全文获取类型
收费全文 | 37734篇 |
免费 | 4621篇 |
国内免费 | 3518篇 |
专业分类
电工技术 | 3199篇 |
技术理论 | 2篇 |
综合类 | 6717篇 |
化学工业 | 1583篇 |
金属工艺 | 813篇 |
机械仪表 | 2649篇 |
建筑科学 | 2648篇 |
矿业工程 | 791篇 |
能源动力 | 753篇 |
轻工业 | 2297篇 |
水利工程 | 1030篇 |
石油天然气 | 850篇 |
武器工业 | 485篇 |
无线电 | 5042篇 |
一般工业技术 | 3646篇 |
冶金工业 | 781篇 |
原子能技术 | 488篇 |
自动化技术 | 12099篇 |
出版年
2024年 | 72篇 |
2023年 | 469篇 |
2022年 | 786篇 |
2021年 | 943篇 |
2020年 | 992篇 |
2019年 | 919篇 |
2018年 | 939篇 |
2017年 | 1124篇 |
2016年 | 1250篇 |
2015年 | 1335篇 |
2014年 | 2010篇 |
2013年 | 2271篇 |
2012年 | 2679篇 |
2011年 | 2888篇 |
2010年 | 2292篇 |
2009年 | 2462篇 |
2008年 | 2560篇 |
2007年 | 2957篇 |
2006年 | 2625篇 |
2005年 | 2327篇 |
2004年 | 1949篇 |
2003年 | 1622篇 |
2002年 | 1336篇 |
2001年 | 1134篇 |
2000年 | 977篇 |
1999年 | 814篇 |
1998年 | 652篇 |
1997年 | 566篇 |
1996年 | 522篇 |
1995年 | 470篇 |
1994年 | 403篇 |
1993年 | 287篇 |
1992年 | 256篇 |
1991年 | 214篇 |
1990年 | 191篇 |
1989年 | 173篇 |
1988年 | 114篇 |
1987年 | 66篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 33篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1965年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Yoshihiro Maruyama Takumi Hamaguchi Tien-Hsiu Tsai 《Journal of Nuclear Science and Technology》2018,55(2):199-208
A new ‘transXend’ detector system has been developed for energy-resolved computed tomography (CT). It consists of several segmented detectors that measure X-rays as electric currents. Response functions of segmented detectors are estimated using component materials of a body under inspection to unfold X-ray spectra. To avoid material-dependent measurements, response functions inherent to segmented detectors are evaluated by Monte Carlo calculations. CT was performed for a phantom consisting of five resins and was analyzed by the estimated response functions. The linear attenuation coefficients for the five resins have excellent agreement with database values. 相似文献
992.
Optogenetics Comes of Age: Novel Inhibitory Light‐Gated Anionic Channels Allow Efficient Silencing of Neural Function 下载免费PDF全文
Dr. Alex Peralvárez‐Marín Prof. Pere Garriga 《Chembiochem : a European journal of chemical biology》2016,17(3):204-206
Optogenetics, the developing field of research that uses light‐switchable biochemical tools in a sophisticated technological approach to monitor or control neural function, is rapidly evolving with the discovery and development of novel microbial rhodopsins. Light‐absorbing membrane proteins, as tools for brain research, are promoting new applications within the discipline of optogenetics. Light‐gated rhodopsin ion channels with better intrinsic light sensitivity and improved resolution are needed to overcome some of the current limitations of existing molecules. The recent discovery of light‐gated inhibitory anion channels opens new opportunities for studying physiological neural processes and, at the same time, represent a powerful approach for elucidating the mechanisms of neurological and mental disorders that could benefit from this approach. 相似文献
993.
Hyeonjoong Cho Binoy Ravindran E. Douglas Jensen 《Journal of Parallel and Distributed Computing》2010
We present the first Utility Accrual (or UA) real-time scheduling algorithm for multiprocessors, called the global Multiprocessor Utility Accrual scheduling algorithm (or gMUA). The algorithm considers an application model where real-time activities are subject to time/utility function time constraints, variable execution time demands, and resource overloads where the total activity utilization demand exceeds the total capacity of all processors. We consider the scheduling objective of (1) probabilistically satisfying lower bounds on each activity’s maximum utility, and (2) maximizing the system-wide, total accrued utility. We establish several properties of gMUA including optimal total utility (for a special case), conditions under which individual activity utility lower bounds are satisfied, a lower bound on system-wide total accrued utility, and bounded sensitivity for assurances to variations in execution time demand estimates. Finally, our simulation experiments validate our analytical results and confirm the algorithm’s effectiveness. 相似文献
994.
