model system. We sought to understand how the composition of the population can change over time in response to different levels of selection pressure, and how well these changes are correlated with selection of the target phenotype. The model population is composed of 857 DNAzyme clones representing 215 discrete sequence classes, which had previously been identified from two parallel selection experiments, conducted under an increasingly stringent, or permissive and constant selection time pressure. In this report, we determined the principal phenotypic properties (i.e. kobs, maximum cleavage yield and PCR efficiency) from a sample of 58 clones representing 46 different major and minor sequence classes from various rounds of each selection experiment. Interestingly, a positive correlation between the catalytic rate constant and the corresponding frequency and temporal position of a given DNAzyme was not consistently observed; however, the strength of the correlation was qualitatively higher under conditions of more stringent selection time pressure. These results suggest that the selective sampling paradigm on which in vitro selection is based, may underestimate the true functional capacity of any given random-sequence library.  相似文献   
9.
10.
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