全文获取类型
收费全文 | 665篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
化学 | 566篇 |
晶体学 | 7篇 |
力学 | 4篇 |
数学 | 21篇 |
物理学 | 108篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 23篇 |
2014年 | 19篇 |
2013年 | 38篇 |
2012年 | 43篇 |
2011年 | 55篇 |
2010年 | 24篇 |
2009年 | 20篇 |
2008年 | 48篇 |
2007年 | 35篇 |
2006年 | 46篇 |
2005年 | 37篇 |
2004年 | 31篇 |
2003年 | 22篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1973年 | 2篇 |
排序方式: 共有706条查询结果,搜索用时 15 毫秒
71.
Han L Miyasaka K Terasaki O Che S 《Journal of the American Chemical Society》2011,133(30):11524-11533
Cage-type, two-dimensional (2D) cylindrical hexagonal (C), bicontinuous diamond (D), bicontinuous gyroid (G), and one-dimensional (1D) lamellar (L) structures of silica mesoporous crystals (SMCs) were obtained by using the anionic surfactant N-stearoyl-l-glutamic acid (C(18)GluA) as a template in the presence of the nonionic surfactant C(16)(EO)(10) (Brij-56). The mesostructures were controlled by the organic/inorganic interface curvature change induced by Brij-56. A synthesis-field diagram showed that the mesostructure changed in the sequence cage-type → C → intergrowth of C and D → intergrowth of C and G → D → G → L with increase of the amount of Brij-56. Mixed micelles were formed by the anionic and nonionic surfactants, the packing parameter g of which increased with increasing the addition amount of nonionic surfactant and the reaction temperature. The local g parameter was obtained from electron crystallography reconstruction results by calculating mean curvatures and Gaussian curvatures from the equi-electrostatic potential surface. The intergrowth of C and D and two kinds of intergrowth of C and G are also discussed. 相似文献
72.
73.
Dr. Yoshihiro Sohtome Bongki Shin Natsuko Horitsugi Prof. Dr. Keiichi Noguchi Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2011,6(9):2463-2470
Herein, we present details of our conformationally flexible, 1,3‐diamine‐tethered guanidine/bisthiourea organocatalysts for chemo‐, regio‐, and enantioselective 1,4‐type Friedel–Crafts reactions of phenols. These organocatalysts show a unique stereo‐discrimination governed by the differential activation entropy (ΔΔS≠), rather than by the differential activation enthalpy (ΔΔH≠). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS≠). A plausible guanidine–thiourea cooperative mechanism for the enantioselective Friedel–Crafts reaction is proposed. 相似文献
74.
75.
Masazumi Ishiguro Kensuke Harada Keiichi Tanaka Takehiko Tanaka 《Journal of Molecular Spectroscopy》1996,180(2)
Rotational transitions of fluoroacetylene in the ν1(CH stretch) vibrational state have been observed by the laser–microwave double resonance technique using a color center laser as a radiation source in the 3 μm region. The rotational constant and centrifugal distortion constant in the ν1state were determined to be 9684.310(16) MHz and 2.68(62) kHz, respectively, where the uncertainties given in parentheses correspond to 2.5 standard deviations. 相似文献
76.
The extraction behavior of mono-, poly-, anal bis-(benzothiacrown ether)s is studied for alkali, alkaline-earth, heavy, and transition metal ions in the presence of picrate. These ethers show high selectivity for silver ion. Silver extractions from binary and quaternary mixtures of silver with heavy or transition metal ions were successful, except for mixtures with mercury(II) ion. Silver was extracted from a copper ore with ca. 80% recovery. 相似文献
77.
78.
K. Miyajima G. Oohata Y. Kagotani M. Ashida K. Edamatsu T. Itoh 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):33
We have studied direct creation processes of confined biexcitons in CuCl quantum dots by polarization-dependent resonant two-photon excitation spectroscopy. The two-photon absorption band for the lowest state of the biexciton (total angular momentum J=0) which appears on the lower energy side of confined exciton band was identified from the analysis of the polarization dependence of the photoluminescence excitation spectrum of the biexciton. Furthermore, the two-photon excitation process for the excited state of the biexciton (J=2) was also found with polarization dependence different from the J=0 biexciton state. 相似文献
79.
80.
Quark mixings and theor momentum dependences are discussed in a subquark model in which the weak current is made of the iso-doublet spinor subquarks. The Cabibbo angle is predicted to become larger as momentum transfer between quarks grows up. 相似文献