全文获取类型
收费全文 | 3869篇 |
免费 | 701篇 |
国内免费 | 519篇 |
专业分类
化学 | 2596篇 |
晶体学 | 66篇 |
力学 | 260篇 |
综合类 | 23篇 |
数学 | 582篇 |
物理学 | 1562篇 |
出版年
2024年 | 12篇 |
2023年 | 91篇 |
2022年 | 137篇 |
2021年 | 161篇 |
2020年 | 184篇 |
2019年 | 149篇 |
2018年 | 169篇 |
2017年 | 181篇 |
2016年 | 181篇 |
2015年 | 185篇 |
2014年 | 224篇 |
2013年 | 295篇 |
2012年 | 339篇 |
2011年 | 357篇 |
2010年 | 225篇 |
2009年 | 261篇 |
2008年 | 262篇 |
2007年 | 221篇 |
2006年 | 256篇 |
2005年 | 181篇 |
2004年 | 119篇 |
2003年 | 106篇 |
2002年 | 104篇 |
2001年 | 86篇 |
2000年 | 71篇 |
1999年 | 76篇 |
1998年 | 68篇 |
1997年 | 51篇 |
1996年 | 61篇 |
1995年 | 38篇 |
1994年 | 39篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1957年 | 2篇 |
1929年 | 2篇 |
1926年 | 2篇 |
排序方式: 共有5089条查询结果,搜索用时 15 毫秒
1.
The research progress of a novel traffic solution,a submerged floating tunnel(SFT),is reviewed in terms of a study approach and loading scenario.Among existing publications,the buoyancy-weight ratio(BWR) is usually predefined.However,BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable system.In the context of a SFT prototype(SFTP) project in Qiandao Lake(Zhejiang Province,China),the importance of BWR is illustrated by finite element analysis and subsequently,an optimized BWR is proposed within a reasonable range in the present study.In the numerical model,structural damping is identified to be of importance.Rayleigh damping and the corresponding Rayleigh coefficients are attained through a sensitivity study,which shows that the adopted damping ratios are fairly suitable for SFTP.Lastly,the human sense of security is considered by quantifying the comfort index,which helps further optimize BWR in the SFTP structural parameter design. 相似文献
2.
3.
4.
A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented
within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical
properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with
time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available. 相似文献
5.
6.
We derive the Friedmann-like equations in braneworld cosmology by imposing the first law of thermodynamics and Bekenstein's area-entropy formula on the apparent horizon of a Friedmann–Robertson–Walker universe in both Randall–Sundrum II gravity and Dvali–Gabadadze–Porrati gravity models. Israel's boundary condition plays an important role in our calculations in both cases, besides the first law of thermodynamics and Bekenstein's area-entropy formula. The results indicate that thermodynamics on the brane world knows the behaviors of gravity. 相似文献
7.
8.
The Existence of Solutions to Sturm-Liouville Boundary Value Problems with Laplacian-like Operator 总被引:2,自引:0,他引:2
Wei-ping Sun Wei-gao GeDepartment of Applied Mathematics Beijing Institute of Technology Beijing China 《应用数学学报(英文版)》2002,18(2):341-348
Abstract The existence of infinitely many solutions to Sturm-Liouville boundary value problem with aLaplacian-like operator is studied by applying generalized polar coordinates. 相似文献
9.
The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed. 相似文献
10.
Dirichlet boundary value problems for perturbed second-order differential equations on a half line are investigated in this paper. The methods mainly depend on the calculus of variations to the classical functionals. Sufficient conditions are obtained for the existence of the solutions. 相似文献