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   2689篇
  免费   203篇
  国内免费   11篇
电工技术   40篇
综合类   18篇
化学工业   539篇
金属工艺   56篇
机械仪表   59篇
建筑科学   154篇
矿业工程   8篇
能源动力   81篇
轻工业   186篇
水利工程   28篇
石油天然气   28篇
无线电   322篇
一般工业技术   548篇
冶金工业   241篇
原子能技术   8篇
自动化技术   587篇
  2023年   42篇
  2022年   68篇
  2021年   109篇
  2020年   80篇
  2019年   88篇
  2018年   98篇
  2017年   86篇
  2016年   107篇
  2015年   96篇
  2014年   115篇
  2013年   207篇
  2012年   136篇
  2011年   231篇
  2010年   144篇
  2009年   159篇
  2008年   160篇
  2007年   164篇
  2006年   123篇
  2005年   89篇
  2004年   53篇
  2003年   53篇
  2002年   43篇
  2001年   40篇
  2000年   36篇
  1999年   25篇
  1998年   31篇
  1997年   27篇
  1996年   22篇
  1995年   23篇
  1994年   26篇
  1993年   9篇
  1992年   18篇
  1991年   7篇
  1990年   12篇
  1989年   13篇
  1988年   9篇
  1987年   11篇
  1986年   6篇
  1985年   13篇
  1984年   8篇
  1983年   11篇
  1982年   13篇
  1981年   7篇
  1979年   9篇
  1977年   8篇
  1976年   5篇
  1975年   8篇
  1974年   13篇
  1973年   5篇
  1969年   5篇
排序方式: 共有2903条查询结果,搜索用时 15 毫秒
91.
International Journal on Software Tools for Technology Transfer - A test harness, in automated test generation, defines the set of valid tests for a system, as well as their correctness properties....  相似文献   
92.
This work aims at determining the constitutive model of four commercial water atomised low alloyed steel powders during cold compaction. Single-action experiments were performed, obtaining cylindrical specimens with different H/D ratios. The distribution of axial and radial stresses was investigated, and the relationships describing both the radial stress transmission coefficient and the flow stress as functions of the relative density were determined. The radial stress transmission coefficient also confirmed the hypothesised value of Poisson’s coefficient. The friction coefficient between the powder column and the die wall was determined, also highlighting the influence of the H/D ratio. Measuring the axial and radial strains due to spring-back, the axial and radial elastic moduli were determined, as functions of the relative density. The results obtained for the four materials were compared, also highlighting both differences and similarities.  相似文献   
93.
94.
Shrimp residues were dried (65 °C), grounded, and posteriorly used as an ingredient to the production of ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’. Both products were packed in modified atmosphere (100% N2) and stored for 180 days (25 °C) for shelf life evaluation. The centesimal composition, physicochemical, microbiological and sensory analyses were carried out in triplicate. The microbiological analysis (residue and shrimp flour) was within the limits of the legislation, confirming the hygienic–sanitary care during processing. The protein content was the most outstanding (40.13% for the spiced shrimp flour and 20.52% for the shrimp flavoured biscuits). The microbiological evaluation for the ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’ was below the legal limit, and both products were accepted by sensory analysis. The shelf life evaluation demonstrated stability for 6 months. Thus, we concluded that the Litopenaeus vannamei shrimp residue is a promising ingredient in the food industry.  相似文献   
95.
96.
