首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   455篇
  免费   10篇
化学   277篇
力学   13篇
数学   55篇
物理学   120篇
  2023年   4篇
  2022年   9篇
  2021年   7篇
  2020年   10篇
  2019年   8篇
  2017年   4篇
  2016年   11篇
  2015年   8篇
  2014年   18篇
  2013年   25篇
  2012年   14篇
  2011年   29篇
  2010年   22篇
  2009年   7篇
  2008年   24篇
  2007年   20篇
  2006年   15篇
  2005年   15篇
  2004年   16篇
  2003年   20篇
  2002年   17篇
  2001年   7篇
  2000年   10篇
  1999年   4篇
  1998年   3篇
  1997年   5篇
  1996年   11篇
  1995年   3篇
  1993年   5篇
  1992年   6篇
  1991年   3篇
  1990年   4篇
  1989年   5篇
  1988年   5篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   8篇
  1980年   6篇
  1979年   11篇
  1978年   3篇
  1977年   5篇
  1976年   4篇
  1975年   3篇
  1974年   2篇
  1973年   6篇
  1926年   2篇
排序方式: 共有465条查询结果,搜索用时 15 毫秒
101.
102.
103.
The Asia-Oceania Forum for Synchrotron Radiation Research (AOFSRR) was formally established by Australia, China, Japan, South Korea, Singapore, Taiwan, and Thailand in 2006. Its objective is to strengthen the collaboration, as well as the inter-communication, among the synchrotron radiation facilities and to promote synchrotron radiation sciences and accelerator-based research in the Asia-Oceania region. Regular meetings have been organized to uphold its objective. The first scientific meeting of AOFSRR took place at KEK, Japan, in 2006. Member countries have been taking turns to organize meetings: Taiwan (NSRRC, 2007), Australia (Australian Synchrotron, 2008), China (SSRF, 2009), South Korea (POSTEC, 2010), Thailand (SLRI, 2012), and Japan (SPring-8, 2013). In 2014, the National Synchrotron Radiation Research Center (NSRRC) hosted the Eighth Asia-Oceania Forum for Synchrotron Radiation Research (AOFSRR 2014) from September 15th to 18th in Hsinchu, Taiwan. The NSRRC is located in the Hsinchu Science Park, within an hour's drive from Taipei, the largest city in Taiwan. Hsinchu is a city not only composed of historical landmarks but also the heartland of high-tech semiconductor industries in Taiwan.  相似文献   
104.
In this article, we prove the convergence of a discrete duality finite volume scheme for a system of partial differential equations describing miscible displacement in porous media. This system is made of two coupled equations: an anisotropic diffusion equation on the pressure and a convection‐diffusion‐dispersion equation on the concentration. We first establish some a priori estimates satisfied by the sequences of approximate solutions. Then, it yields the compactness of these sequences. Passing to the limit in the numerical scheme, we finally obtain that the limit of the sequence of approximate solutions is a weak solution to the problem under study. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 723–760, 2015  相似文献   
105.
A fluorinated methacrylic homopolymer, poly(2,2,3,3,3-pentafluoropropyl methacrylate) (PPFPMA) was synthesized by a free radical polymerization reaction. The dispersive component of the surface energy () of PPFPMA was determined by contact angle measurements and inverse gas chromatography (IGC). An extensive surface characterization was conducted by means of IGC. Surface characterization demonstrated that PPFPMA has low value, even at 35 °C and is a Lewis amphoteric polymer with predominantly basic character, as confirmed by the Lewis acidity and basicity constants KA and KB, respectively. The values of obtained by IGC are slightly higher than those obtained by the contact angle method. This trend can be attributed to the fact that IGC evaluates, primarily, high energy sites of a surface.  相似文献   
106.
