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   26382篇
  免费   668篇
  国内免费   27篇
电工技术   288篇
综合类   25篇
化学工业   4270篇
金属工艺   369篇
机械仪表   385篇
建筑科学   1488篇
矿业工程   133篇
能源动力   598篇
轻工业   6573篇
水利工程   187篇
石油天然气   196篇
武器工业   1篇
无线电   1303篇
一般工业技术   3596篇
冶金工业   4322篇
原子能技术   174篇
自动化技术   3169篇
  2022年   227篇
  2021年   330篇
  2020年   275篇
  2019年   324篇
  2018年   390篇
  2017年   363篇
  2016年   467篇
  2015年   372篇
  2014年   536篇
  2013年   1324篇
  2012年   898篇
  2011年   1143篇
  2010年   852篇
  2009年   836篇
  2008年   1059篇
  2007年   1105篇
  2006年   785篇
  2005年   805篇
  2004年   639篇
  2003年   627篇
  2002年   574篇
  2001年   361篇
  2000年   333篇
  1999年   341篇
  1998年   357篇
  1997年   340篇
  1996年   342篇
  1995年   379篇
  1994年   294篇
  1993年   348篇
  1992年   308篇
  1991年   199篇
  1990年   293篇
  1989年   348篇
  1988年   262篇
  1987年   282篇
  1986年   258篇
  1985年   325篇
  1984年   324篇
  1983年   244篇
  1982年   262篇
  1981年   267篇
  1980年   227篇
  1979年   239篇
  1978年   230篇
  1977年   243篇
  1976年   220篇
  1975年   212篇
  1974年   213篇
  1973年   209篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
281.
Several studies have pointed out the need for accurate mid-level representations of music signals for information retrieval and signal processing purposes. In this paper, we propose a new mid-level representation based on the decomposition of a signal into a small number of sound atoms or molecules bearing explicit musical instrument labels. Each atom is a sum of windowed harmonic sinusoidal partials whose relative amplitudes are specific to one instrument, and each molecule consists of several atoms from the same instrument spanning successive time windows. We design efficient algorithms to extract the most prominent atoms or molecules and investigate several applications of this representation, including polyphonic instrument recognition and music visualization.  相似文献   
282.
283.
Proteomics is a powerful tool for the identification of proteins, which provides a basis for rational vaccine design. However, it is still a highly technical and time‐consuming task to examine a protein's immunogenicity utilizing traditional approaches. Here, we present a platform for effectively evaluating protein immunogenicity and antibody detection. A tetanus toxin C fragment (Tet‐c) was used as a representative antigen to establish this platform. A cell wall‐anchoring sialidase‐like protein (SLP) of Propionibacterium acnes was utilized to assess the efficacy of this platform. We constructed an Escherichia coli vector‐based vaccine by overexpressing Tet‐c or SLP in E. coli and utilized an intact particle of E. coli itself as a vaccine (E. coli Tet‐c or SLP vector). After ultraviolet (UV) irradiation, the E. coli vector‐based vaccines were administered intranasally into imprinting control region mice without adding exogenous adjuvants. For antibody detection, we fabricated antigen microarrays by printing with purified recombinant proteins including Tet‐c and SLP. Our results demonstrated that detectable antibodies were elicited in mice 6 weeks after intranasal administration of UV‐irradiated E. coli vector‐based vaccines. The antibody production of Tet‐c and SLP was significantly elevated after boosting. Notably, the platform with main benefits of using E. coli itself as a vaccine carrier provides a critical template for applied proteomics aimed at screening novel vaccine targets. In addition, the novel immunogenic SLP potentially serves as an antigen candidate for the development of vaccines targeting P. acnes‐associated diseases.  相似文献   
284.
An experimental technique is presented to measure reflectance at high sample temperature with respect to room temperature in the infrared using Fourier transform infrared fitted with a reflectometer. Sample temperature artifacts are accounted for by sequential measurements taken with the lamp source on and with the lamp source off. The sequential measurements are shown mathematically to correct for the modulation of sample and detector thermal emissions. Further, the technique is applied to a polyimide (PMDA-ODA) film on a layer of gold deposited on a thermally oxidized Si wafer. It is shown that the optical properties (index of refraction and extinction coefficient) remain relatively constant with temperature (from room temperature to 380 degrees C) in the 4000-6000 cm(-1) spectral region. The significant changes that occur with temperature are the change in thickness of the film and also the spectral properties in the 2000-4000 cm(-1) region. Also, by using a Lorentz oscillator model, it is shown that this method is able to discern that spectral features corresponding to the OH stretching bands at 3630 and 3470 cm(-1) show significant variation with increasing temperature.  相似文献   
285.
