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   7091篇
  免费   622篇
  国内免费   5篇
电工技术   59篇
综合类   5篇
化学工业   1903篇
金属工艺   79篇
机械仪表   208篇
建筑科学   276篇
矿业工程   15篇
能源动力   151篇
轻工业   1490篇
水利工程   72篇
石油天然气   16篇
无线电   454篇
一般工业技术   1170篇
冶金工业   320篇
原子能技术   16篇
自动化技术   1484篇
  2024年   27篇
  2023年   87篇
  2022年   112篇
  2021年   284篇
  2020年   233篇
  2019年   229篇
  2018年   369篇
  2017年   373篇
  2016年   429篇
  2015年   308篇
  2014年   398篇
  2013年   729篇
  2012年   664篇
  2011年   596篇
  2010年   390篇
  2009年   381篇
  2008年   355篇
  2007年   350篇
  2006年   248篇
  2005年   184篇
  2004年   170篇
  2003年   142篇
  2002年   136篇
  2001年   68篇
  2000年   51篇
  1999年   39篇
  1998年   43篇
  1997年   43篇
  1996年   28篇
  1995年   36篇
  1994年   23篇
  1993年   27篇
  1992年   18篇
  1991年   14篇
  1990年   7篇
  1989年   13篇
  1988年   12篇
  1987年   6篇
  1986年   9篇
  1985年   14篇
  1984年   12篇
  1983年   6篇
  1982年   7篇
  1981年   11篇
  1979年   7篇
  1978年   3篇
  1976年   4篇
  1908年   2篇
  1905年   2篇
  1899年   2篇
排序方式: 共有7718条查询结果,搜索用时 15 毫秒
91.
The external administration of recombinant human erythropoietin is the chosen treatment for those patients with secondary anemia due to chronic renal failure in periodic hemodialysis. The objective of this paper is to carry out an individualized prediction of the EPO dosage to be administered to those patients. The high cost of this medication, its side-effects and the phenomenon of potential resistance which some individuals suffer all justify the need for a model which is capable of optimizing dosage individualization. A group of 110 patients and several patient factors were used to develop the models. The support vector regressor (SVR) is benchmarked with the classical multilayer perceptron (MLP) and the Autoregressive Conditional Heteroskedasticity (ARCH) model. We introduce a priori knowledge by relaxing or tightening the epsilon-insensitive region and the penalization parameter depending on the time period of the patients' follow-up. The so-called profile-dependent SVR (PD-SVR) improves results of the standard SVR method and the MLP. We perform sensitivity analysis on the MLP and inspect the distribution of the support vectors in the input and feature spaces in order to gain knowledge about the problem.  相似文献   
92.
In this work we propose a modification to the conventional lumped equivalent circuit model for integrated inductors. Also the widely used parametric model is modified. The proposed models expand the frequency range where the integrated inductor behavior is accurately predicted. They are useful in developing automatic tools to assist the designers in selecting and automatically laying-out integrated inductors [1]. This work is based on measurements from integrated inductors fabricated in a standard silicon process.  相似文献   
93.
Over the past decade, near‐infrared (NIR)‐emitting nanoparticles have increasingly been investigated in biomedical research for use as fluorescent imaging probes. Here, high‐quality water‐dispersible core/shell/shell PbS/CdS/ZnS quantum dots (hereafter QDs) as NIR imaging probes fabricated through a rapid, cost‐effective microwave‐assisted cation exchange procedure are reported. These QDs have proven to be water dispersible, stable, and are expected to be nontoxic, resulting from the growth of an outer ZnS shell and the simultaneous surface functionalization with mercaptopropionic acid ligands. Care is taken to design the emission wavelength of the QDs probe lying within the second biological window (1000–1350 nm), which leads to higher penetration depths because of the low extinction coefficient of biological tissues in this spectral range. Furthermore, their intense fluorescence emission enables to follow the real‐time evolution of QD biodistribution among different organs of living mice, after low‐dose intravenous administration. In this paper, QD platform has proven to be capable (ex vivo and in vitro) of high‐resolution thermal sensing in the physiological temperature range. The investigation, together with the lack of noticeable toxicity from these PbS/CdS/ZnS QDs after preliminary studies, paves the way for their use as outstanding multifunctional probes both for in vitro and in vivo applications in biomedicine.  相似文献   
94.
