全文获取类型
收费全文 | 20186篇 |
免费 | 2202篇 |
国内免费 | 1061篇 |
专业分类
电工技术 | 1258篇 |
技术理论 | 1篇 |
综合类 | 1360篇 |
化学工业 | 3221篇 |
金属工艺 | 1342篇 |
机械仪表 | 1454篇 |
建筑科学 | 1560篇 |
矿业工程 | 628篇 |
能源动力 | 532篇 |
轻工业 | 1385篇 |
水利工程 | 459篇 |
石油天然气 | 1158篇 |
武器工业 | 216篇 |
无线电 | 2302篇 |
一般工业技术 | 2390篇 |
冶金工业 | 1068篇 |
原子能技术 | 346篇 |
自动化技术 | 2769篇 |
出版年
2024年 | 137篇 |
2023年 | 417篇 |
2022年 | 743篇 |
2021年 | 976篇 |
2020年 | 801篇 |
2019年 | 677篇 |
2018年 | 700篇 |
2017年 | 800篇 |
2016年 | 717篇 |
2015年 | 1078篇 |
2014年 | 1317篇 |
2013年 | 1473篇 |
2012年 | 1556篇 |
2011年 | 1419篇 |
2010年 | 1295篇 |
2009年 | 1159篇 |
2008年 | 1091篇 |
2007年 | 1068篇 |
2006年 | 1021篇 |
2005年 | 810篇 |
2004年 | 535篇 |
2003年 | 469篇 |
2002年 | 472篇 |
2001年 | 411篇 |
2000年 | 341篇 |
1999年 | 314篇 |
1998年 | 248篇 |
1997年 | 200篇 |
1996年 | 200篇 |
1995年 | 162篇 |
1994年 | 133篇 |
1993年 | 89篇 |
1992年 | 92篇 |
1991年 | 64篇 |
1990年 | 53篇 |
1989年 | 38篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 34篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
On Controllability of Switched Linear Systems 总被引:1,自引:0,他引:1
Zhijian Ji Long Wang Xiaoxia Guo 《Automatic Control, IEEE Transactions on》2008,53(3):796-801
This paper investigates the number of switchings and design of switching sequences for controllability of switched linear systems. Two related results are established. One is a new constructive approach to designing switching sequences. The controllable state set of each switching sequence designed via the approach coincides with the controllable subspace of switched linear systems. The other is a well-estimated value for the minimum number of switchings required for controllability. Each state in the controllable subspace can be steered to origin within this value of switching times. 相似文献
92.
An application of MODIS data to snow cover monitoring in a pastoral area: A case study in Northern Xinjiang, China 总被引:3,自引:0,他引:3
Tian Gang Liang Xing Yuan Liu Wen Long Li Zheng Gang Guo Ji Zhou Ren 《Remote sensing of environment》2008,112(4):1514-1526
Snow is an important land cover on the earth's surface. It is characterized by its changing nature. Monitoring snow cover extent plays a significant role in dynamic studies and prevention of snow-caused disasters in pastoral areas. Using NASA EOS Terra/MODIS snow cover products and in situ observation data during the four snow seasons from November 1 to March 31 of year 2001 to 2005 in northern Xinjiang area, the accuracy of MODIS snow cover mapping algorithm under varied snow depth and land cover types was analyzed. The overall accuracy of MODIS daily snow cover mapping algorithm in clear sky condition is high at 98.5%; snow agreement reaches 98.2%, and ranges from 77.8% to 100% over the 4-year period for individual sites. Snow depth (SD) is one of the major factors affecting the accuracy of MODIS snow cover maps. MODIS does not identify any snow for SD less than 0.5 cm. The overall accuracy increases with snow depth if SD is equal to or greater than 3 cm, and decreases for SD below 3 cm. Land cover has an important influence in the accuracy of MODIS snow cover maps. The use of MOD10A1 snow cover products is severely affected by cloud cover. The 8-day composite products of MOD10A2 can effectively minimize the effect of cloud cover in most cases. Cloud cover in excess of 10% occurs on 99% of the MOD10A1 products and 14.7% of the MOD10A2 products analyzed during the four snow seasons. User-defined multiple day composite images based on MOD10A1, with flexibilities of selecting composite period, starting and ending date and composite sequence of MOD10A1 products, have an advantage in effectively monitoring snow cover extent for regional snow-caused disasters in pastoral areas. 相似文献
93.
