首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3965篇
  免费   150篇
  国内免费   4篇
电工技术   46篇
综合类   11篇
化学工业   690篇
金属工艺   82篇
机械仪表   53篇
建筑科学   278篇
矿业工程   8篇
能源动力   103篇
轻工业   363篇
水利工程   41篇
石油天然气   17篇
无线电   392篇
一般工业技术   605篇
冶金工业   744篇
原子能技术   15篇
自动化技术   671篇
  2023年   37篇
  2022年   62篇
  2021年   80篇
  2020年   62篇
  2019年   76篇
  2018年   86篇
  2017年   75篇
  2016年   108篇
  2015年   86篇
  2014年   131篇
  2013年   219篇
  2012年   164篇
  2011年   220篇
  2010年   190篇
  2009年   138篇
  2008年   182篇
  2007年   166篇
  2006年   178篇
  2005年   138篇
  2004年   116篇
  2003年   130篇
  2002年   97篇
  2001年   92篇
  2000年   67篇
  1999年   70篇
  1998年   174篇
  1997年   100篇
  1996年   89篇
  1995年   71篇
  1994年   52篇
  1993年   50篇
  1992年   42篇
  1991年   26篇
  1990年   22篇
  1989年   40篇
  1988年   24篇
  1987年   31篇
  1986年   23篇
  1985年   29篇
  1984年   29篇
  1983年   20篇
  1982年   20篇
  1981年   21篇
  1980年   19篇
  1979年   21篇
  1978年   22篇
  1977年   33篇
  1976年   44篇
  1973年   21篇
  1972年   10篇
排序方式: 共有4119条查询结果,搜索用时 0 毫秒
41.
Limb repositioning is necessary for individuals with severe physical disabilities to sustain muscle strength and prevent pressure sores. As robotic technologies become ubiquitous, these tools offer promise to support the repositioning process. However, research has yet to focus on ways in which individuals with severe physical disabilities can control robots for these tasks. This paper presents a study that examines the needs and attitudes of potential users with physical disabilities to control a robotic aid for limb repositioning. Subjects expressed interest in using brain–computer interface (BCI) and speech recognition technologies for purposes of executing robotic tasks. The performance of four subjects controlling arm movements on an avatar through the keyboard, mouse, BCI, and Dragon NaturallySpeaking speech recognition was evaluated. Although BCI and speech technologies may limit physical fatigue, more challenges were faced using BCI and speech conditions compared to the keyboard and mouse. This research promotes accessibility into mainstream robotic technologies and represents the first step in the development of a robotic prototype using a BCI and speech recognition technologies for limb repositioning.  相似文献   
42.
Analogy based estimation (ABE) generates an effort estimate for a new software project through adaptation of similar past projects (a.k.a. analogies). Majority of ABE methods follow uniform weighting in adaptation procedure. In this research we investigated non-uniform weighting through kernel density estimation. After an extensive experimentation of 19 datasets, 3 evaluation criteria, 5 kernels, 5 bandwidth values and a total of 2090 ABE variants, we found that: (1) non-uniform weighting through kernel methods cannot outperform uniform weighting ABE and (2) kernel type and bandwidth parameters do not produce a definite effect on estimation performance. In summary simple ABE approaches are able to perform better than much more complex approaches. Hence,—provided that similar experimental settings are adopted—we discourage the use of kernel methods as a weighting strategy in ABE.  相似文献   
43.
Urbanisation results in changes to runoff behaviour which, if not addressed, inevitably degrade receiving waters. To date, most stormwater management has focussed on the streetscape and public open space. Given that much of the catchment imperviousness is located on private land, we developed and tested a novel economic instrument (a uniform price auction) for encouraging allotment-scale stormwater retention. We evaluated bids using an integrated environmental benefit index (EBI), based on the ability of the proposed works to reduce runoff frequency, pollutant loads and to reduce potable water demand. The uniform price auction resulted in 1.4 ha of impervious areas being effectively 'disconnected' from the stormwater system. The EBI provided an objective and transparent method of comparing bids, which varied in the type of works proposed (e.g. rainwater tank, rain-garden), the cost and the resulting environmental benefit. Whilst the pilot auction was a success, the public subsidy of works undertaken was around 85%, meaning that property owners a relatively small private benefit in the works. Future auction rounds will be revised to (i) test an EBI which is more focussed on the protection of streams (assessing changes to runoff frequency, baseflow volumes and water quality) and (ii) provide an auction process which is simpler to understand, and provides greater practical support for landholders who wish to undertake works.  相似文献   
44.
