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   282篇
  免费   10篇
电工技术   1篇
化学工业   39篇
金属工艺   4篇
机械仪表   6篇
建筑科学   3篇
能源动力   5篇
轻工业   9篇
水利工程   1篇
石油天然气   2篇
无线电   50篇
一般工业技术   41篇
冶金工业   64篇
原子能技术   6篇
自动化技术   61篇
  2022年   3篇
  2021年   5篇
  2020年   6篇
  2019年   5篇
  2018年   8篇
  2017年   1篇
  2016年   4篇
  2015年   3篇
  2014年   5篇
  2013年   13篇
  2012年   23篇
  2011年   5篇
  2010年   9篇
  2009年   6篇
  2008年   13篇
  2007年   15篇
  2006年   18篇
  2005年   6篇
  2004年   7篇
  2003年   8篇
  2002年   4篇
  2001年   6篇
  2000年   4篇
  1999年   9篇
  1998年   23篇
  1997年   14篇
  1996年   15篇
  1995年   11篇
  1994年   6篇
  1993年   1篇
  1992年   5篇
  1991年   6篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1985年   3篇
  1984年   2篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有292条查询结果,搜索用时 31 毫秒
81.
Nutritional analyses were performed on 27 fruit species that are eaten by frugivorous birds in east Mediterranean habitats in Israel. The essential amino acid (EAA) profile [compared by principal component analysis (PCA)] of these fruits indicated two distinct groups of fruits. The main group consisted of 23 species that were similar in their relatively low total EAA quantities and unbalanced EAA profiles. On average, the EAAs phenylalanine and tyrosine were most concentrated and histidine least (tryptophan was not measured). Comparing the relative amounts of EAAs in fruits with required amounts for maintenance of granivorous passerine birds revealed that these fruits are deficient in all or most EAAs. The sulfur-containing amino acids (methionine and cystine) were most limiting relative to the required amount (41–61% below requirement), while four others (arginine, lysine, isoleucine, and leucine) were severely deficient (30–37% below requirement). These results complement reports suggesting that frugivorous birds have lower total protein demands than granivores. The second group of four fruit species had relatively high total EAA contents. Each of these fruits appeared to contain especially large quantities of some EAAs, but it was uncertain whether some high concentrations could have resulted from interactions in the pulp during preparation and chemical analysis.  相似文献   
82.
This study was undertaken in order to investigate the effect of reduced ambient pressure from an atmospheric pressure (101 kPa) to 0.1 kPa on one-pass full penetration welding of thick high-tensile strength steel plate of 23 mm thickness. A 16 kW disk laser of 1030 nm in wavelength was employed to weld HT980 grade plates at the speed of 5–25 mm/s. In partial penetration welding, it was revealed that humping phenomena occurred easily. Full penetration welding of the high-tensile strength steel plates could not be achieved at 101 kPa. On the other hand, full penetration welding was obtained at the welding speed of less than 20 mm/s at the pressure of less than 10 kPa. Especially, at 0.1 kPa, and 17 and 20 mm/s, sound weld joints without defects were obtained. According to the observation results of a keyhole inlet and a surface molten pool during welding with a high-speed video camera, the melt in front of a keyhole was smaller and the behaviour of a keyhole and a plume was much more stable at 0.1 kPa than at 101 kPa. Moreover, in the full penetration welding, spattering was suppressed under the proper conditions. Such phenomena became more stable in fast welding. It was revealed in laser welding of thick high-tensile strength steel plates that the formation of narrow I-shaped weld beads by achieving full-penetration welding in low vacuum was essential for the production of sound welds without defect.  相似文献   
83.
The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed.  相似文献   
84.
4D printing is a novel approach that enables dynamic functionality in ordinary static object. We used a methacrylated semicrystalline polymer to print objects exhibiting thermally triggered shape memory behaviour. By exploring various molecular weights, it was found that a methacrylated polycaprolactone polymer with a number average molecular weight of 10,000?g?mol?1 exhibited the best thermal and mechanical behaviour. The effect of dyes’ addition to the ink formulation on the photopolymerisation and on the printing processes was evaluated. The ink was utilised for demonstrating fabrication of dynamic jewellery and a shoe accessory by Digital Light Processing printing.  相似文献   
85.
In La214, the electronic specific heat coefficient (=C el /T) is gradually suppressed with lowering T below a certain temperature T* (> T c ), where the in-plane resistivity and magnetic susceptibility also tend to be suppressed slightly. Temperature T*, increasing with lowering x, is in qualitative agreement with the mean field T c (T co ), estimated from the superconducting gap amplitude 2 o at T T c , as the onset temperature T* of a pseudogap in Bi2212. The gradual suppression of below T co implies that a pseudogap will also open up below T co in La214 as in Bi2212. In underdoped samples, whose pseudogap-like behaviors in C el(T) become marked, the anomaly of C el around T c is rather different from the BCS expectation.  相似文献   
86.
