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   18792篇
  免费   52篇
  国内免费   86篇
系统科学   296篇
丛书文集   458篇
教育与普及   39篇
理论与方法论   94篇
现状及发展   8636篇
研究方法   833篇
综合类   8385篇
自然研究   189篇
  2012年   255篇
  2011年   482篇
  2010年   116篇
  2009年   105篇
  2008年   310篇
  2007年   377篇
  2006年   343篇
  2005年   334篇
  2004年   321篇
  2003年   406篇
  2002年   379篇
  2001年   736篇
  2000年   686篇
  1999年   393篇
  1993年   93篇
  1992年   339篇
  1991年   257篇
  1990年   310篇
  1989年   282篇
  1988年   280篇
  1987年   294篇
  1986年   298篇
  1985年   355篇
  1984年   259篇
  1983年   228篇
  1982年   208篇
  1981年   249篇
  1980年   281篇
  1979年   595篇
  1978年   490篇
  1977年   492篇
  1976年   373篇
  1975年   399篇
  1974年   601篇
  1973年   477篇
  1972年   448篇
  1971年   546篇
  1970年   680篇
  1969年   600篇
  1968年   512篇
  1967年   550篇
  1966年   468篇
  1965年   347篇
  1959年   200篇
  1958年   301篇
  1957年   197篇
  1956年   175篇
  1955年   169篇
  1954年   163篇
  1948年   91篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Summary The D-galactose specific lectin fromViscum album L. reacts with serum proteins that contain the corresponding D-galactopyranosyl residues. By affinity chromatography of human serum on lectin-sepharose IgM, 2-macroglobulin, haptoglobin and -lipoprotein were quantitatively retained. Only parts of IgA, IgG and transferrin were retarded. The other serum proteins are unbounded as albumin, 1A– and 1C.  相似文献   
132.
Linear unintegrated DNA of Schmidt-Ruppin Rous sarcoma virus, subgroup D (SR-RSV-D), was digested with SmaI restriction endonuclease, analyzed by agarose gel electrophoresis, "blotted" by Southern's method and hybridized with a viral 32P cDNA. SmaI cleaves this DNA at five sites, two of which are localized at the ends of the provirus. Src and env genes seem not to be restrictied by SmaI cleavage.  相似文献   
133.
Summary Corpora allata fromOncopeltus fasciatus incubated in vitro in medium containing 10–5.35 M (1 g/ml) of precocene II lose their ability to secrete juvenile hormone when reimplanted into last instar larvae.Acknowledgments. We thank Mr K. Dorn, Mrs L. Dolezal, Mrs V. Nötzli-Graf, Mr K.H. Trautmann and Mr A. Schuler for technical help, Dr W. Vogel and Dr A. Dübendorfer for valuable discussions.  相似文献   
134.
135.
136.
Summary Cells from a murine fibrosarcoma (FSa) have been grown in vitro as multicell tumor spheroids (MTS). The growth rate of these MTS was determined. Follwing selected periods of growth, MTS were made into a single cell suspension and separated on linear density gradients of Renografin. While only 1 population of cells was separated from small spheroids (400 m diameter), at least 3 subpopulations of tumor cells were separated and isolated from large spheroids (800 m in diameter).This investigation was supported in part by grants numbered CA-18628 and CA-06294, awarded by the National Cancer Institute, DHEW.  相似文献   
137.
P Perry  H J Evans 《Nature》1975,258(5531):121-125
A staining technique that detects sister chromatid exchanges (SCEs) has been used to examine the response of chromosomes in cultured Chinese hamster cells to a wide variety of mutagens-carcinogens. The test gives a very sensitive and rapid method for detecting chromosome mutagenicity of chemical agents and provides a powerful new method for detecting environmental mutagens.  相似文献   
138.
New theory for receptor mechanism of carotid body chemoreceptors.   总被引:1,自引:0,他引:1  
M P Osborne  P J Butlar 《Nature》1975,254(5502):701-703
  相似文献   
139.
Summary Acute toxicity induced by DMN was partially prevented by previously administering methyl mercuric chloride (MMC), a chemical inhibitor of the drug metabolizing enzyme system (DMES). We have studied the early changes occurring during the course of DMN-intoxication, namely disaggregation of polysomal profiles and necrosis, evaluated morphologically and by the release of S-GPT.This work was supported by Consiglio Nazionale delle Ricerche, Roma, Italy.  相似文献   
140.
Summary The serum activities of aspartate aminotransferase, alanine aminotransferase, -hydroxybutyrate dehydrogenase and creatine phosphokinase have been measured in the African elephant. In general, the values were broadly comparable with those of man except that alanine aminotransferase was much lower and creatine phosphokinase higher. No variation due to age, sex, season or location was observed.  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