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   109489篇
  免费   5988篇
  国内免费   376篇
林业   4523篇
农学   3261篇
基础科学   746篇
  13019篇
综合类   19938篇
农作物   4350篇
水产渔业   4928篇
畜牧兽医   57191篇
园艺   1237篇
植物保护   6660篇
  2019年   1098篇
  2018年   1703篇
  2017年   1845篇
  2016年   1652篇
  2015年   1394篇
  2014年   1813篇
  2013年   4171篇
  2012年   3134篇
  2011年   3765篇
  2010年   2466篇
  2009年   2574篇
  2008年   3765篇
  2007年   3403篇
  2006年   3247篇
  2005年   2958篇
  2004年   2875篇
  2003年   2911篇
  2002年   2633篇
  2001年   3327篇
  2000年   3367篇
  1999年   2554篇
  1998年   1059篇
  1997年   1049篇
  1996年   996篇
  1995年   1138篇
  1993年   971篇
  1992年   2072篇
  1991年   2386篇
  1990年   2209篇
  1989年   2220篇
  1988年   1995篇
  1987年   2044篇
  1986年   2124篇
  1985年   2020篇
  1984年   1574篇
  1983年   1397篇
  1979年   1629篇
  1978年   1266篇
  1977年   1062篇
  1976年   979篇
  1975年   1107篇
  1974年   1406篇
  1973年   1423篇
  1972年   1408篇
  1971年   1269篇
  1970年   1296篇
  1969年   1231篇
  1968年   1115篇
  1967年   1118篇
  1966年   1012篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
Sevoflurane and desflurane are volatile inhaled anesthetics that are currently being investigated as possible improvements for the anesthetic management of human patients. Information to date suggests these agents have several advantages over existing clinical agents. For example, the blood/gas partition coefficient for both agents is lower than that of other halogenated anesthetics. Consistent with this physical characteristic is a more rapid induction of and emergence from anesthesia. Both cause a dose-related depression of cardiopulmonary function, which is comparable to isoflurane. Results of studies to date favor desflurane over sevoflurane because it is less soluble in blood, is stable in soda lime, is biodegraded the least of any volatile anesthetic, and is not toxic.  相似文献   
114.
115.
116.
Application of new procedures in the sphere of the control of sexual functions requires an extension of present knowledge of postparturient endocrinium or endogenic factors comprised in postparturient physiology of sexual activity. According to recent data, oxytocin, besides its uterotonic and luteolytic activity, acts as an ovarian factor in the local intrafollicular regulation of stereidogenesis and as a modulator of uterine secretion of prostaglandines. Based on present knowledge of oxytocin effects, this study was aimed at investigation of the influence of repeated carbetocin (Depotocin inj. Spofa) administration on the dynamics of changes in thyroxine (T4), triiodothyronine (T3), 17 beta-estradiol (E2), progesterone (P4) concentrations and their mutual correlations from the 36th hour till the 51st day after parturition. Simultaneous study of a possible delayed influence of applied carbetocin on conception of ewes after oestrus evocation on day 51 after lambing was carried out. Nineteen ewes of the Slovak Merino breed, lambed in the first decade of February, were assigned to the experimental (n = 9) and to the control group (n = 10). Experimental ewes were subjected to repeated postparturient carbetocin treatment at the dose 0.07 mg per animal. The first dose was applied i. m. in 24 hours, and the second in 72 hours after parturition. On day 51 oestrus was induced in nine ewes of each group by combined treatment with chlorsuperlutin (Agelin, vaginal pessaries, Spofa) and PMSG (500 I.U./animal). On the day of PMSG application ewes were housed together with rams for the period of the next six days. Samples of blood were taken 24 hours before parturition (-1st day), up to 36 h after parturition and on days 4, 7, 14, 17, 21, 25, 34, 42 and 51 after parturition. Concentrations of T4, T3, E2 and P4 were determined by commercial kits RIA-test-T4; RIA-test-T3; RIA-test-ESTRA and RIA-test-PROG (URVJT Kosice). Animal of the control group showed variations of T4 concentrations (Tab. I, Fig. 1) at the level of original values (59.4 +/- 9.69 nmol.l-1) up to the 21st day with the exception of temporary drop on day 4 and rise on day 7, insignificant compared to the -1st day. T4 concentrations of the control group displayed an intermittent increasing trend with the statistically insignificant peak after 36 h and on day 17, compared to the -1st day. After the 21st day controls revealed a sustained moderate increase while the experimental ewes displayed a decline of its concentrations until the 51st day.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
117.
118.
119.
120.
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