全文获取类型
收费全文 | 3620篇 |
免费 | 142篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 40篇 |
综合类 | 5篇 |
化学工业 | 805篇 |
金属工艺 | 63篇 |
机械仪表 | 97篇 |
建筑科学 | 151篇 |
矿业工程 | 17篇 |
能源动力 | 63篇 |
轻工业 | 327篇 |
水利工程 | 28篇 |
石油天然气 | 13篇 |
无线电 | 296篇 |
一般工业技术 | 615篇 |
冶金工业 | 693篇 |
原子能技术 | 21篇 |
自动化技术 | 534篇 |
出版年
2022年 | 45篇 |
2021年 | 74篇 |
2020年 | 63篇 |
2019年 | 47篇 |
2018年 | 69篇 |
2017年 | 65篇 |
2016年 | 96篇 |
2015年 | 65篇 |
2014年 | 102篇 |
2013年 | 239篇 |
2012年 | 187篇 |
2011年 | 227篇 |
2010年 | 149篇 |
2009年 | 151篇 |
2008年 | 152篇 |
2007年 | 161篇 |
2006年 | 118篇 |
2005年 | 85篇 |
2004年 | 92篇 |
2003年 | 98篇 |
2002年 | 91篇 |
2001年 | 57篇 |
2000年 | 40篇 |
1999年 | 65篇 |
1998年 | 112篇 |
1997年 | 68篇 |
1996年 | 48篇 |
1995年 | 51篇 |
1994年 | 40篇 |
1993年 | 49篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 40篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 41篇 |
1984年 | 26篇 |
1983年 | 35篇 |
1982年 | 30篇 |
1981年 | 33篇 |
1980年 | 32篇 |
1979年 | 33篇 |
1978年 | 34篇 |
1977年 | 35篇 |
1976年 | 35篇 |
1975年 | 42篇 |
1974年 | 24篇 |
1973年 | 21篇 |
排序方式: 共有3768条查询结果,搜索用时 31 毫秒
81.
Antonio de la Oliva Ignacio Soto Albert Banchs Johannes Lessmann Christian Niephaus Telemaco MeliaAuthor vitae 《Computer Standards & Interfaces》2011,33(6):556-564
The IEEE 802.21 standard facilitates media independent handovers by providing higher layer mobility management functions with common service primitives for all technologies. Right after the base specification was published, several voices rose up in the working group advocating to broaden the scope of IEEE 802.21 beyond handovers. This paper aims at updating the reader with the main challenges and functionalities required to create a Media Independence Service Layer, through the analysis of scenarios which are being discussed within the working group: 1) Wireless Coexistence, and 2) Heterogeneous Wireless Multihop Backhaul Networks. 相似文献
82.
The separation of mixed auditory signals into their sources is an eminent neuroscience and engineering challenge. We reveal the principles underlying a deterministic, neural network-like solution to this problem. This approach is orthogonal to ICA/PCA that views the signal constituents as independent realizations of random processes. We demonstrate exemplarily that in the absence of salient frequency modulations, the decomposition of speech signals into local cosine packets allows for a sparse, noise-robust speaker separation. As the main result, we present analytical limitations inherent in the approach, where we propose strategies of how to deal with this situation. Our results offer new perspectives toward efficient noise cleaning and auditory signal separation and provide a new perspective of how the brain might achieve these tasks. 相似文献
83.
84.
Most empirical investigations of the business cycles in the United States have excluded the dimension of asymmetric conditional volatility. This paper analyses the volatility dynamics of the US business cycle by comparing the performance of various multivariate generalised autoregressive conditional heteroskedasticity (GARCH) models. In particular, we propose two bivariate GARCH models to examine the evidence of volatility asymmetry and time-varying correlations concurrently, and then apply the proposed models to five sectors of Industrial Production of the United States. Our findings provide strong evidence of asymmetric conditional volatility in all sectors, and some support of time-varying correlations in various sectoral pairs. This has important policy implications for government to consider the effective countercyclical measures during recessions. 相似文献
85.
