全文获取类型
收费全文 | 22628篇 |
免费 | 2853篇 |
国内免费 | 2965篇 |
专业分类
化学 | 9722篇 |
晶体学 | 182篇 |
力学 | 1526篇 |
综合类 | 164篇 |
数学 | 1285篇 |
物理学 | 7562篇 |
综合类 | 8005篇 |
出版年
2024年 | 55篇 |
2023年 | 184篇 |
2022年 | 425篇 |
2021年 | 472篇 |
2020年 | 666篇 |
2019年 | 520篇 |
2018年 | 539篇 |
2017年 | 677篇 |
2016年 | 744篇 |
2015年 | 816篇 |
2014年 | 1039篇 |
2013年 | 1413篇 |
2012年 | 1241篇 |
2011年 | 1355篇 |
2010年 | 1101篇 |
2009年 | 1330篇 |
2008年 | 1383篇 |
2007年 | 1667篇 |
2006年 | 1474篇 |
2005年 | 1396篇 |
2004年 | 1166篇 |
2003年 | 1163篇 |
2002年 | 1128篇 |
2001年 | 908篇 |
2000年 | 869篇 |
1999年 | 749篇 |
1998年 | 539篇 |
1997年 | 544篇 |
1996年 | 465篇 |
1995年 | 376篇 |
1994年 | 361篇 |
1993年 | 291篇 |
1992年 | 267篇 |
1991年 | 211篇 |
1990年 | 181篇 |
1989年 | 190篇 |
1988年 | 147篇 |
1987年 | 99篇 |
1986年 | 43篇 |
1985年 | 64篇 |
1984年 | 32篇 |
1983年 | 18篇 |
1982年 | 35篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1974年 | 4篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This work develops the dynamics of a perfectly elastic solid model for application to the outer crust of a magnetised neutron
star. Particular attention is given to the Noether identities responsible for energy-momentum conservation, using a formulation
that is fully covariant, not only (as is usual) in a fully relativistic treatment but also (sacrificing accuracy and elegance
for economy of degrees of gravitational freedom) in the technically more complicated case of the Newtonian limit. The results
are used to obtain explicit (relativistic and Newtonian) formulae for the propagation speeds of generalised (Alfven type)
magneto-elastic perturbation modes. 相似文献
102.
高Q-腔中量子化平移运动与原子内态布居的关系 总被引:1,自引:0,他引:1
讨论了在驻波腔场中两能级原子的量子化平移运动与原子内态布居间的相互影响。结果表明原子量子化平移运动敏感地依赖于原子的内态布居。 相似文献
104.
How can the basic compatibility of theory and observations be investigated for nonlinear processes without requiring stochastic characterizations for residual error terms? The present paper proposes a flexible least-cost approach. For each possible estimatex for the sequence of process states, letc D (x) andx M(x) denote the costs incurred for deviations away from the prior dynamic specifications and prior measurement specifications, respectively. Define the cost-efficiency frontier to be the greatest lower bound for the set of all possible cost pairs [c D (x),c M(x)], conditional on the given observations. State sequence estimatesx that attain the cost-efficiency frontier indicate the possible ways that the actual process could have developed over time in a manner minimally incompatible with the prior dynamic and measurement specifications. An algorithm is developed for the exact sequential updating of the cost-efficient state sequence estimates as the duration of the process increases and additional observations are obtained. 相似文献
105.
使用“对称性匹配簇-组态相互作用”方法,对Li2分子三重态的第一激发态、LiH分子的基态、单重态的第一和第二激发态的几何构型与谐振频率进行了优化计算.利用“群操作求和”方法分别对这4个态进行单点能扫描计算,并拟合出了相应各态的Murrell-Sorbie势能函数.使用多种方法对Li2H分子的基态结构进行优化,并用优选出的密度泛函(B3P86)方法对该分子进行了进一步的频率计算.结果发现Li2H分子的基态稳态结构为C2v构型,在此基础上用多体项展式理论导出了它的解析势能函数,其等值势能图准确再现了Li2H分子的结构特征和离解能.首次报导了该分子对称伸缩振动等值势能图中存在的两个对称鞍点,对应于反应LiH Li→Li2H,活化能大约为18.7×4.184 KJ/mol. 相似文献
106.
非对称三态叠加多模泛函叠加态光场的高次压缩——广义电场分量的不等幂次和压缩效应研究 总被引:2,自引:0,他引:2
多模真空态|{0j}〉q与两个空间强度分布特征不同的多模复共轭泛函相干态|{f(j a)*(x,y,z)}〉q和|{f(j b)*(x,y,z)}〉q的线性叠加组成的三态叠加多模泛函叠加态光场|ψ(f3)〉q,利用多模压缩态理论,研究了态|ψ(f3)〉q中广义电场分量的不等幂次高次和(H)压缩特性.结果表明:在一定的条件下,态|ψ(f3)〉q的广义电场分量可呈现出周期性变化的任意奇数次和任意偶数次的不等幂次高次H压缩效应;光场的经典振幅和经典初始相位的任意非对称空间分布特征对其压缩程度和压缩深度等压缩特性将产生直接的影响. 相似文献
107.
Chemical techniques were employed to synthesize CdS nanoparticles embedded in polymer (PEG 300) and sol-gel silica matrices. Systematic growth of particles (radius 3–9 nm) was obtained by adjusting post-deposition annealing temperature and time to examine the dependence of surface-state–related luminescence on particle size. Photoluminescence (PL) peak energy showed a linear dependence with a gentle slope in the weak confinement region and a steep slope in the strong confinement region, the divergence being observed near the excitonic Bohr radius for CdS. The empirical relation proposed for the weak confinement region could be used for estimating chemically prepared CdS nanoparticle size with a high degree of reliability from PL peak energy. 相似文献
108.
Let { X n} be a Markov chain that is either f -mixing or satisfies the Poisson equation.In this note we obtain the convergence rate under L 1 -criterion for bounded functions of the X k 's. And in the hidden Markov model setup { (X n ,Y n ) }we study the kernel estimate of the density of the observed variables { Y n }when a 'stable' status is reached. 相似文献
109.
The collision-generated hybridization which has been found responsible for the on-site mixing of the atomic-likef-state and the band-liked states in mixed valence solids has been studied for the cerium solid. A practical expression which depends on the lattice
constant and temperature has been obtained for the collision-generated hybridization. Numerical calculations show that the
valence varies continuously with lattice constant and that temperature makes the transition smoother. The collision-generated
hybridization is found to be of significant strength in the intermediate valence regime; but over a wide range of the valence
near 3.5 it varies rather slowly without preferring a particular valence. Factors which can assist the collision-generated
hybridization in stabilizing the mixed valence phase at a particular lattice constant are discussed. 相似文献