全文获取类型
收费全文 | 2386篇 |
免费 | 48篇 |
专业分类
电工技术 | 30篇 |
综合类 | 4篇 |
化学工业 | 280篇 |
金属工艺 | 25篇 |
机械仪表 | 35篇 |
建筑科学 | 81篇 |
矿业工程 | 5篇 |
能源动力 | 30篇 |
轻工业 | 85篇 |
水利工程 | 36篇 |
石油天然气 | 1篇 |
无线电 | 233篇 |
一般工业技术 | 325篇 |
冶金工业 | 1073篇 |
原子能技术 | 22篇 |
自动化技术 | 169篇 |
出版年
2022年 | 18篇 |
2021年 | 26篇 |
2019年 | 14篇 |
2018年 | 23篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 23篇 |
2014年 | 27篇 |
2013年 | 56篇 |
2012年 | 45篇 |
2011年 | 72篇 |
2010年 | 50篇 |
2009年 | 53篇 |
2008年 | 71篇 |
2007年 | 66篇 |
2006年 | 63篇 |
2005年 | 45篇 |
2004年 | 59篇 |
2003年 | 52篇 |
2002年 | 39篇 |
2001年 | 42篇 |
2000年 | 52篇 |
1999年 | 59篇 |
1998年 | 296篇 |
1997年 | 191篇 |
1996年 | 136篇 |
1995年 | 95篇 |
1994年 | 67篇 |
1993年 | 72篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 31篇 |
1989年 | 29篇 |
1988年 | 17篇 |
1987年 | 30篇 |
1986年 | 31篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1977年 | 37篇 |
1976年 | 75篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1971年 | 13篇 |
排序方式: 共有2434条查询结果,搜索用时 31 毫秒
81.
In response to the increasing trend toward community health care, a model of training that prepares students for community practice was incorporated into the occupational therapy curriculum at the University of Southern California. During academic training students are placed in a part-time community assignment where no occupational therapy services are offered. Training students for the role of community health specialist produces a dilemma for curriculum design. A balance must be achieved between providing traditional clinical content and providing the knowledge and expertise necessary for community practice. However, this training is considered necessary for maintaining the viability of the profession in a changing health system. Significantly, during the four-year period using this model, many graduates have sought employment in "nontraditional" community roles. 相似文献
82.
Rainer Keller Edgar Gabriel Bettina Krammer Matthias S. Müller Michael M. Resch 《Journal of Grid Computing》2003,1(2):133-149
The message passing interface (MPI) is a standard used by many parallel scientific applications. It offers the advantage of a smoother migration path for porting applications from high performance computing systems to the Grid. In this paper Grid-enabled tools and libraries for developing MPI applications are presented. The first is MARMOT, a tool that checks the adherence of an application to the MPI standard. The second is PACX-MPI, an implementation of the MPI standard optimized for Grid environments. Besides the efficient development of the program, an optimal execution is of paramount importance for most scientific applications. We therefore discuss not only performance on the level of the MPI library, but also several application specific optimizations, e.g., for a sparse, parallel equation solver and an RNA folding code, like latency hiding, prefetching, caching and topology-aware algorithms. 相似文献
83.
A. Persaud S. J. Park J. A. Liddle I. W. Rangelow J. Bokor R. Keller F. I. Allen D. H. Schneider T. Schenkel 《Quantum Information Processing》2004,3(1-5):233-245
Spins of single donor atoms are attractive candidates for large scale quantum information processing in silicon. Formation of devices with a few qubits is crucial for validation of basic ideas and development of a scalable architecture. We describe our development of a single ion implantation technique for placement of single atoms into device structures. Collimated highly charged ion beams are aligned with a scanning probe microscope. Enhanced secondary electron emission due tohigh ion charge states (e.g., 31P13+, or 126Te33+)allows efficient detection of single ion impacts. Studies of electrical activation of low dose, low energy implants of 31P in silicon show a drastic effect of dopant segregation to the SiO2/Si interface,while Si3N4/Si retards 31P segregation. We discuss resolution limiting factors in ion placement, and process challenges forintegration of single atom arrays with control gates and single electron transistors.
PACS: 03.67.Lx, 34.50.Dy, 85.35.Gv, 73.23, 61.72, 86.40.py, 07.79.-v 相似文献
84.
