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   284871篇
  免费   24084篇
  国内免费   12794篇
电工技术   17221篇
技术理论   25篇
综合类   19700篇
化学工业   46191篇
金属工艺   16491篇
机械仪表   18597篇
建筑科学   22218篇
矿业工程   9238篇
能源动力   7918篇
轻工业   19428篇
水利工程   5178篇
石油天然气   18512篇
武器工业   2399篇
无线电   31456篇
一般工业技术   32473篇
冶金工业   14757篇
原子能技术   3128篇
自动化技术   36819篇
  2024年   939篇
  2023年   4612篇
  2022年   7659篇
  2021年   11598篇
  2020年   9064篇
  2019年   7442篇
  2018年   8371篇
  2017年   9419篇
  2016年   8383篇
  2015年   11469篇
  2014年   14793篇
  2013年   17401篇
  2012年   19121篇
  2011年   20490篇
  2010年   18246篇
  2009年   17049篇
  2008年   16604篇
  2007年   15974篇
  2006年   15851篇
  2005年   13592篇
  2004年   9293篇
  2003年   7648篇
  2002年   6790篇
  2001年   5960篇
  2000年   6394篇
  1999年   7102篇
  1998年   5758篇
  1997年   4738篇
  1996年   4453篇
  1995年   3708篇
  1994年   2948篇
  1993年   2080篇
  1992年   1614篇
  1991年   1274篇
  1990年   969篇
  1989年   776篇
  1988年   573篇
  1987年   342篇
  1986年   279篇
  1985年   193篇
  1984年   144篇
  1983年   101篇
  1982年   124篇
  1981年   109篇
  1980年   87篇
  1979年   44篇
  1978年   26篇
  1977年   22篇
  1976年   36篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
81.
Abstract

Different drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of chicken powders. The hygroscopicity curves and glass transition temperature were used to evaluate the influence of ambient humidity and temperature on moisture absorption of powders. The results showed that the chicken powder dried by MVD had the lowest moisture absorption, followed by IFVD, VD, and SD. The hygroscopicity of SD chicken powders was different from other three kinds of chicken powders due to the physical properties of particles and the changes of protein secondary structure as detected by the Fourier transform-infrared spectrometer. For the three vacuum drying methods, the difference of protein secondary structure was the main reason of differences in hygroscopicity. Although MVD chicken powders were slightly inferior to SD chicken powders in taste, MVD chicken powders were the best in terms of smell and color as suggested by instrumental sensory parameter evaluations. It was found that MVD had a positive effect on reducing moisture absorption and maintaining sensory quality of chicken powders.  相似文献   
82.
基于物联网的智慧林业可持续发展策略研究   总被引:1,自引:0,他引:1  
随着我国科技的不断进步,在“互联网+”大数据的背景下,林业的智慧化发展是必经之路。虽然我国智慧林业的发展已经取得了一定的突破,但是仍然存在着许多问题。基于此,文章在物联网技术的基础上,对智慧林业的可持续发展策略进行探讨。  相似文献   
83.
Yan  Jing  Zhu  Rongying  Wu  Fan  Zhao  Ziyin  Ye  Huan  Hou  Mengying  Liu  Yong  Yin  Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally...  相似文献   
84.
Chi  Yaxiong  Liu  Jing 《Natural computing》2019,18(2):301-312

Reconstructing gene regulatory networks (GRNs) plays an important role in identifying the complicated regulatory relationships, uncovering regulatory patterns in cells, and gaining a systematic view for biological processes. In order to reconstruct large-scale GRNs accurately, in this paper, we first use fuzzy cognitive maps (FCMs), which are a kind of cognition fuzzy influence graphs based on fuzzy logic and neural networks, to model GRNs. Then, a novel hybrid method is proposed to reconstruct GRNs from time series expression profiles using memetic algorithm (MA) combined with neural network (NN), which is labeled as MANNFCM-GRN. In MANNFCM-GRN, the MA is used to determine regulatory connections in GRNs and the NN is used to determine the interaction strength of the regulatory connections. In the experiments, the performance of MANNFCM-GRN is validated on both synthetic data and the benchmark dataset DREAM3 and DREAM4. The experimental results demonstrate the efficacy of MANNFCM-GRN and show that MANNFCM-GRN can reconstruct GRNs with high accuracy without expert knowledge. The comparison with existing algorithms also shows that MANNFCM-GRN outperforms ant colony optimization, non-linear Hebbian learning, and real-coded genetic algorithms.

  相似文献   
85.
Chen  Meng  Yu  Xiaohui  Liu  Yang 《World Wide Web》2019,22(6):2901-2920
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each...  相似文献   
86.
87.
88.
89.
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry  相似文献   
90.
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings.  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