全文获取类型
收费全文 | 1698篇 |
免费 | 86篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 23篇 |
综合类 | 7篇 |
化学工业 | 563篇 |
金属工艺 | 36篇 |
机械仪表 | 35篇 |
建筑科学 | 111篇 |
矿业工程 | 5篇 |
能源动力 | 31篇 |
轻工业 | 106篇 |
水利工程 | 12篇 |
无线电 | 108篇 |
一般工业技术 | 322篇 |
冶金工业 | 202篇 |
原子能技术 | 3篇 |
自动化技术 | 228篇 |
出版年
2023年 | 33篇 |
2022年 | 35篇 |
2021年 | 58篇 |
2020年 | 35篇 |
2019年 | 32篇 |
2018年 | 48篇 |
2017年 | 34篇 |
2016年 | 64篇 |
2015年 | 48篇 |
2014年 | 72篇 |
2013年 | 90篇 |
2012年 | 87篇 |
2011年 | 109篇 |
2010年 | 65篇 |
2009年 | 67篇 |
2008年 | 91篇 |
2007年 | 79篇 |
2006年 | 62篇 |
2005年 | 61篇 |
2004年 | 41篇 |
2003年 | 34篇 |
2002年 | 48篇 |
2001年 | 18篇 |
2000年 | 37篇 |
1999年 | 29篇 |
1998年 | 37篇 |
1997年 | 41篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1973年 | 7篇 |
1969年 | 6篇 |
排序方式: 共有1792条查询结果,搜索用时 0 毫秒
1.
2.
Dynamics of a single fluxon in an annular Josephson junction is studied in the presence of an externally applied magnetic
field H. Due to the interaction of the fluxon with the radial field component, the fluxon moves in a potential well which
height is proportional to H. Several spectacular features of fluxon dynamics analogous to the motion of a particle in a washboard
potential are clearly observed experimentally. Periodic revolutions of the fluxon in the junction lead to a potential induced
emission of plasma waves. These waves are indicated by a resonance at a certain fluxon velocity which depends on the junction
length. Good agreement between experiment, theoretical model and numerical simulations is found. 相似文献
3.
Norbert Delatte 《Canadian Metallurgical Quarterly》2004,130(1):37-43
For the last seven years, a summer Research Experiences for Undergraduates site in structural engineering, funded by the National Science Foundation, has operated at the University of Alabama at Birmingham. During this time, 33 students from 22 colleges and universities have participated in the site. Participants are recruited nationally and have come from as far away as California and Puerto Rico. The program is intended to provide students interested in graduate studies with an introduction to research methods, and to provide students who will not continue their studies past a bachelor of science in civil engineering with a better understanding of how research provides the theoretical foundation of engineering practice. Students work individually with faculty on literature reviews, computer modeling, laboratory testing, and field research. Three students have researched structural failure case studies and the technical and ethical lessons to be learned from them. Participants also have the opportunity to tour construction sites and construction material manufacturers’ and fabricators’ facilities. During the past three years, an ethics seminar series has been added. At the end of the program, students prepare research papers and Web pages documenting their work and present their results to faculty, students, and other participants. 相似文献
4.
The variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids. 相似文献
5.
Norbert J. Kubilus 《Information Systems Management》1991,8(2):54-61
For many companies, involvement in mergers or acquisitions is quite common, Unfortunately, what is not so common is the IS department's role in preparing for the organizational changes that occur after a merger or acquisition has taken place. This article identifies some of the corporate issues and problems the IS department faces following a merger or acquisition and discusses how IS managers can best prepare for and manage the impact of such transactions on their IS departments. 相似文献
6.
Jan Haas Karen S. Frese Farbod Sedaghat-Hamedani Elham Kayvanpour Rewati Tappu Rouven Nietsch Oguz Firat Tugrul Michael Wisdom Carsten Dietrich Ali Amr Tanja Weis Torsten Niederdrnk Michael P. Murphy Thomas Krieg Marcus Drr Uwe Vlker Jens Fielitz Norbert Frey Stephan B. Felix Andreas Keller Hugo A. Katus Benjamin Meder 《International journal of molecular sciences》2021,22(4)
With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10−6). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets. 相似文献
7.
