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   5197篇
  免费   95篇
  国内免费   8篇
电工技术   178篇
综合类   4篇
化学工业   938篇
金属工艺   122篇
机械仪表   114篇
建筑科学   105篇
矿业工程   1篇
能源动力   112篇
轻工业   416篇
水利工程   26篇
石油天然气   7篇
无线电   545篇
一般工业技术   901篇
冶金工业   1351篇
原子能技术   118篇
自动化技术   362篇
  2023年   26篇
  2022年   51篇
  2021年   88篇
  2020年   51篇
  2019年   55篇
  2018年   70篇
  2017年   51篇
  2016年   78篇
  2015年   45篇
  2014年   100篇
  2013年   240篇
  2012年   148篇
  2011年   222篇
  2010年   148篇
  2009年   189篇
  2008年   184篇
  2007年   156篇
  2006年   169篇
  2005年   141篇
  2004年   139篇
  2003年   150篇
  2002年   133篇
  2001年   100篇
  2000年   92篇
  1999年   139篇
  1998年   493篇
  1997年   341篇
  1996年   254篇
  1995年   135篇
  1994年   131篇
  1993年   145篇
  1992年   61篇
  1991年   59篇
  1990年   60篇
  1989年   54篇
  1988年   49篇
  1987年   34篇
  1986年   53篇
  1985年   58篇
  1984年   39篇
  1983年   42篇
  1982年   41篇
  1981年   47篇
  1980年   40篇
  1979年   28篇
  1978年   18篇
  1977年   28篇
  1976年   48篇
  1975年   13篇
  1973年   13篇
排序方式: 共有5300条查询结果,搜索用时 15 毫秒
41.
Liquid marble (LM) is a droplet that is wrapped by hydrophobic solid particles, which behave as a non-wetting soft solid. Based on these properties, LM can be applied in fluidics and soft device applications. A wide variety of functional particles have been synthesized to form functional LMs. However, the formation of multifunctional LMs by integrating several types of functional particles is challenging. Here, a general strategy for the flexible patterning of functional particles on droplet surfaces in a patchwork-like design is reported. It is shown that LMs can switch their macroscopic behavior between a stable and active state on super-repellent surfaces in situ by jamming/unjamming the surface particles. Active LMs hydrostatically coalesce to form a self-sorted particle pattern on the droplet surface. With the support of LM handling robotics, on-demand cyclic activation–manipulation–coalescence–stabilization protocols by LMs with different sizes and particle types result in the reliable design of multi-faced LMs. Based on this concept, a single bi-functional LM is designed from two mono-functional LMs as an advanced droplet carrier.  相似文献   
42.
In bionic technology, it has become an innovative process imitating the functionality and structuralism of human biological systems to exploit advanced artificial intelligent machines. Bionics plays a significant role in environmental protection, especially for its low energy loss. By fusing the concept of receptor-like sensing component and synapse-like memory, the photoactive electro-controlled optical sensory memory (PE-SM) is proposed and realized in a single device, which endows a simple methodology of reducing power consumption by photoactive electro-control. The PE-SM is the system built with the stacked atomically thick materials, in which rhenium diselenide serves as a robust photosensor, hexagonal boron nitride serves as a tunneling dielectric, and graphene serves as a charge-storage layer. With the features of the PE-SM, it performs synaptic metaplasticities under optical spikes. In addition, a simulated spiking neural network composed of 24 × 24 PE-SMs is further presented in an unsupervised machine learning environment, performing image recognition via the Hebbian rule. The PE-SM not only improves the neuromorphic computing efficiency but also simplifies the circuit-size structure. Eventually, the concept of photoactive electro-control can extend to other photosensitive 2D materials and provide a new approach of constructing either visual perception memory or photonic synaptic devices.  相似文献   
43.
A widely tunable laser, consisting of a 100 GHz FSR triple-ring resonator and a semiconductor optical amplifier, is presented. The 100 GHz FSR ring resonator makes it possible to demonstrate 96 nm wavelength tuning with stable single-mode operation produced by a large threshold gain difference  相似文献   
44.
A scalable single-chip 422P@ML MPEG-2 video, audio, and system encoder LSI for portable 422P@HL system is described. The encoder LSI is implemented using 0.13-μm embedded DRAM technology. It integrates 3-M logic gates and 64-Mb DRAM in an area of 99-mm2. The power consumption is suppressed to 0.7 W by adopting a low-power DRAM core. It performs real-time 422P@ML video encoding, audio encoding, and system encoding with no external DRAM. Furthermore, the encoder LSI realizes a 422P@HL video encoder with multichip configuration, due to its scalable architecture. This results in a PC-card size 422P@HL encoder for portable HDTV codec system  相似文献   
45.
