全文获取类型
收费全文 | 789篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
化学 | 631篇 |
晶体学 | 18篇 |
力学 | 4篇 |
数学 | 58篇 |
物理学 | 92篇 |
出版年
2020年 | 6篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 24篇 |
2012年 | 17篇 |
2011年 | 24篇 |
2010年 | 12篇 |
2009年 | 18篇 |
2008年 | 37篇 |
2007年 | 49篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 38篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 20篇 |
1997年 | 21篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 25篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有803条查询结果,搜索用时 62 毫秒
111.
The equilibrium geometry of disilyne is not linear, but is twisted. The potential surfaces of acetylene and disilyne have a critical internuclear distance between the central atoms, where the stable geometry changes from linear to twisted forms the R-dependence of the valence-shell electron energy causes the difference in the structure of the molecules. 相似文献
112.
The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth. 相似文献
113.
114.
115.
Imai T Hiraoka R Kovalenko A Hirata F 《Journal of the American Chemical Society》2005,127(44):15334-15335
Four water molecules confined in a small cavity of hen egg-white lysozyme were detected by means of the three-dimensional (3D) RISM theory, a statistical-mechanical theory of molecular solutions. This is the first theoretical realization of confined molecules in a protein without making nonsense tricks, such as placing the molecules in the space a priori. Possible impacts which the result may have on biochemistry and biophysics, including the molecular recognition, enzymatic reactions, etc., are discussed. 相似文献
116.
Treatment of 6-amino-5-arylazo-1,3-dimethyluracils with ethyl propiolate gave the corresponding Michael-type adducts, 5-arylazo-1,3-dimethyl-6-ethoxycarbonylvinylaminouracils, which on treatment with a mixture of hydrochloric acid and acetic acid caused the acid-catalyzed rearrangement accompanied with rearrangement to give rise to the corresponding 8-anilinomethyltheophylline derivatives. In the case that the arylazo group possesses an electron-releasing substituent such as methoxy, the reaction proceeded in a different way to afford 1,2-bis(theophyllin-8-yl)ethane. The presumable reaction mechanisms for the above purine syntheses were proposed. 相似文献
117.
Fumio Yoneda Kazuo Shinozuka Kinshiro Tsukuda Akira Koshiro 《Journal of heterocyclic chemistry》1979,16(7):1365-1367
The condensation of 6-arylamino- and 6-alkylaminouracils with nitrosobenzenes in a mixture of acetic anhydride and acetic acid gave the corresponding 10-aryl- and 10-alkylisoalloxazines (flavins). 相似文献
118.
The RISM-SCF and polarizable continuum model (PCM) approaches have been applied to study the conformational equilibrium of 1,2-dichloroethane (DCE) in water. Both the electron correlation effect and basis sets play an important role in the relative energies of the gauche and trans conformers in gas and solution phases. Both PCM and RISM-MP2 methods resulted in a consistent trend with the previous experimental and theoretical studies that the population of the gauche conformer increases in going from the gas phase to the aqueous solution. However, the PCM treatment could not describe the solvent effect completely in that the sign of the relative free energy of the gauche and trans forms is opposite to the most recent experimental and theoretical data, while the RISM-MP2 gives the right sign in the free energy difference. We found that the larger excess chemical potential gain (by ca. -4.1 kcal/mol) for the gauche conformer is large enough to result in the gauche preference of DCE in water, though it has to compensate for more solute reorganization energy (approximately 1.6 kcal/mol) and overcome the energy difference (approximately 1.6 kcal/mol) in the gas phase. The radial distribution functions between DCE and the nearest water shows that the electrostatic repulsion between chlorine and oxygen atoms is higher in the trans conformer than in the gauche one, while the attractive interaction between chlorine and hydrogen of water is higher in the gauche conformer. 相似文献
119.
We present a method for controlling the depth of three-dimensional (3D) images reconstructed by integral photography. Incoherent light is reflected from 3D objects, propagates through a lens array, and is captured as the first elemental images by a capturing device. The second elemental images of the 3D images are generated by numerical processing from the first elemental images in accordance with the desired depth. The optical reconstruction of 3D images at the desired depth by the second elemental images is confirmed experimentally. 相似文献
120.
Kawakita M Sasaki H Arai J Okano F Suehiro K Haino Y Yoshimura M Sato M 《Optics letters》2008,33(7):684-686
In projection-type integral imaging, positional errors in elemental images and elemental lenses affect three-dimensional (3D) image quality. We analyzed the relationships between the geometric distortion in elemental images caused by a projection lens and the spatial distortion in the reconstructed 3D image. As a result, we clarified that 3D images that were reconstructed far from the lens array were largely affected, and that the reconstructed images were significantly distorted in the depth direction at the corners of the displayed images. 相似文献