全文获取类型
收费全文 | 1004篇 |
免费 | 53篇 |
专业分类
化学 | 851篇 |
晶体学 | 13篇 |
力学 | 11篇 |
数学 | 36篇 |
物理学 | 146篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 19篇 |
2020年 | 26篇 |
2019年 | 39篇 |
2018年 | 23篇 |
2017年 | 12篇 |
2016年 | 38篇 |
2015年 | 32篇 |
2014年 | 30篇 |
2013年 | 54篇 |
2012年 | 104篇 |
2011年 | 97篇 |
2010年 | 38篇 |
2009年 | 45篇 |
2008年 | 60篇 |
2007年 | 49篇 |
2006年 | 74篇 |
2005年 | 44篇 |
2004年 | 45篇 |
2003年 | 40篇 |
2002年 | 38篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1969年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有1057条查询结果,搜索用时 0 毫秒
11.
Masatoshi Fujii Ritsuo Nakamoto Keisuke Yonezawa 《Linear algebra and its applications》2013,438(4):1580-1586
The grand Furuta inequality has the following satellite (SGF;), given as a mean theoretic expression:where is the -geometric mean and () is a formal extension of . It is shown that (SGF; ) has the Löwner–Heinz property, i.e. (SGF; ) implies (SGF;t) for every . Furthermore, we show that a recent further extension of (GFI) by Furuta himself has also the Löwner–Heinz property. 相似文献
12.
The aberration theory applied to co-axial optical systems is extended to off-axial systems, for which third-order aberration coefficients are considered. The derived aberrations are analyzed using three-dimensional ray bundles, spot diagrams, and image charts, and classified in relation to the system symmetry. This theory is very useful for optical designers, allowing them to clarify the relationship between the structures of off-axial optical systems and the corresponding off-axial aberrations. 相似文献
13.
Keisuke Matsuya 《Journal of Difference Equations and Applications》2013,19(3):457-465
In this paper, a discretization of a semilinear wave equation whose nonlinear term is a power function is investigated. It is shown that, when a condition on the initial value problem, similar to that governing the existence of blow-up solutions for the original continuous equation is met, the newly introduced difference equation has blow-up solutions with characteristics corresponding to those of the blow-up solutions for the original equation. 相似文献
14.
A tandem three-component coupling photoreaction proceeds upon photoirradiation of MeCN/H2O solutions containing propanedinitrile (1, malononitrile), 2,5-dimethylhexa-2,4-diene (2), and polycyanoarenes in the presence of phenanthrene and carbonate, leading to selective alpha-monoalkylation of 1. The reaction proceeds via photo-NOCAS (Nucleophile-Olefin Combination, Aromatic Substitution) type mechanism: nucleophilic attack of the anion of 1 to photogenerated 2(*+) is followed by ipso-substitution on the radical anion of the polycyanoarene. It advances under mild, safe, and environmentally friendly conditions such as proceeding at ambient temperature without metals and halogens, and in the presence of weak base. The reaction also represents a novel and metal-free cross-coupling reaction that leads to ipso-substitution on polycyanoarene via aryl-cyano bond cleavage. In addition, the reaction is a rare example of introducing carbon nucleophile in the photoinduced electron transfer reaction, except that of cyanide ion. 相似文献
15.
[Structure: see text] Beta-isocupreidine (beta-ICD)-catalyzed Baylis-Hillman reaction of chiral N-Boc-alpha-amino aldehydes and 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA) takes place without racemization and exhibits the match-mismatch relationship between the substrate and the catalyst. In the case of acyclic amino aldehydes, L-substrates show excellent syn selectivity and high reactivity in contrast to D-substrates. On the other hand, in the case of cyclic amino aldehydes, D-substrates rather than L-substrates show excellent anti selectivity and high reactivity. 相似文献
16.
Benfatto M Della Longa S Hatada K Hayakawa K Gawelda W Bressler C Chergui M 《The journal of physical chemistry. B》2006,110(29):14035-14039
A full multiple theoretical model (MXAN) is applied to fit picosecond difference X-ray absorption spectra at the ruthenium L(3) edge upon photoexcitation of aqueous [RuII(bpy)3]2+. We show that fitting difference spectra allows an increase in sensitivity, such that slight structural changes can be retrieved, which are not detected in fitting full spectra. The Ru-N bond distances of the excited complex in the (3)MLCT state are in good agreement with recently published values. The implementation of the present approach to L-edge spectra and its high sensitivity opens opportunities for its extension to a large class of experiments where difference X-ray absorption spectra are recorded. 相似文献
17.
Koji Kano Keisuke Takuma Tsuyoshi Ikeda Daisuke Nakajima Yashuhiro Tsutsui Taku Matsuo 《Photochemistry and photobiology》1978,27(6):695-701
Abstract— Zn-tetraphenylporphyrin (ZnTPP), solubilized in non-ionic surfactant micelles, was found to sensitize photoreductions of some sodium anthraquinonesulfonatesz in the presence of ascorbic acid under anaerobic conditions. The reaction rate was increased by the addition of an anionic surfactant, while retardation was observed with a cationic surfactant. The pH-reaction rate profiles showed maxima located in the order corresponding to pKa-values for the semiquinone of each anthraquinone-sulfonate. A reaction scheme involving the formation of ZnTPP+ at the primary step, followed by back-reduction with ascorbic acid, is proposed. The reaction scheme is in good agreement with the results of flash photolysis. The surfactant micelles are suggested to aid the charge-separation between the ionic species just after the redox reaction involving the photoexcited ZnTPP and anthraquinonesulfonates. 相似文献
18.
Arata Yajima Yuuma Kagohara Keisuke Shikai Ryo Katsuta Tomoo Nukada 《Tetrahedron》2012,68(6):1729-1735
The synthesis of two potent osteoclast-forming suppressing agents isolated from the Chinese mushroom Agrocybe chaxingu, demethylincisterol A3 and chaxine A, was accomplished using ergocalciferol as the starting material. Our methodology for the synthesis of demethylincisterol A3 and chaxine A featured the construction of a butenolide moiety by the intramolecular Horner–Wadsworth–Emmons reaction under Masamune–Roush conditions. This is the first reported synthesis of chaxine A. 相似文献
19.
20.