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   8180篇
  免费   697篇
  国内免费   450篇
电工技术   140篇
综合类   797篇
化学工业   1364篇
金属工艺   113篇
机械仪表   145篇
建筑科学   462篇
矿业工程   193篇
能源动力   523篇
轻工业   459篇
水利工程   144篇
石油天然气   561篇
武器工业   24篇
无线电   1250篇
一般工业技术   814篇
冶金工业   292篇
原子能技术   60篇
自动化技术   1986篇
  2024年   28篇
  2023年   100篇
  2022年   153篇
  2021年   284篇
  2020年   341篇
  2019年   195篇
  2018年   225篇
  2017年   279篇
  2016年   327篇
  2015年   288篇
  2014年   445篇
  2013年   571篇
  2012年   482篇
  2011年   550篇
  2010年   466篇
  2009年   520篇
  2008年   449篇
  2007年   547篇
  2006年   525篇
  2005年   455篇
  2004年   345篇
  2003年   361篇
  2002年   274篇
  2001年   215篇
  2000年   165篇
  1999年   149篇
  1998年   119篇
  1997年   79篇
  1996年   78篇
  1995年   64篇
  1994年   54篇
  1993年   36篇
  1992年   27篇
  1991年   19篇
  1990年   16篇
  1989年   20篇
  1988年   18篇
  1987年   7篇
  1986年   11篇
  1985年   9篇
  1984年   8篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1962年   1篇
  1961年   1篇
  1958年   1篇
  1957年   1篇
  1951年   2篇
排序方式: 共有9327条查询结果,搜索用时 803 毫秒
991.
优化卤水精制工艺   总被引:3,自引:1,他引:3  
在戈尔膜分离净化卤水的中试过程中,我们对卤水处理与卤水精制的质量、膜结垢的清洗技术进行了研究。结果表明。优化的卤水处理工艺可以防止膜结垢,使卤水精制质量达到优质标准,而膜的清洗也相对容易、周期相对延长;同时还研制了高效酸难溶垢清洗剂,以化学清洗法清除粘膜的硫酸钡垢。  相似文献   
992.
用根霉ZM-10脂肪酶为催化剂,在有机相中催化合成己酸乙酯。文中研究了温度、底物浓度、酸醇比、溶剂、吸水方法等对己酸乙酯合成转化率的影响。结果表明,以环己烷为溶剂,以摩尔比为1∶1.3的己酸和乙醇为底物,己酸浓度为0.2 mol/L,在40℃条件下振荡反应14h,合成己酸乙酯的的转化率可达到91.5%。  相似文献   
993.
流媒体技术及其应用   总被引:1,自引:0,他引:1  
李文芳 《电力学报》2005,20(2):167-168,171
流媒体是网络环境中的一种新的媒体形式,本文探讨了流媒体技术,并对其主要应用做了介绍。  相似文献   
994.
In this paper we investigate the mass transfer of CO2 injected into a homogenous (sub)-surface porous formation saturated with a liquid. In almost all cases of practical interest CO2 is present on top of the liquid. Therefore, we perform our analysis to a porous medium that is impermeable from sides and that is exposed to CO2 at the top. For this configuration density-driven natural convection enhances the mass transfer rate of CO2 into the initially stagnant liquid. The analysis is done numerically using mass and momentum conservation laws and diffusion of CO2 into the liquid. The effects of aspect ratio and the Rayleigh number, which is dependent on the characteristics of the porous medium and fluid properties, are studied. This configuration leads to an unstable flow process. Numerical computations do not show natural convection effects for homogeneous initial conditions. Therefore a sinusoidal perturbation is added for the initial top boundary condition. It is found that the mass transfer increases and concentration front moves faster with increasing Rayleigh number. The results of this paper have implications in enhanced oil recovery and CO2 sequestration in aquifers.  相似文献   
995.
李小苓  邸燕 《电声技术》2002,(11):43-46
概括阐述了以边下载边播放的形式在网上传输多媒体信息的新技术-流式媒体技术,并着重介绍三大解决方案中目前较具优势的方案-RealSystem系统。  相似文献   
996.
A novel process is introduced for rapid vaporization of subcooled liquid in a capillary structure. The process consists of a low-thermal-conductivity porous wick, heated from a downward-facing grooved heating block that is in intimate contact with the upper surface of the wick structure. For such a specially configured heat transfer device, measurements show that vapor can be generated rather quickly once a sufficient amount of heat was applied. The mechanisms leading to the rapid vaporization of liquid are numerically investigated. It is found that the low thermal conductivity of the capillary structure and the presence of the extremely steep temperature gradients at the fin/porous structure interface due to the rather weak natural convection, reflected by small-scale secondary flow cells below the heated fins, are responsible for the rapid vaporization of subcooled liquid.  相似文献   
997.
The effect of glucose oxidase (GOX) catalyzed reaction with glucose on Pseudomonas fragi was analyzed in nutrient broth and fish extract media. Growth of P. fiugi in nutrient broth was clearly suppressed by 1.0, 2.0 and 4.0 mg/mL glucose when combined with 0.5–2.0 U/mL GOX. The same GOX/glucose combinations inhibited P. frasi growth in fish extract media. Viable cell numbers in fish media showed clear growth inhibition with combinations of l.0–2.0 U/mL GOX and 8.0–16.0 mg/mL glucose. Higher GOX and glucose rapidly produced 2.0–2.5 unit decreases in pH, but produced enough gluconic acid to precipitate fish proteins. Use of 0.5 U/mL GOX in fish extract media resulted in slow, sustained activity with potential for inhibition of microbial growth in foods without excessive acidity.  相似文献   
998.
对比等径棒球介质与传统圆球介质在煤磨中使用情况,等径棒球研磨介质在增产、节能和提高粉体 制备质量等方面具有显著的技术经济效果,其具有广阔的推广应用前景。  相似文献   
999.
根据吸附位势(位能)理论,利用Dubinin吸附势的定义,对于同一种类型的吠附剂(多孔介质),对不同吸附质在不同温度条件下测得的吸附实验数据,将其吸附量和吸附势相关联,拟合得到相应的回归方程。并利用拟合得到的回归方程,针对某个气藏(Case2),在确定的平均气层岩心参数的条件下,建立该气藏在给定气层温度下所有组分的吸附等温线。此项研究工作将为开展多孔介质中吸附作用的各种研究(如吸附平衡相态模拟和油气藏数值模拟研究等)提供重要的基础数据和研究方法。  相似文献   
1000.
Soil–steel bridges are built of flexible corrugated steel panels buried in well-compacted granular soil. Their design is based on the composite interaction between the soil pressures and the displacements of the conduit wall. The structure failure could be initiated by shear or tension failure in the soil cover above the steel conduit. The provisions for design given in different codes, such as the Canadian Highway Bridge Design Code, managed to avoid some of the problems associated with the failure of soil above soil–steel bridges by requiring a minimum depth of soil cover over the crown of the conduit taking into consideration the geometric shape of the conduit. However, the present code requirements for a minimum depth of cover were developed for a maximum span of 7.62 m and using nonstiffened panels of 51 mm depth of corrugation. The effect of having larger spans or using more rigid corrugated panels has not been examined before and is the subject of this paper. The present study uses the finite-element analysis to re-examine the possible soil failures due to centric live loads (i.e., loads acting symmetrically about the mid span of conduit) or eccentric live loads. The study deals with spans up to 15.24 m of circular conduits and 21.3 m of arches with deep corrugations. It has been found that, in addition to the conduit geometry, the actual dimension of the span should be considered to determine the required depth of soil cover.  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