Copper indium diselenide (CuInSe2) compound was prepared by direct reaction of high-purity elemental copper, indium and selenium. CuInSe2 thin films were deposited onto well-cleaned glass substrates by a hot wall deposition technique using quartz tubes of different lengths (0.05, 0.07, 0.09, 0.11 and 0.13 m). X-ray diffraction studies revealed that all the deposited films are polycrystalline in nature and exhibit chalcopyrite structure. The crystallites were found to have a preferred orientation along the (1 1 2) direction. Micro-structural parameters of the films such as grain size, dislocation density, tetragonal distortion and strain have been determined. The grain sizes in the films were in the range of 65-250 nm. As the tube length increases up to 0.11 m the grain size in the deposited films increases, but the strain decreases. The film deposited using the 0.13 m long tube has smaller grain size and more strain. CuInSe2 thin films coated using a tube length of 0.11 m were found to be highly crystalline when compared to the films coated using other tube lengths; it has also been found that films possess the same composition (Cu/In=1.015) as that of the bulk. Scanning electron microscope analysis indicates that the films are polycrystalline in nature. Structural parameters of CuInSe2 thin films deposited under higher substrate temperatures were also studied and the results are discussed. The optical absorption coefficient of CuInSe2 thin films has been estimated as 104 cm−1 (around 1050 nm). The direct band gap of CuInSe2 thin films was also determined to be between 1.018 and 0.998 eV.  相似文献   
97.
The volatile compositions of 192 olive oil samples from five different European countries were investigated by PTR-MS sample headspace analysis. The mass spectra of all samples showed many masses with high abundances, indicating the complex VOC composition of olive oil. Three different PLS-DA models were fitted to the data to classify samples into ‘country’, ‘region’ and ‘district’ of origin, respectively. Correct classification rates were assessed by cross-validation. The first fitted model produced an 86% success rate in classifying the samples into their country of origin. The second model, which was fitted to the Italian oils only, also demonstrated satisfactory results, with 74% of samples successfully classified into region of origin. The third model, classifying the Italian samples into district of origin, yielded a success rate of only 52%. This lower success rate might be due to either the small class set, or to genuine similarities between olive oil VOC compositions on this tight scale.  相似文献   
98.
Experiments were carried out at 1175–1350°C to study the phosphate capacity of CaO-CaCl2 slags and the sulphide capacity was calculated according to the correlation between the two capacities. At 1200°C the logarithm of the phosphate capacity increased from 24.5 to 26.5 with increasing CaO mole fraction from 0 to 0.22 in the slags and it decreased with increasing temperature. Sulphide capacity increased both with increasing CaO mole fraction and temperature. A good linear correlation was found between slag carbonate capacity and phosphate capacity as well as sulphide capacity. Optical basicity was used to evaluate the property of the CaO-CaCl2 slag in the present study. The value of optical basicity of CaCl2 is established as 0.63. The correlations of optical basicity with above mentioned three capacities were found to be linear.  相似文献   
99.
The equilibrium moisture contents (MC) of leaves and stems of lemon balm (Melissa officinalis L.) were determined separately at temperatures of 25, 35 and 45 °C over a stepwise increase of relative humidity (RH) ranging from 3 to 90% by an automatic, gravimetric analyzer (DVS system). Equilibrium was achieved within 6 h for most of the target values of relative humidity. The equilibrium moisture content of leaves was significantly higher than that of stems (p < 0.05). Differences in moisture sorption capacity between the leaves and stems can be attributed to chemical composition and structure of the tissues. Five three-parameter moisture sorption models (modifications of Chung–Pfost, GAB, Halsey, Henderson and Oswin) were tested for their effectiveness to fit the experimental sorption data. The modified Oswin equation was found to be the best model to describe the adsorption isotherms of both leaves and stems of lemon balm. The recommended MC values of leaves and stems for microbial safe storage at 25 °C were 0.124 and 0.113 kg water per kg dry solids, respectively. The net isosteric heat of sorption was computed from the predicted sorption data by applying the integrated form of the Clausius–Clapeyron equation.  相似文献   
100.
The application of rubber seed oil (RSO) and epoxidized RSO (ERSO) as a plasticizer in acrylonitrile butadiene rubber (NBR) was studied using RSO and ERSO with different levels of epoxidation. The results indicated that ERSO could be used as a less leachable and low volatility plasticizer for NBR. The use of ERSO in NBR gave better abrasion resistance whereas the tensile strength and tear strength were comparable to those vulcanizates that contained dioctyl phthalate as a plasticizer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 668–673, 2003  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