全文获取类型
收费全文 | 9775篇 |
免费 | 1225篇 |
国内免费 | 1462篇 |
专业分类
化学 | 6095篇 |
晶体学 | 90篇 |
力学 | 1507篇 |
综合类 | 63篇 |
数学 | 513篇 |
物理学 | 4194篇 |
出版年
2024年 | 33篇 |
2023年 | 161篇 |
2022年 | 281篇 |
2021年 | 305篇 |
2020年 | 393篇 |
2019年 | 329篇 |
2018年 | 299篇 |
2017年 | 397篇 |
2016年 | 413篇 |
2015年 | 392篇 |
2014年 | 513篇 |
2013年 | 788篇 |
2012年 | 606篇 |
2011年 | 684篇 |
2010年 | 513篇 |
2009年 | 600篇 |
2008年 | 568篇 |
2007年 | 620篇 |
2006年 | 508篇 |
2005年 | 513篇 |
2004年 | 444篇 |
2003年 | 373篇 |
2002年 | 337篇 |
2001年 | 335篇 |
2000年 | 267篇 |
1999年 | 250篇 |
1998年 | 218篇 |
1997年 | 178篇 |
1996年 | 156篇 |
1995年 | 156篇 |
1994年 | 129篇 |
1993年 | 96篇 |
1992年 | 82篇 |
1991年 | 74篇 |
1990年 | 65篇 |
1989年 | 42篇 |
1988年 | 51篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 32篇 |
1984年 | 32篇 |
1983年 | 12篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1977年 | 22篇 |
1976年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
用三维样边界元法分析水闸闸室结构。底板,闸墩和载水墙等为其子结构,交通桥,工作桥和胸墙等处理为内部支撑。地基和边载可以是任意的,只要能给定地表位移面力关系。在各种工况下,不论是设置平板门还是弧形门,是平底板是反拱底板,即使在稀疏剖分下也能给出高精度的位移场,应力场和地基反力场。 相似文献
32.
Final state interaction effects inpp→ pΛK
+ andpd →3Heη reactions are explored near threshold to study the sensitivity of the cross-sections to thepΛ potential and theηN scattering matrix. The final state scattering wave functions between Λ andp andη and3He are described rigorously. The Λ production is described by the exchange of one pion and aK-meson between two protons in the incident channel. Theη production is described by a two-step model, where in the first step a pion is produced. This pion then produces anη by interacting with another nucleon 相似文献
33.
E. F. Kvashina 《Russian Chemical Bulletin》1994,43(12):2121-2121
The interaction of ditoluenetitanium with CO{in2} has been studied. Based on hydrolysis, thermolysis, and IR spectral data, the conclusion is drawn that a low-valent titanium oxalate is formed.This study was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5538).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2241–2242, December, 1994. 相似文献
34.
35.
36.
通过考虑同类核子相干对间的四极相互作用,在IBM2中对Ce偶-偶同位素^128Ce-^138Ce的低激发态能谱和E2跃迁几率及分支比进行了理论分析,计算结果有效地改善了IBM中这些核的γ带能谱的Staggering现象描述,与实验观察到的低激发态结果基本一致。 相似文献
37.
讨论了结构与饱和土壤相互作用的固结分析问题.对于结构利用多重子结构分析技术实现向饱和土交界面上的凝聚.从而建立了结构与饱和土壤相互作用的固结控制方程.文中给出了问题求解的一次性算法方案,采取压力主从关系的手段处理边界上的不排水条件.文末给出数值算例.本文工作为大型结构与土体相互作用固结分析研究工作的深入创造了条件. 相似文献
38.
提出了一种利用简并Ⅴ型三能级原子与相干态光场(大失谐条件下)Raman相互作用实现类自旋的腔场Greenberger-Home-Zeilinger(即GHZ)态的新方案。 相似文献
39.
An algorithm for a time accurate incompressible Navier–Stokes solver on an unstructured grid is presented. The algorithm uses a second order, three‐point, backward difference formula for the physical time marching. For each time step, a divergence free flow field is obtained based on an artificial compressibility method. An implicit method with a local time step is used to accelerate the convergence for the pseudotime iteration. To validate the code, an unsteady laminar flow over a circular cylinder at a Reynolds number of 200 is calculated. The results are compared with available experimental and numerical data and good agreements are achieved. Using the developed unsteady code, an interaction of a Karman vortex street with an elliptical leading edge is simulated. The incident Karman vortex street is generated by a circular cylinder located upstream. A clustering to the path of the vortices is achieved easily due to flexibility of an unstructured grid. Details of the interaction mechanism are analysed by investigating evolutions of vortices. Characteristics of the interactions are compared for large‐ and small‐scale vortex streets. Different patterns of the interaction are observed for those two vortex streets and the observation is in agreement with experiment. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
40.
In order to study cross flow induced vibration of heat exchanger tube bundles, a new fluid–structure interaction model based on surface vorticity method is proposed. With this model, the vibration of a flexible cylinder is simulated at Re=2.67 × 104, the computational results of the cylinder response, the fluid force, the vibration frequency, and the vorticity map are presented. The numerical results reproduce the amplitude‐limiting and non‐linear (lock‐in) characteristics of flow‐induced vibration. The maximum vibration amplitude as well as its corresponding lock‐in frequency is in good agreement with experimental results. The amplitude of vibration can be as high as 0.88D for the case investigated. As vibration amplitude increases, the amplitude of the lift force also increases. With enhancement of vibration amplitude, the vortex pattern in the near wake changes significantly. This fluid–structure interaction model is further applied to simulate flow‐induced vibration of two tandem cylinders and two side‐by‐side cylinders at similar Reynolds number. Promising and reasonable results and predictions are obtained. It is hopeful that with this relatively simple and computer time saving method, flow induced vibration of a large number of flexible tube bundles can be successfully simulated. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献