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   547篇
  免费   19篇
  国内免费   1篇
电工技术   9篇
综合类   2篇
化学工业   105篇
金属工艺   20篇
机械仪表   10篇
建筑科学   8篇
能源动力   35篇
轻工业   40篇
水利工程   5篇
无线电   49篇
一般工业技术   146篇
冶金工业   33篇
原子能技术   8篇
自动化技术   97篇
  2024年   2篇
  2023年   19篇
  2022年   20篇
  2021年   28篇
  2020年   19篇
  2019年   20篇
  2018年   31篇
  2017年   29篇
  2016年   20篇
  2015年   15篇
  2014年   25篇
  2013年   54篇
  2012年   47篇
  2011年   28篇
  2010年   25篇
  2009年   19篇
  2008年   24篇
  2007年   12篇
  2006年   7篇
  2005年   10篇
  2004年   9篇
  2003年   6篇
  2002年   5篇
  2001年   5篇
  2000年   2篇
  1999年   1篇
  1998年   5篇
  1997年   8篇
  1996年   6篇
  1995年   8篇
  1994年   9篇
  1993年   3篇
  1992年   6篇
  1991年   6篇
  1990年   8篇
  1989年   3篇
  1988年   5篇
  1987年   2篇
  1985年   3篇
  1984年   1篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1974年   1篇
排序方式: 共有567条查询结果,搜索用时 15 毫秒
81.
Parallax scrolling is a popular web technique used widely in product presentation websites, but its effect on user experience is unknown. Parallax scrolling allows the object displayed in the foreground to move faster than the object displayed in the background, so as to create a 3D effect. Dimensionality and scrolling (modality interactivity) are two major characteristics of this technique. A 2 (dimension) × 2 (modality interactivity) between-subjects (= 295) online experiment revealed that parallax scrolling influences user engagement through two routes: the cue route (perceived coolness, perceived vividness) and the action route (natural mapping, perceived ease of use). User engagement is in turn associated with positive attitudes and behavioral intentions toward the website and the product. The theoretical contribution of the study is it examined interface feature of parallax scrolling on both user perceptions and user actions using the theory of interactive media effects (TIME). The practical contribution of the study is it provides a roadmap to web developers to emphasize affective factors (i.e., vividness, coolness) rather than cognitive factors (i.e., natural mapping, perceived usefulness) when it comes to improving the user experience of the product presentation websites.  相似文献   
82.
Multimedia Tools and Applications - Breast cancer is one of the widespread reasons of morbidity worldwide that begins in the cells of the tissues of morbidity worldwide in the woman community....  相似文献   
83.

This paper presents an adaptive Improved Recycling Folded Cascode (IRFC) amplifier with improved gain, high slew rate, high phase margin and reduced power consumption. The proposed design is implemented using 180 nm technology with a supply voltage of 1.8 V and a capacitive load of 1 pF. The proposed design is compared with basic two stage op-amp, cascode amplifier and conventional recycling folded cascode amplifier (RFC). Analysis demonstrates that the flexible structure of IRFC with adaptive biasing shows an improvement in gain to 87.74 dB, approximately three times enhancement in slew rate to 53.8 V/µs when compared with the design specifications. The phase margin was observed to be 64.86°. The design also reports an increase in output swing. The gain increases to 109 dB when a cascode stage is added to the IRFC structure.

  相似文献   
84.
Riverscape genetics of fish, though extensively studied in temperate regions, have received limited interest in tropical rivers, especially in montane systems which not only harbour several endemic and threatened species, but are also subjected to extensive habitat modifications. We determine the population genetic structure of two endemic balitorid loaches (Bhavania australis and Travancoria elongata) in response to natural (25 m high waterfall) and artificial (23 m high and 290 m long hydropower dam) barriers in a small mountain riverscape in the Western Ghats Hotspot. Population genetics analysis using mitochondrial cytochrome b gene sequence showed low nucleotide diversity, haplotype diversity and genetic differentiation among populations, for both species, suggesting that barriers did not influence genetic structuring. Though migration analysis also revealed that barriers did not affect movement of the two species through the riverscape, patterns in mutation-scaled immigration rates and population sizes differed between the two species supporting our observation that they rarely co-exist in the same habitat, likely as an effect of competitive exclusion. Mismatch distribution and Bayesian skyline plot suggested recent expansion in the populations of B. australis and corresponding population decline in T. elongata in the last 100 years, which probably explains the widespread and abundant distribution of B. australis as opposed to the narrow endemism and rarity of T. elongata. Our results provide novel insights into the ecology of balitorid loaches and their response to riverine barriers in a tropical mountain landscape.  相似文献   
85.
Barium hexaferrite BaFe12O19 (BHF) ceramic was synthesized by chemical route on sintering at 1050 °C for 12 h. The synthesized material was characterized by XRD, SEM, AFM and TEM analysis. Metal oxide stretching frequencies corresponding to Fe-O, Ba-O, and Fe-O-Fe bands are confirmed by FTIR studies. The hexagonal nature of the BHF ceramic was confirmed by TEM analysis and Rietveld refinement with space group P63/mmc. The particle size observed by TEM is 175 nm. The root means square and average roughness were found to be 61.048 nm and 44.025 nm respectively. The M-T and M-H hysteresis loop indicates temperature dependent ferromagnetic behavior of BHF ceramic. The temperature and frequency dependent dielectric properties were explained by Maxwell-Wagner theory. The value of dielectric constant (ε′) for BHF ceramic was found to be 22× 103 at 100 Hz and 483 K.  相似文献   
86.
