全文获取类型
收费全文 | 150992篇 |
免费 | 2245篇 |
国内免费 | 673篇 |
专业分类
化学 | 86014篇 |
晶体学 | 2156篇 |
力学 | 5567篇 |
综合类 | 6篇 |
数学 | 17311篇 |
物理学 | 42856篇 |
出版年
2016年 | 1830篇 |
2015年 | 1555篇 |
2014年 | 1929篇 |
2013年 | 6093篇 |
2012年 | 4653篇 |
2011年 | 5935篇 |
2010年 | 3624篇 |
2009年 | 3278篇 |
2008年 | 5282篇 |
2007年 | 5322篇 |
2006年 | 5442篇 |
2005年 | 5239篇 |
2004年 | 4682篇 |
2003年 | 4153篇 |
2002年 | 4014篇 |
2001年 | 4006篇 |
2000年 | 3050篇 |
1999年 | 2558篇 |
1998年 | 2235篇 |
1997年 | 2279篇 |
1996年 | 2178篇 |
1995年 | 2105篇 |
1994年 | 1912篇 |
1993年 | 1863篇 |
1992年 | 2045篇 |
1991年 | 2045篇 |
1990年 | 1938篇 |
1989年 | 1946篇 |
1988年 | 1928篇 |
1987年 | 1878篇 |
1986年 | 1815篇 |
1985年 | 2460篇 |
1984年 | 2605篇 |
1983年 | 2190篇 |
1982年 | 2546篇 |
1981年 | 2320篇 |
1980年 | 2384篇 |
1979年 | 2317篇 |
1978年 | 2466篇 |
1977年 | 2357篇 |
1976年 | 2324篇 |
1975年 | 2237篇 |
1974年 | 2076篇 |
1973年 | 2260篇 |
1972年 | 1385篇 |
1971年 | 1063篇 |
1970年 | 1003篇 |
1969年 | 980篇 |
1968年 | 1096篇 |
1967年 | 1147篇 |
排序方式: 共有10000条查询结果,搜索用时 257 毫秒
991.
H.O.U. Fynbo Y. Prezado J. Äystö U.C. Bergmann M.J.G. Borge P. Dendooven W. Huang J. Huikari H. Jeppesen P. Jones B. Jonson M. Meister G. Nyman M. Oinonen K. Riisager O. Tengblad I.S. Vogelius Y. Wang L. Weissman K.W. Rolander 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):135-138
992.
This paper describes a methodology for allocating resources in hospitals. The methodology uses two linear goal-programming models. One model sets case mix and volume for physicians, while holding service costs fixed; the other translates case mix decisions into a commensurate set of practice changes for physicians. The models allow decision makers to set case mix and case costs in such a way that the institution is able to break even, while preserving physician income and minimizing disturbance to practice. The models also permit investigation of trade-offs between case mix and physician practice parameters. Results are presented from a decision-making scenario facing the surgical division of Toronto's Mount Sinai Hospital after the announcement of a 3-year, 18% reduction in funding. 相似文献
993.
N.P. Somasiri W.K. Toh X. Chen I.D. Robertson A.A. Rezazadeh 《International Journal of Infrared and Millimeter Waves》2002,23(12):1777-1785
This paper describes numerical modelling of a dual band multi-layered microstrip patch antenna operating at 35GHz on an in-house semi-insulating GaAs substrate. The simulated and measured resonant frequencies at both lower and upper resonant frequencies will be compared to check the accuracy of the different numerical modelling techniques. 相似文献
994.
Peter A. Markowich Gerhard Rein Gershon Wolansky 《Journal of statistical physics》2002,106(5-6):1221-1239
We consider the Schrödinger–Poisson system in the repulsive (plasma physics) Coulomb case. Given a stationary state from a certain class we prove its nonlinear stability, using an appropriately defined energy-Casimir functional as Lyapunov function. To obtain such states we start with a given Casimir functional and construct a new functional which is in some sense dual to the corresponding energy-Casimir functional. This dual functional has a unique maximizer which is a stationary state of the Schrödinger–Poisson system and lies in the stability class. The stationary states are parameterized by the equation of state, giving the occupation probabilities of the quantum states as a strictly decreasing function of their energy levels. 相似文献
995.
996.
Tevian Dray Corinne A. Manogue Robin W. Tucker 《General Relativity and Gravitation》1991,23(8):967-971
We consider the (massless) scalar field on 2-dimensional manifolds whose metric changes signature and which admit a spacelike isometry. Choosing the wave equation so that there will be a conserved Klein-Gordon product implicitly determines the junction conditions one needs to impose in order to obtain global solutions. The resulting mix of positive and negative frequencies produced by the presence of Euclidean regions depends only on the total width of the regions, and not on the detailed form of the metric.This essay received honorable mention in the 1991 competition of the Gravity Research Foundation. 相似文献
997.
998.
Gerald W. Evans Robert Fairbairn 《The Journal of the Operational Research Society》1989,40(11):971-981
A 0-1 integer linear programme for the selection and scheduling of US National Aeronautics and Space Administration (NASA) missions over a long planning horizon is presented. This model was formulated to allow a higher-level user-interaction with an advanced missions database currently being developed. The model implicitly considers the multi-objective nature of the problem, which results from the desire to maximize benefits in several categories as well as from the desire to minimize cost. In addition, the model allows the planner much flexibility in the selection process. This is accomplished by allowing the planner the ability to specify long- or short-term budget constraints, precursor/follow-on mission requirements, or any number of other idiosyncratic constraints which might be of importance in the decision process. Small example problems are solved in order to illustrate the approach, and areas for further research are discussed. 相似文献
999.
It is shown, using a Born-Oppenheimer model, that the four-body Efimov effect may occur in a system consisting of three identical heavy particles and one light particle, if the light-heavy interaction leads to a zeroenergy two-heavy-one-light bound state. 相似文献
1000.
Optimale Quantisierung 总被引:1,自引:0,他引:1
Peter M. Gruber 《Mathematische Semesterberichte》2002,49(2):227-251
Zusammenfassung. Optimale Quantisierungen oder – damit ?quivalent – minimale Summen von Momenten spielen in mehreren Zweigen der Mathematik
und ihrer Anwendungen eine Rolle. Ausgehend von der Fejes Tóth'schen Ungleichung für Summen von Momenten in der euklidischen
Ebene und einem zugeh?rigen Stabilit?tssatz, werden gewisse Erweiterungen auf normierte R?ume und riemannsche Mannigfaltigkeiten
h?herer Dimension besprochen. Die Ergebnisse werden dann auf Probleme aus folgenden Bereichen angewendet: (i) Datenübertragung,
(ii) Wahrscheinlichkeitstheorie, (iii) numerische Integration, (iv) Approximation konvexer K?rper und (v) isoperimetrische
Probleme.
Eingegangen am 29. Mai 2002 / Angenommen am 8. Juli 2002 相似文献