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   309451篇
  免费   33435篇
  国内免费   259篇
  2018年   2670篇
  2016年   3742篇
  2015年   5308篇
  2014年   6034篇
  2013年   8968篇
  2012年   9796篇
  2011年   10120篇
  2010年   6640篇
  2009年   6153篇
  2008年   9107篇
  2007年   9307篇
  2006年   8845篇
  2005年   8620篇
  2004年   8472篇
  2003年   8259篇
  2002年   7961篇
  2001年   12180篇
  2000年   12079篇
  1999年   9722篇
  1998年   3857篇
  1997年   3960篇
  1996年   3870篇
  1995年   3405篇
  1994年   3422篇
  1993年   3418篇
  1992年   8175篇
  1991年   8115篇
  1990年   7794篇
  1989年   7723篇
  1988年   7120篇
  1987年   6861篇
  1986年   6257篇
  1985年   6514篇
  1984年   5539篇
  1983年   4653篇
  1982年   3752篇
  1981年   3553篇
  1980年   3356篇
  1979年   5220篇
  1978年   4076篇
  1977年   4008篇
  1976年   3695篇
  1975年   3977篇
  1974年   4417篇
  1973年   4290篇
  1972年   3789篇
  1971年   3546篇
  1970年   3234篇
  1969年   3121篇
  1968年   2870篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The influence of interlok, biotop and remantadine on the functional activity of monocytes was determined with the use of the NBT test permitting the quantitative evaluation of this characteristic. In this study interlok was found to give promising results in the treatment of acute viral hepatitis, due both to its antiviral action and to the stimulation of the functional activity of monocytes. biotop proved to render a sharply pronounced stimulating effect on the functional activity of monocytes, thus enhancing antiviral resistance. Remantadine suppressed the functional activity of monocytes and increased their lesion by the virus, thus creating favorable conditions for virus persistence in monocytes.  相似文献   
992.
Two hybridomas secreting mouse cytotoxic monoclonal antibodies to in vivo and in vitro activated human T-lymphocyte and neutrophil surface membrane antigenic determinants have been produced. One of these monoclonal antibodies (Ta/H-2) appeared to be also specifically reactive to blast cells in the majority of non-T-non-B and T acute lymphoblastic leukemia patients.  相似文献   
993.
The Orlando Easterly Wetland (OEW), located near Christmas, Florida, USA, is among the longer-lived treatment wetlands in the United States. It was established in the late 1980s to reduce nitrogen and phosphorus concentrations from tertiary treated wastewater bound for the St. Johns River. A goal of 0.07 mg/l total phosphorus concentration has been set by the regulating agency (St. Johns River Water Management District). In order to understand and define the operating conditions for which this target could be met, a systematic study of historic phosphorus uptake was performed using a traditional first-order model. Phosphorus uptake performance is shown to correlate well with hydraulic performance for two parallel upstream cells. The first-order model is enhanced with predictive capabilities that acknowledge the correlation between the phosphorus uptake rate constant and the hydraulic loading rate observed in the system. Inherent limitations with the first-order modeling approach are addressed and uncertainty in model performance is used to bound predictions.  相似文献   
994.
The new, fluorescent Ca2+ indicator, fura-2, promises to expand our understanding of the role of subcellular changes in Ca2+ underlying cell function. During an investigation of the role of Ca2+ in the polarization response of human polymorphonuclear leukocytes to formyl-methionyl-leucyl-phenylalanine, we found that fura-2 trapped by cells incubated with the acetoxy-methyl ester of fura-2, F2-AM, yielded measurements of Ca2+ that were depressed at rest and during the response to formyl-methionyl-leucyl-phenylalanine. Fura-2, trapped by the cells, exhibited a spectrum in the presence of saturating Ca2+ that differed from that of fura-2 free acid. We have shown that the cellular fluorescence can be spectrally decomposed into two components: one with Ca2+ sensitivity identical to fully deesterified fura-2, and another which is Ca2+-insensitive. The Ca2+-insensitive component appears to be more fluorescent than F2-AM as well as spectrally different from F2-AM. The insensitive form probably results from incomplete deesterification of F2-AM by the cells. In order to accurately measure Ca2+ in polymorphonuclear leukocytes, it is imperative to check for the presence of Ca2+-insensitive fluorescence. The contribution of Ca2+-insensitive fura-2 fluorescence can be assessed routinely from spectral data obtained by calibration of intracellular fura-2 with known [Ca2+] using ionomycin. The end-of-experiment calibration step not only ensures accurate [Ca2+] measurements in polymorphonuclear leukocytes and in other cell types that display Ca2+-insensitive, contaminating fluorescence but also yields the spectral characteristics of the insensitive species.  相似文献   
995.
996.
997.
The movement and polarity of zeatin, a highly active, endogenous cytokinin, through petioles and roots were tested in the classical experimental arrangement using excised 5-mm sections. Zeatin in the receiver cylinders of agar was measured by soybean callus bioassay and by liquid scintillation counting of 14C that had been added in the donor cylinders as [8-14C] zeatin. Both methods agreed in showing movement, but there was no polarity in Coleus #5 petioles. The amounts moved were about one-tenth of the GA-3 movement through petioles of the third pair of leaves of the same clone. Movement of 14C-zeatin through Pisum roots was similarly statistically significant but non-polar; the amounts moved were similar to those previously observed for polar GA-3 movement through Zea roots.  相似文献   
998.
999.
1000.
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