In sheep, recognition of the familiar lamb by the mother depends on the learning of its olfactory signature after parturition. The authors quantified Fos changes in order to identify brain regions activated during lamb odor memory formation. Brain activation was compared with those measured in anosmic ewes displaying maternal behavior but not individual lamb recognition. In intact ewes, parturition induced significant increase in Fos expression in olfactory cortical regions and in cortical amygdala, whereas in anosmic mothers, Fos expression was very low. In contrast, no difference was observed between intact and anosmic ewes in hypothalamic areas and medial amygdala, suggesting a differentiation between the neural network controlling maternal responsiveness and that involved in olfactory lamb memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
The ability to visualize cell motility occurring deep in the context of opaque tissues will allow many currently intractable issues in developmental biology and organogenesis to be addressed. In this study, we compare two-photon excitation with laser scanning confocal and conventional digital deconvolution fluorescence microscopy, using the same optical configuration, for their ability to resolve cell shape deep in Xenopus gastrula and neurula tissues. The two-photon microscope offers better depth penetration and less autofluorescence compared to confocal and conventional deconvolution imaging. Both two-photon excitation and confocal microscopy also provide improved rejection of "out-of-focus" noise and better lateral and axial resolution than conventional digital deconvolution microscopy. Deep Xenopus cells are best resolved by applying the digital deconvolution method on the two-photon images. We have also found that the two-photon has better depth penetration without any degradation in the image quality of interior sections compared to the other two techniques. Also, we have demonstrated that the quality of the image changes at different depths for various excitation powers. 相似文献
86.
C. Hassel K. Blaum T. Day Goodacre H. Dorrer Ch. E. Düllmann K. Eberhardt S. Eliseev C. Enss P. Filianin A. Fäßler A. Fleischmann L. Gastaldo M. Goncharov D. Hengstler J. Jochum K. Johnston M. Keller S. Kempf T. Kieck U. Köster M. Krantz B. Marsh C. Mokry Yu. N. Novikov P. C. O. Ranitzsch S. Rothe A. Rischka J. Runke A. Saenz F. Schneider S. Scholl R. X. Schüssler F. Simkovic T. Stora P. Thörle-Pospiech A. Türler M. Veinhard M. Wegner K. Wendt K. Zuber 《Journal of Low Temperature Physics》2016,184(3-4):910-921
87.
B. Nagy Y. N. Khaydukov L. F. Kiss S. Sajti D. G. Merkel F. Tanczikó A. S. Vasenko R. O. Tsaregorodsev A. Rühm T. Keller L. Bottyán 《Journal of Superconductivity and Novel Magnetism》2013,26(5):1957-1961
The thickness (d F) and concentration (x) dependence of the Curie temperature of Ni x Cu1?x (d F) ferromagnetic alloy layers (x=0.55, 0.65, d F=[4.5 nm÷12 nm]) in contact with a vanadium layer was studied. The Curie temperature of the ferromagnetic layers depends on the thickness when it is comparable with the transition layer between the F and the vanadium layers, which is attributed to the proximity coupling of the interface region with the rest of the F layer. The present study provides valuable information for fabrication of samples with controlled exchange coupling strength for studies of superconductor/ferromagnet proximity effects. 相似文献
88.
Jessica Jones Schonna Manning Morela Montoya Karin Keller Martin Poenie 《Journal of the American Oil Chemists' Society》2012,89(8):1371-1381
Algae are a promising source of biofuel but claims about their lipid content can be ambiguous because extraction methods vary and lipid quantitation often does not distinguish between particular lipid classes. Here we compared methods for the extraction of algal lipids and showed that 2-ethoxyethanol (2-EE) provides superior lipid recovery (>150–200 %) compared to other common extraction solvents such as chloroform:methanol or hexane. Extractions of wet and dry algal biomass showed that 2-EE was more effective at extracting lipids from wet rather than dried algal pellets. To analyze lipid content we used normal-phase HPLC with parallel quantitation by an evaporative light scattering detector and a mass spectrometer. Analysis of crude lipid extracts showed that all major lipid classes could be identified and quantified and revealed a surprisingly large amount of saturated hydrocarbons (HC). This HC fraction was isolated from extracts of bioreactor-grown algae and further analyzed by HPLC/MS, NMR, and GC/MS. The results showed that the sample consisted of a mixture of saturated, straight- and branched-chain HC of different chain lengths. These algal HC could represent an alternative biofuel to triacylglycerols (TAG) that could feed directly into the current petroleum infrastructure. 相似文献
89.
Hydrogels of poly(n-vinyl-2-pyrrolidone) were produced by UV irradiation of aqueous solutions of the polymer in presence of hydrogen peroxide, used as initiator. The mechanical and the nanostructural properties of the gels were characterized by a combination of experimental techniques including rheology, low field nuclear magnetic resonance spectroscopy (LF-NMR), and small angle X-ray scattering. Different irradiation doses as well as polymer and initiator concentrations were tested in the characterization. The study elucidates the relationship between different methods to estimate the mesh size of the gel polymeric network. Moreover, a novel correlation model was developed based on Chui and Scherer theories for the interpretation of LF-NMR dataset of polymer solutions and networks. 相似文献
90.
Sethuraman Latha Vijayakumar Ganesh Ananthan Shreyas Paranthaman M. Parans Keller Jonathan King Ryan 《Forschung im Ingenieurwesen》2021,85(2):287-311
Forschung im Ingenieurwesen - Direct-drive wind turbine generators are increasing in popularity, thanks to recent project developments—especially offshore, where reliability and efficiency... 相似文献