全文获取类型
收费全文 | 223184篇 |
免费 | 6090篇 |
国内免费 | 4823篇 |
专业分类
化学 | 102383篇 |
晶体学 | 2940篇 |
力学 | 13563篇 |
综合类 | 332篇 |
数学 | 41099篇 |
物理学 | 73780篇 |
出版年
2023年 | 896篇 |
2022年 | 2135篇 |
2021年 | 2689篇 |
2020年 | 3003篇 |
2019年 | 3365篇 |
2018年 | 12073篇 |
2017年 | 12562篇 |
2016年 | 8809篇 |
2015年 | 4136篇 |
2014年 | 4979篇 |
2013年 | 7224篇 |
2012年 | 11232篇 |
2011年 | 19406篇 |
2010年 | 12758篇 |
2009年 | 12748篇 |
2008年 | 16555篇 |
2007年 | 19502篇 |
2006年 | 5883篇 |
2005年 | 10790篇 |
2004年 | 7026篇 |
2003年 | 6655篇 |
2002年 | 4917篇 |
2001年 | 3164篇 |
2000年 | 2976篇 |
1999年 | 2084篇 |
1998年 | 2055篇 |
1997年 | 1846篇 |
1996年 | 1730篇 |
1995年 | 1362篇 |
1994年 | 1383篇 |
1993年 | 1282篇 |
1992年 | 1231篇 |
1991年 | 1286篇 |
1990年 | 1272篇 |
1989年 | 1172篇 |
1988年 | 1065篇 |
1987年 | 1063篇 |
1986年 | 1016篇 |
1985年 | 1088篇 |
1984年 | 1092篇 |
1983年 | 965篇 |
1982年 | 959篇 |
1981年 | 854篇 |
1979年 | 958篇 |
1978年 | 983篇 |
1977年 | 885篇 |
1976年 | 1037篇 |
1975年 | 897篇 |
1974年 | 934篇 |
1973年 | 973篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A firm's logistics cost, including shipping and inventory-carrying, is a substantial percentage of its sales. Nevertheless, typical inventory-control methods ignore or insufficiently represent the shipping cost. This paper describes a recursive algorithm that determines the reorder cycle-time that minimizes total logistics cost. It allows for a realistic accounting of shipping cost, which is modelled here as a function of shipping distance and weight. The algorithm uses a relaxation procedure to identify a suitable initial approximation to the optimal order cycle-time and then, through a series of recursive steps, moves to the optimal result. We demonstrate the algorithm with a single item, with a group of items that share a common order cycle, and with multi-items when item demands are random variables. Experience with this algorithm indicates that it converges to the optimal result in a very few steps. 相似文献
42.
Yu V Sharvin 《Pramana》1987,28(5):592-592
Investigation of the galvanomagnetic properties of disordered metals in weak magnetic fields [r(H)?l, wherer(H) is the electron trajectory radius andl, the electron free path], proved to be one of the effective experimental methods of studying disordered metals. The phase difference between the interfering electron waves is affected by the presence of magnetic flux in the sample. One of the observable effects is the oscillatory magnetoresistanceK(H) of multiconnected samples predicted by Altshuleret al (1981). The period ofK(H) oscillations for the hollow cylinders, networks or chains with orifices cross-sections areasS isΔH=φ 0/2S [whereφ 0=hc/e]. The amplitude and the phase of the oscillations depend on the spin orbit interaction, the intensity of superconductive fluctuation etc. It should be noted that in small “mesoscopic” single loops the oscillations with the periodΔH?φ 0/S were also observed recently (see also Altshuleret al 1987 included in this issue). 相似文献
43.
44.
We demonstrate a method that permits to obtain generalized solutions for some quasilinear equations and systems of hyperbolic
type. The corresponding variational principle is constructed using the theory of equilibrium of a potential in an external
field.
Dedicated to the memory of B. M. Levitan
Supported by RFBR grants Nos. 05-01-00522 and NSh-1551.2003.1, by Program No. 1 of the Branch of Mathematics, Russian Academy
of Sciences, and by INTAS project No. 03-51-6637. 相似文献
45.
S. N. Solov’ev K. A. Minasyan A. A. Korunov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):663-664
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol. 相似文献
46.
47.
V. Yu. Belashov 《Radiophysics and Quantum Electronics》2002,45(5):376-380
We consider generalizations of the earlier results, obtained for one-dimensional equations of the Kadomtsev–Petviashvili (KP) class, to two- and three-dimensional KP-class equations with an arbitrary nonlinearity index with allowance for the higher-order dispersion correction and terms describing dissipation and instability. The asymptotics of soliton and nonsoliton solutions are derived. Constructing phase portraits in the 8-dimensional space based on the results of a qualitative analysis of generalized Korteweg–de Vries (KdV) equations is discussed. 相似文献
48.
A. I. Magunov A. Ya. Faenov I. Yu. Skobelev T. A. Pikuz E. Biémont P. Quinet F. Blasco C. Bonte F. Dorchies T. Caillaud F. Salin C. Stenz 《Journal of Experimental and Theoretical Physics》2002,95(6):998-1005
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. 相似文献
49.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
50.
An overview of theoretical and experimental studies of the coherent type-B e
+
e-pair production by photons in aligned crystals performed at Nuclear Physics Institute at Tomsk Polytechnic University is given. 相似文献