全文获取类型
收费全文 | 4580篇 |
免费 | 149篇 |
国内免费 | 26篇 |
专业分类
化学 | 3294篇 |
晶体学 | 34篇 |
力学 | 83篇 |
综合类 | 1篇 |
数学 | 344篇 |
物理学 | 999篇 |
出版年
2021年 | 42篇 |
2020年 | 66篇 |
2019年 | 53篇 |
2018年 | 52篇 |
2017年 | 52篇 |
2016年 | 113篇 |
2015年 | 84篇 |
2014年 | 107篇 |
2013年 | 202篇 |
2012年 | 242篇 |
2011年 | 243篇 |
2010年 | 143篇 |
2009年 | 140篇 |
2008年 | 268篇 |
2007年 | 275篇 |
2006年 | 268篇 |
2005年 | 259篇 |
2004年 | 197篇 |
2003年 | 177篇 |
2002年 | 169篇 |
2001年 | 104篇 |
2000年 | 91篇 |
1999年 | 79篇 |
1998年 | 56篇 |
1997年 | 42篇 |
1996年 | 53篇 |
1995年 | 51篇 |
1994年 | 33篇 |
1993年 | 45篇 |
1992年 | 60篇 |
1991年 | 62篇 |
1990年 | 35篇 |
1989年 | 41篇 |
1988年 | 53篇 |
1987年 | 41篇 |
1986年 | 37篇 |
1985年 | 75篇 |
1984年 | 59篇 |
1983年 | 35篇 |
1982年 | 55篇 |
1981年 | 40篇 |
1980年 | 37篇 |
1979年 | 56篇 |
1978年 | 35篇 |
1977年 | 41篇 |
1976年 | 39篇 |
1975年 | 31篇 |
1974年 | 26篇 |
1973年 | 25篇 |
1969年 | 23篇 |
排序方式: 共有4755条查询结果,搜索用时 42 毫秒
31.
32.
Bond IA Budding E Conway MJ Fenton KB Fujii H Fujii Z Fujimoto M Hasegawa H Hayashida N Honda M Hotta N Humble JE Kabe S Kasahara K Kifune T Masaike A Matsubara Y Mitsui K Miura Y Mori M Murakami K Muraki Y Nagano M Nakamura K Nakamura T Norris PM Ohashi Y Okada A Saito T Sakata M Sato H Shibata S Shima M Storey JR Tanimori T Teshima M Torii S Uchino K Watase Y Woodhams MD Yamamoto Y Yock PC Yuda T 《Physical review letters》1988,61(20):2292-2295
33.
34.
K Ogawa M Nishii J Inagaki F Nohara T Saito T Itaya T Fujii 《Chemical & pharmaceutical bulletin》1992,40(5):1315-1317
The synthesis of 8-methylguanine 7-oxide (3) was accomplished via a "phenacylamine route", which started from condensation of alpha-(4-methoxybenzylamino)propiophenone (6), prepared by coupling of alpha-bromopropiophenone (4) and 4-methoxybenzylamine (5), with 2-amino-6-chloro-5-nitro-4(3H)-pyrimidinone (7) and proceeded through cyclization of the resulting phenacylaminopyrimidinone (8) and removal of the 4-methoxybenzyl group. The N-oxide 3 and its 9-arylmethyl derivatives 9 and 11 showed only very weak antileukemic activity and no antimicrobial activity. 相似文献
35.
Cyclic voltammetry of TEMPO in aqueous 0.1 M NaOH in the presence of glutathione (GSH) or cysteine (Cys) indicated the following points: (i) Both of the thiols rapidly formed adducts 3 with oxoammonium ion 1 anodically generated from TEMPO. (ii) 3 generated from GSH entered a succeeding reaction that generated N-oxide anion 2- (the reduced TEMPO). (iii) 3 produced from Cys remained intact over the time scale of voltammetry. A structural feature of GSH was considered to contribute to the observed behavior of this tripeptide. Possible structural features were evaluated by screening various thiols on the basis of whether they provided GSH-like voltammetric results. The 3-mercaptopropionamide group with an amide hydrogen in GSH was determined to be responsible for the observed difference between GSH and Cys. The likely function is to transform 3 from GSH into a 5-imino-1,2-oxathiolane intermediate, thereby releasing 2-. Product analysis for reactions of model thiols representing GSH and Cys with 1 provided support for this argument and suggested that the reaction of GSH or Cys with 1 would produce the corresponding disulfides, regardless of whether a five-membered ring intermediate was formed. The proposed function of the 3-mercaptopropionamide moiety of GSH may provide useful insight for the molecular design of exogenous thiol compounds as novel drugs for the treatment of GSH-depletion-related disorders. 相似文献
36.
Masaaki Kubota Raul A. Reimer Kuniko Terajima Yuji Yoshimura Akio Nishijima 《Analytica chimica acta》1987
Inductively-coupled plasma/atomic emission spectrometry with a high-resolution vacuum scanning monochromator is described for the determination of sulfur at 180.734 nm. The behavior of the signal-to-background ratio is investigated as functions of RF power, argon gas flow rate and observation height above the load coil. Under the operating conditions selected, the detection limit is 3 μg l?1. The Se I 196.090-nm line is chosen as internal standard, because the S/Se line pair exhibited the least change with carrier gas flow rate and acid concentration of solution. Sulfur in NiMo and CoMo/ Al2O3 catalysts used for coal liquefaction is determined as S(II) and S(VI) species. The total amount of the species agreed well with the sulfur value obtained by the conventinal combustion method. 相似文献
37.
38.
39.
40.