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   76850篇
  免费   5241篇
  国内免费   1621篇
电工技术   2436篇
技术理论   2篇
综合类   2061篇
化学工业   14967篇
金属工艺   3749篇
机械仪表   4972篇
建筑科学   3087篇
矿业工程   710篇
能源动力   3076篇
轻工业   5979篇
水利工程   863篇
石油天然气   1505篇
武器工业   195篇
无线电   10986篇
一般工业技术   14005篇
冶金工业   5050篇
原子能技术   991篇
自动化技术   9078篇
  2024年   210篇
  2023年   1103篇
  2022年   1739篇
  2021年   2600篇
  2020年   1912篇
  2019年   1958篇
  2018年   2318篇
  2017年   2318篇
  2016年   2685篇
  2015年   2390篇
  2014年   3433篇
  2013年   4591篇
  2012年   4950篇
  2011年   5786篇
  2010年   4444篇
  2009年   4484篇
  2008年   4288篇
  2007年   3658篇
  2006年   3435篇
  2005年   2956篇
  2004年   2499篇
  2003年   2513篇
  2002年   2509篇
  2001年   2186篇
  2000年   1710篇
  1999年   1563篇
  1998年   1975篇
  1997年   1385篇
  1996年   1169篇
  1995年   865篇
  1994年   663篇
  1993年   576篇
  1992年   439篇
  1991年   374篇
  1990年   328篇
  1989年   301篇
  1988年   262篇
  1987年   210篇
  1986年   155篇
  1985年   134篇
  1984年   107篇
  1983年   74篇
  1982年   51篇
  1981年   47篇
  1980年   42篇
  1979年   40篇
  1978年   32篇
  1977年   41篇
  1976年   68篇
  1973年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We report on the significantly enhanced photoluminescence (PL) of hybrid double‐layered nanotubes (HDLNTs) consisting of poly(3‐methylthiophene) (P3MT) nanotubes with various doping levels enveloped by an inorganic, nickel (Ni) metal nanotube. From laser confocal microscopy PL experiments on a single strand of the doped‐P3MT nanotubes and of their HDLNTs, the PL peak intensity of the HDLNT systems increased remarkably up to ~350 times as the doping level of the P3MT nanotubes of the HDLNTs increased, which was confirmed by measurements of the quantum yield. In a comparison of the normalized ultraviolet and visible absorption spectra of the doped‐P3MT nanotubes and their HDLNTs, new absorption peaks corresponding to surface‐plasmon (SP) energy were created at 563 and 615 nm after the nanoscale Ni metal coating onto the P3MT nanotubes, and their intensity increased on increasing the doping level of the P3MT nanotube. The doping‐induced bipolaron peaks of the HDLNTs of doped‐P3MT/Ni were relatively reduced, compared with those of the doped‐P3MT nanotubes before the Ni coating, due to the charge‐transfer effect in the SP‐resonance (SPR) coupling. Both energy‐transfer and charge‐transfer effects due to SP resonance contributed to the very‐large enhancement of the PL efficiency of the doped‐P3MT‐based HDLNTs.  相似文献   
992.
This paper proposes a test algorithm that can detect and diagnose all the faults occurring in dual‐port memories that can be accessed simultaneously through two ports. In this paper, we develop a new diagnosis algorithm that classifies faults in detail when they are detected while the test process is being developed. The algorithm is particularly efficient because it uses information that can be obtained by test results as well as results using an additional diagnosis pattern. The algorithm can also diagnose various fault models for dual‐port memories.  相似文献   
993.
Recently, NAND flash memory has emerged as a next generation storage device because it has several advantages, such as low power consumption, shock resistance, and so on. However, it is necessary to use a flash translation layer (FTL) to intermediate between NAND flash memory and conventional file systems because of the unique hardware characteristics of flash memory. This paper proposes a new clustered FTL (CFTL) that uses clustered hash tables and a two‐level software cache technique. The CFTL can anticipate consecutive addresses from the host because the clustered hash table uses the locality of reference in a large address space. It also adaptively switches logical addresses to physical addresses in the flash memory by using block mapping, page mapping, and a two‐level software cache technique. Furthermore, anticipatory I/O management using continuity counters and a prefetch scheme enables fast address translation. Experimental results show that the proposed address translation mechanism for CFTL provides better performance in address translation and memory space usage than the well‐known NAND FTL (NFTL) and adaptive FTL (AFTL).  相似文献   
994.
A novel linear switched termination active cross‐coupled low‐voltage differential signaling (LVDS) transceiver operating at 1.5 GHz clock frequency is presented. On the transmitter side, an active cross‐coupled linear output driver and a switched termination scheme are applied to achieve high speed with low current. On the receiver side, a shared preamplifier scheme is employed to reduce power consumption. The proposed LVDS transceiver implemented in an 80 nm CMOS process is successfully demonstrated to provide a data rate of 6 Gbps/pin, an output data window of 147 ps peak‐to‐peak, and a data swing of 196 mV. The power consumption is measured to be 4.2 mW/pin at 1.2 V.  相似文献   
995.
