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   12091篇
  免费   1238篇
  国内免费   604篇
电工技术   660篇
综合类   824篇
化学工业   2172篇
金属工艺   693篇
机械仪表   733篇
建筑科学   945篇
矿业工程   300篇
能源动力   334篇
轻工业   894篇
水利工程   226篇
石油天然气   648篇
武器工业   90篇
无线电   1573篇
一般工业技术   1430篇
冶金工业   542篇
原子能技术   130篇
自动化技术   1739篇
  2024年   61篇
  2023年   222篇
  2022年   446篇
  2021年   560篇
  2020年   399篇
  2019年   340篇
  2018年   383篇
  2017年   473篇
  2016年   397篇
  2015年   470篇
  2014年   631篇
  2013年   762篇
  2012年   741篇
  2011年   831篇
  2010年   745篇
  2009年   624篇
  2008年   617篇
  2007年   614篇
  2006年   592篇
  2005年   432篇
  2004年   392篇
  2003年   498篇
  2002年   596篇
  2001年   492篇
  2000年   316篇
  1999年   274篇
  1998年   199篇
  1997年   158篇
  1996年   154篇
  1995年   108篇
  1994年   93篇
  1993年   69篇
  1992年   48篇
  1991年   51篇
  1990年   34篇
  1989年   27篇
  1988年   17篇
  1987年   12篇
  1986年   17篇
  1985年   9篇
  1984年   7篇
  1983年   5篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1979年   3篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
 分析了如何利用中间件技术支持专业知识获取的问题.提出了基于XML,SOAP,UDDI和WSDL的web服务技术的专业知识获取的中间件应用模式,它可以有效解决消息传送、服务功能的抽象描述以及服务在网络上的发布与发现等问题。以固定瓦推力滑动轴承的性能参数计算Web服务为实例,指出web服务是分布式设计知识获取和知识资源集成的有效途径.  相似文献   
72.
赵有生 《山西煤炭》2003,23(3):41-43
介绍了9号、10号、11号煤层开采中顶板管理的具体做法,对特殊时期的初采初放和末采回收也做了阐述,并对特殊地质条件下的顶板管理提出了可行的方法。  相似文献   
73.
74.
依据丰满漉域的水文气象资料,计算丰满流域可能最大暴雨,推求白丰区间的可能最大洪水并进行成果合理性分析.  相似文献   
75.
Liming Tang  Hu You  Ji Feng 《Thin solid films》2007,515(5):2998-3004
An acrylated hyperbranched poly(ester-amine) (HPEA) synthesized from piperazine and trimethylolpropanetriacrylate at a molar ratio of 1:1.42 was used as the polycation to form self-assembled films by layer-by-layer dipping with poly(sodium-p-styrenesulfonate) as the polyanion. The surface morphology and hydrophilicity of the films with HPEA as the outmost layer were controlled by adjusting the solution pH of HPEA. Due to the existence of many acrylate groups, the films with HPEA as the outmost layer were further reacted with a series of reagents, including piperazine, piperidine, laurylamine and p-phenylenediamine. The surface reactions of the films depended on both the nature of the reagents and the morphology of the initial surface. In the presence of the strong basic amines, piperazine and piperidine, the films dissolved extensively into the solution. In the case of laurylamine, a modified film with an opaque appearance was obtained due to the crystallization of long alkyl chains. With the weak basic amine p-phenylenediamine as the reactant, the film was effectively modified without any change in the surface morphology.  相似文献   
76.
介绍了一个应用力传感器组成的智能机器人精密装配作业的宏/微操作系统,它能够完成一般凸形销孔零件沿任意方向的精密装配作业。  相似文献   
77.
This paper presents a multistage amplifier for low-voltage applications (<2 V). The amplifier consists of simple (noncascode) low gain stages and is stabilized using a nested transconductance-capacitance compensation (NGCC) scheme. The resulting topology is similar to the well known nested Miller compensation (NMC) multistage amplifier, except that the proposed topology contains extra G m feedforward stages which are used to enhance the amplifier performance. The NGCC simplifies the transfer function of the proposed multistage amplifier which, in turn, simplifies its stability conditions. A comparison between the NGCC and NMC shows that the NGCC has wider bandwidth and is easier to stabilize. A four-stage NGCC amplifier has been fabricated using a 2-μm CMOS process and is tested using a ±1.0 V power supply. A dc gain of 100 dB has been measured. A gain bandwidth product of 1 MHz with 58° of phase margin and power of 1.4 mW can be achieved. The op amp occupies an active area of 0.22 mm2. Step response shows that the op amp is stable  相似文献   
78.
Due to their simplicity and intuitiveness, swept surfaces are widely used in many surface modelling applications. In this paper, we present a versatile swept surface technique called the boundary constrained swept surfaces. The most distinct feature is its ability to satisfy boundary constraints, including the shape and tangent conditions at the boundaries of a swept surface. This permits significantly varying surfaces to be both modelled and smoothly assembled, leading to the construction of complex objects. The representation, similar to an ordinary swept surface, is analytical in nature and thus it is light in storage cost and numerically very stable to compute. We also introduce a number of useful shape manipulation tools, such as sculpting forces, to deform a surface both locally and globally. In addition to being a complementary method to the mainstream surface modelling and deformation techniques, we have found it very effective in automatically rebuilding existing complex models. Model reconstruction is arguably one of the most laborious and expensive tasks in modelling complex animated characters. We demonstrate how our technique can be used to automate this process.  相似文献   
79.
在3.39μm波段甲烷吸收特性的测量与应用研究   总被引:1,自引:0,他引:1  
报道了甲烷气体在3.39μm波段吸收特性的研究结果,及其在3.39μm波段多波长干涉测量中的应用。通过改变甲烷吸收室的充气参数,使激光器工作在双等光强工作点,并完成了绝对距离的干涉测量。  相似文献   
80.
Experimental thermal hydraulic research has been conducted at Oregon State University for the purpose of assessing the performance of a new reactor design concept, the multi-application small light water reactor (MASLWR). The MASLWR is a pressurized light water reactor design with a net output of 35 MWe that uses natural circulation in both normal and transient operation. Due to its small size, portability and modularity, the MASLWR design is well suited to help fill the potential need for grid appropriate reactor designs for smaller electricity grids as may be found in developing or remote regions. The purpose of the OSU MASLWR test facility is to assess the operation of the MASLWR under normal full operating pressure and full temperature conditions and to assess the passive safety systems under transient conditions. The data generated by the testing program will be used to assess computer code calculations and to provide a better understanding of the thermal-hydraulic phenomena in the design of the MASLWR NSSS. During this testing program, four tests were conducted at the OSU MASLWR test facility. These tests included one design basis accident and one beyond design basis accident. During the performance of these tests, plant operations to include start up, normal operation and shut down evolutions were demonstrated successfully.  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