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   4019篇
  免费   64篇
  国内免费   10篇
电工技术   38篇
综合类   3篇
化学工业   383篇
金属工艺   46篇
机械仪表   51篇
建筑科学   36篇
矿业工程   3篇
能源动力   94篇
轻工业   90篇
水利工程   5篇
石油天然气   17篇
无线电   335篇
一般工业技术   450篇
冶金工业   2305篇
原子能技术   20篇
自动化技术   217篇
  2023年   17篇
  2022年   35篇
  2021年   53篇
  2020年   44篇
  2019年   40篇
  2018年   66篇
  2017年   57篇
  2016年   52篇
  2015年   32篇
  2014年   69篇
  2013年   139篇
  2012年   92篇
  2011年   90篇
  2010年   63篇
  2009年   75篇
  2008年   71篇
  2007年   83篇
  2006年   61篇
  2005年   41篇
  2004年   48篇
  2003年   48篇
  2002年   51篇
  2001年   32篇
  2000年   30篇
  1999年   93篇
  1998年   696篇
  1997年   462篇
  1996年   297篇
  1995年   192篇
  1994年   149篇
  1993年   153篇
  1992年   44篇
  1991年   47篇
  1990年   40篇
  1989年   35篇
  1988年   54篇
  1987年   30篇
  1986年   29篇
  1985年   23篇
  1984年   14篇
  1983年   17篇
  1982年   21篇
  1981年   27篇
  1980年   20篇
  1979年   16篇
  1978年   18篇
  1977年   53篇
  1976年   135篇
  1975年   8篇
  1973年   11篇
排序方式: 共有4093条查询结果,搜索用时 15 毫秒
101.
Quantum cheques could be a forgery-free way to make transaction in a quantum networked banking system with perfect security against any no-signalling adversary. Here, we demonstrate the implementation of quantum cheque, proposed by Moulick and Panigrahi (Quantum Inf Process 15:2475–2486, 2016), using the five-qubit IBM quantum computer. Appropriate single qubit, CNOT and Fredkin gates are used in an optimized configuration. The accuracy of implementation is checked and verified through quantum state tomography by comparing results from the theoretical and experimental density matrices.  相似文献   
102.
103.
Thermoluminescence behaviour of a series of binary alkali borate glasses has been investigated to study their energy storage mechanism. Sodium borate glasses of varying composition have been prepared and their glow curves recorded after exposing them to X-rays (CuK radiation, 30 kV, 10 mA) of different dosages at room temperature. The effect of the nature and concentration of alkali oxide and the dose of irradiation on the nature of thermoluminescent glow curves were also studied. Borate glasses containing different concentrations of Na2O exhibit significantly different glow curves. These glow curves have been analysed and the nature of traps responsible for TL emission are tentatively identified. The broad and complex nature of the glow pattern is attributed to distribution of trap depths in these materials. The viability of borate glasses in the construction of TL dosimeters are discussed.  相似文献   
104.
With the rapid growth of the availability and popularity of interpersonal and behavior-rich resources such as blogs and other social media avenues, emerging opportunities and challenges arise as people now can, and do, actively use computational intelligence to seek out and understand the opinions of others. The study of collective behavior of individuals has implications to business intelligence, predictive analytics, customer relationship management, and examining online collective action as manifested by various flash mobs, the Arab Spring (2011) and other such events. In this article, we introduce a nature-inspired theory to model collective behavior from the observed data on blogs using swarm intelligence, where the goal is to accurately model and predict the future behavior of a large population after observing their interactions during a training phase. Specifically, an ant colony optimization model is trained with behavioral trend from the blog data and is tested over real-world blogs. Promising results were obtained in trend prediction using ant colony based pheromone classier and CHI statistical measure. We provide empirical guidelines for selecting suitable parameters for the model, conclude with interesting observations, and envision future research directions.  相似文献   
105.
In the design and analysis of any queueing system, one of the main objectives is to reduce congestion which can be achieved by controlling either arrival-rates or service-rates. This paper adopts the latter approach and analyzes a single-server finite-buffer queue where customers arrive according to the Poisson process and are served in batches of minimum size a with a maximum threshold limit b. The service times of the batches are arbitrarily distributed and depends on the size of the batches undergoing service. We obtain the joint distribution of the number of customers in the queue and the number with the server, and distributions of the number of customers in the queue, in the system, and the number with the server. Various performance measures such as the average number of customers in the queue (system) and with the server etc. are obtained. Several numerical results are presented in the form of tables and graphs and it is observed that batch-size-dependent service rule is more effective in reducing the congestion as compared to the one when service rates of the batches remain same irrespective of the size of the batch. This model has potential application in manufacturing, computer-communication network, telecommunication systems and group testing.  相似文献   
106.
Economic pressures and "value" judgments both compel and contaminate the current debate on the efficacy of psychotherapy. Too often, complex clinical trial outcome studies ignore the clinical or treatment process, as well as personality or contextual variables. Thus, they fail to build the foundations of a clinical science that makes possible the development of individually tailored treatment approaches and outcome predictions for specific patients with unique personalities, symptoms, and life circumstances. The real challenge, therefore, is for each psychotherapeutic approach to delineate its "process steps" and relate these steps to different outcomes. The "process" is the "final common pathway" for a number of patient, therapist, technique, and contextual variables. The capacity to predict the relationship between process and outcome at each stage in a therapeutic procedure is the relevant clinical test of "efficacy."  相似文献   
107.
beta-Ionone is found to stimulate considerably carotinoids synthesis in Blakeslea trispora. The stabilization of carotene-synthesizing ability of B. trispora in the presence of beta-ionine under prolonged incubation time is observed. Stabilization of polyribosomes in the presence of beta-ionine is observed when studying polyribosome content in B. trispora. A hypothesis is expressed on the existence of biochemical "receptors" as a linkage between synthesized protein and destroying mRNA.  相似文献   
108.
Synthesis conditions of La2Mo2O9 thin film by radio frequency (RF) sputtering technique on Al2O3 ceramic substrates are studied. It is found that the deposition temperature and oxygen partial pressure are the most important factors for obtaining pure La2Mo2O9 films. Varying both parameters, Mo-rich, stoichiometric, and Mo-deficient films are obtained. With increasing the La:Mo ratio, films become denser. A crust layer is observed on top of the Mo-rich and the Mo-deficient films. The formation of the La2Mo2O9 phase is discussed with respect to the sputtering mechanism.  相似文献   
109.
We have studied the minimum off-state leakage current of ultrascaled Schottky-barrier carbon nanotube transistors (SBCNTs) with midgap Schottky-barrier source/drain contacts. The off-state leakage current is separated into two parts: thermal emission around the top of the Schottky barrier and tunneling through the evanescent band-gap states. Because the transmission through deep band-gap states makes a dominant contribution for ultrascaled SBCNTs, the off-state minimum leakage current increases exponentially with decreasing scaling length of SBCNTs.  相似文献   
110.
PbTe thin films were deposited electrochemically on transparent conducting oxide coated (TCO) glass substrates from a solution of lead acetate and TeO2 at low pH. A lead (Pb) strip was used as a sacrificing anode and the TCO glass acted as the cathode, which were short-circuited externally. Depositions were carried out at different temperatures of the bath to study the growth kinetics and grain growth. X-ray diffraction technique, scanning electron microscopy, infrared spectroscopy and resistivity measurements were carried out to characterize the deposited films. The films were polycrystalline in nature with a cubic phase.  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