Yi?GongEmail author Wei?Chen Long?Zhang Yun?Zeng Qunsheng?Peng 《The Visual computer》2008,24(2):95-103
In this paper we introduce an approximate image-space approach for real-time rendering of deformable translucent models by
flattening the geometry and lighting information of objects into textures to calculate multi-scattering in texture spaces.
We decompose the process into two stages, called the gathering and scattering corresponding to the computations for incident and exident irradiance respectively. We derive a simplified illumination model
for the gathering of the incident irradiance, which is amenable for deformable models using two auxiliary textures. In the scattering stage,
we adopt two modes for efficient accomplishment of the view-dependent scattering. Our approach is implemented by fully exploiting the capabilities of graphics processing units (GPUs). It achieves visually
plausible results and real-time frame rates for deformable models on commodity desktop PCs. 相似文献
94.
This paper investigates the controllability of multi-agent systems based on agreement protocols. First, for a group of single-integrator
agents, the controllability is studied in a unified framework for both networks with leader-following structure and networks
with undirected graph. Some new necessary/sufficient conditions for the controllability of networks of single-integrator agents
are established. Second, we prove that, under the same topology and same prescribed leaders, a network of high-order dynamic
agents is completely controllable if and only if so is a network of single-integrator agents. Third, how the selection of
leaders and the coupling weights of graphs affect the controllability is analyzed. Finally, some numerical simulations are
presented to demonstrate the effectiveness of the theoretical results. 相似文献
95.
提出了一种高效并行的二维离散提升小波(DWT)变换结构,该结构只需要7行教据缓存,即可实现行和列方向同时进行滤波变换.采用一种基于CSD编码和优化的移位加操作实现常系数乘法器,整个小波变换插入多级流水线寄存器,加快了处理速度.用VHDL设计可自动验证的testbench,通过matlab+modelsim联合仿真能方便有效地对IP核进行验证.此IP核具有3个可配置参数,分别为图像尺寸、位宽、小波变换的级数,可方便重用.该IP核已经在XC2VP20 FPGA上实现,并能稳定工作在60MHz时钟频率下,其处理512512 8bil图像的速度可达240帧/s,完全能满足高速图像实时处理要求. 相似文献
96.
预期的研究成果是拥有自主知识产权的振动噪声数据库.通过建立这样一个数据信息规模较大、可用性强、开放式的振动噪声数据库,为振动噪声试验工作提供坚实的基础.对系统进行了概要的介绍,提出了一套基于J2EE框架平台的系统解决方案.整个系统采用了MVC设计模式,还采用了Struts、Spring、Hibernate等多种技术,使得系统成为以网络为系统平台,基于B/S结构、具有结构清晰,具有良好的可扩展性、可维护性以及重用性的主题数据库应用系统. 相似文献
97.
98.
采用自顶向下的模块化设计思想,介绍了一种采用级联结构在FPGA上实现ⅡR数字滤波器的设计方案.设计ⅡR数字滤波器的二阶节,将二阶节ⅡR数字滤波器级联实现高阶ⅡR数字滤波器,从而实现通过修改外围参数来改变滤波器的频率响应,根据不同的要求在不同规模的FPGA上加以实现. 相似文献
99.
100.
幽门螺杆菌TNF-α诱导蛋白的生物信息学分析 总被引:1,自引:0,他引:1
肿瘤坏死因子诱导蛋白Tipα是幽门螺杆菌特有的一个膜相关蛋白.它可以激活核因子κB,并诱导多种细胞因子和趋化因子的表达,导致胃炎和随后的肿瘤发生.它是幽门螺杆菌和胃癌发生之间的关键分子.本文利用生物信息学工具分析Tipα序列,预测其信号肽、跨膜区、疏水性、二级结构、三级结构等性质.结果:Tipα具有一段信号肽、脂蛋白信号肽酶切位点及脂盒模体.另外该蛋白没有跨膜区,可能是一个外周膜蛋白.Tipα的三级结构说明,该蛋白形成了一个致密的球状结构,Tipα的二级结构以α螺旋为主. 相似文献