全文获取类型
收费全文 | 886篇 |
免费 | 62篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 496篇 |
金属工艺 | 19篇 |
机械仪表 | 6篇 |
建筑科学 | 21篇 |
矿业工程 | 9篇 |
能源动力 | 32篇 |
轻工业 | 159篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 16篇 |
一般工业技术 | 94篇 |
冶金工业 | 11篇 |
原子能技术 | 1篇 |
自动化技术 | 70篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 104篇 |
2021年 | 139篇 |
2020年 | 28篇 |
2019年 | 43篇 |
2018年 | 24篇 |
2017年 | 31篇 |
2016年 | 36篇 |
2015年 | 39篇 |
2014年 | 51篇 |
2013年 | 46篇 |
2012年 | 51篇 |
2011年 | 61篇 |
2010年 | 32篇 |
2009年 | 25篇 |
2008年 | 31篇 |
2007年 | 27篇 |
2006年 | 31篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有948条查询结果,搜索用时 46 毫秒
681.
The results of heavy metals (Fe, Mn, Zn, Ni, Cu, Cr, Pb, Cd) removal and partitioning between aqueous and solid phases at two treatment wetlands (TWs) treating municipal landfill leachates are presented. One of the TWs is a surface flow facility consisting of 10 ponds. The other TW is a newly constructed pilot-scale facility consisting of three beds with alternately vertical and horizontal subsurface flow. The metals concentrations were analysed in leachate (both TWs) and bottom sediments (surface flow TW). Very high (90.9-99.9%) removal rates of metals were observed in a mature surface flow TW. The effectiveness of metals removal in a newly constructed pilot-scale sub-surface flow wetland were considerably lower (range 0-73%). This is attributed to young age of the TW, different hydraulic conditions (sub-surface flow system with much shorter retention time, unoxic conditions) and presence of metallic complexes with refractory organic matter. 相似文献
682.
De Stasio G Frazer BH Girasole M Wiese LM Krasnowska EK Greco G Serafino A Parasassi T 《Microscopy research and technique》2004,63(2):115-121
Established microscopies such as Scanning Electron Microscopy (SEM) and more recent developments such as Atomic Force Microscopy (AFM) and X-ray Photo-Electron Emission spectroMicroscopy (X-PEEM) can only image the sample surface. We present an argon sputtering method able to progressively expose inner cell structures without apparent damage. By varying the sputtering time, the structure of cell cytoskeleton, vesicles, mitochondria, nuclear membrane, and nucleoli can be imaged. We compared images obtained with confocal fluorescence microscopy, transmission electron microscopy (TEM), SEM, and X-PEEM on similar samples after argon sputtering, then confirmed the similarity of reference intracellular structures, including cytoskeleton fibers, cell-cell and cell-substrate adhesion structures, and secretory vesicles. We conclude that the sputtering method is a new valuable tool for surface sensitive microscopies. 相似文献
683.
This paper presents positron lifetime studies of the subsurface region in aluminium-based alloys 2017A and 6101A, the surfaces of which were exposed to dry sliding. In the case of the 2017A alloy, the total range of the subsurface zone below the worn surface detected using the positron annihilation technique was larger than 120 μm and this value was hardly affected by load and sliding distance. For the 6101A alloy, the subsurface zone ranged from 30 to 500 μm and depended on the applied load and only to some extent on the sliding distance. The obtained results are significantly different from the results achieved for pure aluminium, thus alloying has considerable effect on the subsurface zone formation. The positron lifetime depth distribution characterizing the subsurface zone was correlated with the microhardness profile. 相似文献
684.
685.
686.
The leader–following consensus problem of fractional-order multi-agent discrete-time systems is considered. In the systems, interactions between opinions are defined like in Krause and Cucker–Smale models but the memory is included by taking the fractional-order discrete-time operator on the left-hand side of the nonlinear systems. In this paper, we investigate fractional-order models of opinions for the single- and double-summator dynamics of discrete-time by analytical methods as well as by computer simulations. The necessary and sufficient conditions for the leader–following consensus are formulated by proposing a consensus control law for tracking the virtual leader. 相似文献
687.
The h‐Difference Approach to Controllability and Observability of Fractional Linear Systems with Caputo–Type Operator 下载免费PDF全文
In the paper a class of h‐difference linear control systems with n fractional orders is studied. The Caputo‐type h‐difference operator is used. The formula of the solution to the stated initial value problem of the given system is proved. The problems of controllability and observability in a finite number of steps of h‐difference linear control systems with n fractional orders are studied. 相似文献
688.
Service replication is an effective way to address resource requirements and resource availability problem. Dynamic service
selection enables clients to choose a server offering the best performance. Proper server selection is especially important
for video streaming over the Internet due to its high bandwidth requirements. However, given the length of a typical video
transmission, the server priorly selected may no longer be an optimal one for the duration of the entire transmission. More
importantly, a server may fail during the transmission of a video. In this paper we examine the possibility of switching to
another server during an on-going transmission for Periodic Broadcast schemes. Due to the timing requirements typical for
Periodic Broadcast the server switch may cause playback disruptions. We analyze the magnitude of the problem and propose an
easy to implement solution. We define the criteria, additional to the bandwidth availability for example, according to which
a new server should be selected. The client is also required to delay its playback by the amount of time bounded by the server
transmission offset. In addition, we propose an alternative method to ensure uninterrupted playback that relies on proxy caching.
Simulation results show that our approach can significantly reduce the likelihood of playback disruptions.
相似文献
David H. C. DuEmail: |
689.
A comparative analysis of the results for the estimation of the pore-size distribution based on the methods of Do and co-workers (ND) and density functional theory (DFT) is given. A new algorithm (ASA, Adsorption Stochastic Algorithm) is adopted and it is shown that this algorithm can be successfully applied for the determination of the PSD curve from the ND method. The obtained results show that, generally, the ND and DFT methods lead to almost the same PSD curves and this similarity is observed for carbons of different origin and possessing different pore structures. However, if the contribution of micropores to the PSD increases, the differences in the fit of ND and DFT to the experimental data are more pronounced. 相似文献
690.
Expression of lyso paf-acether (lyso paf):acetyl-CoA acetyltransferase and its activation above basal levels by specific agonists
controls the rate of paf biosynthesis in proinflammatory cells. Acetyltransferase activation in these cells is due to the
rapid postranslational modification of an inactive precursor by phosphorylation, most probably catalyzed by a cAMP-dependent
kinase. However, the possibility exists that a calcium/calmodulin-dependent kinase can be implicated as well. Unlike murine
cultured mast cells, human neutrophils form paf when stimulated with phorbol myristate acetate (PMA) or diacylglycerol. In
both cell types, acetyltransferase is activated by PMA. Controversy exists as to whether PMA activates the remodeling pathway,i.e. the activation of phospholipase A2 and acetyltransferase, or thede novo route through CDPcholine cholinephosphotransferase action on alkylacetylglycerol. There is some indication that PKC might
regulate paf biosynthesis. The implication of a GTP-regulated protein has also been postulated in signal transduction leading
to paf formation in endothelial cells, neutrophils, and mast cells. The topography of paf formation is discussed in light
of the subcellular distribution of acetyltransferase in neutrophils and Krebs II cells.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献