全文获取类型
收费全文 | 1018篇 |
免费 | 50篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 193篇 |
金属工艺 | 12篇 |
机械仪表 | 18篇 |
建筑科学 | 50篇 |
矿业工程 | 1篇 |
能源动力 | 98篇 |
轻工业 | 69篇 |
水利工程 | 4篇 |
石油天然气 | 6篇 |
无线电 | 72篇 |
一般工业技术 | 197篇 |
冶金工业 | 124篇 |
原子能技术 | 7篇 |
自动化技术 | 209篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 47篇 |
2020年 | 33篇 |
2019年 | 24篇 |
2018年 | 25篇 |
2017年 | 36篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 42篇 |
2013年 | 56篇 |
2012年 | 45篇 |
2011年 | 54篇 |
2010年 | 38篇 |
2009年 | 47篇 |
2008年 | 37篇 |
2007年 | 35篇 |
2006年 | 33篇 |
2005年 | 18篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 19篇 |
1998年 | 30篇 |
1997年 | 26篇 |
1996年 | 12篇 |
1995年 | 16篇 |
1994年 | 29篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有1070条查询结果,搜索用时 0 毫秒
41.
Experimental study on the time‐dependent smoke densities at 39 locations in a multi‐floor building through a digital smoke detector system
下载免费PDF全文
![点击此处可从《火与材料》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The objective of this study was to quantitatively investigate some characteristics of the smoke transportation in multi‐floor buildings. Eight experiments were conducted for worst scenario. The effects of an open window in the burning room on the smoke transportation are also analyzed. The time‐dependent smoke densities at 39 locations in a half‐scale building with an atrium were measured through a digital smoke detector system. The results indicate that the chimney effect plays an important role in the smoke transportation in multi‐floor buildings with atriums. For the effects of the open window, the results suggest that the smoke densities at most locations in the building increase earlier when a window is open but have a smaller peak value than those results in the cases without any outer vents. It is suggested that a building without vertical atrium would be safer than those with long ones. More attention should be paid to those spaces when the fire protection systems are designed for buildings with atriums. The data of the time‐dependent smoke densities at tens of locations in the building are useful for the validation of smoke transportation models. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
42.
This work investigates the effects of recycled engine oil bottoms (REOBs) on asphalt field performance by comparing asphalts with and without REOBs in terms of the asphalt properties required for pavement oxidation modeling. Specifically, oxidation reaction kinetics parameters, dynamic shear rheometer (DSR) function (DSRFn) hardening susceptibility (HS), and low sheer viscosity (LSV) HS are determined and compared for base binder, 5 wt.% REOBs, and 15 wt.% REOBs blends. At the higher percentage, addition of REOBs appears to increase the initial oxidation rate at field temperatures and significantly increases LSV HS, but does not significantly increase the DSRFn HS. A field modeling example elucidates the effects. 相似文献
43.
44.
45.
Combined continuum damage‐embedded discontinuity model for explicit dynamic fracture analyses of quasi‐brittle materials
下载免费PDF全文
![点击此处可从《International journal for numerical methods in engineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Timo Saksala Delphine Brancherie Isaac Harari Adnan Ibrahimbegovic 《International journal for numerical methods in engineering》2015,101(3):230-250
In this paper, a novel constitutive model combining continuum damage with embedded discontinuity is developed for explicit dynamic analyses of quasi‐brittle failure phenomena. The model is capable of describing the rate‐dependent behavior in dynamics and the three phases in failure of quasi‐brittle materials. The first phase is always linear elastic, followed by the second phase corresponding to fracture‐process zone creation, represented with rate‐dependent continuum damage with isotropic hardening formulated by utilizing consistency approach. The third and final phase, involving nonlinear softening, is formulated by using an embedded displacement discontinuity model with constant displacement jumps both in normal and tangential directions. The proposed model is capable of describing the rate‐dependent ductile to brittle transition typical of cohesive materials (e.g., rocks and ice). The model is implemented in the finite element setting by using the CST elements. The displacement jump vector is solved for implicitly at the local (finite element) level along with a viscoplastic return mapping algorithm, whereas the global equations of motion are solved with explicit time‐stepping scheme. The model performance is illustrated by several numerical simulations, including both material point and structural tests. The final validation example concerns the dynamic Brazilian disc test on rock material under plane stress assumption. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
46.
Afshin Behzadan Alagan Anpalagan Isaac Woungang Bobby Ma Han‐Chieh Chao 《Wireless Communications and Mobile Computing》2015,15(16):2020-2037
A utility‐based distributed data routing algorithm is proposed and evaluated for heterogeneous wireless sensor networks. It is energy efficient and is based on a game‐theoretic heuristic load‐balancing approach. It runs on a hierarchical graph arranged as a tree with parents and children. Sensor nodes are considered heterogeneous in terms of their generated traffic, residual energy and data transmission rate and the bandwidth they provide to their children for communication. The proposed method generates a data routing tree in which child nodes are joined to parent nodes in an energy‐efficient way. The principles of the Stackelberg game, in which parents as leaders and children as followers, are used to support the distributive nature of sensor networks. In this context, parents behave cooperatively and help other parents to adjust their loads, while children act selfishly. Simulation results indicate the proposed method can produce on average more load‐balanced trees, resulting in over 30% longer network lifetime compared with the cumulative algorithm proposed in the literature. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
47.
