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   2189篇
  免费   60篇
  国内免费   3篇
电工技术   28篇
综合类   2篇
化学工业   471篇
金属工艺   88篇
机械仪表   45篇
建筑科学   32篇
矿业工程   1篇
能源动力   137篇
轻工业   109篇
水利工程   17篇
石油天然气   8篇
无线电   300篇
一般工业技术   445篇
冶金工业   221篇
原子能技术   25篇
自动化技术   323篇
  2023年   15篇
  2022年   26篇
  2021年   38篇
  2020年   20篇
  2019年   40篇
  2018年   53篇
  2017年   41篇
  2016年   54篇
  2015年   41篇
  2014年   53篇
  2013年   127篇
  2012年   86篇
  2011年   119篇
  2010年   106篇
  2009年   93篇
  2008年   95篇
  2007年   96篇
  2006年   83篇
  2005年   66篇
  2004年   49篇
  2003年   50篇
  2002年   50篇
  2001年   40篇
  2000年   38篇
  1999年   46篇
  1998年   79篇
  1997年   67篇
  1996年   45篇
  1995年   45篇
  1994年   46篇
  1993年   32篇
  1992年   43篇
  1991年   41篇
  1990年   26篇
  1989年   30篇
  1988年   16篇
  1987年   13篇
  1986年   12篇
  1985年   22篇
  1984年   22篇
  1983年   28篇
  1982年   27篇
  1981年   21篇
  1980年   16篇
  1979年   15篇
  1978年   10篇
  1977年   16篇
  1975年   13篇
  1974年   11篇
  1973年   11篇
排序方式: 共有2252条查询结果,搜索用时 93 毫秒
81.
There are various methods to determine the compressive and tensile strength of asphalt concrete under static loading conditions and most studies on asphalt strength and fracture have been conducted under such loading conditions. However, pavement materials also have to withstand a wide variety of loading and temperature conditions which may vary from quasi-static to high-strain rate impact, and pavement breakdown may occur due to fracture and/or fatigue failure. In the present study, a bituminous mix with 30% RAP has been characterized under quasi-static (10?3–10?4 strain/s) and high-strain rate (200–700 strain/s) regimes. The experimental studies have been performed to better understand the compressive, tensile and fracture response of bituminous mixes. Split Hopkinson pressure bar (SHPB) and its modifications were used for high-strain rate characterization of this bituminous mixture. It was observed that the mechanical properties of the hot mix asphalt (HMA) changed significantly under high-strain rate testing. Also, the failure mechanisms observed under the high-strain rate loading were found to be considerably different from those obtained in static testing, where failure of binder was a predominant mechanism. It was observed that high-strain rate loading caused trans-aggregate failures in the specimens; in addition to failure of the binder.  相似文献   
82.
The effect of Gate-Source/Drain underlap (L un) on soft error performance in 30 nm common double gate-FinFET (simultaneously driven gates) and independent double gate-FinFET (independently driven gates) have been examined through extensive mixed mode-device and circuit simulations using Sentaurus TCAD. Four different 6T-SRAM topologies, one simultaneously driven double gate-FinFET and three independently driven double gate-FinFETs-based topologies namely Flex-V TH, Flex-PG, and PG-SN are chosen to study the geometrical parameter L un and also to calculate their soft error performance. When L un increases, current decreases due to increase in parasitic series resistance. The simulation results reveal that L un increase in independently driven double gate-FinFETs in place of access devices in 6T-SRAM does not degrade the soft error performance significantly whereas the L un increase inside the cell, in the inverters, degrade the performance significantly.  相似文献   
83.
84.
