全文获取类型
收费全文 | 1304篇 |
免费 | 18篇 |
国内免费 | 4篇 |
专业分类
化学 | 915篇 |
晶体学 | 11篇 |
力学 | 19篇 |
数学 | 98篇 |
物理学 | 283篇 |
出版年
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 23篇 |
2015年 | 27篇 |
2014年 | 22篇 |
2013年 | 49篇 |
2012年 | 64篇 |
2011年 | 65篇 |
2010年 | 46篇 |
2009年 | 29篇 |
2008年 | 97篇 |
2007年 | 83篇 |
2006年 | 87篇 |
2005年 | 89篇 |
2004年 | 84篇 |
2003年 | 48篇 |
2002年 | 58篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 21篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1974年 | 10篇 |
1972年 | 7篇 |
排序方式: 共有1326条查询结果,搜索用时 15 毫秒
41.
Yuzuru Uchida Katsumi Onoue Nobuaki Tada Fumio Nagao Hideaki Kozawa Shigeru Oae 《Heteroatom Chemistry》1990,1(4):295-306
Phosphine oxides bearing two or three 2-pyridyl groups react with organometallic reagents affording 2,2′-bipyridyl, 2-substituted pyridines and pyridine in good yields. Phosphonium salts and phosphine oxides, bearing at least two 2-pyridyl or substituted 2-pyridyl groups also give the corresponding 2,2′-bipyridyls and pyridines upon treatment with acid or neutral solvents such as water and alcohols in substantial yields. The 2,2′-bipyridyls are considered to be formed by ligand coupling within the pentacoordinated phosphorus intermediate formed incipiently during the reaction. 相似文献
42.
With the progress of LSI technology, the electronic device size is scaled down to the sub 0.1μ m region. In such an ultrasmall device, it is indispensable to take quantum mechanical effects into account in device modeling. In this paper, we present a newly developed quantum Monte Carlo device simulation applicable to ultrasmall semiconductor devices. In this model, the quantum effects are represented in terms of quantum mechanically corrected potential in the classical Boltzmann equation. It is demonstrated that the quantum transport effects such as tunneling and energy quantization in ultrasmall semiconductor devices are obtained for the first time by using the standard Monte Carlo techniques. 相似文献
43.
M. Rashdan A. Faessler N. Ohtsuka R. Linden W. Wadia M. Ismail 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(4):417-421
Using a complex energy density functional derived from the Reid soft-core potential, the changes in nuclear shapes of two colliding208Pb are investigated. At each separation distanceR, the total binding energy of the Pb + Pb system is minimized w.r.t. the quadrupole deformation and diffuseness parameters of nuclear densities. It is found that the nuclear shapes are strongly affected by the nuclear and Coulomb interactions. A sudden transition occurs from oblate to prolate shapes around R16.8fm and a smooth one from prolate to oblate shapes aroundR?11.76 fm. 相似文献
44.
Yulu Jiang Dr. Taro Ozaki Mei Harada Tadachika Miyasaka Dr. Hajime Sato Dr. Kazunori Miyamoto Dr. Junichiro Kanazawa Dr. Chengwei Liu Prof. Dr. Jun-ichi Maruyama Dr. Masaatsu Adachi Dr. Atsuo Nakazaki Prof. Dr. Toshio Nishikawa Prof. Dr. Masanobu Uchiyama Dr. Atsushi Minami Prof. Dr. Hideaki Oikawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18152-18158
Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome-editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical-induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue. 相似文献
45.
Satoshi Tanaka Kazuaki Yoshida Seiichiro Kinugasa Yoshihiro Ohtsuka 《Optical Review》1997,4(1):A92-A95
Novel birefringent single-mode fibers are fabricated with a vacant hole on either side of the central elliptical core, referred to as side-hole fiber, and their intrinsic and tension-induced modal birefringences are measured to know their characteristic properties for the purpose of making a strain sensor. Five sampled side-hole fibers are prepared for measurements. The sensitivity of the strain sensor is primarily determined by two parameters, tension-induced and intrinsic modal birefringences. Tension-induced modal birefringence is controllable by optimal arrangement of the size and location of the side-holes in the cross-section of the fiber. A sensitivity diagram for designating and fabricating side-hole fibers is presented. 相似文献
46.
Lea Kremer Elisabeth Hennes Alexandra Brause Andrei Ursu Lucas Robke Hideaki T. Matsubayashi Yuta Nihongaki Jana Flegel Ivana Mejdrov Jan Eickhoff Matthias Baumann Radim Nencka Petra Janning Susanne Kordes Hans R. Schler Jared Sterneckert Takanari Inoue Slava Ziegler Herbert Waldmann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16770-16781
47.
Hideaki Takahashi Hajime Ohno Ryohei Kishi Masayoshi Nakano Nobuyuki Matubayasi 《Chemical physics letters》2008,456(4-6):176-180
In a recent development we proposed a quantum chemical approach to compute free energy change for chemical reactions in condensed phases by combining the QM/MM method with the theory of energy representation (QM/MM-ER). We extend in this Letter the novel approach to compute reduction free energy of isoalloxazine ring of FAD (flavin adenine dinucleotide) immersed in water within the framework of the QM/MM-ER method. The characteristic feature of our approach is that the excess electron to be attached on the FAD is identified as a solute. The reduction free energy has been obtained as −80.1 kcal/mol in the aqueous solution. 相似文献
48.
49.
Hideaki Matsuda 《Journal of polymer science. Part A, Polymer chemistry》1974,12(10):2419-2433
Divalent metal salts (I) of monohydroxyethyl phthalate have catalytic activity for polymerization of isocyanate groups. The synthesis of novel metal-containing isocyanurate-type crosslinked polyurethanes were investigated by the crosslinking reaction of I in DMF with diisocyanates or urethane prepolymers, that is, diisocyanate adducts of polyethylene glycol. 2,4-Toluene diisocyanate and diphenylmethane diisocyanate were used as diisocyanates, and DMF was the solvent. The crosslinking reactions were followed by determining the gelation time. Gelation time decreased with increasing temperature. The Ca salt was more effective than the Mg salt in the crosslinking reaction. The yields of resulting metal-containing three-dimensional polymers decreased with increasing metal content in the feed. The Ca salt was more easily introduced into the network polymers than the Mg salt was. Decomposition temperatures decreased on introducing metals into the network polymers. Some physical properties of the metal-containing network polymers are also discussed. 相似文献
50.
Hideaki Takahashi Shin-ichiro Kurimoto Junichi Kobayashi Takaaki Kubota 《Tetrahedron letters》2018,59(51):4500-4502
A new indole alkaloid with the canthin-6-one skeleton, ishigadine A, has been isolated from an Okinawan marine sponge Hyrtios sp. The structure of ishigadine A was elucidated on the basis of spectroscopic analyses. Ishigadine A is a new canthin-6-one alkaloid possessing a hydroxy group, a 1,3-dimethyl-4-methylthioimidazolium, and a 1-propylguanidine. Ishigadine A is the third canthin-6-one alkaloid from sponges. Ishigadine A might be generated from l-arginine, l-histidine, and l-tryptophan. Ishigadine A exhibited moderate cytotoxicity against L1210 murine leukemia cells. 相似文献