全文获取类型
收费全文 | 3922篇 |
免费 | 672篇 |
国内免费 | 521篇 |
专业分类
化学 | 2609篇 |
晶体学 | 66篇 |
力学 | 261篇 |
综合类 | 23篇 |
数学 | 587篇 |
物理学 | 1569篇 |
出版年
2024年 | 12篇 |
2023年 | 91篇 |
2022年 | 138篇 |
2021年 | 171篇 |
2020年 | 185篇 |
2019年 | 149篇 |
2018年 | 172篇 |
2017年 | 182篇 |
2016年 | 181篇 |
2015年 | 185篇 |
2014年 | 224篇 |
2013年 | 295篇 |
2012年 | 339篇 |
2011年 | 358篇 |
2010年 | 226篇 |
2009年 | 262篇 |
2008年 | 262篇 |
2007年 | 221篇 |
2006年 | 257篇 |
2005年 | 184篇 |
2004年 | 120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 | 40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 | 6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5115条查询结果,搜索用时 15 毫秒
991.
In this work, we consider the following second-order m-point boundary value problem on time scales $$\left\{\begin{array}{@{}l}(\phi_{p}(u^{\triangle}(t)))^{\nabla}+h(t)f(t,u(t),u^{\triangle }(t))=0,\quad t\in(0,+\infty)_{\mathbb{T}},\\[4pt]\displaystyle u(0)=\sum_{i=1}^{m-2}\alpha_{i}u(\eta_{i}),\qquad u^{\triangle}(+\infty)=\sum_{i=1}^{m-2}\beta_{i}u^{\triangle}(\eta_{i}).\end{array}\right.$$ We establish new criteria for the existence of at least three unbounded positive solutions. Our results are new even for the corresponding differential $({\mathbb{T}}={\mathbb{R}})$ , difference equation $({\mathbb{T}}={\mathbb{Z}})$ and for the general time-scale setting. An example is given to illustrate our results. 相似文献
992.
The notion of mixed quermassintegrals in the classical Brunn-Minkowski theory is extended to that of Orlicz mixed quermassintegrals in the Orlicz Brunn-Minkowski theory. The analogs of the classical Cauchy-Kubota formula, the Minkowski isoperimetric inequality and the Brunn-Minkowski inequality are established for this new Orlicz mixed quermassintegrals. 相似文献
993.
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
994.
By means of the Leggett-Williams fixed-point theorem, criteria are developed for the existence of at least three positive solutions to the one-dimensional p-Laplacian boundary value problem, ((y′))′ + g(t)f(t,y) = 0, y(0) - B0(y′(0)) = 0, y(1) + B1(y′(1)) = 0, where (v) |v|p−2v, p > 1. 相似文献
995.
On free entropy dimension of finite von Neumann algebras 总被引:3,自引:0,他引:3
996.
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
997.
The singularly perturbed problem for the semilinear elliptic equations is considered. Under appropriate conditions, by using the comparison theorem, the existence and asymptotic behavior of solution for the boundary value problems are studied. 相似文献
998.
通过城市竞争力的比较与分析,可以找出促进城市快速发展的突破口以及进一步提升城市竞争力的对策和策略.从已有的多家评价指标体系出发,选取反映静态维度的7个方面32个指标以及动态维度的4个方面共38个原始指标或生成统计指标,组成城市竞争力评价指标体系.采用主成分分析方法,对从地理位置和区域发展角度均具有代表性的大连、青岛、厦门3城市与宁波进行了单项和总量排序,并进行竞争力的比较分析,最后,就宁波市城市竞争力的提升提出了对策建议. 相似文献
999.
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
1000.