全文获取类型
收费全文 | 9136篇 |
免费 | 865篇 |
国内免费 | 782篇 |
专业分类
化学 | 3397篇 |
晶体学 | 69篇 |
力学 | 2835篇 |
综合类 | 95篇 |
数学 | 2464篇 |
物理学 | 1923篇 |
出版年
2024年 | 12篇 |
2023年 | 99篇 |
2022年 | 127篇 |
2021年 | 172篇 |
2020年 | 227篇 |
2019年 | 200篇 |
2018年 | 209篇 |
2017年 | 285篇 |
2016年 | 307篇 |
2015年 | 258篇 |
2014年 | 392篇 |
2013年 | 648篇 |
2012年 | 489篇 |
2011年 | 543篇 |
2010年 | 432篇 |
2009年 | 533篇 |
2008年 | 487篇 |
2007年 | 509篇 |
2006年 | 445篇 |
2005年 | 508篇 |
2004年 | 417篇 |
2003年 | 403篇 |
2002年 | 360篇 |
2001年 | 284篇 |
2000年 | 264篇 |
1999年 | 253篇 |
1998年 | 220篇 |
1997年 | 226篇 |
1996年 | 154篇 |
1995年 | 183篇 |
1994年 | 145篇 |
1993年 | 125篇 |
1992年 | 94篇 |
1991年 | 108篇 |
1990年 | 80篇 |
1989年 | 60篇 |
1988年 | 85篇 |
1987年 | 74篇 |
1986年 | 78篇 |
1985年 | 56篇 |
1984年 | 43篇 |
1983年 | 18篇 |
1982年 | 57篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+. 相似文献
62.
带有无限到达源的Re-entrant Line的稳定性 总被引:1,自引:0,他引:1
用Foster判别准则,Weiss[13]给出了带有无限到达源的两站三步re-entrant line的稳定性的充分条件.本文用两种不同的方法得到了其稳定性的充分必要条件,即: 二维随机游动方法和Foster判别准则.同时,我们又用流体模型方法得到了系统稳定的充分条件,大大地简化了Weiss[13]的证明. 相似文献
63.
Zhangxin Chen 《Numerical Methods for Partial Differential Equations》2002,18(2):203-217
In this article we prove uniform convergence estimates for the recently developed Galerkin‐multigrid methods for nonconforming finite elements for second‐order problems with less than full elliptic regularity. These multigrid methods are defined in terms of the “Galerkin approach,” where quadratic forms over coarse grids are constructed using the quadratic form on the finest grid and iterated coarse‐to‐fine intergrid transfer operators. Previously, uniform estimates were obtained for problems with full elliptic regularity, whereas these estimates are derived with less than full elliptic regularity here. Applications to the nonconforming P1, rotated Q1, and Wilson finite elements are analyzed. The result applies to the mixed method based on finite elements that are equivalent to these nonconforming elements. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 203–217, 2002; DOI 10.1002/num.10004 相似文献
64.
泊松类型方程边界元解法 总被引:2,自引:0,他引:2
本文采用高阶拉普拉斯算子基本解将泊松类型方程的区域积分全部变换成边界积分,使计算问题的维数减少一维.通过斯托克斯方程的算例,表明本文所用的方法是有效的方法。 相似文献
65.
66.
Philippe Quevauviller Rob Ritsema Roberto Morabito Wilfried M. R. Dirkx Salvatore Chiavarini Jos M. Bayona Olivier F. X. Donard 《应用有机金属化学》1994,8(6):541-549
Biogeochemical pathways of tin species in the environment are still controversial, e.g. with regard to methylation and transmethylation phenomena, owing to the fact that the identification of methylated tin-compounds is often difficult. The previous tentative identification of a mixed methylbutyltin compound in sediment and biological samples by GC/AAS after hydride generation gave an illustration of this problem. This compound was previously identified in sediments by other authors and also suspected to occur in a contaminated sediment sample from the Boyardville Marina, France. The retention time obtained by GC/AAS corresponded to the actual retention time of a mixed methylbutyltin calibrant. However, additional checks demonstrated that the compound detected was actually monophenyltin. This evidence was produced by a thorough analysis of a selected sediment sample by alternative techniques such as GC/AAS and GC/AES after pentylation, GC/FPD and GC/MS. The results presented highlight the need for a full identification of compounds to avoid mis-interpretation. 相似文献
67.
In this paper we outline a new particle-mesh method for rapidly rotating shallow water flows based on a set of regularized equations of motion. The time-stepping method uses an operator splitting of the equations into an Eulerian gravity wave part and a Lagrangian advection part. An essential ingredient is the advection of absolute vorticity by means of translated radial basis functions. We show that this implies exact conservation of enstrophy. The method is tested on two model problems based on the qualitative features of the solutions obtained (i.e., dispersion or smoothness of potential vorticity contours) as well as on the increase in mean divergence level. 相似文献
68.
W. Korneta 《Czechoslovak Journal of Physics》2002,52(2):313-316
The topological and geometrical properties of Voronoi cells generated for 2D fluid of hard disks with Ising-like spins near the second-order phase transition from the paramagnetic to ferromagnetic phase are described for different disk densities. The comparison with Voronoi cells generated for the random hard disk system is given. 相似文献
69.
This paper reports a combined experimental and numerical investigation of three-dimensional steady turbulent flows in inlet manifolds of square cross-section. Predictions and measurements of the flows were carried out using computational fluid dynamics and laser Doppler anemometry techniques respectively. The flow structure was characterized in detail and the effects of flow split ratio and inlet flow rate were studied. These were found to cause significant variations in the size and shape of recirculation regions in the branches, and in the turbulence levels. It was then found that there is a significant difference between the flow rates through different branches. The performance of the code was assessed through a comparison between predictions and measurements. The comparison demonstrates that all important features of the flow are well represented by the predictions. 相似文献
70.