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   3909篇
  免费   248篇
  国内免费   32篇
电工技术   72篇
综合类   19篇
化学工业   1141篇
金属工艺   86篇
机械仪表   128篇
建筑科学   127篇
矿业工程   4篇
能源动力   262篇
轻工业   522篇
水利工程   55篇
石油天然气   67篇
武器工业   2篇
无线电   374篇
一般工业技术   631篇
冶金工业   148篇
原子能技术   12篇
自动化技术   539篇
  2024年   10篇
  2023年   72篇
  2022年   187篇
  2021年   270篇
  2020年   224篇
  2019年   221篇
  2018年   271篇
  2017年   224篇
  2016年   266篇
  2015年   162篇
  2014年   231篇
  2013年   399篇
  2012年   309篇
  2011年   267篇
  2010年   179篇
  2009年   142篇
  2008年   85篇
  2007年   81篇
  2006年   63篇
  2005年   58篇
  2004年   37篇
  2003年   29篇
  2002年   23篇
  2001年   29篇
  2000年   27篇
  1999年   24篇
  1998年   53篇
  1997年   29篇
  1996年   22篇
  1995年   30篇
  1994年   25篇
  1993年   16篇
  1992年   8篇
  1991年   8篇
  1990年   13篇
  1989年   16篇
  1988年   11篇
  1987年   6篇
  1986年   6篇
  1985年   12篇
  1984年   4篇
  1983年   3篇
  1982年   7篇
  1981年   4篇
  1980年   5篇
  1978年   3篇
  1976年   5篇
  1975年   2篇
  1973年   4篇
  1972年   2篇
排序方式: 共有4189条查询结果,搜索用时 15 毫秒
1.
2.
Neural Computing and Applications - Texture analysis is devised to address the weakness of color-based image segmentation models by considering the statistical and spatial relations among the group...  相似文献   
3.
In this paper, cenosphere particles embedded in AA2014 aluminium matrix are used to fabricate syntactic foam by stir casting method. The particle size is about 100?µm and foam density is about 1990?kg?m?3. Compression tests at strain rate 0.001/s are performed on foam samples to characterise their mechanical properties which are then used in numerical analysis on commercial finite element analysis software ABAQUS/CAE with isotropic elastic-plastic material model. Experimental and numerical results show good conformity in deformation behaviour with elastic and plateau zones showing average deviations less than 5% and 20%, respectively. Foams showed high yield stress and energy absorption capabilities that can be useful in making blast and impact resistant structures.  相似文献   
4.
5.
Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry  相似文献   
6.
逆向反射镜光度测量   总被引:1,自引:1,他引:0  
赵阿民  李真 《光电工程》1994,21(6):38-44
为了正确评价逆向反射镜的加工质量与使用效果,且将二者有机地统一起来,本文提出应根据测试目的来选择合适的光度测量方法,并进一步分析了不同测试目的将导致测量装置的组成、几何条件(距离,孔径角,工作姿态等)、光度条件(光源色温、稳定性与均匀性,接收器线性、灵敏度与光谱修正等)、测量参数(反光强度系数、逆反射系数、逆亮度系数等)等各不相同。  相似文献   
7.
Survival of rotavirus on lettuce, radishes, and carrots was studied to evaluate the potential of rotavirus transmission by vegetables irrigated with wastewater. The vegetables were contaminated with rotavirus SA-11 and stored at 4°C and room temperature in covered and uncovered containers to simulate post harvest conditions. Virus decay rates were greater on radishes and carrots than lettuce. Decay rates of rotavirus on lettuce, radish, and carrot ranged from ?0·057 to ?0·479 (log10 pfu/day). Rotavirus SA-11 survived on lettuce, radish, and carrot for 25 to 30 days at 4°C but at room temperature survival was very different for the various vegetables varying from 5 to 25 days. Greatest survival was always observed on the lettuce. These data suggest that rotaviruses can survive long enough on contaminated vegetables as to be transmitted by this vehicle.  相似文献   
8.
This paper considers interference suppression and multipath mitigation in Global Navigation Satellite Systems (GNSSs). In particular, a self-coherence anti-jamming scheme is introduced which relies on the unique structure of the coarse/acquisition (C/A) code of the satellite signals. Because of the repetition of the C/A-code within each navigation symbol, the satellite signals exhibit strong self-coherence between chip-rate samples separated by integer multiples of the spreading gain. The proposed scheme utilizes this inherent self-coherence property to excise interferers that have different temporal structures from that of the satellite signals. Using a multiantenna navigation receiver, the proposed approach obtains the optimal set of beamforming coefficients by maximizing the cross correlation between the output signal and a reference signal, which is generated from the received data. It is demonstrated that the proposed scheme can provide high gains toward all satellites in the field of view, while suppressing strong interferers. By imposing constraints on the beamformer, the proposed method is also capable of mitigating multipath that enters the receiver from or near the horizon. No knowledge of either the transmitted navigation symbols or the satellite positions is required.  相似文献   
9.
A generalized kinematic viscosity-temperature correlation for undefined liquid heavy petroleum fractions has been developed to represent the data for a wide range of temperature from 100°C to 200°C. The correlation is based on the experimental kinematic viscosity data of true boiling point fractions of four Arabian crude oils. The characterization property required for estimation is 50% boiling point. The proposed correlation fits the experimental data with an overall absolute error of 6.1%. Experimental measurements of kinematic viscosity of heavy true boiling point fractions of Arabian crude oils were also obtained in order to develop the proposed correlation.  相似文献   
10.
This paper contributes to extend the minimax disparity to determine the ordered weighted averaging (OWA) model based on linear programming. It introduces the minimax disparity approach between any distinct pairs of the weights and uses the duality of linear programming to prove the feasibility of the extended OWA operator weights model. The paper finishes with an open problem.  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