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   8199篇
  免费   590篇
  国内免费   16篇
电工技术   175篇
综合类   30篇
化学工业   1929篇
金属工艺   216篇
机械仪表   221篇
建筑科学   321篇
矿业工程   38篇
能源动力   285篇
轻工业   1241篇
水利工程   63篇
石油天然气   59篇
武器工业   1篇
无线电   614篇
一般工业技术   1799篇
冶金工业   253篇
原子能技术   80篇
自动化技术   1480篇
  2024年   33篇
  2023年   87篇
  2022年   103篇
  2021年   240篇
  2020年   244篇
  2019年   207篇
  2018年   395篇
  2017年   413篇
  2016年   454篇
  2015年   291篇
  2014年   412篇
  2013年   837篇
  2012年   523篇
  2011年   655篇
  2010年   463篇
  2009年   452篇
  2008年   372篇
  2007年   367篇
  2006年   238篇
  2005年   258篇
  2004年   190篇
  2003年   172篇
  2002年   209篇
  2001年   108篇
  2000年   88篇
  1999年   70篇
  1998年   99篇
  1997年   87篇
  1996年   71篇
  1995年   55篇
  1994年   47篇
  1993年   38篇
  1992年   29篇
  1991年   32篇
  1990年   22篇
  1989年   26篇
  1988年   21篇
  1986年   17篇
  1985年   35篇
  1984年   31篇
  1983年   21篇
  1982年   24篇
  1981年   25篇
  1980年   22篇
  1979年   28篇
  1978年   23篇
  1977年   18篇
  1976年   20篇
  1974年   18篇
  1973年   19篇
排序方式: 共有8805条查询结果,搜索用时 15 毫秒
81.
Dataflow programs are widely used. Each program is a directed graph where nodes are computations and edges indicate the flow of data. In prior work, we reverse-engineered legacy dataflow programs by deriving their optimized implementations from a simple specification graph using graph transformations called refinements and optimizations. In MDE speak, our derivations were PIM-to-PSM mappings. In this paper, we show how extensions complement refinements, optimizations, and PIM-to-PSM derivations to make the process of reverse engineering complex legacy dataflow programs tractable. We explain how optional functionality in transformations can be encoded, thereby enabling us to encode product lines of transformations as well as product lines of dataflow programs. We describe the implementation of extensions in the \(\mathtt{ReFlO}\) tool and present two non-trivial case studies as evidence of our work’s generality.  相似文献   
82.
Both academic and corporate interest in sustainable supply chains has increased in recent years. Supplier selection process is one of the key operational tasks for sustainable supply chain management. This paper examines the problem of identifying an effective model based on sustainability principles for supplier selection operations in supply chains. Due to its multi-criteria nature, the sustainable supplier evaluation process requires an appropriate multi-criteria analysis and solution approach. The approach should also consider that decision makers might face situations such as time pressure, lack of expertise in related issue, etc., during the evaluation process. The paper develops a novel approach based on fuzzy analytic network process within multi-person decision-making schema under incomplete preference relations. The method not only makes sufficient evaluations using the provided preference information, but also maintains the consistency level of the evaluations. Finally, the paper analyzes the sustainability of a number of suppliers in a real-life problem to demonstrate the validity of the proposed evaluation model.  相似文献   
83.
Conformance control for ATM cells is based on a real-time reactive algorithm which delivers a value depending on inputs from the network. This value must always fit with a well defined theoretical value. We present here the correctness proof of the algorithm standardized for the ATM transfer capability called ABR. The proof turned out to produce a key argument during the standardization process of ABR.  相似文献   
84.
Classical visual servoing techniques need a strong a priori knowledge of the shape and the dimensions of the observed objects. In this paper, we present how the 2 1/2 D visual servoing scheme we have recently developed, can be used with unknown objects characterized by a set of points. Our scheme is based on the estimation of the camera displacement from two views, given by the current and desired images. Since vision-based robotics tasks generally necessitate to be performed at video rate, we focus only on linear algorithms. Classical linear methods are based on the computation of the essential matrix. In this paper, we propose a different method, based on the estimation of the homography matrix related to a virtual plane attached to the object. We show that our method provides a more stable estimation when the epipolar geometry degenerates. This is particularly important in visual servoing to obtain a stable control law, especially near the convergence of the system. Finally, experimental results confirm the improvement in the stability, robustness, and behaviour of our scheme with respect to classical methods.  相似文献   
85.
This paper proposes a non-parametric method for the classification of thin-layer chromatographic (TLC) images from patterns represented in a dissimilarity space. Each pattern corresponds to a mixture of Gaussian approximation of the intensity profile. The methodology comprises various phases, including image processing and analysis steps to extract the chromatographic profiles and a classification phase to discriminate among two groups, one corresponding to normal cases and the other to three pathological classes. We present an extensive study of several dissimilarity-based approaches analysing the influence of the dissimilarity measure and the prototype selection method on the classification performance. The main conclusions of this paper are that, Match and Profile-difference dissimilarity measures present better results, and a new prototype selection methodology achieves a performance similar or even better than conventional methods. Furthermore, we also concluded that simplest classifiers, such as k-NN and linear discriminant classifiers (LDCs), present good performance being the overall classification error less than 10% for the four-class problem.  相似文献   
86.
