全文获取类型
收费全文 | 7739篇 |
免费 | 1009篇 |
国内免费 | 2137篇 |
专业分类
化学 | 9911篇 |
晶体学 | 34篇 |
力学 | 55篇 |
综合类 | 65篇 |
数学 | 7篇 |
物理学 | 813篇 |
出版年
2024年 | 15篇 |
2023年 | 125篇 |
2022年 | 187篇 |
2021年 | 349篇 |
2020年 | 430篇 |
2019年 | 329篇 |
2018年 | 316篇 |
2017年 | 290篇 |
2016年 | 401篇 |
2015年 | 395篇 |
2014年 | 492篇 |
2013年 | 820篇 |
2012年 | 544篇 |
2011年 | 495篇 |
2010年 | 444篇 |
2009年 | 444篇 |
2008年 | 538篇 |
2007年 | 548篇 |
2006年 | 470篇 |
2005年 | 422篇 |
2004年 | 414篇 |
2003年 | 440篇 |
2002年 | 372篇 |
2001年 | 236篇 |
2000年 | 217篇 |
1999年 | 176篇 |
1998年 | 143篇 |
1997年 | 151篇 |
1996年 | 141篇 |
1995年 | 126篇 |
1994年 | 92篇 |
1993年 | 75篇 |
1992年 | 71篇 |
1991年 | 42篇 |
1990年 | 41篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
121.
N. A. Ustynyuk M. G. Peterleitner O. V. Gusev L. I. Denisovich 《Russian Chemical Bulletin》1993,42(10):1727-1730
The electrochemical behavior of rhodium sandwich complexes containing η4-pentamethylcyclopentadiene or tetramethylfulvene fragments has been studied by cyclic voltammetry. The complexes undergo
one-electron oxidation to give unstable 17-electron radical cations which are converted into rhodocenium salts as a result
of elimination or uptake of hydrogen or C-C bond cleavage.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1802–1805, October, 1993. 相似文献
122.
The main product of the reaction of 1-methylcyclobutanol with Pb(OAc)4 in benzene is 1-phenyl-4-pentanone; the use of Mn(OAc)3 in acetic acid gives a mixture of 2,9-decanedione and methyl propyl ketone; 1-(chloro-, bromo-, thiocyano-, or cyano)-4-pentanone is formed in the presence of the systems Pb(OAc)4-metal halide or Mn(OAc)3-metal halide.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2760–2763, December, 1992. 相似文献
123.
The [4+2] cyclodimerization of cyclohexa-2,4-dienone derivatives of the orthoquinone monoketal and orthoquinol types has been the topic of numerous investigations over the last 50 years in the aim of rationalizing the extraordinary level of regio-, site-, and stereoselectivities observed in these processes. In particular, the double diastereo-π-facial differentiation expressed in cyclodimerizations of chiral orthoquinols (i.e., 6-alkyl-6-hydroxycyclohexa-2,4-dienones) is an important aspect of these transformations, for they relate to the construction of several natural products. The experimental and theoretical results that are described in this article offer a comprehensive understanding of the factors controlling these site-specific regio- and diastereoselectivities. Our interpretation of these results relies on a combination of Woodward-Hoffmann and Salem-Houk secondary orbital interactions and Cieplak-type hyperconjugative effects in bispericyclic C2-symmetric transition states. 相似文献
124.
125.
A new capillary electrophoretic (CE) technique was developed for the separation of lignin degradation products after permanganate oxidation, yielding information about quality and quantity of various linkages in the lignin molecule. This CE method is a promising alternative to existing gas chromatographic (GC) methods. An advantage in comparison with GC is the short separation time and the fact that the oxidation products (aromatic acids) can be analyzed without derivatization. The selectivity and sensitivity of CE combined with UV detection is adequate and makes it suited for fast routine characterization of lignins. If necessary, the CE method can be coupled with electrospray ionization mass spectrometry in order to make a clear assignment of the peaks. 相似文献
126.
127.
烯丙位氧化的几种方法 总被引:4,自引:0,他引:4
综述了近年来烯丙位氧化的研究进展,详细讨论了过渡金属及其络合物、硒化 合物在烯丙位氧化中的应用,并简述了丁基锂方法、固相催化方法、生物氧化方法 和次氯酸钠氧化方法在烯丙位氧化中的应用. 相似文献
128.
漆树漆酶的催化氧化作用——Ⅳ.二茂铁及其衍生物的酶促氧化 总被引:2,自引:0,他引:2
In phosphate buffer-diethylene glycol monobutyl ether(DGBE), the oxidations of ferrocene and 15 derivatives were investigated in the presence of Rhus vernicifera laccase. The results showed that ferrocene and 11 derivatives can be oxidized. The mechanism of Laccase catalyzed oxidation of ferrocene was put forward. 相似文献
129.
We have studied the electrocatalytic activity of RuO2-PVC film electrodes, fabricated using RuO2 powders prepared at five different temperatures, viz., 300, 400, 500, 600 and 700°C, for the oxidation of glucose in high alkaline media, 1 to 3 M NaOH. The RuO2-PVC film electrodes have been first characterized in 1 to 3 M NaOH solution by cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques in a wide potential range −1,100 to 450 mV (SCE), and three redox pairs representing Ru(IV)/Ru(III), Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI) transitions have been identified. The voltammetric peaks at low sweep rates have been analyzed using surface activity theory formulated for interacting electroactive adsorption sites, and interaction terms have been evaluated. The total voltammetric surface charges have been analyzed as per Trassatti’s formalism with respect to their dependence on potential sweep rate, and charges associated with less accessible and more accessible surface sites have been calculated. For glucose oxidation, the results have indicated that RuO2 (700°C)-PVC electrode shows two oxidation peaks in contrast to RuO2 (300°C)-PVC electrode. Also, RuO2 (700°C)-PVC electrode exhibits higher intrinsic electrocatalytic activity than the 300°C electrode, although the former possesses lower electrochemically active surface area. Additionally, kinetic analyses made from RDE results with reference to Michealis–Menten (MM) enzyme catalysis has shown that RuO2 (700°C) electrode possesses extended glucose-sensing range in terms of MM kinetic constant, K
M
, compared to other electrodes. Possible reasons for such differences in the behavior of the electrodes of different temperatures towards glucose oxidation are identified from studies on oxidation of glucose in solutions of different pH, oxidation of different glucose derivatives, and also from physicochemical results from BET, XRD, SEM, DTGA, XPS analysis of RuO2 powder samples. 相似文献
130.
MA Jianhua LIN Weizhen DU Fuqiang HAN Zhenhui YAO Side & LIN Nianyun .College of Biology Engineering Jimei University Xiamen China .Laboratory of Nanobiomedicine & Laboratory of Radiation Chemistry Shanghai Institute of Applied Physics Chinese Acade Sciences Shanghai China 《中国科学B辑(英文版)》2005,48(4):292-296
Quinones including menadione are ubiquitous in nature. They play important roles in aerobic respira- tion and photosynthesis[1,2]. In addition, exogenous quinones are used as antibiotics and anticancer drugs. Their function is closely related to their red… 相似文献