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   275857篇
  免费   17931篇
  国内免费   3563篇
  2021年   3334篇
  2020年   2252篇
  2019年   2868篇
  2018年   9365篇
  2017年   8767篇
  2016年   7937篇
  2015年   4787篇
  2014年   5994篇
  2013年   7466篇
  2012年   10612篇
  2011年   15246篇
  2010年   11316篇
  2009年   10624篇
  2008年   12502篇
  2007年   14051篇
  2006年   6762篇
  2005年   6889篇
  2004年   6663篇
  2003年   6780篇
  2002年   6481篇
  2001年   9333篇
  2000年   9490篇
  1999年   6900篇
  1998年   2362篇
  1997年   2358篇
  1996年   2116篇
  1995年   1978篇
  1992年   5476篇
  1991年   5629篇
  1990年   5334篇
  1989年   5307篇
  1988年   4857篇
  1987年   4654篇
  1986年   4211篇
  1985年   4349篇
  1984年   3509篇
  1983年   3018篇
  1982年   2011篇
  1979年   3265篇
  1978年   2597篇
  1977年   2321篇
  1976年   2124篇
  1975年   2593篇
  1974年   2920篇
  1973年   2858篇
  1972年   3280篇
  1971年   2944篇
  1970年   2152篇
  1969年   2040篇
  1968年   1915篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
951.
952.
953.
Chloragogen cells, subserving ion exchange and electron accepting functions, were studied in Tubifex tubifex after insecticide treatment. Chloragogen cells were strongly influenced by in vivo carbofuran poisoning. The first alterations in the chloragogen cells became activated, both the formation and release of the chloragosomes reached a high rate. The released chloragosomes were phagocytosed by the amoebocytes. At an advanced stage of the toxication a heavy loading of the apical cytoplasm of chloragogen cells with lipid droplets, finally degenerative changes both in the chloragogen cells and amoebocytes were observed. Possible mechanisms of the carbofuran toxication and of the protective function of chloragogen cells in T. tubifex are discussed.  相似文献   
954.
955.
The effect of inert helium and argon gases on the tissue respiration has been studied on lymphocyte suspensions of white rats. It is shown that normoxic helium-oxygen mixture induces almost a two-fold increase of the O2 uptake by lymphocytes as compared with the control (air). No deviations in the value of the studied parameter are revealed in case of replacement of nitrogen from air by argon. Significance of the membrane structure in realization of effects of inert gases is under discussion.  相似文献   
956.
A total of 626 patients undergoing a prostaglandin-induced abortion, the majority in the second trimester, have been analysed for complications occurring during inpatient treatment. Of the last 155 consecutive patients 143 were critically assessed six to eight weeks after abortion for morbidity occurring during their early recovery period.Blood loss of 250 ml or more occurred in 68 patients, pyrexia in 34, pelvic infection in three, and readmission in 14 of the 626 patients studied, and a transfusion was required in eight.Bleeding after abortion stopped within six weeks in all 143 of the 155 consecutive patients assessed but three required readmission for uterine curettage. Menstruation was re-established within six weeks of abortion in 106 patients.The incidence of operative morbidity was similar to that reported for first trimester abortion and better than that in most reported series of second trimester abortions.  相似文献   
957.
Mild micrococcal nuclease treatment of rat and mouse nuclei and fractionation were based on the method of Tata and Baker. Three chromatin fractions, S, P1, P2, were separated, and for each of these fractions the sensitivity to the DNase 1 action was determined. The relative content in these fractions of non-transcribed DNA sequences was established by hydridization with a mouse satellite DNA, and the relative content of transcribed DNA sequences--by hydridization with DNA synthesised on the total poly (A) mRNA. None of the fractions displayed the properties characteristic of active chromatin.  相似文献   
958.
Natural heparin complexes proved to activate the anticoagulation system. The obtained experimental data convincingly confirm that glutamic acid alone, and particularly in a complex with heparin, has a considerable preventive potential and efficiently protects experimental animals with induced diabetes mellitus.  相似文献   
959.
960.
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