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   514篇
  免费   42篇
  国内免费   2篇
电工技术   2篇
化学工业   236篇
金属工艺   12篇
机械仪表   9篇
建筑科学   17篇
矿业工程   2篇
能源动力   20篇
轻工业   36篇
水利工程   2篇
石油天然气   1篇
无线电   19篇
一般工业技术   62篇
冶金工业   12篇
原子能技术   2篇
自动化技术   126篇
  2024年   4篇
  2023年   8篇
  2022年   66篇
  2021年   73篇
  2020年   21篇
  2019年   19篇
  2018年   28篇
  2017年   28篇
  2016年   34篇
  2015年   30篇
  2014年   26篇
  2013年   32篇
  2012年   30篇
  2011年   35篇
  2010年   18篇
  2009年   20篇
  2008年   19篇
  2007年   11篇
  2006年   10篇
  2005年   7篇
  2004年   5篇
  2003年   5篇
  2002年   5篇
  2001年   1篇
  2000年   4篇
  1999年   2篇
  1998年   3篇
  1997年   5篇
  1996年   3篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1986年   1篇
  1980年   1篇
排序方式: 共有558条查询结果,搜索用时 245 毫秒
51.
This paper is a first‐hand summary on our comprehensive live trial of cellular‐assisted device‐to‐device (D2D) communications currently being ratified by the standards community for next‐generation mobile broadband networks. In our test implementation, we employ a full‐featured 3GPP LTE network deployment and augment it with all necessary support to provide real‐time D2D connectivity over emerging Wi‐Fi‐Direct (WFD) technology. As a result, our LTE‐assisted WFD D2D system enjoys the required flexibility while meeting the existing standards in every feasible detail. Further, this paper provides an account on the extensive measurement campaign conducted with our implementation. The resulting real‐world measurements from this campaign quantify the numerical effects of D2D functionality on the resultant system performance. Consequently, they shed light on the general applicability of LTE‐assisted WFD solutions and associated operational ranges.  相似文献   
52.
Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.  相似文献   
53.
A new biosensor platform for the detection of bacterial pathogens based on long-range surface plasmon-enhanced fluorescence spectroscopy (LRSP-FS) is presented. The resonant excitation of LRSP modes provides an enhanced intensity of the electromagnetic field, which is directly translated to an increased strength of fluorescence signal measured upon the capture of target analyte at the sensor surface. LRSPs originate from a coupling of surface plasmons across a thin metallic film embedded in dielectrics with similar refractive indices. With respect to regular surface plasmon-enhanced fluorescence spectroscopy, the excitation of LRSPs offers the advantage of a larger enhancement of the evanescent field intensity and a micrometer probing depth that is comparable to the size of target bacterial pathogens. The potential of the developed sensor platform is demonstrated in an experiment in which the detection of E. coli O157:H7 was carried out using sandwich immunoassays. The limit of detection below 10 cfu mL(-1) and detection time of 40 min were achieved.  相似文献   
54.
In this article we present SMES–SPPC, a high–performance system for intelligent extraction of structured data from free text documents. SMES–SPPC consists of a set of domain–adaptive shallow core components that are realized by means of cascaded weighted finite–state machines and generic dynamic tries. The system has been fully implemented for German; it includes morphological and on–line compound analysis, efficient POS–filtering, high–performance named–entity recognition and chunk parsing based on a novel divide–and–conquer strategy. The whole approach proved to be very useful for processing free word order languages such as German. SMES–SPPC has a good performance (more than 6000 words per second on standard PC environments) and achieves high linguistic coverage, especially for the divide–and–conquer parsing strategy, where we obtained an f –measure of 87.14% on unseen data.  相似文献   
55.
Data are reviewed indicating that allosteric modulators can enhance the affinities of muscarinic receptors for their antagonists and agonists, that the enhancement of the affinity for agonists is relevant functionally, and that the allosterically induced conformational change also affects the interaction between the receptors and the G proteins.  相似文献   
56.
This is the fourth and final article in a series of articles dealing with the metallographic preparation and evaluation of thermal spray coatings. Previous articles have covered variables and best practices for the sectioning, mounting, and coarse grinding of coated components. In this article, the relationship between fine grinding and polishing practices, consumables, and resultant plasma spray coating structure are discussed.  相似文献   
57.
Identifying the cutting tool type used in excavations using neural networks   总被引:1,自引:1,他引:0  
The paper presents results of preliminary research on utilising neural networks to identify excavating cutting tool’s type used in multi-tool excavating heads of mechanical coal miners. Such research is necessary to identify rock excavating process with a given head, and construct adaptation systems for control of excavating process with such a head.  相似文献   
58.
 Torsion classes of MV-algebras are defined as radical classes which are closed with respect to homomorphisms; in this paper we investigate their relations to radical classes of lattice ordered groups and to varieties of MV-algebras. Supported by Grant VEGA 1/9056/02.  相似文献   
59.
The Electronegativity Equalization Method (EEM) is a fast approach for charge calculation. A challenging part of the EEM is the parameterization, which is performed using ab initio charges obtained for a set of molecules. The goal of our work was to perform the EEM parameterization for selected sets of organic, organohalogen and organometal molecules. We have performed the most robust parameterization published so far. The EEM parameterization was based on 12 training sets selected from a database of predicted 3D structures (NCI DIS) and from a database of crystallographic structures (CSD). Each set contained from 2000 to 6000 molecules. We have shown that the number of molecules in the training set is very important for quality of the parameters. We have improved EEM parameters (STO-3G MPA charges) for elements that were already parameterized, specifically: C, O, N, H, S, F and Cl. The new parameters provide more accurate charges than those published previously. We have also developed new parameters for elements that were not parameterized yet, specifically for Br, I, Fe and Zn. We have also performed crossover validation of all obtained parameters using all training sets that included relevant elements and confirmed that calculated parameters provide accurate charges.  相似文献   
60.
Detailed mechanisms of the switch of the cell death mode from apoptosis to necrosis remain to be solved, although the intracellular level of ATP and that of free radicals have been postulated to be the major factors involved in the mechanisms. In the present study menadione (MEN)-induced cell injury processes were studied using rho0 cells derived from human osteosarcoma 143B cells and parental rho+ cells co-treated with inhibitors of electron transfer chain of mitochondria or oligomycin, an inhibitor of ATP synthesis. Treatment of rho+ cells with 100 microM MEN induced apoptosis, which reached the maximum at 6 h, and was followed by an abrupt decrease thereafter, while necrotic cells (NC) increased continuously when they were judged by Annexin V and PI double staining. On the other hand, MEN induced apoptotic and necrotic changes much faster in rho0 cells compared to rho+ cells. The frequency to find apoptotic cells (AP) in the former cells was distinctly smaller than that to find NC judged by Annexin V and PI double staining. Electron microscopically, a major population of rho0 cells treated with MEN for 6 h consisted of intermediate cells, and a small number of AP co-existed. At 9 h of the treatment intermediate cells were exclusively seen, and AP were hardly detected. When parental rho+ cells were treated with MEN in the presence of oligomycin or oligomycin plus antimycin A both apoptotic and necrotic changes of the cells were distinctly accelerated. The intracellular level of superoxide in rho0 cells continuously increased after the MEN treatment, whereas that of ATP remained distinctly low before and after the MEN treatment compared to that in rho+ cells. These data suggest that the intracellular level of superoxide may be a key factor controlling the switch from apoptosis to necrosis.  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