全文获取类型
收费全文 | 6501篇 |
免费 | 452篇 |
国内免费 | 292篇 |
专业分类
电工技术 | 336篇 |
综合类 | 376篇 |
化学工业 | 1118篇 |
金属工艺 | 411篇 |
机械仪表 | 311篇 |
建筑科学 | 513篇 |
矿业工程 | 133篇 |
能源动力 | 223篇 |
轻工业 | 427篇 |
水利工程 | 101篇 |
石油天然气 | 267篇 |
武器工业 | 38篇 |
无线电 | 688篇 |
一般工业技术 | 995篇 |
冶金工业 | 440篇 |
原子能技术 | 78篇 |
自动化技术 | 790篇 |
出版年
2024年 | 24篇 |
2023年 | 96篇 |
2022年 | 162篇 |
2021年 | 243篇 |
2020年 | 191篇 |
2019年 | 182篇 |
2018年 | 154篇 |
2017年 | 182篇 |
2016年 | 186篇 |
2015年 | 188篇 |
2014年 | 269篇 |
2013年 | 374篇 |
2012年 | 329篇 |
2011年 | 410篇 |
2010年 | 346篇 |
2009年 | 320篇 |
2008年 | 348篇 |
2007年 | 324篇 |
2006年 | 362篇 |
2005年 | 322篇 |
2004年 | 219篇 |
2003年 | 223篇 |
2002年 | 174篇 |
2001年 | 168篇 |
2000年 | 155篇 |
1999年 | 201篇 |
1998年 | 182篇 |
1997年 | 137篇 |
1996年 | 140篇 |
1995年 | 115篇 |
1994年 | 95篇 |
1993年 | 83篇 |
1992年 | 54篇 |
1991年 | 56篇 |
1990年 | 37篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1969年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有7245条查询结果,搜索用时 18 毫秒
91.
92.
GNSS时间传递技术是卫星导航技术在时间频率领域的重要应用,也是时间传递的主要技术手段之一。随着我国北斗卫星导航系统的不断建设,北斗系统在时间频率领域应用的研究也逐步深入。主要基于北斗卫星导航系统特有的IGSO、MEO、GEO卫星星座,开展了基于北斗共视和载波相位时间传递算法研究,研制了北斗时间传递软件包(PPTSlo),并对其时间传递链路精度、稳定度进行了定性、定量分析,实验结果表明北斗共视时间传递精度优于6 ns,北斗载波相位时间传递精度能达到亚纳秒-纳秒精度。 相似文献
93.
J.P. Zhang D.Y. Chu S.L. Wu W.G. Bi R.C. Tiberio R.M. Joseph A. Taflove C.W. Tu S.T. Ho 《Photonics Technology Letters, IEEE》1996,8(4):491-493
A strongly-guided one-dimensional (1-D) waveguide called a photonic wire has high spontaneous emission coupling efficiency, enabling one to realize low-threshold lasers. Combined with the use of 1-D photonic bandgap structures consisting of arrays of holes etched within the photonic wire, novel microcavity lasers can be realized. We report the nanofabrication of a photonic bandgap structure for 1.5 /spl mu/m wavelength along a InGaAsP photonic wire, and discuss numerical simulations for its electrodynamics. 相似文献
94.
J.P. Zhang D.Y. Chu S.L. Wu W.G. Bi R.C. Tiberio C.W. Tu S.T. Ho 《Photonics Technology Letters, IEEE》1996,8(8):968-970
We have obtained directional light output from a recently realized InGaAsP photonic-wire microcavity ring lasers. The output was achieved by fabricating a 0.45-/spl mu/m-wide U-shape waveguide next to a 10-/spl mu/m diameter microcavity ring laser. The laser has a threshold pump power of around 124 /spl mu/W when optically pumped at 514 nm. It is comparable to the former structure without output coupling. The output coupling efficiency can be controlled carefully by choosing the spacing between the laser cavity and the waveguide. 相似文献
95.
一种工业用高频抗杂散小电容测量电路 总被引:1,自引:0,他引:1
介绍了一种工业用高频抗杂散小电容测量电路。该电路基于电荷转换原理,并采用差分结构产生输出信号。它有直至几兆赫兹的可编程测量频率。廉价且易于单片集成。通过采用特殊的开关安排,可以消除包括开关元件在内的杂散电容的影响,使得测量电路具有好的稳定性和线性衣0.3pF的分辨率。 相似文献
96.
97.
98.
本文提出,将煤矿井下喷雾降尘使用的降尘剂,研制成为同时具有减缓金属腐蚀功能的产品;选用多聚磷酸盐进行试验的结果证明这是可行的。 相似文献
99.
Performance of High-Reliability and High-Linearity InGaP/GaAs HBT PAs for Wireless Communication 总被引:1,自引:0,他引:1
An InGaP heterojunction-bipolar-transistor (HBT) power amplifier with the best linearity and high reliability is presented in this paper for use in wireless digital mobile communication systems. We optimized the linearity of a novel HBT device and investigated its reliability. Using SILVACO software, we performed a simulation of the HBT device. The best linearity, which was revealed for the device with a capacitance ratio Cbc (0/6 V), is 1.25 at a BVceo of 22 V. After the device was fabricated, a reasonably high PAE, i.e., ~ 55%, was obtained at 2.0 GHz, and an adjacent channel power ratio of over -48 dBc was achieved. In the reliability testing, the device, which was stressed at Vce = 3 V and JC = 25 kA/cm2 under 85°C ambient temperature and 85% humidity, showed no failure for more than 1100 h. No significant beta degradation was observed under an extreme current JC = 200 kA/cm2 stress under wafer-level electrical/thermal overstress tests. 相似文献
100.
Chengmo Yang Mingjing Chen Alex Orailoglu 《Design Automation for Embedded Systems》2010,14(3):265-284
Microcoded customized IPs offer superior performance and direct programmability of micro-architectural structures compared
to instruction-based processors, yet at the cost of drastically enlarged code sizes. Code compression can deliver size reductions
but necessitates attention to performance issues, so that the performance benefits of microcoded IPs are not squandered in
the process. To attain this goal, we propose in this paper a fast code compression technique through exploiting the fact that
the microcodes contain a sizable amount of unspecified bits. Although the values and the positions of the specified bits are
highly irregular, the proposed technique can still flexibly and precisely fill in these fully specified bits through utilizing
a linear network. The linear property inherent in the compression strategy in turn enables the development of an extremely
low-overhead decompression engine. At runtime, the decompressed code can be generated in such a way that all the specified
bits can be filled as required by a fixed-bandwidth XOR network. The combination of the proposed flexible XOR-based network
with a minimum two-level storage for highly specified fields, such as immediate values, offers utmost code compression, attained
within a negligible amount of performance and hardware overhead. 相似文献