Health Outcomes and Socio-economic Status Among the Elderly in China: Evidence from the CHARLS Pilot
John Strauss Xiaoyan Lei Albert Park Yan Shen James P. Smith Zhe Yang Yaohui Zhao 《Journal of population ageing》2010,3(3-4):111-142
We are concerned in this paper with measuring health outcomes among the elderly in Zhejiang and Gansu provinces, China, and examining the relationships between different dimensions of health status and measures of socio-economic status (SES). We are CHARLS pilot data to document health conditions, using a very rich set of health indicators that include both self-reported measures and biomarkers. We also examine correlations between these health outcomes and two important indicators of socio-economic status (SES): education and log of per capita expenditure (log pce), our preferred measure of household resources. In general education tends to be positively correlated with better health outcomes, as it is in other countries. However, unmeasured community influences turn out to be highly important, much more so than one usually finds in other countries. While it is not yet clear which aspects of communities matter and why they matter, we set up an agenda for future research on this topic. We also find a large degree of under-diagnosis of hypertension, a major health problems that afflicts the aged. This implies that the current health system is not well prepared to address the rapid aging of the Chinese population, at least not in Gansu and Zhejiang. 相似文献
86.
A physical model describing the I(V) characteristics of planar limiting current oxygen sensors based in an ion-conducting electrolyte is presented. The model focuses on the minimization of the electrochemical potential and the diffusion across a porous layer covering the measuring electrode. The proposed model describes three key phenomena in the response of the sensors: the influence of the polarization resistance on the slope of I(V), the linearity between the limiting current and the diffusivity of the porous layer and a low non-zero current at zero polarization. 相似文献
87.
A survey and taxonomy on energy efficient resource allocation techniques for cloud computing systems
Abdul Hameed Alireza Khoshkbarforoushha Rajiv Ranjan Prem Prakash Jayaraman Joanna Kolodziej Pavan Balaji Sherali Zeadally Qutaibah Marwan Malluhi Nikos Tziritas Abhinav Vishnu Samee U. Khan Albert Zomaya 《Computing》2016,98(7):751-774
In a cloud computing paradigm, energy efficient allocation of different virtualized ICT resources (servers, storage disks, and networks, and the like) is a complex problem due to the presence of heterogeneous application (e.g., content delivery networks, MapReduce, web applications, and the like) workloads having contentious allocation requirements in terms of ICT resource capacities (e.g., network bandwidth, processing speed, response time, etc.). Several recent papers have tried to address the issue of improving energy efficiency in allocating cloud resources to applications with varying degree of success. However, to the best of our knowledge there is no published literature on this subject that clearly articulates the research problem and provides research taxonomy for succinct classification of existing techniques. Hence, the main aim of this paper is to identify open challenges associated with energy efficient resource allocation. In this regard, the study, first, outlines the problem and existing hardware and software-based techniques available for this purpose. Furthermore, available techniques already presented in the literature are summarized based on the energy-efficient research dimension taxonomy. The advantages and disadvantages of the existing techniques are comprehensively analyzed against the proposed research dimension taxonomy namely: resource adaption policy, objective function, allocation method, allocation operation, and interoperability. 相似文献
88.
Hybrid additive-subtractive manufacturing is gaining popularity by making full use of geometry complexity produced by additive manufacturing and dimensional accuracy derived from subtractive machining. Part design for this hybrid manufacturing approach has been done by trial-and-error, and no dedicated design methodology exists for this manufacturing approach. To address this issue, this work presents a topology optimization method for hybrid additive and subtractive manufacturing. To be specific, the boundary segments of the input design domain are categorized into two types: (i) Freeform boundary segments freely evolve through the casting SIMP method, and (ii) shape preserved boundary segments suppress the freeform evolvement and are composed of machining features through a feature fitting algorithm. Given the manufacturing strategy, the topology design is produced through additive manufacturing and the shape preserved boundary segments will be processed by post-machining. This novel topology optimization algorithm is developed under a unified SIMP and level set framework. The effectiveness of the algorithm is proved through a few numerical case studies. 相似文献
89.
Albert Visser 《Theoretical computer science》2011,412(28):3404-3411
In this paper we study an alternative way of treating Polish notation. Instead of proving unique reading for a well-behaved set of terms, we interpret any string of the alphabet in a monoid that extends, in a specifiable sense, the given algebra of functions. 相似文献
90.
Determining a tight WCET of a block of code to be executed on a modern superscalar processor architecture is becoming ever more difficult due to the dynamic behaviour exhibited by current processors, which include dynamic scheduling features such as speculative and out-of-order execution in the context of multiple execution units with deep pipelines. We describe the use of Coloured Petri Nets (CP-nets) in a simulation based approach to this problem. A complex model of a generic processor architecture is described, with emphasis on the modelling strategy for obtaining the WCET and an analysis of the results. 相似文献