全文获取类型
收费全文 | 27764篇 |
免费 | 140篇 |
国内免费 | 295篇 |
专业分类
系统科学 | 440篇 |
丛书文集 | 409篇 |
教育与普及 | 89篇 |
理论与方法论 | 90篇 |
现状及发展 | 11109篇 |
研究方法 | 1121篇 |
综合类 | 14304篇 |
自然研究 | 637篇 |
出版年
2013年 | 307篇 |
2012年 | 625篇 |
2011年 | 1242篇 |
2010年 | 425篇 |
2009年 | 401篇 |
2008年 | 683篇 |
2007年 | 806篇 |
2006年 | 804篇 |
2005年 | 721篇 |
2004年 | 548篇 |
2003年 | 470篇 |
2002年 | 513篇 |
2001年 | 824篇 |
2000年 | 852篇 |
1999年 | 595篇 |
1992年 | 470篇 |
1991年 | 402篇 |
1990年 | 423篇 |
1989年 | 386篇 |
1988年 | 376篇 |
1987年 | 406篇 |
1986年 | 372篇 |
1985年 | 460篇 |
1984年 | 430篇 |
1983年 | 303篇 |
1982年 | 321篇 |
1981年 | 313篇 |
1980年 | 342篇 |
1979年 | 804篇 |
1978年 | 648篇 |
1977年 | 590篇 |
1976年 | 521篇 |
1975年 | 557篇 |
1974年 | 682篇 |
1973年 | 572篇 |
1972年 | 570篇 |
1971年 | 685篇 |
1970年 | 814篇 |
1969年 | 640篇 |
1968年 | 682篇 |
1967年 | 695篇 |
1966年 | 612篇 |
1965年 | 462篇 |
1964年 | 200篇 |
1959年 | 238篇 |
1958年 | 387篇 |
1957年 | 272篇 |
1956年 | 220篇 |
1955年 | 231篇 |
1954年 | 204篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Summary Silver-staining has been used to identify the nucleolus organizer regions (NORs) in the bharal. These show homology with sheep, goat, cattle and aoudad. The association of the NORs on both telomeres of chromosome 3 results in a ring chromosome. 相似文献
102.
H. L. Weinberg 《Cellular and molecular life sciences : CMLS》1980,36(5):548-549
Summary The hemolymph volume ofHeliothis zea larvae was determined by the amaranth dye method and found to vary from 28 to 288 l. It averaged 30.6% of b.wt, a value comparable to that obtained with C14 inulin. Amaranth became evenly distributed in the hemocoele in 3–5 min. 相似文献
103.
J. Kędziora M. Soszyński G. Bartosz H. Witas W. Leyko 《Cellular and molecular life sciences : CMLS》1980,36(8):926-927
Summary A statistically significant decrease of prealbumin and statistically significant increases of alpha2-macroglobulin and IgA were found in blood plasma of patients with Down's syndrome using quantitative crossed immunoelectrophoresis.We are indebted to Prof. T.C. Bøg-Hansen, University of Copenhagen, for the helpful discussion of our results. 相似文献
104.
Summary In the sandal plant affected by spike disease, caused by mycoplasma-like organisms, the changes occurring in the 5-and 3-nucleotidase activities were studied and their possible significance discussed. 相似文献
105.
R. L. Tyson C. -j. Chang J. L. McLaughlin Y. Aynehchi J. M. Cassady 《Cellular and molecular life sciences : CMLS》1981,37(5):441-442
Summary A novel sesquiterpene lactone, 9--hydroxyparthenolide (1) was isolated from a chloroform extract ofAnvillea garcini that was collected in Iran. The structure of1 was assigned on the basis of high field NMR decoupling experiments and other spectroscopic evidence. This -methylene lactone has shown significant activity in both the 9KB cell culture and P388 mouse leukemia test systems.The authors acknowledge the support of contract No. N01-CM-97296 from the National Cancer Institute and the use of the Purdue University Biochemical Magnetic Resonance Laboratory (NIH grant No. RR01077). This is paper 16 in the series Potential Antitumor Agents. 相似文献
106.
107.
108.
For the identification of a peptidyl principle inducing sexual agglutination in the yeast, 2 supposed hexapeptides (1a, b) were synthesized by the conventional method. The 1a (H-Arg-Gly-Pro-Phe-Pro-Ile-OH) revealed complete identity with the natural peptide in TLC, MS and biological property on agglutination. The 1b showed the sexual agglutinability in the same degree as 1a, though distinct differences were observed in the chemical data. Both 1a and 1b had a strong bitter taste. 相似文献
109.
The ontogeny and localization of the gamma crystallins in Discoglossus pictus lens development has been determined. Using antibody specific for amphibian gamma crystallins in the immunofluorescence technique, it was found that gamma crystallins first appear in primary lens fibre cells in the lens rudiment, and continue to be restricted to the fibre area as lens development progresses. Thus the role of gamma crystallins as indicators of a differentiated state remains constant in amphibian evolution, having been demonstrated in the most archaic anuran superfamily, as well as in others more recently evolved. 相似文献
110.
Summary Pronase and -chymotrypsin digested the major glycoprotein in the human and mouse red cell membranes and in SDS gel electrophoresis the glycoprotein disappeared accompanied by the appearance of a new band of lower mol.wt. However in the membranes of sheep, rat and rabbit, no digestion was demonstrated. The effects of pronase on anion permeability were almost identical for human and animal erythrocytes. 相似文献