全文获取类型
收费全文 | 4079篇 |
免费 | 82篇 |
国内免费 | 21篇 |
专业分类
化学 | 2852篇 |
晶体学 | 43篇 |
力学 | 50篇 |
数学 | 187篇 |
物理学 | 1050篇 |
出版年
2022年 | 18篇 |
2021年 | 36篇 |
2020年 | 49篇 |
2019年 | 58篇 |
2018年 | 42篇 |
2017年 | 23篇 |
2016年 | 60篇 |
2015年 | 69篇 |
2014年 | 68篇 |
2013年 | 166篇 |
2012年 | 178篇 |
2011年 | 229篇 |
2010年 | 106篇 |
2009年 | 143篇 |
2008年 | 216篇 |
2007年 | 222篇 |
2006年 | 225篇 |
2005年 | 188篇 |
2004年 | 181篇 |
2003年 | 166篇 |
2002年 | 179篇 |
2001年 | 131篇 |
2000年 | 106篇 |
1999年 | 69篇 |
1998年 | 51篇 |
1997年 | 56篇 |
1996年 | 52篇 |
1995年 | 41篇 |
1994年 | 53篇 |
1993年 | 62篇 |
1992年 | 74篇 |
1991年 | 58篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 43篇 |
1987年 | 56篇 |
1986年 | 49篇 |
1985年 | 56篇 |
1984年 | 52篇 |
1983年 | 40篇 |
1982年 | 29篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 48篇 |
1978年 | 42篇 |
1977年 | 25篇 |
1976年 | 31篇 |
1975年 | 24篇 |
1974年 | 28篇 |
1973年 | 22篇 |
排序方式: 共有4182条查询结果,搜索用时 15 毫秒
21.
22.
A linear correlation between the NQR frequency of the terminal iodine atom and the corresponding I-I bond length in I3? was found in several compounds containing triiodide anions. A simple extended Huckel MO calculation suggested that such a correlation can be used to check the validity of wavefunctions of iodine. 相似文献
23.
Tanaka M Nakamura M Ikeda T Ikeda K Ando H Shibutani Y Yajima S Kimura K 《The Journal of organic chemistry》2001,66(21):7008-7012
Synthetic procedures for monoazathiacrown ethers were explored, and monoazatrithia-12-crown-4, monoazatetrathia-15-crown-5, and monoazapentathia-18-crown-6 were obtained in moderate yields by the reaction of bis(2-chloroethyl)amine with the appropriate dithiols in the presence of lithium hydroxide in THF. To evaluate metal-ion binding properties of the monoazathiacrown ethers by solvent extraction, lipophilic dodecyl and dodecanoyl groups were incorporated onto the monoazathiacrown ethers. The solvent extraction experiments suggested that monoazathiacrown ethers have Ag(+) and Hg(2+) selectivities and that the relative selectivity between Ag(+) and Hg(2+) depends on their nitrogen atom properties and numbers of sulfur atoms reflecting the respective affinities of nitrogen and sulfur atoms to Hg(2+) and Ag(+). An interesting ability to bind Mg(2+) was observed in the case of N-dodecyl monoazatrithia-12-crown-4. 相似文献
24.
25.
26.
27.
We investigate the construction of long, stable hybrid threadlike micelles consisting of polyelectrolytes and oppositely charged surfactants in aqueous solution and examine the physicochemical features such as their structure and viscoelastic behavior in aqueous solution. The most important point for their construction is the careful control of interactions, especially electrostatic interactions, caused between the surfactants and polyelectrolytes. Incorporated polyelectrolytes are fully extended in these hybrid threadlike micelles irrespective of the molecular weight of the polymer. The viscoelastic behavior of the hybrid threadlike micellar solution is similar to that of ordinary threadlike micellar systems consisting of low‐molecular‐weight substances. However, the inclusion of polymers in the micelles causes differences in their mechanical properties. 相似文献
28.
Junji Furukawa Eiichi Kobayashi Morio Nakamura 《Journal of polymer science. Part A, Polymer chemistry》1974,12(12):2789-2799
The effect of ultraviolet irradiation on the terpolymerization was investigated. In the terpolymerizations of sulfur dioxide–butene-1–acrylonitrile, sulfur dioxide–butene-1–n-butyl acrylate, and maleic anhydride–allyl chloride–acrylonitrile systems, the composition of the terpolymers prepared under ultraviolet irradiation was different from those prepared in the dark. The unit content of sulfur dioxide and butene-1 or of maleic anhydride and allyl chloride in the terpolymer increased under ultraviolet irradiation. The nature of the growing end under ultraviolet irradiation is supposed to be the same as that of the dark polymerization on the basis of the same solvent effect on the terpolymer composition, the rate of polymerization and the molecular weight of polymer. The experimental results suggest that the complex between sulfur dioxide and butene-1 or maleic anhydride and allyl chloride might be excited by ultraviolet light and the excited complex may participate in the terpolymerization. 相似文献
29.
Yoshiharu Yamane Yozo Nakamura Hiroyuki Okamoto Hiroshi Ooshima Jyoji Kato 《Applied biochemistry and biotechnology》1995,50(3):317-322
Effects of pH and dissolved oxygen concentration on batchwise riboflavin production by a 5-fluorouracil (5-FU)-resistant mutant
ofArthrobacter sp. were investigated. The reaction was carried out in a jar fermentor. The optimal pH of culture medium was around 7.3.
Dissolved oxygen concentration was almost constant during fermentation at 600 rpm of agitation rate. Production of riboflavin
reached a maximum of 160 mg/L after 70 h fermentation under the agitation rate of 600 rpm, aeration rate of 1.0 L/min, and
pH 7.0. 相似文献
30.
To detect a lectin from soybean, an electrochemical procedure was developed by the use of a labeling of galactosamine. Because the lectin has binding sites to galactosamine, galactosamine labeled with daunomycin having electroactivity was prepared. When labeled galactosamine (LG) combines with lectin, the part of daunomycin is taken in the binding sites of the lectin and becomes electroinactive. Therefore, the concentration of the lectin can be estimated by measuring the peak current of the LG. On the other hand, a competitive reaction to the lectin of galactosamine and the LG makes a detection of galactosamine possible. This method has merit that does not require a separation procedure of the free LG from the bound one. An effect of length of spacer between daunomycin and galactosamine was also investigated. It was found that adsorption of reagent on the electrode increased due to introduction of the spacer. Furthermore, the electrode response of the LG was influenced by the type of the spacer. 相似文献