全文获取类型
收费全文 | 2098篇 |
免费 | 47篇 |
国内免费 | 3篇 |
专业分类
化学 | 1166篇 |
晶体学 | 11篇 |
力学 | 53篇 |
数学 | 292篇 |
物理学 | 626篇 |
出版年
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 23篇 |
2018年 | 20篇 |
2017年 | 11篇 |
2016年 | 40篇 |
2015年 | 27篇 |
2014年 | 35篇 |
2013年 | 88篇 |
2012年 | 77篇 |
2011年 | 71篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 74篇 |
2007年 | 74篇 |
2006年 | 67篇 |
2005年 | 86篇 |
2004年 | 71篇 |
2003年 | 78篇 |
2002年 | 64篇 |
2001年 | 60篇 |
2000年 | 70篇 |
1999年 | 49篇 |
1998年 | 22篇 |
1997年 | 40篇 |
1996年 | 49篇 |
1995年 | 36篇 |
1994年 | 29篇 |
1993年 | 34篇 |
1992年 | 42篇 |
1991年 | 31篇 |
1990年 | 51篇 |
1989年 | 39篇 |
1988年 | 40篇 |
1987年 | 24篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 30篇 |
1982年 | 36篇 |
1981年 | 28篇 |
1980年 | 29篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 29篇 |
1976年 | 20篇 |
1975年 | 26篇 |
1974年 | 21篇 |
1973年 | 31篇 |
1971年 | 12篇 |
排序方式: 共有2148条查询结果,搜索用时 343 毫秒
41.
42.
43.
44.
45.
The metals vanadium, chromium and molybdenum may be separated from the other constituents of steel by passing an acetate buffered solution of the steel through a strongly basic onion exchanger and selectively eluting the above metals from the resin column with aqueous solutions of 0.6 N sodium hydroxide, 8 N hydrochloric acid and 1 N hydrochloric acid, respectively. 相似文献
46.
A general approach for the allylation of aldehydes using stable, air-tolerant camphor-based chiral allylboronates under Sc(OTf)3 catalysis is described. This practical methodology provides both syn and anti propionate units and other homoallylic alcohols with very high levels of diastereo- and enantioselectivity for several substrates, including functionalized aliphatic aldehydes useful toward the elaboration of complex natural products. 相似文献
47.
48.
49.
Reza Dabestani Robert D. Hall Robert H. Sik Colin F. Chignell 《Photochemistry and photobiology》1990,52(5):961-971
The photochemistry (Type I and II) of anthralin and its photo-oxidation product 1,8-dihydroxyanthraquinone (1,8-DHAQ) has been studied in ethanol, acetonitrile and dimethylsulfoxide using spin-trapping and direct detection of singlet oxygen (1O2) luminescence techniques. In ethanol, where it exists in its neutral form (AN), anthralin does not undergo either Type I or II reactions upon UV-irradiation. In contrast, irradiation of anthralin in acetonitrile, a solvent in which anthralin is partially converted to its corresponding mono-anion (AN-), generates both superoxide and singlet oxygen. Irradiation of anthralin in dimethylsulfoxide, where the AN- form is present in substantial quantity, generates superoxide and solvent derived radicals but no detectable singlet oxygen. UV-irradiation of 1,8-DHAQ in ethanol and acetonitrile produces both superoxide and singlet oxygen in significant yields. In dimethylsulfoxide, on the other hand, only superoxide and solvent derived radicals are observed. The 1O2 quantum yield for AN- and 1,8-DHAQ in acetonitrile were determined to be 0.14 and 0.88 relative to rose bengal in the same solvent. These findings suggest that the AN photosensitization occurs via Type I and II pathways, is solvent dependent and involves AN- as well as its oxidation product 1,8-DHAQ, which is a more potent generator of both singlet oxygen and superoxide. 相似文献
50.
Shoji Mori Toyoji Kakuchi Anne Buyle Padias H. K. Hall 《Journal of polymer science. Part A, Polymer chemistry》1990,28(3):551-558
Six new gem-dicyanocyclobutanes containing carbomethoxy and hydroxyl/acetoxy functions were synthesized by cycloaddition of the appropriate vinyl ethers or alkoxystyrenes to methyl β,β-dicyanoacrylate. They proved to be too thermally labile to allow polycondensation to potentially piezoelectric linear polyesters. 相似文献