全文获取类型
收费全文 | 360547篇 |
免费 | 13673篇 |
国内免费 | 7741篇 |
专业分类
化学 | 181248篇 |
晶体学 | 5108篇 |
力学 | 21404篇 |
综合类 | 320篇 |
数学 | 52940篇 |
物理学 | 120941篇 |
出版年
2022年 | 4021篇 |
2021年 | 4833篇 |
2020年 | 5094篇 |
2019年 | 5452篇 |
2018年 | 13561篇 |
2017年 | 14018篇 |
2016年 | 11887篇 |
2015年 | 6477篇 |
2014年 | 8505篇 |
2013年 | 13945篇 |
2012年 | 17219篇 |
2011年 | 25454篇 |
2010年 | 16974篇 |
2009年 | 17114篇 |
2008年 | 21399篇 |
2007年 | 24039篇 |
2006年 | 10547篇 |
2005年 | 14520篇 |
2004年 | 10834篇 |
2003年 | 10095篇 |
2002年 | 8198篇 |
2001年 | 7186篇 |
2000年 | 5769篇 |
1999年 | 4692篇 |
1998年 | 4032篇 |
1997年 | 4050篇 |
1996年 | 3997篇 |
1995年 | 3359篇 |
1994年 | 3322篇 |
1993年 | 3061篇 |
1992年 | 3260篇 |
1991年 | 3296篇 |
1990年 | 3124篇 |
1989年 | 3080篇 |
1988年 | 2954篇 |
1987年 | 2914篇 |
1986年 | 2740篇 |
1985年 | 3328篇 |
1984年 | 3356篇 |
1983年 | 2794篇 |
1982年 | 2734篇 |
1981年 | 2689篇 |
1980年 | 2488篇 |
1979年 | 2854篇 |
1978年 | 2823篇 |
1977年 | 2940篇 |
1976年 | 2964篇 |
1975年 | 2741篇 |
1974年 | 2670篇 |
1973年 | 2835篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A. N. Troflmchuk 《Journal of Mathematical Sciences》1991,57(5):3407-3409
We develop a method of computing the nonsteady-state and free oscillations of a framed elastic structure situated on an elastic base and containing an ideal compressible fluid. The solution uses the method of integral transforms in conjunction with the method of orthogonal polynomials. In the transform space the problem reduces to systems of linear algebraic equations. The Fourier transform is applied to return to the original space. Examples of the computation are given.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 69–72. 相似文献
52.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989. 相似文献
53.
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
54.
N. N. Manuylov 《Journal of Mathematical Sciences》2006,133(6):1686-1692
Renormalization formulas connecting the points of the orbits O
0
±
, i.e., the sequences generated by an irrational shift on the half-open interval [0, 1) or (0, 1], and the points of the orbits'
derivatives dmO
0
±
, i.e., the sequences obtained by restricting O
0
±
to half-open intervals of smaller length, are obtained. Bibliography: 5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 314, 2004, pp. 142–154. 相似文献
55.
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
56.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems. 相似文献
57.
58.
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
59.
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
60.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献