全文获取类型
收费全文 | 46036篇 |
免费 | 3961篇 |
国内免费 | 6418篇 |
专业分类
化学 | 31567篇 |
晶体学 | 1406篇 |
力学 | 1101篇 |
综合类 | 275篇 |
数学 | 8840篇 |
物理学 | 13226篇 |
出版年
2024年 | 87篇 |
2023年 | 476篇 |
2022年 | 1101篇 |
2021年 | 1046篇 |
2020年 | 1362篇 |
2019年 | 1417篇 |
2018年 | 1200篇 |
2017年 | 1454篇 |
2016年 | 1498篇 |
2015年 | 1417篇 |
2014年 | 2056篇 |
2013年 | 3470篇 |
2012年 | 2282篇 |
2011年 | 3525篇 |
2010年 | 2752篇 |
2009年 | 3170篇 |
2008年 | 3342篇 |
2007年 | 3188篇 |
2006年 | 2827篇 |
2005年 | 2643篇 |
2004年 | 2291篇 |
2003年 | 1870篇 |
2002年 | 1698篇 |
2001年 | 1274篇 |
2000年 | 1229篇 |
1999年 | 1051篇 |
1998年 | 863篇 |
1997年 | 772篇 |
1996年 | 690篇 |
1995年 | 688篇 |
1994年 | 635篇 |
1993年 | 554篇 |
1992年 | 448篇 |
1991年 | 326篇 |
1990年 | 225篇 |
1989年 | 217篇 |
1988年 | 173篇 |
1987年 | 128篇 |
1986年 | 128篇 |
1985年 | 134篇 |
1984年 | 110篇 |
1983年 | 71篇 |
1982年 | 95篇 |
1981年 | 84篇 |
1980年 | 89篇 |
1979年 | 63篇 |
1978年 | 63篇 |
1977年 | 45篇 |
1976年 | 31篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis. 相似文献
5.
Rajiv Manohar G. Tripathi A.K. Srivastava A.K. Prajapati 《Journal of Physics and Chemistry of Solids》2006,67(11):2300-2304
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared. 相似文献
6.
采用交流法测量大功率商用钛酸钡(BT)陶瓷加热器的电阻和加热功率随温度的变化关系.结果显示,BT陶瓷的电导特性在80℃附近出现了明显的转变,从低温时的极化子跳跃导电转变为高温时的能带导电,此时,电阻出现极小值,而加热功率出现极大值. 相似文献
7.
(S)-2-[2-(p-Tolylsulfinyl)phenyl]acetaldehyde reacts with different O-silylated ketenethioacetals in the presence of Yb(OTf)3 yielding β-hydroxythioesters in high yields and diastereoselectivities. The obtained compounds were readily transformed into β-hydroxyacids and their corresponding diols. These Mukaiyama aldol reactions are a direct evidence of the ability of the sulfinyl group to control 1,5- and 1,6-asymmetric induction processes. 相似文献
8.
A Volterra type integral equation in a Hilbert space with an additional linear operator L and a spectral parameter depending
on time is considered. If the parameter does not belong to the spectrum of L unconditional solvability of the considered problem
is proved. In the case where the initial value of the parameter coincides with some isolated point of the spectrum of the
operator L sufficient conditions for solvability are established. The obtained results are applied to the partial integral
equations associated with a contact problem of the theory of elasticity. 相似文献
9.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
10.
GAO Jing ZHOU Xiaohua CHEN Xun Chongqing University Chemical Engineering Department Chongqing China 《Chinese Journal of Reactive Polymers》2006,(2)
1. INTRODUCTION In the process of coking plant, about 30%~35% sulfur is transformed to H2S and some other sulfide, which form impurity in coal gas together with NH3 and HCN. Only 0.1% H2S containing in air can lead to die, so it is very important to carry on desulphurization and decyanation with coal gas [1~3]. Currently desulphurization and decyanation craft technique have Dry Oxidation Technology, Wet Oxidation Technology and Liquid Absorption Technology [2] three main kinds. The… 相似文献