全文获取类型
收费全文 | 11619篇 |
免费 | 20篇 |
国内免费 | 41篇 |
专业分类
系统科学 | 49篇 |
丛书文集 | 205篇 |
教育与普及 | 41篇 |
理论与方法论 | 63篇 |
现状及发展 | 5230篇 |
研究方法 | 563篇 |
综合类 | 5322篇 |
自然研究 | 207篇 |
出版年
2013年 | 106篇 |
2012年 | 196篇 |
2011年 | 414篇 |
2010年 | 90篇 |
2008年 | 225篇 |
2007年 | 240篇 |
2006年 | 238篇 |
2005年 | 279篇 |
2004年 | 235篇 |
2003年 | 236篇 |
2002年 | 239篇 |
2001年 | 288篇 |
2000年 | 298篇 |
1999年 | 194篇 |
1992年 | 178篇 |
1991年 | 150篇 |
1990年 | 156篇 |
1989年 | 158篇 |
1988年 | 169篇 |
1987年 | 158篇 |
1986年 | 169篇 |
1985年 | 234篇 |
1984年 | 145篇 |
1983年 | 140篇 |
1982年 | 100篇 |
1981年 | 116篇 |
1980年 | 153篇 |
1979年 | 378篇 |
1978年 | 283篇 |
1977年 | 305篇 |
1976年 | 220篇 |
1975年 | 220篇 |
1974年 | 340篇 |
1973年 | 278篇 |
1972年 | 300篇 |
1971年 | 308篇 |
1970年 | 419篇 |
1969年 | 364篇 |
1968年 | 365篇 |
1967年 | 335篇 |
1966年 | 292篇 |
1965年 | 213篇 |
1964年 | 69篇 |
1959年 | 117篇 |
1958年 | 211篇 |
1957年 | 169篇 |
1956年 | 160篇 |
1955年 | 132篇 |
1954年 | 132篇 |
1948年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
Dasgupta (2015) has recently put forward a novel argument, which he calls the ‘curvature argument’, that aims to show that Galilean spacetime is not an ideal setting for our classical theory of motion. This paper examines the curvature argument and argues that it is not sound. The discussion yields a remark about the conditions under which a ‘symmetry argument’ demonstrates that a particular spacetime is a non-ideal setting for our theory of motion. 相似文献
2.
3.
F. Mulè 《Cellular and molecular life sciences : CMLS》1948,4(3):115-117
Summary A study was undertaken on the variations of the redox potential level produced by streptomycinin vitro andin vivo. We have been able to show that, owing to an oxidative effect, streptomycin produces an increase of the redox potential level. This oxidative effect varies in degree according to the condition of the patient.We also found that in the blood and in the spinal fluid of patients suffering from tubercular meningitis factors are present which inhibit the action of streptomycin.The results of our findings lead to the conclusion that the dose of streptomycin must be varied according to the condition of the patient if the constant level required for an efficient therapy is to be maintained in the blood and in the spinal fluid. 相似文献
4.
5.
F. Weygand A. Wacker V. Schmied-Kowarzik 《Cellular and molecular life sciences : CMLS》1948,4(11):427-428
Summary By condensing 2:4:5-triamino-6-hydroxy-pyrimidine with dihydroxyacetone (diacetate), diaminoacetone or acetone-1,3-di (p-formylaminobenzoic acid) not the expected 8- or 9-oxymethyl resp. -aminomethyl-pteridines but 8-or 9-methyl-pteridines were obtained. With p-tolyl-d-isoglucosamine not a tetrahydroxybutyl-pteridine but a trihydroxybutyl-pteridine was formed. For an explanation of these results it is supposed that from the dihydro-pteridines formed at first by intramolecular splitting off of H2O or R·NH2 aromatization takes place. 相似文献
6.
Summary Intravenous or subcutaneous administration of pyribenzamine and other antihistaminics is able to decrease, and to delay the appearance of chemosis produced by mustard oils in the eye of the rabbit. Simultaneously occurring vascular reactions, on the other hand, are but slightly affected by antihistaminics. Intravenous or subcutaneous administration of rutin has no clear-cut effect on chemosis; it is however able to inhibit the vascular reaction. 相似文献
7.
8.
9.
10.