全文获取类型
收费全文 | 243549篇 |
免费 | 6206篇 |
国内免费 | 5099篇 |
专业分类
化学 | 115508篇 |
晶体学 | 3190篇 |
力学 | 15115篇 |
综合类 | 323篇 |
数学 | 50576篇 |
物理学 | 70142篇 |
出版年
2022年 | 2238篇 |
2021年 | 2848篇 |
2020年 | 3124篇 |
2019年 | 3402篇 |
2018年 | 14258篇 |
2017年 | 14039篇 |
2016年 | 11114篇 |
2015年 | 4088篇 |
2014年 | 5211篇 |
2013年 | 8139篇 |
2012年 | 11269篇 |
2011年 | 18397篇 |
2010年 | 11988篇 |
2009年 | 12374篇 |
2008年 | 13488篇 |
2007年 | 15224篇 |
2006年 | 6471篇 |
2005年 | 6750篇 |
2004年 | 6490篇 |
2003年 | 6472篇 |
2002年 | 5666篇 |
2001年 | 4791篇 |
2000年 | 3729篇 |
1999年 | 2877篇 |
1998年 | 2743篇 |
1997年 | 2399篇 |
1996年 | 2290篇 |
1995年 | 1927篇 |
1994年 | 1950篇 |
1993年 | 1911篇 |
1992年 | 1896篇 |
1991年 | 2012篇 |
1990年 | 1938篇 |
1989年 | 1888篇 |
1988年 | 1714篇 |
1987年 | 1657篇 |
1986年 | 1617篇 |
1985年 | 1746篇 |
1984年 | 1842篇 |
1983年 | 1600篇 |
1982年 | 1623篇 |
1981年 | 1425篇 |
1980年 | 1354篇 |
1979年 | 1539篇 |
1978年 | 1670篇 |
1977年 | 1665篇 |
1976年 | 1689篇 |
1975年 | 1543篇 |
1974年 | 1581篇 |
1973年 | 1567篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A. I. Bril' V. P. Kabashnikov N. V. Kuz'mina Yu. V. Khodyko 《Journal of Applied Spectroscopy》1991,55(3):934-939
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 478–484, September, 1991. 相似文献
72.
In this paper, we consider a class of functional equations and prove three theorems which give the approximation properties
and error estimates of the optimal polynomial approximation of slution of those functional equations. 相似文献
73.
A. P. Prudnikov Yu. A. Brychkov O. I. Marichev 《Journal of Mathematical Sciences》1991,54(6):1239-1341
Translated from Itogi Nauki i Tekhniki, Seriya Matematicheskii Analiz, Vol. 27, pp. 3–146, 1989. 相似文献
74.
The stressed state of a thick three-layer plate with two circular holes is studied. Resolving functions are expressed in terms of Kolosov-Muskhelishvili integral potentials and modified Bessel functions. The problem is reduced to solving an infinite set of linear algebraic equations.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 25–28, 1987. 相似文献
75.
76.
D. Yu. Gladilov S. Yu. Nekhaevskii A. V. Ochkin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(12):1934-1939
Various methods for describing the distribution of water in the H2O-tributyl phosphate (TBP) system were considered. An equation for describing the deviations from the Henry law was proposed. A three-parameter equation for calculating the distribution of water in H2O-TBP-solvent systems was derived. It is based on the additive solubility model and allows for the dependence of the activity coefficients on the TBP concentration. Based on the published data, the parameters of the equation for a number of systems were calculated. 相似文献
77.
This paper proposes two constructive heuristics for the well-known single-level uncapacitated dynamic lot-sizing problem. The proposed heuristics, called net least period cost (nLPC) and nLPC(i), are developed by modifying the average period cost concept from Silver and Meal's heuristic, commonly known as least period cost (LPC). An improved tie-breaking stopping rule and a locally optimal decision rule are proposed in the second heuristic to enhance performance. We test the effectiveness of the proposed heuristics by using 20 benchmarking test problems frequently used in the literature. Furthermore, we perform a large-scale simulation study involving three factors, 50 experimental conditions, and 100?000 randomly generated problems to evaluate the proposed heuristics against LPC and six other well-known constructive heuristics in the literature. The simulation results show that both nLPC and nLPC(i) produce average holding and setup costs lower than or equal to those of LPC in every one of the 50 experimental conditions. The proposed heuristics also outperform each of the six other heuristics evaluated in all experimental conditions, without an increase in computational requirements. Lastly, considering that both nLPC and nLPC(i) are fairly simple for practitioners to understand and that lot-sizing heuristics have been commonly used in practice, there should be a very good chance for practical applications of the proposed heuristics. 相似文献
78.
79.
80.
In a two-dimensional array of magnetic moments with planar magnetization and relatively weak anisotropy in the basal plane, a stepwise phase transition is induced by an external magnetic field parallel to the easy axis of the system. This transition is similar to the spin flop phase transition in weakly anisotropic Heisenberg antiferromagnets with the significant difference that it is accompanied by the rearrangement of the sublattice structure of the magnet; i.e., it can be interpreted as a topological transition. The transition should manifest itself for arrays of submicron magnetic particles (magnetic dots) on nonmagnetic substrates, which have recently become the object of intensive research. 相似文献