全文获取类型
收费全文 | 220926篇 |
免费 | 2698篇 |
国内免费 | 1324篇 |
专业分类
化学 | 122731篇 |
晶体学 | 3228篇 |
力学 | 8889篇 |
综合类 | 61篇 |
数学 | 24365篇 |
物理学 | 65674篇 |
出版年
2020年 | 1754篇 |
2019年 | 1896篇 |
2018年 | 2483篇 |
2017年 | 2531篇 |
2016年 | 3645篇 |
2015年 | 2424篇 |
2014年 | 3537篇 |
2013年 | 8872篇 |
2012年 | 7686篇 |
2011年 | 9396篇 |
2010年 | 6651篇 |
2009年 | 6451篇 |
2008年 | 8792篇 |
2007年 | 8900篇 |
2006年 | 8384篇 |
2005年 | 7705篇 |
2004年 | 6870篇 |
2003年 | 6053篇 |
2002年 | 5985篇 |
2001年 | 6703篇 |
2000年 | 5067篇 |
1999年 | 3669篇 |
1998年 | 3038篇 |
1997年 | 3008篇 |
1996年 | 3011篇 |
1995年 | 2618篇 |
1994年 | 2718篇 |
1993年 | 2581篇 |
1992年 | 2829篇 |
1991年 | 2894篇 |
1990年 | 2703篇 |
1989年 | 2616篇 |
1988年 | 2557篇 |
1987年 | 2498篇 |
1986年 | 2520篇 |
1985年 | 3301篇 |
1984年 | 3359篇 |
1983年 | 2804篇 |
1982年 | 3046篇 |
1981年 | 2811篇 |
1980年 | 2607篇 |
1979年 | 2790篇 |
1978年 | 2998篇 |
1977年 | 3032篇 |
1976年 | 3059篇 |
1975年 | 2793篇 |
1974年 | 2906篇 |
1973年 | 2956篇 |
1972年 | 2318篇 |
1971年 | 1845篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
The electromagnetic field distribution on an illuminated rough gold surface has been investigated by apertureless scanning near-field optical microscopy. The sample consists of an alumina substrate with a variable gold coverage ranging from 0 to 30 monolayers (ML). For such small thicknesses, the metal layer is not continuous but exhibits a certain roughness. We have studied the influence of this thickness on the electromagnetic field localization on the surface. For a gold coverage smaller than 10 equivalent monolayers, the electromagnetic field is almost uniform on the surface. For 10 and 14 ML, the field becomes inhomogeneous and isolated, localized peaks start to be visible. The width of the peaks is smaller than 50 nm. Above 14 ML, strong variations are apparent everywhere on the sample. Their amplitude tends to saturate beyond 24 ML. A complete statistical study of the sample (standard deviation, Fourier analysis) is performed. 相似文献
872.
We show that the racemic states of the B 2 phase of liquid crystals composed of banana-shaped molecules do not satisfy the Curie principle. Thus it is argued that these states cannot exist in bulk samples and the homochiral states constitute the only stable microscopic structures. A reinterpretation of the racemic states with the same macroscopic optical behaviour is proposed in terms of mixtures of the homochiral structures. 相似文献
873.
L. A. Malozemov 《Mathematical Notes》1991,50(3):935-938
Translated from Matematicheskie Zametki, Vol. 50, No. 3, pp. 81–86, September, 1991. 相似文献
874.
875.
R. Arnaldi R. Averbeck K. Banicz J. Castor B. Chaurand C. Cicalo A. Colla P. Cortese S. Damjanovic A. David A. De Falco A. Devaux A. Drees L. Ducroux H. En’yo A. Ferretti M. Floris A. Foerster P. Force N. Guettet A. Guichard H. Gulkanian J. Heuser M. Keil L. Kluberg J. Lozano C. Lourenço F. Manso A. Masoni P. Martins A. Neves H. Ohnishi C. Oppedisano P. Parracho P. Pillot G. Puddu E. Radermacher P. Ramalhete P. Rosinsky E. Scomparin J. Seixas S. Serci R. Shahoyan P. Sonderegger H.J. Specht R. Tieulent G. Usai R. Veenhof H.K. Wöhri 《The European Physical Journal C - Particles and Fields》2007,49(1):235-241
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs
is observed above the yield expected from neutral meson decays. The unprecedented sample size close to 400000 events and the
good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of
the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution
from π+π-→ϱ→μ+μ- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The
pT-differential mass spectra show the excess to be much stronger at low pT than at high pT. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to
the chiral condensate.
PACS 25.75.-q; 12.38.Mh; 13.85.Qk 相似文献
876.
M. L. Eritsyan L. A. Gyurdzhyan L. T. Melkonyan G. V. Akopyan 《Russian Journal of Applied Chemistry》2006,79(10):1666-1668
Composition and rheological characteristics of aqueous solutions of acrylic acid/urea copolymers were studied, including the composition dependences of the equivalent conductivity and viscosity. 相似文献
877.
为了精确计算束流在离子光学系统中的传输,用Visual FORTRAN 6.5语言编写了一个计算程序,长约13000行. 此程序可以计算由三圆筒单透镜、三膜片单透镜、双元筒透镜、均匀场静电加速管、磁四极透镜、六极磁铁、静电四极透镜、偏转磁铁、螺线管透镜、ExB~正交电磁场分析器、静电偏转器、漂浮管、QWR(Quarter Wave Resonators)和SLR(Split Loop Resonators)射频加速元件等元件任意组成的离子光学系统. 粒子轨迹的计算可精确到三级近似. 粒子的分布类型也可以有多种选择. 程序具有最优化计算功能,即可以自动调整元件的参数,以实现所需要的光学条件. 各元件之后的横向和纵向相图以及系统的束流包络线以图形方式显示在屏幕上. 相似文献
878.
879.
880.
P. Lugli C. Erlen A. Pecchia F. Brunetti L. Latessa A. Bolognesi G. Csaba G. Scarpa A. di Carlo 《Applied Physics A: Materials Science & Processing》2007,87(3):593-598
Molecular devices have lately attracted increased attention due to some appealing features such as their low production cost,
flexibility in the substrate choice, possibility of large area deployment, and possibly higher integration capabilities. Starting
from a series of results obtained from our groups, we critically review the state-of-the-art in the field of simulation of
organic and molecular systems, by analyzing and comparing existing approaches, and looking at the open problems and possible
solutions and future developments.
PACS 72.80.Le 相似文献