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   84942篇
  免费   2074篇
  国内免费   48篇
  2018年   980篇
  2017年   1144篇
  2016年   2885篇
  2015年   6195篇
  2014年   5825篇
  2013年   5621篇
  2012年   4802篇
  2011年   2057篇
  2010年   2118篇
  2009年   2074篇
  2008年   564篇
  2007年   517篇
  2006年   557篇
  2005年   6631篇
  2004年   5320篇
  2003年   3533篇
  2002年   1094篇
  2001年   1102篇
  2000年   373篇
  1999年   1519篇
  1998年   350篇
  1997年   181篇
  1992年   1945篇
  1991年   2028篇
  1990年   2081篇
  1989年   2014篇
  1988年   1962篇
  1987年   1824篇
  1986年   1630篇
  1985年   1662篇
  1984年   1103篇
  1983年   848篇
  1982年   480篇
  1981年   432篇
  1980年   387篇
  1979年   1085篇
  1978年   771篇
  1977年   634篇
  1976年   655篇
  1975年   889篇
  1974年   1001篇
  1973年   1012篇
  1972年   957篇
  1971年   933篇
  1970年   826篇
  1969年   838篇
  1968年   742篇
  1967年   758篇
  1966年   589篇
  1965年   439篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
262.
263.
264.
265.
In several geographic populations of the Arctic ground squirrel C. parryi, studies have been made on changes in oxygen consumption during decrease of the ambient temperature from 25 to 3-4 degrees, thermal preference, hemoglobin content of the blood and composition of the adipose tissue (both brown and white, subcutaneous and visceral). Significant shifts of these indices were found. In animals from various parts of the species area, different sensitivity to cooling was found, as indicated by determinations of oxygen consumption at different temperatures and the prefered temperature: different hemoglobin content of the blood was also found together with differences in the level of two unsaturated fatty acids - the oleic and linoleic ones. Comparison of these data with similar results obtained on various populations of the Siberian ground squirrel C. undulatus revealed obvious differences between these close species with respect to the indices studied.  相似文献   
266.
The effect of primycin, a guanidine-type antibiotic was studied on the electric properties and 42K+ uptake of the frog sartorius and semitendinosus muscle. Both in normal and choline chloride Ringer solution, primycin evoked a concentration and time dependent depolarization of the surface membrane of the muscle. This depolarization was significantly increased by Na ions. Primycin treatment was shown to evoke a dose-dependent decrease of the depolarization induced by 20 mM K+-Ringer. When the muscles were incubated in a Ringer solution containing choline chloride, during an incubation period of 30 min the uptake of 42K+ was decreased to 12% upon the exposure to 5 x 10(-6) mol primycin as compared to the control value. As the primycin-induced depolarization increased, the shape and amplitude of the action potentials elicited by square-wave electric impulses were altered and decreased, respectively. In sodium isaethionate Ringer 1--2 x 10(-6) M primycin induced a slow depolarization resulting in firing potentials. The results suggest that primycin depolarizes the surface membrane exclusively through the blockade of the resting K+ channels, the other phenomena being the results of this depolarizing effect.  相似文献   
267.
268.
The importance of protein phosphorylation at tyrosyl hydroxy groups in the control of cell proliferation has recently been established. For identification of tyrosine-phosphorylated proteins, monoclonal antibodies (Mabs) against artificial immunogens containing O-phosphotyrosine (pTyr) or tripeptide pTyr-Gly-Gly as haptens were generated; the haptens were coupled to carrier proteins (bovine serum albumin, human immunoglobulin, keyhole limpet hemocyanin). After immunization of mice with pTyr coupled to keyhole limpet hemocyanin, Mabs were generated which were highly specific for pTyr and did not cross-react with O-phosphoserine, O-phosphothreonine, tyrosine or nucleoside-5'-monophosphates. The Mabs specifically react with tyrosinephosphorylated proteins in the Rous sarcoma virus-transformed rat XC-cell.  相似文献   
269.
E Schr?der 《Acta anatomica》1978,100(4):478-489
The utero-ovarian vascularisation of the non-pregnant rat was investigated, described and morphometrically evaluated. The ovarian and uterine arteries anastomose together giving up a ramus ovaricus. The leaving of these vessels from their main trunks varies to each body side, just as their length and width. Several segmental arteries arise from each uterine artery to the corpus uteri also side-specifically. Coiled circular arteries are found. The uterine cervical vascularisation is described separately. Different regulating effects on the function of the vessels are discussed.  相似文献   
270.
Genetic variants of serum alkaline phosphatase were studied by the method of starch gel electrophoresis in the Z?otnicka Pstra breed of pigs. Two regions of alkaline phosphatase migration were observed. A single fraction in region I and four different phenotypes: AB, B, BC and BD in region II, were found. For AB, B and BC phenotypes the genetic control by three alleles AkpA, AkpB and AkpC is suggested. The observed segregation ratios in some cases deviated significantly from the expected ones.  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