Since the various people involved in the design process for a building project tend to hold conflicting views, this inevitably leads to a range of disparate models for planning and calculation purposes. In order to interpret the relevant geometrical, topological and semantical data for any given building model, we identify a structural component graph, a graph of room faces, a room graph and a relational object graph as aids and explain algorithms to derive these relations. We start with a building model by transferring its geometrical, topological and semantical data into a volume model, decomposing the latter into a so-called connection model and then extracting all air volume bodies and hulls of the model by means of further decomposition into elementary cyclic connection components. The technique is demonstrated within the scope of building energy simulation by deriving both a dimensionally reduced object model required for setting up a thermal multizone model and a geometrical model for defining single or multiple computational fluid dynamic domains in a building together with incidence matrices correlating these models. The algorithm is basically applicable to any building energy simulation tool.
Ernst RankEmail:
  相似文献   
286.
We present a dynamic comparison-based search structure that supports insertions, deletions, and searches within the unified bound. The unified bound specifies that it is quick to access an element that is near a recently accessed element. More precisely, if w(y)w(y) distinct elements have been accessed since the last access to element yy, and d(x,y)d(x,y) denotes the rank distance between xx and yy among the current set of elements, then the amortized cost to access element xx is O(minylog[w(y)+d(x,y)+2])O(minylog[w(y)+d(x,y)+2]). This property generalizes the working-set and dynamic-finger properties of splay trees.  相似文献   
287.
Ordered binary decision diagrams are the state-of-the-art representation of switching functions. In order to keep the sizes of OBDDs tractable, heuristics and dynamic reordering algorithms are applied to optimize the underlying variable order. When finite state machines are represented by OBDDs the state encoding can be used as an additional optimization parameter. In this paper, we analyze local encoding transformations which can be applied dynamically. First, we investigate the potential of re-encoding techniques. We then propose the use of an XOR-transformation and show why this transformation is most suitable among the set of all encoding transformations. The presented theoretical framework establishes a new optimization technique for OBDDs.  相似文献   
288.
Bounded Model Checking Using Satisfiability Solving   总被引:10,自引:1,他引:9  
The phrase model checking refers to algorithms for exploring the state space of a transition system to determine if it obeys a specification of its intended behavior. These algorithms can perform exhaustive verification in a highly automatic manner, and, thus, have attracted much interest in industry. Model checking programs are now being commercially marketed. However, model checking has been held back by the state explosion problem, which is the problem that the number of states in a system grows exponentially in the number of system components. Much research has been devoted to ameliorating this problem.In this tutorial, we first give a brief overview of the history of model checking to date, and then focus on recent techniques that combine model checking with satisfiability solving. These techniques, known as bounded model checking, do a very fast exploration of the state space, and for some types of problems seem to offer large performance improvements over previous approaches. We review experiments with bounded model checking on both public domain and industrial designs, and propose a methodology for applying the technique in industry for invariance checking. We then summarize the pros and cons of this new technology and discuss future research efforts to extend its capabilities.  相似文献   
289.
We present an approach for controlling robotic interactions with objects, using synthetic images generated by morphing shapes. In particular, we attempt the problem of positioning an eye-in-hand robotic system with respect to objects in the workspace for grasping and manipulation. In our formulation, the grasp position (and consequently the approach trajectory of the manipulator), varies with each object. The proposed solution to the problem consists of two parts. First, based on a model-based object recognition framework, images of the objects taken at the desired grasp pose are stored in a database. The recognition and identification of the grasp position for an unknown input object (selected from the family of recognizable objects) occurs by morphing its contour to the templates in the database and using the virtual energy spent during the morph as a dissimilarity measure. In the second step, the images synthesized during the morph are used to guide the eye-in-hand system and execute the grasp. The proposed method requires minimal calibration of the system. Furthermore, it conjoins techniques from shape recognition, computer graphics, and vision-based robot control in a unified engineering amework. Potential applications range from recognition and positioning with respect to partially-occluded or deformable objects to planning robotic grasping based on human demonstration.  相似文献   
290.
Analyzing the design of networks for visual information routing is an underconstrained problem due to insufficient anatomical and physiological data. We propose here optimality criteria for the design of routing networks. For a very general architecture, we derive the number of routing layers and the fanout that minimize the required neural circuitry. The optimal fanout l is independent of network size, while the number k of layers scales logarithmically (with a prefactor below 1), with the number n of visual resolution units to be routed independently. The results are found to agree with data of the primate visual system.  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