全文获取类型
收费全文 | 106692篇 |
免费 | 10191篇 |
国内免费 | 11910篇 |
专业分类
化学 | 72433篇 |
晶体学 | 1269篇 |
力学 | 3787篇 |
综合类 | 1328篇 |
数学 | 16975篇 |
物理学 | 33001篇 |
出版年
2024年 | 108篇 |
2023年 | 937篇 |
2022年 | 1645篇 |
2021年 | 3439篇 |
2020年 | 3249篇 |
2019年 | 3081篇 |
2018年 | 2567篇 |
2017年 | 2923篇 |
2016年 | 3735篇 |
2015年 | 3642篇 |
2014年 | 4552篇 |
2013年 | 8092篇 |
2012年 | 6128篇 |
2011年 | 6022篇 |
2010年 | 5257篇 |
2009年 | 6659篇 |
2008年 | 6716篇 |
2007年 | 7053篇 |
2006年 | 6200篇 |
2005年 | 4927篇 |
2004年 | 4397篇 |
2003年 | 4024篇 |
2002年 | 5982篇 |
2001年 | 3260篇 |
2000年 | 2671篇 |
1999年 | 2390篇 |
1998年 | 2158篇 |
1997年 | 1738篇 |
1996年 | 1593篇 |
1995年 | 1534篇 |
1994年 | 1337篇 |
1993年 | 1221篇 |
1992年 | 1191篇 |
1991年 | 836篇 |
1990年 | 688篇 |
1989年 | 553篇 |
1988年 | 616篇 |
1987年 | 451篇 |
1986年 | 394篇 |
1985年 | 512篇 |
1984年 | 401篇 |
1983年 | 220篇 |
1982年 | 441篇 |
1981年 | 586篇 |
1980年 | 532篇 |
1979年 | 535篇 |
1978年 | 433篇 |
1977年 | 333篇 |
1976年 | 285篇 |
1973年 | 202篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
971.
高密度氩气的原子间相互作用与状态方程 总被引:5,自引:4,他引:1
本文从高密度气体的原子间相互作用出发进行思考,在修改范德瓦耳方程的基础上,提出了一种新的适用于高密度气体的状态方程,并用以对氩气临界区的等温压缩线进行计算,结果与实验值很符合. 相似文献
972.
The three-dimensional structure of the calcite (104)-water interface has been determined with surface X-ray scattering. Nine crystal truncation rods (including specular and non-specular rods) were measured providing both vertical and lateral sensitivity to the interfacial structure. The results reveal that calcite is nearly ideally terminated with a single surface hydration layer that includes two inequivalent water molecules having distinct heights of 2.3 ± 0.1 and 3.5 ± 0.2 Å, each with a well-defined lateral registry with respect to the calcite surface. No additional layering of water is observed beyond this surface hydration layer. Small displacements in the outer two calcium carbonate layers were also observed. These results are compared with previous experimental and computational results. 相似文献
973.
Yoshihide Yoshimoto 《Surface science》2004,556(1):52-62
A conception of a structure formation suitable for nano-technology is proposed, which is programmable and suitable for mass production-like lithography. This conception utilizes the controlled folding of chains like the scan-lines of television. Its possibility and property were studied theoretically using the modeled chains consist of beads. By adopting the interaction among the beads which can distinguish the kind of the partner by its polarity and is chiral to break the chiral symmetry of the folded state, the special chains which have the unique ground states could be designed. In these ground states, the chains are folded like the scan-lines of television. The thermodynamic properties of the suggested chains were studied by the Monte Carlo simulations and the suggested chains showed the phase-transition-like behavior which is distinct compared to both the random chains and the chain that has only the non-specific attraction. The size dependence and the effects of adding the non-specific attraction and modifying the border of the folded conformation were also studied. 相似文献
974.
Doubly tunable sum frequency generation (SFG) spectra demonstrate that the water molecules at gold/electrolyte interface change their orientation with applied potential. At negative potentials, water molecules in the double layer align with their oxygen atom pointing to the solution. As potential became positive to be close to the potential of zero charge (PZC), the SFG signal decreased, suggesting the OH groups of the water molecule are either in random orientation or parallel to the electrode. As potential became more positive than the PZC, the SFG signal increased again with the oxygen-up orientation as same as in the negative potential region, indicating that water molecules interact with the adsorbed sulfate anions. The peak position of the SFG spectra indicates a relatively disordered state of water molecules at the gold electrode surface, in contrast to the previously observed ice-like structure of water at electrolyte/oxide interfaces. 相似文献
975.
电子被HF和HCl分子散射总截面的计算 总被引:1,自引:1,他引:0
利用光学势方法计算了能量在10eV—1000eV范围内电子被H、F和Cl原子散射的总截面,并与已有的实验结果和理论计算进行了比较;又利用可加性规则(additivityrule)计算得到了电子被HF和HCl分子散射的总截面,计算结果也与已有的实验结果和理论计算进行了比较 相似文献
976.
977.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P
Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical
application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results
of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics.
Received: 10 December 1997 相似文献
978.
以MCl2和配体L(L=1,10-菲罗啉-5,6-二酮)为原料,合成了标题配合物MLCl2,M=NiⅡ,CuⅡ,ZnⅡ,并经元素分析、热谱、IR和摩尔电导表征.三者均为四配位的电中性配合物,热稳定性高于500K,易溶于DMF、DMSO和吡啶,可溶于乙腈和水.它们在DMF中于350nm和315nm附近显示出强的M-L荷移跃迁 相似文献
979.
P. Galatola M. Zelazna I. Lelidis 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(1):51-56
We study the surface behavior of a semi-infinite smectogenic sample bounded by a solid wall, in the presence of an external
electric field. Our analysis is performed in the framework of a Landau-de Gennes theory. For the sake of simplicity, we consider
only the case in which, in the absence of field and surfaces, a direct isotropic to smectic-A transition occurs, while in
the presence of the electric field a nonspontaneous nematic phase appears. Two new surface phases are identified, namely a
parasmectic and a surface-induced smectic phase. The shifts in the transition temperatures and the critical behavior of the surface states are analyzed.
Received: 25 August 1997 / Accepted: 23 January 1998 相似文献
980.