全文获取类型
收费全文 | 1269篇 |
免费 | 3篇 |
专业分类
化学 | 987篇 |
晶体学 | 5篇 |
力学 | 24篇 |
数学 | 70篇 |
物理学 | 186篇 |
出版年
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 25篇 |
2017年 | 36篇 |
2016年 | 27篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 63篇 |
2012年 | 46篇 |
2011年 | 53篇 |
2010年 | 54篇 |
2009年 | 57篇 |
2008年 | 48篇 |
2007年 | 44篇 |
2006年 | 30篇 |
2005年 | 40篇 |
2004年 | 37篇 |
2003年 | 39篇 |
2002年 | 43篇 |
2001年 | 42篇 |
2000年 | 31篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1992年 | 12篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1973年 | 12篇 |
1972年 | 8篇 |
1971年 | 15篇 |
1970年 | 9篇 |
1969年 | 15篇 |
1967年 | 12篇 |
排序方式: 共有1272条查询结果,搜索用时 15 毫秒
61.
62.
Shaikhutdinova S. I. Kazantseva T. I. Gusarova N. K. Dmitriev V. I. Trofimov B. A. 《Russian Journal of General Chemistry》2001,71(1):58-60
4-Methoxybenzyl chloride reacts with elemental (red or white) phosphorus under the conditions of phase-transfer catalysis (concentrated aqueous KOH, dioxane, benzyltriethylammonium chloride, 85-90°C, argon) to give as major product tris(4-methoxybenzyl)phosphine oxide in up to 45% yield. With white phosphorus at lower (70°C) temperature this reaction yields mainly bis(4-methoxybenzyl)phosphine oxide. Phosphine reacts with 4-methoxybenzyl chloride in superbasic KOH-DMSO suspension, and under definite conditions bis(4-methoxybenzyl)phosphine oxide is predominantly formed. 相似文献
63.
S. E. Korostova B. A. Trofimov L. N. Sobenina A. I. Mikhaleva M. V. Sigalov 《Chemistry of Heterocyclic Compounds》1982,18(10):1043-1045
2-(1-Naphthyl)- and 2-(2-naphthyl)pyrroles and their 1-vinyl derivatives were synthesized in 22–64% yields by the reaction of 1- and 2-acetylnaphthalene oximes with acetylene at both atmospheric pressure and elevated pressures in an alkali metal hydroxide-dimethyl sulfoxide system.See [1] for communication 22.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1351–1353, October, 1982. 相似文献
64.
A new general approach to anionic transformations of acetylenes using superbasic media has been developed. It allows series of new reactions which are not undergone by acetylene under conventional conditions. The triads Se8KOHdimethylsulfoxide (DMSO), Se8KOHDMSO, TeKOH-hexamethyl-phosphorictriamide (HMPA) are proposed as new effective reagents for the preparation of unsaturated compounds of sulfur, selenium and tellerium. A series of reactions of acetylene with sulfur, selenium and tellerium proceeding in DMSO or HMPA in the presence of alkali and water at 80–120° leading to divinyl sulfide, divinyl selenide and divinyl teluride in 25–80% yields have been found. Thiophen, di-1-(1,3-butadienyl) sulfide, 1-vinyl-2-thiabicyclo[3.2.0]hept-3-ene, and dihydrothiophen have been obtained by the reaction of vinylacetate with sulfur. The reaction of vinylacetylene with selenium affords selenophen, di-1-(1,3-butadienyl) selenide, 1-vinyl-2-selenabicyclo[3.2.0]hept-3-ene, methyl (1-(1,3-butadienyl) sulfide, and methylthiomethyl 1-(1,4-butadienyl) selenide, vinyl 1-(1,3-butadienyl) sulfide, and methylthiomethyl 1-(1,3-butadienyl) selenide (the latter two with DMSO participation). The reaction of vinylacetate with tellerium gives mainly di-1-(1,3-butadienyl) telluride. A series of reactions between DMSO and selenium leading to dimethyl sulfide, dimethyl sulfoselenide, and methylthiomethyl selenide have been observed. 相似文献
65.
66.
The possibility of formation of a basic (stationary) and an additional (moving) high-absorption domain in an optically bistable system, based on high absorption, is demonstrated. A semiconductor with the absorption coefficient dependent on the concentration of free charge carriers in the conduction band is considered as a nonlinear medium. Under certain conditions, an optical beam passing through the stationary high-absorption domain acquires an annular profile and, after traveling a certain distance, transforms into a Gaussian beam with an intensity on the axis sufficient to switch the medium-beam system to the upper state. This moving domain periodically disappears and reappears due to diffusion processes. 相似文献
67.
68.
69.
70.
The corresponding 2-bromomethyl derivatives of benzofuran and indole were obtained by bromination of 2-methyl-3-carbethoxy-5-methoxybenzofuran and 1,2-dimethyl-3-earbethoxy-5-methoxyindole with N-bromosuccinimide. A number of alkyl(aryl)thiomethyl and dialkylaminomethyl derivatives were obtained by reaction of the 2-bromomethyl derivatives with nucleophilic reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 308–311, March, 1973. 相似文献