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   53186篇
  免费   5818篇
  国内免费   2212篇
电工技术   6412篇
技术理论   3篇
综合类   4229篇
化学工业   4865篇
金属工艺   1507篇
机械仪表   1402篇
建筑科学   8702篇
矿业工程   1299篇
能源动力   6196篇
轻工业   7190篇
水利工程   3072篇
石油天然气   2161篇
武器工业   258篇
无线电   3145篇
一般工业技术   4573篇
冶金工业   1468篇
原子能技术   269篇
自动化技术   4465篇
  2024年   371篇
  2023年   1231篇
  2022年   1982篇
  2021年   2285篇
  2020年   2361篇
  2019年   2134篇
  2018年   1853篇
  2017年   2051篇
  2016年   2051篇
  2015年   2139篇
  2014年   3465篇
  2013年   3115篇
  2012年   3800篇
  2011年   4065篇
  2010年   2904篇
  2009年   2946篇
  2008年   2714篇
  2007年   3216篇
  2006年   2911篇
  2005年   2338篇
  2004年   2004篇
  2003年   1637篇
  2002年   1372篇
  2001年   1155篇
  2000年   955篇
  1999年   773篇
  1998年   632篇
  1997年   508篇
  1996年   437篇
  1995年   328篇
  1994年   312篇
  1993年   210篇
  1992年   196篇
  1991年   113篇
  1990年   83篇
  1989年   95篇
  1988年   74篇
  1987年   60篇
  1986年   49篇
  1985年   70篇
  1984年   44篇
  1983年   31篇
  1982年   27篇
  1981年   19篇
  1980年   32篇
  1979年   12篇
  1977年   8篇
  1976年   8篇
  1975年   8篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
苏虓 《石化技术》2003,10(2):5-8
介绍湛江东兴炼油厂的重整装置由200kt/a扩能至300kt/a中有关催化重整反应动力学模拟计算软件的应用、反应工艺技术的改造、装置标定的情况。结合装置实际情况,采用两段装填、两段混氢技术提升了装置的技术水平。标定结果表明,改造后的装置达到了预期目的。  相似文献   
113.
简要介绍了鞍钢现有人造富矿生产能力,分析了鞍钢生产1600万t/a生铁所需要的炉料数量、品种和质量,并提出了解决炉料缺口的方法和措施。  相似文献   
114.
根据高炉风机配置的具体情况 ,为充分发挥大风机生产优势 ,建立了适宜的送风制度及装料制度 ,对利旧风机采取了自动防喘振控制、高压水阻软启动的措施 ,风机仪表采用集散控制 ,并优化上料系统 ,提高了高炉上料能力。一系列优化方案保证了高炉稳定、安全、顺行 ,1号、2号高炉利用系数分别由 3 .3 64、3 .43 2t/m3.d提高到 3 .917和 3 .767t/m3.d。  相似文献   
115.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
116.
一种三叉树的存储结构及其基本操作的实现   总被引:3,自引:0,他引:3  
本文在文献[1]所给出的有关三叉树有其相关概念的基础上,提出了一种新的三叉树存储结构,即“儿子-兄弟链表”方法,并在这种结构下,对三叉树的基本操作的实现算法进行了较详细的讨论。  相似文献   
117.
This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77.  相似文献   
118.
A cryo-specimen storage system for low-temperature scanning electron microscopy (LTSEM) specimens is described, which: liberates multi-specimen experiments from sampling restrictions imposed by the rate at which LTSEM specimens can be examined in the SEM; provides security against experiment loss resulting from breakdown of the SEM or cryo-system; enables collection of specimens in the field or in laboratories remote from the SEM laboratory; and facilitates international air transport of LTSEM specimens. The components of the system, which has a capacity of 98 stub-mounted specimens, are readily made in a laboratory workshop. The details of the design may be altered to suit particular specimen types or experimental approaches.  相似文献   
119.
杨学民  郭占成 《炼钢》1994,10(5):45-50
本文总结了近年冶金炉渣氮酸盐容量的研究方法,氮在炉渣中存在形态与炉渣氧分压的关系,炉渣氮化物容量与温度及炉渣成分的关系,并给出设计钢液脱氮渣系的基本原则。  相似文献   
120.
Single=walled carbon nanotubes(SWNTs) were synthesized by a hydrogen arc discharge method.A high yield of gram quantity of SWNTs per hour was achieved.Tow kinds of SWNT products:web-like substancea and thin films in large slices were obtained. Results of resonant Raman scattering measurements indicate that the SWNTs prepared have a wider diameter distribution and a larger mean diameter.Hydrogen uptake measurements of the two kinds of SWNT samples(both as prepared and pretreated) were carried out using a high pressure volumetric method,respectively.And a hydrogen storage capacity of 4 wt pct could be repeatedly achieved for the suitably pretreated SWMNTs,whicb indicates that SWNTs may be a promising hydrogen storge material.  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