全文获取类型
收费全文 | 4410篇 |
免费 | 231篇 |
国内免费 | 64篇 |
专业分类
化学 | 3315篇 |
晶体学 | 41篇 |
力学 | 118篇 |
综合类 | 1篇 |
数学 | 338篇 |
物理学 | 892篇 |
出版年
2023年 | 29篇 |
2022年 | 48篇 |
2021年 | 99篇 |
2020年 | 78篇 |
2019年 | 94篇 |
2018年 | 72篇 |
2017年 | 71篇 |
2016年 | 136篇 |
2015年 | 151篇 |
2014年 | 190篇 |
2013年 | 258篇 |
2012年 | 384篇 |
2011年 | 395篇 |
2010年 | 253篇 |
2009年 | 230篇 |
2008年 | 318篇 |
2007年 | 293篇 |
2006年 | 255篇 |
2005年 | 242篇 |
2004年 | 198篇 |
2003年 | 163篇 |
2002年 | 144篇 |
2001年 | 91篇 |
2000年 | 63篇 |
1999年 | 51篇 |
1998年 | 31篇 |
1997年 | 30篇 |
1996年 | 21篇 |
1995年 | 30篇 |
1994年 | 19篇 |
1993年 | 31篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有4705条查询结果,搜索用时 687 毫秒
21.
Yong‐Jin Kim Jin‐Woong Kim Jung‐Eun Lee Jee‐Hyun Ryu Junoh Kim Ih‐Seop Chang Kyung‐Do Suh 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5627-5635
Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004 相似文献
22.
23.
24.
In single-objective optimization it is possible to find a global optimum, while in the multi-objective case no optimal solution is clearly defined, but several that simultaneously optimize all the objectives. However, the majority of this kind of problems cannot be solved exactly as they have very large and highly complex search spaces. Recently, meta-heuristic approaches have become important tools for solving multi-objective problems encountered in industry as well as in the theoretical field. Most of these meta-heuristics use a population of solutions, and hence the runtime increases when the population size grows. An interesting way to overcome this problem is to apply parallel processing. This paper analyzes the performance of several parallel paradigms in the context of population-based multi-objective meta-heuristics. In particular, we evaluate four alternative parallelizations of the Pareto simulated annealing algorithm, in terms of quality of the solutions, and speedup. 相似文献
25.
M. Alves Da Silva M. Helena Gil A. P. Piedade J. S. Redinha A. M. Oliveira Brett J. M. Caridade Costa 《Journal of polymer science. Part A, Polymer chemistry》1991,29(2):269-274
The immobilization of catalase on grafted membranes of poly(ethylene)-g-co-acrylic acid and poly(tetrafluoroethylene)-g-co-acrylic acid and their application in hydrogen peroxide electrochemical sensors is described. The introduction of carboxylic acid groups onto a hydrophobic support provides a good environment for subsequent enzyme immobilization. This single membrane, hydrogen peroxide sensor showed significant improvement with respect to the double membrane versions. The response is very rapid, the linear range being from 10 μM up to 6 mM, with a detection limit of 4.7 μM, and a lifetime of more than 4 months. 相似文献
26.
M.I.Gil' 《Annals of Differential Equations》2004,20(2):145-154
The nonlocal initial problem for nonlinear nonautonomous evolution equati-ons in a Banach space is considered. It is assumed that the nonlinearities havethe local Lipschitz properties. The existence and uniqueness of mild solutionsare proved. Applications to integro-differential equations are discussed.The main tool in the paper is the normalizing mapping (the generalizednorm). 相似文献
27.
28.
Roberto Ballini Dennis Fiorini Maria Victoria Gil Alessandro Palmieri 《Tetrahedron》2004,60(12):2799-2804
Nitroalkanes have been found to give good yields in Michael and nitroaldol (Henry) reactions by the use of a catalytic amount (10 mol%) of CTAOH, at room temperature and under solvent free conditions and in very short reaction times. The methods do not need a large excess of the nitroalkanes and show good chemoselectivity toward further functionalities. 相似文献
29.
Ha Yong Lee Se Hun Jung Soo Yong Lee Young Ho You Kyung Hyun Ko 《Applied Surface Science》2005,252(5):1891-1898
Al-Al2O3 composite coatings with different Al2O3 particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al2O3) having different sizes and agglomerations were varied into ratios of 10:1 wt% and 1:1 wt%. Al2O3 particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al2O3 particles. In addition, when the large hard particles of fused Al2O3 were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages. 相似文献
30.