全文获取类型
收费全文 | 26641篇 |
免费 | 4755篇 |
国内免费 | 3681篇 |
专业分类
化学 | 18983篇 |
晶体学 | 346篇 |
力学 | 1625篇 |
综合类 | 217篇 |
数学 | 3463篇 |
物理学 | 10443篇 |
出版年
2024年 | 73篇 |
2023年 | 518篇 |
2022年 | 648篇 |
2021年 | 908篇 |
2020年 | 1190篇 |
2019年 | 1056篇 |
2018年 | 962篇 |
2017年 | 924篇 |
2016年 | 1343篇 |
2015年 | 1326篇 |
2014年 | 1620篇 |
2013年 | 2098篇 |
2012年 | 2328篇 |
2011年 | 2492篇 |
2010年 | 1820篇 |
2009年 | 1650篇 |
2008年 | 1898篇 |
2007年 | 1680篇 |
2006年 | 1506篇 |
2005年 | 1295篇 |
2004年 | 1017篇 |
2003年 | 856篇 |
2002年 | 925篇 |
2001年 | 772篇 |
2000年 | 597篇 |
1999年 | 553篇 |
1998年 | 417篇 |
1997年 | 389篇 |
1996年 | 409篇 |
1995年 | 345篇 |
1994年 | 263篇 |
1993年 | 203篇 |
1992年 | 187篇 |
1991年 | 181篇 |
1990年 | 145篇 |
1989年 | 106篇 |
1988年 | 63篇 |
1987年 | 68篇 |
1986年 | 78篇 |
1985年 | 58篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1969年 | 1篇 |
1957年 | 5篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 29 毫秒
91.
ZrO2 nanoparticles was uniformly co-deposited into a nickel matrix by electroplating of nickel from a Watts bath containing particles in suspension which were monodispersed with dispersant under DC electrodeposition condition. It was found that morphology, orientation and hardness of the nanocomposite coatings with monodispersed ZrO2 nanoparticles had lots of difference from the nanocomposite coatings with agglomerated ZrO2 nanoparticles and pure nickel coatings. Especially, the result of hardness showed that only a very low volume percent (less than 1 wt.%) of monodispered ZrO2 nanoparticles in Ni-ZrO2 nanocomposite coatings would result in higher hardness of the coatings. The hardness of Ni-ZrO2 nanocomposite coatings with monodispersed and agglomerated ZrO2 nanoparticles were 529 and 393 HV, respectively. The hardness value of the former composite coatings was over 1.3 times higher than that of the later. All these composite coatings were two-three times higher than that of pure nickel plating (207 HV) prepared under the same condition. The strengthening mechanisms of the Ni-ZrO2 nanocomposite coatings based on a combination of grain refinement strengthening from nickel matrix grain refining and dispersion strengthening from dispersion state of ZrO2 nanoparticles in the coatings. 相似文献
92.
93.
94.
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field. 相似文献
95.
96.
利用Ditzian-Totik光滑模,研究了推广的Kantorovich算子在Ba空间中的逼近,得到逼近的正定理与等价定理.所得结果改进、推广和统一了一些作者的结果. 相似文献
97.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献
98.
99.
100.
Augustine O. Esogbue Qiang Song Donovan Young 《Mathematical Methods of Operations Research》2006,63(3):525-542
In this paper the problem of verifying the Pareto-optimality of a given solution to a dynamic multiple-criterion decision (DMCD) problem is investigated. For this purpose, some new conditions are derived for Pareto-optimality of DMCD problems. In the literature, Pareto-optimality is characterized by means of Euler-Lagrangian differential equations. There exist problems in production and inventory control to which these conditions cannot be applied directly (Song 1997). Thus, it is necessary to explore new conditions for Pareto-optimality of DMCD problems. With some mild assumptions on the objective functionals, we develop necessary and/or sufficient conditions for Pareto-optimality in the sprit of optimization theory. Both linear and non-linear cases are considered. 相似文献