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   51349篇
  免费   2631篇
  国内免费   162篇
电工技术   625篇
综合类   274篇
化学工业   10230篇
金属工艺   1201篇
机械仪表   1052篇
建筑科学   1515篇
矿业工程   186篇
能源动力   1310篇
轻工业   8296篇
水利工程   402篇
石油天然气   265篇
武器工业   12篇
无线电   2503篇
一般工业技术   8374篇
冶金工业   11069篇
原子能技术   316篇
自动化技术   6512篇
  2023年   450篇
  2022年   705篇
  2021年   1325篇
  2020年   927篇
  2019年   962篇
  2018年   1494篇
  2017年   1406篇
  2016年   1553篇
  2015年   1372篇
  2014年   1731篇
  2013年   3209篇
  2012年   2554篇
  2011年   2903篇
  2010年   2282篇
  2009年   2261篇
  2008年   2258篇
  2007年   2068篇
  2006年   1588篇
  2005年   1360篇
  2004年   1127篇
  2003年   1036篇
  2002年   937篇
  2001年   704篇
  2000年   666篇
  1999年   834篇
  1998年   3633篇
  1997年   2239篇
  1996年   1598篇
  1995年   932篇
  1994年   783篇
  1993年   731篇
  1992年   283篇
  1991年   286篇
  1990年   231篇
  1989年   264篇
  1988年   230篇
  1987年   235篇
  1986年   202篇
  1985年   316篇
  1984年   244篇
  1983年   214篇
  1982年   174篇
  1981年   224篇
  1980年   224篇
  1979年   149篇
  1978年   129篇
  1977年   307篇
  1976年   655篇
  1975年   113篇
  1973年   141篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This paper deals with fault detection and identification in dynamic systems when the system dynamics can be modeled by smooth nonlinear differential equations including affine, bilinear or linear parameter varying (LPV) systems. Two basic approaches will be considered, these apply differential algebraic and differential geometric tools.In the differential algebraic approach the state elimination methods will be used to derive nonlinear parity relations. In the specific case when a reconstruction of the fault signal is needed the dynamic inversion based approach will be investigated. This approach will also be studied from geometric point of view. The geometric approach, as proposed by Isidori and De Persis, is suitable to extend the detection filter and unknown input observer design approaches (well elaborated for LTI systems) to affine nonlinear systems.Beyond the development of the theory of fault detection and identification it is equally important to offer computable methods and to analyze the robustness properties against uncertainties. Both the observer based and the inversion based approaches will be elaborated for LPV systems that may offer computational tools inherited from linear systems and also allow to design for robustness utilizing results from robust filtering and disturbance attenuation.  相似文献   
992.
Medical data mining is currently actively pursued in computer science and statistical research but not in medical practice. The reasons therefore lie in the difficulties of handling and statistically analyzing medical data. We have developed a system that allows practitioners in the field to interactively analyze their data without assistance of statisticians or data mining experts. In the course of this paper we will introduce data mining of medical data and show how this can be achieved for survival data. We will demonstrate how to solve common problems of interactive survival analysis by presenting the Online Clinical Data Mining (OCDM) system. Thereby the main focus is on similarity based queries, a new method to select similar cases based on their covariables and the influence of these on their survival.  相似文献   
993.
The present paper deals with a generalization of the homogeneous multi-server finite-source retrial queue with search for customers in the orbit. The novelty of the investigation is the introduction of balking and impatience for requests who arrive at the service facility with a limited capacity and FIFO queue. Arriving customers may balk, i.e., they either join the queue or go to the orbit. Moreover, the requests are impatient and abandon the buffer after a random time and enter the orbit, too. In case of an empty buffer, each server searches for a customer in the orbit after finishing service. All random variables involved in the model construction are supposed to be exponentially distributed and independent of each other. The primary aim of this analysis is to show the effect of balking, impatience, and buffer size on the steady-state performance measures. Concentrating on the mean response time, several numerical examples are investigated by the help of the MOSEL-2 tool used for creating the model and calculating the stationary characteristics.  相似文献   
994.
