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   419520篇
  免费   47139篇
  国内免费   33576篇
电工技术   36254篇
技术理论   1篇
综合类   45708篇
化学工业   52527篇
金属工艺   28937篇
机械仪表   29266篇
建筑科学   31023篇
矿业工程   17546篇
能源动力   10854篇
轻工业   47101篇
水利工程   13545篇
石油天然气   14910篇
武器工业   5979篇
无线电   44140篇
一般工业技术   34977篇
冶金工业   18357篇
原子能技术   7037篇
自动化技术   62073篇
  2024年   2518篇
  2023年   6793篇
  2022年   15665篇
  2021年   20257篇
  2020年   14414篇
  2019年   10231篇
  2018年   10939篇
  2017年   12967篇
  2016年   11604篇
  2015年   18276篇
  2014年   23207篇
  2013年   27405篇
  2012年   34231篇
  2011年   36073篇
  2010年   34051篇
  2009年   32460篇
  2008年   33801篇
  2007年   32726篇
  2006年   28681篇
  2005年   23634篇
  2004年   17149篇
  2003年   11797篇
  2002年   11479篇
  2001年   10225篇
  2000年   7892篇
  1999年   3536篇
  1998年   1438篇
  1997年   1162篇
  1996年   1046篇
  1995年   843篇
  1994年   626篇
  1993年   532篇
  1992年   444篇
  1991年   337篇
  1990年   315篇
  1989年   244篇
  1988年   186篇
  1987年   145篇
  1986年   85篇
  1985年   88篇
  1984年   73篇
  1983年   69篇
  1982年   60篇
  1981年   82篇
  1980年   119篇
  1979年   81篇
  1977年   12篇
  1976年   16篇
  1959年   74篇
  1951年   80篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Advances in the fabrication of solid-solution single crystal relaxor ferroelectrics have made it possible to produce highly efficient piezoelectric crystals, and have attracted renewed interest in the use of these crystals for a new generation of piezoelectric transducers, actuators and sensors. Of particular interest is their incorporation into micro-electromechanical systems (MEMS). In this paper we report on the laser-induced wet chemical etching of lead zinc niobate-lead titanate (PZN-PT) in hydrochloric acid (HCl). Argon-ion laser radiation at power levels up to 4 W is focused to a spot diameter of about 15μm and results in the chemical etching of grooves at patterning speeds up to 5μm/sec. Crystal ion slicing, an ion-implant-based film separation technique, is used in combination with laser etching to form 5 to 10μm-thick patterned and freestanding films for incorporation into micro-electromechanical devices.  相似文献   
2.
Functional Properties and Food Applications of Rapeseed Protein Concentrate   总被引:1,自引:0,他引:1  
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone.  相似文献   
3.
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology.  相似文献   
4.
In this paper, a localized MEI method (L-MEI) is developed and combined with the domain decomposition method (DDM) for the simulation of scattering by a concave cylinder. In the L-MEI, the whole domain is decomposed into many subdomains. Different from the conventional MEI method, the MEI coefficients of the L-MEI method in each subdomain are only dependent on the localized metrons that are defined in the subdomain. The localization of metrons has the following advantages: (1) speeding up the calculation of MEI coefficients and saving memory, (2) making the MEI method available for concave structures, and (3) obtaining a band sparse matrix directly without any modification  相似文献   
5.
化学镀非晶态Ni—B合金的研究   总被引:1,自引:0,他引:1  
本文通过化学镀方法在铜和钢上沉积非晶态Ni-B合金。着重讨论了还原剂浓度、络合剂浓度对化学镀沉积速率的影响;分析了它的耐蚀原因和其显微硬度随退火温度的变化情况并就其应用和发展略作说明。  相似文献   
6.
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
7.
8.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding.  相似文献   
9.
10.
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