We present dynamic studies of surface reactions using video-Field Ion Microscopy (FIM) along with Pulsed Field Desorption
Mass Spectrometry (PFDMS). Catalytic water formation is followed using rhodium and platinum 3D field emitter crystals for
the oxidation of hydrogen with either oxygen (Rh) or NO (Pt). Strongly non-linear dynamics are observed with nanoscale spacial
resolution. For both reactions quasi-oscillatory behaviour exists under certain conditions of temperatures and partial pressures.
An influence of the probing electric field is observed and possibly essential in establishing oscillatory behaviour. Local
chemical probing of selected surface areas with up to 400 atomic surface sites proves catalytic water formation to take place.
Since water ions (H2O+/H3O+) cause image formation of the O2–H2 reaction on Rh, respective videos provide space-time resolved information on the catalytically active sites. Atom-probe data
also reveal that the surface of the Rh sample reversibly switches from a metallic to an oxidized state during oscillations.
As to the NO–H2 reaction on Pt, fast ignition phenomena are observed to precede wave fronts. After catalytic water formation, NO molecules
diffuse into emptied areas and cause high image brightness. Depending on the size of the Pt crystal, the reaction may ignite
in planes or kinked ledges along the <100> zone lines. Thus FIM provides clear experimental evidence that kinks are more reactive
than steps in the catalytic NO + H2 reaction. Pt surface oxidation occurs and has probably been underestimated in previous FIM studies. 相似文献
8.
9.
Significant progress has been made in recent years regarding the photooxidation of olefin copolymers, but questions still remain. This paper reviews the progress and probes the photooxidative chemistry of ethylene–propylene (EP) and ethylene/propylene/diene monomer (EPDM) copolymers. Both stabilized and unstabilized polymer plaques were irradiated in a xenon are and the surface chemistry followed using infra-red spectroscopy. Model compounds were used to help elucidate the chemistry caused by unique structural features present in the copolymers. Volatile products evolved during photooxidation were determined giving valuable insight into the degradation chemistry. 相似文献
10.
The inter-relations between iron catalysts, recycle solvent composition and product yield and composition have been investigated in bench-scale (1–2 kg h?1) continuous hydrogenation of Australian coals at process severity of 21–22 MPa at 400–430°C. Products and recycle solvent are recovered in batch distillation (atmospheric and vacuum) and the distillate solvent is returned to slurry feed without further treatment. Successive samples of recycle solvent are analysed by g.c.-m.s., i.r. and titrimetry. The effect of adding iron catalysts in the form of red mud - sulphur mixtures or compounds after a short period of continuous operation without catalyst is demonstrated. Distillate yields from black coals increase from 24–34 wt% daf under non-catalytic conditions to 35–53 wt% daf by adding iron catalysts. The composition of the almost equilibrated recycle solvent also changes and a new equilibrium is approached after the iron catalyst is added. The effect of solvent composition on distillate yield can not be determined from these data. The ratio of hydroaromatic components to hydroaromatic plus aromatic components in the solvent increases from ≈0.2 at non-catalytic equilibrium to ≈0.5–0.6 at catalysed equilibrium after adding iron. Other compositional parameters in the recycle solvent do not show any clear responses to the addition of iron. Equilibrium solvent composition under constant operating conditions is attained at ≈10 passes at 1 kg h?1 throughput with total system holdup of ≈20 kg. Paraffins for the Queensland subbituminous coal equilibrated at 18–24% in the solvent, phenolics at 16–21%, basic nitrogen at ≈0.4% (as N), and the balance a mixture of aromatics and hydroaromatics. The total aromatics neglecting phenolics in the equilibrium recycle solvent consists of ≈40–50% each of two-and three-ring and 5–10% four-ring members. 相似文献