全文获取类型
收费全文 | 1903篇 |
免费 | 113篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 50篇 |
综合类 | 3篇 |
化学工业 | 512篇 |
金属工艺 | 33篇 |
机械仪表 | 54篇 |
建筑科学 | 85篇 |
矿业工程 | 4篇 |
能源动力 | 54篇 |
轻工业 | 208篇 |
水利工程 | 21篇 |
石油天然气 | 5篇 |
无线电 | 162篇 |
一般工业技术 | 319篇 |
冶金工业 | 166篇 |
原子能技术 | 16篇 |
自动化技术 | 328篇 |
出版年
2023年 | 19篇 |
2022年 | 83篇 |
2021年 | 88篇 |
2020年 | 38篇 |
2019年 | 33篇 |
2018年 | 58篇 |
2017年 | 45篇 |
2016年 | 66篇 |
2015年 | 45篇 |
2014年 | 68篇 |
2013年 | 115篇 |
2012年 | 77篇 |
2011年 | 124篇 |
2010年 | 98篇 |
2009年 | 113篇 |
2008年 | 109篇 |
2007年 | 98篇 |
2006年 | 79篇 |
2005年 | 65篇 |
2004年 | 61篇 |
2003年 | 58篇 |
2002年 | 48篇 |
2001年 | 27篇 |
2000年 | 30篇 |
1999年 | 27篇 |
1998年 | 47篇 |
1997年 | 39篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1910年 | 2篇 |
排序方式: 共有2020条查询结果,搜索用时 15 毫秒
51.
The vortex reconnection rate f plays an important role in the dynamics of a tangle of quantised vortices in superfluid turbulence. The question which we address is how f depends on the vortex line density L. In the case of a homogeneous isotropic tangle of vortices we show that, besides the known regime which scales as f ~ L5/2, another regime exists which scales as f ~ L2. In the case of a polarised vortex confguration, we argue that the scaling law changes and show numerical evidence for it. Finally we construct an idealised model of turbulence decay based on vortex reconnections and discuss its implications. PACS numbers: 67.40.Vs, 67.57.Fg. 相似文献
52.
A mathematical model was developed to describe the in‐line hot rolling deformation and recrystallization behaviour of austenite after the solidification on a thin slab casting plant. The most significant features of the cast rolling process were taken into consideration: through‐thickness thermal gradients, inhomogeneous stress and strain, temperature discontinuity between the strip and the rolls. A HSLA (High Strength Low Alloy) steel has been chosen to perform the experiments of cast rolling. The characteristic constants ruling the microstructural evolution of that steel were computed and integrated into the computational module which manages the structural stress‐strain and strain rate computation. The developed approach is based on the Navier‐Stokes’ equations which were used to compute the speed field in the strip during the deformation. Then a model providing a proper constitutive equation was structured on the basis of the Yada's model based on evolution of the dislocation populations. The use of the Navier‐Stokes’ formalism allows to reach the resolution of the structural problem from the data measured easily during the industrial practice (i.e. speed of the rolled product at the entry and at the exit of a stand, the temperature of the rolled material). The validation of this computational approach was obtained by a comparison between the prior austenite grain size of the strip in different positions of the hot rolling process, as well as by a comparison between the computed deformation power and the measured one provided by the engines moving the rolls. 相似文献
53.
Pedersoli E Capotondi F Cocco D Zangrando M Kaulich B Menk RH Locatelli A Mentes TO Spezzani C Sandrin G Bacescu DM Kiskinova M Bajt S Barthelmess M Barty A Schulz J Gumprecht L Chapman HN Nelson AJ Frank M Pivovaroff MJ Woods BW Bogan MJ Hajdu J 《The Review of scientific instruments》2011,82(4):043711
We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi@Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi@Elettra free electron laser in 2011. 相似文献
54.
Shasha Zhang Carlo Badiola Mirko Schoenitz Edward L. Dreizin 《Combustion and Flame》2012,159(5):1980-1986
Materials combining high energy density of metals with the biocidal activity of halogens are of interest for applications aiming to inactivate harmful aerosolized microorganisms by combined thermal and chemical effects. This effort develops nanocomposite Al-halogen materials to replace pure Al as a fuel additive in energetic formulations. Cryogenic milling of elemental aluminum and iodine is used to prepare powder-like composite materials for laboratory tests. In such materials, iodine is stabilized in aluminum matrix and is released when the materials are heated and ignited. Al·I2 composite powders with the iodine concentration from 10 to 30 wt.% were prepared. Iodine release by and oxidation of such materials were investigated using thermo-gravimetric analysis. Ignition temperatures of the prepared powders were determined at the heating rates of 1000–22,000 K/s using an electrically heated filament. Composite powders ignite at lower temperatures compared to pure Al powders. Combustion characteristics of the prepared materials were investigated using a constant volume explosion test for aerosolized powders and laser ignition test for individual particles. In both combustion experiments pure Al served as a reference. Higher combustion rate and greater total pressure were observed for the aerosolized clouds of composite powders with 15 and 20 wt.% of iodine. For individual particles, the burn times were slightly longer and flame temperatures were slightly lower compared to those of pure aluminum. Both overall iodine concentration and its stability in the composite powders affected their ignition and combustion characteristics. 相似文献
55.
