全文获取类型
收费全文 | 1622篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
化学 | 1233篇 |
晶体学 | 21篇 |
力学 | 4篇 |
数学 | 76篇 |
物理学 | 321篇 |
出版年
2023年 | 12篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 23篇 |
2018年 | 10篇 |
2016年 | 24篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 88篇 |
2012年 | 52篇 |
2011年 | 67篇 |
2010年 | 42篇 |
2009年 | 48篇 |
2008年 | 85篇 |
2007年 | 64篇 |
2006年 | 65篇 |
2005年 | 70篇 |
2004年 | 62篇 |
2003年 | 76篇 |
2002年 | 56篇 |
2001年 | 44篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 17篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 35篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 35篇 |
1979年 | 29篇 |
1978年 | 30篇 |
1977年 | 33篇 |
1976年 | 12篇 |
1975年 | 19篇 |
1974年 | 16篇 |
1973年 | 14篇 |
排序方式: 共有1655条查询结果,搜索用时 31 毫秒
121.
Masahito Sekiguchi Hiromichi Tanaka Noriaki Takami Akiya Ogawa Ilhyong Ryu Noboru Sonoda 《Heteroatom Chemistry》1991,2(3):427-430
The reduction of elemental selenium by samarium diiodide led to selective formation of selenolate anion species (Se2− and Se22−), the alkylation of which provided dialkyl selenides and diselenides, respectively, in excellent yields. 相似文献
122.
123.
124.
Noboru Oyama Takeo Ohsaka Takeyoshi Okajima Tomoaki Hirokawa Tsuyoshi Maruyama Yukio Ohnuki 《Journal of Electroanalytical Chemistry》1985,187(1):79-96
Liquid crystalline/polymer composite membrane-coated electrodes were prepared by casting a 1,2-dichloroethane solution of N-(4-ethoxybenzylidene)-4′-n-butylaniline (EBBA) and polycarbonate (PC) on an electrode surface. The temperature-dependence of the permeability of the EBBA/PC composite membrane on electrodes to Fe(CN)3?6 ion as a solution-phase redox ion was investigated by means of hydrodynamic voltammetry at a rotating disk electrode. The permeability changed with temperature over the range of the crystalline-nematic-phase transition temperature of EBBA. It is demonstrated that the observed temperature-dependence of the permeability reflects the thermotropic properties of EBBA in the EBBA/PC composite membrane. Furthermore, the dependence of the limiting current of the steady-state current-potential curves for the reduction of Fe(CN)—6 at the EBBA/PC composite membrane-coated electrode upon the membrane thickness, the blend ratio of EBBA and PC and the concentration of Fe(CN)3?6 in a bulk solution was examined in order to understand the transport process of Fe(CN)?36 through the EBBA/PC composite membrane from the membrane/solution interface to the electrode/membrane interface. The transport process of Fe(CN)3?6 within the membrane was found to obey Fick's Law. 相似文献
125.
Dr. Atsuko Masuya-Suzuki Satoshi Goto Takafumi Kambe Dr. Ryunosuke Karashimada Dr. Yasuhiro Kubota Prof. Nobuhiko Iki 《ChemistryOpen》2021,10(1):46-55
We prepared Ln(III) (Ln=Eu, Gd, and Yb) complexes with a tripodal Schiff base, tris[2-(5-methylsalicylideneimino)ethyl]amine (H3L) and studied their photophysical properties. Upon ligand excitation, YbL showed Yb(III)-centered luminescence in the near-infrared region. While the overall quantum yield (0.60(1)%) of YbL in acetonitrile was moderate among the reported values for Yb(III) complexes, its radiative lifetime (0.33(2) ms) was significantly shorter than those reported previously. We propose that the ligand-to-metal charge-transfer (LMCT) state mediated the sensitization in YbL. The emission and excitation spectra of EuL indicated the participation of the LMCT state in the sensitization. The radiative lifetime (0.84(7) ms) for EuL in the solid state was rather short compared to those of reported Eu(III) complexes. Our results show that the Yb(III) complex with the Schiff base ligand has two features: the short radiative lifetime and the non-triplet sensitization path. 相似文献
126.
We derive string-loop corrections (torus topology) to the quartic curvature term in the low-energy effective lagrangian for the heterotic string theory. The one-loop correction is found to give the relative weight of two tensor structures different from the tree level. 相似文献
127.
128.
The fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes having mono-, di-, tri-, and tetra(ethyleneglycol) units were examined. The mono(ethylenglycol) derivative was solid at room temperature, whereas the di-, tri-, and tetra(ethylenglycol) derivatives were oily. The monoethyleneglycol derivative showed weak aggregation-induced emission enhancement with fluorescence maximum at 649 nm, which comes from J-aggregates. The fluorescence of oily di-, tri-, and tetra(ethyleneglycol) derivatives in neat form was very weak. No aggregation-induced emission enhancement was observed for the oily derivatives. 相似文献
129.
130.
The pendant E-ring moiety of the podophyllotoxin aza-analogue 1 that is a potent inhibitor of microtubule assembly was modified in order to acquire inhibitory activity of DNA topoisomerase II. The monophenolic analogue 2 did not exhibit human topoisomerase II inhibition, while the ortho-quinone 3 that was obtained by oxidation of 2 inhibited its catalytic activity (decatenation) in a dose-dependent manner and stimulated double strand DNA breaks in supercoiled circular plasmid DNA, resulting in the production of linear DNA. These results showed that the topoisomerase II inhibition of the ortho-quinone 3 is due to stabilization of the topoisomerase II-DNA covalent binary complex. On the other hand, the ortho-quinone 3 did not inhibit the relaxation process of supercoiled DNA by topoisomerase I at concentrations up to 400 microM, nor was intercalation observed in unwinding measurements of 3. Therefore, the ortho-quinone 3 was shown to be a novel nonintercalative topoisomerase II specific inhibitor that stabilizes the cleavable complex. The present results suggest that the 4'-free hydroxyl group on the E-ring and the sugar moiety on the C-ring are not a prerequisite for topoisomerase II inhibition by podophyllotoxin derivatives. 相似文献