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   27693篇
  免费   2843篇
  国内免费   1635篇
电工技术   2167篇
技术理论   3篇
综合类   1796篇
化学工业   4366篇
金属工艺   1608篇
机械仪表   1461篇
建筑科学   2031篇
矿业工程   578篇
能源动力   912篇
轻工业   2113篇
水利工程   488篇
石油天然气   815篇
武器工业   278篇
无线电   3008篇
一般工业技术   3861篇
冶金工业   1599篇
原子能技术   272篇
自动化技术   4815篇
  2024年   88篇
  2023年   494篇
  2022年   763篇
  2021年   1307篇
  2020年   983篇
  2019年   747篇
  2018年   841篇
  2017年   942篇
  2016年   920篇
  2015年   1066篇
  2014年   1366篇
  2013年   2018篇
  2012年   2021篇
  2011年   2160篇
  2010年   1822篇
  2009年   1681篇
  2008年   1800篇
  2007年   1719篇
  2006年   1501篇
  2005年   1225篇
  2004年   984篇
  2003年   871篇
  2002年   934篇
  2001年   778篇
  2000年   524篇
  1999年   404篇
  1998年   256篇
  1997年   261篇
  1996年   225篇
  1995年   202篇
  1994年   184篇
  1993年   142篇
  1992年   117篇
  1991年   86篇
  1990年   84篇
  1989年   79篇
  1988年   65篇
  1987年   33篇
  1986年   43篇
  1985年   43篇
  1984年   43篇
  1983年   28篇
  1982年   33篇
  1981年   44篇
  1980年   28篇
  1979年   27篇
  1978年   25篇
  1976年   18篇
  1974年   21篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 37 毫秒
1.
黄科  袁启平  董薇  孙沂昆  亢勇  王天翔 《电视技术》2021,45(10):129-135
恶意代码数量已经呈现爆炸式增长,对于恶意代码的检测防护显得尤为重要.近几年,基于深度学习的恶意代码检测方法开始出现,基于此,提出一种新的检测方法,将恶意代码二进制文件转化为十进制数组,并利用一维卷积神经网络(1 Dimention Convolutional Neural Networks,1D CNN)对数组进行分类和识别.针对代码家族之间数量不平衡的现象,该算法选择在分类预测上表现良好的XGBoost,并对Vision Research Lab中的25个不同恶意软件家族的9458个恶意软件样本进行了实验.实验结果表明,所提的方法分类预测精度达到了97%.  相似文献   
2.
3.
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased.  相似文献   
4.
Titanium and boron are simultaneously introduced into LiNi0.8Co0.1Mn0.1O2 to improve the structural stability and electrochemical performance of the material. X-ray diffraction studies reveal that Ti4+ ion replaces Li+ ion and reduces the cation mixing; B3+ ion enters the tetrahedron of the transition metal layers and enlarges the distance of the [LiO6] layers. The co-doped sample has spherical secondary particles with elongated and enlarged primary particles, in which Ti and B elements distribute uniformly. Electrochemical studies reveal the co-doped sample has improved rate performance (183.1 mAh·g-1 at 1 C and 155.5 mAh·g-1 at 10 C) and cycle stability (capacity retention of 94.7% after 100 cycles at 1 C). EIS and CV disclose that Ti and B co-doping reduces charge transfer impedance and suppresses phase change of LiNi0.8Co0.1Mn0.1O2.  相似文献   
5.
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic...  相似文献   
6.
7.
Multimedia Tools and Applications - Changes in appearance present a tremendous problem for the visual localization of an autonomous vehicle in outdoor environments. Data association between the...  相似文献   
8.
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   
9.
田华  孙瑞  宋春风  邓帅  石凌峰  康克  舒歌群 《化工进展》2020,39(7):2884-2892
CO2捕集作为温室气体排放控制的有效手段已成为重要研究课题。作为新兴捕集技术之一,低温CO2捕集因产品纯度高、无附加污染等优势受到关注。然而,该技术能耗和捕集率对于气体中CO2浓度十分敏感,对于高CO2浓度气体可获得较高的CO2捕集率和较低能耗水平。基于此,本文提出了耦合膜分离的新型CO2低温捕集系统,通过膜材料选择渗透性实现待捕集气体CO2浓度主动调控,并在最优浓度下进行CO2低温捕集。首先基于不同传统低温捕集系统特点,对比分析了不同耦合系统模式,从而确定了最优耦合系统结构。针对最优耦合系统进行了运行参数优化,并分别基于实现系统捕集能耗最低与捕集率最高的目标,获得了膜渗透侧CO2浓度与进气CO2浓度间的关系式,为该耦合系统中膜组件选型提供指导。研究表明,本文提出的耦合系统捕集能耗为1.92MJ/kgCO2,相比于传统单一低温系统捕集能耗可降低16.5%。  相似文献   
10.
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