Jeppe Rich Carlo Giacomo PratoTove Hels Allan LyckegaardNiels Buus Kristensen 《Accident; analysis and prevention》2013
While the number of fatalities on Danish roads has decreased in the last 40 years, research has not investigated the contribution of legislation changes, enforcement measures, technological enhancements, infrastructural improvements and human factors to this reduction. In the context of a Danish car market with remarkably high registration tax that causes potential buyers to hold longer onto old cars, the relationship between technological enhancements of vehicles and severity of crashes requires particular attention. 相似文献
56.
Patrizia Proia Carlo Maria Di Liegro Gabriella Schiera Anna Fricano Italia Di Liegro 《International journal of molecular sciences》2016,17(9)
More than two hundred years after its discovery, lactate still remains an intriguing molecule. Considered for a long time as a waste product of metabolism and the culprit behind muscular fatigue, it was then recognized as an important fuel for many cells. In particular, in the nervous system, it has been proposed that lactate, released by astrocytes in response to neuronal activation, is taken up by neurons, oxidized to pyruvate and used for synthesizing acetyl-CoA to be used for the tricarboxylic acid cycle. More recently, in addition to this metabolic role, the discovery of a specific receptor prompted a reconsideration of its role, and lactate is now seen as a sort of hormone, even involved in processes as complex as memory formation and neuroprotection. As a matter of fact, exercise offers many benefits for our organisms, and seems to delay brain aging and neurodegeneration. Now, exercise induces the production and release of lactate into the blood which can reach the liver, the heart, and also the brain. Can lactate be a beneficial molecule produced during exercise, and offer neuroprotection? In this review, we summarize what we have known on lactate, discussing the roles that have been attributed to this molecule over time. 相似文献
57.
Arrays of precisely positioned single crystal silicon nanopillars, nanoneedles, and nanoblades with minimum feature sizes as small as 30 nm are fabricated using entirely scalable top-down fabrication techniques. Using the same scalable technologies, devices consisting of electrically connected silicon nanopillars with multiple addressable electrodes for each nanostructure are realized. The arrays of nanopillars, nanoneedles, and nanoblades are shown to exhibit Raman signal enhancement on 1,2-benzenedithiol monolayers, opening a path to nanodevices that manipulate, position, detect and analyze molecules. 相似文献
58.
Christoph Beierle Carlo Meghini 《Annals of Mathematics and Artificial Intelligence》2016,76(3-4):247-249
59.
Antonella Ilenia Alfano Prof. Elisabetta Buommino Prof. Maria Grazia Ferraro Prof. Carlo Irace Prof. Angela Zampella Prof. Heiko Lange Prof. Margherita Brindisi 《ChemMedChem》2021,16(24):3795-3809
The generation of peptidomimetic substructures for medicinal chemistry purposes requires effective and divergent synthetic methods. We present in this work an efficient flow process that allows quick modulation of reagents for Joullié-Ugi multicomponent reaction, using spiroindolenines as core motifs. This sterically hindered imine equivalent could successfully be diversified using various isocyanides and amino acids in generally good space-time yields. A telescoped flow process combining interrupted Fischer reaction for spiroindolenine synthesis and subsequent Joullié-Ugi-type modification resulted in product formation in very good overall yield in less than 2 hours compared to 48 hours required in batch mode. The developed protocol can be seen as a general tool for rapid and facile generation of peptidomimetic compounds. We also showcase preliminary biological assessments for the prepared compounds. 相似文献
60.
Giordana Feriotto Federico Tagliati Riccardo Giriolo Fabio Casciano Claudio Tabolacci Simone Beninati Mahmud Tareq Hassan Khan Carlo Mischiati 《International journal of molecular sciences》2021,22(4)
Among the phenolic acids tested on the K562 cell line, a model of chronic myeloid leukemia (CML), caffeic acid (CA) was biologically active on sensitive and imatinib (IM)-resistant cells at micro-molar concentration, either in terms of reduction of cell proliferation or triggering of apoptosis. The CA treatment provoked mitochondrial membrane depolarization, genomic DNA fragmentation and phosphatidylserine exposure, hallmarks of apoptosis. Cell cycle analysis following the treatment with comparable cytotoxic concentrations of IM or CA showed marked differences in the distribution profiles. The reduction of cell proliferation by CA administration was associated with increased expression of two cell cycle repressor genes, CDKN1A and CHES1, while IM at a cytotoxic concentration increased the CHES1 but not the CDKN1A expression. In addition, CA treatment affected the proliferation and triggered the apoptosis in IM-resistant cells. Taken together, these data suggested that CA induced the anti-proliferative effect and triggered apoptosis of CML cells by a different mechanism than IM. Finally, the combined administration of IM and CA at suboptimal concentrations evidenced a synergy of action in determining the anti-proliferative effect and triggering apoptosis. The ability of CA to potentiate the anti-leukemic effect of IM highlighted the nutraceutical potential of CA in CML. 相似文献