全文获取类型
收费全文 | 43012篇 |
免费 | 5414篇 |
国内免费 | 2594篇 |
专业分类
化学 | 10412篇 |
晶体学 | 182篇 |
力学 | 10934篇 |
综合类 | 586篇 |
数学 | 13567篇 |
物理学 | 15339篇 |
出版年
2024年 | 47篇 |
2023年 | 413篇 |
2022年 | 728篇 |
2021年 | 1063篇 |
2020年 | 1351篇 |
2019年 | 1105篇 |
2018年 | 1077篇 |
2017年 | 1381篇 |
2016年 | 1710篇 |
2015年 | 1423篇 |
2014年 | 2099篇 |
2013年 | 3307篇 |
2012年 | 2404篇 |
2011年 | 2874篇 |
2010年 | 2314篇 |
2009年 | 2824篇 |
2008年 | 2643篇 |
2007年 | 2625篇 |
2006年 | 2279篇 |
2005年 | 1989篇 |
2004年 | 1931篇 |
2003年 | 1674篇 |
2002年 | 1506篇 |
2001年 | 1147篇 |
2000年 | 1116篇 |
1999年 | 995篇 |
1998年 | 917篇 |
1997年 | 798篇 |
1996年 | 670篇 |
1995年 | 619篇 |
1994年 | 560篇 |
1993年 | 477篇 |
1992年 | 458篇 |
1991年 | 342篇 |
1990年 | 302篇 |
1989年 | 229篇 |
1988年 | 222篇 |
1987年 | 202篇 |
1986年 | 184篇 |
1985年 | 202篇 |
1984年 | 194篇 |
1983年 | 104篇 |
1982年 | 166篇 |
1981年 | 83篇 |
1980年 | 45篇 |
1979年 | 45篇 |
1978年 | 36篇 |
1977年 | 30篇 |
1976年 | 20篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
L. E. Payne P. W. Schaefer J. C. Song 《Mathematical Methods in the Applied Sciences》2004,27(17):2045-2053
Energy bounds are derived for Dirichlet type boundary value problems for the Navier–Stokes and Stokes equations when a combination of the solution values initially and at a later time is prescribed. The bounds are obtained by means of a differential inequality and imply uniqueness and continuous data dependence of the solutions for a range of values of the parameter in the non‐standard auxiliary condition. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
152.
Jérôme Le NôtreAna Acosta Martinez Pierre H DixneufChristian Bruneau 《Tetrahedron》2003,59(47):9425-9432
Enyne rearrangement of silylated modified terpenoids has been used as the key step for the synthesis of new terpenes and terpenoids. The catalytic system generated in situ from [RuCl2(p-cymene]2, 1,3-bis(mesityl)imidazolinium chloride and cesium carbonate is able to perform the transformation of silylated 1,7-enynes into cyclic siloxanes. Selective cleavage of the silicon-carbon and silicon-oxygen bonds by simple reactions has been performed to afford new terpenes and terpenoids by formal addition of a C5 unit. 相似文献
153.
Wang Renhong Zhou Heng 《分析论及其应用》2003,19(3)
1 IntroductionLet Sd- 1 bethe unitsphere of Rd,Πdthe space of allpolynomialsofd variables,and x(i)= (x1 ,… ,xi) (i=1 ,… ,d) .In this paper,we are concerned with the homogeneous polyno-mials orthogonal with the weightfunction h(x(d) ) =x2 k11 …x2 kdd on Sd- 1 ,where ki≥ 0 (i=1 ,… ,d) .Connected with the weightfunction h(x(d) ) are the following differential-differenceoperators introduced by Charles F. Dunkl in [3 ] ,Dip(x(d) ) = p(x(d) ) xi+ di=1kip(x(d) ) -p(x1 ,… ,-xi,… ,xd)xi,Δ… 相似文献
154.
工程施工中运输网络优化方案 总被引:5,自引:0,他引:5
施工工地运输方案的优化设计可以归结为 :按施工期要求设计运输线路或验证已有线路通行能力 ,计算总线路中影响提高流量的关键路段 ,取得最小费用最大流 .本文运用图论理论这一数学工具把实际问题抽象为有向网络 ,进而建立数学模型 .此方法理论上严密 ,解题步聚直观清晰 ,对水利、公路、水路、铁路等其它运输系统有普遍意义 . 相似文献
155.
The electromagnetic (EM) energy flow near single spheres is investigated by applying Mie theory. From the patterns of the energy flow, the absorption and the scattering of light can be understood in the microscopic point of view. In the absorption profiles of metallic particles, most absorbed energy is consumed on the surface of the particles, which indicates that the resonance of surface plasmon is different from that of the bulk plasmon. Two mechanisms to enhanced local EM field are also distinguished. One is the surface plasmon resonance, and another one is the intensified energy flow. 相似文献
156.
157.
158.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
159.
Biswarup Mukhopadhyaya 《Pramana》1998,51(1-2):181-190
The observable consequences of gauge-mediated supersymmetry breaking (GMSB) are reviewed here. Implications of scenarios both
with a neutralino and a slepton as the next lightest supersymmetric particle (NLSP) are surveyed in relation to hadronic ande
+
e
- colliders. We also discuss the phenomenological consequences of the NLSP decaying slowly, giving rise to delayed events in
the detectors.The importance of distinguishing signals of GMSB models from those of the commonly discussed supergravity-type
theories is emphasized. 相似文献
160.
Mass distributions of fragments in the low-energy fission of nuclei from 187Ir to 213At have been analysed. This analysis has shown that shell effects in symmetric-mode fragment mass yields from the fission of pre-actinide nuclei could be described if one assumes the existence of two strongly deformed neutron shells in the arising fragments with neutron numbers N1 ≈ 52 and N2 ≈ 68. A new method has been proposed for quantitatively describing the mass distributions of the symmetric fission mode for pre-actinides with A ≈ 180–220. 相似文献