In Tunable-Transmitter Fixed-Receiver (TT-FR)-based Wavelength Division Multiplexed (WDM) ring topologies, each node is provided with a dedicated wavelength (home channel) for reception, which must be shared by the upstream nodes willing to communicate with it. Thus, to avoid channel collisions, it is necessary to define a Medium Access Control (MAC) mechanism that arbitrates access to a given destination wavelength. This work proposes and analyses a simple MAC mechanism that avoids channel collisions by recirculating traffic on the upstream ring segment where congestion was detected. Essentially, whenever a given node has got any traffic to transmit, it must first block access to in-transit traffic, which is reflected back to the upstream node over a second optical fibre. Such blocked traffic is given a second chance to pass through the congested node after a round segment delay, thus making use of the ring topology as buffering units. This work analyses the performance operation of such a MAC protocol under two policies applied to recirculated traffic: (1) recirculation bypass and (2) recirculation store-and-forward.  相似文献   
95.
The subscribers’ personal information and services that mobile operators are able to provide to Web developers offer new and exciting possibilities in numerous domains. However, bringing mobile information services to the Web to enable a new generation of mobile Web services presents several research challenges on identity and privacy management. In this paper, we describe a framework for identity management in mobile services that empowers users to govern the use and release of their personal information. Our framework is based on a brokering approach that intermediates between the mobile operator’s information services and the Web service providers. By leveraging on Web services, identity management infrastructure and privacy enhancing technologies, our framework provides an effective, privacy-considerate delivery of services over the mobile Web environment. This paper describes the design principles and architecture of the framework as well as the feasibility, applicability and user-experience evaluation we have carried out.  相似文献   
96.
An in-vitro method using commercially available enzymes for the prediction of the in-vivo digestible crude protein content was developed and tested on seven feedstuffs and 16 diets for pigs. Fat-extracted feed samples were consecutively incubated with pepsin at pH 1 and pancreatin at pH 6.8. From the nitrogen content of the feed sample and of the residue after incubation the in-vitro digestibility of the crude protein was calculated. Using the linear regression of in-vitro on in-vivo digestible crude protein of samples obtained in feeding trials, the in-vivo digestible crude protein content (DXPp) in g kg?1 dry matter could be predicted. For feedstuffs and diets the correlation was 0.99 and 0.95 and the residual standard deviation 17 and 6 g kg?1 dry matter, respectively. In a similar procedure the nitrogen solubilised during incubation with enzymes was analysed. The regression value was similar to that of the original procedure. However, this procedure was abandoned because it was more laborious.  相似文献   
97.
The MPLS platform enables the implementation of advanced multipath and multicast routing schemes. This work develops and analyses the performance of a new bi-criteria minimum spanning tree model intended for routing broadcast messages in MPLS networks or constructing tree-based overlay networks. The aim of the model is to obtain spanning trees which are compromise solutions with respect to two important traffic engineering metrics: load balancing cost and average delay bound. An exact solution to the formulated bi-criteria optimization problem is presented, which is based on an algorithm that enables the computation of the set of supported non-dominated spanning trees. An application model and a set of experiments on randomly generated Internet type topologies will also be presented. Finally a network performance analysis of the model considering three network performance metrics will be shown.  相似文献   
98.
The separation ability of branched alkane isomers (nHEX, 3MP, 22DMB) of the flexible and functionalized microporous iron(III) dicarboxylate MIL‐53(Fe)‐(CF3)2 solid is evaluated through a combination of breakthrough experiments (binary or ternary mixtures), adsorption isotherms, X‐ray diffraction temperature analysis, quasi‐elastic neutron scattering measurements and molecular dynamics simulations. A kinetically controlled molecular sieve separation between the di‐branched isomer of hexane 22DMB from a mixture of paraffins is achieved. The reported total separation between mono‐ and di‐branched alkanes which was neither predicted nor observed so far in any class of porous solids is spectacular and paves the way towards a potential unprecedented upgrading of the RON of gasoline.  相似文献   
99.
This is a position paper on our views on security aspects of Wireless Multimedia Sensor Networks (Secure WMSNs). It is meant to serve as a brief survey. But, more importantly, it gives a perspective on how we foresee the future of this research area, its main challenges, and its future trends. We believe that this paper will spur new discussions and research ideas among the researchers from both the industry and the academic world.  相似文献   
100.
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