全文获取类型
收费全文 | 5496篇 |
免费 | 189篇 |
国内免费 | 24篇 |
专业分类
化学 | 4137篇 |
晶体学 | 22篇 |
力学 | 111篇 |
综合类 | 2篇 |
数学 | 751篇 |
物理学 | 686篇 |
出版年
2023年 | 37篇 |
2022年 | 99篇 |
2021年 | 219篇 |
2020年 | 131篇 |
2019年 | 158篇 |
2018年 | 142篇 |
2017年 | 112篇 |
2016年 | 196篇 |
2015年 | 189篇 |
2014年 | 171篇 |
2013年 | 354篇 |
2012年 | 374篇 |
2011年 | 390篇 |
2010年 | 274篇 |
2009年 | 213篇 |
2008年 | 316篇 |
2007年 | 353篇 |
2006年 | 311篇 |
2005年 | 250篇 |
2004年 | 224篇 |
2003年 | 186篇 |
2002年 | 158篇 |
2001年 | 70篇 |
2000年 | 75篇 |
1999年 | 51篇 |
1998年 | 63篇 |
1997年 | 41篇 |
1996年 | 46篇 |
1995年 | 32篇 |
1994年 | 38篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1985年 | 17篇 |
1984年 | 25篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 10篇 |
1978年 | 19篇 |
1975年 | 13篇 |
1970年 | 10篇 |
1969年 | 13篇 |
1968年 | 9篇 |
1965年 | 9篇 |
1916年 | 10篇 |
排序方式: 共有5709条查询结果,搜索用时 218 毫秒
1.
Nonlinear Dynamics - In this paper, we analyze the effect which the choice of a friction model has on tippe top inversion in the case where the resulting action of all dissipative forces is... 相似文献
2.
Carello Giuliana Landa Paolo Tnfani Elena Testi Angela 《Central European Journal of Operations Research》2022,30(1):159-187
Central European Journal of Operations Research - In the past years, the number of patients in need of chemotherapy treatments has been constantly increasing. Chemotherapy treatments must be... 相似文献
3.
Elena Kardash-Strochkova Yakov I. Tur’yan I. Kuselman Naphtali Brodsky 《Accreditation and quality assurance》2002,7(6):250-254
The results of two interlaboratory comparisons of acid number determinations in used motor oils are discussed. It is shown
that the comparability of the measurement results is not as good as that required by known standards for petroleum products.
The problem is motor oil contaminants which accumulated during use, and which are the source of a matrix effect in the acid
number determination. The standard methods’ drawbacks are analyzed and some improvements are proposed. Repeatability and accuracy
of the improved methods are evaluated.
Received: 11 December 2001 Accepted: 15 February 2002 相似文献
4.
Bajdik J. Pintye-Hódi K. Novák Cs. Kelemen A. Regdon G. Erős I. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):613-627
The extents of the protective effects of coating films on the surface of crystals were determined. Three different samples
were made with different quantities of coating fluid (Sepifilm LP 010 in 10% aqueous solution). Since the atomizing rate was
constant, the coating time increased in parallel with the volume of coating fluid applied. The direct measurement of film
thickness and smoothness is very difficult, and therefore indirect methods were used. Dimenhydrinate was chosen as model drug;
this is a heat-sensitive antihistamine with a low melting point. This temperature can be reached during the tableting process.
The behaviour of samples on exposure to heat was examined by differential scanning calorimetry. The water uptakes of the samples
were determined with an Enslin apparatus. Plasticity was studied with an instrumented tablet machine. These indirect methods
(thermal conductivity, water uptake and plasticity measurements) revealed connections between the results of the various experiments.
An overlong coating time decreased the protective effect of the coating film.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Mariusz Bednarz Peter Reineker Elena Mena-Osteritz Peter Buerle 《Journal of luminescence》2004,110(4):225-231
We theoretically study the size-dependent relation between absorption spectra of thiophene-based oligomers and the corresponding cyclothiophenes. In our approach based on a Frenkel exciton Hamiltonian, we demonstrate that the geometry and selection rules determine the observed relations between the spectra. 相似文献
6.
7.
In [7] point-reflection geometries were studied which can be derived from commutative kinematic
spaces without involutory elements. But the class of point-reflection geometries is larger. For example, elliptic
planes with their reflections cannot be derived from commutative kinematic spaces. Here we investigate a larger
class of reflection geometries.This paper was sponsored by Vigoni Program 1999. 相似文献
8.
Elena Larraz Carlos Elvira Julio San Romn 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1641-1649
This article explores the synthesis of a novel methacrylic macromonomer with an amphiphilic character derived from poly(ethylene glycol) tert‐octylphenyl ether (MT) and its respective homopolymer. To know their reactivity in radical copolymerization reactions with methyl methacrylate (MMA), a model monomer (MTm) was synthesized to determine the reactivity ratios and compare them with the low molar fractions of copolymers of MT with MMA because they were difficult to isolate. They were rMTm = 0.97 and rMMA = 0.95. The compositional diagrams when representing the weight fraction of MT and MTm in the feed and the copolymer suggested that a clear correlation exists between the experimental points of the model monomer MTm and the macromonomer MT ones, suggesting that the length of the side poly(ethylene oxide) chain does not affect the reactivity of the methacrylic double bond in the prepared monomers for this type of polymerization reaction. The reactivity ratios of the copolymers have a tendency for the formation of random or Bernoullian copolymers. The glass‐transition temperatures (Tg's) of the prepared copolymers were determined by differential scanning calorimetry, deviated from the Fox equation, and discussed on the basis of treatments that consider the influence of the monomeric units along the copolymer chains, determining the Tg of the corresponding alternating dyads. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1641–1649, 2003 相似文献
9.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria. 相似文献
10.