全文获取类型
收费全文 | 16415篇 |
免费 | 435篇 |
国内免费 | 137篇 |
专业分类
化学 | 11330篇 |
晶体学 | 134篇 |
力学 | 510篇 |
数学 | 2510篇 |
物理学 | 2503篇 |
出版年
2022年 | 134篇 |
2021年 | 152篇 |
2020年 | 218篇 |
2019年 | 200篇 |
2018年 | 185篇 |
2017年 | 149篇 |
2016年 | 313篇 |
2015年 | 269篇 |
2014年 | 311篇 |
2013年 | 780篇 |
2012年 | 760篇 |
2011年 | 1038篇 |
2010年 | 485篇 |
2009年 | 437篇 |
2008年 | 844篇 |
2007年 | 882篇 |
2006年 | 929篇 |
2005年 | 856篇 |
2004年 | 783篇 |
2003年 | 713篇 |
2002年 | 683篇 |
2001年 | 232篇 |
2000年 | 200篇 |
1999年 | 163篇 |
1998年 | 190篇 |
1997年 | 199篇 |
1996年 | 232篇 |
1995年 | 180篇 |
1994年 | 185篇 |
1993年 | 147篇 |
1992年 | 153篇 |
1991年 | 159篇 |
1990年 | 132篇 |
1989年 | 113篇 |
1988年 | 147篇 |
1987年 | 142篇 |
1986年 | 108篇 |
1985年 | 212篇 |
1984年 | 236篇 |
1983年 | 169篇 |
1982年 | 241篇 |
1981年 | 220篇 |
1980年 | 224篇 |
1979年 | 206篇 |
1978年 | 198篇 |
1977年 | 181篇 |
1976年 | 182篇 |
1975年 | 152篇 |
1974年 | 163篇 |
1973年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
It is shown that data on the dissociation rate of deuterium obtained in an experiment at the Sudbury Neutrino Observatory provides evidence that the Continuous Spontaneous Localization wavefunction collapse model should have mass–proportional coupling to be viable. 相似文献
42.
43.
Irradiation of 3,4,5-trideuteriopyridine at 254 nm in the vapor phase results in the formation of a mixture of 2,3,4-trideuteriopyridine and 2,3,6-trideuteriopyridine. The formation of these products is consistent with a photoisomerization mechanism involving equilibrating azaprefulvene intermediates. This is the first direct evidence that pyridine vapor undergoes photoisomerization resulting in transposition of the pyridine ring atoms. 相似文献
44.
Huimin Xie Biao Li Robert Geer Bai Xu James Castracane 《Optics and Lasers in Engineering》2003,40(3):163-177
A focused ion beam (FIB) Moiré method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB Moiré is generated by the interference between a prepared specimen grating and FIB raster scan lines. The principle of the FIB Moiré is described. The sensitivity and accuracy of deformation measurement are discussed in detail. Several specimen gratings with 0.14 and 0.20 μm spacing are used to generate FIB Moiré patterns. The FIB Moiré method is successfully used to measure the residual deformation in a micro-electro-mechanical system structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method. 相似文献
45.
46.
Jilly James Chidambaram Ramalechume Asit Baran Mandal 《Journal of Polymer Science.Polymer Physics》2007,45(17):2410-2420
The shape, size, aggregation, hydration, and correlation times of water insoluble PEO‐PPO‐PEO triblock copolymer micelles with sodium dodecylsulfate (SDS) micelles were investigated using transport studies and dynamic light scattering technique. From the conductance of micellar solutions of the polymer in 25 mM SDS and 5 mM NaCl, the hydration of polymer micelles were determined using the principle of obstruction of electrolyte migration by the polymer. The asymmetry of the micellar particles of polymer and polymer‐SDS mixed micellar systems in 5 mM NaCl and their average axial ratios were calculated using intrinsic viscosity and hydration data obeying Simha–Einstein equation. Hydration number and micellar sizes were variable with temperature. The shape of the polymer micelles has been ellipsoidal rather than spherical. The micellar volume, hydrodynamic radius, radius of gyration, diffusional coefficients as well as translational, rotational and effective correlation times have been calculated from the absolute values of the axes. The partial molal volume of polymer micelles has also been determined and its comparison with the molar volume of pure polymer suggested a volume contraction due to immobilization of the water phase by the hydrophilic head groups of the polymer. The thermodynamic activation parameters for viscous flow favor a more ordered water structure around polymer micelles at higher temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2410–2420, 2007 相似文献
47.
48.
49.
Past cellular automata models of self-replication have always been initialized with an original copy of the structure that will replicate, and have been based on a transition function that only works for a single, specific structure. This article demonstrates for the first time that it is possible to create cellular automata models in which a self-replicating structure emerges from an initial state having a random density and distribution of individual components. These emergent self-replicating structures employ a fairly general rule set that can support the replication of structures of different sizes and their growth from smaller to larger ones. This rule set also allows “random” interactions of self-replicating structures with each other and with other structures within the cellular automata space. Systematic simulations show that emergence and growth of replicants occurs often and is essentially independent of the cellular space size, initial random pattern of components, and initial density of components, over a broad range of these parameters. The number of replicants and the total number of components they incorporate generally approach quasi-stable values with time. 相似文献
50.