全文获取类型
收费全文 | 11595篇 |
免费 | 576篇 |
国内免费 | 269篇 |
专业分类
化学 | 7899篇 |
晶体学 | 86篇 |
力学 | 389篇 |
综合类 | 39篇 |
数学 | 1642篇 |
物理学 | 2385篇 |
出版年
2023年 | 86篇 |
2022年 | 208篇 |
2021年 | 306篇 |
2020年 | 265篇 |
2019年 | 288篇 |
2018年 | 250篇 |
2017年 | 185篇 |
2016年 | 399篇 |
2015年 | 384篇 |
2014年 | 450篇 |
2013年 | 747篇 |
2012年 | 751篇 |
2011年 | 817篇 |
2010年 | 524篇 |
2009年 | 564篇 |
2008年 | 663篇 |
2007年 | 611篇 |
2006年 | 553篇 |
2005年 | 472篇 |
2004年 | 439篇 |
2003年 | 351篇 |
2002年 | 392篇 |
2001年 | 281篇 |
2000年 | 210篇 |
1999年 | 157篇 |
1998年 | 112篇 |
1997年 | 104篇 |
1996年 | 101篇 |
1995年 | 87篇 |
1994年 | 96篇 |
1993年 | 83篇 |
1992年 | 82篇 |
1991年 | 67篇 |
1990年 | 68篇 |
1989年 | 52篇 |
1988年 | 70篇 |
1987年 | 48篇 |
1985年 | 61篇 |
1984年 | 53篇 |
1983年 | 60篇 |
1982年 | 49篇 |
1981年 | 53篇 |
1979年 | 47篇 |
1978年 | 49篇 |
1977年 | 50篇 |
1976年 | 64篇 |
1975年 | 56篇 |
1974年 | 63篇 |
1973年 | 71篇 |
1972年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
71.
采用从头计算方法,计算了反式和顺式聚乙炔的氢原子在垂直于聚乙炔分子面方向振动的红外光谱,计算表明,Gibson等用红外吸收实验所测得的谱线的确是聚乙炔的CH面外振动产生的谱线,经100℃长时间加热后,顺式聚乙炔变为反式聚炔,但波数为740cm^-1的谱级仍保留5%的强度。 相似文献
72.
通过考虑同类核子相干对间的四极相互作用,在IBM2中对Ce偶-偶同位素^128Ce-^138Ce的低激发态能谱和E2跃迁几率及分支比进行了理论分析,计算结果有效地改善了IBM中这些核的γ带能谱的Staggering现象描述,与实验观察到的低激发态结果基本一致。 相似文献
73.
Frédéric Coquel Thierry Gallouët Jean-Marc Hérard Nicolas Seguin 《Comptes Rendus Mathematique》2002,334(10):927-932
Closure laws for interfacial pressure and interfacial velocity are proposed within the frame work of two-pressure two-phase flow models. These enable us to ensure positivity of void fractions, mass fractions and internal energies when investigating field by field waves in the Riemann problem. To cite this article: F. Coquel et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 927–932. 相似文献
74.
Marie‐France Llauro Julien Loiseau Fernande Boisson Frdric Delolme Catherine Ladavire J. Claverie 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5439-5462
Low‐molecular‐weight poly(acrylic acid) (PAA) was synthesized by reversible addition fragmentation chain transfer polymerization with a trithiocarbonate as chain‐transfer agent (CTA). With a combination of NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, the PAA end‐groups of the polymer were analyzed before and after neutralization by sodium hydroxide. The polymer prior to neutralization is made up of the expected trithiocarbonate chain‐ends and of the H‐terminated chains issued from a reaction of transfer to solvent. After neutralization, the trithiocarbonates are transformed into thiols, disulfides, thiolactones, and additional H‐terminated chains. By quantifying the different end‐groups, it was possible to demonstrate that fragmentation is the rate limiting step in the transfer reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5439–5462, 2004 相似文献
75.
F. F. Éfendiev 《Mathematical Notes》1992,51(2):204-207
Translated from Matematicheskie Zametki, Vol. 51, No. 2, pp. 139–143, February, 1992. 相似文献
76.
77.
DaXinSHI YaQingFENG ShunHeZHONG 《中国化学快报》2005,16(5):685-687
Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu/CdS-TiO2/SiO2. 相似文献
78.
Triterpenoid Constituents of Huperzia miyoshiana 总被引:1,自引:0,他引:1
Thirteen triterpenoids, including three new ones, miyoshianois A (1), B (2) and C (3), were isolated from Huperzia miyoshiana. The structures of these new compounds were established as 3-O-dihydroferuloyltohogenol (1), 16-oxo-3β,21β-dihydrox-y-serrat-14-en-24-ferulate (2) and 16-oxo-3a, 21β-dihydroxy-serrat-14-en-24-ferulate (3), respectively, on the basis of their spectroscopic analysis. 相似文献
79.
A. F. G. Monte M. A. G. Soler S. W. da Silva B. B. D. Rodrigues P. C. Morais A. A. Quivy J. R. Leite 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):466
We have investigated the influence of vicinal GaAs substrates on the optical and electronic properties of InGaAs/GaAs quantum wells (QWs). A single In0.10Ga0.90As QW was grown by molecular-beam epitaxy on a vicinal GaAs(0 0 1) substrate with a miscut angle of 0° (nominal), 2°, 4° and 6° towards [1 1 0]. The carrier diffusion was obtained by a micro-photoluminescence scan technique that permits to observe the effective diffusion length characterized by the lateral spread of carriers in the QW followed by radiative recombination. The carrier diffusion length was obtained parallel (L||) and perpendicular (L) to the atomic steps. The diffusion length decreases as the temperature increases up to 100 K. Above this temperature we found different behaviours that depend on the sample miscut angle. 相似文献
80.