全文获取类型
收费全文 | 35229篇 |
免费 | 76篇 |
国内免费 | 120篇 |
专业分类
系统科学 | 343篇 |
丛书文集 | 721篇 |
教育与普及 | 88篇 |
理论与方法论 | 116篇 |
现状及发展 | 15358篇 |
研究方法 | 1410篇 |
综合类 | 16787篇 |
自然研究 | 602篇 |
出版年
2013年 | 201篇 |
2012年 | 500篇 |
2011年 | 1100篇 |
2010年 | 192篇 |
2009年 | 167篇 |
2008年 | 556篇 |
2007年 | 643篇 |
2006年 | 678篇 |
2005年 | 668篇 |
2004年 | 640篇 |
2003年 | 630篇 |
2002年 | 560篇 |
2001年 | 1068篇 |
2000年 | 1035篇 |
1999年 | 655篇 |
1992年 | 637篇 |
1991年 | 544篇 |
1990年 | 580篇 |
1989年 | 503篇 |
1988年 | 520篇 |
1987年 | 560篇 |
1986年 | 539篇 |
1985年 | 692篇 |
1984年 | 559篇 |
1983年 | 452篇 |
1982年 | 373篇 |
1981年 | 394篇 |
1980年 | 522篇 |
1979年 | 1123篇 |
1978年 | 918篇 |
1977年 | 883篇 |
1976年 | 704篇 |
1975年 | 782篇 |
1974年 | 1051篇 |
1973年 | 933篇 |
1972年 | 913篇 |
1971年 | 1114篇 |
1970年 | 1467篇 |
1969年 | 1098篇 |
1968年 | 917篇 |
1967年 | 1018篇 |
1966年 | 916篇 |
1965年 | 650篇 |
1959年 | 386篇 |
1958年 | 612篇 |
1957年 | 466篇 |
1956年 | 419篇 |
1955年 | 351篇 |
1954年 | 382篇 |
1948年 | 282篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The rough endoplasmic reticulum membranes of mammalian cells contain specific ribosome-binding sites. A purification to apparent homogeneity of a negatively charged protein (ERp180) of relative molecular mass 180,000 (180 K) was reported which was proposed to function as a rough endoplasmic reticulum ribosome receptor. We report here that ribosome-binding site activity quantitatively solubilized from rough endoplasmic reticulum membranes does not cofractionate with ERp180. By contrast, ribosome-binding site activity fractionates as a much smaller, positively charged protein. 相似文献
72.
Genotoxic effects of dithane M-45 were studied on the bone marrow cells of male albino mice (Lacca strain) in vivo. Different doses (30 mg, 40 mg and 300 mg/kg b.wt) of dithane M-45 were injected intraperitoneally and their effects were investigated after time intervals of 1, 2, 5 and 10 days. The chromosomal aberrations observed in the bone marrow cells of male mice after treatment with dithane M-45 were fragments, rings, dicentric chromosomes, terminal chromatid deletions, chromatid gaps and breaks. In addition to these chromosomal aberrations, physiological effects such as uneven stretching of chromatin material, end-to-end chromosomal associations, exchange configurations, clumping, stickiness and centromeric associations were also observed. 相似文献
73.
74.
LANE RE 《Advancement of science》1948,5(18):96-118
75.
76.
77.
78.
R. Auerbach 《Cellular and molecular life sciences : CMLS》1948,4(12):473-474
Summary The preceding empirical relation was found between the surface tension of liquids, the specific weight of liquids, and the velocity of sound:=6.3 · 10–4
3/2. In place of the vèocity of sound can be used, with suitable changes in the equation, the compressibility or, in the case of solid substances, the elasticity of the material in question. The range of validity of this relation is so large that it is possible by means of it to calculate the surface tension of solid substances and of gases. 相似文献
79.
1 Results In addition to single wall and multiwall carbon nanotubes[1], several structures,which are more or less related to fullerenes,including carbon nanohorns[2a], carbon nanospheres[2b] and onion like carbon structures[2c] have been reported.A new simple straight forward method to access some of these structures is the solid-state pyrolysis of different organometallic complexes in a sealed vessel,which led so far to carbon nanotubes[3a,b], carbon nanocables[3c] and onions[3d]. 相似文献
80.