The impact of misregistration on SRTM and DEM image differences   总被引:2,自引:0,他引:2  
Image differences between Shuttle Radar Topography Mission (SRTM) data and other Digital Elevation Models (DEMs) are often performed for either accuracy assessment or for estimating vegetation height across the landscape. It has been widely assumed that the effect of sub-pixel misregistration between the two models on resultant image differences is negligible, yet this has not previously been tested in detail. The aim of this study was to determine the impact that various levels of misregistration have on image differences between SRTM and DEMs. First, very accurate image co-registration was performed at two study sites between higher resolution DEMs and SRTM data, and then image differences (SRTM–DEM) were performed after various levels of misregistration were systematically introduced into the SRTM data. It was found that: (1) misregistration caused an erroneous and dominant correlation between elevation difference and aspect across the landscape; (2) the direction of the misregistration defined the direction of this erroneous and systematic elevation difference; (3) for sub-pixel misregistration the error due solely to misregistration was greater than, or equal to the true difference between the two models for substantial proportions of the landscape (e.g., greater than 33% of the area for a half-pixel misregistration); and (4) the strength of the erroneous relationship with aspect was enhanced by steeper terrain. Spatial comparisons of DEMs were found to be sensitive to even sub-pixel misregistration between the two models, which resulted in a strong erroneous correlation with aspect. This misregistration induced correlation with aspect is not likely specific to SRTM data only; we expect it to be a generic relationship present in any DEM image difference analysis.  相似文献   
45.
Kidney failure is a major health problem worldwide. Patients with end-stage renal disease require intensive medical support by dialysis or kidney transplantation. Current methods for diagnosis of kidney disease are either invasive or insensitive, and renal function may decline by as much as 50% before it can be detected using current techniques. The goal of this study was, therefore, to identify biomarkers of kidney disease (associated with renal fibrosis) that can be used for the development of a non-invasive clinical test for early disease detection. We utilized two protein-profiling technologies (SELDI-TOF MS and 2-D) to screen the plasma and kidney proteome for aberrantly expressed proteins in an experimental mouse model of unilateral uretric obstruction, which mimics the pathology of human renal disease. Several differentially regulated proteins were detected at the plasma level of day-3-obstructed animals, which included serum amyloid A1, fibrinogen α, haptoglobin precursor protein, haptoglobin and major urinary proteins 11 and 8. Differentially expressed proteins detected at the tissue level included ras-like activator protein 2, haptoglobin precursor protein, malate dehydrogenase, α enolase and murine urinary protein (all p<0.05 versus controls). Immunohistochemistry was used to confirm the up-regulation of fibrinogen. Interestingly, these proteins are largely separated into four major classes: (i) acute-phase reactants (ii) cell-signaling molecules (iii) molecules involved in cell growth and metabolism and (iv) urinary proteins. These results provide new insights into the pathology of obstructive nephropathy and may facilitate the development of specific assay(s) to detect and monitor renal fibrosis.  相似文献   
46.
A study was carried out in which carcass characteristics of 36 gilts were evaluated: 18 originated from the Hungarian 'Hungahyb' cross-breed, another 18, with undefined genetic background, from small private household plots. Two, rather simple substitute reference methods, called referee methods, were evaluated: measurement of carcass weight without skin and subcutaneous fat ('meat + bone'), and measurement of carcass weight without skin, subcutaneous fat and bone ('boneless meat'). Both methods gave a rather close relationship with the Kulmbach reference lean; however, removal of bone had presumably a beneficial effect on stability of prediction. The importance of preliminary information in quantitative form, giving a theoretical background for prediction equations, was presented as an example. Simple material balances could be formulated between reference lean and 'meat + bone' or 'boneless meat' content. Such material balances could not be set up with the indirect, rapid surrogate methods using mainly linear measurements (e.g. fat and muscle thickness, etc.) For this reason, as several other publications demonstrated, these latter methods seem to be more susceptible to bias than the referee methods. By determining the lipid content of the homogenised 'boneless meat' component, a 'lean' value adjusted to 3% fat content could be calculated from data which was compared to the dissected reference lean standardised also to contain 3% fat. These relationships, for several reasons discussed in this paper, were not as close as expected. So, further studies are needed to reveal these discrepancies.  相似文献   
47.
Pickering and Chater (P&C) maintain that folk psychology and cognitive science should neither compete nor cooperate. Each is an independent enterprise, with a distinct subject matter and characteristic modes of explanation. P&C's case depends upon their characterizations of cognitive science and folk psychology. We question the basis for their characterizations, challenge both the coherence and the individual adequacy of their contrasts between the two, and show that they waver in their views about the scope of each. We conclude that P&C do not so muchdiscover ascreate the gap they find between folk psychology and cognitive science. It is an artifact of their implausible and unmotivated attempt to demarcate the two areas, and of the excessively narrow accounts they give of each.  相似文献   
48.
Tizard  James  Rietz  Tim  Liu  Xuanhui  Blincoe  Kelly 《Requirements Engineering》2022,27(3):293-315
Requirements Engineering - Many software users give feedback online about the applications they use. This feedback often contains valuable requirements information that can be used to guide the...  相似文献   
49.
Autonomous Robots - We propose a simple yet effective set of local control rules to make a small group of “herder agents” collect and contain in a desired region a large ensemble of...  相似文献   
50.
An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically‐heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号