全文获取类型
收费全文 | 5078篇 |
免费 | 774篇 |
国内免费 | 413篇 |
专业分类
化学 | 2746篇 |
晶体学 | 34篇 |
力学 | 176篇 |
综合类 | 34篇 |
数学 | 520篇 |
物理学 | 1601篇 |
无线电 | 1154篇 |
出版年
2024年 | 21篇 |
2023年 | 94篇 |
2022年 | 141篇 |
2021年 | 208篇 |
2020年 | 227篇 |
2019年 | 166篇 |
2018年 | 137篇 |
2017年 | 168篇 |
2016年 | 233篇 |
2015年 | 270篇 |
2014年 | 276篇 |
2013年 | 365篇 |
2012年 | 247篇 |
2011年 | 249篇 |
2010年 | 183篇 |
2009年 | 262篇 |
2008年 | 278篇 |
2007年 | 330篇 |
2006年 | 311篇 |
2005年 | 217篇 |
2004年 | 197篇 |
2003年 | 219篇 |
2002年 | 183篇 |
2001年 | 175篇 |
2000年 | 142篇 |
1999年 | 132篇 |
1998年 | 108篇 |
1997年 | 89篇 |
1996年 | 77篇 |
1995年 | 52篇 |
1994年 | 47篇 |
1993年 | 35篇 |
1992年 | 40篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 34篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 30篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 19篇 |
1973年 | 14篇 |
排序方式: 共有6265条查询结果,搜索用时 31 毫秒
1.
Vyacheslav V. Sentyurin Oleg A. Levitskiy Tatiana V. Magdesieva 《Current Opinion in Electrochemistry》2020
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications. 相似文献
2.
Renny Mathew Karolina A. Uchman Lydia Gkoura Chris J. Pickard Maria Baias 《Magnetic resonance in chemistry : MRC》2020,58(11):1018-1025
A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of ab initio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated 1H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs. 相似文献
3.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
4.
在离子波纹摆动器中,改变电子束的入射方向,保证了离子波纹场的纵向分量为零,从而消除了纵向电场对离子波纹激光的不利影响。给出了束电子的运动轨迹,运用Madey定理计算了小振幅条件下该离子波纹激光的小信号增益。 相似文献
5.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
6.
7.
8.
9.
We provide a rigorous derivation of an asymptotic formula for perturbations in the eigenvalues caused by the presence of a finite number of inhomogeneities of small diameter with conductivity different from the background conductivity. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
10.
S.V.N Bhaskara Rao T.K. Balasubramanian 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,87(2):203-210
Fresh computations of rovibrational matrix elements of the polarizability α[=(α||+2α⊥)/3] and the polarizability anisotropy γ(=α||−α⊥) of the heteronuclear isotopomers, HD, HT, and DT, of the hydrogen molecule are presented. The computations combine the most accurate polarizability functions α(R) and γ(R) (R being the bond distance) on the one hand and the most accurate adiabatic potential on the other. The calculations are extended to the product operators xα and xγ where x is the centre of mass to centre of charge separation in the heteronuclear species. The latter matrix elements are needed, additionally, for elucidating the absorption intensities of some of the zero-phonon rovibrational transitions peculiar to the heteronuclear species in the crystalline phase. 相似文献