全文获取类型
收费全文 | 19929篇 |
免费 | 504篇 |
国内免费 | 130篇 |
专业分类
化学 | 13768篇 |
晶体学 | 110篇 |
力学 | 418篇 |
数学 | 3407篇 |
物理学 | 2860篇 |
出版年
2022年 | 122篇 |
2021年 | 177篇 |
2020年 | 225篇 |
2019年 | 217篇 |
2018年 | 167篇 |
2017年 | 160篇 |
2016年 | 343篇 |
2015年 | 345篇 |
2014年 | 380篇 |
2013年 | 858篇 |
2012年 | 881篇 |
2011年 | 1116篇 |
2010年 | 562篇 |
2009年 | 481篇 |
2008年 | 999篇 |
2007年 | 1017篇 |
2006年 | 1028篇 |
2005年 | 1117篇 |
2004年 | 967篇 |
2003年 | 820篇 |
2002年 | 716篇 |
2001年 | 282篇 |
2000年 | 266篇 |
1999年 | 217篇 |
1998年 | 196篇 |
1997年 | 254篇 |
1996年 | 309篇 |
1995年 | 230篇 |
1994年 | 225篇 |
1993年 | 212篇 |
1992年 | 209篇 |
1991年 | 186篇 |
1990年 | 186篇 |
1989年 | 155篇 |
1988年 | 171篇 |
1987年 | 180篇 |
1986年 | 142篇 |
1985年 | 308篇 |
1984年 | 268篇 |
1983年 | 206篇 |
1982年 | 282篇 |
1981年 | 245篇 |
1980年 | 290篇 |
1979年 | 267篇 |
1978年 | 269篇 |
1977年 | 281篇 |
1976年 | 243篇 |
1975年 | 200篇 |
1974年 | 190篇 |
1973年 | 196篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Richard P. Stanley 《Israel Journal of Mathematics》2004,143(1):317-339
We survey three recent developments in algebraic combinatorics. The first is the theory of cluster algebras and the Laurent
phenomenon of Sergey Fomin and Andrei Zelevinsky. The second is the construction of toric Schur functions and their application
to computing three-point Gromov-Witten invariants, by Alexander Postnikov. The third development is the construction of intersection
cohomology for nonrational fans by Paul Bressler and Valery Lunts and its application by Kalle Karu to the torich-vector of a nonrational polytope. We also briefly discuss the “half hard Lefschetz theorem” of Ed Swartz and its application
to matroid complexes.
Partially supported by NSF grant #DMS-9988459. 相似文献
72.
Martin E. V. Pedersen Lars S. Rishøj Henrik Steffensen Sanshui Xiao Niels Asger Mortensen 《Optical and Quantum Electronics》2007,39(10-11):903-911
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals is theoretically studied. Using a scattering-matrix approach and the Wigner–Smith delay time concept, we show that optical absorbance benefits both from slow-light phenomena as well as a high filling factor of the energy residing in the liquid. Utilizing strongly dispersive photonic crystal structures, we numerically demonstrate how liquid-infiltrated photonic crystals facilitate enhanced light–matter interactions, by potentially up to an order of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized absorbance cells for optical detection in lab-on-a-chip systems. 相似文献
73.
An adaptive pruning algorithm for the discrete L-curve criterion 总被引:1,自引:0,他引:1
Per Christian Hansen Toke Koldborg Jensen Giuseppe Rodriguez 《Journal of Computational and Applied Mathematics》2007
We describe a robust and adaptive implementation of the L-curve criterion. The algorithm locates the corner of a discrete L-curve which is a log–log plot of corresponding residual norms and solution norms of regularized solutions from a method with a discrete regularization parameter (such as truncated SVD or regularizing CG iterations). Our algorithm needs no predefined parameters, and in order to capture the global features of the curve in an adaptive fashion, we use a sequence of pruned L-curves that correspond to considering the curves at different scales. We compare our new algorithm to existing algorithms and demonstrate its robustness by numerical examples. 相似文献
74.
We present a linear rational pseudospectral (collocation) method with preassigned poles for solving boundary value problems. It consists in attaching poles to the trial polynomial so as to make it a rational interpolant. Its convergence is proved by transforming the problem into an associated boundary value problem. Numerical examples demonstrate that the rational pseudospectral method is often more efficient than the polynomial method. 相似文献
75.
The use of reagent concentration has resulted in increased rates for all stages of the REM resin synthesis of tertiary amines. These increases in rate translate into faster reaction times, higher yields and lower reagent consumption. Of the methods examined, the most successful was the use of perfluorous solvents, either alone or with a small amount of organic co-solvent. 相似文献
76.
A. Filarowski A. Koll A. Kochel J. Kalenik P. E. Hansen 《Journal of Molecular Structure》2004,700(1-3):67-72
The crystal structures of two ortho-hydroxy ketones (5-chloro-2-hydroxyacetophenone (I K) and 3,5-dichloro-2-hydroxyacetophenone (II K)) have been determined with X-ray diffraction at 100 K. A comparison of steric effects on properties of pseudoaromatic hydrogen bonds in ortho-hydroxy acetophenone and ortho-hydroxy ketimines have been carried out with the application of crystallographic data.
Nuclear quadrupole resonance (NQR) spectra have been measured and interpreted. 相似文献
77.
We study the stability and the properties of the ground state of neutral systems containing up to four positively charged
bosons and their antiparticles. Examples are the di-pionium molecule (π
+
π
−)2, which is almost identical to the positronium molecule (e
+
e
−)2, the tri-pionium (π
+
π
−)3, and the quadri-pionium (π
+
π
−)4 molecules. We briefly compare our results on the energy to those on the large-N limit of (π
+
π
−)
N
. We also show that the annihilation probability can be calculated accurately with simple wave functions when one uses the
generalized Schwinger rule.
Received September 5, 1994; accepted for publication October 15, 1994 相似文献
78.
79.
Richard Valenta 《Czechoslovak Journal of Physics》1998,48(9):1035-1048
The purpose of this paper is to solve the coupled non-homogeneous equations derived from the basic classical theory of the
acoustic propagation in visco-thermal fluid. The 1D radial distribution of pressure and temperature inside a spherical object
was found. It is supposed that both acoustic and thermal conditions on a surface of the object are known. The starting equations
are considered in the time domain and their solution was found without initial conditions for steady harmonic motion. 相似文献
80.