全文获取类型
收费全文 | 799篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
化学 | 524篇 |
晶体学 | 3篇 |
力学 | 50篇 |
数学 | 130篇 |
物理学 | 117篇 |
出版年
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 31篇 |
2015年 | 20篇 |
2014年 | 31篇 |
2013年 | 55篇 |
2012年 | 49篇 |
2011年 | 51篇 |
2010年 | 28篇 |
2009年 | 24篇 |
2008年 | 42篇 |
2007年 | 51篇 |
2006年 | 45篇 |
2005年 | 37篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 26篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1972年 | 5篇 |
1966年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有824条查询结果,搜索用时 453 毫秒
61.
62.
63.
Aldo Banfi Alberto Sala P. Angelo Soresinetti Giovanni Russo 《Journal of heterocyclic chemistry》1990,27(2):215-219
The preparation of new imidazole derivatives containing a carboxylic moiety such as succinic, adipic or benzoic into the side chain, is reported starting from the suitable imidazole intermediates. 相似文献
64.
Aldo Belleni Morante 《Meccanica》1973,8(1):11-15
Summary We prove existence and uniqueness of the solution of a linearized version of the kinetic equation of vehicular traffic on a highway by using the theory of semigroups of linear bounded operators.We assume that a perturbation is introduced at the entrance of the highway, i. e., at x=0 and that it continues for a given time interval [0,
].We then study the behaviour of such a perturvation at values of x close to zero by using perturbation theory for linear operators.Finally, we prove that the perturbation attenuates and approaches zero as x+, i. e. at a large distance from the entrance of the highway.
Work performed under the auspices of the National Research Council (C.N.R., Gruppo Nazionale per la Fisica Matematica). 相似文献
Sommario Si prova l'esistenza e l'unicità della soluzione dell'equazione linearizzata del traffico automobilistico su un'autostrada con un'entrata in corrispondenza di x=0.Si studia poi il comportamento di una perturbazione, dovuta per esempio all'uscita da una partita di calcio, e si mostra come tale perturbazione si attenui al crescere della distanza dall'ingresso dell'autostrada.
Work performed under the auspices of the National Research Council (C.N.R., Gruppo Nazionale per la Fisica Matematica). 相似文献
65.
Summary An ionized gas whose dynamics is dominated by charge exchange is considered. The following two problems are studied: the time
behaviour of sinusoidal waves in a uniform equilibrium; the propagation in a bounded equilibrium of sinusoidal oscillations
forced to the wall. It is shown, in particular, that the equilibria considered, not necessarily thermal equilibria, are stable
for any form of the distribution function.
Research supported in part by C.N.R., G.N.F.M. 相似文献
Sommario Si considera un gas ionizzato, non necessariamente in equilibrio termico, la cui dinamica sia dominata dal processo di scambio di carica, e si studiano i seguenti due problemi: evoluzione temporale di onde sinusoidali su un equilibrio uniforme; propagazione di oscillazioni sinusoidali forzate alla parete in un equilibrio spazialmente limitato. Si mostra in particolare la stabilitá degli equilibri per qualunque forma della funzione di distribuzione.
Research supported in part by C.N.R., G.N.F.M. 相似文献
66.
The merits and limitations of gas-phase electron diffraction as a technique for determining accurately the structures of small
organic molecules are demonstrated by comparing the molecular structures of five benzene derivatives studied in two different
laboratories. The existence of many possible representations of the structure of a molecule (r
a, r
g, r
α, r
α0, r
e, …), implying differences in the physical meaning of geometrical parameters, is discussed in some detail as it may cause
difficulties in a comparison. Also illustrated are different ways of estimating and expressing uncertainties in the geometrical
parameters from a gas-phase electron diffraction study. 相似文献
67.
Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation
of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction
(SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled
with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting
the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied.
To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical
characteristics, fortified with the 100 ng g−1 of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g−1, depending on the compound. 相似文献
68.
The goal of this paper is to determine Göbner bases of powers of determinantal ideals and to show that the Rees algebras of (products of) determinantal ideals are normal and Cohen–Macaulay if the characteristic of the base field is non-exceptional. Our main combinatorial result is a generalization of Schensted's Theorem on the Knuth–Robinson–Schensted correspondence. 相似文献
69.
The sensitivity of the ATLAS detector to the discovery of a heavy charged Higgs boson is presented. Assuming a heavy SUSY spectrum, the most promising channels above the top quark mass are H± → tb and H± → τ±ντ which provide coverage in the low and high tanβ regions up to ∼ 600 GeV. The achievable precisions on the charged Higgs mass and tanβ determination are also discussed. The H± → W± h0 channel, though restricted to a small MSSM parameter space, shows a viable signal in NMSSM where the parameter space is less constrained. The observation of the channel H− → τ−L ντ + c.c. may constitute a distinctive evidence for models with singlet neutrinos in large extra dimensions. 相似文献
70.
In this article the dynamics of generic Cr (r ≥ 3) perturbations of complex polynomials are considered. The attention is focused on the determination of the existence
of large or invariant components of the complement of the basin of ∞, where the interesting dynamics occur. 相似文献