The development and adoption of lab-on-a-chip and micro-TAS (total analysis system) techniques requires not only the solving of design and manufacturing issues, but also the introduction of reliable and quantitative methods of analysis. In this work, two complementary tools are applied to the study of thermal and solutal transport in liquids. The experimental determination of the concentration of water in a water–methanol mixture and of the temperature of water in a microfluidic T-mixer are achieved by means of fluorescence lifetime imaging microscopy (FLIM). The results are compared to those of finite volume simulations based on tabulated properties and well-established correlations for the fluid properties. The good correlation between experimental and modelled results demonstrate without ambiguity that (1) the T-mixer is an adiabatic system within the conditions, fluids and flow rates used in this study, (2) buoyancy effects influence the mixing of liquids of different densities at moderate flow rates (Reynolds number Re ≪ 10−2), and (3) the combination of FLIM and computational fluid dynamics has the potential to be used to measure the thermal and solutal diffusion coefficients of fluids for a range of temperatures and concentrations in one single experiment. As such, it represents a first step towards the full-field monitoring of both the extent and the kinetics of a chemical reaction.
David-A. MendelsEmail:
  相似文献   
87.
The Plasmodium falciparum food vacuole (FV) is a lysosome-like organelle where erythrocyte hemoglobin digestion occurs. It is a favorite target in the development of antimalarials. We have used a tandem mass spectrometry approach to investigate the proteome of an FV-enriched fraction and identified 116 proteins. The electron microscopy analysis and the Western blot data showed that the major component of the fraction was the FV and, as expected, the majority of previously known FV markers were recovered. Of particular interest, several proteins involved in vesicle-mediated trafficking were identified, which are likely to play a key role in FV biogenesis and/or FV protein trafficking. Recovery of parasite surface proteins lends support to the cytostomal pathway of hemoglobin ingestion as a FV trafficking route. We have identified 32 proteins described as hypothetical in the databases. This insight into FV protein content provides new clues towards understanding the biological function of this organelle in P. falciparum.  相似文献   
88.
The purpose of this study was to describe the traumatology of teaching physical education (PE) and to document the causes and mechanisms of injuries in this occupation. Our sample was composed of 314 physical educators (PEs) teaching at three school levels (primary school, secondary school and college) who responded to a questionnaire survey. The results showed a 0.55 rate of recent lesion per teacher per year (0.65 for women and 0.51 for men). A total of 37.6% of subjects were affected by a lesion during the last year at work. Subjects with a higher weekly frequency of leisure physical activities or endurance activities (five times and more) were less affected by chronic lesions as well as those who frequently practiced aerobic physical activities. Prevalence of chronic injuries was higher in older teachers. Our results confirm that the rate of lesions in this group of workers is high, and that school level and respondent age may influence the rate of lesion and the characteristics of risk factors. In particular, the effect of ageing and teaching specialization on the incidence of occupational problems in PEs warrants further research. Given the relatively high rate of injuries among PE teachers, we suggest that it is necessary to further explore preventive strategies to reduce occupational risk in these workers. In particular, prophylactic physical activity outside of work may represent such a strategy since PEs more active outside their work have lower chronic injury prevalence. PEs gave long periods of standing the highest rating for movements or positions most likely to cause them occupational injuries. It can thus be suggested to find ways to reduce standing position sustained for long periods.  相似文献   
89.
Reasoning about software systems at the architectural level is key to effective software development, management, evolution and reuse. All too often, though, the lack of appropriate documentation leads to a situation where architectural design information has to be recovered directly from implemented software artifacts. This is a very demanding process, particularly when involving recovery of runtime abstractions (clients, servers, interaction protocols, etc.) that are typical to the design of distributed software systems. This paper presents an exploratory reverse engineering approach, called X-ray, to aid programmers in recovering architectural runtime information from a distributed system's existing software artifacts. X-ray comprises three domain-based static analysis techniques, namely component module classification, syntactic pattern matching, and structural reachability analysis. These complementary techniques can facilitate the task of identifying a distributed system's implemented executable components and their potential runtime interconnections. The component module classification technique automatically distinguishes source code modules according to the executables components they implement. The syntactic pattern matching technique in turn helps to recognise specific code fragments that may implement typical component interaction features. Finally, the structural reachability analysis technique aids in the association of those features to the code specific for each executable component. The paper describes and illustrates the main concepts underlying each technique, reports on their implementation as a suit of new and off-the-shelf tools, and, to give evidence of the utility of the approach, provides a detailed account of a successful application of the three techniques to help recover a static approximation of the runtime architecture for Field, a publicly-available distributed programming environment.  相似文献   
90.
The acidity constants, pK(a) values for protonation of some substituted thiazole derivatives were calculated by using AM1 and PM3 basis sets of semi-empirical methods and B3LYP/6-31G(d) basis sets of density functional theory (DFT) calculated physical and thermodynamic parameters. Correlation search among the experimental and calculated acidity constants, pK(a) values, revealed that the best correlation exist between the experimental and ab initio calculated pK(a) values with a regression of R(2)=0.98.  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