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   3373篇
  免费   181篇
  国内免费   2篇
电工技术   18篇
综合类   2篇
化学工业   561篇
金属工艺   54篇
机械仪表   61篇
建筑科学   119篇
矿业工程   10篇
能源动力   49篇
轻工业   617篇
水利工程   25篇
石油天然气   13篇
无线电   137篇
一般工业技术   539篇
冶金工业   880篇
原子能技术   9篇
自动化技术   462篇
  2024年   3篇
  2023年   19篇
  2022年   23篇
  2021年   69篇
  2020年   55篇
  2019年   51篇
  2018年   92篇
  2017年   123篇
  2016年   114篇
  2015年   98篇
  2014年   113篇
  2013年   243篇
  2012年   218篇
  2011年   192篇
  2010年   158篇
  2009年   130篇
  2008年   166篇
  2007年   148篇
  2006年   88篇
  2005年   79篇
  2004年   81篇
  2003年   66篇
  2002年   71篇
  2001年   44篇
  2000年   36篇
  1999年   48篇
  1998年   300篇
  1997年   181篇
  1996年   128篇
  1995年   86篇
  1994年   56篇
  1993年   60篇
  1992年   25篇
  1991年   24篇
  1990年   21篇
  1989年   11篇
  1988年   14篇
  1987年   15篇
  1986年   10篇
  1985年   12篇
  1984年   4篇
  1983年   7篇
  1982年   11篇
  1981年   6篇
  1980年   3篇
  1979年   4篇
  1978年   4篇
  1977年   11篇
  1976年   26篇
  1975年   3篇
排序方式: 共有3556条查询结果,搜索用时 31 毫秒
91.
A solar heated experimental drying kiln was installed in Madrid (INIA-Forest Industries Department) to study the efficiency of solar drying of sawn lumber in Spain, as compared with normal air drying. The kiln has been designed as a low cost semi-greenhouse type, but was equipped with a semi-automated control of the drying schedules. The performance of the solar kiln has been studied during ten test runs over a period of two years particularly with respect to drying rate, initial and final wood MC, reliability and efficiency. The results have proven that the solar kiln is capable of drying (economically) from an initial moisture content of 70 to 80%, to a final MC of 8 to 10% up to 3.5 times faster than air drying. With respect to checks, splits and internal stresses, the final wood quality is mostly better, not only compared to normal air drying but also to conventional kiln drying.  相似文献   
92.
This paper presents the Cantabrian portable infiltrometer (CP infiltrometer), a specially designed device based on rainfall simulation for the assessment of the infiltration capacity of all types of urban pavements. Several pervious and impervious surfaces were tested with the LCS permeameter, an existing infiltration test based on the use of a column of water, and the CP Infiltrometer, simulating rain intensities with return periods of 10, 50, and 500 years and 5?min duration. The discussion of the results indicates that the CP infiltrometer could be used successfully to identify different levels of infiltration capacity and to assess the correct performance of pervious surfaces on which design, construction, and maintenance decisions are based.  相似文献   
93.
94.
95.
Erythrocytes express the same glucose transporter (GLUT-1) as is present in the blood-brain barrier. With the aim of testing the viability of using this transport system to deliver glucosyl drug derivatives to the brain, the uptake of several dopamine-glucose conjugates and a few structurally related analogues by erythrocytes was studied with HPLC and (1)H MAS NMR spectroscopy. The results showed that slight structural changes determine the uptake of glycoconjugates by red blood cells. However, experiments in the presence of glucose transport inhibitors showed that none of the conjugates that efficiently crossed the cell membrane were transported by GLUT-1.  相似文献   
96.
97.
Nanocomposites based on polyamide 6 have been directly prepared by melt compounding, using modified low cost bentonites by three selected quaternary ammonium cations, in particular quaternized octadecylamine (ODA), dimethyl benzyl hydrogenated tallow quaternary ammonium (B2MTH) and dimethyl hydrogenated ditallow quaternary ammonium (2M2TH). Thermal stability of organic modifiers and organoclays has been studied by TGA and results allow evaluating the degree of modifier incorporation into clay galleries. The influence of the organic modifier on the morphology and properties of the obtained nanocomposites has been studied by X-ray diffraction and TEM analysis. Depending on the degree of bentonite modification, different mechanisms were reported to explain the improved mechanical properties of the resulting nanocomposites.  相似文献   
98.
A methodology is proposed for estimating a combined transportation model that accommodates spatial aggregation. It employs maximum likelihood estimation using a joint probability function that includes destination and mode choice simultaneously. The main contribution of the paper is the incorporation of a spatial aggregation strategy to validate the method when the survey data are insufficient. By aggregating small zones into larger districts, estimation of the trip distribution parameters can be achieved with limited data, while mode choice continues to be estimated using disaggregated data. Our results demonstrate that including trip distribution in the travel decision induces variations in the utility function parameter estimators obtained for the different travel modes when only mode choice is estimated. The methodology thus corrects omission bias.  相似文献   
99.
100.
Almond kernels show large variability for oil content and fatty acid profile. The objective of this research was to evaluate the potential of near infrared (NIR) reflectance spectroscopy (NIRS) for the analysis of these traits in almond flour. Ground kernels of 181 accessions collected in 2009 were used for developing calibration equations for oil content and concentrations of individual fatty acids. Calibration equations were developed using second derivative transformation and modified partial least squares regression. They were validated with samples from 179 accessions collected in 2010. The accuracy of calibration equations was measured through the coefficient of determination (r2) in external validation and the ratio of the SD in the validation set to the standard error of prediction (RPD). Both r2 and RPD were high for oil content (r2 = 0.99; RPD = 9.24) and concentrations of oleic (r2 = 0.97; RPD = 5.37) and linoleic acids (r2 = 0.98; RPD = 7.35), revealing that calibration equations for these traits are highly accurate. Conversely, the accuracy of the calibration equations for palmitic (r2 = 0.54; RPD = 1.41) and stearic acids (r2 = 0.52; RPD = 1.44) was too low for allowing their application in practice. NIRS discrimination of oil content and concentrations of oleic and linoleic acids was mainly based on the spectral region from 2240 to 2380 nm. Practical applications : NIRS is a high‐throughput analytical technique that allows fast measurement of several traits in a single analysis without using chemical reagents. We evaluated the feasibility of analyzing oil content and concentrations of palmitic, stearic, oleic, and linoleic acids in almond flour using fruits collected during 2 years from a world germplasm collection. The fruits collected in 2009 were used for NIRS calibration, whereas the fruits collected in 2010 were used for validation. NIRS equations were highly accurate for measuring oil content and concentrations of oleic and linoleic acids, which are important traits defining the quality of almond flour for specific uses in the food industry. These results have applications both in the research laboratory and the food industry, where NIRS is becoming a widely used technique for quality control.  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