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   5287篇
  免费   91篇
  国内免费   19篇
电工技术   264篇
综合类   7篇
化学工业   1006篇
金属工艺   155篇
机械仪表   105篇
建筑科学   73篇
矿业工程   2篇
能源动力   112篇
轻工业   308篇
水利工程   9篇
石油天然气   19篇
无线电   563篇
一般工业技术   1022篇
冶金工业   1285篇
原子能技术   160篇
自动化技术   307篇
  2023年   20篇
  2022年   51篇
  2021年   99篇
  2020年   39篇
  2019年   57篇
  2018年   62篇
  2017年   62篇
  2016年   78篇
  2015年   58篇
  2014年   85篇
  2013年   191篇
  2012年   169篇
  2011年   239篇
  2010年   162篇
  2009年   167篇
  2008年   175篇
  2007年   187篇
  2006年   157篇
  2005年   166篇
  2004年   142篇
  2003年   139篇
  2002年   106篇
  2001年   105篇
  2000年   104篇
  1999年   134篇
  1998年   536篇
  1997年   288篇
  1996年   217篇
  1995年   165篇
  1994年   131篇
  1993年   118篇
  1992年   78篇
  1991年   80篇
  1990年   62篇
  1989年   69篇
  1988年   50篇
  1987年   56篇
  1986年   60篇
  1985年   59篇
  1984年   54篇
  1983年   37篇
  1982年   42篇
  1981年   46篇
  1980年   45篇
  1979年   31篇
  1978年   29篇
  1977年   28篇
  1976年   74篇
  1975年   17篇
  1974年   14篇
排序方式: 共有5397条查询结果,搜索用时 0 毫秒
71.
One of the greatest challenges in a C/C++-based design methodology is efficiently mapping C/C++ models into hardware. Many networking and multimedia applications implemented in hardware or mixed hardware/software systems now use complex data structures stored in multiple memories, so many C/C++ features that were originally designed for software applications are now making their way into hardware. Such features include dynamic memory allocation and pointers for managing data. We present a solution for efficiently mapping arbitrary C code with pointers and malloc/free into hardware. Our solution, which fits current memory management methodologies, instantiates an application-specific hardware memory allocator coupled with a memory architecture. Our work also supports the resolution of pointers without restriction on the data structures. We present an implementation based on the SUIF framework along with case studies such as the realization of a video filter and an ATM segmentation engine  相似文献   
72.
The 80-mm-diameter ZnTe single crystals were successfully obtained by the liquid-encapsulated Kyropoulos (LEK) method. Both 〈100〉- and 〈110〉-oriented single crystals were reproducibly grown by using ZnTe seed crystals. Furthermore, 80-mm-diameter, 〈100〉 and 〈110〉 ZnTe single crystals were obtained by the pulling method. The etch pit densities (EPDs) of the grown crystals by the LEK and pulling methods were lower than 10,000 cm−2. The strain in the grown crystals by the pulling method was lower than that of LEK crystals.  相似文献   
73.
浸没式光刻的优势和可行性   总被引:3,自引:2,他引:3  
浸没式光刻通过高折射率的液体充入透镜底部和片子之间的空间使光学系统的数值孔径具有显著的优势。在193nm曝光系统中,水(折射率为1.44)被选作最佳的浸入液体。通过成像模拟,现已证明ArF穴193nm雪浸没式光刻(NA=1.05~1.23)与F2穴157nm雪干法穴NA=0.85~0.93雪光刻具有几乎相同的成像性能。结合流体力学和热模拟结果,讨论了ArF浸没式曝光设备的优势和可行性。  相似文献   
74.
Long-period fibre grating (LPFG) writing by a CO2 laser-annealing using a fibre-drawing process is demonstrated. The fibre in the drawing process was irradiated periodically by a CO2 laser to modify the refractive index. An LPFG with transmission loss of -10 dB and full width at half-maximum of 13 nm has been fabricated. Results show that the refractive index change was induced by stress at the moment of laser annealing  相似文献   
75.
