全文获取类型
收费全文 | 1473篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
化学 | 1110篇 |
晶体学 | 20篇 |
力学 | 30篇 |
数学 | 99篇 |
物理学 | 250篇 |
出版年
2023年 | 9篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 26篇 |
2015年 | 29篇 |
2014年 | 26篇 |
2013年 | 63篇 |
2012年 | 74篇 |
2011年 | 81篇 |
2010年 | 42篇 |
2009年 | 55篇 |
2008年 | 91篇 |
2007年 | 85篇 |
2006年 | 89篇 |
2005年 | 83篇 |
2004年 | 69篇 |
2003年 | 66篇 |
2002年 | 48篇 |
2001年 | 23篇 |
2000年 | 32篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1969年 | 6篇 |
排序方式: 共有1509条查询结果,搜索用时 0 毫秒
101.
The C-S stretching vibrations of 28 aliphatic sulfides including one thiol are summarized, and all of the C-S stretching bands are classified into several groups. An extraordinarily low frequency associated with the ethyl group is discussed briefly. 相似文献
102.
Calorimetric measurements at 25°C were made to determine the thermodynamic quantities for the intercalation of pyridine with α- and γ-zirconium phosphates. These phosphates showed exothermic reactions with ΔH0 = ?59.3 and ?21.9 kJ mole?1, respectively. The large difference between the depyridination temperatures for both intercalates is rediscussed with the aid of the ΔG0 data obtained. 相似文献
103.
4,4'-Dihydroxytriphenylmethanes were synthesized using Br?nsted acid or Lewis acid in yields of 24-86% as target compounds for developing antiviral agents. Most of the 4,4'-dihydroxytriphenylmethanes showed significant activity against herpes simplex virus type 1 (anti-HSV-1 activity) in a plaque reduction assay. Higher cytotoxicity was observed generally in halogenated 4,4'-dihydroxytriphenylmethanes (2a-d) than in non-halogenated derivatives. The non-halogenated derivative, 4,4',4"-trihydroxy-3"-methoxytriphenylmethane (3), showed remarkable antiviral activity with an EC(50) value of 1.8 microg/ml. 相似文献
104.
We consider primal-dual algorithms for certain types of infinite-dimensional optimization problems. Our approach is based on the generalization of the technique of finite-dimensional Euclidean Jordan algebras to the case of infinite-dimensional JB-algebras of finite rank. This generalization enables us to develop polynomial-time primal-dual algorithms for ``infinite-dimensional second-order cone programs.' We consider as an example a long-step primal-dual algorithm based on the Nesterov-Todd direction. It is shown that this algorithm can be generalized along with complexity estimates to the infinite-dimensional situation under consideration. An application is given to an important problem of control theory: multi-criteria analytic design of the linear regulator. The calculation of the Nesterov-Todd direction requires in this case solving one matrix differential Riccati equation plus solving a finite-dimensional system of linear algebraic equations on each iteration. The number of equations and unknown variables of this algebraic system is m+1, where m is a number of quadratic performance criteria.
Key words.polynomial-time primal-dual interior-point methods – JB-algebras – infinite-dimensional problems – optimal control problemsThis author was supported in part by DMS98-03191 and DMS01-02698.This author was supported in part by the Grant-in-Aid for Scientific Research (C) 11680463 of the Ministry of Education, Culture, Sports, Science and Technology of Japan.Mathematics Subject Classification (1991):90C51, 90C48, 34H05, 49N05 相似文献
105.
In reactive plasma processing, species produced in the plasma reach the surface of a substrate and cause etching, deposition and surface modification through surface reactions. These reactions are characterized by the densities and energies of species incident on the surfaces. In order to realize nano-scale plasma processing, important species for plasma processing have been identified and characterized, and their behavior, not only in the gas phase, but also on the surface, have been clarified and controlled. One of the most critical parameters for insights into surface reaction kinetics of radicals is sticking and surface loss probability. On the basis of radical densities measured by various methods, the sticking and surface reaction loss probabilities have been compiled, and they enable the quantitative understanding of the kinetics of radicals on the surface in the plasma. In this article, the sticking and surface reaction loss probabilities measured thus far are reviewed focusing on fluorocarbon gas, silane gas and methane gas based plasma processes. The establishment of a smart plasma process and the development of an autonomous production device with control of radicals on the basis of insights into the surface reactions for nano-scale plasma processing are presented. 相似文献
106.
and ESI, in which [M + H]+ were not observed or the spectra were complicated. The liquid ionization mass spectra of triorganotin carboxylates varied with solvents and sample concentrations. For instance, the fragment ions [M + (C4H9)3Sn]+ of dimeric ions were observed with chloroform used as a solvent, while the [M + H]+ were observed as the base peak using ethylene dichloride. Spectra useful for the differentiation of isomers [CgH7O3Sn(C4Hg)3] were obtained by the formation of characteristic adduct ions, such as [M + EA + H]+ and [M + 2EA + H]+, with a reagent like 2-aminoethanol. Collision-induced dissociation (CID) spectra observed by ESI and LPI mass spectrometry were similar and provided less information than adduct ions did. 相似文献
107.
Kinichi Obi Yutaka Matsumi Yasuaki Takeda Shinya Mayama Hajime Watanabe Soji Tsuchiya 《Chemical physics letters》1983,95(6):520-524
The new nozzle assembly using Hg-photosensitized reaction has been developed to obtained a jet-cooled radical beam. This technique was applied to produce a HNO radical beam. Laser-induced flourescence excitation spectra were obtained for the 1A″ — 1A′ system. Time-resolved measurements yielded fluorescence lifetimes of 22–29 μs for single rovibronic levels of HNO. 相似文献
108.
Shimizu K Suzuki H Hayashi E Kodama T Tsuchiya Y Hagiwara H Kitayama Y 《Chemical communications (Cambridge, England)》2002,(10):1068-1069
Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction. 相似文献
109.
110.