全文获取类型
收费全文 | 100820篇 |
免费 | 4071篇 |
国内免费 | 2983篇 |
专业分类
化学 | 40327篇 |
晶体学 | 1060篇 |
力学 | 8039篇 |
综合类 | 239篇 |
数学 | 34334篇 |
物理学 | 23875篇 |
出版年
2024年 | 78篇 |
2023年 | 504篇 |
2022年 | 818篇 |
2021年 | 861篇 |
2020年 | 984篇 |
2019年 | 905篇 |
2018年 | 10989篇 |
2017年 | 10794篇 |
2016年 | 7034篇 |
2015年 | 1852篇 |
2014年 | 1569篇 |
2013年 | 1963篇 |
2012年 | 5790篇 |
2011年 | 12408篇 |
2010年 | 6956篇 |
2009年 | 7299篇 |
2008年 | 8009篇 |
2007年 | 10029篇 |
2006年 | 1536篇 |
2005年 | 2352篇 |
2004年 | 2357篇 |
2003年 | 2659篇 |
2002年 | 1607篇 |
2001年 | 754篇 |
2000年 | 795篇 |
1999年 | 739篇 |
1998年 | 674篇 |
1997年 | 570篇 |
1996年 | 629篇 |
1995年 | 501篇 |
1994年 | 431篇 |
1993年 | 417篇 |
1992年 | 321篇 |
1991年 | 291篇 |
1990年 | 284篇 |
1989年 | 217篇 |
1988年 | 177篇 |
1987年 | 141篇 |
1986年 | 154篇 |
1985年 | 111篇 |
1984年 | 79篇 |
1983年 | 75篇 |
1982年 | 78篇 |
1981年 | 59篇 |
1980年 | 54篇 |
1979年 | 50篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Harish C. Bahl Stanley Zionts 《The Journal of the Operational Research Society》1987,38(12):1141-1148
Scheduling the production of several items requires the determination of production quantities in different periods in the presence of resource constraints. Several approximate and heuristic algorithms have been proposed to solve this problem. However, no method for finding an optimal solution has as yet been developed. It is shown that the problem may be solved advantageously using Benders' decomposition. The subproblem in Benders' decomposition is shown to be a transportation problem, and some strategies for solving the master problem are indicated. The paper concludes with a sample problem demonstrating the application of the method. 相似文献
82.
Rie Natsui 《Acta Mathematica Hungarica》2005,108(4):299-318
Summary Let Fq be a finite field with q elements. We consider formal Laurent series of Fq -coefficients with their continued fraction expansions by Fq -polynomials. We prove some arithmetic properties for almost every formal Laurent series with respect to the Haar measure. We construct a group extension of the non-archimedean continued fraction transformation and show its ergodicity. Then we get some results as an application of the individual ergodic theorem. We also discuss the convergence rate for limit behaviors. 相似文献
83.
Zhu Linsheng 《东北数学》1998,(1)
in this paper, the classification and realization of complete Lie algebras withcommutative nilpotent radicals are given. From this, some results on the radicals of thesecomplete Lie algebras are obtained. 相似文献
84.
Dorina Mitrea Marius Mitrea Jill Pipher 《Journal of Fourier Analysis and Applications》1997,3(2):131-192
We study boundary value problems for the time-harmonic form of the Maxwell equations, as well as for other related systems
of equations, on arbitrary Lipschitz domains in the three-dimensional Euclidean space. The main goal is to develop the corresponding
theory for Lp-integrable bounday data for optimal values of p's. We also discuss a number of relevant applications in electromagnetic scattering. 相似文献
85.
86.
Operational Research groups were established in private and public sector organizations following on from their success supporting the military in the Second World War. In the early years their numbers grew rapidly but by the mid-1970s evidence started to accumulate that they were being viewed less favourably. Many organizations chose not to set up OR groups. Established groups were closed down or dispersed to operating units in organizations, particularly during the recessionary periods. In 1993 following on the closures of some major OR groups in the UK, the Operational Research Society decided to fund research to examine those factors influencing a group's success and survival. This review, which forms part of the research, first examines the history of OR groups in the UK and North America, arguing that in practice they were one of a number of internal organizational consultancies. As such they were judged by their competitive performance. Despite the intent of the founding fathers of OR many groups found their scope was limited to mainly tactical problems using analytical model based approaches although there were exceptions that were successful in making major contributions at the strategic level also. Within their chosen fields of activity however many groups flourished whilst some failed. This review presents a comprehensive list of influences on success and survival. They include changes in the external environment, together with shifts in managerial style and culture, organizational factors, and the OR group itself. The review concludes that, while OR groups can do much to protect themselves from closure, organizational changes within a hostile managerial culture demand a creative response that acknowledges new requirements. Areas where an OR group has greatest influence over its effectiveness include its leadership and personnel, project balance and management. In addition, to be successful OR groups need to positively develop and market their services in an increasingly competitive managerial climate. 相似文献
87.
Banach空间上的框架与Riesz基 总被引:5,自引:0,他引:5
本文讨论Banach空间上框架、无冗框架与Riesz基之间的关系及它们的稳定性. 相似文献
88.
用相位调制方法测量光盘盘基应力双折射的精度分析 总被引:4,自引:2,他引:2
偏振相位调制方法是测量微小双折射的一种高精度检测方法。本文系统全面地分析了以PMCSA结构形式测量光盘盘基应力双折射的相位调制方法中,由各种误差源造成的对测试结果的影响。 相似文献
89.
A numerical study of confined jets in a cylindrical duct is carried out to examine the performance of two recently proposed turbulence models: an RNG-based K-? model and a realizable Reynolds stress algebraic equation model. The former is of the same form as the standard K-? model but has different model coefficients. The latter uses an explicit quadratic stress-strain relationship to model the turbulent stresses and is capable of ensuring the positivity of each turbulent normal stress. The flow considered involves recirculation with unfixed separation and reatachment points and severe adverse pressure gradients, thereby providing a valuable test of the predictive capability of the models for complex flows. Calculations are performed with a finite volume procedure. Numerical credibility of the solutions is ensured by using second-order-accurate differencing schemes and sufficiently fine grids. Calculations with the standard K-? model are also made for comparison. Detailed comparisons with experiments show that the realizable Reynolds stress algebraic equation model consistently works better than does the standard K-? model in capturing the essential flow features, while the RNG-based K-? model does not seem to give improvements over the standard K-? model under the flow conditions considered. 相似文献
90.