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   344篇
  免费   3篇
  国内免费   1篇
电工技术   2篇
综合类   1篇
化学工业   90篇
金属工艺   5篇
机械仪表   7篇
建筑科学   10篇
能源动力   12篇
轻工业   40篇
水利工程   3篇
石油天然气   14篇
无线电   42篇
一般工业技术   60篇
冶金工业   23篇
原子能技术   1篇
自动化技术   38篇
  2023年   2篇
  2022年   10篇
  2021年   19篇
  2020年   12篇
  2019年   14篇
  2018年   24篇
  2017年   8篇
  2016年   10篇
  2015年   5篇
  2014年   7篇
  2013年   28篇
  2012年   12篇
  2011年   25篇
  2010年   18篇
  2009年   17篇
  2008年   15篇
  2007年   16篇
  2006年   10篇
  2005年   6篇
  2004年   4篇
  2003年   6篇
  2002年   4篇
  2001年   5篇
  2000年   1篇
  1999年   5篇
  1998年   9篇
  1997年   4篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1993年   5篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1980年   6篇
  1979年   2篇
  1978年   1篇
  1976年   3篇
  1975年   6篇
  1974年   1篇
  1973年   3篇
  1971年   2篇
  1970年   2篇
排序方式: 共有348条查询结果,搜索用时 0 毫秒
1.
The reaction of 5-arylidene-4-arylimino-2-thiazolidinones 4 with GRIGNARD reagents effected 1,4-addition to the exocyclic  CC bond with the formation of 5 . Alkylation of the arylidene derivatives 4 with diazomethane or methyl iodide results in the formation of the N-methyl derivatives 6 . Treatment of 6 with phenylmagnesium bromide effects addition of the reagent to the double bond of the lateral chain to yield products, proved to have structure 8 . The 5-arylazo derivatives 9 of 4-arylimino-2-thiazolidinones were obtained by coupling 4 with aromatic diazonium chlorides. Compounds 9 were N-methylated with diazomethane to yield 10 .  相似文献   
2.
4-Arylidene-2-phenyl-1-substituted-2-imidazolin-5-ones 1a – d react with organomagnesium compounds, in ether at room temperature, to yield, as the main isolable products, the 4-disubstituted-methyl derivatives 2a – h . On the other hand, 1a – d react with phenylmagnesium bromide in a boiling ether-benzene mixture to give, among the reaction products, 2a – d and the 4-diarylmethylene derivatives 3a – d . Spectral data of 2 and 3 are discussed. Treatment of the GRIGNARD products 2a – c with formaldehyde and piperidine or morpholine effects aminomethylation at C-4 with the formation of the MANNICH bases 6a – f .  相似文献   
3.
We present a novel Partial Virtual channel Sharing (PVS) NoC architecture which reduces the impact of faults on performance and also tolerates faults within the routing logic. Without PVS, failure of a component impairs the fault-free connected components, which leads to considerable performance degradation. Improving resource utilization is key in enhancing or sustaining performance with minimal overhead when faults or overload occurs. In the proposed architecture, autonomic virtual-channel buffer sharing is implemented with a novel algorithm that determines the sharing of buffers among a set of ports. The runtime allocation of the buffers depends on incoming load and fault occurrence. In addition, we propose an efficient technique for maintaining the accessibility of a processing element (PE) to the network even if its router is faulty. Our techniques can be used in any NoC topology and for both, 2D and 3D NoCs. The synthesis results for an integrated video conference application demonstrate 22 % reduction in average packet latency compared to state-of-the-art virtual channel (VC) based NoC architecture. Extensive quantitative simulation has been carried out with synthetic benchmarks. Simulation results reveal that the PVS architecture improves the performance significantly in presence of faults, compared to other VC-based NoC architectures.  相似文献   
4.
The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice‐treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat‐treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi‐prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry  相似文献   
5.
Abstract Production of fish fingers was achieved by using fish species such as sardine (Sardina pilchardus, Walbaum, 1792), whiting (Merlangius merlangus, Linnaeus, 1758) and pike perch (Sander lucioperca, Linnaeus, 1758). Quality changes of battered fish patties during a period of 8 months at –18 °C were investigated. According to the results of microbiological and chemical analysis, fish fingers were found to be within acceptable limits during frozen storage for 8 months. However, sensory analysis showed that, at the end of the frozen storage, fish fingers made from sardine could not be consumed because of rancidity.  相似文献   
6.
The structure and surface morphology of Ni-incorporated diamond like carbon (Ni:DLC) films have been investigated. These films were deposited on Si substrates using pulsed laser deposition (PLD) technique. A KrF Excimer laser (λ = 248 nm) was used for co-ablation from multi component Ni–graphite target. The concentration of Ni was varied by ablating the Ni part of the target with various numbers of laser pulses. The SEM and AFM analysis reveals that the surface is composed of segregates of Ni which increases with the increase in Ni content during the growth process. The structural investigations by XRD and Raman spectroscopy provided information about the orientation of the incorporated constituent and the ordering of the carbon species. Maximum height of the nano structures which were observed on the surface was ∼50 nm. The G-peak of the graphite was shifted towards higher wave number due to enhancement in SP2 sites which have been increased due to the increase in the Ni concentration. A small change in the surface roughness ranging from 7.78 nm to 13.1 nm due to increased Ni concentration was also observed.  相似文献   
7.

