全文获取类型
收费全文 | 4665篇 |
免费 | 140篇 |
国内免费 | 30篇 |
专业分类
化学 | 3094篇 |
晶体学 | 35篇 |
力学 | 54篇 |
数学 | 297篇 |
物理学 | 947篇 |
无线电 | 408篇 |
出版年
2022年 | 30篇 |
2021年 | 44篇 |
2020年 | 44篇 |
2019年 | 62篇 |
2018年 | 49篇 |
2017年 | 37篇 |
2016年 | 81篇 |
2015年 | 82篇 |
2014年 | 105篇 |
2013年 | 228篇 |
2012年 | 241篇 |
2011年 | 253篇 |
2010年 | 142篇 |
2009年 | 161篇 |
2008年 | 268篇 |
2007年 | 283篇 |
2006年 | 276篇 |
2005年 | 252篇 |
2004年 | 207篇 |
2003年 | 177篇 |
2002年 | 181篇 |
2001年 | 102篇 |
2000年 | 97篇 |
1999年 | 76篇 |
1998年 | 55篇 |
1997年 | 50篇 |
1996年 | 64篇 |
1995年 | 44篇 |
1994年 | 43篇 |
1993年 | 55篇 |
1992年 | 72篇 |
1991年 | 68篇 |
1990年 | 55篇 |
1989年 | 56篇 |
1988年 | 55篇 |
1987年 | 46篇 |
1986年 | 44篇 |
1985年 | 83篇 |
1984年 | 54篇 |
1983年 | 45篇 |
1982年 | 48篇 |
1981年 | 41篇 |
1980年 | 39篇 |
1979年 | 39篇 |
1978年 | 29篇 |
1977年 | 35篇 |
1976年 | 33篇 |
1975年 | 25篇 |
1974年 | 22篇 |
1973年 | 32篇 |
排序方式: 共有4835条查询结果,搜索用时 0 毫秒
31.
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
32.
33.
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
34.
35.
36.
37.
38.
39.
Minamide T Mitsubayashi K Jaffrezic-Renault N Hibi K Endo H Saito H 《The Analyst》2005,130(11):1490-1494
Methyl mercaptan (MM) is known as one of the major chemicals of halitosis (bad breath). In this study, a bioelectronic gas sensor (bio-detector) for gaseous MM was developed and was applied to measure halitosis in breath. The bio-detector consisted of a Clark-type dissolved oxygen electrode, a monoamine oxidase type-A (MAO-A) immobilized membrane and a reaction unit that had liquid and gaseous compartments separated by a hydrophobic porous polytetrafluoroethylene (PTFE) diaphragm membrane. The tip of the electrode covered with MAO-A membrane was placed into the liquid compartment as touching to the PTFE diaphragm membrane. In order to amplify the bio-detector output, a substrate regeneration cycle caused by coupling the monooxygenase with l-ascorbic acid as reducing reaction with reagent system, was applied. The results of MM vapor measurements showed the calibration range of the bio-detector for MM vapor was from 0.087 to 11.5 ppm (correlation coefficient: 0.993) and included the human sense of smell level 5 (0.2 ppm). The bio-detector had good selectivity being attributed to enzyme specificity was obtained for several substances (trimethyl amine, ammonia, dimethyl sulfide, etc.). The bio-detector was applied for halitosis measurement. Expired gases in five subjects were sampled every hour and the concentrations of MM in the expired gases were monitored. The output of bio-detector showed behaviour of halitosis level changes in a day such as increasing with passage of time and decreasing after eating. 相似文献
40.