全文获取类型
收费全文 | 6939篇 |
免费 | 195篇 |
国内免费 | 46篇 |
专业分类
化学 | 4781篇 |
晶体学 | 68篇 |
力学 | 204篇 |
数学 | 991篇 |
物理学 | 1136篇 |
出版年
2022年 | 41篇 |
2021年 | 68篇 |
2020年 | 77篇 |
2019年 | 92篇 |
2018年 | 58篇 |
2017年 | 57篇 |
2016年 | 149篇 |
2015年 | 124篇 |
2014年 | 134篇 |
2013年 | 297篇 |
2012年 | 343篇 |
2011年 | 415篇 |
2010年 | 233篇 |
2009年 | 172篇 |
2008年 | 328篇 |
2007年 | 371篇 |
2006年 | 398篇 |
2005年 | 377篇 |
2004年 | 311篇 |
2003年 | 314篇 |
2002年 | 275篇 |
2001年 | 109篇 |
2000年 | 97篇 |
1999年 | 58篇 |
1998年 | 66篇 |
1997年 | 84篇 |
1996年 | 111篇 |
1995年 | 72篇 |
1994年 | 74篇 |
1993年 | 72篇 |
1992年 | 62篇 |
1991年 | 71篇 |
1990年 | 66篇 |
1989年 | 63篇 |
1988年 | 67篇 |
1987年 | 40篇 |
1986年 | 48篇 |
1985年 | 98篇 |
1984年 | 94篇 |
1983年 | 68篇 |
1982年 | 97篇 |
1981年 | 92篇 |
1980年 | 91篇 |
1979年 | 69篇 |
1978年 | 89篇 |
1977年 | 73篇 |
1976年 | 70篇 |
1975年 | 68篇 |
1974年 | 74篇 |
1973年 | 74篇 |
排序方式: 共有7180条查询结果,搜索用时 15 毫秒
1.
Philip B. Burt 《Foundations of Physics》1993,23(6):965-968
Several interesting and important quantum field theories must contain the coupling constant in the boundary conditions. The theories considered include quantum electrodynamics of spin-1/2 fermions and gauge field theories. 相似文献
2.
Philip B. Lukins 《Chemical physics letters》1991,180(6):551-555
Measurements of the magneto-optical Cotton—Mouton effect at 632.8 nm of O2(3Σ) over a range of temperature (≈299–464 K) and pressure (up to 613 kPa) are reported and analysed. The study enables a useful comparison to be made of data obtained under different conditions by the two groups that have undertaken systematic measurements of this effect. Agreement between the experimental results and also the derived molecular properties is found to be satisfactory. 相似文献
3.
4.
Philip A. Wheeler Michael Brungs Graham R. Atkins 《Journal of Sol-Gel Science and Technology》2003,27(3):321-326
Organically modified silicates (ormosils) have been viewed as possible materials for optical signal processing devices for communications networks. One significant problem obstructing their use in this application is the absorption of infrared light by hydroxy species (present for example in silanol groups (SiOH) and water) around the communications wavelengths (1310 and 1550 nm). We have investigated several ormosil compositions, synthesised via an aqueous sol-gel method, to determine if residual hydroxy groups can be removed more effectively via reducing the connectivity of the material by increasing the number of organic groups (such as Si—CH3). Furthermore, we have investigated the effect of different inert atmospheres on the drying process. It was found that reducing the connectivity does promote the removal of hydroxy absorption, mainly via the condensation of residual silanol groups, but also by removal of residual water, depending on the other precursors in the system. It was also found that the drying atmosphere used (nitrogen or helium) had no effect on the drying process. 相似文献
5.
Philip Sinclair 《Discrete Mathematics》2004,286(3):171-175
Let G be a 2-connected graph with minimum degree at least 3. We prove that there exists an even circuit C in G with factorization F={F1,F2} such that G−E(F1) is 2-connected. 相似文献
6.
An investigation of BELENE Nuclear Power Plant (NPP) free field signal is presented in the current study. An SH wave propagation trough multilayer geological media in the region is considered. An original structural model of the geological column has been developed. The investigated layers are isotropic, with constant depth and skyline parallel. The SH rays are with an arbitrary angle as far as the layers are concerned. The seismic SH waves have been generated by a special detonation device. The main results of the study are graphically illustrated. A comparison between the original BELENE NPP experimental and the numerical surface (free field) signals (obtained by the formulated direct problem) for the investigated geological column has been carried out and its results are hereby shown. 相似文献
7.
The N-carboethoxy precursor to (±)-tecomanine has been prepared in 11 steps from 2-methyl-1-buten-3-yne. The key step, Pauson-Khand cyclization of a methylated 5-aza-6-nonen-1-yne succeeds, but only in low yield, a consequence of the dialkyl substitution about the azaenyne framework. Nevertheless, the overall sequence to that point is one of the more efficient to be described. 相似文献
8.
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
9.
10.