全文获取类型
收费全文 | 3163篇 |
免费 | 394篇 |
国内免费 | 188篇 |
专业分类
化学 | 2056篇 |
晶体学 | 188篇 |
力学 | 46篇 |
综合类 | 9篇 |
数学 | 267篇 |
物理学 | 1179篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 43篇 |
2021年 | 61篇 |
2020年 | 126篇 |
2019年 | 87篇 |
2018年 | 67篇 |
2017年 | 83篇 |
2016年 | 157篇 |
2015年 | 118篇 |
2014年 | 138篇 |
2013年 | 249篇 |
2012年 | 243篇 |
2011年 | 186篇 |
2010年 | 174篇 |
2009年 | 237篇 |
2008年 | 195篇 |
2007年 | 170篇 |
2006年 | 197篇 |
2005年 | 121篇 |
2004年 | 129篇 |
2003年 | 94篇 |
2002年 | 170篇 |
2001年 | 106篇 |
2000年 | 66篇 |
1999年 | 61篇 |
1998年 | 62篇 |
1997年 | 46篇 |
1996年 | 39篇 |
1995年 | 50篇 |
1994年 | 36篇 |
1993年 | 28篇 |
1992年 | 34篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 5篇 |
1985年 | 16篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有3745条查询结果,搜索用时 15 毫秒
31.
本文运用密度矩阵方程推导了V型三能级系统的荧光量子拍讯号强度,并对其结果进行了分析和讨论。 相似文献
32.
Marty W. DeGroot Chhatra Khadka Harald Rösner John F. Corrigan 《Journal of Cluster Science》2006,17(1):97-110
The thermolysis of the zinc trimethylsilylchalcogenolate complexes (N,N′-tmeda)Zn(ESiMe3)2 (E = S, 1; E = Se, 2) and (3,5-Me2-C5H3N)2Zn(ESiMe3)2 (E = S, 3; E = Se, 4) has been investigated. Solid-state thermal decomposition of complexes 1–4 above 250°C results in the formation of hexagonal ZnS and cubic ZnSe, respectively, via the liberation of TMEDA (1–2) or 3,5-lutidine (3–4) and E(SiMe3)2. Solid-state or solution thermolysis of these complexes up to 200°C produces nanocrystalline ZnS and ZnSe materials whose surface is protected by either coordinated TMEDA or 3,5-lutidine ligands. The progress of the step-wise solid-state decomposition of these complexes was monitored by thermogravimetric and single differential thermal analysis and volatile decomposition products in both solution and solid-state experiments were identified by GC/MS.Dedicated to Professor Brian F. G. Johnson on the occasion of his retirement. 相似文献
33.
载波钝化和钼酸盐后处理对不锈钢钝化膜性能的影响 总被引:1,自引:1,他引:1
一般认为交流电对金属的腐蚀过程具有加速作用,但我们发现,在直流电位基础上叠加适当波形、幅值和频率的交流电对不锈钢进行载波钝化,尔后再进行适当后处理可使钝化膜的稳定性提高,我们曾就不经后处理的载波钝化过程进行过探讨,本文着重探讨钼酸盐后处理对载波钝化膜表面状态和化学稳定性改善的作用机理。 相似文献
34.
合成和鉴定了二安替比林基-(3-羟基)苯基甲烷(DAmHM),研究了它与V(v)的显色反应。在磷酸介质中,在Mn(Ⅱ)和吐温-40存在下,DAmHM与V(V)生成橙黄色化合物,λ_(max)=480nm,ε=1.03×10 ̄6L·mol ̄(-1)·cm ̄(-1),V(v)量在0.2~1.2ug/25mL间符合比尔定律,体系灵敏度高,稳定性好,用于中草药中痕量钒的测定,结果满意。 相似文献
35.
A novel method for DNA detection is proposed that is based on the enhancement of resonance light scattering (RLS) of Ru(bpy)2PIP(V)2+ at pH 2.7. Under optimum conditions, good linear relationships were obtained in the wide concentration range of 16–5120 ng mL−1. The linear equation is I
RLS = 13.15 + 171.4 c (μg mL−1), the correlation coefficient (r) is 0.9999. The detection limit of calf thymus DNA is 5.02 ng mL−1. Plasmid DNA extracted from bacillus subtilis was determined by the method with satisfactory results. 相似文献
36.
Akira Watanabe 《Tetrahedron letters》2004,45(33):6229-6233
Oxovanadium(V)(salen) complex 4 was found to catalyze Meerwein-Ponndorf-Verley cyanation of aliphatic aldehydes with good to high enantioselectivity. This cyanation showed a positive nonlinear effect. 相似文献
37.
Yong Li Xiao-Bing Cui Ji-Qing Xu Ke-Chang Li Guang-Hua Li Qing-Xin Yang 《Journal of solid state chemistry》2005,178(1):363-369
Both the homometal cluster [P(ph4)]2[Mo2O2(μ-S)2(S2)2] (1) and [Mo2O2(μ-S)2(Et2dtc)2] (2) (Et2dtc=diethyl-dithiocarbamate) were successfully synthesized by low-temperature solid-state reactions. X-ray single-crystal diffraction studies suggest that compound (1) is a dinuclear anion cluster, and compound (2) is a dinuclear neutral cluster. The two compounds were characterized by elemental analyses, IR spectra and UV-Vis spectra. The third-order non-linear optical (NLO) properties of the clusters were also investigated and all exhibited nice non-linear absorption and self-defocusing performance with moduli of the hyperpolarizabilities 5.145×10−30 esu for (1) and 5.428×10−30 esu for (2). 相似文献
38.
Eun-Ku Lee Kwang-Deog Jung Oh-Shim Joo Yong-Gun Shul 《Reaction Kinetics and Catalysis Letters》2004,83(1):25-30
The room temperature wet catalytic oxidation was conducted in a batch reactor with V/MgO catalyst. The XRD study of the catalyst
used indicated that V/MgO could not only oxidize H2S to sulfur selectively, but also prevent the sulfidation of metal oxide
effectively at the room temperature. The XPS study indicated that the H2S oxidation with V/MgO could proceed by a redox mechanism
(V5+↔ V4+) and that V3+ formation (V4+→ V3+), was responsible for the deactivation of V/MgO.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
39.
本文合成了2,5-二(2-菲基)-[3,2-b]并二噻吩(PhTT), 表征了其基本的物理和化学性质, 制备了相应的有机薄膜晶体管. 相似文献
40.
Microwave discharges of HBr/H2/Ar and H/H2/Ar with additional do biasing of the sample were used to etch InP, GaAs, and AlGaAs at temperatures between 50–250°C. The etch rates increase by factors of 3–50 and 5–9, respectively, for HBr-and HI-based discharges over this temperature range, but display non-Arrhenius behavior. The etched surfaces became very rough above 100°C for InP with either discharge chemistry due to preferential loss of P, while GaAs and AlGaAs are more tolerant of the elevated temperature etching. The near-surface electrical properties of InP are severely degraded by etch temperatures above 100°C, while extensive hydrogen in-diffusion occurs in GaAs and AlGaAs under these conditions, leading to dopant passivation which can be reversed by annealing at 400°C. 相似文献