Internet of Things (IoT) is changing the way many sectors operate and special attention is paid to promoting healthy living by employing IoT based technologies. In this paper, a novel approach is developed with IoT prototype of Wireless Sensor Network and Cloud based system to provide continuous monitoring of a patient’s health status, ensuring timely scheduled and unscheduled medicinal dosage based on real-time patient vitals measurement, life-saving emergency prediction and communication. The designed integrated prototype consists of a wearable expandable health monitoring system, Smart Medicine Dispensing System, Cloud-based Big Data analytical diagnostic and Artificial Intelligence (AI) based reporting tool. A working prototype was developed and tested on few persons to ensure that it is working according to expected standards. Based on the initial experiments, the system fulfilled intended objectives including continuous health monitoring, scheduled timely medication, unscheduled emergency medication, life-saving emergency reporting, life-saving emergency prediction and early stage diagnosis. In addition, based on the analysis reports, physicians can diagnose/decide, view medication side effects, medication errors and prescribe medication accordingly. The proposed system exhibited the ability to achieve objectives it was designed using IoT to alleviate the pressure on hospitals due to crowdedness in hospital care and to reduce the healthcare service delays.

  相似文献   
8.
Propylsulfonic acid-functionalized partially crystalline silicalite-1 materials were synthesized via one step co-condensation technique by varying the molar ratio of organosilane source, 3-mercaptopropyltrimethoxysilane (3MP) to tetraethylorthosilicate (TEOS) in the range of 0.05–0.30, and subsequent oxidation of thiol group to propylsulfonic acid using hydrogen peroxide (H2O2). These materials were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption method. The structure of these materials was determined by Fourier transform infrared spectroscopy (FT-IR) and 29Si and 13C solid state NMR. XRD results show that % crystallinity of the materials decreased with the increase in 3MP concentration in the synthesis mixture. Selected area electron diffraction (SAED) showed the presence of crystalline and amorphous phases in the samples. An amorphous phase was formed when 3MP concentration was 30 mol% of the total silica source. After elimination of the structure directing agent (SDA) by calcination at 420 °C, thermogravimetric analysis (TGA) shows that the structure was thermally stable up to 550 °C. Ammonia temperature-programmed desorption (NH3-TPD) shows that the acid capacity of these materials was in the range of 1.19–1.83 mmol H+/g, which shows that these materials could be used as potential heterogeneous acid catalyst.  相似文献   
9.
In this article, time–frequency representation of Wigner–Ville is used to analyse the acoustic signal backscattered by a thin elastic tube of radii ratio b/a. This analysis allows to determine the reduced cutoff frequency of the circumferential antisymmetric wave A1 propagating around the tube. The evolution of this reduced cutoff frequency in function of b/a is reported. The values obtained of reduced cutoff frequency are compared to the values computed from the proper modes method.  相似文献   
10.
ABSTRACT

A model study on the hydrodesulphurization of dimethyl sulphide, di n-prophyl sulphide, di n-butyl sulphide and dimethyl disulphide on Co-Mo-A12O3 surface was conducted using stopped-flow chromatographic technique. The plots for the rates of hydrocarbon formation agreed well with the first order reaction at the surface of the catalyst.

Activation energies for the hydrodesulphurization of (C2H5)2S, (C3H7)2S, n-(C4H9)2S and (CH3)2S2 are 57.55, 70.67, 72.74 and 37.80 Kj mole?1 respectively.  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