全文获取类型
收费全文 | 3129篇 |
免费 | 60篇 |
国内免费 | 12篇 |
专业分类
化学 | 2348篇 |
晶体学 | 40篇 |
力学 | 36篇 |
数学 | 176篇 |
物理学 | 601篇 |
出版年
2022年 | 18篇 |
2021年 | 32篇 |
2020年 | 18篇 |
2019年 | 42篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 37篇 |
2015年 | 31篇 |
2014年 | 49篇 |
2013年 | 149篇 |
2012年 | 108篇 |
2011年 | 136篇 |
2010年 | 83篇 |
2009年 | 73篇 |
2008年 | 145篇 |
2007年 | 157篇 |
2006年 | 156篇 |
2005年 | 160篇 |
2004年 | 130篇 |
2003年 | 124篇 |
2002年 | 133篇 |
2001年 | 46篇 |
2000年 | 66篇 |
1999年 | 56篇 |
1998年 | 49篇 |
1997年 | 41篇 |
1996年 | 44篇 |
1995年 | 35篇 |
1994年 | 37篇 |
1993年 | 41篇 |
1992年 | 57篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 44篇 |
1987年 | 47篇 |
1986年 | 36篇 |
1985年 | 64篇 |
1984年 | 62篇 |
1983年 | 38篇 |
1982年 | 43篇 |
1981年 | 47篇 |
1980年 | 37篇 |
1979年 | 56篇 |
1978年 | 52篇 |
1977年 | 39篇 |
1976年 | 47篇 |
1975年 | 38篇 |
1974年 | 38篇 |
1973年 | 44篇 |
排序方式: 共有3201条查询结果,搜索用时 15 毫秒
111.
Transparent thin (ca. 100 nm) films of silica-surfactant mesostructured materials were deposited on borosilicate glass plates and soda-lime glass tubes from aqueous solutions containing tetraethoxysilane, alkyltrimethylammonium chloride, ammonia, and methanol. By calcination in air, the films became mesoporous (BET surface area of 700-900 m2 g-1) with pore diameter 2.0-2.8 nm. 相似文献
112.
Akira Hirota Masahira Nakagawa Heiichi Sakai Akira Isogai Kazuo Furihata Haruo Seto 《Tetrahedron letters》1985,26(32):3845-3848
Feeding experiments with [2-3H3]acetate and [2-13C2H3]acetate in Thom No. 14 indicated that the hydrogen at C-2 in terrecyclic acid A is incorporated without migration from the precursor acetic acid; the results favour our group's earlier speculation for the cyclization to the tricyclic skeleton in the biosynthetic scheme. 相似文献
113.
1-Phenylcyclopentadiene fused with two homoadamantene units at the 2,3- and 4,5-positions (4) was deprotonated with KH to lead to the quantitative formation of the corresponding cyclopentadienyl (Cp) anion 3(-). This anion was oxidized by AgCl to afford an orange crystalline solid consisting of Cp radical 3(?) and cyclopentadiene 4. The ESR spectrum in hexane exhibited approximately 15 lines, demonstrating that the two homoadamantene frameworks were equivalent and that the C1-C2(Ph)-C3 moiety of the five-membered ring formed a symmetrical allyl-like radical in agreement with the prediction by DFT calculation. The reaction of the Cp radical 3(?) with an oxygen molecule in the presence of Ag(+)SbF(6)(-) afforded the SbF(6)(-) salt of a phenylpyrylium ion annelated with two homoadamantene frameworks (8(+)SbF(6)(-)). 相似文献
114.
115.
116.
Kazuo Sugiyama Tadao Nakaya Minoru Imoto 《Journal of polymer science. Part A, Polymer chemistry》1972,10(1):205-215
A study of the photopolymerization of vinyl monomers in the presence of tetramethyltetrazene (TMT) was made. TMT was found to act as an effective sensitizer. In the photopolymerization of vinyl monomers such as methyl methacrylate or styrene the rate of polymerization was expressed by the equation: Rp = k[TMT]1/2[monomer]. The chain-transfer constant of TMT under ultraviolet irradiation was estimated to be 3.8 × 10?2 for the above monomers. A linear correlation was found to exist between the reactivity of dimethylamino radical toward the vinyl monomers and e values for the corresponding monomers. 相似文献
117.
K Kameo Y Asami K Ogawa T Matsunaga S Saito K Tomisawa K Sota 《Chemical & pharmaceutical bulletin》1989,37(5):1260-1267
2-Acetylthio-3-benzoylpropionic acid derivatives having two benzene rings or condensed-ring moieties were prepared, and tested for hypolipidemic activity in normal rats. Some of these compounds were active. 2-Acetylthio-3-[4-(phenylthio)benzoyl]propionic acid (10) and its derivatives seemed to have the most potent hypocholesterolemic activities. Compound 10 showed strong activity, especially in cholesterol-fed rats. 相似文献
118.
Ai Ito Takamasa Amaki Ayako Ishii Kazuo Fukuda Ryu Yamasaki Iwao Okamoto 《Tetrahedron letters》2018,59(45):3994-3998
Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom. 相似文献
119.