Analysis according to the EBC protocol, immunological determination of a α-amylase and estimation of malt β-glucan using the Calcofluor-FIA method, were used to screen 327 barley breeding lines for malting quality. The results obtained with the α-amylase and β-glucan methods are highly correlated to the important malt quality paramters: extract yield and β-glucan content in the wort. It is recommended that either of the two methods, which are simple to perform are used as prescreening tools in breeding programmes for malting barley.  相似文献   
996.
纪越峰  庄晓实 《电子学报》1995,23(4):39-43,9
本文对引导扰码进行了更深入的研究,不仅证明了在满足一定条件下引导扰码可产生类似于白噪声的输出特性,而且还建立了硬件和软件二套技术方案并实验成功,经测试检验,证明完全可行。  相似文献   
997.
In this paper, we study a bandwidth allocation strategy with state-dependent Bernoulli access (SDBA) and preemptive priority (PP) to serve wideband (WB) and narrowband (NB) traffics in wideband integrated networks. In this strategy, total bandwidth is divided into three regions, bandwidth for WB traffic, bandwidth for NB traffic and shared bandwidth. Under this environment, the minimum usable bandwidths for queueable NB traffic are controlled adaptively according to the system states. And the bandwidths used by the NB traffic are probabilistically preempted by a blockable WB traffic, when the number of NB messages waiting in the buffer is varying. The strategy is analyzed using the Neuts' matrix analytic approach. It shows better performance than other schemes which do not use SDBA and PP. In addition, the strategy with multiple buffer thresholds controls bandwidth allocation more dynamically and shows more performance build-up than the strategy with single buffer threshold.  相似文献   
998.
Adaptive robust impulse noise filtering   总被引:1,自引:0,他引:1  
It is well known that when data is contaminated by non-Gaussian noise, conventional linear systems may perform poorly. The paper presents an adaptive robust filter (adaptive preprocessor) for canceling impulsive components when the nominal process (or background noise) is a correlated, possibly nonstationary, Gaussian process. The proposed preprocessor does not require iterative and/or batch processing or prior knowledge about the nominal Gaussian process; consequently, it can be implemented in real time and adapt to changes in the environment. Based on simulation results, the proposed adaptive preprocessor shows superior performances over presently available techniques for cleaning impulse noise. Using the proposed adaptive preprocessor to clean the impulsive components in received data samples, conventional linear systems based on the Gaussian assumption can work in an impulsive environment with little if any modification. The technique is applicable to a wide range of problems, such as detection, power spectral estimation, and jamming or clutter suppression in impulsive environments  相似文献   
999.
SIR-C data quality and calibration results   总被引:5,自引:0,他引:5  
The SIR-C/X-SAR imaging radar took its first flight on the Space Shuttle Endeavour in April 1994 and flew for a second time in October 1994. This multifrequency radar has fully polarimetric capability at L- and C-band, and a single polarization at X-band (X-SAR). The Endeavour missions were designated the Space Radar Laboratory-1 (SRL-1) and -2 (SRL-2). Calibration of polarimetric L- and C-band data for all the different modes SIR-C offers is an especially complicated problem. The solution involves extensive analysis of pre-flight test data to come up with a model of the system, analysis of in-flight test data to determine the antenna pattern and gains of the system during operation, and analysis of data from over fourteen calibration sites distributed around the SIR-C/X-SAR orbit track. The SRL missions were the first time a multifrequency polarimetric imaging radar employing a phased array antenna has been flown in space. Calibration of SIR-C data products involved some unique technical problems given the complexity of the radar system. In this paper, the approach adopted for calibration of SIR-C data is described and the calibration performance of the data products is presented  相似文献   
1000.
Kim  Sungwook 《Wireless Networks》2017,23(2):641-650

For the next generation wireless networks, machine type communication (MTC) is gaining an enormous interest as a new communication paradigm. MTC is expected to become a cost-effective solution for improving the wireless communication performance. In MTC, one of the most critical issues is to support data transfers among devices without human interaction. In this study, we introduce a new MTC control scheme for the future network infrastructure. To effectively support a large number of MTC devices, we investigate a dual-level interaction mechanism by employing the timed strategy game model. In dynamic wireless network environments, our timed strategic game approach can practically adapt current system conditions while maximizing system performance. Main contribution of this research is to show a way of MTC system modeling based on the competitive and cooperative manner. Finally, numerical simulations illustrate the validity of our game-based approach. Our solution enables a better network resource utilization for heterogeneous traffic services in contrast to existing schemes.

  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