全文获取类型
收费全文 | 2239篇 |
免费 | 36篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 161篇 |
金属工艺 | 15篇 |
机械仪表 | 12篇 |
建筑科学 | 22篇 |
矿业工程 | 2篇 |
能源动力 | 21篇 |
轻工业 | 103篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 107篇 |
一般工业技术 | 100篇 |
冶金工业 | 1597篇 |
原子能技术 | 6篇 |
自动化技术 | 95篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 20篇 |
2016年 | 8篇 |
2015年 | 18篇 |
2014年 | 31篇 |
2013年 | 50篇 |
2012年 | 22篇 |
2011年 | 32篇 |
2010年 | 27篇 |
2009年 | 46篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 26篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 14篇 |
1999年 | 60篇 |
1998年 | 570篇 |
1997年 | 287篇 |
1996年 | 200篇 |
1995年 | 115篇 |
1994年 | 85篇 |
1993年 | 87篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 40篇 |
1976年 | 62篇 |
1975年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有2277条查询结果,搜索用时 109 毫秒
51.
Juan Gutierrez-Aguado Jose M. Alcaraz Calero Wladimiro Diaz Villanueva 《Journal of Grid Computing》2016,14(2):283-297
Monitoring of cloud computing infrastructures is an imperative necessity for cloud providers and administrators to analyze, optimize and discover what is happening in their own infrastructures. Current monitoring solutions do not fit well for this purpose mainly due to the incredible set of new requirements imposed by the particular requirements associated to cloud infrastructures. This paper describes in detail the main reasons why current monitoring solutions do not work well. Also, it provides an innovative monitoring architecture that enables the monitoring of the physical and virtual machines available within a cloud infrastructure in a non-invasive and transparent way making it suitable not only for private cloud computing but also for public cloud computing infrastructures. This architecture has been validated by means of a prototype integrating an existing enterprise-class monitoring solution, Nagios, with the control and data planes of OpenStack, a well-known stack for cloud infrastructures. As a result, our new monitoring architecture is able to extend the exiting Nagios functionalities to fit in the monitoring of cloud infrastructures. The proposed architecture has been designed, implemented and released as open source to the scientific community. The proposal has also been empirically validated in a production-level cloud computing infrastructure running a test bed with up to 128 VMs where overhead and responsiveness has been carefully analyzed. 相似文献
52.
Frank-Michael Schleif Mathias Lindemann Mario Diaz Peter Maaß Jens Decker Thomas Elssner Michael Kuhn Herbert Thiele 《Computing and Visualization in Science》2009,12(4):189-199
Automatic classification of high-resolution mass spectrometry data has increasing potential to support physicians in diagnosis of diseases like cancer. The proteomic data exhibit variations among different disease states. A precise and reliable classification of mass spectra is essential for a successful diagnosis and treatment. The underlying process to obtain such reliable classification results is a crucial point. In this paper such a method is explained and a corresponding semi automatic parameterization procedure is derived. Thereby a simple straightforward classification procedure to assign mass spectra to a particular disease state is derived. The method is based on an initial preprocessing stage of the whole set of spectra followed by the bi-orthogonal discrete wavelet transform (DWT) for feature extraction. The approximation coefficients calculated from the scaling function exhibit a high peak pattern matching property and feature a denoising of the spectrum. The discriminating coefficients, selected by the Kolmogorov–Smirnov test are finally used as features for training and testing a support vector machine with both a linear and a radial basis kernel. For comparison the peak areas obtained with the it ClinProt-System 1 [33] were analyzed using the same support vector machines. The introduced approach was evaluated on clinical MALDI-MS data sets with two classes each originating from cancer studies. The cross validated error rates using the wavelet coefficients where better than those obtained from the peak areas2. 相似文献
53.
Viscoelastic material design with negative stiffness components using topology optimization 总被引:1,自引:1,他引:0
An application of topology optimization to design viscoelastic composite materials with elastic moduli that soften with frequency
is presented. The material is a two-phase composite whose first constituent is isotropic and viscoelastic while the other
is an orthotropic material with negative stiffness but stable. A concept for this material based on a lumped parameter model
is used. The performance of the topology optimization approach in this context is illustrated using three examples. 相似文献
54.
This paper introduces time stream Pétri nets (Ts treamPn), a model for the formal specification of multimedia synchronization scenarios. This new model extends time Pétri nets to formally describe the timed behaviour of multimedia objects and streams in asynchronous distributed systems. The proposed approach uses time intervals to label the arcs exiting from the places of the net, and typed transitions to define different firing rules. This model allows a complete and accurate specification of synchronization constraints between multimedia streams and can be used at different levels of granularity. 相似文献
55.
Rafael Diaz 《国际生产研究杂志》2016,54(8):2487-2498
The warehouse order-picking operation is one of the most labour-intense activities that has an important impact on responsiveness and efficiency of the supply chain. An understanding of the impact of the simultaneous effects of customer demand patterns and order clustering, considering physical restrictions in product storage, is critical for improving operational performance. Storage restrictions may include storing non-uniform density stock keeping units (SKUs) whose dimensions and weight constrain the order-picking operation given that a priority must be followed. In this paper, a heuristic optimisation based on a quadratic integer programming is employed to generate a layout solution that considers customer demand patterns and order clustering. A simulation model is used to investigate the effects of creating and implementing these layout solutions in conjunction with density zones to account for restrictions in non-uniform density SKUs. Results from combining layout optimisation heuristics and density zoning indicate statistical significant differences between assignments that ignore the aforementioned factors and those that recognise it. 相似文献
56.
