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   17575篇
  免费   39篇
  国内免费   42篇
系统科学   100篇
丛书文集   264篇
教育与普及   33篇
理论与方法论   79篇
现状及发展   8093篇
研究方法   813篇
综合类   8034篇
自然研究   240篇
  2013年   87篇
  2012年   234篇
  2011年   500篇
  2010年   85篇
  2008年   281篇
  2007年   307篇
  2006年   340篇
  2005年   342篇
  2004年   442篇
  2003年   306篇
  2002年   322篇
  2001年   481篇
  2000年   445篇
  1999年   336篇
  1992年   294篇
  1991年   223篇
  1990年   239篇
  1989年   237篇
  1988年   205篇
  1987年   235篇
  1986年   280篇
  1985年   341篇
  1984年   233篇
  1983年   234篇
  1982年   212篇
  1981年   218篇
  1980年   225篇
  1979年   564篇
  1978年   476篇
  1977年   439篇
  1976年   343篇
  1975年   406篇
  1974年   565篇
  1973年   453篇
  1972年   472篇
  1971年   553篇
  1970年   702篇
  1969年   542篇
  1968年   540篇
  1967年   536篇
  1966年   431篇
  1965年   371篇
  1964年   121篇
  1959年   193篇
  1958年   330篇
  1957年   247篇
  1956年   190篇
  1955年   192篇
  1954年   190篇
  1948年   127篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Summary Rats given aluminium hydroxide after cold-restraint stress but before the post-stress delay period, ulcerated significantly less severely and less frequently than rats given the drug before cold-restraint stress or those given water at either time period. Both aluminium hydroxide treated groups exhibited less ulceration than non-drug groups. These data suggest profound parasympathetic and hence, gastric acid, involvement in restraint delay-induced ulceration in rats.  相似文献   
102.
103.
Summary A needle type of colloid osmometer has been devised with special attachments which made it useable with 3-l samples. It has been used in oncometry of fresh water teleosts to give the following results: 5.1±1.0 mm Hg for goldfish, 5.2±0.71 mm Hg for carp, and 14.3±0.75 mm Hg for eel.This study was supported in part by Research Grant 387036 from the Ministry of Education of Japan.invited to National Institute of Physiological Sciences, Okazaki, Japan.  相似文献   
104.
105.
106.
Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner.  相似文献   
107.
Summary Thymidylate synthetase (methylenetetrahydrofolate: 2-deoxyuridine-5-monophosphate C-methyltransferase; EC 2.1.1.45) from neonatal mouse liver has been purified 714-fold by affinity chromatography on aminohexylsepharose bound 10-methyl-5,8-dideazafolate.Supported by grant CA22754, awarded by the National Cancer Institute, DHEW.  相似文献   
108.
Summary Several high molecular weight polyacetylenes have been isolated from the spongePetrosia ficiformis found in dark caves. These compounds are related to, but different from, the polyacetylenes isolated from the same sponge living in its usual habitat.This work is a part of the Progetto finalizzato per l'Oceanografia e i Fondi Marini, CNR, Roma.The authors thank Mr G. Scognamiglio for the HPLC work, Mr C. Di Pinto for the NMR spectra and Mr G. Villani for the collection of the sponge.  相似文献   
109.
Incorporation of 32P into adrenal mitochondrial phospholipids (PL) incrased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overacity. Since diabetics did not show increased 11 beta-hydroxylation. as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. The process is impaired in diabetics and prevents the stimulation of 11 beta-hydroxylation.  相似文献   
110.
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