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   11135篇
  免费   203篇
  国内免费   156篇
电工技术   221篇
技术理论   1篇
综合类   435篇
化学工业   2674篇
金属工艺   345篇
机械仪表   694篇
建筑科学   225篇
矿业工程   364篇
能源动力   1414篇
轻工业   636篇
水利工程   19篇
石油天然气   2399篇
武器工业   41篇
无线电   208篇
一般工业技术   882篇
冶金工业   259篇
原子能技术   140篇
自动化技术   537篇
  2024年   12篇
  2023年   128篇
  2022年   182篇
  2021年   238篇
  2020年   289篇
  2019年   248篇
  2018年   282篇
  2017年   262篇
  2016年   250篇
  2015年   248篇
  2014年   516篇
  2013年   628篇
  2012年   586篇
  2011年   916篇
  2010年   548篇
  2009年   554篇
  2008年   510篇
  2007年   518篇
  2006年   495篇
  2005年   574篇
  2004年   499篇
  2003年   453篇
  2002年   313篇
  2001年   302篇
  2000年   299篇
  1999年   303篇
  1998年   264篇
  1997年   207篇
  1996年   175篇
  1995年   174篇
  1994年   102篇
  1993年   71篇
  1992年   71篇
  1991年   53篇
  1990年   40篇
  1989年   27篇
  1988年   20篇
  1987年   22篇
  1986年   18篇
  1985年   11篇
  1984年   10篇
  1983年   16篇
  1982年   8篇
  1981年   22篇
  1980年   9篇
  1979年   5篇
  1978年   5篇
  1977年   4篇
  1975年   3篇
  1974年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients.  相似文献   
2.
This is the first time an extensive investigation has been carried out regarding the effects of riser exit geometry on pressure drop and solid behaviour inside the Internal Circulating Fluidized Bed (ICFB) riser, using different riser exit geometries at several operating conditions.The Radioactive Particle-Tracking (RPT) technique was used for solid concentration measurements and solid residence time distribution at the exit zone. Experiments were conducted using Geldart B particles, in the gas superficial velocity range of 4 to 10 m/s. Axial solid hold-up, solid residence time distribution in the exit zone, and the reflux ratio factor km, (defined earlier by [E.H. Van der Meer, R.B. Thorpe, J.F. Davidson, Flow patterns in the square cross-section riser of a circulating fluidized bed and the effect of riser exit design, Chem. Eng. Sc. 55 (19) (2000) 4079-4099]), were the main criteria used to investigate the impact of gas-solid separator devices implemented at the ICFB riser exit.Solid residence time distribution results and axial solid hold-up profiles provided clear evidence that the separator device at the riser exit strongly influences the hydrodynamic structure of the ICFB riser. The V-shaped riser exit geometry was found to be the optimum of all the configurations studied.  相似文献   
3.
含H_2S井完井液对井下金属管串具有腐蚀性。采用锌基或铁基螯合物除硫剂及咪唑啉缓蚀剂可有效地防止这种腐蚀的发生。本文对H_2S的腐蚀、除硫剂和缓蚀剂产品及其对产层的损害作了介绍与探讨。  相似文献   
4.
用数学方法建立气测井油气储层识别模式,以解决录井中实时软件在判别依据少的条件下,及时识别油气显示假异常的难题。该判别式经实用,正到率达90%。  相似文献   
5.
本文介绍β放射性气体浓度计的一种新的分度方法——泄漏元件排气法。其特点是一只元件可分度放射性气体浓度计的许多读出数(甚至是几个量程),操作方便。  相似文献   
6.
用于重离子核反应实验测量的纵向电场气体电离室   总被引:1,自引:0,他引:1  
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。  相似文献   
7.
Gas transfer efficiency during absorption is an important factor in various technological processes involving the interaction between liquid and gaseous systems. It is known that gas bubble motion characteristics strongly affect the efficiency of mass transfer during gas absorption. A device for mechanical vibration of an aerated liquid was designed, based on a cylindrical column filled up with tab water and a plate oscillating in the vertical direction. The goal of the present study is to investigate the effect of vibration parameters such as amplitude, frequency and form of the applied signal on the efficiency of the oxygenation process. Bubble residence time in the liquid and bubble depth of submergence related to the oscillating plate surface were chosen as main parameters for measurements. Furthermore, experiments were conducted to study the effect of the design parameters of the vibrating plate on bubble motion characteristics. The resultant data show that bubble residence time and depth of submergence can be controlled by changing the amplitude, the frequency and the form of the vibration field applied.  相似文献   
8.
谭廷栋 《测井技术》1992,16(6):402-407
人类社会即将跨入21世纪,各行各业都在预测未来技术的发展,测井行业也不例外。预测成象测井技术将是跨世纪的测井找油找气高技术。  相似文献   
9.
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms, polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of a gas diffusion electrode for oxygen reduction reaction.  相似文献   
10.
B.S. Kirkland 《Polymer》2008,49(2):507-524
Poly(n-alkyl acrylate)s can have side chains that crystallize independently of the main chain; side-chain length can thus be used as a tunable parameter to control the gas permeability of membranes. The gas permeation response of poly(n-alkyl acrylate) and poly(m-alkyl acrylate) blends as a function of temperature is reported for varying side-chain lengths, n and m, and blend composition in the semi-crystalline and molten states. Macroscopic homogeneity is observed for a small range of n and m where |n − m| ≤ 2-4 methylene units. Thermal analysis indicates that the blend components crystallize independently of one another; however, crystallization is hindered by the presence of the other component. Permeation responses of the blends investigated in some cases exhibited two distinct permeation jumps or increases at the melting temperature of each component. Blends with continuous permeation responses but higher effective activation energies of permeation (i.e., more thermally responsive) were observed for some blends over the temperature of interest for membranes to be used for modified atmosphere packaging.  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