全文获取类型
收费全文 | 3052篇 |
免费 | 99篇 |
国内免费 | 15篇 |
专业分类
化学 | 2483篇 |
晶体学 | 31篇 |
力学 | 29篇 |
数学 | 209篇 |
物理学 | 414篇 |
出版年
2023年 | 18篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 43篇 |
2019年 | 45篇 |
2018年 | 28篇 |
2017年 | 23篇 |
2016年 | 59篇 |
2015年 | 58篇 |
2014年 | 91篇 |
2013年 | 192篇 |
2012年 | 152篇 |
2011年 | 182篇 |
2010年 | 125篇 |
2009年 | 109篇 |
2008年 | 184篇 |
2007年 | 164篇 |
2006年 | 195篇 |
2005年 | 192篇 |
2004年 | 176篇 |
2003年 | 143篇 |
2002年 | 149篇 |
2001年 | 53篇 |
2000年 | 45篇 |
1999年 | 28篇 |
1998年 | 41篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 22篇 |
1994年 | 29篇 |
1993年 | 18篇 |
1992年 | 23篇 |
1991年 | 19篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1986年 | 18篇 |
1985年 | 33篇 |
1984年 | 48篇 |
1983年 | 29篇 |
1982年 | 40篇 |
1981年 | 43篇 |
1980年 | 31篇 |
1979年 | 29篇 |
1978年 | 18篇 |
1977年 | 22篇 |
1976年 | 19篇 |
1975年 | 19篇 |
1974年 | 22篇 |
1973年 | 12篇 |
排序方式: 共有3166条查询结果,搜索用时 187 毫秒
61.
The molar enthalpies of transfer t
H
° of some divalent metal ions (M-Mn, Co, Ni and Zn) and their chloro complexes from N,N-dimethyl-for-mamide (DMF) to N,N-dimethylacetamide (DMA) have been determined using the tetraphenylarsonium-tetraphenylborate (TATB) assumption at 25°C. Although physicochemical properties of DMF and DMA as solvent are similar, the t
H
°(M
2+) value increased significantly in the order Mnt
H
° values for the mono-and dichloro complexes showed also a strong metal dependence, while those for the triand tetrachloro complexes practically do not. These results can be reasonably explained in terms of steric hindrance upon solvation of the metal ions and complexes in DMA. 相似文献
62.
63.
Numerical Algorithms - In this paper, we propose an infeasible arc-search interior-point algorithm for solving nonlinear programming problems. Most algorithms based on interior-point methods are... 相似文献
64.
A bioassay-directed fractionation of the cytotoxic constituents of the Japanese sea hare Dolabella auricularia resulted in the isolation of two 35-membered depsipeptides dolastatin G (1) and nordolastatin G (2), which showed cytotoxicity against HeLa S(3) cells with IC(50) values of 1.0 and 5.3 &mgr;g/mL, respectively. The gross structures of these substances were established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure of 1 was determined by chiral HPLC analysis of amino acid components obtained from acid hydrolysis of 1 and by the enantioselective syntheses of two degradation products arising from polyketide portions. Nordolastatin G (2) is a congener that has the same absolute stereochemistry as that of 1. 相似文献
65.
In the presence of palladium complexes as catalysts, fluorinated disilanes add to 1,3-dienes, metehyl vinyl ketone and p-benzoquinone to give mainly 1,4-addition products. 相似文献
66.
Sung Il Hong Toshikazu Kurosaki Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1972,10(11):3405-3419
Polyoxime-urethanes have been synthesized from dioximes and diisocyanates, and their structures have been ascertained by elemental analysis and infrared spectroscopy. They can be represented by the general formula: These polymer films were photolyzed by using a high-pressure 100-W mercury lamp, and the rate of decomposition of the N? O bond was determined by use of ultraviolet and infrared spectra, or comparing the photochemical behavior with that of corresponding model compounds. Upon irradiating these polymers in the presence or absence of sensitizers or a hydrogen donor, there were obtained photolyzed polymers of low molecular weight, of which the molecular weights were estimated by observing the viscosity changes. To deduce the mechanism of photodegradation of polyoxime-urethane, photolysis of benzophenone oxime-phenyl urethane was investigated as a model compound. 相似文献
67.
Yoko Nambu Takeshi Endo Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):1937-1943
Reductive S-monoacylation of lipoamide with some carboxylic acids and tri-n-butylphosphine was carried out in acetonitrile to obtain the corresponding S-monoacylated compounds in excellent yield. This method was applied to the preparation of S-monoacylated dihydrolipoyl polymer with a neighboring thiol group. The acyl transfer from the polymer to cyclohexylamine was enhanced as much as 64 times by adding silver perchlorate. 相似文献
68.
The proposed structures of patellamides B and C, cytotoxic lipophilic cyclic peptides from a marine tunicate, have been revised on the basis of the spectral data of their partial hydrolysates, and their revised structures have been synthetically confirmed by the use of diphenyl phosphorazidate(DPPA) and diethyl phosphorocyanidate(DEPC). 相似文献
69.
H Moriya C Moriwaki S Akimoto K Yamaguchi M Iwadare 《Chemical & pharmaceutical bulletin》1967,15(11):1662-1668
70.
Makoto Oba 《Journal of organometallic chemistry》2006,691(6):1151-1153
A novel [2.2]metacyclophane in which two benzene rings are linked together with a carbon-carbon double bond and a disilane unit was prepared. Photolysis of the cyclophane in the presence of oxygen afforded the 4,5-dihydro-4,5-disilapyrene derivative via a transannular dehydrogenation reaction. 相似文献