全文获取类型
收费全文 | 8261篇 |
免费 | 398篇 |
国内免费 | 209篇 |
专业分类
电工技术 | 308篇 |
综合类 | 273篇 |
化学工业 | 1268篇 |
金属工艺 | 584篇 |
机械仪表 | 370篇 |
建筑科学 | 385篇 |
矿业工程 | 337篇 |
能源动力 | 651篇 |
轻工业 | 370篇 |
水利工程 | 66篇 |
石油天然气 | 702篇 |
武器工业 | 45篇 |
无线电 | 1265篇 |
一般工业技术 | 897篇 |
冶金工业 | 300篇 |
原子能技术 | 297篇 |
自动化技术 | 750篇 |
出版年
2024年 | 16篇 |
2023年 | 97篇 |
2022年 | 143篇 |
2021年 | 220篇 |
2020年 | 197篇 |
2019年 | 179篇 |
2018年 | 184篇 |
2017年 | 258篇 |
2016年 | 257篇 |
2015年 | 273篇 |
2014年 | 445篇 |
2013年 | 505篇 |
2012年 | 493篇 |
2011年 | 683篇 |
2010年 | 437篇 |
2009年 | 438篇 |
2008年 | 409篇 |
2007年 | 347篇 |
2006年 | 398篇 |
2005年 | 369篇 |
2004年 | 341篇 |
2003年 | 305篇 |
2002年 | 254篇 |
2001年 | 214篇 |
2000年 | 213篇 |
1999年 | 194篇 |
1998年 | 198篇 |
1997年 | 151篇 |
1996年 | 142篇 |
1995年 | 120篇 |
1994年 | 130篇 |
1993年 | 46篇 |
1992年 | 73篇 |
1991年 | 29篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1978年 | 1篇 |
排序方式: 共有8868条查询结果,搜索用时 568 毫秒
51.
52.
M.A.K. Lodhi 《Energy Conversion and Management》1996,37(12):1677-1694
Solar ponds are probably the simplest technology available for the useful conversion of solar energy. The basic technology is proven. Solar ponds have been shown to be technically feasible and economically viable for many applications, particularly for thermal use. The electrical conversion and use of solar energy via solar ponds is still questionable, in general, for economic viability. By putting the untapped sources together in the South Plains region, it looks promising economically both for thermal and electrical conversions and applications. There are a number of alkaline lake basins randomly scattered in the South Plains region of the U.S.A. In that area, there are thousands of crude oil producing wells that produce brine in abundance. The selection of suitable alkaline lake basins as a solar pond site and as depository sites of brine from oil wells and the using of this brine and salty water from alkaline lakes makes the solar pond economically viable for both thermal and electrical demands in the area. 相似文献
53.
着重介绍了静态法测试低温下(-100~50℃)液体饱和蒸气压的原理及方法,给出了低温下液体全氟三乙胺饱和蒸气压的测试结果,并进行了讨论。 相似文献
54.
提取系统的冲击响应函数(impulse response function,IRF)是测量雷达系统性能指标的前提,IRF来自理想点目标的雷达图像。对于低频超宽带合成孔径雷达(ultra wide band synthetic aperture radar,UWB SAR),参考点目标的电磁散射特性是频率和方位角的函数,不满足理想点目标的散射特性要求。本文从IRF的定义出发,结合低频UWBSAR系统处理模型,利用二维数字聚焦方法消除杂波的影响,同时利用低频电磁散射数值建模的方法计算参考点目标的电磁散射特性,最后给出了计算系统IRF的方法。 相似文献
55.
本文介绍了以悬浮型速溶PHPAM为基础研制的低温油井堵水剂,讨论了影响堵水剂交联时间和成胶粘度的因素,制定了移动式弹性隔板堵水工艺并成功地应用于二连油田蒙古林砾岩油藏的油井堵水。该堵剂适用于30—60℃油井,交联时间可控、配制简便、快速、施工周期短。 相似文献
56.
多沙河流中的水厂取水口,枯水期经常存在淤沙,影响抽水。以往的治理方法多是采用丁坝群束水冲沙,但坝田淤高有碍行洪,对城市防洪不利.南区水厂采用潜坝方案,兼顾防洪.通航等要求,缩小治理范围,用十分简易的方法获得成功,且投资更省,值得在类似工程中推广运用. 相似文献
57.
文章讨论了PAGER控制器芯片(ZQD021)的系统设计,该控制器内部集成了FLASH,SRAM,POCSAG协议解码器和嵌入式MCU CORE。重点分析了芯片的可测性设计(DFT),内嵌FLASH设计,低功耗设计,其设计方法和思路对消费类和嵌入式控制芯片的设计有一定的借鉴意义。 相似文献
58.
Fatigue at high temperature is a complex phenomenon as it is influenced by a number of time-dependent processes which become
important at elevated temperatures. These processes include creep, oxidation, phase instabilities and dynamic strain ageing
(DSA), acting either independently or synergistically influence fatigue behaviour, often lowering the fatigue life. Current
design approaches employ linear summation of fatigue and creep damage with suitable factors on permissible damage to take
care of uncertainties in interaction between cyclic and time-dependent processes. It is, therefore, important to develop a
deeper understanding of the processes that occur during high temperature fatigue so that realistic life predictions could
be made.
Results on the high temperature fatigue behaviour of austenitic stainless steels, ferritic steels and nickel base alloys are
presented here. The important mechanisms of interaction of high temperature time-dependent processes with fatigue under various
conditions are discussed in detail. Emphasis is placed on cyclic stress response, fatigue life, deformation substructure and
fracture behaviour. This is followed by a review of important life prediction techniques under combined creep-fatigue loading
conditions. Life prediction techniques considered here include linear damage summation, strain range partitioning, ductility
exhaustion approach, frequency modified and frequency separation methods, techniques based on hysteresis energy and damage
rate models, and methods based on crack-cavitation interation models. 相似文献
59.
60.
Study on Numerical Simulation of Mold Filling and Solidification Processes under Pressure Conditions
The mold filling and solidification simulation for the high pressure die casting (HPDC) and low pressure die casting (LPDC) processes were studied.A mathematical model considering the turbulent flow and heat transfer phenomenon during the HPDC process has been established and paralled computation technique was used for the mold filling simulation of the process.The laminar flow characteristics of the LPDC process were studied and a simplified model for the mold filling process of wheel castings has been developed.For the solidification simulation under pressure conditions,the cyclic characteristics and the complicated boundary conditions were considered and techniques to improve the computational efficiency are discussed.A new criterion for predicting shrinkage porosity of Al alloy under low pressure condition has been developed in the solidification simulation process. 相似文献