全文获取类型
收费全文 | 1039篇 |
免费 | 29篇 |
国内免费 | 11篇 |
专业分类
化学 | 874篇 |
晶体学 | 13篇 |
力学 | 9篇 |
数学 | 69篇 |
物理学 | 114篇 |
出版年
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 40篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 42篇 |
2008年 | 54篇 |
2007年 | 50篇 |
2006年 | 67篇 |
2005年 | 60篇 |
2004年 | 67篇 |
2003年 | 46篇 |
2002年 | 42篇 |
2001年 | 11篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 27篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 26篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 5篇 |
排序方式: 共有1079条查询结果,搜索用时 15 毫秒
71.
Yukiji Shimojima Hiroshi Hayashi Tadaaki Ooka Mitsuru Shibukawa Yoichi Iitaka 《Tetrahedron letters》1982,23(51):5435-5438
The structures of a novel gastroprotective substance AI-77-B and its analogues AI-77-C, D, F and G, which are produced by Bacillus pumilus, are described. Five of the asymmetric centers of AI-77-B have S absolute stereochemistry confirmed by X-ray in combination with chemical studies. 相似文献
72.
73.
Yoshio Teki Takeji Takui Mitsuru Hirai Koichi Itoh Hiizu Iwamura 《Chemical physics letters》1982,89(3):263-267
Optically detected ENDOR and electron—nuclear—nuclear triple resonance of 17O were measured via phosphorescence from 3(nπ*) benzil in benzophenone-d10 crystals at high magnetic field. The n and π* spin densities on the oxygen atom are 0.201 and 0.092, respectively, the angle between the two CO bonds being 150°. 相似文献
74.
The bioultrasonic spectroscopy system was employed for measurements of velocity and attenuation coefficient of glucose solutions in the VHF/UHF range. The relation between the slope of the square of velocity and the relaxation parameters, and the relation between the frequency exponent on attenuation coefficient and the relaxation parameters are investigated. In order to carry out numerical calculations, a model for a single relaxation process is employed, wherein the attenuation coefficient is expressed as (A/( 1 + (f/falpha)2) + B)f2 where falpha is the attenuation relaxation frequency, and A and B are constants. The numerical calculations show that the slope of the square of the velocity is determined uniquely by the velocity relaxation frequency fv and v(infinity)2 - v(0)2 where v0 is the zero-frequency velocity and v(infinity) is the infinite-frequency velocity, and that the frequency exponent on the attenuation coefficient is determined uniquely by falpha and A/B. For experimental considerations, the velocities and the attenuation coefficients of 5, 15, and 25% concentration aqueous solutions of glucose were measured in the frequency range 20 to 700 MHz. The data for the 5 and 15% aqueous solutions can be explained using the single relaxation model. However, the data for the 25% aqueous solution suggest the existence of multirelaxation processes. 相似文献
75.
Inukai J Wakisaka M Yamagishi M Itaya K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(18):7507-7511
Hydroquinone (HQ) adlayers were formed on Pt(111) in HF solution and in a vacuum. By using scanning tunneling microscopy (STM) in solution, it was revealed that HQ formed an ordered structure on Pt(111) with a strong attractive interaction between two adjacent hydroxyl groups in neighboring HQ molecules. After the sample was transferred into a vacuum, low-energy electron diffraction (LEED) measurement was performed, which showed that the (2.56 x 2.56)R16 degrees incommensurate structure of the HQ adlayer was formed in solution. The HQ adlayer on Pt(111) was formed also by vapor deposition, and the identical (2.56 x 2.56)R16 degrees adlayer structure was found by LEED and STM in a vacuum. 相似文献
76.
77.
78.
Hayashi Y Tsuboi W Shoji M Suzuki N 《Journal of the American Chemical Society》2003,125(37):11208-11209
High pressure induced by water-freezing has been successfully applied to the direct catalytic asymmetric-three component List-Barbas-Mannich reaction, in which higher yield and better enantioselectivity can be realized than those from the reaction at room temperature under 0.1 MPa. 相似文献
79.
Mitsuru Musha Yosuke Tamura Ken’ichi Nakagawa Ken-ichi Ueda 《Optics Communications》2007,272(1):211-216
We have developed a practical and precise frequency measurement system at 1.5 μm telecommunication band. An electro-optic-modulator based optical frequency comb is phase-locked to a dither-free acetylene-stabilized laser to realize an optical frequency comb with frequency uncertainty of 10 kHz (5 × 10−11) and the linewidth of 15 kHz. The present frequency comb can be also used as an optical frequency reference grid defined by ITU-T (International Telecommunication Union, Telecommunication Standardization Sector). Using the present frequency measurement system, we have demonstrated the first optical frequency measurement of 12C16O overtone absorption lines around 1.56 μm with the uncertainty of lower than 900 kHz. 相似文献
80.