全文获取类型
收费全文 | 115038篇 |
免费 | 13479篇 |
国内免费 | 15285篇 |
专业分类
化学 | 79327篇 |
晶体学 | 1228篇 |
力学 | 6244篇 |
综合类 | 1395篇 |
数学 | 14616篇 |
物理学 | 40992篇 |
出版年
2024年 | 208篇 |
2023年 | 1109篇 |
2022年 | 2449篇 |
2021年 | 3706篇 |
2020年 | 3417篇 |
2019年 | 3272篇 |
2018年 | 2926篇 |
2017年 | 3455篇 |
2016年 | 4180篇 |
2015年 | 3847篇 |
2014年 | 5266篇 |
2013年 | 9146篇 |
2012年 | 6591篇 |
2011年 | 6569篇 |
2010年 | 5749篇 |
2009年 | 6957篇 |
2008年 | 7229篇 |
2007年 | 7588篇 |
2006年 | 6764篇 |
2005年 | 5599篇 |
2004年 | 5104篇 |
2003年 | 4685篇 |
2002年 | 6456篇 |
2001年 | 3750篇 |
2000年 | 3267篇 |
1999年 | 2719篇 |
1998年 | 2493篇 |
1997年 | 2114篇 |
1996年 | 2015篇 |
1995年 | 1767篇 |
1994年 | 1630篇 |
1993年 | 1424篇 |
1992年 | 1371篇 |
1991年 | 985篇 |
1990年 | 797篇 |
1989年 | 745篇 |
1988年 | 696篇 |
1987年 | 508篇 |
1986年 | 440篇 |
1985年 | 519篇 |
1984年 | 427篇 |
1983年 | 237篇 |
1982年 | 440篇 |
1981年 | 567篇 |
1980年 | 516篇 |
1979年 | 552篇 |
1978年 | 417篇 |
1977年 | 324篇 |
1976年 | 270篇 |
1973年 | 193篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Framstad N. C. Øksendal B. Sulem A. 《Journal of Optimization Theory and Applications》2004,121(1):77-98
We give a verification theorem by employing Arrow's generalization of the Mangasarian sufficient condition to a general jump diffusion setting and show the connections of adjoint processes to dynamic programming. The result is applied to financial optimization problems. 相似文献
992.
《Magnetic resonance in chemistry : MRC》2003,41(8):626-628
15N isotopic enrichment was necessary for the unequivocal assignment of the 1H NMR lines to the protons in the NH–OH fragment of benzohydroxamic acid, BHXA, C6H5CONHOH, in dry dimethyl sulfoxide solutions. The assignment [δ(NH) = 11.21, δ(OH) = 9.01, 1J(15N,1H) = 102.2 Hz, 2J(15N,1H) <1.5 Hz], which is opposite to that used by other authors, confirms the assignment extended to BHXA by Brown and co‐workers from the spectra of acetohydroxamic acid. The enrichment allowed also assignment of the 29Si lines in the spectra of disilylated benzohydroxamic acid, (Z)‐tert‐butyldimethylsilyl N‐tert‐butyldimethylsilyloxybenzoimidate (2) and (Z)‐tert‐butyldiphenylsilyl N‐tert‐butyldiphenylsilyloxybenzoimidate (3), and confirmed structure of the monosilylated products, N‐tert‐butyldiphenylsilyloxybenzamide (4) and N‐tert‐butyldiphenylsilyloxy benzoimidic acid (5). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
993.
由于腔模与激子对压力的依赖关系不同,所以可以选择不同的压力使激子和光场处于不同的耦合状态,从而实现对耦合的调谐。利用这种办法,我们观测到了代表激子与光场强耦合作用的Rabi分裂。由于在我们现有样品结构中压力对激子本征行为的影响很小,与以前报道的温度、电场等调谐方式相比,这种调谐方法不仅可以有效地调谐半导体微腔内激子与腔模的耦合程度,而且能够保持激子的本征性质在整个调谐过程中基本不变。这有助于研究在强耦合过程中激子极化激元的本征性质。将实验结果与压力下激子与腔模耦合理论进行拟合,得出了正确的Rabi分裂值。 相似文献
994.
Ya.G. Groda P. Argyrakis G.S. Bokun V.S. Vikhrenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):527-535
The selfconsistent diagram approximation (SCDA) is generalized for three-dimensional lattice gases with nearest neighbor repulsive
interactions. The free energy is represented in a closed form through elementary functions. Thermodynamical (phase diagrams,
chemical potential and mean square fluctuations), structural (order parameter, distribution functions) as well as diffusional
characteristics are investigated. The calculation results are compared with the Monte Carlo simulation data to demonstrate
high precision of the SCDA in reproducing the equilibrium lattice gas characteristics. It is shown that similarly to two-dimensional
systems the specific statistical memory effects strongly influence the lattice gas diffusion in the ordered states.
Received 7 August 2002 / Received in final form 22 January 2003 Published online 24 April 2003 相似文献
995.
M. R. Setare 《International Journal of Theoretical Physics》2004,43(11):2237-2242
We compute particle creation for a real massive scalar field conformally coupled to a spatially closed Robertson–Walker space-time background, with time-dependent scale factor. This is a dynamical Casimir effect with moving boundaries. 相似文献
996.
激发对相干态的等阶Y压缩效应 总被引:16,自引:0,他引:16
用数值计算法研究了激发对相干态|ζ;m〉=a+mb+m|ζ〉的等阶Y压缩效应.结果表明:对于态a+mb+m|ζ〉,光场存在着等阶K(=2,3,4,5,…)次方Y压缩效应,但是随着场模上光子增加数m的增大,等阶K次方Y压缩效应减弱. 相似文献
997.
We use methods of nonequilibrium statistical thermodynamics to investigate two dissipative processes in solids. We find the electron energy losses of a particle moving in a planar channeling regime and the sound absorption coefficient in metals under electron impurity scattering. The oscillator model is used to analyze the contribution from the effect of electron entrainment by a moving scattering center to the total dissipated energy. We investigate the frequency and temperature dependence of energy losses and also the dependence of the absorption coefficient on the sound wave vector. 相似文献
998.
Phenethylammonium-based perovskites, which can be regarded as a semiconductor/insulator multiple quantum well consisting of lead halide semiconductor layers sandwiched between phenethylammonium insulator layers were prepared. To investigate the effects of the electronic state and the orientation of organic insulator layers on the optical properties of layered perovskites, fluorine substituted analogues were also prepared. The structure and optical properties were investigated by the XRD, UV–Vis absorption, and fluorescence measurements. The exciton absorption peak was shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms. 相似文献
999.
1000.
Jungho Yoon 《Applied mathematics and computation》2004,150(3):875-887
In this paper, we consider approximation to derivatives of a function by using radial basis function interpolation. Most of well-known theories for this problem provide error analysis in terms of the so-called native space, say Cφ. However, if a basis function φ is smooth, the space Cφ is extremely small. Thus, the purpose of this study is to extend this result to functions in the homogenous Sobolev space. 相似文献