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   1028826篇
  免费   107230篇
  国内免费   417篇
  1136473篇
  2018年   9755篇
  2017年   9247篇
  2016年   13203篇
  2015年   17125篇
  2014年   20316篇
  2013年   29279篇
  2012年   32874篇
  2011年   33593篇
  2010年   22922篇
  2009年   21157篇
  2008年   30003篇
  2007年   31290篇
  2006年   29261篇
  2005年   28091篇
  2004年   27622篇
  2003年   26751篇
  2002年   26230篇
  2001年   45869篇
  2000年   45683篇
  1999年   36442篇
  1998年   13096篇
  1997年   13295篇
  1996年   12714篇
  1995年   11741篇
  1994年   11434篇
  1993年   11321篇
  1992年   30039篇
  1991年   29365篇
  1990年   28601篇
  1989年   27761篇
  1988年   25613篇
  1987年   24322篇
  1986年   22675篇
  1985年   22525篇
  1984年   18581篇
  1983年   16170篇
  1982年   12266篇
  1981年   11090篇
  1980年   10303篇
  1979年   17503篇
  1978年   13661篇
  1977年   12321篇
  1976年   11651篇
  1975年   13107篇
  1974年   13972篇
  1973年   13743篇
  1972年   12621篇
  1971年   11133篇
  1970年   9820篇
  1969年   9580篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose.  相似文献   
993.
994.
995.
996.
The seminal receptacle or spermatheca of Portunus sanguinolentus consists of two parts--an anterior glandular and a posterior chitinous part. The chitinous part continues as the oviduct, which opens on the sternite of the sixth thoracic segment. Significant morphological and histological differences were observed between the spermatheca, as well as the oviduct, of mated and unmated crabs. In mated crabs the spermatheca is much more bulging, owing to receipt of a copious supply of seminal products, and its cells are hyperactive. Further stages of ovarian development were observed as indicators of sequential changes in the spermatheca. The secretory cells gradually disintegrate by way of holocrine secretion; this results in cellular stratification and the formation of distinct furrows in the chitinous posterior part.  相似文献   
997.
998.
Prairie voles, Microtus ochrogaster, were infected with Eimeria ochrogasteri and exposed to 2 environmental temperatures, 5 and 22 C. Dry weights of the small and large intestines increased by 33% and 19%, respectively, in infected animals. Infected animals also exhibited a 14% decrease in cecal length compared to uninfected animals. The interaction between temperature and infection affected the length of the small intestine. Infected animals maintained at 5 C had longer small intestines than both infected animals housed at 22 C, and uninfected animals at 22 or 5 C. Furthermore, the dry weight of the small intestine was affected by a 3-way interaction (infection, temperature, and sex). Temperature affected stomach and liver dry weights, as well as lengths of the small intestine and cecum. Stomach and liver dry weights, as well as small intestine lengths, were greater in those animals held at 5 C, whereas cecum lengths decreased. Prepatency, patency, and total oocyst production were not affected by temperature; however, infected animals held at 5 C exhibited diarrhea during the patent period.  相似文献   
999.
The cytotoxic and radiosensitizing effects of hyperthermia was shown on Ehrlich ascites tumor cells heated in vitro. The effect of hyperthermia resulted in the formation of local lesions in membranes of dying cells.  相似文献   
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