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   682318篇
  免费   74229篇
  国内免费   310篇
  2016年   7644篇
  2015年   10263篇
  2014年   12145篇
  2013年   17990篇
  2012年   19617篇
  2011年   20229篇
  2010年   13728篇
  2009年   12464篇
  2008年   17922篇
  2007年   18898篇
  2006年   17728篇
  2005年   17017篇
  2004年   17135篇
  2003年   16687篇
  2002年   16381篇
  2001年   28392篇
  2000年   28419篇
  1999年   22896篇
  1998年   8295篇
  1997年   8610篇
  1996年   8171篇
  1995年   7856篇
  1994年   7701篇
  1993年   7597篇
  1992年   19993篇
  1991年   19435篇
  1990年   19395篇
  1989年   18936篇
  1988年   17815篇
  1987年   16863篇
  1986年   15611篇
  1985年   16105篇
  1984年   13305篇
  1983年   11610篇
  1982年   9018篇
  1981年   8050篇
  1980年   7621篇
  1979年   13075篇
  1978年   10066篇
  1977年   9461篇
  1976年   8925篇
  1975年   9686篇
  1974年   10589篇
  1973年   10540篇
  1972年   9721篇
  1971年   8978篇
  1970年   7661篇
  1969年   7609篇
  1968年   6951篇
  1967年   6007篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
983.
The role of cortisol as a factor controlling the deposition of glycogen in the pig fetus was examined by infusing either a low dose (1 mg/day) or a high dose (3 mg/day) of cortisol into chronically-catheterized hypophysectomized fetal pigs for five days beginning on day 100-104 of gestation. After infusion, liver glycogen was significantly higher (P less than 0.05) and lung glycogen significantly lower (P less than 0.05) than in uninfused hypophysectomized litter mates although concentrations were significantly different from intact litter mates (P less than 0.05). Although skeletal and cardiac muscle content increased after infusion this difference was not significant. Changes in tissue glycogen content were similar for both the low and high rates of infusion. These observations indicate that exogenous cortisol alone is able to stimulate liver glycogen deposition and reverse the effect of hypophysectomy. Although other factors may be necessary for maximal response this suggests that cortisol is an important stimulant for liver glycogen deposition in the fetal pig. The effect of cortisol on muscle glycogen was equivocal suggesting that other hormones may play a more important role in this tissue.  相似文献   
984.
Paracoenia fumosalis Cresson previously known only from the USA and Canada is recorded in the Palaearctic Region for the first time. The adults were collected near a thermal hydrosulfuric spring in the Geiser Valley in Kamchatka. A key to species of the genus Paracoenia occurring in Russia is given.  相似文献   
985.
986.
Fossil plants of the Chingandzha flora were studied from volcanogenic sediments of the Chingandzha and Rond formations on the northern coast of the Sea of Okhotsk. It was concluded that all platanaceous leaves earlier described in this flora as different taxa belong to one highly variable species, Pseudoprotophyllum cordatum Samyl. emend. Shczepetov et Golovneva.  相似文献   
987.
988.
989.
Abstract The parasitoid wasp Trichogramma dendrolimi Matsumura sets the number of progeny allocated to its insect egg hosts according to the duration of its initial transit walk across the host surface. Although cooling the wasp reduces its walking speed, reduced temperature does not affect progeny allocation. By locally heating and cooling the wasps, the initial transit can be thermally uncoupled from the subsequent oviposition. Using this technique we show that the timing of initial transit duration is temperature-dependent. These findings suggest that short interval timing by Trichogramma differs physiologically from the temperature compensated clocks that have been described for other insects.  相似文献   
990.
The combination of alpha interferon and vinblastine has been reported to yield a response rate of 30-40% in previously untreated patients with metastatic renal cell carcinoma. This combination was given to nine patients with advanced metastatic renal carcinoma after they failed or relapsed on alpha-interferon alone, to attempt to evaluate the role of vinblastine in this combination. Neither complete nor partial response was observed. Two patients had disease stabilization for two and seven months. Our preliminary results suggest that vinblastine did not add to the efficacy of interferon in this group of patients.  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