全文获取类型
收费全文 | 725篇 |
免费 | 17篇 |
国内免费 | 26篇 |
专业分类
化学 | 431篇 |
晶体学 | 20篇 |
力学 | 21篇 |
综合类 | 1篇 |
数学 | 59篇 |
物理学 | 236篇 |
出版年
2022年 | 23篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 32篇 |
2013年 | 28篇 |
2012年 | 40篇 |
2011年 | 58篇 |
2010年 | 37篇 |
2009年 | 25篇 |
2008年 | 36篇 |
2007年 | 29篇 |
2006年 | 27篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 15篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 15篇 |
1993年 | 20篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1937年 | 4篇 |
排序方式: 共有768条查询结果,搜索用时 15 毫秒
751.
For a sample with plasma frequency varying exponentially from ωps at the surface to a larger value ωpb in the bulk, and moderate damping, we find, contrary to other calculations, that the long wavelength surface plasmon dispersion has a single branch that is reentrant at ω = ωps. 相似文献
752.
A convenient synthesis for varions (Z)-1-alkanesulfinyl-2-phenylethenes has been developed. This involves addition of different sodium thiolates to phenylacetylene in ethanol, and oxidation of the resulting (Z)-1-alkanesulfenyl-2-phenylethenes [(Z)-styryl alkyl thioethers] with sodium metaperiodate supported on acidic alumina. The corresponding sulfones can be obtained by oxidation of these (Z)-styryl alkyl thioethers with hydrogen peroxide in glycial acetic acid, or, alternatively by reduction of the β-iodostyrylsulfones with zinc in acetic acid. These β-iodostyrylsulfones were obtained by addition of the corresponding sulfonyl iodides to phenylacetylene under the catalytic action of cupric chloride and triethylaminium chloride. 相似文献
753.
Ohne Zusammenfassung 相似文献
754.
A nonplanar, reentrant two-spherical-mirror ring cavity is demonstrated. It is compact and free of astigmatism. Unidirectional operation is achieved by use of reciprocal and nonreciprocal polarization rotators to differentiate round-trip loss. A single-frequency green laser is generated by intracavity frequency doubling. Amplitude noise as low as 0.25% is achieved. 相似文献
755.
We will study the cosmological implications of the five dimensional scalar–vector and scalar-Kalb–Ramond model. In particular, a new set of Bianchi type I power-law analytic solution will be obtained for this model. The cosmic no-hair conjecture can be shown to break down in the presence of the scalar–vector and scalar-Kalb–Ramond couplings. The effect of the Kalb–Ramond field in the presence of the power-law solution will be shown explicitly. We will also show that the presence of a phantom field does, however, destabilize the corresponding Bianchi type I power-law inflationary solutions. 相似文献
756.
Chi-Hua Tung Yen-Ta Lu Wei-Ting Kao Jen-Wei Liu Yi-Hsuan Lai Shinn-Jong Jiang Hao-Ping Chen Tzenge-Lien Shih 《中国化学会会志》2020,67(7):1254-1262
Three novel naphthalimide-based derivatives were synthesized and tested in vitro as anticancer agents. Our previous report of the C4-benzazole 1,8-naphthalimide derivatives showed good inhibition against murine melanoma. We aimed to synthesize more potent agents and found that compound 5 reported in this article behaved 5- to 10-fold potency than our previous best results. The unique structure of compound 5 consisted of a naphthalimide framework in which C4 position was linked with an ethylenediamine group where the amino group was coupled with a 2-piconic acid moiety. Compound 5 exhibited the most potent inhibitory activity toward human DNA topoisomerase II proteins with IC50 value (2.6 ± 0.1 μM) against murine B16F10 melanoma cells among the three target compounds synthesized in this study. In accordance with this finding, the results of molecular docking also revealed that compound 5 has the highest affinity with human DNA topoisomerase II among the selected compounds. Compound 5 , therefore, has high potential for becoming a lead compound. 相似文献
757.
Two novel indium silicates, K5In3Si7O21 (1) and K4In2Si8O21 (2), have been synthesized by a flux-growth method and characterized by single-crystal X-ray diffraction. The structure of 1 consists of siebener single chains of corner-sharing SiO4 tetrahedra running along the b axis linked via corner-sharing by In2O9 face-sharing octahedral dimers and InO5 trigonal bipyramids to form a 3D framework. The structure of 2 consists of a 3D silicate framework containing 6- and 14-ring channels. InO5 square pyramids are located within the 14-ring channels sharing corners with the silicate framework. The solid-state 29Si MAS NMR spectrum of compound 1 was recorded; it shows the influence of the indium atoms in the second coordination sphere of the silicon on the chemical shift. Crystal data: 1, orthorhombic, Pna21 (No. 33), a = 12.4914(3) A, b = 16.8849(3) A, c = 10.2275(2) A, V = 2157.1(1) A3 and Z = 4; 2, monoclinic, P21/n (No. 14), a = 8.4041(3) A, b = 11.4919(4) A, c = 10.4841(3) A, beta = 90.478(2) degrees , V = 1012.5(1) A3 and Z = 2. 相似文献
758.
Takanori Iino Po-Lin Li Wen-Zhe Wang Jia-Huei Deng Yun-Chang Lu Fu-Jen Kao Yoichiroh Hosokawa 《Applied Physics A: Materials Science & Processing》2014,116(1):389-393
When an intense femtosecond laser is focused in a cell culture medium, shock wave, stress wave, and cavitation bubble are generated at the laser focal point. Cell–cell adhesion can be broken at the cellular level by the impacts of these factors. We have applied this breaking of the adhesion to an estimation of the cell–cell adhesion strength. In this application, it is important to identify which of these factors is the dominant factor that breaks the adhesion. Here we investigated this issue using streptavidin-coated microbeads adhering to a biotin-coated substrate as a mimic of the cell–cell adhesion. The results indicated that the break was induced mainly by the stress wave, not by the impact of the cavitation bubble. 相似文献
759.
Kao MT Chen JH Chu YY Tseng KP Hsu CH Wong KT Chang CW Hsu CP Liu YH 《Organic letters》2011,13(7):1714-1717
A new synthesis of 5,10,15-hexaaryltruxene derivatives has been developed. Experimental observations and theoretical calculations confirmed that the presence of aryl substituents on the sp(3)-hybridized bridge carbon atoms had an effect on the photophysical properties of the truxene core. Interestingly, the cage compound 11 possessing a distorted truxene core was verified by X-ray diffraction analysis; the influence of the peripheral aryl substituents on the photophysical properties of the truxene core was diminished because of its molecular rigidity. 相似文献
760.
Well-ordered periodic mesoporous benzene-silicas functionalized with a high loading of pendant carboxylic acid groups (up to 60 mol% based on silica) have been successfully synthesized via co-condensation of 1,4-bis(triethoxysilyl)benzene and carboxyethylsilanetriol sodium salt using Pluronic P123 as a template and KCl as an additive. 相似文献