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   8731篇
  免费   474篇
  国内免费   11篇
电工技术   118篇
综合类   38篇
化学工业   2251篇
金属工艺   226篇
机械仪表   184篇
建筑科学   601篇
矿业工程   20篇
能源动力   281篇
轻工业   838篇
水利工程   87篇
石油天然气   43篇
武器工业   1篇
无线电   658篇
一般工业技术   1448篇
冶金工业   548篇
原子能技术   58篇
自动化技术   1816篇
  2023年   85篇
  2022年   202篇
  2021年   333篇
  2020年   184篇
  2019年   200篇
  2018年   270篇
  2017年   233篇
  2016年   314篇
  2015年   233篇
  2014年   337篇
  2013年   624篇
  2012年   482篇
  2011年   614篇
  2010年   426篇
  2009年   492篇
  2008年   453篇
  2007年   410篇
  2006年   341篇
  2005年   291篇
  2004年   269篇
  2003年   258篇
  2002年   189篇
  2001年   137篇
  2000年   137篇
  1999年   114篇
  1998年   128篇
  1997年   128篇
  1996年   96篇
  1995年   79篇
  1994年   79篇
  1993年   83篇
  1992年   58篇
  1991年   60篇
  1990年   61篇
  1989年   68篇
  1988年   49篇
  1987年   47篇
  1986年   50篇
  1985年   53篇
  1984年   62篇
  1983年   44篇
  1982年   38篇
  1981年   37篇
  1980年   39篇
  1979年   32篇
  1978年   34篇
  1977年   33篇
  1976年   39篇
  1975年   40篇
  1973年   36篇
排序方式: 共有9216条查询结果,搜索用时 15 毫秒
231.
Digital Library support for textual and certain types of non-textual documents has significantly advanced over the last years. While Digital Library support implies many aspects along the whole library workflow model, interactive and visual retrieval allowing effective query formulation and result presentation are important functions. Recently, new kinds of non-textual documents which merit Digital Library support, but yet cannot be fully accommodated by existing Digital Library technology, have come into focus. Scientific data, as produced for example, by scientific experimentation, simulation or observation, is such a document type. In this article we report on a concept and first implementation of Digital Library functionality for supporting visual retrieval and exploration in a specific important class of scientific primary data, namely, time-oriented research data. The approach is developed in an interdisciplinary effort by experts from the library, natural sciences, and visual analytics communities. In addition to presenting the concept and to discussing relevant challenges, we present results from a first implementation of our approach as applied on a real-world scientific primary data set. We also report from initial user feedback obtained during discussions with domain experts from the earth observation sciences, indicating the usefulness of our approach.  相似文献   
232.
Business process models are becoming available in large numbers due to their widespread use in many industrial applications such as enterprise and quality engineering projects. On the one hand, this raises a challenge as to their proper management: how can it be ensured that the proper process model is always available to the interested stakeholder? On the other hand, the richness of a large set of process models also offers opportunities, for example with respect to the re-use of existing model parts for new models. This paper describes the functionality and architecture of an advanced process model repository, named APROMORE. This tool brings together a rich set of features for the analysis, management and usage of large sets of process models, drawing from state-of-the art research in the field of process modeling. A prototype of the platform is presented in this paper, demonstrating its feasibility, as well as an outlook on the further development of APROMORE.  相似文献   
233.
Model predictive control of a rotary cement kiln   总被引:2,自引:0,他引:2  
A first principles model of a cement kiln is used to control and optimize the burning of clinker in the cement production process. The model considers heat transfer between a gas and a feed state via convection and radiation. Furthermore, it contains effects such as chemical reactions, feed transport, energy losses and energy input. A model predictive controller is used to stabilize a temperature profile along the rotary kiln, guarantee good combustion conditions and maximize production. Moving horizon estimation was used for online estimation of selected model parameters and unmeasured states. Results from the pilot site are presented.  相似文献   
234.
Jan Kapa?a 《Calphad》2011,35(2):219-223
The thermodynamic properties of ABr-PrBr3(A=Li-Cs) systems were assessed by the CALPHAD method. The liquid phase in the systems was described by the non-stoichiometric associate model. The entropies of mixing in the liquid were evaluated from experimental liquidus and enthalpy of mixing data. For the pseudobinary compounds A3PrBr6,APr2Br7, and A2PrBr5 (A=K,Rb) and Cs3PrBr6 and CsPr2Br7, the dependences of Gibbs energies of formation on temperature were calculated. The anomalies of sequences of thermodynamic properties in RbBr-PrBr3 were observed and discussed. The nature of the liquid phase and precision of calculations of the Rb2PrBr5(s) compound were discussed.  相似文献   
235.
