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   6734篇
  免费   243篇
  国内免费   13篇
电工技术   65篇
综合类   6篇
化学工业   1244篇
金属工艺   82篇
机械仪表   170篇
建筑科学   256篇
矿业工程   48篇
能源动力   158篇
轻工业   532篇
水利工程   94篇
石油天然气   15篇
无线电   375篇
一般工业技术   1115篇
冶金工业   1646篇
原子能技术   47篇
自动化技术   1137篇
  2023年   44篇
  2022年   29篇
  2021年   108篇
  2020年   84篇
  2019年   96篇
  2018年   141篇
  2017年   120篇
  2016年   122篇
  2015年   128篇
  2014年   184篇
  2013年   417篇
  2012年   335篇
  2011年   408篇
  2010年   290篇
  2009年   262篇
  2008年   365篇
  2007年   358篇
  2006年   309篇
  2005年   285篇
  2004年   246篇
  2003年   210篇
  2002年   219篇
  2001年   137篇
  2000年   108篇
  1999年   136篇
  1998年   119篇
  1997年   125篇
  1996年   119篇
  1995年   105篇
  1994年   116篇
  1993年   92篇
  1992年   111篇
  1991年   54篇
  1990年   101篇
  1989年   77篇
  1988年   71篇
  1987年   89篇
  1986年   58篇
  1985年   72篇
  1984年   60篇
  1983年   67篇
  1982年   59篇
  1981年   47篇
  1980年   45篇
  1979年   45篇
  1978年   37篇
  1977年   43篇
  1976年   28篇
  1975年   33篇
  1973年   19篇
排序方式: 共有6990条查询结果,搜索用时 15 毫秒
11.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
12.
Filtering algorithms are well accepted as a means of speeding up the solution of the consistent labeling problem (CLP). Despite the fact that path consistency does a better job of filtering than arc consistency, AC is still the preferred technique because it has a much lower time complexity. We are implementing parallel path consistency algorithms on multiprocessors and comparing their performance to the best sequential and parallel arc consistency algorithms.(1,2) (See also work by Kerethoet al. (3) and Kasif(4)) Preliminary work has shown linear performance increases for parallelized path consistency and also shown that in many cases performance is significantly better than the theoretical worst case. These two results lead us to believe that parallel path consistency may be a superior filtering technique. Finally, we have implemented path consistency as an outer product computation and have obtained good results (e.g., linear speedup on a 64K-node Connection Machine 2).  相似文献   
13.
14.
Perhaps the most powerful claim that advocates of fiber can make,on top of the massive bandwidthfiber makes possible today, is that fiber is future-proof. That is, the fiber that is laid today can be upgraded so that the same strands of glass can carry massively more bandwidth in the future.  相似文献   
15.
Real-world tasks are often complex, uncertain, and constrained. The complexity arises from the need to consider numerous factors that are of varying degrees of relevance to the problem at hand. The uncertainty springs from imperfect information concerning the state of the world, the repertoire of feasible alternatives, and the consequences of each action. The constraints are attributable to time, money, and computational resources as well as individual tastes and societal values.Despite the rich nature of practical tasks, previous work in decision making—whether in engineering, statistics, management, or economics—has focused solely on partial aspects of the problem. This state of affairs is reflected in the nomenclature, which involves categories such as “constrained optimization” or “decisions under uncertainty”.If real-world tasks are to be addressed in a coherent fashion, it is imperative to develop a systematic framework providing an integrated view. The framework may then serve as the foundation for a general theory of decision making that can capture the full richness of realistic problems. This paper explores how these goals might be achieved.Algebraic and stochastic models of innovative decision making are presented. This is followed by an examination of idea generation in product design. Finally, suggestions are made for extending the work along both theoretical and empirical lines.  相似文献   
16.
Blood product transfusion is a financial concern for hospitals and patients. Efficient utilization of this dwindling resource is a critical problem if hospitals are to maximize patient care while minimizing costs. Traditional statistical models do not perform well in this domain. An additional concern is the speed with which transfusion decisions and planning can be made. Rapid assessment in the emergency room (ER) necessarily limits the amount of usable information available (with respect to independent variables available). This study evaluates the efficacy of using artificial neural networks (ANNs) to predict the transfusion requirements of trauma patients using readily available information. A total of 1016 patient records are used to train and test a backpropagation neural network for predicting the transfusion requirements of these patients during the first 2, 2-6, and 6-24 h, and for total transfusions. Sensitivity and specificity analysis are used along with the mean absolute difference between blood units predicted and units transfused to demonstrate that ANNs can accurately predict most ER patient transfusion requirements, while only using information available at the time of entry into the ER.  相似文献   
17.
Although continuing care is strongly related to positive treatment outcomes for substance use disorder (SUD), participation rates are low and few effective interventions are available. In a randomized clinical trial with 150 participants (97% men), 75 graduates of a residential Veterans Affairs Medical Center SUD program who received an aftercare contract, attendance prompts, and reinforcers (CPR) were compared to 75 graduates who received standard treatment (STX). Among CPR participants, 55% completed at least 3 months of aftercare, compared to 36% in STX. Similarly, CPR participants remained in treatment longer than those in STX (5.5 vs. 4.4 months). Additionally, CPR participants were more likely to be abstinent compared to STX (57% vs. 37%) after 1 year. The CPR intervention offers a practical means to improve adherence among individuals in SUD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
18.
This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
19.
Copper containing faujasite has been successfully prepared for the first time using a direct synthesis method. Faujasite type zeolite can be prepared in the presence of copper species by tuning the synthesis conditions. Ammonium hydroxide was used to form a copper complex that was later mixed with the reacting gel. Sodium is required to obtain copper faujasite. The complete elimination of sodium ions from the starting gel produces amorphous material. Crystallization took place at 358 K for 11 days. Crystallization temperature of 373 K produces ANA type zeolite as an impurity. Increasing by two times the amount of copper complex added to the reacting gel increases the crystallization time of Cu-FAU from 11 to 20 days (the crystallization rate decreases). The copper containing faujasite obtained was characterized by XRD, FESEM, EDX, EPR, FT-IR, TPR, and BET. According to the XRD pattern only FAU type zeolite was obtained. According to TPR experiments, the reduction temperature for Cu2+ ions present in Cu-FAU prepared by direct synthesis was 70 K more than for Cu-FAU prepared by ion-exchange. This difference can be due to the different location of the copper ions in the supercages or in the sodalite cages of the faujasite.  相似文献   
20.
Introduction     
Concluding remarks With this brief exposition of the areas covered in this special double issue on Eurotra, we shall now conclude our introduction. We hope that the volume will achieve its goals, as outlined above, at least to some extent. Certainly, much more could be said about a wide range of topics which have been covered in the lifetime or the project so far. For instance, these article, mainly written by linguists, deliberately neglect the software implementation and environment aspects of the prototype Eurotra Translation System, as well as a number of peripheral tools and components of the system that are available to the user, such as lexical data bases, text-handling mechanisms and the like. The reader interested in aspects of this kind is referred to Raw et al. 1989 for a very brief introduction, and to the Eurotra software team at the Commission of the European Communities (DG XIII, Luxembourg) for more details. However, one goal that we do hope to come close to achieving is to give a fair overview of the Eurotra linguistic theory of translation and the mainstream and sideline formalisms expressing variant versions of it. If we have come anywhere near achieving that, our gratitude is due to the numerous Eurotra colleagues who have supported us in preparing this volume, and to the editor of this journal.  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