Helge Klippstein Hany Hassanin Alejandro Diaz De Cerio Sanchez Yahya Zweiri Lakmal Seneviratne 《Advanced Engineering Materials》2018,20(9)
57.
Superantigens stimulate T-lymphocyte proliferation and cytokine production, but the effects of superantigen exposure on cell function within a complex, highly regulated immune response remain to be determined. In this study, we demonstrate that superantigen exposure significantly alters the murine host response to bacterial antigens in an in vitro coculture system. Two days after exposure to the superantigen staphylococcal enterotoxin B, splenocytes cultured with Streptococcus mutans produced significantly greater amounts of gamma interferon (IFN-gamma) and interleukin-12 than did sham-injected controls. The majority of IFN-gamma production appeared to be CD8(+) T-cell derived since depletion of this cell type dramatically reduced the levels of IFN-gamma. To study host cell damage that may occur following superantigen exposure, we analyzed cytotoxicity to "bystander" fibroblast cells cultured with splenocytes in the presence of bacterial antigens. Prior host exposure to staphylococcal enterotoxin B significantly enhanced fibroblast cytotoxicity in the presence of bacteria. Neutralization of IFN-gamma decreased the amount of cytotoxicity observed. However, a greater reduction was evident when splenocyte-bacterium cocultures were separated from the bystander cell monolayer via a permeable membrane support. Increased cytotoxicity appears to be primarily dependent upon cell-cell contact. Collectively, these data indicate that overproduction of inflammatory cytokines may alter the activity of cytotoxic immune cells. Superantigen exposure exacerbates cytokine production and lytic cell activity when immune cells encounter bacteria in vitro and comparable activities could possibly occur in vivo. 相似文献
58.
M Tahara JR Coorssen K Timmers PS Blank T Whalley R Scheller J Zimmerberg 《Canadian Metallurgical Quarterly》1998,273(50):33667-33673
The homotypic fusion of sea urchin egg cortical vesicles (CV) is a system in which to correlate the biochemistry and physiology of membrane fusion. Homologues of vesicle-associated membrane protein (VAMP), syntaxin, and SNAP-25 were identified in CV membranes. A VAMP and syntaxin immunoreactive band at a higher apparent molecular mass (approximately 70 kDa) was detected; extraction and analysis confirmed that the band contained VAMP, SNAP-25, and syntaxin. This complex was also identified by immunoprecipitation and by sucrose gradient analysis. VAMP in the complex was insensitive to proteolysis by tetanus toxin. All criteria identify the SNARE complex as that described in other secretory systems. Complexes exist pre-formed on individual CV membranes and form between contacting CV. Most notably, CV SNARE complexes are disrupted in response to [Ca2+]free that trigger maximal fusion. N-Ethylmaleimide, which blocks fusion at or before the Ca2+-triggering step, blocks complex disruption by Ca2+. However, disruption is not blocked by lysophosphatidylcholine, which transiently arrests a late stage of fusion. Since removal of lysophosphatidylcholine from Ca2+-treated CV is known to allow fusion, complex disruption occurs independently from the membrane fusion step. As Ca2+ disrupts rather than stabilizes the complex, the presumably coiled-coil SNARE interactions are not needed at the time of fusion. These findings rule out models of fusion in which SNARE complex formation goes to completion ("zippers-up") after Ca2+ binding removes a "fusion-clamp." 相似文献
59.
PS Estes J Roos A van der Bliek RB Kelly KS Krishnan M Ramaswami 《Canadian Metallurgical Quarterly》1996,16(17):5443-5456
Presynaptic terminals contain several specialized compartments, which have been described by electron microscopy. We show in an identified Drosophila neuromuscular synapse that several of these compartments-synaptic vesicle clusters, presynaptic plasma membrane, presynaptic cytosol, and axonal cytoskeleton-labeled by specific reagents may be resolved from one another by laser scanning confocal microscopy. Using a panel of compartment-specific markers and Drosophila shibire(ts1) mutants to trap an intermediate stage in synaptic vesicle recycling, we have examined the localization and redistribution of dynamin within single synaptic varicosities at the larval neuromuscular junction. Our results suggest that dynamin is not a freely diffusible molecule in resting nerve terminals; rather, it appears localized to synaptic sites by association with yet uncharacterized presynaptic components. In shi(ts1) nerve terminals depleted of synaptic vesicles, dynamin is quantitatively redistributed to the plasma membrane. It is not, however, distributed uniformly over presynaptic plasmalemma; instead, fluorescence images show "hot spots" of dynamin on the plasma membrane of vesicle-depleted nerve terminals. We suggest that these dynamin-rich domains may mark the active zones for synaptic vesicle endocytosis first described at the frog neuromuscular junction. 相似文献
60.
J Murcia J Vazquez SM Lopez M Gamez L Hierro C Camarena A de la Vega E Frauca MC Diaz P Jara J Tovar 《Canadian Metallurgical Quarterly》1996,6(3):152-154
BACKGROUND: Biological systems that show threshold phenomena are candidates for stochastic resonance as a mechanism to explain what appears to be biovariability. Stochastic resonance is the amplification of weak signals by "noise." OBJECTIVE: This review discusses the areas of contact dermatitis in which threshold events have been documented. The purpose is to point out the mechanism by which stochastic resonance may affect patch test results. METHODS: A literature review technique was used. RESULTS: The recent finding of a neurological influence on contract dermatitis provides a mechanism for stochastic resonance to affect patch test results. CONCLUSION: Stochastic resonance is likely to affect patch test results when more than one patch test result is positive. 相似文献