The reliability of InP-based HEMTs is studied, focussing on how it is affected by the doped layer material and gate recess structure. Bias-and-temperature stress tests reveal that fluorine-induced donor passivation in the recess region, formed adjacent to the gate electrode, causes the source resistance (Rs) to increase at large drain bias voltages. The increase in Rs can be prevented by using InP or InAlP as the carrier supply layer material instead of InAlAs. On the other hand, the increase in the drain resistance (Rd) does not depend on the material of the carrier supply layer, which suggests that a mechanism different from that in the case of Rs should be considered. It is also found that a deep gate recess suppresses the increase in Rd after long-term stressing.  相似文献   
46.
Photosensitivity in a perfluoropolymer (CYTOP) optical fibre is investigated. Significant diffraction has been observed from transmission gratings made from the fibre. A maximum diffraction efficiency of 1.6% has been achieved, corresponding to an index change ≃3×10-4. The study demonstrates for the first time the existence of significant photosensitivity and the feasibility of writing a Bragg grating in a CYTOP fibre  相似文献   
47.
Photovoltaic modules must generally be connected in series in order to produce the voltage required to efficiently drive an inverter. However, if even a very small part of photovoltaic module (PV module) is prevented from receiving light, the generation power of the PV module is decreased disproportionately. This greater than expected decrease occurs because PV modules which do not receive adequate light cannot operate on the normal operating point, but rather operate as loads. As a result, the total power from the PV modules is decreased if even only a small part of the PV modules are shaded. In the present paper, a novel circuit, referred to as the generation control circuit (GCC), which enables maximum power to be obtained from all of the PV modules even if some of the modules are prevented from receiving light. The proposed circuit enables the individual PV modules to operate effectively at the maximum power point tracking, irrespective of the series connected PV module system. In addition, the total generated power is shown experimentally to increase for the experimental set-up used in the present study  相似文献   
48.
Plasma membrane was isolated from the salt-tolerant yeast Candida versatilis and the ATPase in plasma membrane was characterized. The ATPase was a typical H+-ATPase with similar properties to the Saccharomyces cerevisiae and Zygosaccharomyces rouxii enzymes. It was reacted with antibody (IgG) raised against S. cerevisiae plasma membrane H+-ATPase. The ATPase activity was not changed by adding NaCl and KCl to the assay solutions, but was increased by NH, especially by ammonium sulfate. In vivo stimulation of ATPase activity was observed by the addition of NaCl into the culture medium, as observed in Z. rouxii. No in vivo activation of H+-ATPase by glucose metabolism was observed in C. versatilis cells and the activity was independent of the growth phase, like Z. rouxii and unlike S. cerevisiae cells.  相似文献   
49.
This paper presents a motion estimation and compensation large scale integration (LSI) for the MPEG2 standard. An embedded RISC processor and special hardware modules enable the LSI to achieve a sufficient ability to perform real-time operation and provide the availability to realize many kinds of block matching algorithms. Using a three-step hierarchical telescopic search algorithm, a single chip accomplishes real-time motion estimation with search ranges of ±32.5×±32.5 pixels for motion vectors. The chip was fabricated using 0.5-μm CMOS technology and has an area of 16.5×16.5 mm2 and 2.0 M transistors  相似文献   
50.
An experimental 1.5-V 64-Mb DRAM   总被引:1,自引:0,他引:1  
Low-voltage circuit technologies for higher-density dynamic RAMs (DRAMs) and their application to an experimental 64-Mb DRAM with a 1.5-V internal operating voltage are presented. A complementary current sensing scheme is proposed to reduce data transmission delay. A speed improvement of 20 ns was achieved when utilizing a 1.5-V power supply. An accurate and speed-enhanced half-VCC voltage generator with a current-mirror amplifier and tri-state buffer is proposed. With it, a response time reduction of about 1.5 decades was realized. A word-line driver with a charge-pump circuit was developed to achieve a high boost ratio. A ratio of about 1.8 was obtained from a power supply voltage as low as 1.0 V. A 1.28 μm2 crown-shaped stacked-capacitor (CROWN) cell was also made to ensure a sufficient storage charge and to minimize data-line interference noise. An experimental 1.5 V 64 Mb DRAM was designed and fabricated with these technologies and 0.3 μm electron-beam lithography. A typical access time of 70 ns was obtained, and a further reduction of 50 ns is expected based on simulation results. Thus, a high-speed performance, comparable to that of 16-Mb DRAMs, can be achieved with a typical power dissipation of 44 mW, one tenth that of 16-Mb DRAMs. This indicates that a low-voltage battery operation is a promising target for future DRAMs  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