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   1029篇
  免费   50篇
  国内免费   18篇
化学   870篇
晶体学   7篇
力学   15篇
数学   63篇
物理学   142篇
  2024年   1篇
  2023年   13篇
  2022年   53篇
  2021年   39篇
  2020年   58篇
  2019年   64篇
  2018年   82篇
  2017年   63篇
  2016年   72篇
  2015年   53篇
  2014年   68篇
  2013年   117篇
  2012年   86篇
  2011年   81篇
  2010年   55篇
  2009年   44篇
  2008年   31篇
  2007年   16篇
  2006年   15篇
  2005年   15篇
  2004年   7篇
  2003年   9篇
  2002年   8篇
  2001年   2篇
  1999年   1篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1992年   3篇
  1990年   1篇
  1988年   1篇
  1985年   5篇
  1984年   3篇
  1983年   1篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1977年   4篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
排序方式: 共有1097条查询结果,搜索用时 15 毫秒
11.
Zahra  S.  Shafaq  B.  Kanwal  B. 《Physics of Atomic Nuclei》2020,83(5):770-772
Physics of Atomic Nuclei - Based on the behavior of elastic scattering of proton and anti-proton at $$\sqrt{s}=1.96$$ TeV for squared four-momentum transfer $$0.26<{-}t<1.2($$ GeV...  相似文献   
12.
Journal of Thermal Analysis and Calorimetry - The present study reports numerical simulations of water-based Al2O3 nanofluid flowing in a 2D channel with a heated wall-mounted obstacle. The...  相似文献   
13.
International Journal of Theoretical Physics - Distributed quantum computing has been well-known for many years as a system composed of a number of small-capacity quantum circuits. Limitations in...  相似文献   
14.
Molecular Diversity - 2-Amino-3-cyano-4H-chromenes are structural core motifs that received increasing attention in the last years due to their interesting potential pharmacological properties. In...  相似文献   
15.
Hossein Farsi  Zahra Barzgari 《Ionics》2013,19(10):1349-1357
In this work, nanostructured tungsten oxide was electrodeposited by cyclic voltammetric technique onto a stainless steel surface. The structure and surface morphology of the resulting oxide film were characterized by means of X-ray diffraction, scanning probe microscopy, and scanning electron microscopy. The electrochemical intercalation of lithium into the nanostructured tungsten oxide was studied using cyclic voltammetry, galvanostatic charge–discharge curves, and electrochemical impedance spectroscopy in a liquid electrolyte consisting of 1 M LiClO4 in propylene carbonate. The as-deposited tungsten oxide indicated the capacity for electrochemical lithium insertion. The specific capacitance of 108.05 F?g?1 was obtained at the constant discharge density of 0.07 mA?cm?2.  相似文献   
16.
In this paper, an extended version of image edge detector using Green's function approach is proposed for detection of edges in the color vector space field. In the proposed method, the relationship between the Red, Green and Blue components is considered to design a differential operator for detection of edges in color images. By using the proposed operator, partial derivatives of all components of color image can simultaneously affect on the edge detection process. Therefore the proposed method can preserve the vector nature of color images during the edge processing stages. Also, the proposed method is compared both quantitatively and qualitatively with other color edge detectors. Experimental results show that the proposed method can efficiently preserve the edges even when the color images corrupted with different levels of noise.  相似文献   
17.
18.
A poly acrylate-ethylene glycol (PA-EG) thin film is introduced for the first time as a novel polar sorbent for sorptive extraction method coupled directly to solid-state spectrofluorimetry without the necessity of a desorption step. The structure, polarity, fluorescence property and extraction performance of the developed thin film were investigated systematically. Carvedilol was used as the model analyte to evaluate the proposed method. The entire procedure involved one-step extraction of carvedilol from plasma using PA-EG thin film sorptive phase without protein precipitation. Extraction variables were studied in order to establish the best experimental conditions. Optimum extraction conditions were the followings: stirring speed of 1000 rpm, pH of 6.8, extraction temperature of 60 °C, and extraction time of 60 min. Under optimal conditions, extraction of carvedilol was carried out in spiked human plasma; and the linear range of calibration curve was 15–300 ng mL−1 with regression coefficient of 0.998. Limit of detection (LOD) for the method was 4.5 ng mL−1. The intra- and inter-day accuracy and precision of the proposed method were evaluated in plasma sample spiked with three concentration levels of carvedilol; yielding a recovery of 91–112% and relative standard deviation of less than 8%, respectively. The established procedure was successfully applied for quantification of carvedilol in plasma sample of a volunteer patient. The developed PA-EG thin film sorptive phase followed by solid-state spectrofluorimetric method provides a simple, rapid and sensitive approach for the analysis of carvedilol in human plasma.  相似文献   
19.
Journal of Thermal Analysis and Calorimetry - Two-phase flow was simulated within the effervescent atomizer by the volume of fluid interface tracing model. Different gas-to-liquid mass ratios...  相似文献   
20.
A novel solid-phase microextraction technique using a hollow fiber-supported sol–gel combined with multi-walled carbon nanotubes was employed in the determination of phenobarbital in wastewater. In this new technique, a silica-based, organic–inorganic polymer containing functionalized multi-walled carbon nanotubes (MWCNTs) was prepared with sol–gel technology via the reaction of tetraethylorthosilicate (TEOS) with an acidic catalyst (HCl). This sol was injected into a polypropylene hollow fiber segment for in situ gelation. This device operated in direct immersion sampling mode. The experimental setup is simple and affordable, and the device is disposable, so there is no risk of cross-contamination or carry-over. Parameters affecting extraction such as pH of the aqueous solution, ageing and extraction times, aqueous sample volume, agitation speed and carbon nanotube amount were optimized. Linearity was observed over a range of 0.50–5000 ng mL−1, with an estimation coefficient (r2) higher than 0.982. The limit of detection (LOD) was 0.32 ng mL−1 (n = 5), and repeatability (RSD% = 2.9) was from the average of three levels of analyte concentrations (1, 1000 and 4500 ng mL−1) with three replicates for each within a single day. Finally, a pre-concentration factor of 2100 was obtained for phenobarbital.  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