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   536篇
  免费   14篇
  国内免费   8篇
电工技术   45篇
综合类   2篇
化学工业   117篇
金属工艺   13篇
机械仪表   5篇
建筑科学   10篇
能源动力   25篇
轻工业   23篇
水利工程   2篇
石油天然气   4篇
无线电   116篇
一般工业技术   98篇
冶金工业   42篇
原子能技术   6篇
自动化技术   50篇
  2023年   13篇
  2022年   12篇
  2021年   17篇
  2020年   10篇
  2019年   15篇
  2018年   14篇
  2017年   8篇
  2016年   18篇
  2015年   6篇
  2014年   10篇
  2013年   39篇
  2012年   15篇
  2011年   28篇
  2010年   27篇
  2009年   18篇
  2008年   14篇
  2007年   16篇
  2006年   10篇
  2005年   7篇
  2004年   8篇
  2003年   12篇
  2002年   13篇
  2001年   4篇
  2000年   10篇
  1999年   9篇
  1998年   20篇
  1997年   22篇
  1996年   10篇
  1995年   8篇
  1994年   8篇
  1993年   7篇
  1992年   11篇
  1991年   5篇
  1990年   4篇
  1988年   11篇
  1987年   7篇
  1985年   8篇
  1984年   8篇
  1983年   7篇
  1982年   4篇
  1981年   7篇
  1980年   6篇
  1979年   6篇
  1978年   6篇
  1977年   4篇
  1976年   11篇
  1975年   3篇
  1973年   3篇
  1971年   3篇
  1966年   3篇
排序方式: 共有558条查询结果,搜索用时 171 毫秒
81.
Water Resources Management - The aim of this article is to determine how human interventions in upstream countries coupled with drought events are affecting the flow regime of downstream countries...  相似文献   
82.
Abstract

Diazotized sulfadiazine derivative (1) was coupled with some nitrogen heterocyclic namely (thiazolone derivatives 2a–c, thiazole derivatives 4a–c and barbituric acid derivatives 6a,b) to give the corresponding azo compounds 3a–c, 5a–c and 7a,b in good yields. The newly synthesized azo benzene sulfonamide dyes were recorded their UV visible spectra in the region 200–600?nm in four different solvents and discussed the effect of solvents, substituent and effect of acid and base on the absorption values of these dyes.  相似文献   
83.
JOM - Nanofibers were prepared from a poly(acrylonitrile-co-vinyl acetate) [P(AN-co-VAC)]/polyvinylidene fluoride (PVDF) blend and used as a quasi-solid (QS) electrolyte for dye-sensitized solar...  相似文献   
84.
85.
Ru(II) polypyridyl complexes are compounds of great interest in cancer therapy due to their unique photophysical, photochemical, and biological properties. For effective treatment, they must be able to penetrate tumor cells effectively and selectively. The development of nanoscale carriers capable of delivering Ru(II) polypyridyl complexes has the potential to passively or selectively enhance their cellular uptake in tumor cells. Many different strategies have been explored to incorporate Ru(II) polypyridyl complexes into a variety of nanosized constructs, ranging from organic to inorganic materials. Herein, recent developments in nanomaterials loaded with Ru(II) polypyridyl complexes are highlighted. Their rational design, preparation, and physicochemical properties are described, and their potential applications in cancer therapy are eventually discussed.  相似文献   
86.
Novel membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from Rice Husk (RH), Glutaraldehyde (GLA) and Glycerine (G) were manufactured by the compression moulding process. Rice husk is a new source to isolate pure cellulose nanocrystals via mechanical and chemical treatment. The biodegradability of the membranes has been evaluated using UV accelerated weathering as well as a soil burial test. The morphology of membranes (PVA/RH-CNCs) was characterized by using the Scanning Electron Microscope (SEM). The chemical structure of the membranes (PVA/RH-CNCs) was characterised by Fourier-Transformation Infrared (FTIR) spectroscopy as well as wide-angle X-ray diffraction. The mechanical properties of the membranes were evaluated using standard techniques. Swelling and weight loss resulting from biodegradation were also evaluated. The results showed that the developed transient membranes can be used as food packaging bags owing to biodegradability (weight loss) under irradiation and during soil burial.  相似文献   
87.
