全文获取类型
收费全文 | 86524篇 |
免费 | 1848篇 |
国内免费 | 1624篇 |
专业分类
化学 | 30547篇 |
晶体学 | 924篇 |
力学 | 7112篇 |
综合类 | 107篇 |
数学 | 32892篇 |
物理学 | 18414篇 |
出版年
2023年 | 153篇 |
2022年 | 322篇 |
2021年 | 336篇 |
2020年 | 357篇 |
2019年 | 431篇 |
2018年 | 10656篇 |
2017年 | 10490篇 |
2016年 | 6438篇 |
2015年 | 1328篇 |
2014年 | 875篇 |
2013年 | 1012篇 |
2012年 | 4609篇 |
2011年 | 11276篇 |
2010年 | 6251篇 |
2009年 | 6644篇 |
2008年 | 7257篇 |
2007年 | 9328篇 |
2006年 | 744篇 |
2005年 | 1698篇 |
2004年 | 1874篇 |
2003年 | 2221篇 |
2002年 | 1248篇 |
2001年 | 439篇 |
2000年 | 425篇 |
1999年 | 301篇 |
1998年 | 297篇 |
1997年 | 232篇 |
1996年 | 302篇 |
1995年 | 211篇 |
1994年 | 151篇 |
1993年 | 159篇 |
1992年 | 111篇 |
1991年 | 105篇 |
1990年 | 88篇 |
1989年 | 83篇 |
1988年 | 90篇 |
1987年 | 76篇 |
1986年 | 76篇 |
1985年 | 70篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1982年 | 44篇 |
1981年 | 43篇 |
1980年 | 48篇 |
1979年 | 45篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Antonio Strozzi 《Journal of Elasticity》2012,108(1):119-123
The solution of cylindrical problems is addressed. A series solution is considered of the biharmonic equation, in which the series terms of the stress function Φ are expressions based upon Legendre polynomials and logarithmically singular functions. An explicit form of a polynomial supplementing each logarithmically singular part of the series solution is obtained. 相似文献
112.
We consider the flow of a viscous incompressible fluid in a pipe when the boundary is a deformable shell of Naghdi type. We prove that the corresponding system of partial differential equations has a solution when the deformation of the shell is smooth and small enough. We propose an algorithm that uncouples the unknowns and prove its convergence. 相似文献
113.
We apply the recently improved version of the 0–1 test for chaos to real experimental time series of laser droplet generation process. In particular two marginal regimes of dripping are considered: spontaneous and forced dripping. The outcomes of the test reveal that both spontaneous and forced dripping time series can be characterized as chaotic, which coincides with the previous analysis based on nonlinear time series analysis. 相似文献
114.
Krishna S Kumar 《Pramana》1993,41(1):45-53
We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z0 pole. From measurements of the τ polarization in e+ e?→τ + τ ?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg v e /g a e =0.066±0.015 andg V τ /g A τ =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG τ /G μ =0.996±0.008. 相似文献
115.
A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints. 相似文献
116.
固相萃取技术(SPE)作为一种分析物提取和样品前处理方法,相比于传统的液液萃取更利于目标分析物的分离,提高痕量分析物的检出能力和被测物的回收率,同时减少对环境的二次污染,且操作过程简单方便,耗时较短.碳纳米管(CNTs)的独特性能使其成为非常有吸引力的SPE吸附材料.介绍了碳纳米管在农残、药品、有机化合物、无机金属离子等检测中的应用,并对碳纳米管在分析领域中的应用前景进行了展望. 相似文献
117.
本文研究了Hg< I )配合物与N2H4的定向反应,得出该反应为定量四电子反应.该反应随反应体系pH值增大,反应速度加快.. Cu( I)是该反应有效的催化剂.文中讨论了该反应的反应机理,N,H:是该反应主要中间体,通过在反应液中加入不饱和酸已成功地截获N2H4 相似文献
118.
应用扩散型指标,Taylor幂法则和lwao m——x回归分析法,分析了东方钝绥螨在柑桔园的分布型。结果表明,东方钝绥螨在柑桔园呈聚集分布。其最适抽样数N=7.34+31.357 5 x1/2,利用该螨释放防治叶螨的序贯抽样的上下限T0(N)=4.2276N±6.3663 N1/2 . 相似文献
119.
Within the framework of effective-mass approximation, the effects of a laser field on the ground-state donor binding energy in zinc-blende (ZB) GaN/AlGaN quantum well (QW) have been investigated variationally. Numerical results show that the donor binding energy is highly dependent on QW structure parameters and Al composition in ZB GaN/AlGaN QW. The laser field effects are more noticeable on the donor binding energy of an impurity localized inside the QW with small well width and low Al composition. However, for the impurity located in the vicinity of the well edge of the QW, the donor binding energy is insensible to the variation of Al composition, well width and laser field intensity in ZB GaN/AlGaN QW. In particular, the competition effects between laser field and quantum confinement on impurity states have also been investigated in this paper. 相似文献
120.
Xiaoming Wu Yulin Hua Zhaoqi Wang Jiajin Zheng Shougen Yin Jiachun Deng Kongwu Wu Songliu Feijian Zhu Xia Niu 《Optik》2006,117(8):373-376
A bright white organic light-emitting diode (OLED) has been successfully fabricated in which a greenish-white emitting host Bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2) is doped with an orange-red fluorescent dye 5,6,11,12-tetraphenylnaphthacene (rubrene). The pure white light emission with CIE coordinates of (0.341, 0.334) is achieved at the driving voltage of 20 V, and the corresponding luminance and external quantum efficiency are 4000 Cd/m2 and 0.63%. On the other hand, the pure red, green, and blue (RGB) emissions are obtained from the white OLED combined well with RGB custom-built optical color filters (CFs) with peaks at 616, 556, and 456 nm, respectively. Moreover, based upon the color mixture principles, we build a model of multi-color display mixed by the pure RGB emissions under the controllable bias. 相似文献