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   1812篇
  免费   89篇
  国内免费   1篇
电工技术   28篇
化学工业   555篇
金属工艺   16篇
机械仪表   44篇
建筑科学   56篇
能源动力   69篇
轻工业   204篇
水利工程   7篇
石油天然气   2篇
武器工业   1篇
无线电   149篇
一般工业技术   269篇
冶金工业   145篇
原子能技术   17篇
自动化技术   340篇
  2023年   10篇
  2022年   69篇
  2021年   89篇
  2020年   42篇
  2019年   45篇
  2018年   53篇
  2017年   33篇
  2016年   55篇
  2015年   49篇
  2014年   65篇
  2013年   132篇
  2012年   117篇
  2011年   121篇
  2010年   92篇
  2009年   76篇
  2008年   77篇
  2007年   95篇
  2006年   63篇
  2005年   57篇
  2004年   49篇
  2003年   52篇
  2002年   41篇
  2001年   25篇
  2000年   23篇
  1999年   27篇
  1998年   56篇
  1997年   54篇
  1996年   27篇
  1995年   22篇
  1994年   30篇
  1993年   19篇
  1992年   14篇
  1991年   9篇
  1990年   6篇
  1989年   6篇
  1988年   8篇
  1987年   7篇
  1986年   4篇
  1984年   13篇
  1983年   5篇
  1982年   6篇
  1981年   4篇
  1980年   8篇
  1979年   7篇
  1978年   7篇
  1977年   7篇
  1976年   6篇
  1971年   3篇
  1967年   3篇
  1966年   2篇
排序方式: 共有1902条查询结果,搜索用时 687 毫秒
1.
2.
3.
Photonic Network Communications - Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous...  相似文献   
4.
5.
Excessive energy intake may evoke complex biochemical processes characterized by inflammation, oxidative stress, and impairment of mitochondrial function that represent the main factors underlying noncommunicable diseases. Because cow milk is widely used for human nutrition and in food industry processing, the nutritional quality of milk is of special interest with respect to human health. In our study, we analyzed milk produced by dairy cows fed a diet characterized by a high forage:concentrate ratio (high forage milk, HFM). In view of the low n-6:n-3 ratio and high content of conjugated linoleic acid of HFM, we studied the effects of this milk on lipid metabolism, inflammation, mitochondrial function, and oxidative stress in a rat model. To this end, we supplemented for 4 wk the diet of male Wistar rats with HFM and with an isocaloric amount (82 kJ, 22 mL/d) of milk obtained from cows fed a diet with low forage:concentrate ratio, and analyzed the metabolic parameters of the animals. Our results indicate that HFM may positively affect lipid metabolism, leptin:adiponectin ratio, inflammation, mitochondrial function, and oxidative stress, providing the first evidence of the beneficial effects of HFM on rat metabolism.  相似文献   
6.
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments.  相似文献   
7.
The radiation from power-bus structures on high-speed printed circuit boards due to the switching noise current of digital integrated circuits is investigated. The study is based on an analytical cavity-resonator model for a rectangular parallel-plate structure. Based on the application of the field-equivalence principle, the radiated field is calculated from the electric edge-field distribution. For typical board dimensions, several cavity-mode resonances occur within the typical frequency range of interest, leading to relatively high maximum values for radiated emission. The evaluation of the radiation patterns reveals that all (0, nth) resonances have equal maximum amplitudes in the whole mode spectrum. This allows the setting up of an engineering equation for quantifying the noise-current-related maximum radiated field strength, including the dielectric and ohmic loss. Among all geometrical and material parameters, the dielectric thickness is one of the most effective ones to control radiated emission. The theoretical results are well confirmed by accurate measurements carried out in an anechoic room.  相似文献   
8.
In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data.  相似文献   
9.
There are several damping phenomena in quantum optics. Such phenomena have been usually explained by open systems. In statistical physics, open system dynamics have been used to study the irreversibility and the approach to equilibrium. In this paper, the dynamical change of the mutual entropy for an open system, frequently studied in the quantum optics literature, is rigorously computed through a model of quantum Markov chain. In particular, the concrete formula of Stinespring expression for such a model is obtained and applied to the derivation of the mutual entropy, and some computational results are presented.  相似文献   
10.
Biodegradable hollow microfibres containing particles loaded with specific active agents can be potentially employed to produce a special kind of substrate for tissue engineering, able to function as a scaffold and at the same time to act as a drug‐releasing system. Biodegradable hollow microfibres based on poly(lactic acid) were produced by a dry–wet spinning procedure. Drug‐loaded microparticles were prepared by a simple oil‐in‐water emulsion and entrapped inside the fibres. The morphology of both fibres and particles was investigated by scanning electron microscopy. The mechanical and thermal properties of the fibres were investigated by tensile tests and differential scanning calorimetry. In vitro tests were performed to evaluate the release of the drug from the fibres loaded with the particles Copyright © 2004 Society of Chemical Industry  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