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   42793篇
  免费   3839篇
  国内免费   21篇
  46653篇
  2022年   311篇
  2021年   651篇
  2020年   366篇
  2019年   508篇
  2018年   621篇
  2017年   569篇
  2016年   908篇
  2015年   1496篇
  2014年   1679篇
  2013年   2156篇
  2012年   2666篇
  2011年   2672篇
  2010年   1673篇
  2009年   1578篇
  2008年   2282篇
  2007年   2370篇
  2006年   2240篇
  2005年   2238篇
  2004年   2138篇
  2003年   2084篇
  2002年   1963篇
  2001年   654篇
  2000年   462篇
  1999年   551篇
  1998年   548篇
  1997年   407篇
  1996年   389篇
  1995年   318篇
  1994年   354篇
  1993年   329篇
  1992年   330篇
  1991年   311篇
  1990年   300篇
  1989年   278篇
  1988年   289篇
  1987年   264篇
  1986年   244篇
  1985年   333篇
  1984年   409篇
  1983年   330篇
  1982年   378篇
  1981年   445篇
  1980年   421篇
  1979年   263篇
  1978年   271篇
  1977年   285篇
  1976年   269篇
  1975年   187篇
  1974年   245篇
  1973年   206篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
Desulfurization of model and diesel oils by resting cells of Gordona sp.   总被引:2,自引:0,他引:2  
The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g–1 cell–1 h–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g–1 cell–1 h–1) than the model oil (0.12 mg sulfur g–1 cell–1 h–1).  相似文献   
2.
In vivo EMG biofeedback was found to be an effective pedagogical tool for removing unwanted left-hand tension in nine violin and viola players. Improvement occurred rapidly and persisted throughout a 5-month follow-up period. Further studies will be necessary to assess the effect of biofeedback independent of placebo effects. The brevity of the method and the magnitude of improvement warrant further investigation.  相似文献   
3.
The ability to metabolically label proteins with 35S-methionine is critical for the analysis of protein synthesis and turnover. Despite the importance of this approach, however, efficient labeling of proteins in vivo is often limited by a low number of available methionine residues, or by deleterious side-effects associated with protein overexpression. To overcome these limitations, we have created a methionine-rich variant of the widely used HA tag, called HAM, for use with ectopically expressed proteins. Here we describe the development of a series of vectors, and corresponding antisera, for the expression and detection of HAM-tagged proteins in mammalian cells. We show that the HAM tag dramatically improves the sensitivity of 35S-methionine labeling, and permits the analysis of Myc oncoprotein turnover even when HAM-tagged Myc is expressed at levels comparable to that of the endogenous protein. Because of the improved sensitivity provided by the HAM tag, the vectors and antisera described here should be useful for the analysis of protein synthesis and destruction at physiological levels of protein expression.  相似文献   
4.
5.
6.
7.
8.
9.
The effects of mammalian gonadotropins, methyltestosterone and partially purified salmon gonadotropin on spermiation and oocyte maturation were studied in adult grey mullet. Methyltestosterone was a potent spermiating agent in both prespawning and spawning trials. The most effective dose was 5 mg/100 g body weight. Human chorionic gonadotropin (HCG) was moderately effective at a dose rate of 20 IU/100 g body weight. Both hormones blocked resorption of milt in captive animals. The HCG, FSH/LH combination, Synahorin+mullet pituitary homogenate, and partially purified salmon gonadotropin were equally effective, at the doses used, in inducing oocyte maturation and preventing onset of atrophy before completion of vitellogenesis. Atrophy occurred in all experimental fish at mean oocyte diameter of 750 μ. The significance of this finding is discussed. (Oceanic Institute Contribution No. 98).  相似文献   
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