全文获取类型
收费全文 | 511654篇 |
免费 | 3183篇 |
国内免费 | 939篇 |
专业分类
化学 | 240805篇 |
晶体学 | 7295篇 |
力学 | 28417篇 |
综合类 | 9篇 |
数学 | 79272篇 |
物理学 | 159978篇 |
出版年
2020年 | 4531篇 |
2019年 | 5397篇 |
2018年 | 12527篇 |
2017年 | 12919篇 |
2016年 | 12653篇 |
2015年 | 5508篇 |
2014年 | 9201篇 |
2013年 | 18909篇 |
2012年 | 17520篇 |
2011年 | 25113篇 |
2010年 | 17828篇 |
2009年 | 18094篇 |
2008年 | 23371篇 |
2007年 | 25515篇 |
2006年 | 15564篇 |
2005年 | 16859篇 |
2004年 | 14383篇 |
2003年 | 13842篇 |
2002年 | 12870篇 |
2001年 | 12066篇 |
2000年 | 9836篇 |
1999年 | 7174篇 |
1998年 | 6505篇 |
1997年 | 6413篇 |
1996年 | 6068篇 |
1995年 | 5211篇 |
1994年 | 5323篇 |
1993年 | 5312篇 |
1992年 | 5493篇 |
1991年 | 5883篇 |
1990年 | 5755篇 |
1989年 | 5788篇 |
1988年 | 5500篇 |
1987年 | 5517篇 |
1986年 | 5224篇 |
1985年 | 6372篇 |
1984年 | 6739篇 |
1983年 | 5621篇 |
1982年 | 6017篇 |
1981年 | 5602篇 |
1980年 | 5243篇 |
1979年 | 5867篇 |
1978年 | 6122篇 |
1977年 | 6171篇 |
1976年 | 6250篇 |
1975年 | 5861篇 |
1974年 | 5726篇 |
1973年 | 6046篇 |
1972年 | 4655篇 |
1971年 | 4175篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
M.-K. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):13-18
We examine the influence of relativistic and QED effects on the existence of the 1,3P
o
H- resonances between n
= 2 and 3 hydrogen thresholds, the relativistic and QED corrections and the coupling effects between the high singlet and triplet
states are considered as first-order perturbations. We firstly obtain accurate non-relativistic resonant energies and widths
of fifteen 1P
o
resonances, and fifteen 3P
o
resonances. The fifteen 1P
o
resonances are classified to be
3
(2, 0)
-
n
( 4 ?
n
? 12) and
3
(1, 1)
+
n
( 3 ?
n
? 8). The fifteen 3P
o
resonances are classified to be
3
(2, 0)
+
n
( 3 ?
n
? 12) and
3
(1, 1)
-
n
( 4 ?
n
? 8). We found there exist six Feshbach resonances for
3
(2, 0)
-
n
(1P
o
) series, four Feshbach resonances for
3
(1, 1)
+
n
(1P
o
) series, seven Feshbach resonances for
3
(2, 0)
+
n
(3P
o
) series, and three Feshbach resonances for
3
(1, 1)
-
n
(1P
o
) series.
Received 22 February 2002 Published online 24 September 2002 相似文献
942.
We present a detailed derivation of the fluctuation transport theory, previously developed by Gerlach and Mycielski. The basic idea is the transformation of carrier-densities and fields into the rest frame of each type of carriers and application of the Fluctuation-Dissipation-theorem for monopolar, unscreened carrier densities. In the present paper, the theory is applied to a model system containing free electrons, rigid ions and polarizable neutral donors. We compare our results with experimental data for the polar II–VI-semiconductor Eu1-xSrxS. 相似文献
943.
944.
The response to Hg(II) of a thin all-solid-state Te-doped silver chalcogenide membrane, described by the general formula Ag2 + δSe1 − xTex, which has been electrochemically prepared following a previously proposed approach, has been investigated. The kinetics of formation of the membrane's secondary dynamic response to Hg(II) has been successfully combined with the precise timing and transient signal, typical for flow-injection (FI) measurements, in developing a sensitive and reliable mercury FI detector. Under optimized stream conditions it exhibits a linear Nernstian response, with a double slope of the calibration graph of 59 mV dec−1, over the mercury(II) concentration range 10−6 − 10−3 M, the typical sample throughput amounting to about 70 samples per hour. The observed chemical amplification of the signal is due to the specificity of the processes dominating the initial step in formation of the steady-state signal of the membrane to mercury. The analytical performance of the Hg(II) FI detector, as regards sensitivity, reproducibility, selectivity and long-term stability has been thoroughly investigated. The exact procedure for membrane electrodeposition is given and the potential of the proposed approach as a cost-effective way for preparing chalcogenides of unique structure and properties has been outlined in the above context. 相似文献
945.
946.
947.
E. Pancheva 《Journal of Mathematical Sciences》1995,76(1):2177-2180
In this paper we give a characterization of the classMSS of all one-dimensional d.f.'s G satisfying the functional equation Gα(x)=G(L(x)), where α∈(0, 1] andL(x) is strictly monotone.
Supported by the Bulgarian Ministry of Education and Science (grant MM-17/1993).
Proceedings of the Seminar on Stability Problems for Stochastic Models, Moscow, 1993. 相似文献
948.
949.
E. A. Bugrii 《Theoretical and Mathematical Physics》1996,109(3):1590-1607
A representation in the form of a functional integral is obtained for the partition function of the inhomogeneous 2D Ising model on a triangular lattice where the coupling parameters are arbitrary functions of coordinates. The method for transforming the partition function into an integral uses an auxiliary six-component Grassmann field in which the Grassmann fields corresponding to one of the components commute with the others. Thus, one pair of components realizes a representation of the q-deformed group SLq(2, R) with q=–1 and the other two pairs correspond to the usual Grassmann spinors (q=1). An explicit expression in terms of the modified Pfaffian is found for the Gaussian integral over these fields and its relation to the ordinary Grassmann functional integral is established.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 109, No. 3, pp. 441–463, December, 1996. 相似文献
950.
Thermoelastic stress analysis was used to document the effect of composite damage on the stress distribution in three ceramic matrix composites. Composite damage was found to significantly alter the thermoelastic response of each material, with the greatest effect noted in SiC/CAS. Thermoelastic imaging of these materials affords a more complete picture of how the various damage mechanisms affect the stress distribution. In particular, a stress concentration factor computed from thermoelastic images, serves as an indicator of stress redistribution. The stress concentration factors were computed by comparing notch root to far field temperatures, and monitored after the introduction of various amounts of damage. In each material, the stress concentration factor diminished as the damaging load approached the ultimate stress. Reduction in the stress concentration is associated with local changes in modulus, mechanistically arising from combinations of fiber, matrix and interface fracture. Stress redistribution occurs as a consequence of modulus changes, leading to lower notch sensitivity in each of the tested composites. 相似文献