全文获取类型
收费全文 | 956篇 |
免费 | 30篇 |
国内免费 | 7篇 |
专业分类
化学 | 663篇 |
晶体学 | 19篇 |
力学 | 12篇 |
数学 | 40篇 |
物理学 | 259篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 16篇 |
2019年 | 12篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 27篇 |
2013年 | 61篇 |
2012年 | 61篇 |
2011年 | 61篇 |
2010年 | 39篇 |
2009年 | 48篇 |
2008年 | 48篇 |
2007年 | 62篇 |
2006年 | 46篇 |
2005年 | 37篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 26篇 |
2001年 | 33篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1967年 | 4篇 |
排序方式: 共有993条查询结果,搜索用时 15 毫秒
91.
2,2-Dimethyl- and 2-benzyl-2-methyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaethenes were employed as ligand of mononuclear chlorogold(I) complexes, which catalyzed cycloisomerization of 1,6-enyne affording vinylcyclopentene exclusively in the absence of silver co-catalyst. The reaction mechanisms are discussed based on DFT calculations. In addition to the cycloisomerization, the phosphaalkene-chlorogold(I) complexes catalyzed cyclization of pent-4-ynoic acids providing γ-methylene-γ-lactones under basic conditions. 相似文献
92.
Shuhei Kudo Emiko Otsuka Atsushi Suzuki 《Journal of Polymer Science.Polymer Physics》2010,48(18):1978-1986
We report the swelling behavior of chemically crosslinked polyvinyl alcohol (PVA) gels with different degrees of hydrolysis in water, several organic solvents, and their mixed solvents. The gels were dried after gelation and were put into their respective solvents. The gel volume in pure water decreased with increasing temperatures, and the total changes increased with decreasing degrees of hydrolysis. The swelling ratio depends on the solvent and its concentration. In the cases of mixed solvents of methanol–water, ethanol–water, and acetone–water, the gels shrank continuously with increasing concentrations of solvents and reached the collapsed state in the pure organic solvent. In the case of dimethyl sulfoxide (DMSO), on the other hand, the gels shrunk, swelled, and finally reached the swollen state in pure DMSO. Results of measurements using Fourier Transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) suggested that crosslinks and microcrystallites were formed due to hydrogen bonds during the drying process after gelation. The hydrogen bonds were partly destroyed in a rich solvent, but the residual hydrogen bonds had an essential role in determining the swelling behavior in a poor solvent. The swelling behavior and the possible phase transition of the present system are discussed in terms of the solubility of polymers with different degrees of hydrolysis in given mixed solvents and in terms of the formation and destruction of physical crosslinks in the chemical PVA gels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1978–1986, 2010 相似文献
93.
Kiminori Itoh Tohru Okamoto Shuhei Wakita Hiroshi Niikura Masayuki Murabayashi 《应用有机金属化学》1991,5(4):295-301
Thin films of peroxohetero(carbon)polytungstic acid (CW-HPA) and carbon-free isopolytungstic acid (W-IPA) were prepared, and examined in terms of optical and etching properties. Thermal decomposition was found to give good results in removing excess hydrogen peroxide (H2O2) during the preparation of CW-HPA and W-IPA. It was shown for the first time that thin films of CW-HPA and W-IPA have very high refractive indices (larger than 2.0) when sufficiently dried. Optical waveguide (OWG) characteristics of these films were examined using a slab-type OWG structure and ARROW (Antiresonance Reflection Optical Waveguide)-type structures. An embossing technique was applied to make diffractional grating couplers. 相似文献
94.
Tomomi Kawamura 《Topology》2007,46(1):29-38
Rasmussen introduced a knot invariant based on Khovanov homology theory, and showed that this invariant estimates the four-genus of knots. We compare his result with the sharper slice-Bennequin inequality for knots. Then we obtain a similar estimate of the Rasmussen invariant for this inequality. 相似文献
95.
96.
A diketone precursor of air-stable bis-2-thienyl-2,6-anthracene was prepared and quantitatively converted to the target acene by photoirradiation of the n-π∗ absorption both in solution and as a film, in air. 相似文献
97.
Back Cover: CH Activation Generates Period‐Shortening Molecules That Target Cryptochrome in the Mammalian Circadian Clock (Angew. Chem. Int. Ed. 24/2015) 下载免费PDF全文
Tsuyoshi Oshima Dr. Iori Yamanaka Dr. Anupriya Kumar Dr. Junichiro Yamaguchi Dr. Taeko Nishiwaki‐Ohkawa Kei Muto Rika Kawamura Dr. Tsuyoshi Hirota Prof. Dr. Kazuhiro Yagita Prof. Dr. Stephan Irle Prof. Dr. Steve A. Kay Prof. Dr. Takashi Yoshimura Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2015,54(24):7200-7200
98.
99.
Y. Ootao R. Kawamura Y. Tanigawa T. Nakamura 《Archive of Applied Mechanics (Ingenieur Archiv)》1998,68(10):662-676
Summary A neural network model is applied to optimization problems of material compositions for a functionally graded material plate
with arbitrarily distributed and continuously varied material properties in the thickness direction. Unsteady temperature
distribution is evaluated by taking into account the bounds of the number of the layers. Thermal stress components for an
infinite functionally graded material plate are formulated under traction-free mechanical conditions. As a numerical example,
a plate composed of zirconium oxide and titanium alloy is considered. In the optimization problem of minimizing the thermal
stress distribution, the numerical calculations are carried out making use of the neural network. The optimum material composition
is determined by taking into account the effect of temperature-dependence of material properties. The results obtained by
neural network and ordinary nonlinear programming method are compared.
Received 3 March 1998; accepted for publication 22 May 1998 相似文献
100.
Hideo Nagashima Yuichi KuboMitsunobu Kawamura Takashi NishikataYukihiro Motoyama 《Tetrahedron》2011,67(40):7667-7672
A triruthenium cluster, (μ3, η2, η3, η5-acenaphthylene)Ru3(CO)7 effectively catalyzes primary-alkylation reaction of electron-rich aromatic rings using a combination of hydrosilane and ester as a source of the primary-alkyl group. The reaction involves electrophilic substitution of arenes by carbocationic species stabilized by a neighboring alkoxy or siloxy group generated during the reduction of esters giving alkylated arenes after reductive removal of the alkoxy or siloxy group at the benzylic position. 相似文献