We propose a new fluid control technique that uses scale-dependent force control to preserve small-scale fluid detail. Control particles define local force fields and can be generated automatically from either a physical simulation or a sequence of target shapes. We use a multi-scale decomposition of the velocity field and apply control forces only to the coarse-scale components of the flow. Small-scale detail is thus preserved in a natural way avoiding the artificial viscosity often introduced by force-based control methods. We demonstrate the effectiveness of our method for both Lagrangian and Eulerian fluid simulation environments.  相似文献   
995.
When evaluating transportation infrastructure projects and determining which of them will be carried out from a set of projects and given a budget constraint, several criteria need to be considered in the decision. Standard evaluation practices imply the aggregation of impacts into one utility function which is later optimized. Nevertheless these techniques used for translation of different measuring units into monetary terms are highly controversial. Multicriteria techniques can explicitly deal with different measuring units, however, they are not suitable to model interdependence relationships of projects that share a common characteristic (same route, location or target population, for instance). In this research we model this transportation planning problem, the multi-objective transportation infrastructure project selection problem (MTIPSP), as a constrained multi-objective optimization problem with quadratic objective functions, using a variation of the multi-objective 0–1 knapsack problem plus some additional constraints. Given the combinatorial nature of the problem, an evolutionary-based framework is used for the identification of Pareto solutions, and later, those with non-attractive properties are filtered using a Knee Identification Procedure. The final selection of the projects portfolio is made using a well known multicriteria decision aid method and including the decision makers’ preferences based on the existing context.  相似文献   
996.
997.
In many Grid infrastructures different kinds of information services are in use, which utilize different incompatible data structures and interfaces to encode and provide their data. Homogeneous monitoring of these infrastructures with the monitoring data being accessible everywhere independently of the middleware which provided it, is the basis for a consistent status reporting on the Grids’ resources and services. Thus, interoperability or interoperation between the different information services in a heterogeneous Grid infrastructure is required. Monitoring data must contain the identity of the affected Virtual Organization (VO) so that it can be related to the resources and services the VO has allocated to enable VO-specific information provision. This paper describes a distributed architecture for an interoperable information service, which combines data unification and categorization with policies for VO membership, VO resource management and data transformations. This service builds the basis for an integrated and interoperating monitoring of Grids, which provide their data to more than one VO and utilize heterogeneous information services.  相似文献   
998.
This work proposes a mathematical model for the acclimatization process of a bioreactor treating toxic wastewater. Experimental data was used to identify the changing kinetic parameters of the model as acclimatization progresses. It was found that only one key parameter, the specific biomass growth rate function, changed during the acclimatization process. Therefore, an acclimatization model was proposed to explain the changes of this parameter.  相似文献   
999.
Zusammenfassung  Die Autoren untersuchen das datenschutzrechtliche Vollzugsdefizit im Anwendungsbereich des Telemediengesetzes. Ihr Ergebnis ist, dass das Ausma? des datenschutzrechtlichen Vollzugsdefizits der von au?en zu überprüfenden datenschutzrechtlichen Pflichten der Anbieter „erschreckend“ ist. Nur einem ganz geringen Teil der Anbieter gelingt es, sich rechtskonform zu verhalten. Prof. Dr. Jürgen Kühling Inhaber eines Lehrstuhls für ?ffentliches Recht an der Universit?t Regensburg. Anastasios Sivridis wissenschaftlicher Mitarbeiter und Doktorand am Lehrstuhl Prof. Kühling. Mathis Schwuchow studentische Hilfskraft am Lehrstuhl Prof. Kühling. Thorben Burghardt wissenschaftlicher Mitarbeiter und Doktorand am Lehrstuhl für Systeme der Informationsverwaltung (TH Karlsruhe).  相似文献   
1000.
This article presents a metamodeling study for Live Sequence Charts (LSCs) and Message Sequence Charts (MSCs) with an emphasis on code generation. The article discusses specifically the following points: the approach to building a metamodel for MSCs and LSCs, a metamodel extension from MSC to LSC, support for model-based code generation, and finally action model and domain-specific data model integration. The metamodel is formulated in metaGME, the metamodel language for the Generic Modeling Environment.
Halit OğuztüzünEmail:
  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