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   167690篇
  免费   6787篇
  国内免费   919篇
  175396篇
  2022年   486篇
  2021年   942篇
  2020年   567篇
  2019年   721篇
  2018年   12558篇
  2017年   11345篇
  2016年   8757篇
  2015年   2961篇
  2014年   2996篇
  2013年   4022篇
  2012年   8716篇
  2011年   17268篇
  2010年   14840篇
  2009年   10876篇
  2008年   13693篇
  2007年   15322篇
  2006年   4359篇
  2005年   4568篇
  2004年   5107篇
  2003年   4753篇
  2002年   4533篇
  2001年   1116篇
  2000年   761篇
  1999年   911篇
  1998年   1194篇
  1997年   875篇
  1996年   794篇
  1995年   759篇
  1994年   744篇
  1993年   713篇
  1992年   642篇
  1991年   637篇
  1990年   585篇
  1989年   621篇
  1988年   545篇
  1987年   522篇
  1986年   458篇
  1985年   592篇
  1984年   750篇
  1983年   655篇
  1982年   761篇
  1981年   795篇
  1980年   721篇
  1979年   499篇
  1978年   557篇
  1977年   527篇
  1976年   525篇
  1974年   498篇
  1972年   516篇
  1971年   537篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
We report a new mutation in the sterol 27-hydroxylase (CYP 27) gene in a Dutch family with cerebrotendinous xanthomatosis: a G→A transition in the splice donor site in intron 4. This mutation leads to skipping of exon 4, resulting in a loss of 66 amino acids in the CYP 27 enzyme molecule. Received: 15 March 1997 / Accepted: 26 March 1997  相似文献   
103.
Systems biology is an approach to explain the behaviour of a system in relation to its individual components. Synthetic biology uses key hierarchical and modular concepts of systems biology to engineer novel biological systems. In my opinion the next step in biology is to use molecule-to-phenotype data using these approaches and integrate them in the form a periodic table. A periodic table in biology would provide chassis to classify, systematize and compare diversity of component properties vis-a-vis system behaviour. Using periodic table it could be possible to compute higher-level interactions from component properties. This paper examines the concept of building a bio-periodic table using protein fold as the fundamental unit.  相似文献   
104.
Ferruh Aşçi 《Biologia》2009,64(6):1146-1149
In this study, the structural characteristics, unique features, various organ measurements of males and females of the water mite Atractides (Atractides) turcicus sp. n. from Turkey are described. In addition, the study compares their characteristics with related species.  相似文献   
105.
Abstract Burkholderia cepacia has emerged as an important multiresistant pathogen in cystic fibrosis (CF), associated in 20% of colonised patients with a rapid and fatal decline in lung function. Although knowledge of B. cepacia epidemiology has improved, the mechanisms involved in pathogenesis remain obscure. In this study, B. cepacia lipopolysaccharide (LPS) was assessed for endotoxic potential and the capacity to induce tumour necrosis factor (TNF). LPS preparations from clinical and environmental isolates of B. cepacia and from the closely related species Burkholderia gladioli exhibited a higher endotoxic activity and more pronounced cytokine response in vitro compared to preparations from the major CF pathogen Pseudomonas aeruginosa . This study may help to explain the vicious host immune response observed during pulmonary exacerbations in CF patients colonised by B. cepacia and lead to therapeutic advances in clinical management.  相似文献   
106.
107.
108.
109.
110.
A laboratory calibration study was undertaken with juvenile Sepia officinalis (80-85 g initial wet weight) to investigate the effects of different food rations and different starving intervals on RNA/dry weight (DW) ratios and RNA/DNA ratios in cephalopod mantle muscle at two different temperatures. The digestive gland index was also used as an additional indicator of recent growth. High food rations and low temperature went along with high RNA/DW ratios and high RNA/DNA ratios. Starving resulted in a linear decline in growth performance and a concomitant decrease in RNA/DW and RNA/DNA ratio, with RNA/DNA ratios representing the growth data better. RNA/DNA ratios decreased faster at higher temperatures. A fluorimetric assay for nucleic acid analysis was optimized for cephalopod mantle tissues and yielded reproducible RNA/DNA ratios with a relative variance below 10%. Thus, it may be possible to use this estimator of recently encountered feeding regime for the evaluation of mortality rates of early teuthid paralarvae to eventually support stock management. Also, log relative digestive gland weight showed a strong relationship with starving time, but, surprisingly, not with temperature. Data from the two temperatures analyzed could be combined to form a common regression line of relative digestive gland index with starving time. This indicator for recent growth might be especially suitable for large specimens with a well-developed digestive gland.  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