全文获取类型
收费全文 | 2450篇 |
免费 | 41篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 106篇 |
综合类 | 52篇 |
化学工业 | 1228篇 |
金属工艺 | 41篇 |
机械仪表 | 78篇 |
建筑科学 | 34篇 |
矿业工程 | 55篇 |
能源动力 | 369篇 |
轻工业 | 44篇 |
水利工程 | 41篇 |
石油天然气 | 50篇 |
武器工业 | 2篇 |
无线电 | 20篇 |
一般工业技术 | 176篇 |
冶金工业 | 159篇 |
原子能技术 | 13篇 |
自动化技术 | 54篇 |
出版年
2024年 | 1篇 |
2023年 | 23篇 |
2022年 | 27篇 |
2021年 | 26篇 |
2020年 | 39篇 |
2019年 | 35篇 |
2018年 | 36篇 |
2017年 | 40篇 |
2016年 | 37篇 |
2015年 | 34篇 |
2014年 | 97篇 |
2013年 | 173篇 |
2012年 | 71篇 |
2011年 | 150篇 |
2010年 | 142篇 |
2009年 | 123篇 |
2008年 | 156篇 |
2007年 | 143篇 |
2006年 | 123篇 |
2005年 | 144篇 |
2004年 | 124篇 |
2003年 | 120篇 |
2002年 | 117篇 |
2001年 | 72篇 |
2000年 | 57篇 |
1999年 | 81篇 |
1998年 | 53篇 |
1997年 | 47篇 |
1996年 | 33篇 |
1995年 | 51篇 |
1994年 | 25篇 |
1993年 | 15篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 2篇 |
排序方式: 共有2522条查询结果,搜索用时 515 毫秒
1.
The methanol‐to‐olefins reaction (MTO) was studied in a small‐scale fluidized‐bed reactor over synthesized silicoaluminophosphate (SAPO‐34) catalysts. Mesoporous nanocrystalline SAPO‐34 molecular sieves were synthesized hydrothermally by ultrasonic and microwave‐assisted aging processes in the presence of hexadecyltrimethylammonium bromide (CTAB) and tetradecyldimethyl(3‐trimethoxysilylpropyl)ammonium chloride (TPOAC) as surfactant agents. The Box‐Behnken experimental design method was applied to determine the optimum operating parameters of this process conducted in the fluidized‐bed reactor. The optimum conditions in terms of reaction temperature, ratio of inlet gas velocity to minimum fluidizing velocity, and MeOH weight fraction were evaluated. 相似文献
2.
A hybrid fluidized-bed bioreactor for water purification was proposed and analyzed. It is a novel type of bioreactor characterized by hitherto unknown stationary and dynamic features. Steady-state characteristics of this hybrid bioreactor with external liquid circulation are presented. A quantitative analysis of steady-state properties of the bioreactor was performed with the aid of an original mathematical model developed for a double-substrate aerobic microbiological process. A steady-state analysis of aerobic processes characterized by different oxygen demand was performed. The effect of essential parameters was evaluated, including carbonaceous substrate concentration in the feed stream to the apparatus, aeration intensity, total residence time of a liquid in the bioreactor, and height of the bed of fine carrier particles. 相似文献
3.
4.
Jonas Berghel 《Drying Technology》2005,23(5):1027-1041
This article presents experimental results for spouted bed drying of sawdust, carried out in a full-scale as well as in a laboratory-scale dryer using air as well as steam as drying media. The aim is to present design parameters for a spouted-bed sawdust dryer that can be used by the industry in designing full-scale dryers. A hydrodynamically stable spouted jet spouted bed was obtained. The heat transfer characteristics of the bed were represented in terms of a volumetric heat transfer coefficient (VHC). When sawdust is dried in a spouted bed, the mean VHC is increasing up to fiber saturation level (20-25% wb) from 40 to 110 W/m3 K. The VHC decreases with the residence time and with an increased static bed height. Gas temperature profiles are also presented for the bottom part of the drying chamber. 相似文献
5.
锌精矿制粒沸腾焙烧新工艺的应用与改进 总被引:1,自引:0,他引:1
介绍了锌精矿制粒沸腾焙烧新工艺的工业化生产应用与技术改进情况 ,阐述了取得的成果及存在的问题 相似文献
6.
Critical Shear Stress of Bimodal Sediment in Sand-Gravel Rivers 总被引:1,自引:0,他引:1
A new model for the critical shear stress and the transport of graded sediment is presented. The model is based on the size distribution of the bed surface and can be used to compute sediment transport rates in numerical simulations with an active layer model. This model makes a distinction between unimodal and bimodal sediments. It is assumed that all size fractions of unimodal sediments have the same critical shear stress while there is selective transport for the gravel fractions of bimodal sediments. A recently published laboratory transport data set is used to calibrate our model. 相似文献
7.
借鉴英国经验完善中国土地产权流转 总被引:1,自引:0,他引:1
本文在简要介绍中、英两国土地产权制度和土地产权流转的基础上,分析了我国土地产权流转过程中出现的问题,如征地过程中的赔偿过低且不完善、国有土地拆迁补偿不公以及补偿的分配方式不公平等问题。由于英国在土地制度方面与中国的相似性,文章借鉴英国土地补偿中的补偿金与改善金相结合原则、土地使用权的租赁行为以及开发收益回馈社会的方法,为完善和健全我国的土地产权流转机制提出措施和建议。 相似文献
8.
武钢氧气公司在大型空分设备循环冷却水系统中,采用化学法和物理法进行水处理效果的实践探索,从原理和监测数据上进行了对比、分析研究,确认物理法具有高效除垢、防垢、杀菌灭藻、缓蚀以及净化等功能,可以取代化学法进行循环水处理。 相似文献
9.
《Materials and Manufacturing Processes》2007,22(1):5-8
The technological properties of the hot-work tool steels depend on their microstructural quality induced by the production process and the heat treatment. One of the frequently applied methods to improve microstructure is preheat treatment. The treatment of carbonitriding X37CrMoV5-1 steel has been investigated in fluidized bed furnaces. Thickness and phase composition have been conducted using optical microscopy Neophot 32 and scanning microscopy, JEOL 5400, after etching in nital. 相似文献
10.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献