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   516篇
  免费   32篇
  国内免费   2篇
电工技术   18篇
综合类   1篇
化学工业   98篇
金属工艺   28篇
机械仪表   6篇
建筑科学   8篇
能源动力   23篇
轻工业   39篇
水利工程   1篇
石油天然气   2篇
无线电   42篇
一般工业技术   87篇
冶金工业   103篇
原子能技术   6篇
自动化技术   88篇
  2023年   2篇
  2022年   9篇
  2021年   9篇
  2020年   9篇
  2019年   9篇
  2018年   18篇
  2017年   13篇
  2016年   26篇
  2015年   9篇
  2014年   34篇
  2013年   21篇
  2012年   29篇
  2011年   22篇
  2010年   22篇
  2009年   24篇
  2008年   19篇
  2007年   17篇
  2006年   16篇
  2005年   9篇
  2004年   14篇
  2003年   21篇
  2002年   11篇
  2001年   7篇
  2000年   5篇
  1999年   11篇
  1998年   49篇
  1997年   18篇
  1996年   19篇
  1995年   15篇
  1994年   14篇
  1993年   14篇
  1992年   4篇
  1991年   5篇
  1990年   3篇
  1988年   4篇
  1987年   1篇
  1986年   7篇
  1984年   2篇
  1982年   1篇
  1981年   3篇
  1980年   1篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
排序方式: 共有550条查询结果,搜索用时 15 毫秒
21.
Vocal fry (also called creak, creaky voice, and pulse register phonation) is a voice quality that carries important linguistic or paralinguistic information, depending on the language. We propose a set of acoustic measures and a method for automatically detecting vocal fry segments in speech utterances. A glottal pulse-synchronized method is proposed to deal with the very low fundamental frequency properties of vocal fry segments, which cause problems in the classic short-term analysis methods. The proposed acoustic measures characterize power, aperiodicity, and similarity properties of vocal fry signals. The basic idea of the proposed method is to scan for local power peaks in a ldquovery short-termrdquo power contour for obtaining glottal pulse candidates, check for periodicity properties, and evaluate a similarity measure between neighboring glottal pulse candidates for deciding the possibility of being vocal fry pulses. In the periodicity analysis, autocorrelation peak properties are taken into account for avoiding misdetection of periodicity in vocal fry segments. Evaluation of the proposed acoustic measures in the automatic detection resulted in 74% correct detection, with an insertion error rate of 13%.  相似文献   
22.
Identifying the extent to which the appearance of a humanoid robot affects human behavior toward it is important. We compared participant impressions of and behaviors toward two real humanoid robots in simple human-robot interactions. These two robots, which have different appearances but are controlled to perform the same recorded utterances and motions, are adjusted by a motion-capturing system. We conducted an experiment with 48 human participants who individually interacted with the two robots and also with a human for reference. The results revealed that different appearances did not affect participant verbal behaviors, but they did affect such nonverbal behaviors as distance and delay of response. These differences are explained by two factors: impressions and attributions.  相似文献   
23.
No Heading The new technique for embedding microimpurities into solid helium has been developed. A He crystal was grown in a vertical cylindrical cell placed in the bath of pumped LHe cryostat. The He solid was continuously moved downward by exhaust of helium from the cell bottom and was simultaneously restored from its upper edge by sedimentation of a jet of gas helium mixed with impurity. A guest particle density of 3· 1019 per cc and stable during an hour doped crystal growth with the rate of 1 mm per 20 s were achieved. The solid Deuterium clusters isolated in solid Helium have been investigated at T = 1.3K and P = 3 MPa by CARS technique. The strong effect of Raman scattering sensitivity to the molecular environment nuclear spin has been found in CARS - the ratio of probabilities for the scattering by para (J=1) and ortho (J=0) deuterium being equal to 1 in a gas is as high as 10,000 in nearly pure o-D2, whereas it is 50 in common Raman scattering. This effect has been shown to give rise starting from cluster size corresponding to the phonon band onset.PACS numbers: 33.20 Fb; 33.70 Jg: 67.80 Mg  相似文献   
24.
Although numerous swarm robotic systems have already been developed, they have exhibited limited adaptability. This was partly because the previous researchers designed the control schemes on the basis of informational interaction, without considering the physical effects of the environment. To tackle this problem, we employ an unconventional approach: we design a control scheme for swarm robots based on their physical interaction in a hydrodynamic field, inspired by biological swarming. Through simulations using a smoothed particle hydrodynamics method, we show that the proposed control scheme allows agents to form an ordered swarm in response to their environment.  相似文献   
25.
Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.  相似文献   
26.
27.
The phonon thermal conductivity of misfit-layered Ca3Co4O9 has been calculated by perturbed molecular dynamics using a classical force field. Detailed numerical analyses reveal that, in spite of its smaller cross-sectional area, the CoO2 layer transports more heat than the thicker rock salt (RS) layer, although its local thermal conduction is more suppressed than in another layered cobaltite, Na x CoO2. The origins of these differences have been elucidated through careful examination of the atomic arrangements in each layer. Since thermal conduction in the RS layer can be reduced without deteriorating electronic properties for which the CoO2 layer is responsible, it is suggested that the RS layer should be modified to further suppress the overall in-plane thermal conductivity. Computational experiments with increasing number of Ca–O planes in the RS layer showed the opposite trend to what can be predicted based on the misfit between two dissimilar layers. Further analyses to reveal the origin of these unexpected results provide yet another strategy to further decrease the thermal conductivity, namely to control the dynamic interference between atoms across the interface between two layers.  相似文献   
28.
Ionic liquid/polyvinylidene fluoride composite membrane was successfully prepared by impregnation method and used for the separation on organic chemical hydride process. The separation factors of C6H6/H2 and C6H12/H2 in the ternary mixture system were 7500 and 300, respectively. The ionic liquid membrane showed an excellent possibility as a technology of H2 purification in the organic chemical hydride process by removing aromatic hydrocarbon and cycloalkane simultaneously from the ternary system. © 2015 American Institute of Chemical Engineers AIChE J, 62: 624–628, 2016  相似文献   
29.
A new polymeric adsorbent material based on polyethylene (PE) was prepared by photografting of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) as a positively chargeable monomer to a PE film. The effects of the experimental parameters, such as the pH value, temperature, and grafted amount on adsorption of chromium(VI) (Cr(VI)) ions were investigated for the DMAEMA‐grafted PE (PE‐g‐PDAMEMA) films. The maximum adsorption capacity was obtained at the initial pH value of 3.0 for a PE‐g‐PDMAEMA film with 1.8 mmol/g and the maximum adsorption capacity obtained was higher than or compatible to those of many of the other polymeric adsorbents prepared for Cr(VI) ions. The adsorption kinetics obeyed the mechanism of the pseudo‐second order kinetic model and adsorption of Cr(VI) ions on PE‐g‐PDMAEMA films was well expressed by the Langmuir isotherm model. A high Langmuir adsorption constant suggests that the adsorption of Cr(VI) ions occurs between protonated dimethylamino groups and ions mainly through the electrostatic interaction. Cr(VI) ions adsorbed were successfully desorbed from a PE‐g‐PDMAEMA film in solutions of NaCl, NH4Cl, NH4Cl containing NaOH, and NaOH and a PE‐g‐PDMAEMA film was regenerated and repeatedly used for adsorption of Cr(VI) ions without appreciable loss in the adsorption capacity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43360.  相似文献   
30.
The progression of chronic liver disease differs by etiology. The aim of this study was to elucidate the difference in disease progression between chronic hepatitis C (CHC) and nonalcoholic fatty liver disease (NAFLD) by means of fibrosis markers, liver function, and hepatic tissue blood flow (TBF). Xenon computed tomography (Xe-CT) was performed in 139 patients with NAFLD and 152 patients with CHC (including liver cirrhosis (LC)). The cutoff values for fibrosis markers were compared between NAFLD and CHC, and correlations between hepatic TBF and liver function tests were examined at each fibrosis stage. The cutoff values for detection of the advanced fibrosis stage were lower in NAFLD than in CHC. Although portal venous TBF (PVTBF) correlated with liver function tests, PVTBF in initial LC caused by nonalcoholic steatohepatitis (NASH-LC) was significantly lower than that in hepatitis C virus (C-LC) (p = 0.014). Conversely, the liver function tests in NASH-LC were higher than those in C-LC (p < 0.05). It is important to recognize the difference between NAFLD and CHC. We concluded that changes in hepatic blood flow occurred during the earliest stage of hepatic fibrosis in patients with NAFLD; therefore, patients with NAFLD need to be followed carefully.  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