全文获取类型
收费全文 | 2019篇 |
免费 | 291篇 |
国内免费 | 215篇 |
专业分类
化学 | 1512篇 |
晶体学 | 23篇 |
力学 | 126篇 |
综合类 | 17篇 |
数学 | 208篇 |
物理学 | 639篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 72篇 |
2021年 | 71篇 |
2020年 | 124篇 |
2019年 | 109篇 |
2018年 | 72篇 |
2017年 | 67篇 |
2016年 | 118篇 |
2015年 | 97篇 |
2014年 | 114篇 |
2013年 | 161篇 |
2012年 | 176篇 |
2011年 | 203篇 |
2010年 | 108篇 |
2009年 | 103篇 |
2008年 | 128篇 |
2007年 | 110篇 |
2006年 | 67篇 |
2005年 | 63篇 |
2004年 | 53篇 |
2003年 | 57篇 |
2002年 | 60篇 |
2001年 | 62篇 |
2000年 | 44篇 |
1999年 | 45篇 |
1998年 | 23篇 |
1997年 | 26篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有2525条查询结果,搜索用时 15 毫秒
151.
By use of the exact diagonalization method, the quantum phase transition and entanglement in a 6-Li atom system are studied.
It is found that entanglement appears before the quantum phase transition and disappears after it in this exactly solvable
quantum system. The present results show that the von Neumann entropy, as a measure of entanglement, may reveal the quantum
phase transition in this model. 相似文献
152.
Acylthiourea derivatives are well known for a wide range of biological activities likebactericidal, fungicidal, herbicidal, insecticidal action and regulating activity for plantgroWth"'. In recent years, substituted phenoxyacetic acid derivatives have beenreported as highly efficient herbicides4. In this paper. a series of substitutedphenoxyacetyl thiourea containing substituted pyrimidine ring sa~so were synthesizedand tested for their biological activities. All of them are new compounds and… 相似文献
153.
Scattering by a cylindrical cavity in a porous solid is studied by the boundary layer approximation of Mei and Foda. Quantitative results will be presented for two cases: (1) vacuum cavity and (2) cavity filled with fluid. In each case both P and SV incident waves will be studied. Focus will be on the stress distribution near the cavity surface and contrast to the non-porous case will be pointed out. The effect of fluid compressibility due to possible entrainment of air will be discussed. These results should be of interest to the design of long tunnels subject to earthquakes. 相似文献
154.
The speciation of strontium in human and bovine milk has been computed using a chemical equilibrium model and the ECCLES program. The calculations show 相似文献
155.
The experimental charge density distribution of dimethyl-trans-2-oxohexahydro-pyrimidine-4,6-dicarboxylate 1 has been determined using single-crystal X-ray diffraction data measured at 100 K, in terms of the rigid-pseudoatom formalism. Multipole refinement converged at R(F) = 0.034 for 7283 reflections with I > 3 sigma (I) and sin theta/lambda < or = 1.13 A(-1). Covalent and hydrogen bonding interactions are analyzed using a topological analysis of the Laplacian of the charge density. The experimentally derived electrostatic potential mapped onto the reactive surface of the molecule reveals the potential binding sites of 1. 相似文献
156.
In this note, we prove that if N is a compact totally geodesic submanifold of a complete Riemannian manifold M, g whose sectional curvature K satisfies the relation K ≥ k > 0, then
for any point m ∈ M. In the case where dim M = 2, the Gaussian curvature K satisfies the relation K ≥ k ≥ 0, and γ is of length l, we get Vol (M, g) ≤
if k ≠ 0 and Vol (M, g ≤ 2ldiam (M) if k = 0.__________Published in Ukrains’kyi Matematychnyi Zhurnal, Vol. 56, No. 11, pp. 1576–1583, November, 2004. 相似文献
157.
Gangsong Leng Lin Si Qingsan Zhu 《Proceedings of the American Mathematical Society》2004,132(9):2655-2660
For let and denote the arithmetic mean and geometric mean of elements of , respectively. It is proved that if is an integer in , then
with equality if and only if . Furthermore, as a generalization of this inequality, a mixed power-mean inequality for subsets is established.
with equality if and only if . Furthermore, as a generalization of this inequality, a mixed power-mean inequality for subsets is established.
158.
We study the magnetic quantum phase transition in an anisotropic Kondo lattice model. The dynamical competition between the RKKY and Kondo interactions is treated using an extended dynamic mean field theory appropriate for both the antiferromagnetic and paramagnetic phases. A quantum Monte Carlo approach is used, which is able to reach very low temperatures, of the order of 1% of the bare Kondo scale. We find that the finite-temperature magnetic transition, which occurs for sufficiently large RKKY interactions, is first order. The extrapolated zero-temperature magnetic transition, on the other hand, is continuous and locally critical. 相似文献
159.
L.?Si Email author Y.L.?Chang J.?Ding C.K.?Ong B.?Yao 《Applied Physics A: Materials Science & Processing》2003,77(5):641-643
In order to search for new materials for the application of magnetic refrigeration, the polycrystalline perovskite compound Nd2/3Sr1/3MnO3 was prepared by a solid-state method. The dependence of the magnetization on the applied field and temperature was measured near the Curie temperature. In terms of Maxwells equation, the temperature dependence of the absolute value of the isothermal magnetic entropy change |SM| at various applied fields from 1 T to 5 T was determined. The results showed that a large magnetic entropy change was observed in this compound. The maximum magnetic entropy change |SMmax|can reach 3.25 J/kgK with an applied field of 1 T at the Curie temperature of 257.5 K, which equals that of Gd. At 5 T applied field, it is 7.57 J/kgK. Such good magnetocaloric properties make this compound a promising candidate for the application of magnetic refrigeration in the room-temperature range. PACS 74.25.Ha; 75.30.-m; 75.30.Sg; 75.50.-y; 75.60.-d 相似文献
160.
采用分子束外延的方法在BaF2(111)衬底上制备出了高质量的Pb1-xMnxSe(0≤x≤0.0681)薄膜.X射线衍射结果表明,Pb1-xMnxSe薄膜为立方相NaCl型结构,没有观察到MnSe相分离现象,薄膜的取向为平行于衬底(111)晶面.晶格常数随着Mn含量的增加逐渐减小,Mn含量由Vegard公式得到.通
关键词:
1-xMnxSe外延薄膜')" href="#">Pb1-xMnxSe外延薄膜
透射光谱
带隙
折射率 相似文献