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   1369篇
  免费   40篇
  国内免费   3篇
电工技术   16篇
综合类   1篇
化学工业   306篇
金属工艺   27篇
机械仪表   52篇
建筑科学   35篇
矿业工程   1篇
能源动力   41篇
轻工业   114篇
水利工程   9篇
石油天然气   2篇
无线电   152篇
一般工业技术   251篇
冶金工业   247篇
原子能技术   9篇
自动化技术   149篇
  2024年   8篇
  2023年   10篇
  2022年   23篇
  2021年   37篇
  2020年   22篇
  2019年   36篇
  2018年   48篇
  2017年   23篇
  2016年   50篇
  2015年   25篇
  2014年   34篇
  2013年   75篇
  2012年   55篇
  2011年   55篇
  2010年   40篇
  2009年   55篇
  2008年   48篇
  2007年   51篇
  2006年   48篇
  2005年   38篇
  2004年   36篇
  2003年   38篇
  2002年   27篇
  2001年   17篇
  2000年   19篇
  1999年   18篇
  1998年   86篇
  1997年   50篇
  1996年   40篇
  1995年   33篇
  1994年   19篇
  1993年   26篇
  1992年   10篇
  1991年   12篇
  1989年   11篇
  1988年   9篇
  1987年   13篇
  1986年   8篇
  1985年   10篇
  1984年   11篇
  1982年   11篇
  1981年   11篇
  1980年   15篇
  1979年   10篇
  1978年   9篇
  1977年   9篇
  1976年   16篇
  1974年   8篇
  1973年   8篇
  1970年   8篇
排序方式: 共有1412条查询结果,搜索用时 15 毫秒
61.
62.
A review of factors affecting fat absorption in hot chips   总被引:4,自引:0,他引:4  
Consumption of hot chips is a convenience food in most countries. Unfortunately, these are high in fat and contribute to fat-related diseases in societies with a high fat consumption. There is substantial scope through best-practice deep-frying techniques for producing lower fat, high-quality chips. From a review of the literature, the main factors associated with a lower-fat content of chips are thick (>12 mm), straight cut chips; cryogenic freezing methods; low moisture content of potatoes (specific gravity >1.1); frying fat: chip volume ratio of 6:1; frying at optimal temperature (180 to 185 degrees C) during cooking and turning the temperature down (approximately 140 degrees C) and covering the vats during slack periods; vigorously shaking the basket and hanging it over the deep fryer to drain after frying; maintaining the quality of the frying fat by regularly skimming the cracklings, filtering the fat, and topping up the fryer with fresh fat; keeping the fat turnover <5 days; regular cleaning of frying equipment. It is important that all deep frying operators are adequately trained in these techniques. It is also important that the frying medium is low in saturated and trans fatty acids (<20%) because of their effects on blood lipids and low in linolenic acid (<3%) because it is readily degraded. The widespread implementation of best-practice deep-frying would reduce fat content of hot chips and thus lower overall fat consumption.  相似文献   
63.
The phenomenon of hyperbolic heat conduction in contrast to the classical (parabolic) form of Fourier heat conduction involves thermal energy transport that propagates only at finite speeds as opposed to an infinite speed of thermal energy transport. To accommodate the finite speed of thermal wave propagation, a more precise form of heat flux law is involved, thereby modifying the heat flux originally postulated in the classical theory of heat conduction. As a consequence, for hyperbolic heat conduction problems, the thermal energy propagates with very sharp discontinuities at the wave front. The primary purpose of the present paper is to provide accurate solutions to a class of one-dimensional hyperbolic heat conduction problems involving non-Fourier effects that can precisely help understand the true response and furthermore can be used effectively for representative benchmark tests and for validating alternate schemes. As a consequence, the present paper purposely describes modeling/analysis formulations via specially tailored hybrid computations for accurately modeling the sharp discontinuities of the propagating thermal wave front. Comparative numerical test models are presented for various hyperbolic heat conduction models involving non-Fourier effects to demonstrate the present formulations.  相似文献   
64.

The automatic identification of the modulation format of a detected signal is a major task of an intelligent receiver in both military and civilian applications. It is well known that the maximum likelihood (ML) classifier requires a priori knowledge of the incoming signal and channel (including amplitude, timing information, noise power, and the roll-off factor of the pulse-shaping filter). To relax this requirement, we introduce a novel estimator to estimate the parameters required by the ML classifier which is blind to the modulation scheme of the received signal, and this gives rise to a new blind modulation classifier for digital amplitude-phase modulated signals. While the proposed classifier is completely blind, the simulation results show that the performance of this classifier is very close to the optimal non-blind classifier.

  相似文献   
65.