Bone transplants are used to treat fractures and increase new tissue development in bone tissue engineering. Grafting of massive implantations showing slow curing rate and results in cell death for poor vascularization. The potentials of biocomposite scaffolds to mimic extracellular matrix (ECM) and including new biomaterials could produce a better substitute for new bone tissue formation. A purpose of this study is to analyze polycaprolactone/silk fibroin/hyaluronic acid/minocycline hydrochloride (PCL/SF/HA/MH) nanoparticles initiate human mesenchymal stem cells (MSCs) proliferation and differentiation into osteogenesis. Electrospraying technique was used to develop PCL, PCL/SF, PCL/SF/HA and PCL/SF/HA/MH hybrid biocomposite nanoparticles and characterization was analyzed by field emission scanning electron microscope (FESEM), contact angle and Fourier transform infrared spectroscopy (FT-IR). The obtained results proved that the particle diameter and water contact angle obtained around 0.54 ± 0.12 to 3.2 ± 0.18 µm and 43.93 ± 10.8° to 133.1 ± 12.4° respectively. The cell proliferation and cell-nanoparticle interactions analyzed using (3-(4,5-dimethyl thiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) MTS assay (Promega, Madison, WI, USA), FESEM for cell morphology and 5-Chloromethylfluorescein diacetate (CMFDA) dye for imaging live cells. Osteogenic differentiation was proved by expression of osteocalcin, alkaline phosphatase activity (ALP) and mineralization was confirmed by using alizarin red (ARS). The quantity of cells was considerably increased in PCL/SF/HA/MH nanoparticles when compare to all other biocomposite nanoparticles and the cell interaction was observed more on PCL/SF/HA/MH nanoparticles. The electrosprayed PCL/SF/HA/MH biocomposite nanoparticle significantly initiated increased cell proliferation, osteogenic differentiation and mineralization, which provide huge potential for bone tissue engineering.  相似文献   
85.
86.
Bulletin of Engineering Geology and the Environment - The numerical methods for slope stability problems always have a serious concern related to their continuum and discontinuum nature. In...  相似文献   
87.
JOM - Prestretch deformation of 6.48% with various initial speeds (1 mm/min, 101 mm/min, and 100 mm/min) was carried out at 723 K to improve the formability of...  相似文献   
88.
Ajith Kumar  K. K.  Srinivasan  A.  Pillai  U. T. S.  Pai  B. C.  Chakraborty  M. 《SILICON》2022,14(15):9499-9515
Silicon - The present work aims at understanding the microstructure and mechanical property correlation of hypo (Mg-0.5, 0.7, 1.15 wt% Si) and hyper (Mg-2, 4, 6, 8 and 10 wt% Si) eutectic binary...  相似文献   
89.
A new one-dimensional Fe(II)molybdophosphate of the formula, [(C10H8N2)H2]2[Fe4(II)Mo12(V)(HPO4)6(PO4)2(H2O)8(OH)6O24]·8H2O, (1), has been synthesized by employing hydrothermal methods and characterized by single crystal X-ray diffraction. The structure consists of a network of MO6 (M = Fe, Mo) octahedra and (H)PO4 tetrahedra linked through their vertices. The connectivity between the polyhedral units gives rise to one-dimensional chains with eight-membered apertures. The hydrogen bonded interactions between the chains form pseudo two-dimensional layers. Extensive hydrogen bonding also exists between the amine molecule, 4,4-bipyridine, water molecule and framework oxygen atoms. Crystal data for 1: monoclinic, space group = P21 (no. 4), a=12.549(3) (Å), b=23.496(5) (Å), c=14.551(3) (Å), β=114.87(3)°, , and Z=2.  相似文献   
90.
The emf of the galvanic cell Pt|UMoO6UMoO5|ZrO2-Y2O3|O2(air, Po2=0.21 atm)|Pt, measured from 776 to 1127 K, was determined to be E = 751.7−0.4909 ±4.3 mV. Using the standard Gibbs energy of formation, fΔG°, for UMoO6 reported in the literature from transpiration studies, the fΔG° for UMoO5 is calculated to be fΔG°〈UMoO5〉=−1816.9+0.3748T±6.0 U-mol−1 The magnitudes of the standard entropies of formation, fΔS°, for UMoO6 and UMoO5 were evaluated from those values reported for the binary oxides which constitute the ternary compounds.  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