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   108342篇
  免费   11247篇
  国内免费   6222篇
电工技术   8142篇
技术理论   3篇
综合类   8530篇
化学工业   16268篇
金属工艺   6617篇
机械仪表   7683篇
建筑科学   8997篇
矿业工程   3785篇
能源动力   3127篇
轻工业   7297篇
水利工程   2436篇
石油天然气   5352篇
武器工业   1122篇
无线电   12979篇
一般工业技术   11839篇
冶金工业   4296篇
原子能技术   1238篇
自动化技术   16100篇
  2024年   258篇
  2023年   1566篇
  2022年   3230篇
  2021年   4616篇
  2020年   3510篇
  2019年   2842篇
  2018年   3150篇
  2017年   3505篇
  2016年   3207篇
  2015年   4879篇
  2014年   5852篇
  2013年   7028篇
  2012年   8043篇
  2011年   8379篇
  2010年   7739篇
  2009年   7530篇
  2008年   7264篇
  2007年   6977篇
  2006年   6386篇
  2005年   5406篇
  2004年   3761篇
  2003年   3308篇
  2002年   3298篇
  2001年   2940篇
  2000年   2229篇
  1999年   2001篇
  1998年   1258篇
  1997年   1116篇
  1996年   975篇
  1995年   785篇
  1994年   634篇
  1993年   496篇
  1992年   366篇
  1991年   288篇
  1990年   234篇
  1989年   192篇
  1988年   155篇
  1987年   88篇
  1986年   84篇
  1985年   39篇
  1984年   35篇
  1983年   19篇
  1982年   25篇
  1981年   20篇
  1980年   25篇
  1979年   14篇
  1978年   8篇
  1976年   7篇
  1959年   9篇
  1951年   14篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
71.
为了提高设计创新效率,本研究基于心理图式提出了国庆彩车的设计程序与方法。研究按照浅层、中层和深层的次序递进,设计心理图式划分为“造型图式”“叙事与动作图式”以及“人物和情感图式”的基本类别,并提出了综合性、时态性、差异性和集体性四类基本属性。而后结合新中国成立70周年彩车设计,对不同心理图式的应用方法和属性进行了案例分析。本文所提出的方法在设计实践中得到了实证,具有一定的实用价值。  相似文献   
72.
73.
74.
“Smart firefighting” construction as a part of the “smart city” has been a concern of the public security and fire agencies at all levels. In this study, the status, problems, and reflections of “smart firefighting” construction in China are discussed. A recent survey indicates that China has launched its smart firefighting construction and initially created a new perspective on its regional smart firefighting work based on three main aspects: intelligent disaster perception by Internet of Things (IoT) construction, intelligent disaster prevention by big data construction, and intelligent disaster disposal by emergency rescue platform construction. However, the current smart firefighting construction in China still has some prominent problems such as the data interconnectivity and normalized management of various platforms, the extensibility of smart firefighting platforms, and the intelligent level of smart firefighting researches, which need to be solved urgently. Therefore, we argue that smart firefighting construction in China should establish data interconnectivity, industrial normalized management, 2D/3D geographic information interaction and extension, high-integration fire protection theory, and many other aspects in the near future and truly realize firefighting visualization and efficient data applications for 4D time space. This study could provide valuable reference for smart firefighting and smart city construction.  相似文献   
75.
This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al2O3 nanostructured composite materials doped with Cr3C2/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr3C2/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al2O3 composites. Al2O3 crack deflection, transgranular Al2O3, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties.  相似文献   
76.
目的: 建立快速灵敏的LC-MS/MS法测定人血浆中阿莫西林浓度,并用于两种阿莫西林胶囊的一致性评价。方法: 采用岛津公司LCMS-8060型LC-MS/MS仪,以MRM模式测定阿莫西林(m/z 366.00/114.00)的浓度,d4-阿莫西林作内标(m/z 370.10/114.05),离子源为ESI源。色谱柱选用Waters ACQUITY BEH C18(2.1×50 mm,1.7 μm),梯度洗脱。血浆样本加入内标,经甲醇沉淀蛋白后取上清液进样检测。结果: 所建方法经验证,其线性、准确度、精密度、最低定量限、提取回收率、特异性、基质效应、稳定性等各项指标均符合CFDA的指导原则及最新核查标准要求,并较文献报道中的方法有处理简单、灵敏度高、色谱峰形好的优点。结论: 所建方法快速、灵敏,适用于人血浆中阿莫西林浓度的检测。用于一致性评价的样本实测,两种制剂生物等效。  相似文献   
77.
The increased concentration of CO2 due to continuous breathing and no discharge of human beings in the manned closed space, like spacecraft and submarines, can be a threat to health and safety. Effective removal of low concentration CO2 from the manned closed space is essential to meet the requirements of long-term space or deep-sea exploration, which is an international frontier and trend. Ionic liquids (ILs), as a widespread and green solvent, already showed its excellent performance on CO2 capture and absorption, indicating its potential application in low concentration CO2 capture. In this review, we first summarized the current methods and strategies for direct capture from low concentration CO2 in both the atmosphere and manned closed spaces. Then, the multi-scale simulation methods of CO2 capture by ionic liquids are described in detail, including screening ionic liquids by COSMO-RS methods, capture mechanism by density functional theory and molecular dynamics simulation, and absorption process by computational fluid dynamics simulation. Lastly, some typical IL-based green technologies for low concentration CO2 capture, such as functionalized ILs, co-solvent systems with ILs, and supported materials based on ILs, are introduced, and analyzed the subtle possibility in manned closed spaces. Finally, we look forward to the technology and development of low concentration CO2 capture, which can meet the needs of human survival in closed space and proposed that supported materials with ionic liquids have great advantages and infinite possibilities in the vital area.  相似文献   
78.
He  Yong  Li  Zhen  Zhang  Ke-neng  Ye  Wei-min  Chen  Yong-gui 《Mine Water and the Environment》2020,39(1):103-111

Laboratory tests, including compressibility, permeability, and microstructure tests, were conducted on tailings samples using custom-designed test apparatus to investigate the effect of metal contamination (Cu2+) on the hydromechanical behavior of compacted tailings. Infiltrating samples with various dry densities with distilled water or CuSO4 solution at various concentrations showed that the void ratio of compacted tailings decreased with increased dry density. An increase in the metal contaminant concentrations from 0 to 0.1 mol/L increased the compression coefficient of the tailings from 0.14 to 0.84 MPa?1 under a vertical load of 0.01 to 2.0 MPa, while the yield stress of the tailings decreased from 204.3 to 98.7 kPa, respectively. The linear relationship between permeability coefficient (k) and void ratio (e) is described by k?=???6.48?+?17.17e. Microstructure test results showed that the diffusion double layer thinned, and the surface potential decreased, indicating that the contaminant of Cu2+ enhanced the compressibility and permeability of the tailings. The microstructure test results also showed that the amount of fine-grained soil in the copper tailings was significantly less after the hydromechanical test. Therefore, the permeability and compressibility of copper tailings increased. The experimental results are in good agreement with the estimated results.

  相似文献   
79.
介绍了PET熔体长距离输送工艺流程,重点分析易对PET熔体输送带来不利影响的因素,如熔体压力降、停留时间、管道粗糙度、焊缝品质等,并针对熔体输送的不利因素,提出了相应的解决方案,对熔体直纺设计、实践提供必要的参考。  相似文献   
80.
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