The standardization and quality control of plant extracts is an important topic, in particular, when such extracts are used for medicinal purposes. Consequently, the development of fast and effective analytical methods for metabolomic fingerprinting of plant extracts is of high interest. In this investigation, electrospray mass spectrometry (ESI-MS) and (1)H NMR techniques were employed with further statistical analyses of the acquired data. The results showed that negative ion mode ESI-MS is particularly effective for characterization of plant extracts. Different samples of the same species appear well-clustered and separated from the other species. To verify the effectiveness of the method, two other batches of extracts from a species, in which the principal components were already identified (Cynara scolymus), were analyzed, and the components that were verified by the principal component analysis (PCA) were found to be within the region identified as characteristic of Cynara Scolymus extracts. The data from extracts of the other species were well separated from those pertaining to the species previously characterized. Only the case of a species that was strictly correlated from a botanical point of view, with extracts that were previously analyzed, showed overlapping.  相似文献   
107.
Extensive Monte Carlo data analysis gives clear evidence that collapsed linear polymers in two dimensions fall in the universality class of athermal, dense self-avoiding walks, as conjectured by Duplantier [Phys. Rev. Lett. 71, 4274 (1993)].10.1103/PhysRevLett.71.4274 However, the boundary of the globule has self-affine roughness and does not determine the anticipated nonzero topological boundary contribution to entropic exponents. Scaling corrections are due to subleading contributions to the partition function corresponding to polymer configurations with one end located on the globule-solvent interface.  相似文献   
108.
In developing countries, approximately half of the healthcare equipments are not in full use and the main cause of this is the inadequate management of them. The Clinical Engineering might face this problem in the healthcare environment analyzing the equipment with a health technological process perspective to identify opportunities of improvements. Generally, the inadequate management is a result of lack of systemized and contextualized information about the health technological process. The effort to make an adequate management generates an increasing interest in the use of benchmarker. Currently, the benchmarkers used by the Clinical Engineering are not representative of a health technological process as a whole. Health technological process concept is stated in this article. The multicriteria analysis methodology MCDA (Multicriteria Decision Aid) is used to obtain benchmarkers and to identify opportunities of improvements, thus generating conditions for that the Clinical Engineering consolidates its relevant contribution for the healthcare.  相似文献   
109.
Square wave anodic stripping voltammetry was used in simultaneous determinations of eco-toxic metals (Pb, Cd, Cu and Zn) on bismuth film electrodes. The electrodes were prepared in situ on a glassy-carbon electrode (GCE) from 0.1 M acetate buffer (pH 4.5) containing 200 μg L?1 of bismuth (III), as well ex situ on electrochemically oxidized graphitized polyacrylonitrile carbon fibres from 200 mg L?1 Bi(NO3)3 in 1% HNO3 (aqueous) solution. Preparation of a Bi-modified carbon fibre electrode (CFE) was by cation exchange of Bi+3 ions for H+ of the acidic surface groups of the electro-oxidized carbon fibres, followed by electrochemical reduction to Bi0. For the Bi-GCE the linear range was 20–280 μg L?1 for zinc, 10–100 μg L?1 for lead, 10–80 μg L?1 for copper, and 5–50 μg L?1 for cadmium. For the Bi-CFE it was 20–160 μg L?1 for zinc, 10–100 μg L?1 for lead, 10–100 μg L?1 for copper, and 2–120 μg L?1 for cadmium. For both kinds of bismuth modified carbon electrodes, low limits of detection and satisfactory precision were achieved. The method was successfully applied to certified reference materials of biological (bovine liver) and environmental (mussel tissue) importance.   相似文献   
110.
In the work presented here a novel approach to comprehensive two-dimensional liquid chromatography is evaluated. Ion chromatography is chosen for the first-dimension separation and reversed-phase liquid chromatography is chosen for the second-dimension separation mode. The coupling of these modes is made possible by neutralising the first-dimension effluent, containing KOH, prior to transfer to the second-dimension reversed-phase column. A test mixture of 24 low-molar-mass organic acids is used for optimisation of the system. Three food and beverage samples were analysed in order to evaluate the developed methodology, the resulting two-dimensional separation is near-orthogonal, the set-up is simple and all instrumental components are available commercially. The method proved to be robust and suitable for the analysis of wine, orange juice and yogurt.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号