995.
A coupled volume-of-fluid and level set (VOSET) method for computing incompressible two-phase flows 总被引:1,自引:0,他引:1
D.L. Sun 《International Journal of Heat and Mass Transfer》2010,53(4):645-655
A coupled volume-of-fluid and level set (VOSET) method, which combines the advantages and overcomes the disadvantages of VOF and LS methods, is presented for computing incompressible two-phase flows. In this method VOF method is used to capture interfaces, which can conserve the mass and overcome the disadvantage of nonconservation of mass in LS method. An iterative geometric operation proposed by author is used to calculate the level set function ? near interfaces, which can be applied to compute the accurate curvature κ and smooth the discontinuous physical quantities near interfaces. By using the level set function ? the disadvantages of VOF method, inaccuracy of curvature and bad smoothness of discontinuous physical quantities near interfaces, can be overcome. Finally the computing results made with VOSET method are compared with those made with VOF and LS methods. 相似文献
996.
Accurate convective heat transfer predictions are required in building engineering and environmental studies on urban heat islands, building energy performance, building-envelope durability or conservation and (natural) ventilation of buildings. When applying computational fluid dynamics (CFD) for these computationally-expensive studies at high-Reynolds numbers, wall functions are mostly used to model the boundary-layer region. In this study, an adjustment to the standard temperature wall function is proposed for forced convective heat transfer at surfaces of typical wall-mounted bluff bodies in turbulent boundary layers, such as the atmospheric boundary layer, at moderate to high Reynolds numbers. The methodology to determine this customised temperature wall function (CWF) from validated numerical data of CFD simulations using low-Reynolds number modelling (LRNM) is explained, where a logarithmic- law behaviour is found. The performance of this CWF is evaluated for several bluff-body configurations. Standard wall functions (SWFs) yield deviations of about 40% for the convective heat transfer coefficient, compared to LRNM. With the CWF however, these deviations are reduced to about 10% or lower. The CWF therefore combines increased (wall-function) accuracy for convective heat transfer predictions with the typical advantage of wall functions compared to LRNM, being a lower grid resolution in the near-wall region, which increases computational economy and facilitates grid generation. Furthermore, this CWF can be easily implemented in existing CFD codes, and is implemented in the commercial CFD code Fluent in this study. 相似文献
997.
998.
999.
Modelling and parameter identification of complex dynamic systems/processes is one of the main challenging problems in control engineering. An example of such a process is clinker rotary kiln (CRK) in cement industry. In the prevailing models independently of which structure is used to describe the kiln's dynamics and the identification algorithm, parameters are assumed to be centralised and constant while the CRK is well known as a distributed parameter system with a strongly varying dynamic through time. In this work, the kiln's dynamic is described in the form of a state‐space representation with three state variables using a system of partial differential equations (PDE). The structure is chosen so that it can easily be embedded in classical state‐space control algorithms. The parameters of the PDE system are called operating functions since their numerical values vary with respect to different operating conditions of the kiln, to their position in the kiln, and through time. A phenomenological approach is also proposed in this paper to identify the operating functions for a given steady‐state operation of the kiln. The model is then used to perform a semi‐dynamic simulation of the process through manipulating main process variables. 相似文献
1000.
Boris Škori? Chibuzo ObiEvgeny Verbitskiy Berry Schoenmakers 《Information and Computation》2011,209(8):1184-1196
Extraction of uniform randomness from (noisy) non-uniform sources is an important primitive in many security applications, e.g. (pseudo-)random number generators, privacy-preserving biometrics, and key storage based on Physical Unclonable Functions. Generic extraction methods exist, using universal hash functions. There is a trade-off between the length of the extracted bit string and the uniformity of the string. In the literature there are proven lower bounds on this length as a function of the desired uniformity. The best known bound involves a quantity known as smooth min-entropy. Unfortunately, there exist at least three definitions of smooth entropy. In this paper we compare three of these definitions, and we derive improved lower bounds on the extractable randomness.We also investigate the use of almost universal hash functions, which are slightly worse at extracting randomness than universal hash functions, but are preferable in practice because they require far less resources in devices. We show that using them has negligible effect on the extractable randomness. 相似文献