全文获取类型
收费全文 | 3464篇 |
免费 | 85篇 |
国内免费 | 10篇 |
专业分类
化学 | 2622篇 |
晶体学 | 78篇 |
力学 | 49篇 |
数学 | 130篇 |
物理学 | 680篇 |
出版年
2022年 | 19篇 |
2021年 | 43篇 |
2020年 | 34篇 |
2019年 | 46篇 |
2018年 | 33篇 |
2017年 | 20篇 |
2016年 | 48篇 |
2015年 | 66篇 |
2014年 | 77篇 |
2013年 | 164篇 |
2012年 | 172篇 |
2011年 | 188篇 |
2010年 | 106篇 |
2009年 | 106篇 |
2008年 | 173篇 |
2007年 | 208篇 |
2006年 | 199篇 |
2005年 | 188篇 |
2004年 | 194篇 |
2003年 | 167篇 |
2002年 | 151篇 |
2001年 | 93篇 |
2000年 | 79篇 |
1999年 | 48篇 |
1998年 | 33篇 |
1997年 | 36篇 |
1996年 | 44篇 |
1995年 | 42篇 |
1994年 | 39篇 |
1993年 | 37篇 |
1992年 | 73篇 |
1991年 | 35篇 |
1990年 | 33篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 33篇 |
1986年 | 34篇 |
1985年 | 45篇 |
1984年 | 48篇 |
1983年 | 26篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 26篇 |
1979年 | 36篇 |
1978年 | 30篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 15篇 |
1974年 | 25篇 |
1973年 | 17篇 |
排序方式: 共有3559条查询结果,搜索用时 625 毫秒
51.
Nagaoka Y Inoue H el-Koussi N Tomioka K 《Chemical communications (Cambridge, England)》2002,(2):122-123
Upon treatment with lithium diisopropylamide achiral and chiral alpha,beta,psi,omega-unsaturated bisphosphine oxides underwent lithiation-conjugate addition tandem cyclization to afford the corresponding endo-alpha,beta-unsaturated cyclic bisphosphine oxides; sequential stereoselective reduction of the cyclized bisphosphine oxide gave the corresponding trans- and cis-bisphosphines that were successfully applicable in a catalytic asymmetric hydrogenation as chiral bisphosphine ligands. 相似文献
52.
Ojida A Mito-Oka Y Inoue MA Hamachi I 《Journal of the American Chemical Society》2002,124(22):6256-6258
The first fluorescent chemosensors toward a native phosphorylated peptide are successfully synthesized. Dinuclear zinc(II)-dipicolylamine-based anthracene (1, 2) can selectively recognize and sense phosphorylated species with an increase in the fluorescence intensity. We also demonstrated that these artificial receptors fluorometrically detect a phosphorylated peptide with high affinity (>107 M-1) in aqueous solution. 相似文献
53.
Inoue M 《Physical review letters》1987,58(9):871-873
54.
Takehiko Yamato Masashi Yasumatsu Yoshiyuki Saruwatari Louis Korbla Doamekpor 《Journal of inclusion phenomena and macrocyclic chemistry》1994,19(1-4):315-331
Novel macrocyclic compounds, hexahydroxy[1.0.1.0.1.0]- (2b) and octahydroxy[1.0.1.0.1.0.1.0]metacyclophane (2c) have been prepared in 50–70% yield by base-catalyzed condensation of 5,5-di-tert-butyl-2,2-dihydroxybiphenyl (1) with formaldehyde in refluxing xylene. An attempted alkylation of the flexible macrocycles2b and2c with ethyl bromoacetate in the presence of Cs2CO3 under acetonitrile reflux gave only one pure stereoisomer3 and4, respectively, while other possible isomers were not observed. The structural characterization of these products is also discussed. The two-phase solvent extraction data indicated that hexaethyl ester3 and octaethyl ester4 show strong metal affinity, comparable with that of the corresponding calix[n]arenes, and a high K+ selectivity was observed for octaethyl ester4.1H-NMR titration of hexaethyl ester3 and octaethyl ester4 with KSCN clearly demonstrate that a 11 complex is formed which is stable on the NMR time scale.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes. 相似文献
55.
