全文获取类型
收费全文 | 7250篇 |
免费 | 202篇 |
国内免费 | 9篇 |
专业分类
化学 | 4699篇 |
晶体学 | 19篇 |
力学 | 98篇 |
数学 | 1090篇 |
物理学 | 1555篇 |
出版年
2020年 | 51篇 |
2019年 | 48篇 |
2018年 | 54篇 |
2016年 | 162篇 |
2015年 | 123篇 |
2014年 | 160篇 |
2013年 | 299篇 |
2012年 | 273篇 |
2011年 | 293篇 |
2010年 | 180篇 |
2009年 | 168篇 |
2008年 | 250篇 |
2007年 | 261篇 |
2006年 | 250篇 |
2005年 | 255篇 |
2004年 | 233篇 |
2003年 | 192篇 |
2002年 | 161篇 |
2001年 | 142篇 |
2000年 | 109篇 |
1999年 | 114篇 |
1998年 | 114篇 |
1997年 | 113篇 |
1996年 | 122篇 |
1995年 | 103篇 |
1994年 | 121篇 |
1993年 | 121篇 |
1992年 | 123篇 |
1991年 | 101篇 |
1990年 | 115篇 |
1989年 | 109篇 |
1988年 | 101篇 |
1987年 | 111篇 |
1986年 | 133篇 |
1985年 | 154篇 |
1984年 | 117篇 |
1983年 | 103篇 |
1982年 | 102篇 |
1981年 | 101篇 |
1980年 | 120篇 |
1979年 | 77篇 |
1978年 | 105篇 |
1977年 | 98篇 |
1976年 | 97篇 |
1975年 | 64篇 |
1974年 | 79篇 |
1973年 | 76篇 |
1972年 | 60篇 |
1971年 | 51篇 |
1970年 | 56篇 |
排序方式: 共有7461条查询结果,搜索用时 31 毫秒
1.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
2.
3.
Hana Macková Daniela Králová Daniel Horák 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5884-5898
The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe2O3 nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe2O3, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe2O3 nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007 相似文献
4.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light. 相似文献
5.
Gerhard Rein 《Mathematical Methods in the Applied Sciences》1992,15(5):365-374
We consider a collisionless plasma, which consists of electrons and positively charged ions and is confined to a bounded domain in ?3. The distribution functions of the particles are assumed to satisfy specular reflections on the boundary of the domain and the boundary is assumed to be perfectly conducting. We establish the existence of stationary plasmas in the non-relativistic, electrostatic case described by the Vlasov–Poisson system as well as in the relativistic, electrodynamic case described by the relativistic Vlasov–Maxwell system. 相似文献
6.
Using topological methods we give a proof that the free product of two strict subgroup separable groups with infinite cyclic amalgamation is subgroup separable. 相似文献
7.
8.
9.
Gerhard Lessner 《General Relativity and Gravitation》2004,36(5):1241-1242
10.