全文获取类型
收费全文 | 612篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 471篇 |
晶体学 | 8篇 |
力学 | 6篇 |
数学 | 11篇 |
物理学 | 127篇 |
出版年
2022年 | 4篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 10篇 |
2013年 | 35篇 |
2012年 | 24篇 |
2011年 | 32篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 28篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 5篇 |
1969年 | 6篇 |
1968年 | 2篇 |
排序方式: 共有623条查询结果,搜索用时 625 毫秒
1.
Xinyu Chen Yoshiro Oro Kenta Tanaka Norimichi Takenaka Hiroshi Bandow 《Analytical sciences》2004,20(7):1019-1023
A new stripping coil for the collection of nitrogen dioxide (NO2) has been developed to increase its versatility and efficiency. Nitrogen dioxide measurements based on quantitative collection through a reaction coil into an alkaline solution has been examined. Nitrogen dioxide is collected in a 0.1 N NaOH solution. This collection system has an efficiency of nearly 100%. The absorbed nitrogen dioxide has been measured by fluorescence detection with sub-ppbv detection limits. The excitation wavelength at 360 nm and the produced emission wavelength at 405 nm were suitable for nitrite ion measurements. 相似文献
2.
Yoshiro Masuyama Takanori SugaAkiko Watabe Yasuhiko Kurusu 《Tetrahedron letters》2003,44(14):2845-2847
2-Propenyl tin species, prepared from 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide in dichloromethane, causes nucleophilic addition to aldehydes to produce the corresponding homoallylic alcohols. 相似文献
3.
Muonium in liquid SiCl has been observed for the first time at low temperature (−65°C) The observed polarization of muonium
is as much as 25% of the total spin polarization and shows a fast relaxation rate. 相似文献
4.
5.
6.
7.
8.
Chiaki Azuma Takao Mitsuboshi Kohei Sanui Naoya Ogata 《Journal of polymer science. Part A, Polymer chemistry》1980,18(3):781-797
cis-1,4-Polybutadiene and polypentenamer having pendant functional groups such as formyl, aldoxime, hydroxymethyl, or cinnamoyloxymethyl groups have been prepared, and some of their properties were investigated in terms of structural effect on physical properties of these polymers. cis-1, 4-Polybutadiene and polypentenamer having a different content of formyl group were prepared by the hydroformylation reaction with rhodium catalyst under mild conditions. The pendant formyl group was reduced to a hydroxymethyl group by using various reducing agents such as sodium borohydride or sodium trimethoxyborohydride which were effective to avoid a crosslinking reaction among the formyl groups. Glass transition temperature of polypentenamer having hydroxymethyl groups increased with increasing the content of the hydroxymethyl groups in the polymer. Cinnamoyl group was introduced into the polypentenamer having hydroxymethyl groups by reacting with cinnamoyl chloride so as to prepare a photosensitive rubber. The relationships between the photosensitivity of the cinnamoylated polypentenamer and the mobility of polymer main chains have been elucidated. A linear relationship between the photodimerization rate constant and the difference between ultraviolet (UV) irradiation temperature and the glass transition temperature of the polymer was found. It has become apparent that the photosensitivity of cinnamoylated polypentenamer can be estimated by the glass transition temperature of the original polymer, UV irradiation temperature, activation energy of the dimerization, and γ, which is a coefficient of the relationship between the photosensitive group concentration and the glass transition temperature of the polymer. 相似文献
9.
Rijssenbeek JT Saito T Malo S Azuma M Takano M Poeppelmeier KR 《Journal of the American Chemical Society》2005,127(2):675-681
The related parameters of cation size and valence that control the crystallization of Sr(3)CaRu(2)O(9) into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr(3)MRu(2)O(9) stoichiometries yield multiphasic mixtures for M = Ni(2+), Mg(2+), and Y(3+), whereas pseudocubic perovskites result for M = Cu(2+) and Zn(2+). For A-site substitutions, an ordered perovskite structure results for Sr(3-x)Ca(x)CaRu(2)O(9), with 0 = x = 1.5. In contrast, Ba(2+) substitution for Sr(2+) is accompanied by a phase change to a hexagonal BaTiO(3) structure type. At high pressures and temperatures, a 1:2 B-site-ordered perovskite structure is stabilized for Sr(3-x)Ba(x)CaRu(2)O(9), with 0 = x = 3. The scarcity of B-site-ordered perovskite ruthenates at ambient pressure and the metastable nature of the high-pressure phases underscore the strict size and valence requirements that must be met by the constituent cations to achieve these uncommon ordered structures. 相似文献
10.
Jun-ichi Azuma Nam-Hun Kim Laurent Heux Roger Vuong Henri Chanzy 《Cellulose (London, England)》2000,7(1):3-19
The cellulose system of the viscous fibrous cellulosic polysaccharide (viscan) in the viscin tissue of the European mistletoe, Viscum album L., was analyzed by chemical and physicochemical techniques including sugar analysis, optical and transmission electron microscopy, X-ray and electron diffraction together with solid state CP/MAS 13C-NMR spectroscopy. The results confirmed that in the elongated thin viscin cells, the cellulose microfibrils (having a diameter of around 3 nm) were tightly coiled with their axes perpendicular to the long axis of the cell. Upon stretching these cells became deformed by more than a hundred fold. In such a deformation, the cellulose microfibrils became unwound to be perfectly aligned along the stretching direction. Based on solid-state CP/MAS 13C-NMR spectroscopic analysis of the viscin tissue, it was found that its cellulose consisted of I and I polymorphs in the ratio 1:1. 相似文献