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   327897篇
  免费   20960篇
  国内免费   10529篇
电工技术   14521篇
技术理论   29篇
综合类   17537篇
化学工业   53228篇
金属工艺   18807篇
机械仪表   18679篇
建筑科学   21443篇
矿业工程   8719篇
能源动力   8018篇
轻工业   18456篇
水利工程   5212篇
石油天然气   18097篇
武器工业   1785篇
无线电   36192篇
一般工业技术   45022篇
冶金工业   16219篇
原子能技术   2721篇
自动化技术   54701篇
  2024年   1012篇
  2023年   4081篇
  2022年   7015篇
  2021年   9863篇
  2020年   7753篇
  2019年   6567篇
  2018年   20586篇
  2017年   20523篇
  2016年   16559篇
  2015年   10291篇
  2014年   12605篇
  2013年   14791篇
  2012年   18695篇
  2011年   26026篇
  2010年   22521篇
  2009年   19110篇
  2008年   20013篇
  2007年   20500篇
  2006年   13692篇
  2005年   12922篇
  2004年   8994篇
  2003年   7972篇
  2002年   6681篇
  2001年   5534篇
  2000年   6131篇
  1999年   7066篇
  1998年   5934篇
  1997年   4802篇
  1996年   4557篇
  1995年   3784篇
  1994年   3079篇
  1993年   2137篇
  1992年   1671篇
  1991年   1331篇
  1990年   1007篇
  1989年   788篇
  1988年   584篇
  1987年   357篇
  1986年   289篇
  1985年   200篇
  1984年   145篇
  1983年   108篇
  1982年   135篇
  1981年   104篇
  1980年   76篇
  1968年   48篇
  1966年   43篇
  1965年   48篇
  1955年   64篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
61.
62.
Treating neuroinflammation-related injuries and disorders through manipulation of neuroinflammation functions is being heralded as a new therapeutic strategy. In this study, a novel pectic galactan (PG) polysaccharide based gene therapy approach is developed for targeting reactive gliosis in neuroinflammation. Galectin-3 (Gal-3) is a cell protein with a high affinity to β-galactoside sugars and is highly expressed in reactive gliosis. Since PG carries galactans, it can target reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 on the cell membrane, and therefore can be utilized as a carrier for delivering genes to these cells. The carrier is synthesized by modifying quaternary ammonium groups on the PG. The resulting quaternized PG (QPG) is found to form complexes with plasmid DNA with a mean diameter of 100 nm and have the characteristics required for targeted gene therapy. The complexes efficiently condense large amounts of plasmid per particle and successfully bind to Gal-3. The in vivo study shows that the complexes are biocompatible and safe for administration and can selectively transfect reactive glial cells of an induced cortical lesion. The results confirm that this PG-based delivery system is a promising platform for targeting Gal-3 overexpressing neuroinflammation cells for treating neuroinflammation-related injuries and neurodegenerative diseases.  相似文献   
63.
64.
65.
Vacuum casting is one of the widely used methods for small-volume production of plastic parts. The main challenge of this method is to choose the optimal w  相似文献   
66.
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   
67.
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   
68.
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   
69.
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   
70.
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   
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