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   7110篇
  免费   664篇
  国内免费   315篇
电工技术   383篇
综合类   449篇
化学工业   1110篇
金属工艺   502篇
机械仪表   498篇
建筑科学   578篇
矿业工程   136篇
能源动力   183篇
轻工业   505篇
水利工程   104篇
石油天然气   300篇
武器工业   76篇
无线电   964篇
一般工业技术   982篇
冶金工业   353篇
原子能技术   75篇
自动化技术   891篇
  2024年   34篇
  2023年   134篇
  2022年   264篇
  2021年   384篇
  2020年   293篇
  2019年   230篇
  2018年   224篇
  2017年   250篇
  2016年   223篇
  2015年   260篇
  2014年   307篇
  2013年   377篇
  2012年   419篇
  2011年   416篇
  2010年   413篇
  2009年   383篇
  2008年   389篇
  2007年   382篇
  2006年   386篇
  2005年   302篇
  2004年   196篇
  2003年   180篇
  2002年   186篇
  2001年   145篇
  2000年   182篇
  1999年   173篇
  1998年   136篇
  1997年   144篇
  1996年   109篇
  1995年   99篇
  1994年   84篇
  1993年   91篇
  1992年   71篇
  1991年   54篇
  1990年   42篇
  1989年   33篇
  1988年   31篇
  1987年   14篇
  1986年   11篇
  1985年   12篇
  1984年   5篇
  1983年   6篇
  1982年   6篇
  1981年   2篇
  1980年   5篇
  1979年   1篇
  1951年   1篇
排序方式: 共有8089条查询结果,搜索用时 10 毫秒
51.
A new design of the CMOS full adder   总被引:2,自引:0,他引:2  
By using the transmission function theory, two CMOS full adders are designed, both of which have simpler circuits than the conventional full adder. Computer simulations with SPICE2G5 show that they can realize the expected logic functions and they have desirable transfer characteristics  相似文献   
52.
This paper presents a channel sharing scheme, Neighbor Cell Channel Sharing (NCCS) , based on region partitioning of cell coverage for wireless cellular networks. Each cell is divided into an inner-cell region and an outer-cell region. Cochannel interference is suppressed by limiting the usage of sharing channels in the inner-cell region. The channel sharing scheme achieves a traffic-adaptive channel assignment and does not require any channel locking. Performance analysis shows that using the NCCS scheme leads to a lower call blocking probability and a better channel utilization as compared with other previously proposed channel assignment schemes.  相似文献   
53.
In this paper, a new adaptive H filtering algorithm is developed to recursively update the tap-coefficient vector of a decision feedback equalizer (DFE) in order to adaptively equalize the time-variant dispersive fading channel of a high-rate indoor wireless personal communication system. Different from conventional L 2 (such as the recursive least squares (RLS)) filtering algorithms which minimize the squared equalization error, the adaptive H filtering algorithm is a worst case optimization. It minimizes the effect of the worst disturbances (including input noise and modeling error) on the equalization error. Hence, the DFE with the adaptive H filtering algorithm is more robust to the disturbances than that with the RLS algorithm. Computer simulation demonstrates that better transmission performance can be achieved using the adaptive H algorithm when the received signal-to-noise ratio (SNR) is larger than 20 dB  相似文献   
54.
针对频率编码脉冲雷达(Frequency-Coded Pulse Radar, FCPR),该文提出一种基于压缩感知(Compressive Sensing, CS)的目标高分辨距离成像方法。利用目标场景的空间稀疏性,建立FCPR目标回波稀疏信号模型,提出基于CS的FCPR脉冲相参合成处理方法。该方法采用少量FCPR信号子脉冲对目标频域响应进行采样,即可提取目标高分辨距离像信息。为了降低CS重构算法的运算复杂度,提出一种基于FFT目标速度预估计的动态构造降维感知矩阵的方法,提高了采用CS进行FCPR脉冲相参合成处理的速度。仿真结果表明该方法较传统IFFT脉冲相干合成算法具有更小的目标强散射中心幅度估计误差,对速度估计误差及噪声的鲁棒性更好。  相似文献   
55.
