全文获取类型
收费全文 | 3739篇 |
免费 | 61篇 |
国内免费 | 17篇 |
专业分类
化学 | 2302篇 |
晶体学 | 26篇 |
力学 | 75篇 |
数学 | 599篇 |
物理学 | 815篇 |
出版年
2022年 | 30篇 |
2021年 | 37篇 |
2020年 | 58篇 |
2019年 | 41篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 45篇 |
2015年 | 51篇 |
2014年 | 47篇 |
2013年 | 164篇 |
2012年 | 162篇 |
2011年 | 178篇 |
2010年 | 99篇 |
2009年 | 87篇 |
2008年 | 153篇 |
2007年 | 189篇 |
2006年 | 177篇 |
2005年 | 173篇 |
2004年 | 169篇 |
2003年 | 139篇 |
2002年 | 125篇 |
2001年 | 84篇 |
2000年 | 96篇 |
1999年 | 51篇 |
1998年 | 65篇 |
1997年 | 53篇 |
1996年 | 62篇 |
1995年 | 63篇 |
1994年 | 50篇 |
1993年 | 70篇 |
1992年 | 43篇 |
1991年 | 40篇 |
1990年 | 44篇 |
1989年 | 45篇 |
1988年 | 37篇 |
1987年 | 42篇 |
1986年 | 41篇 |
1985年 | 58篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 34篇 |
1981年 | 37篇 |
1980年 | 36篇 |
1979年 | 26篇 |
1978年 | 30篇 |
1977年 | 39篇 |
1976年 | 45篇 |
1975年 | 49篇 |
1974年 | 41篇 |
1973年 | 45篇 |
排序方式: 共有3817条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
M S Patterson S J Madsen B C Wilson 《Journal of photochemistry and photobiology. B, Biology》1990,5(1):69-84
Singlet oxygen (1O2) is thought to be the cytotoxic agent in photodynamic therapy (PDT) with current photosensitizers. Direct monitoring of 1O2 concentration in vivo would be a valuable tool in studying biological response. Attempts were made to measure 1O2 IR luminescence during PDT of cell suspensions and two murine tumour models using the photosensitizers Photofrin II and aluminium chlorosulphonated phthalocyanine. Instrumentation was virtually identical to that devised by Parker in the one positive report of in vivo luminescence detection in the literature. Despite the fact that our treatments caused cell killing and tissue necrosis, we were unable to observe 1O2 emission under any conditions. We attribute this negative result to a reduction in 1O2 lifetime in the cellular environment. Quantitative calibration of our system allowed us to estimate that the singlet oxygen lifetime in tissue is less than 0.5 microsecond. Some technical improvements are suggested which would improve detector performance and perhaps make such measurements feasible. 相似文献
7.
Toy and Stringham recently reported [1] the synthesis of N2F+5 (CF3)3CO-, a salt containing the novel pentafluorohydrazinium cation. This cation would be of significant academic and practical interest [2] since it would constitute the first known example of a substituted NF+4 cation, i.e. an NF+4 cation in which a fluorine ligand is replaced by an NF2 group. According to the authors of [1], N2F+5(CF3)3CO- was formed in a very unusual reaction involving the transfer of a fluorine cation from (CF3)3COF to N2F4 according to: 相似文献
8.
Extraction and subsequent recovery, in four separate fractions, of naphthenic acids, alkylphenols, pyrrollic compounds and nitrogen bases can be made from petroleum products using macroporous ion-exchange resins. Distinctive features of the technique are the use of dissolved gases in polar solvents as eluants and the application of the carbonate form of anion-exchange resins. The transition metal form of a macroreticular cation exchanger is shown to extract ligands from non-aqueous systems and a specific application to petroleum analysis is given. 相似文献
9.
10.