全文获取类型
收费全文 | 196673篇 |
免费 | 1984篇 |
国内免费 | 634篇 |
专业分类
化学 | 109093篇 |
晶体学 | 3313篇 |
力学 | 7917篇 |
综合类 | 5篇 |
数学 | 18569篇 |
物理学 | 60394篇 |
出版年
2016年 | 2346篇 |
2015年 | 1740篇 |
2014年 | 2465篇 |
2013年 | 7992篇 |
2012年 | 5373篇 |
2011年 | 6737篇 |
2010年 | 4497篇 |
2009年 | 4418篇 |
2008年 | 6052篇 |
2007年 | 6220篇 |
2006年 | 5957篇 |
2005年 | 5444篇 |
2004年 | 4981篇 |
2003年 | 4467篇 |
2002年 | 4352篇 |
2001年 | 5808篇 |
2000年 | 4428篇 |
1999年 | 3525篇 |
1998年 | 2754篇 |
1997年 | 2789篇 |
1996年 | 2742篇 |
1995年 | 2531篇 |
1994年 | 2407篇 |
1993年 | 2292篇 |
1992年 | 2791篇 |
1991年 | 2676篇 |
1990年 | 2623篇 |
1989年 | 2649篇 |
1988年 | 2584篇 |
1987年 | 2598篇 |
1986年 | 2408篇 |
1985年 | 3286篇 |
1984年 | 3295篇 |
1983年 | 2727篇 |
1982年 | 2923篇 |
1981年 | 2855篇 |
1980年 | 2763篇 |
1979年 | 2901篇 |
1978年 | 3143篇 |
1977年 | 2966篇 |
1976年 | 2898篇 |
1975年 | 2761篇 |
1974年 | 2704篇 |
1973年 | 2720篇 |
1972年 | 1759篇 |
1971年 | 1467篇 |
1968年 | 1930篇 |
1967年 | 2129篇 |
1966年 | 1920篇 |
1965年 | 1499篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Current techniques of water wave visualization such as shadowgraphy and stereo photography are widely used but are deficient
in many aspects. Refraction based visualization observes the bending of light as it traverses across a liquid-air interface.
This work describes the continued development of techniques to measure the surface height of a liquid free surface. The method,
Reference Image Topography, utilizes refraction of light at the free surface as a function of the local angle of that surface.
Particle Image Velocimetry (PIV) software is used to evaluate apparent dislocations of the target image viewed through the
free surface, which are approximately proportional to the surface angle. High-resolution images are presented of the dynamic
surface topography for a point source and the shallow water flow around a vertical cylinder. 相似文献
182.
The black-body radiation is considered in a theory with noncommutative electromagnetic fields; that is noncommutativity is introduced in field space, rather than in real space. A direct implication of the result on cosmic microwave background map is argued. 相似文献
183.
Backstepping design is proposed for synchronization of Genesio chaotic system. Firstly, the control problem for the chaos synchronization of nominal Genesio systems without unknown parameters is considered. Next, an adaptive backstepping control law is derived to make the error signals between drive Genesio system and response Genesio system with an uncertain parameter asymptotically synchronized. Finally, the approach is extended to the synchronization problem for the system with three unknown parameters. The stability analysis in this article is proved by using a well-known Lyapunov stability theorem. Note that the approach provided here needs only a single controller to realize the synchronization. Two numerical simulations are presented to show the effectiveness of the proposed chaos synchronization scheme. 相似文献
184.
H. P. Gunnlaugsson 《Hyperfine Interactions》2006,167(1-3):851-854
The general problem of finding a distribution in hyperfine interaction parameters from experimental Mössbauer spectra is outlined. Existing methods may lack flexibility to be easily applicable to simple problems. A line shape for hyperfine parameter distributions is given, which is based on linear segments in the probability function. This method is applied in the analysis of samples containing iron in a silicate glass. 相似文献
185.
Heinz H. Bauschke 《Proceedings of the American Mathematical Society》2007,135(1):135-139
Recently, S. Reich and S. Simons provided a novel proof of the Kirszbraun-Valentine extension theorem using Fenchel duality and Fitzpatrick functions. In the same spirit, we provide a new proof of an extension result for firmly nonexpansive mappings with an optimally localized range.
186.
von Eynatten G. Ritter T. Bömmel H. E. Dransfeld K. 《Zeitschrift für Physik B Condensed Matter》1987,65(3):341-345
A new model is presented which explains well the dramatic decrease of the Mössbauer line intensities with raising temperatures for freely dispersed iron microscrystals. In contrast to other theories which consider mainly vibration to be responsible we discuss here the decrease in terms of large amplitude diffusive rotational or translational jumps of the particles. Such diffusive jumps lead — in agreement with the observation — to a strong reduction of the Mössbauer-intensity without broadening the line width in a noticeable way. The typical potential well for a diffusing particle in an equilibrium position is derived quantitatively to be 13 meV. The model might be important also for a new understanding of the dynamics of catalytic clusters either in contact with each other or with larger solid surfaces.Part of this work was supported by the DFG Sonderforschungsbereich 306, Konstanz 相似文献
187.
Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal
fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of
the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical
effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation
in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical
results obtained are in good agreement with our earlier experimental results presented elsewhere [1]. 相似文献
188.
陈永静 朱胜江 J.H.Hamilton A.V.Ramayya J.K.Hwang Y.X.Luo J.O.Rasmussen 车兴来 丁怀博 李明亮 《中国物理 C》2006,30(8):740-744
通过测量252Cf自发裂变所产生的瞬发γ射线, 对146Ce核的高自旋结构进行了重新研究, 结果更新了以前报道的能级纲图, 把八级形变集体带扩展到更高的自旋, 并且重新构建了可能的准γ带结构. 此外, 用反射不对称壳模型(RASM)对146Ce核的八级形变带进行了计算, 低自旋处的计算结果与实验数据符合得很好. 相似文献
189.
Y.-Q. Peng J.-H. Yang F.-P. Lu Q.-S. Yang H.-W. Xing X.-S. Li C.-A. Song 《Applied Physics A: Materials Science & Processing》2007,86(2):225-229
Based on the assumption of Gaussian energy distributions of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), analytical expressions of generalized Einstein relation in chemically doped organic semiconductor are developed, by approximation of Coulomb traps with a rectangle potential well. Numerical calculations show that traditional Einstein relations do not hold for chemically doped organic semiconductors. Similar to physical doping, the dependence of diffusion coefficient to mobility D/μ ratio on the carrier concentration has a maximum. An essential difference between chemical doping and physical doping is that, the D/μ ratio in chemically doped organic semiconductors depends not only on carrier concentration and doping concentration, but also on the applied electric field. PACS 71.20.Rv; 72.90.+y; 73.50.-h 相似文献
190.
Z.G. Xiao R.J. HuH.Y. Wu G.M. JinZ.Y. Li L.M. DuanH.W. Wang B.G. ZhangS.F. Wang Z.Y. WeiH.S. Xu Y.T. ZhuS.L. Li F. FuX.H. Yuan Z.Q. Feng 《Physics letters. [Part B]》2006
The inclusive reduced velocity correlation functions of the intermediate mass fragments were measured in the reactions of 36Ar + 112,124Sn at 35 MeV/u. The anti-correlation is observed to be stronger in 36Ar + 124Sn system than that in 36Ar + 112Sn. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three body Coulomb repulsive trajectory model is employed to calculate the emission time scale of the IMFs for the two systems. The time scale is 150 fm/c in 36Ar + 112Sn and 120 fm/c in the 36Ar + 124Sn, respectively. 相似文献