全文获取类型
收费全文 | 11189篇 |
免费 | 18篇 |
国内免费 | 35篇 |
专业分类
系统科学 | 41篇 |
丛书文集 | 205篇 |
教育与普及 | 40篇 |
理论与方法论 | 49篇 |
现状及发展 | 5180篇 |
研究方法 | 500篇 |
综合类 | 5096篇 |
自然研究 | 131篇 |
出版年
2013年 | 97篇 |
2012年 | 174篇 |
2011年 | 298篇 |
2010年 | 69篇 |
2008年 | 194篇 |
2007年 | 209篇 |
2006年 | 206篇 |
2005年 | 231篇 |
2004年 | 192篇 |
2003年 | 192篇 |
2002年 | 201篇 |
2001年 | 286篇 |
2000年 | 296篇 |
1999年 | 192篇 |
1992年 | 176篇 |
1991年 | 149篇 |
1990年 | 154篇 |
1989年 | 159篇 |
1988年 | 166篇 |
1987年 | 158篇 |
1986年 | 168篇 |
1985年 | 229篇 |
1984年 | 141篇 |
1983年 | 140篇 |
1982年 | 98篇 |
1981年 | 116篇 |
1980年 | 151篇 |
1979年 | 377篇 |
1978年 | 284篇 |
1977年 | 304篇 |
1976年 | 220篇 |
1975年 | 222篇 |
1974年 | 346篇 |
1973年 | 278篇 |
1972年 | 300篇 |
1971年 | 308篇 |
1970年 | 422篇 |
1969年 | 367篇 |
1968年 | 371篇 |
1967年 | 336篇 |
1966年 | 295篇 |
1965年 | 218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 15 毫秒
181.
182.
183.
Binding of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to adenylylated (E--11) glutamine synthetase is cooperative and time-dependent, with 3 dye sites per subunit. In fluorescence polarization experiments TNS and pyrene butyrate give normalized Perrin plots that indicate a symmetrical arrangement of dye excited state dipoles, relative to the rotational axis of the oblate ellipsoid of the dodecameric native enzyme. 相似文献
184.
The present study demonstrates that a) serum based culture medium degrades 125I inhibits its proteolytic activity leading to the recovery of more insulin secreted by islets cultured in the presence of high glucose concentration alone or with glucagon; c) aprotinin also favoured the accumulation of secreted insulin by protecting the hormone from a residual degradative capacity of the hear treated serum. 相似文献
185.
The ability of dog renal cortex slices to accumulate beta-methyl-glucoside or glycine is enhanced by the flavonoid (+)-catechin at a concentration of 3.5 mM. This stimulatory effect is apparently due to a decreased rate of efflux of either substrate. On the other hand, the uptake of p-amino-hippuric acid and N1-methyl-nicotinamide is inhibited by (+)-catechin. The drug at the same concentration is without action on amino-acid transport by guinea-pig intestine in vitro. 相似文献
186.
A study was made of the effect of daily administration of kanamycin (400 mg kg-1) on the hearing of Wistar albino and Lister hooded (pigmented) rats, which had been conditioned to discriminate an acoustic signal. In all animals except one, the drug caused severe, permanent hearing impairment and there was no difference between albino and pigmented rats in onset or degree. Other work has suggested a mediatory role for melanin pigment in such drug ototoxicity but the significance of this must be questioned in view of the failure to find any differences in functional deficit. 相似文献
187.
Biopsies of subjects affected by ulcerous colitis were stained with ruthenium Red. Alterations of the cellular coat and glycocalyx of the epithelial cells of the colon were identified. 相似文献
188.
189.
190.