全文获取类型
收费全文 | 3382篇 |
免费 | 71篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 50篇 |
综合类 | 1篇 |
化学工业 | 527篇 |
金属工艺 | 31篇 |
机械仪表 | 56篇 |
建筑科学 | 148篇 |
矿业工程 | 5篇 |
能源动力 | 74篇 |
轻工业 | 282篇 |
水利工程 | 22篇 |
石油天然气 | 8篇 |
无线电 | 374篇 |
一般工业技术 | 489篇 |
冶金工业 | 1044篇 |
原子能技术 | 40篇 |
自动化技术 | 305篇 |
出版年
2021年 | 36篇 |
2019年 | 30篇 |
2018年 | 32篇 |
2017年 | 38篇 |
2016年 | 36篇 |
2015年 | 30篇 |
2014年 | 55篇 |
2013年 | 110篇 |
2012年 | 68篇 |
2011年 | 118篇 |
2010年 | 77篇 |
2009年 | 89篇 |
2008年 | 89篇 |
2007年 | 105篇 |
2006年 | 103篇 |
2005年 | 80篇 |
2004年 | 63篇 |
2003年 | 65篇 |
2002年 | 56篇 |
2001年 | 62篇 |
2000年 | 62篇 |
1999年 | 76篇 |
1998年 | 308篇 |
1997年 | 192篇 |
1996年 | 144篇 |
1995年 | 99篇 |
1994年 | 85篇 |
1993年 | 77篇 |
1992年 | 48篇 |
1991年 | 50篇 |
1990年 | 57篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 40篇 |
1986年 | 41篇 |
1985年 | 47篇 |
1984年 | 46篇 |
1983年 | 42篇 |
1982年 | 25篇 |
1981年 | 27篇 |
1980年 | 38篇 |
1979年 | 36篇 |
1978年 | 31篇 |
1977年 | 47篇 |
1976年 | 71篇 |
1975年 | 33篇 |
1974年 | 37篇 |
1973年 | 28篇 |
1971年 | 35篇 |
1970年 | 24篇 |
排序方式: 共有3456条查询结果,搜索用时 15 毫秒
31.
32.
33.
Ashwin Kumar Vutha Benyamin Davaji Chung Hoon Lee Glenn M. Walker 《Microfluidics and nanofluidics》2014,17(5):871-878
We demonstrate the use of heat to count microscopic particles. A thermal particle detector (TPD) was fabricated by combining a 500-nm-thick silicon nitride membrane containing a thin-film resistive temperature detector with a silicone elastomer microchannel. Particles with diameters of 90 and 200 μm created relative temperature changes of 0.11 and ?0.44 K, respectively, as they flowed by the sensor. A first-order lumped thermal model was developed to predict the temperature changes. Multiple particles were counted in series to demonstrate the utility of the TPD as a particle counter. 相似文献
34.
The characterization of carbon surface activity in the absence of gasification was attempted using oxygen isotope exchange in CO2 over spectroscopically pure natural graphite, the surface activity being characterized by the rate of approach to isotopic equilibrium. The probable mechanism of exchange is via the first step in the carbon-CO2 reaction, the dissociation of CO2 over a carbon free site: . Assuming this mechanism to hold for isotopic exchange, the theoretical rate equation was derived. The rate constants i1, and j1, were obtained from previous studies. Theoretical calculations show that the exchange rate is negligible over natural graphite at temperatures much below gasification conditions. Experimental verification of the theoretical analysis was not possible due to the activity of the quartz boat, holding the graphite, for catalyzing the exchange reaction. The exchange reaction was successfully followed over the Pt and CaO supported on a graphitized carbon black, in which case the activity was much, much greater than that ovgr the empty quartz boat. 相似文献
35.
Lesa Lorenzen Huber Kalpana Shankar Kelly Caine Kay Connelly L. Jean Camp Beth Ann Walker 《International journal of human-computer interaction》2013,29(7):441-455
In-home technologies can support older adults' activities of daily living, provide physical safety and security, and connect elders to family and friends. They facilitate aging in place while reducing caregiver burden. One of older adults' primary concerns about in-home technologies is their potential to reduce human contact, particularly from cherished caregivers. In this exploratory in situ study, we provided an ecosystem of networked monitoring technologies to six older adults and their caregivers. We analyzed the amount and content of communication between them. The amount of noncomputer-mediated communication did not decrease through the 6-week study. The content of communication coalesced into four themes: communication about the technologies, communication facilitated by technologies, intrusiveness of technologies, and fun and playfulness with the technologies. Results suggest that in-home technologies, designed with sensitivity to older adults' primary motivations, have the potential to shape and tailor important relationships in later life. 相似文献
36.
James Alfred Walker Katharina Völk Stephen L. Smith Julian Francis Miller 《Genetic Programming and Evolvable Machines》2009,10(4):417-445
Parallel and distributed methods for evolutionary algorithms have concentrated on maintaining multiple populations of genotypes,
where each genotype in a population encodes a potential solution to the problem. In this paper, we investigate the parallelisation
of the genotype itself into a collection of independent chromosomes which can be evaluated in parallel. We call this multi-chromosomal evolution
(MCE). We test this approach using Cartesian Genetic Programming and apply MCE to a series of digital circuit design problems
to compare the efficacy of MCE with a conventional single chromosome approach (SCE). MCE can be readily used for many digital
circuits because they have multiple outputs. In MCE, an independent chromosome is assigned to each output. When we compare
MCE with SCE we find that MCE allows us to evolve solutions much faster. In addition, in some cases we were able to evolve
solutions with MCE that we unable to with SCE. In a case-study, we investigate how MCE can be applied to to a single objective
problem in the domain of image classification, namely, the classification of breast X-rays for cancer. To apply MCE to this
problem, we identify regions of interest (RoI) from the mammograms, divide the RoI into a collection of sub-images and use
a chromosome to classify each sub-image. This problem allows us to evaluate various evolutionary mutation operators which
can pairwise swap chromosomes either randomly or topographically or reuse chromosomes in place of other chromosomes. 相似文献
37.
38.
Moritz Tebbe Elizabeth Galati Gilbert C. Walker Eugenia Kumacheva 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(37)
Future progress in nanoscience and nanotechnology necessitates further development of versatile, labor‐, and cost‐efficient surface patterning strategies. A new approach to nanopatterning is reported, which utilizes surface segregation of a smooth layer of an end‐grafted homopolymer in a poor solvent. The variation in polymer grafting density yields a range of surface nanostructures, including randomly organized pinned spherical micelles, worm‐like structures, networks, and porous films. The capability to use the polymer patterns for site‐specific deposition of small molecules, polymers, or nanoparticles is shown. This versatile strategy enables patterning of curved surfaces with direct access to the substrate and no need in changing polymer composition to realize different surface patterns. 相似文献
39.
DI Blyth MS Pedrick TJ Savage H Bright JE Beesley S Sanjar 《Canadian Metallurgical Quarterly》1998,19(1):38-54
40.
We describe a type of multilayer dielectric coating designed to enhance the intensity of evanescent waves. The coating consists of a stack of alternating high- and low-index quarter-wave layers followed by a final low-index layer whose thickness is chosen to optimize the evanescent-wave intensity. Indirect measurements of the film properties are in good agreement with theory. 相似文献