全文获取类型
收费全文 | 431770篇 |
免费 | 2970篇 |
国内免费 | 1112篇 |
专业分类
化学 | 210027篇 |
晶体学 | 6606篇 |
力学 | 23081篇 |
综合类 | 18篇 |
数学 | 69827篇 |
物理学 | 126293篇 |
出版年
2020年 | 3305篇 |
2019年 | 3894篇 |
2018年 | 15166篇 |
2017年 | 15154篇 |
2016年 | 12917篇 |
2015年 | 4588篇 |
2014年 | 6959篇 |
2013年 | 15526篇 |
2012年 | 14838篇 |
2011年 | 23581篇 |
2010年 | 15798篇 |
2009年 | 16350篇 |
2008年 | 18897篇 |
2007年 | 20832篇 |
2006年 | 11661篇 |
2005年 | 11486篇 |
2004年 | 11003篇 |
2003年 | 10653篇 |
2002年 | 9663篇 |
2001年 | 10576篇 |
2000年 | 8004篇 |
1999年 | 6098篇 |
1998年 | 5207篇 |
1997年 | 4998篇 |
1996年 | 4761篇 |
1995年 | 4354篇 |
1994年 | 4191篇 |
1993年 | 4039篇 |
1992年 | 4680篇 |
1991年 | 4895篇 |
1990年 | 4732篇 |
1989年 | 4812篇 |
1988年 | 4724篇 |
1987年 | 4760篇 |
1986年 | 4464篇 |
1985年 | 5666篇 |
1984年 | 5689篇 |
1983年 | 4665篇 |
1982年 | 4810篇 |
1981年 | 4778篇 |
1980年 | 4408篇 |
1979年 | 5002篇 |
1978年 | 5131篇 |
1977年 | 5263篇 |
1976年 | 5178篇 |
1975年 | 4791篇 |
1974年 | 4677篇 |
1973年 | 4810篇 |
1972年 | 3635篇 |
1968年 | 3195篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
Condensation of α-halocarbonyl compounds and 2-mercaptobenzimidazole gives thiazolo-[3,2-a]benzimidazoles. This condensation occurred at the mercapto group of the benzimidazole followed by cyclization to form the thiazole ring. This was confirmed by the examination of the mass spectra of 2- and 3-methylthiazolo[3,2-a]benzimidazoles, 2- and 3-phenylthiazolo[3,2-a]-benzimidazoles, and their derivatives. 相似文献
996.
997.
N. K. Gusarova N. A. Chernysheva M. Ya. Khil'ko S. V. Yas'ko L. M. Sinegovskaya N. N. Chipanina N. A. Korchevin B. A. Trofimov 《Russian Journal of General Chemistry》2005,75(8):1247-1250
Selective monoaddition of carbonodithioate anions to divinyl sulfoxide gives rise to O-alkyl S-[2-(vinylsulfinyl)ethyl] carbonodithioates [ROC(S)SK, R = Et, Bu; 42–50°C, 6 h, NaHCO3, aqueous benzene]. 相似文献
998.
999.
The conjugate of mitomycin C (MMC) with linear (1----3)-beta-D-glucan from Alcaligenes faecalis var. myxogenes IFO 13140 was synthesized and its antitumor activities investigated. The conjugate (MMC-carboxymethylated linear (1----3)-beta-D-glucan (CMPS)) was obtained by treatment of CMPS with MMC in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide. In vitro cytotoxicity of MMC-CMPS against L1210 leukemia cells was similar to that of MMC. In i.p.-i.p. system in vivo against P388 leukemia in mice, the maximum increase of MMC-CMPS conjugate in life span (ILSmax) was higher than that of MMC but the therapeutic index was reduced. However, the antitumor activity of MMC-CMPS conjugate against subcutaneously implanted sarcoma 180 solid tumor in mice by i.p. administration was similar to that of MMC at a dose of 1.5 mg eq MMC/kg/d x 7 and the reduction of the number of leukocytes caused by MMC was suppressed by attaching MMC to CMPS. In addition, on assay using serum of sarcoma 180 solid tumor-bearing mice with injection of MMC-CMPS conjugate, a drastic loss of tumor cells and an increase in polymorphonuclear leukocytes (PMN) were observed. This result suggested that MMC-CMPS conjugate induced tumor-regressing factor similar to CMPS. 相似文献
1000.
M. Zh. Ovakimyan S. K. Barsegyan A. S. Pogosyan N. M. Kikoyan M. G. Indzhikyan 《Russian Journal of General Chemistry》2006,76(11):1757-1759
Dehydrogenation of 1-(diphenylphosphinoyl)-2-hydrazino-substituted ethanes and N-butyl-N′-phenylhydrazine to the corresponding hydrazone derivatives is performed. Both reactions were established to involve predominantly, if not exclusively, an azo intermediate. 相似文献