Moustafa  S.F.  Soliman  F.A. 《Tribology Letters》1997,3(4):311-315
The wear behaviour of Al-4% Cu alloy and its composite containing-type alumina fibres has been studied at roomtemperature and at 150°C, using a standard pin-on-ringtribometer. The results show higher wear resistance and a lowercoefficient of friction for the composite material as comparedwith the matrix alloy. Three wear mechanisms of the matrix alloytested at room temperature were observed: oxidation-induceddelamination, seizure and subsequent wear due to surfacemelting. At 150°C, however, the matrix wear is due toseizure and melting. In the case of the composite material,different wear mechanisms were found: at low loads, oxidation-induced delamination was predominant, changing to high-strain-induced delamination at higher loads up to 80 N; at high loads(beyond 120 N) sub-surface delamination was the prevailingmechanism.  相似文献   
88.
In 5G cloud computing, the most notable and considered design issues are the energy efficiency and delay. The majority of the recent studies were dedicated to optimizing the delay issue by leveraging the edge computing concept, while other studies directed its efforts towards realizing a green cloud by minimizing the energy consumption in the cloud. Active queue management‐based green cloud model (AGCM) as one of the recent green cloud models reduced the delay and energy consumption while maintaining a reliable throughput. Multiaccess edge computing (MEC) was established as a model for the edge computing concept and achieved remarkable enhancement to the delay issue. In this paper, we present a handoff scenario between the two cloud models, AGCM and MEC, to acquire the potential gain of such collaboration and investigate its impact on the cloud fundamental constraints; energy consumption, delay, and throughput. We examined our proposed model with simulation showing great enhancement for the delay, energy consumption, and throughput over either model when employed separately.  相似文献   
89.
Calcium nano ferrite with composition CaGdxEryFe2?x?yO4 (x?=?y?=?0.0, x?=?0.025, y?=?0.05) was prepared by citrate gel auto combustion method. The prepared samples showed orthorhombic phase structure and the crystallite sizes were found in the range of 32.1–35.3 nm. Detailed observation via the Field Emission Scanning Electron Microscopy (FESEM) showed that the calcium ferrite nano-particles were spherical and capsule like formation shape. The hysteresis loop confirms the magnetic behavior of the investigated samples, which is then discussed on the basis of super exchange interactions. Magnetic parameters such as saturation magnetization, coercivity, and retentivity were obtained. Greater than six-fold increase in coercivity (≈2085 Oe) was observed in calcium nanoferrites compared to the doped samples (≈360 Oe). The CaFe2O4-type structure includes edge- and corner sharing BO6 octahedral, constituting a very unique network similar to perovskite-related nanoparticles. This structural network leads to an improvement in the physical properties of the investigated samples. Great efforts have been made to synthesize pure nanoferrite samples without any secondary phases even after the substitution of low soluble rare earth ions. Special attention should be given to calcium ferrite nanoparticles which are suitable candidates to be used in the manufacturing of bone-like scaffolds, hyperthermia treatment of cancer and biological activity.  相似文献   
90.
Realism rendering methods of outdoor augmented reality (AR) is an interesting topic. Realism items in outdoor AR need advanced impacts like shadows, sunshine, and relations between unreal items. A few realistic rendering approaches were built to overcome this issue. Several of these approaches are not dealt with real-time rendering. However, the issue remains an active research topic, especially in outdoor rendering. This paper introduces a new approach to accomplish reality real-time outdoor rendering by considering the relation between items in AR regarding shadows in any place during daylight. The proposed method includes three principal stages that cover various outdoor AR rendering challenges. First, real shadow recognition was generated considering the sun’s location and the intensity of the shadow. The second step involves real shadow protection. Finally, we introduced a shadow production algorithm technique and shades through its impacts on unreal items in the AR. The selected approach’s target is providing a fast shadow recognition technique without affecting the system’s accuracy. It achieved an average accuracy of 95.1% and an area under the curve (AUC) of 92.5%. The outputs demonstrated that the proposed approach had enhanced the reality of outside AR rendering. The results of the proposed method outperformed other state-of-the-art rendering shadow techniques’ outcomes.  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