全文获取类型
收费全文 | 3726篇 |
免费 | 671篇 |
国内免费 | 1361篇 |
专业分类
化学 | 2821篇 |
晶体学 | 163篇 |
力学 | 304篇 |
综合类 | 93篇 |
数学 | 574篇 |
物理学 | 1803篇 |
出版年
2024年 | 6篇 |
2023年 | 62篇 |
2022年 | 168篇 |
2021年 | 156篇 |
2020年 | 144篇 |
2019年 | 144篇 |
2018年 | 142篇 |
2017年 | 190篇 |
2016年 | 180篇 |
2015年 | 198篇 |
2014年 | 234篇 |
2013年 | 370篇 |
2012年 | 317篇 |
2011年 | 326篇 |
2010年 | 322篇 |
2009年 | 334篇 |
2008年 | 364篇 |
2007年 | 281篇 |
2006年 | 317篇 |
2005年 | 276篇 |
2004年 | 194篇 |
2003年 | 133篇 |
2002年 | 124篇 |
2001年 | 142篇 |
2000年 | 148篇 |
1999年 | 105篇 |
1998年 | 59篇 |
1997年 | 35篇 |
1996年 | 38篇 |
1995年 | 33篇 |
1994年 | 35篇 |
1993年 | 27篇 |
1992年 | 28篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有5758条查询结果,搜索用时 0 毫秒
1.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
2.
We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors. 相似文献
3.
The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr2-H2O and LiBr-KBr-MgBr2-H2O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr2-H2O is hydrate II type as NaBr and NaBr·2H2O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr2-H2O is a complex type as the double salt KBr·MgBr2·6H2O formed. In addition to this double salt, the three single salts LiBr·2H2O, KBr and MgBr2·6H2O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones. 相似文献
4.
Jiatian Chen Le Yang Ying Li Qinghua Hou Lanlan Li Peng Jin 《International journal of quantum chemistry》2019,119(16):e25961
Inorganic planar ring-shape molecules with 4n + 2 π electrons are always the focus of experimental synthesis and theoretical research due to their potential aromaticity and stability. In this work, the whole series of five-membered heterocycle monoanions X nY5-n− (X, Y = group 15 elements; n = 1-4) were thoroughly investigated by means of density functional theory calculations. They all have large formation energies and HOMO-LUMO gap energies, suggesting the potential thermodynamic and kinetic stability. Their aromaticities are comparable to that of typical aromatic hydrocarbons. Their thermal stabilities were firmly established by the ab initio molecular dynamics simulations. As most of them are predicted for the first time, their various spectra were simulated for experimental characterization. Furthermore, we demonstrate that these five-membered cyclic anions can be employed as η5-ligand to construct novel all-inorganic metallocenes, which may serve as the building blocks of low-dimensional nanomaterials. 相似文献
5.
6.
7.
GAO Xiaoyan CAI Xiao CAO Zeng CUI Chenghe 《核工业西南物理研究院年报(英文版)》2004,(1):54-56
HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated from the operation staff during discharges, to guarantee the safe and reliable operation of the vacuum system, it is necessary to watch the vacuum system outside the machine hall with an automatic monitoring system. The paper describes the design and manufacture of the monitoring system. 相似文献
8.
The vacuum system of today's tokamak devices is designed to meet the operational requirements of the experiments. The operation can be divided into five modes, (1) pumping down and leak detecting of the vacuum vessel, (2) baking, (3) plasma-facing component (PFC) conditioning, (4)evacuating and controlling of the particles at plasma edge, (5) plasma discharge experiments. 相似文献
9.
10.