Implementing Residual‐Based KPSS Tests for Cointegration with Data Subject to Temporal Aggregation and Mixed Sampling Frequencies
下载免费PDF全文
![点击此处可从《时间序列分析杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We show how different data types (stocks and flows) and temporal aggregation affect the size and power of the dynamic ordinary least squares residual‐based Kwiatkowski–Phillips–Schmidt–Shin (KPSS) test of the null of cointegration. Size may be more effectively controlled by setting the minimum number of leads equal to one – as opposed to zero – when selecting the lag/lead order of the dynamic ordinary least squares regression using aggregated data, but at a cost to power. If high‐frequency data for one or more series are available – that is, the model has mixed sampling frequencies – we show how to effectively utilize the high‐frequency data to increase power while controlling size. 相似文献
48.
This article develops an improved seismic risk assessment formulation exhibiting both random and bounded uncertainties using a probability and parallelepiped convex set mixed model. Limit thresholds for different types of components are described via a probabilistic model. The distribution parameters of limit thresholds are originally treated by employing a multidimensional parallelepiped convex model, in which marginal intervals are utilised to represent scattering levels for the distribution parameters, while relevant angle are employed to express the correlation between uncertain distribution parameters. The structural responses, i.e., engineering demand parameters (EDPs), are considered as correlated random variables and are assumed to follow a multidimensional lognormal distribution. A performance limit state function, which allows considering the relationship between the EDPs and the corresponding limit thresholds, is employed to reflect the coexistence of both random and parallelepiped convex variables. The limit state function is mapped into the standard parameter space via a transformation technique. Then, the improved seismic risk formulation, characterised through a probability and parallelepiped convex mixed variables, can be derived with the combination of the seismic fragility function and the ground motion hazard curve. The main purpose is to illustrate that the performance limit states should be properly modeled as random and parallelepiped convex mixed variables rather than only random or deterministic quantities. A six-story reinforced concrete building designed according to Chinese codes are used to illustrate the proposed approach for constructing hazard curves. The interstory drift and the peak floor acceleration are the selected EDPs, calculated through incremental dynamic analysis. The results demonstrate that the calculated failure probabilities for different limit states in 50?years are found capable of meeting the requirements of Chinese seismic norms after the proposed seismic risk formulation is adopted. 相似文献
49.
Juan Carlos Fernndez-Martín Ana María Espinosa-Oliva Irene García-Domínguez Isaac Rosado-Snchez Yolanda M. Pacheco Rosario Moyano Jos G. Monterde Jos Luis Venero Rocío M. de Pablos 《International journal of molecular sciences》2022,23(3)
Lipopolysaccharide (LPS)-induced endotoxemia induces an acute systemic inflammatory response that mimics some important features of sepsis, the disease with the highest mortality rate worldwide. In this work, we have analyzed a murine model of endotoxemia based on a single intraperitoneal injection of 5 mg/kg of LPS. We took advantage of galectin-3 (Gal3) knockout mice and found that the absence of Gal3 decreased the mortality rate oflethal endotoxemia in the first 80 h after the administration of LPS, along with a reduction in the tissular damage in several organs measured by electron microscopy. Using flow cytometry, we demonstrated that, in control conditions, peripheral immune cells, especially monocytes, exhibited high levels of Gal3, which were early depleted in response to LPS injection, thus suggesting Gal3 release under endotoxemia conditions. However, serum levels of Gal3 early decreased in response to LPS challenge (1 h), an indication that Gal3 may be extravasated to peripheral organs. Indeed, analysis of Gal3 in peripheral organs revealed a robust up-regulation of Gal3 36 h after LPS injection. Taken together, these results demonstrate the important role that Gal3 could play in the development of systemic inflammation, a well-established feature of sepsis, thus opening new and promising therapeutic options for these harmful conditions. 相似文献
50.
Frederick Wieland Lawrence Hawley Abe Feinberg Mike Di Loreto Leo Blume Joseph Ruffles Peter Reiher Brian Beckman Philip Hontalas Steven Bellenot David Jefferson 《Concurrency and Computation》1989,1(1):35-50
This paper analyzes the performance of a discrete-event combat simulation executed on a parallel processor under control of the Time Warp Operating System. Time Warp is in a class of distributed simulation methods called Optimistic methods which have proven to be useful over a wide range of simulations. The combat simulation used for this performance study, called STB88, is a division-corps model incorporating a number of different types of computations. The speed-up for three versions of this model on the Caltech/JPL Mark III Hypercube and the BBN Butterfly parallel processors was measured relative to an efficient sequential execution of the same model on the same hardware. The results indicate that STB88 version 1 achieves a speed-up of 28.6 on 60 Mark III processors, while STB88 version 2 achieves a speed-up of 36.8 on 100 Butterfly processors. Version 3 of STB88 achieved a speed-up of 38.5 on 128 Mark III processors. The versions differed only in their interface to Time Warp. On the Butterfly, the sequential execution completed in 2 hours, while the 100 processor execution completed in 3.2 minutes. 相似文献