Dye‐sensitized solar cells (DSSCs) are receiving considerable attention as low‐cost alternatives to conventional solar cells. In DSSCs based on liquid electrolytes, a photoelectric efficiency of 11 % has been achieved, but potential problems in sealing the cells and the low long‐term stability of these systems have impeded their practical use. Here, we present a thermoplastic gel electrolyte (TPGE) as an alternative to the liquid electrolytes used in DSSCs. The TPGE exhibits a thermoplastic character, high conductivity, long‐term stability, and can be prepared by a simple and convenient protocol. The viscosity, conductivity, and phase state of the TPGE can be controlled by tuning the composition. Using 40 wt % poly(ethylene glycol) (PEG) as the polymeric host, 60 wt % propylene carbonate (PC) as the solvent, and 0.65 M KI and 0.065 M I2 as the ionic conductors, a TPGE with a conductivity of 2.61 mS cm–2 is prepared. Based on this TPGE, a DSSC is fabricated with an overall light‐to‐electrical‐energy conversion efficiency of 7.22 % under 100 mW cm–2 irradiation. The present findings should accelerate the widespread use of DSSCs.  相似文献   
76.
A multi-level NAND Flash memory cell, using a new Side-WAll Transfer-Transistor (SWATT) structure, has been developed for a high performance and low bit cost Flash EEPROM. With the SWATT cell, a relatively wide threshold voltage (Vth) distribution of about 1.1 V is sufficient for a 4-level memory cell in contrast to a narrow 0.6 V distribution that is required for a conventional 4-level NAND cell. The key technology that allows this wide Vth distribution is the Transfer Transistor which is located at the side wall of the Shallow Trench Isolation (STI) region and is connected in parallel with the floating gate transistor. During read, the Transfer Transistors of the unselected cells (connected in series with the selected cell) function as pass transistors. So, even if the Vth of the unselected floating gate transistor is higher than the control gate voltage, the unselected cell will be in the ON state. As a result, the Vth distribution of the floating gate transistor can be wider and the programming can be faster because the number of program/verify cycles can be reduced. Furthermore, the SWATT cell results in a very small cell size of 0.57 μm2 for a 0.35 μm rule. Thus, the SWATT cell combines a small cell size with a multi-level scheme to realize a very low bit cost. This paper describes the process technology and the device performance of the SWATT cell, which can be used to realize NAND EEPROM's of 512 Mbit and beyond  相似文献   
77.
This paper describes a computer vision system for the automatic extraction and velocity measurement of moving leukocytes that adhere to microvessel walls from a sequence of images. The motion of these leukocytes can be visualized as motion along the wall contours. The authors use the constraint that the leukocytes move along the vessel wall contours to generate a spatiotemporal image, and the leukocyte motion is then extracted using the methods of spatiotemporal image analysis. The generated spatiotemporal image is processed by a special-purpose orientation-selective filter and a subsequent grouping process newly developed for this application. The orientation-selective filter is designed by considering the particular properties of the spatiotemporal image in this application in order to enhance only the traces of leukocytes. In the subsequent grouping process, leukocyte trace segments are selected and grouped among all the segments obtained by simple thresholding and skeletonizing operations. The authors show experimentally that the proposed method can stably extract leukocyte motion  相似文献   
78.
This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed  相似文献   
79.
The virtual path concept has several valuable features to construct an economical and efficient asynchronous transfer mode (ATM) network. One of them is bandwidth control which affords transmission efficiency improvement through statistical sharing of capacity. An effective bandwidth control algorithm and its calculated performance are described. Network performance with the algorithm is evaluated, and the bandwidth control is shown to successfully improve network transmission efficiency with only a slight increase in processing load compared to the fixed bandwidth scheme. A method is also proposed to equalize call loss probability for each virtual path. The effectiveness of the method is demonstrated by analysis  相似文献   
80.
A BiCMOS logic circuit applicable to sub-2-V digital circuits has been developed. A transiently saturated full-swing BiCMOS (TS-FS-BiCMOS) logic circuit operates twice as fast as CMOS at 1.5-V supply. A newly developed transient-saturation technique, with which bipolar transistors saturate only during switching periods, is the key to sub-2-V operation because a high-speed full-swing operation is achieved to remove the voltage loss due to the base-emitter turn-on voltage. Both small load dependence and small fan-in dependence of gate delay time are attained with this technique. A two-input gate fabricated with 0.3-μm BiCMOS technology verifies the performance advantage of TS-FS-BiCMOS over other BiCMOS circuits and CMOS at sub 2-V supply  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