This study examined the influence of perceived enjoyment on pre-service teachers’ intention to use technology, in addition to re-appraising the role of attitude toward use in the Technology Acceptance Model (TAM; Davis, Bagozzi, &; Warshaw, 1989). One hundred and fifty-three participants in Singapore completed a survey questionnaire measuring their responses to five constructs from a research model that was developed specifically for the study. Structural Equation Modeling (SEM) showed that perceived enjoyment was a significant predictor of perceived usefulness, perceived ease of use, and intention to use technology. The findings of this study support the view of Davis et al. (1989) from over 30 years ago that attitude toward use contributes only modestly to the TAM.  相似文献   
236.
A configurable process model provides a consolidated view of a family of business processes. It promotes the reuse of proven practices by providing analysts with a generic modeling artifact from which to derive individual process models. Unfortunately, the scope of existing notations for configurable process modeling is restricted, thus hindering their applicability. Specifically, these notations focus on capturing tasks and control-flow dependencies, neglecting equally important ingredients of business processes such as data and resources. This research fills this gap by proposing a configurable process modeling notation incorporating features for capturing resources, data and physical objects involved in the performance of tasks. The proposal has been implemented in a toolset that assists analysts during the configuration phase and guarantees the correctness of the resulting process models. The approach has been validated by means of a case study from the film industry.  相似文献   
237.
This work describes a novel method of detecting Escherichia coli using photoluminescence (PL) emission from III–V quantum semiconductor (QS) devices functionalized with two different antibody-based architectures. The first approach employed self-assembled monolayers of biotinylated polyethylene glycol thiols to immobilize biotinylated antibody via neutravidin. In the second approach, we used QS microstructures coated with a thin layer of Si3N4 allowing direct functionalization with E. coli antibodies through hydrofluoric acid etching and glutaraldehyde-based reticulation. Atomic force, optical and fluorescence microscopy measurements were used to assess the immobilization process. Depending on the biosensing architecture, density of the immobilized bacteria was observed in the range of 0.5–0.7 bacteria/100 μm2. The detection of E. coli at 104 CFU/ml was achieved within less than 120 min of the bacteria exposure. It is expected that an even better sensitivity threshold could be achieved following further optimization of the method.  相似文献   
238.
The paper deals with the problem of motion planning of anthropomorphic mechanical hands avoiding collisions and trying to mimic real human hand postures. The approach uses the concept of “principal motion directions” to reduce the dimension of the search space in order to obtain results with a compromise between motion optimality and planning complexity (time). Basically, the work includes the following phases: capturing the human hand workspace using a sensorized glove and mapping it to the mechanical hand workspace, reducing the space dimension by looking for the most relevant principal motion directions, and planning the hand movements using a probabilistic roadmap planner. The approach has been implemented for a four finger anthropomorphic mechanical hand (17 joints with 13 independent degrees of freedom) assembled on an industrial robot (6 independent degrees of freedom), and experimental examples are included to illustrate its validity.  相似文献   
239.
In recent years, manufacturing companies and service providers have moved towards offering customer-specific problem solutions. These integrated bundles usually consist of hardware, software, and service components and are called product service systems (PSS) or hybrid products. Since the success of the resulting solution depends on the understanding of all requirements, requirements engineering (RE) has become a key factor. The article analyzes the state of the art of RE for PSS based on an extensive literature review in the domains of product-, software-, and service engineering. For this, criteria are derived from the characteristics of PSS and from the task area of RE in the life cycle of PSS. Based on these criteria we analyze the most established RE approaches for their suitability for PSS. An important finding is that integrated/interdisciplinary approaches for RE are missing. Moreover, the maturity of RE approaches in the three domains varies significantly. All analyzed approaches heavily rely on concepts and solution characteristics of their own domain so that a transfer to other domains is hardly possible. This literature review lays the foundation for successful RE for PSS and especially for future research aiming at combining and integrating RE approaches and models of product-, software-, and service engineering. Such requirement models could connect concepts of single domains and enable an integrated and seamless RE for PSS.  相似文献   
240.
Solutions of a boundary value problem for the Korteweg–de Vries equation are approximated numerically using a finite-difference method, and a collocation method based on Chebyshev polynomials. The performance of the two methods is compared using exact solutions that are exponentially small at the boundaries. The Chebyshev method is found to be more efficient.  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