Multi-modality (MM) positron emission tomography-computed tomography (PET-CT) visualises biological and physiological functions (from PET) as region of interests (ROIs) within a higher resolution anatomical reference frame (from CT). The need to efficiently assess and assimilate the information from these co-aligned volumes simultaneously has stimulated new visualisation techniques that combine 3D volume rendering with interactive transfer functions to enable efficient manipulation of these volumes. However, in typical MM volume rendering visualisation, the transfer functions for the volumes are manipulated in isolation with the resulting volumes being fused, thus failing to exploit the spatial correlation that exists between the aligned volumes. Such lack of feedback makes MM transfer function manipulation complex and time consuming. Further, transfer function alone is often insufficient to select the ROIs when they have similar voxel properties to those of non-relevant regions. In this study, we propose a new ROI-based MM visibility-driven transfer function (m 2-vtf) for PET-CT visualisation. We present a novel ‘visibility’ metric, a fundamental optical property that represents how much of the ROIs are visible to the users, and use it to measure the visibility of the ROIs in PET in relation to how it is affected by transfer function manipulations to its counterpart CT. To overcome the difficulty in ROI selection, we provide an intuitive ROI selection tool based on automated PET segmentation. We further present a MM transfer function automation where the visibility metrics from the PET ROIs are used to automate its CT’s transfer function. Our GPU implementation achieved an interactive visualisation of PET-CT with efficient and intuitive transfer function manipulations.  相似文献   
87.
Morag I 《Applied ergonomics》2007,38(2):201-211
The occupational ergonomic program that Intel's newly established manufacturing plant in Israel implemented in 1997 helped prevent injuries and also marked the launch of a whole new approach to ergonomics. A key element in the success of the seven-point program was a strong commitment from management, which came to regard this plan as a vital strategic element in the new plant's success. Comprehensive, top-down planning imposed obligations on all elements in the manufacturing spectrum, from suppliers to contractors to employees. Work requirements were set; cooperation with the plant's occupational health professionals was established; and long-term reporting and instruction systems were developed. Extensive ergonomic training was a crucial factor in integrating ergonomic procedures into the organization's day-to-day activities. Along with this instructional program, ergonomic engineers implemented a strict measuring system to ensure that each ergonomic activity would be performed according to schedule. By the time the factory opened its gates and began to produce, a vigorous ergonomic environment had emerged and employees were displaying an ergonomic mindset that also impinged upon their non-work activities. As a result of the successful implementation of the program, Intel's ergonomic program has become a model for Israeli industry. This paper presents a full ergonomic program that besides supplying the Intel plant with solutions was unique enough to impact the whole Israeli industry.  相似文献   
88.
89.
Functional imaging with PET and SPECT is capable of visualizing subtle changes in physiological function in vivo, which aids in the early diagnosis of disease. Quantitative functional parameters are usually derived by curve fitting the dynamic data of a functional imaging study. However, the intrinsic high level of noise and low signal to noise ratio can lead to instability in the parameter estimation and give rise to non-physiological parameter estimates. Clustering techniques have been applied to improve signal to noise ratio and the reliability of parametric image generation, but these may enhance partial volume effects (PVE) and result in biased estimates for small structures. Therefore, a systematic study was performed using computer simulations of SPECT data and the generalized linear least square algorithm (GLLS) to evaluate the ability of three proposed enhanced methods and a clustering-aided method to improve the reliability of parametric image generation. The results demonstrate that clustering with sufficient cluster numbers ameliorated PVE and provided noise-insensitive parameter estimates. The enhanced GLLS method with a prior volume of distribution and bootstrap Monte Carlo resampling improved the reliability of the curve fitting, and is thus suitable for application to noisy SPECT data.  相似文献   
90.
An intervention study was conducted to examine the effectiveness of an innovative self-modeling photo-training method for reducing musculoskeletal risk among office workers using computers. Sixty workers were randomly assigned to either: 1) a control group; 2) an office training group that received personal, ergonomic training and workstation adjustments or 3) a photo-training group that received both office training and an automatic frequent-feedback system that displayed on the computer screen a photo of the worker's current sitting posture together with the correct posture photo taken earlier during office training. Musculoskeletal risk was evaluated using the Rapid Upper Limb Assessment (RULA) method before, during and after the six weeks intervention. Both training methods provided effective short-term posture improvement; however, sustained improvement was only attained with the photo-training method. Both interventions had a greater effect on older workers and on workers suffering more musculoskeletal pain. The photo-training method had a greater positive effect on women than on men.  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