全文获取类型
收费全文 | 18853篇 |
免费 | 1317篇 |
国内免费 | 1055篇 |
专业分类
化学 | 8409篇 |
晶体学 | 54篇 |
力学 | 847篇 |
综合类 | 90篇 |
数学 | 405篇 |
物理学 | 3126篇 |
综合类 | 8294篇 |
出版年
2024年 | 61篇 |
2023年 | 181篇 |
2022年 | 450篇 |
2021年 | 429篇 |
2020年 | 505篇 |
2019年 | 412篇 |
2018年 | 454篇 |
2017年 | 547篇 |
2016年 | 643篇 |
2015年 | 710篇 |
2014年 | 826篇 |
2013年 | 1044篇 |
2012年 | 1220篇 |
2011年 | 1028篇 |
2010年 | 818篇 |
2009年 | 842篇 |
2008年 | 858篇 |
2007年 | 1081篇 |
2006年 | 941篇 |
2005年 | 842篇 |
2004年 | 771篇 |
2003年 | 723篇 |
2002年 | 659篇 |
2001年 | 545篇 |
2000年 | 595篇 |
1999年 | 542篇 |
1998年 | 423篇 |
1997年 | 474篇 |
1996年 | 376篇 |
1995年 | 361篇 |
1994年 | 293篇 |
1993年 | 232篇 |
1992年 | 223篇 |
1991年 | 205篇 |
1990年 | 194篇 |
1989年 | 160篇 |
1988年 | 144篇 |
1987年 | 103篇 |
1986年 | 62篇 |
1985年 | 51篇 |
1984年 | 52篇 |
1983年 | 23篇 |
1982年 | 32篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
基于Gross-Pitaevskii方程,运用有效化学势概念,研究了囚禁在组合势(由磁阱和三维光 晶格组成)中玻色凝聚气体在三维光晶格中的分布规律,并由此得到玻色凝聚气体的归 一化基态波函数.在取消组合势和仅取消光晶格而保留磁阱的两种情况下,运用传播子方 法求解出玻色凝聚气体密度分布的解析表达式.取消组合势后,理论计算所得到的玻色凝聚 气体聚随时间的演化规律与Greiner等的实验结果相一致.仅取消光晶格而保留磁阱时,研 究表明玻色凝聚气体的干涉模式呈现周期性的振荡行为.此外,在磁阱为各向异性的情况下 ,
关键词:
玻色凝聚气体
磁阱
光晶格
干涉模式 相似文献
32.
A fully quantum mechanical approach to the calculation and normalization of the Franck–Condon factors for diatomic species is described. The treatment is based on the fundamental demand of completeness of the energy eigenfunctions, which results in the rigorous sum rule for the Franck–Condon overlap integrals. The importance of this general rule has been discussed and thoroughly illustrated in the case of diatomic xenon molecules. Exactly solvable reference potentials for this system have been constructed and a complete basis of the actual energy eigenstates (including both bound and scattering states) has been created. Several direct spectroscopic applications to xenon excimers are presented, and their good agreement with relevant experimental data demonstrated. In particular, a kinetic model is proposed to explain the observed oscillatory structures in the fluorescence spectra of Xe2* [Chem. Phys. Lett. 117 (1985) 301] related to their classical left turning points. The same model gives a uniform explanation to the well-known first and second emission continua of rare gases. 相似文献
33.
34.
35.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献
36.
陈刚 《西北大学学报(自然科学版)》1995,(5)
运用深盆气圈闭的基本原理,综合分析了鄂尔多斯盆地下古生界天然气赋存的基本地质因素,论证并提出了盆地腹部下古生界深盆气圈闭的新认识,并依据盆地地质构造特征将其进一步划分为:西部前渊拗陷型和中东部复式向斜型两大深盆气赋存系统. 相似文献
37.
D. V. Kazakov A. I. Voloshin N. N. Kabal'nova V. V. Shereshovets V. P. Kazakov 《Russian Chemical Bulletin》1996,45(10):2452-2453
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of chemiluminescence.[/ p]Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2582–2583, October 1996. 相似文献
38.
赫崇衡 《安徽师范大学学报(自然科学版)》1995,18(2):34-39
具有MEL拓扑结构的新型钛硅沸石TS-2,对用H2O2直接将苯酚选择性氧化为邻、对苯二酚的反应,表现出优良的催化活性,H2O2的选择率和产物所上率都很高。产品混合物的定量分析采用气相色谱法,以OV-25为固定液、联苯为内标,得到了令人满意的结果。 相似文献
39.
Semi-empirical molecular orbital calculations were carried out for the compounds (C2H5)3As, (C2H5)3Ga and RAsH2 (R = C2H5, i-C3H7, i-C4H9, and t-C4H9) by using the CNDO/2-U program, and their capability of β-elimination reaction is compared on the basis of the torsion energy to the transition state, electrostatic interactions and orbital overlapping between the central atom and the β-hydrogen, and bond order of the metal-carbon, and carbon-hydrogen bond. In the comparison of (C2H5)3As with (C2H5)3Ga, we found that the β-elimination of (C2H5)3As could hardly be expected to take place in the thermal decomposition. The capability of β-elimination would be smaller in C2H5AsH2 than that in (C2H5)3As. Moreover when the ethyl group is replaced by a t-butyl group in RAsH2, the β-elimination reaction appears to become more difficult and a large possibility for a radical process is suggested. 相似文献
40.
R. Németh 《Journal of statistical physics》1991,63(1-2):419-424
We calculate the site occupation probabilities of one-dimensional lattice gas models within the canonical and grand canonical ensembles. The appearing differences do not vanish if we increase the system size keeping the site energies discrete. In this way one can explain the surprising numerical results of Barszczak and Kutner. This effect in the single-site occupation number disappears in higher dimensions. 相似文献