In the present work, we report the preparation of PLZT thin films in pure perovskite phase by RF magnetron sputtering without external substrate heating and their integration with micro-cantilevers. The ‘lift-off’ process for patterning different layers of a micro-cantilever including PLZT, Pt/Ti and Au/Cr was employed. The basic requirement of lift-off process is that the deposition temperature should not exceed 200°C otherwise photoresist will burn out. Therefore, one of the aims of the present work was to prepare PLZT film at lower deposition temperatures, which can be subsequently annealed to form pure perovskite phase. This also strongly favours the incorporation of ‘lift-off’ process for patterning in the complete process flow. As no external substrate heating was required in the deposition of PLZT film, this objective has been successfully accomplished in the present work. The ‘lift-off’ process has been successfully adopted for patterning the composite layers of PLZT/Pt/Ti and Au/Cr using thick positive photo-resist (STR-1045). Different types of cantilever beams incorporating PLZT films have been successfully fabricated using ‘lift-off’ process and bulk micromachining technology. The proposed process can be advantageously applied for the fabrication of various MEMS devices.  相似文献   
66.
In the present work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films in pure perovskite phase by RF magnetron sputtering. For this purpose, a 3-in. diameter target of PLZT (8/60/40) was prepared by conventional solid-state reaction route. The chemical composition of PLZT target was determined using gravimetric analysis followed by UV–vis and flame atomic absorption spectrometry. Various deposition parameters such as target-to-substrate spacing, deposition temperature, post-deposition annealing temperature and time have been optimized to obtain PLZT films in pure perovskite phase. The films prepared in pure argon at 100 W RF power without external substrate heating exhibited pure perovskite phase after rapid thermal annealing (RTA) as confirmed by X-ray diffraction (XRD). Compositional analysis of the PLZT film was performed by secondary ion mass spectroscopy (SIMS) using PLZT target as standard sample. Depth profile of the film shows very good stoichiometric uniformity of all elements of PLZT.  相似文献   
67.
Computer colour matching of paints is based on the determination of the Kubelka—Munk absorption (K) and scattering coefficients (S) of pigments. K and S are sensitive to particle size in the range of sizes employed in paint technology. The K—M theory does not provide any guidelines for the correction of the values of K and S with a change in particle size. On the other hand the Mie theory linear scattering coefficient can be calculated from a knowledge of size and refractive index of the pigment. A number of relations correlating the K—M scattering coefficient and the linear scattering coefficient have been proposed in the literature. Attempts are made to estimate the K—M scattering coefficient using a relation suggested by Mudgett and Richards and to make a comparison with experimental values. The Mie theory equations being complex, simplified equations applicable to pigment sizes for the calculation of Mie theory parameters are proposed. The viability of the simplified equations has been established by comparing the results with those obtained using the full Mie equations.The K—M scattering coefficient for titanium dioxide pigments has been determined from reflectance measurements. The particle size of titanium dioxide has been determined by a light scattering method. The K—M scattering coefficient calculated from the linear scattering coefficient obtained using the simplified expressions agrees with experimental results. This suggests a method for the correction of the values of K and S with changes in pigment particle size.  相似文献   
68.
Production of protein and volatile fatty acids by anaerobic digestion of blackstrap molasses was investigated. This protein may have potential as a feed for animals (and, we hope, for humans) in the near future. Volatile fatty acids can be further fermented to produce methane. Fermentation of molasses byEubacterium ruminantium was studied in a chemostat at a constant temperature of 37 C. This study focused on kinetics of growth of the pure culture. The maximum rate of protein production of about 0.326 g/l/hr was obtained when the pH and retention times were 6.2 and between 5 and 7 hrs, respectively. Average cell yield was 12.6% and carbohydrate conversion was 82 to 99%. Volatile fatty acids also were produced, with acetic acid and n-butyric acid being the predominant products. Two different kinetic models were used to fit the experimental data. The kinetic parameters obtained for the Monod model were: μmax=0.207 (1/hr); ks=0.165 g/l.  相似文献   
69.
This study investigated five different trace organic contaminants (TOrCs) (one hormone: 17α‐ethinylestradiol (EE2), two pharmaceuticals: salicylic acid (SA) and trimethoprim (TMP), one analgesic drug: carbamazepine (CBZ), and one surfactant metabolite: nonylphenol (NP)) removal efficiency at a full‐scale Advanced Wastewater Treatment Plant (AWTP). The AWTP achieved average EE2, SA and NP removal over 80% at the biological carbon removal stages. The results also showed a 66% removal of TMP at the nitrogen removal stages. CBZ was recalcitrant throughout the plant, due to its high solubility and low distribution coefficient between wastewater and sludge. Batch experiments were conducted on active and inactive secondary, nitrification and denitrification sludge by adding TOrCs to understand the removal mechanism through sorption and biodegradation. Sorption was the dominant mechanism to remove EE2, SA and NP in secondary treatment processes. In nitrification and denitrification processes, higher percentage of TOrCs removal through biodegradation were observed compared to removal through sorption.  相似文献   
70.
Fortified probiotic Greek dahi was formulated with pomegranate pulp (PP) and flaxseed powder (FP). The product variables, viz. PP, FP and incubation time, were optimised based on chemical, sensory and textural attributes. The study revealed that PP significantly affected the acidity and antioxidant content, while FP influenced the sensory and textural properties of the product. The optimum conditions were 15% PP, 2% FP and 12‐h incubation time. The developed fortified probiotic Greek dahi is a potential synbiotic food.  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