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   28903篇
  免费   3666篇
  国内免费   29篇
  2016年   247篇
  2015年   315篇
  2014年   399篇
  2013年   667篇
  2012年   636篇
  2011年   687篇
  2010年   484篇
  2009年   403篇
  2008年   588篇
  2007年   644篇
  2006年   612篇
  2005年   614篇
  2004年   620篇
  2003年   634篇
  2002年   640篇
  2001年   1847篇
  2000年   1828篇
  1999年   1433篇
  1998年   461篇
  1997年   465篇
  1996年   474篇
  1995年   422篇
  1994年   425篇
  1993年   419篇
  1992年   1068篇
  1991年   1080篇
  1990年   1058篇
  1989年   1025篇
  1988年   955篇
  1987年   896篇
  1986年   767篇
  1985年   746篇
  1984年   586篇
  1983年   506篇
  1982年   367篇
  1981年   341篇
  1980年   331篇
  1979年   561篇
  1978年   444篇
  1977年   412篇
  1976年   336篇
  1975年   455篇
  1974年   468篇
  1973年   414篇
  1972年   393篇
  1971年   310篇
  1970年   258篇
  1969年   240篇
  1968年   225篇
  1967年   205篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
Plasma melatonin levels in adult river lampreys Lampetra fluviatilis , sampled during their upstream migration showed a pronounced diel profile, with high levels during the night and lower levels during the day, showing that a cyclostome, in common with other vertebrates, exhibits such a diel plasma profile.  相似文献   
85.
86.
87.
88.
U B Olsen 《Prostaglandins》1978,15(4):645-649
Isolated rabbit kidneys were perfused with 37 degrees C Krebs-Henseleit solution aerated with 95% O2 + 5% CO2. Perfusion rate was varied from 1 to 10 ml/min. This was accompanied by parallel changes of perfusion pressure, prostaglandin excretion and release of radioactivity from kidneys with 14C-arachidonic acid incorporated into the tissue lipid pool. It is suggested that enhancement of perfusion rate raises the intrarenal pressure which increases renal prostaglandin release due to increased substrate availability.  相似文献   
89.
Autovaccination of rats with chronic pyelonephritis carried out approximately two months after the onset of infection does not result in an improved histological picture in the infected but can prevent destructive processes in the controlateral kidney. Cyclophosphamide administered in three doses of 30 mg/kg simultaneously with autovaccination slightly modulates the immune response to the infectious strain. The temporal relationship between immunization and cyclophosphamide administration determines the mode of action of cyclophosphamide. In the present experiment, the concept of Miller has not proved to be applicable. Cyclophosphamide administration causes a distinct increase in inflammatory processes in the kidney. Should an enhancement phenomenon be involved in the bacterial infection of the kidney, of which we have found no proof, cyclophosphamide therapy as it was used in the present study would not result in its removal and thus in improved elimination of the infectious organism. Additional experiments are required to determine whether animals subjected to autovaccination are protected against a new episode of urinary tract infection.  相似文献   
90.
In three adult macaques the retrograde degeneration of cell bodies in the motor cortex was investigated 6 months after unilateral pyramidal tract section. Large and small Betz cells of the fifth layer were identified microscopically and counted. The analysis of the data reveals that after pyramidotomy, (1) contrary to our expectations from the extent of the pyramidal lesions, a surprising percentage of undegenerated Betz cells remains in the contralateral motor cortex, (2) a greater percentage of small rather than large cell survives, and (3) the greatest loss of cells is in the foot region, the smallest in the face region. The results are discussed in relation to the role of pyramidal axon collaterals in the survival of cell bodies, and the distinction between pyramidal cells and pyramidal tract cells.  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