全文获取类型
收费全文 | 12205篇 |
免费 | 4288篇 |
国内免费 | 3581篇 |
专业分类
化学 | 3696篇 |
晶体学 | 206篇 |
力学 | 2418篇 |
综合类 | 325篇 |
数学 | 2367篇 |
物理学 | 11062篇 |
出版年
2024年 | 119篇 |
2023年 | 439篇 |
2022年 | 586篇 |
2021年 | 561篇 |
2020年 | 444篇 |
2019年 | 466篇 |
2018年 | 333篇 |
2017年 | 477篇 |
2016年 | 461篇 |
2015年 | 593篇 |
2014年 | 971篇 |
2013年 | 778篇 |
2012年 | 814篇 |
2011年 | 828篇 |
2010年 | 864篇 |
2009年 | 920篇 |
2008年 | 955篇 |
2007年 | 818篇 |
2006年 | 900篇 |
2005年 | 748篇 |
2004年 | 769篇 |
2003年 | 730篇 |
2002年 | 702篇 |
2001年 | 653篇 |
2000年 | 493篇 |
1999年 | 411篇 |
1998年 | 412篇 |
1997年 | 433篇 |
1996年 | 350篇 |
1995年 | 314篇 |
1994年 | 317篇 |
1993年 | 268篇 |
1992年 | 263篇 |
1991年 | 226篇 |
1990年 | 210篇 |
1989年 | 199篇 |
1988年 | 79篇 |
1987年 | 71篇 |
1986年 | 41篇 |
1985年 | 26篇 |
1984年 | 15篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
磁化水具有比普通水更小的簇合分子,具有硬度、pH值、含氧浓度均增加的性质.采用傅立叶变换红外光谱技术,测量了大豆与玉米实验组与空白组的叶绿体的红外光谱,发现两者在酰氨键的振动吸峰处存在一定的差异,实验组的吸收明显强于对照组,说明磁化水对作物的生长发育有一定影响,具有一定的生物效应. 相似文献
3.
4.
英国《新科学家》杂志日前刊载文章称,新一代X射线激光器能用于研究蛋白质和其他生物分子的构造和行为。新一代X射线激光器的能量将是现有设备的100亿倍,能使科学家观察到最微小最精妙的分子构造。利用这种技术可以破解复杂的蛋白质和完整的病毒结构,甚至可能获得DNA的三维图像。X射线激光器被称作自由电子激光器。与传统激光器不同,自由电子激光器并不是通过光照或电流刺激某种物质发射光子,而是使用粒子加速器让极小的电子云穿过磁铁组,这些磁铁把电子推来推去,直到电子释放出光脉冲。传统激光器的激光波长是由发射光子的物质本… 相似文献
5.
Ennio Arimondo 《量子光学学报》2006,12(B08):59-60
Cold atoms and, more recently, Bose-Einstein condensates (BEC's) in optical lattices have attracted increasing interest since their first realization. In particular, the formal similarity between the wavefunction of a BEC inside the periodic potential of an optical lattice and of the electrons in a crystal lattice has triggered theoretical and experimental efforts alike. Many phenomena from condensed matter physics, such as Bloch oscillations and Landau-Zener tunneling have been shown to be observable also in optical lattices. An important difference between electrons in a crystal lattice and a BEC inside the periodic potential of an optical lattice is the strength of the self interaction and hence the magnitude of the nonlinearity of the system. Electrons in a metal are almost noninteracting, whereas atoms inside a BEC interact strongly. A' perturbation approach is appropriate in the former case while in the latter the full nonlinearity must be taken into account. From this feature new physics is expected. Most experiments to date have been carried out in the regime of shallow lattice depth, for which the system is well described by the mean field Gross-Pitaevskii equation with a periodic potential. Moreover, the nonlinearity induced by the mean-field of the condensate has been shown, both theoretically and experimentally, to give rise to instabilities in certain regions of the Brillouin zone. These instabilities are not present in the corresponding linear system, i.e. the electron system. Experimental and theoretical results on the subject of nonlinear Landau-Zener tunneling and nonlinearity-induced instabilities in a Bose-Einstein condensate interacting with an external periodic potential will be presented. 相似文献
6.
7.
The electronic structures for three types of PbW04 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-Vpb) and fluorine doped PWO crystal (F^-:PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb^2 ions are unable to trap holes forming Pb^3 or Pb^4 to compensate for VPb^2-. The hole-trappers in PWO-Vpb are O^2- ions. Two of the longer-bond O^2- ions share a hole forming O2^3-, and four of the longer-bond oxygen ions trap two holes forming an associated color centre [O2^3--Vpb-O2^3-], which may be the origin of the 42Onto absorption band. It is also concluded that the doping of F^- would reduce the band gap and F^- ions substituting for O^2- can effectively restrict the formation of [O2^3--Vpb-O2^3-] and weaken the 42Onm absorption band and hence enhance the scintillation property of PWO. 相似文献
8.
9.
Geng Sheng WANG 《数学学报(英文版)》2005,21(5):1005-1014
This work is concerned with Pontryagin's maximum principle of optimal control problems governed by some non-well-posed semilinear heat equations. A type of approach to the non-well-posed optimal control problem is given. 相似文献
10.