56.
用红外光谱技术研究打蜡梨的红外光谱特性   总被引:1,自引:0,他引:1  
袁鹏  崔蔓  庄一迪  蒙振章  陈建军 《红外》2014,35(1):42-44
采用CCD阵列光谱仪研究了打蜡梨的红外光谱特性。经分析,在655~660 nm波段,经过打蜡处理后的梨会出现吸收峰,而未经打蜡处理的梨则没有出现吸收峰;在610~620 nm波段,打过石蜡梨的红外图谱吸收峰峰高和未打蜡梨的红外图谱吸收峰峰高相当,而打过果蜡梨的红外图谱吸收峰远远低于未打蜡梨的红外图谱吸收峰。该结果表明红外光谱技术在打蜡梨检测中具有一定的可行性,同时也为进一步研究针对打蜡梨的智能化无损检测技术提供了参考依据。  相似文献   
57.
For future wireless communication systems, Power Domain Non-Orthogonal Multiple Access (PD-NOMA) using an advanced receiver has been considered as a promising radio access technology candidate. Power allocation plays an important role in the PD-NOMA system because it considerably affects the total throughput and Geometric Mean User Throughput (GMUT) performance. However, most existing studies have not completely accounted for the computational complexity of the power allocation process when the User Terminals (UTs) move in a slow fading channel environment. To resolve such problems, a power allocation method is proposed to considerably reduce the search space of a Full Search Power (FSP) allocation algorithm. The initial power reallocation coefficients will be set to start with former optimal values by the proposed Lemma before searching for optimal power reallocation coefficients based on total throughput performance. Step size and correction granularity will be adjusted within a much narrower power search range while invalid power combinations may be reasonably discarded during the search process. The simulation results show that the proposed power reallocation scheme can greatly reduce computational complexity while the total throughput and GMUT performance loss are not greater than 1.5% compared with the FSP algorithm.  相似文献   
58.
A novel positively K+‐responsive membrane with functional gates driven by host‐guest molecular recognition is prepared by grafting poly(N‐isopropylacrylamide‐co‐acryloylamidobenzo‐15‐crown‐5) (poly(NIPAM‐co‐AAB15C5)) copolymer chains in the pores of porous nylon‐6 membranes with a two‐step method combining plasma‐induced pore‐filling grafting polymerization and chemical modification. Due to the cooperative interaction of host‐guest complexation and phase transition of the poly(NIPAM‐co‐AAB15C5), the grafted gates in the membrane pores could spontaneously switch from “closed” state to “open” state by recognizing K+ ions in the environment and vice versa; while other ions (e.g., Na+, Ca2+ or Mg2+) can not trigger such an ion‐responsive switching function. The positively K+‐responsive gating action of the membrane is rapid, reversible, and reproducible. The proposed K+‐responsive gating membrane provide a new mode of behavior for ion‐recognizable “smart” or “intelligent” membrane actuators, which is highly attractive for controlled release, chemical/biomedical separations, tissue engineering, sensors, etc.  相似文献   
59.
激光诱导沙田柚无核化的研究   总被引:2,自引:0,他引:2  
报道了1988年以来激光诱变导致沙田柚无核化的研究。果实种子数已由平均140粒左右变为完全无核。开花期套袋也已得到无核果实表明,柚树已可单性结实。过氧化物因同工酶和酯酶同工酶分析也证实,其遗传性状确已发生改变。  相似文献   
60.
以激光在粗糙物体表面的散射理论为基础.详细讨论了被测表面倾斜与激光三角位移计接收光功率的关系,在此基础上提出了在测位移的同时测量该倾斜角的方法.给出了计算机模拟及实测的结果。  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