One of the crucial regulators of embryonic patterning and tissue development is the Hedgehog‐glioma (Hh‐Gli) signalling pathway; its uncontrolled activation has been implicated in different types of cancer in adult tissues. Primary cilium is one of the important factors required for the activation of Hh signalling, as it brings the critical components together for key protein–protein interactions required for Hh pathway regulation. Most of the synthetic and natural small molecule modulators of the pathway primarily antagonise Smoothened (Smo) or other effectors like Hh ligand or Gli. Here, we report a previously described Hh antagonist, with a pyrimidine–indole hybrid (PIH) core structure, as an inhibitor of ciliogenesis. The compound is unique in its mode of action, as it shows perturbation of microtubule dynamics in both cell‐based assays and in vivo systems (zebrafish embryos). Further studies revealed that the probable targets are α‐tubulin and its acetylated form, found in the cytoplasm and primary cilia. PIH also showed axonal defasiculation in developing zebrafish embryos. We thus propose that PIH antagonises Hh signalling by repressing cilia biogenesis and disassembling α‐tubulin from its stabilised form.  相似文献   
87.
Pharmaceutical compounds and their derivatives are major pollutants in the environment, as their metabolites affect the terrestrial as well as aquatic organisms in one or another way. In recent times, many papers have discussed the treatment procedures for single pharmaceutical and mixture of pharmaceutical components, but only few papers have discussed the fate and the exposure of pharmaceutical contaminants in our environment. In this paper, we discuss the sources and the forms of pharmaceutical products and their resultant in the environment and their addition to the microbial and to human communities. A detailed discussion of various treatment techniques from conventional to current techniques, their advantages and disadvantages is given here. Researchers are finding the techniques in order to completely degrade the contaminants and their transformed products from the environment. Among the technique, s nanotechnology was found to be an efficient technique, and the combination of nanotechnology with other conventional technologies gives higher removal efficiency.  相似文献   
88.
Night video enhancement techniques are widely used for identifying suspicious activities captured by night visual surveillance systems. However, artificial light sources present in the surroundings deteriorate the visual quality of the video captured during night. This non-uniform illumination reduces the object identification and tracking capability of a real-time visual security system. Thus, a uniform enhancement technique is insufficient for handling such uneven illumination. In this paper, we propose a novel night video enhancement scheme based on a hierarchical self-organizing network. This proposed scheme automatically groups and enhances the neighboring pixels of dark and light regions in each frame. In this scheme, two-level self- organizing neural networks were hierarchically arranged to group similar pixels present in the night video frame. We applied the no-reference-based performance evaluation metrics for measuring the objective quality of the video. The experimental results showed that our proposed approach considerably enhances the visual perception of the video captured at night under varied illumination conditions.  相似文献   
89.
Bacteria in drinking water systems can grow in bulk water and as biofilms attached to pipe walls, both causing regrowth problems in the distribution system. While studies have focused on evaluating the factors influencing the bacteria in bulk water and in biofilms separately, there is a need for understanding biofilm characteristics relative to the bulk water phase. The current study evaluated the effects of chlorine and residence time on the presence of culturable bacteria in biofilms relative to that in bulk water. The results showed that when no chlorine residual was present in the system, the median ratio of bulk to total bacteria was 0.81, indicating that 81% of the bacteria were present in bulk water, whereas only 19% were present in the biofilm. As chlorine concentration increased to 0.2, 0.5, and 0.7 mg/L, the median percentage of bacteria present in bulk water decreased to 37, 28, and 31, respectively. On the other hand, as the residence times increased to 8.2, 12, 24, and 48h, the median percentage of bacteria present in bulk water increased to 7, 37, 58, and 88, respectively, in the presence of a 0.2mg/L chlorine residual. The common notion that biofilms dominate the distribution system is not true under all conditions. These findings suggest that bulk water bacteria may dominate in portions of a distribution system that have a low chlorine residual.  相似文献   
90.
In this work, we develop a Ag@Al2O3@Ag plasmonic core–shell–satellite (PCSS) to achieve highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection of probe molecules. To fabricate PCSS nanostructures, we employ a simple hierarchical dewetting process of Ag films coupled with an atomic layer deposition (ALD) method for the Al2O3 shell. Compared to bare Ag nanoparticles, several advantages of fabricating PCSS nanostructures are discovered, including high surface roughness, high density of nanogaps between Ag core and Ag satellites, and nanogaps between adjacent Ag satellites. Finite-difference time-domain (FDTD) simulations of the PCSS nanostructure confirm an enhancement in the electromagnetic field intensity (hotspots) in the nanogap between the Ag core and the satellite generated by the Al2O3 shell, due to the strong core–satellite plasmonic coupling. The as-prepared PCSS-based SERS substrate demonstrates an enhancement factor (EF) of 1.7 × 107 and relative standard deviation (RSD) of ~7%, endowing our SERS platform with highly sensitive and reproducible detection of R6G molecules. We think that this method provides a simple approach for the fabrication of PCSS by a solid-state technique and a basis for developing a highly SERS-active substrate for practical applications.  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