Highly reactive zinc was readily prepared by electrolysis of a DMF solution containing pyrene as a mediator with a platinum cathode and a zinc anode. Preferential reduction of pyrene occurred to generate the corresponding radical anion, which reduced zinc ions generated from anodic dissolution to give zero valent zinc with high reactivity. The reactive zinc was successfully used for an efficient transformation of bromoalkanes into the corresponding organozinc bromides. Organozinc bromides obtained were further used successfully in Pd-catalyzed cross-coupling reaction with various aryl iodides and bromides. 相似文献
56.
Saito H Sivaguru J Jockusch S Inoue Y Adam W Turro NJ 《Chemical communications (Cambridge, England)》2005,(27):3424-3426
Oxazolidinone-functionalized enecarbamates undergo diastereoselective E/Z photoisomerization upon direct and triplet sensitized irradiations with chiral/achiral sensitizers, showing that the enhanced product diastereoselectivity depends on the solvent and temperature. 相似文献
57.
Since the first heavy alkene analogues of germanium and tin were isolated in 1976, followed by West''s disilene in 1981, the chemistry of stable group 14 dimetallenes and dimetallynes has advanced immensely. Recent developments in this field veered the focus from the isolation of novel bonding motifs to mimicking transition metals in their ability to activate small molecules and perform catalysis. The potential of these homonuclear multiply bonded compounds has been demonstrated numerous times in the activation of H2, NH3, CO2 and other small molecules. Hereby, the strong relationship between structure and reactivity warrants close attention towards rational ligand design. This minireview provides an overview on recent developments in regard to bond activation with group 14 dimetallenes and dimetallynes with the perspective of potential catalytic applications of these compounds.This minireview highlights the recent advances in small molecule activation and catalytic applications of homonuclear dimetallenes, dimetallynes and interconnected bismetallylenes of heavier group 14 elements. 相似文献
58.
K. Komura K. Komura Y. Kuwahara Y. Kuwahara T. Abe T. Abe K. Tanaka K. Tanaka Y. Murata Y. Murata M. Inoue M. Inoue 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):511-516
Summary Extremely low activity levels of cosmic ray induced nuclides have been measured in freshly precipitated rainwater by quick
chemical separation coupled with ultra low background gamma-spectrometry. The nuclides detected were 38S (T1/2 = 2.83 h)-38Cl (37.2 m), 39Cl (55.6 m), 24Na (14.96 h), 28Mg (20.9 h), 7Be (53.3 d) and 22Na (2.602 y). The number of atoms in rain water were evaluated to be ranging from 400-1900 l-1 for 39Cl (n = 6, mean: 1200), 30-1500 l-1 for 24Na (n = 16, mean: 520), 80-600 l-1 for 28Mg (n = 13, mean: 260), 1 . 106-4 . 107 l-1 for 7Be (n = 16, mean: 7 . 106) and 2 . 103-1 . 105 l-1 for 22Na (n = 9, mean: 2 . 104). Measurements of activity levels and activity ratios of short-lived cosmic-ray induced short-lived nuclides will open new
method to understand atmospheric processes occurred at the altitude of rain cloud. 相似文献
59.
Kondo T Kaneko Y Taguchi Y Nakamura A Okada T Shiotsuki M Ura Y Wada K Mitsudo TA 《Journal of the American Chemical Society》2002,124(24):6824-6825
Pyranopyrandiones were prepared by a novel ruthenium-catalyzed carbonylative dimerization of cyclopropenones via C-C bond cleavage. For example, treatment of dipropylcyclopropenone with a catalytic amount of Ru3(CO)12 and NEt3 in THF under 15 atm of carbon monoxide at 140 degrees C for 20 h gave a novel functional monomer, 3,4,7,8-tetrapropylpyrano[6,5-e]pyran-2,6-dione, in an isolated yield of 81%. Unsymmetrically substituted pyranopyrandiones were also obtained by ruthenium-catalyzed carbonylative coupling of cyclopropenones with alkynes under similar reaction conditions. 相似文献
60.
The title compound shows dual fluorescence depending on polarity of the solvent used. The fluorescence in the nonpolar solvent, cyclohexane, has a maximuni at 370 nm, while the fluorescence in the polar solvent, methanol, has a maximum at 400nm. The short and long wavelength fluorescences were assigned to the syn and anti conformers, respectively. From these observations one is allowed to conclude that a novel solvent dipole-induced rotational isomerism takes place in the excited singlet state. 相似文献