全文获取类型
收费全文 | 20783篇 |
免费 | 3903篇 |
国内免费 | 2736篇 |
专业分类
化学 | 12143篇 |
晶体学 | 308篇 |
力学 | 2274篇 |
综合类 | 175篇 |
数学 | 1737篇 |
物理学 | 10785篇 |
出版年
2024年 | 27篇 |
2023年 | 236篇 |
2022年 | 497篇 |
2021年 | 567篇 |
2020年 | 777篇 |
2019年 | 685篇 |
2018年 | 669篇 |
2017年 | 767篇 |
2016年 | 986篇 |
2015年 | 863篇 |
2014年 | 1263篇 |
2013年 | 1995篇 |
2012年 | 1425篇 |
2011年 | 1513篇 |
2010年 | 1179篇 |
2009年 | 1343篇 |
2008年 | 1367篇 |
2007年 | 1477篇 |
2006年 | 1260篇 |
2005年 | 1061篇 |
2004年 | 956篇 |
2003年 | 882篇 |
2002年 | 748篇 |
2001年 | 657篇 |
2000年 | 633篇 |
1999年 | 492篇 |
1998年 | 484篇 |
1997年 | 368篇 |
1996年 | 330篇 |
1995年 | 309篇 |
1994年 | 279篇 |
1993年 | 250篇 |
1992年 | 193篇 |
1991年 | 144篇 |
1990年 | 111篇 |
1989年 | 98篇 |
1988年 | 90篇 |
1987年 | 66篇 |
1986年 | 64篇 |
1985年 | 64篇 |
1984年 | 59篇 |
1983年 | 22篇 |
1982年 | 44篇 |
1981年 | 19篇 |
1980年 | 24篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
41.
Th. Seyller K.V. Emtsev F. Speck A. Tadich J.D. Riley O. Rader A.M. Shikin 《Surface science》2006,600(18):3906-3911
Photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy were used to investigate the electronic and structural properties of graphite layers grown by solid state graphitization of SiC(0 0 0 1) surfaces. The process leads to well-ordered graphite layers which are rotated against the substrate lattice by 30°. On on-axis 6H-SiC(0 0 0 1) substrates we observe graphitic layers with up to several 100 nm wide terraces. ARUPS spectra of the graphite layers grown on on-axis 6H-SiC(0 0 0 1) surfaces are indicative of a well-developed band structure. For the graphite/n-type 6H-SiC(0 0 0 1) layer system we observe a Schottky barrier height of ?B,n = 0.3 ± 0.1 eV. ARUPS spectra of graphite layers grown on 8° off-axis oriented 4H-SiC(0 0 0 1) show unique replicas which are explained by a carpet-like growth mode combined with a step bunching of the substrate. 相似文献
42.
Huafei Sun 《Geometriae Dedicata》2002,90(1):63-75
We study minimal submanifolds in the locally symmetric and conformally flat Riemannian manifold and generalize Yau's result obtained in J. Amer. Math. 97 (1975), 76–100. 相似文献
43.
A Garcia-Quiroz David L AzevedoE.C da Silva 《Journal of Physics and Chemistry of Solids》2002,63(10):1863-1866
Properties of oxygenated carbon nitride films have attracted the attention of physics researchers due to their magnetic and physical properties, as well as for their usefulness in the industry. The free radicals were investigated using electron paramagnetic resonance applied in the study of spin concentration due to the different mechanism of preparation of carbon nitride films by RF-discharge with different kinds of plasma. Unpaired spin concentrations, in the order of 1020 per cm3, were measured and their time recombination dependency was important in those films. The films were grown by plasma enhanced chemical vapor deposition using mixtures of hydrocarbons, N2 and O2 in different proportions. 相似文献
44.
NMR screening techniques in drug discovery and drug design 总被引:7,自引:0,他引:7
Brian J. Stockman Claudio Dalvit 《Progress in Nuclear Magnetic Resonance Spectroscopy》2002,41(3-4):187-231
45.
An optical measurement of vortex shape at a free surface 总被引:1,自引:0,他引:1
We have proposed an optical method of vortex shape measurement based on Fourier transform profilometry (FTP) and verified it by experiment. The results of our experiment proposed in this paper show that FTP can efficiently reconstruct the vortex shape at a free surface and this method is suitable for wide use in studying such problems as liquid shear flow, wake of an object, flow behind a bluff body, and wetting angle. 相似文献
46.
应用密度泛函理论,本文系统地研究了O在Au(111)表面上的吸附能、吸附结构、功函数、电子密度和投影态密度,给出了覆盖度从0.11ML到1.0ML的范围内,O的吸附特性随覆盖度变化的规律.研究发现O的稳定吸附位为3重面心立方(fcc)洞位,O在fcc洞位的吸附能对覆盖度比较敏感,其值随着覆盖度的增加而减小;O诱导Au(111)表面功函数的变化量与覆盖度成近线性关系,原因是Au表面电子向O偏移,形成表面偶极子;O—Au的相互作用形成成键态和反键态,且反键态都被占据,造成O—Au键很弱,O吸附能较小.
关键词:
表面吸附
Au(111)表面
密度泛函理论
电子特性 相似文献
47.
揭示非最大相干可能比最大相干产生更有效的非线性频率转换. 为此以三能级级联系统(没有最大相干)为例计算其非线性光学信号的强度, 并与三能级Λ型系统(具有最大相干)进行比较. 利用非微扰方法计算表明, 在双光子共振和相同参数的条件下, 级联系统产生的非线性光学信号的最大强度约是Λ系统的两倍. 利用缀饰态表象分析表明, 两个系统中耦合跃迁的自发辐射及其介入的不可逆三光子过程具有相反的作用. 它们在级联系统中加强非线性转换, 而在Λ系统中削弱非线性转换.
关键词:
电磁感应透明
非线性光学过程
双光子共振 相似文献
48.
The paper proposes a rational method to derive fairness measures for surfaces. It works in cases where isophotes, reflection lines, planar intersection curves, or other curves are used to judge the fairness of the surface. The surface fairness measure is derived by demanding that all the given curves should be fair with respect to an appropriate curve fairness measure. The method is applied to the field of ship hull design where the curves are plane intersections. The method is extended to the case where one considers, not the fairness of one curve, but the fairness of a one parameter family of curves. Six basic third order invariants by which the fairing measures can be expressed are defined. Furthermore, the geometry of a plane intersection curve is studied, and the variation of the total, the normal, and the geodesic curvature and the geodesic torsion is determined. 相似文献
49.
50.
烷基硫酸盐表面张力的量子化学研究 总被引:1,自引:0,他引:1
用AMl量子化学计算法优化了十三烷基硫酸根阴离子和——CH3在不同取代位的十二烷基硫酸根阴离子的几何构型,得到最优构型时最高占据分子轨道能级EHOMO、最低空轨道能级ELUMO、电子能量Eele和偶极矩μ等数据.将这些电子结构数据分别与表面张力相拟合,得到很好的相关性。文中讨论了——CH3在不同位置取代对表面张力的影响。 相似文献