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   77779篇
  免费   7435篇
  国内免费   3556篇
电工技术   4882篇
技术理论   8篇
综合类   5254篇
化学工业   12435篇
金属工艺   4282篇
机械仪表   4720篇
建筑科学   6020篇
矿业工程   2083篇
能源动力   2270篇
轻工业   6375篇
水利工程   1542篇
石油天然气   3966篇
武器工业   689篇
无线电   9681篇
一般工业技术   9483篇
冶金工业   3495篇
原子能技术   976篇
自动化技术   10609篇
  2025年   28篇
  2024年   1499篇
  2023年   1597篇
  2022年   2590篇
  2021年   3507篇
  2020年   2906篇
  2019年   2293篇
  2018年   2320篇
  2017年   2456篇
  2016年   2430篇
  2015年   3166篇
  2014年   3887篇
  2013年   4459篇
  2012年   5073篇
  2011年   5419篇
  2010年   4645篇
  2009年   4414篇
  2008年   4352篇
  2007年   4156篇
  2006年   3838篇
  2005年   3264篇
  2004年   2410篇
  2003年   2062篇
  2002年   1878篇
  2001年   1650篇
  2000年   1787篇
  1999年   1927篇
  1998年   1555篇
  1997年   1287篇
  1996年   1252篇
  1995年   1022篇
  1994年   873篇
  1993年   612篇
  1992年   479篇
  1991年   333篇
  1990年   305篇
  1989年   269篇
  1988年   177篇
  1987年   131篇
  1986年   108篇
  1985年   68篇
  1984年   58篇
  1983年   34篇
  1982年   46篇
  1981年   32篇
  1980年   27篇
  1979年   13篇
  1976年   10篇
  1973年   8篇
  1959年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Journal of Applied Electrochemistry - There has been a growing interest in the performance of supercapacitors (SCs) based on Transition Metal Oxides (TMOs). It has recently been included in...  相似文献   
53.
Jia  Ning  Peng  ZhiLong  Wang  Shuai  Li  JianJun  Yao  Yin  Chen  ShaoHua 《中国科学:技术科学(英文版)》2020,63(11):2413-2422
Science China Technological Sciences - Nanostructured electrodes with surface effect show a distinct advantage in prolonging the lifetime of lithium-ion (Li-ion) battery. In order to characterize...  相似文献   
54.
In this article, poly (dimethyl siloxane) (PDMS) porous beads were prepared by suspension polymerization method using n‐octane and carbon tetrachloride (CCl4) as diluents and pore formation agents. The apparent density, porosity and other characteristics were characterized. The absorption experiments showed that the porous PDMS beads exhibited more absorption capacity and faster absorption rate toward oils than the nonporous or oligoporous PDMS beads did, moreover they are of remarkable stability and recyclability, which could provide a path to absorb the oils floating on water. POLYM. ENG. SCI., 54:2965–2969, 2014. © 2014 Society of Plastics Engineers  相似文献   
55.
Inspired by pressure resistance welding of metallic materials, herein we describe how two MAX phases—Ti3SiC2 and Ti3AlC2—were successfully joined by a rapid electric current heating method in a pulsed electric current sintering furnace. No welding agent was employed and the total processing time was less than 6 min. When the bulk temperature of the joint couple exceeded 1070°C, good joints, with shear strength above 50 MPa, were achieved in both homo‐ and heterojunction joints.  相似文献   
56.
For the purpose of obtaining fully dense B4C with micro hole array of high quality and precision, synthesis of B4C powders were carried out by micro powder injection molding. Five kinds of additive systems were used and their influences on mechanical properties were investigated. The relative density, Vickers hardness, bending strength, and fracture toughness of the B4C ceramics with BS10AY additive sintered at 2000 °C for 2 h could reach 97.56%, 3580.4 HV, 355.3 MPa and 5.87 MPa m1/2, respectively. The temperature was generally 100–200 °C lower than reported temperatures which was attributed to the additives. The improvement in mechanical properties was attributed to grain refinement. A mixture of intragranular and transgranular fractures occurred due to the fine microstructures and the additive systems in the B4C ceramics after sintering. Micro-hole array with the diameter of 450 μm and the length-diameter ratio of more than 8 were obtained. The inhomogeneous filling of feedstock from the substrate to the thin wall between two adjacent micro holes caused the inhomogeneous shrinkage of the substrate and micro holes.  相似文献   
57.
在惰性气氛保护下,对炭黑样品进行不同温度下的热处理,得到具有不同石墨化度的炭黑样品。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、热重分析仪(TG)、以及拉曼分析仪(Raman)等对其进行了结构表征,结果表明随着碳化温度的升高,炭黑样品的石墨化程度显著增大,尤其在经过2 800℃高温热处理的炭黑样品中出现了中空的石墨化结构,有望成为具有较大吸附性能的橡塑弹性体材料的较好补强剂。  相似文献   
58.
丁凝  刘建明 《广东化工》2014,(7):167-168
文章介绍了目前工业磷化废水处理过程中常用的化学沉淀除磷法,研究了pH、PAM投加量的变化对除磷效率的影响。确定了除磷的最佳工艺条件为:pH为7.5~9之间,PAM投加量为300 mg/L。  相似文献   
59.
60.
1,1?-Diamino-4,4?,5,5?-tetranitro-2,2?-biimidazole (DATNBI) was synthesized, by employing one-pot facile method, from 4,4?,5,5?-tetranitro-2,2?-biimidazole. The crystal structure was determined by X-ray diffraction for the first time. DATNBI crystallized in monoclinic system P21/c, with a crystal density of 1.934 g cm?3 at 293(2) K and 2.019 g cm?3 at 130(2) K, respectively. Its crystal parameters at 293 K are = 4.8833(15) Å, = 6.960(2) Å, = 6.928(4) Å, α γ = 90°, β = 93.418(6)°, = 591.1(3) ?3, = 2, μ = 0.178 mm?1, and F(000) = 348. The thermal stability and non-isothermal kinetics of DATNBI were studied by differential scanning calorimeter (DSC) with heating rates of 5, 10, 15, and 20 K min?1. The apparent activation energy (Ea) at the first decomposition peak calculated by Kissinger, Ozawa, and Starink equations were 85.50, 89.67, and 86.10 kJ mol?1, respectively. For the second peak, these were 116.49, 119.82, and 117.45 kJ mol?1, respectively, with individual pre-exponential factors ln= 18.40 s?1 and ln= 25.11 s?1. The thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) analysis of thermal decomposition products reveals that the main decomposition gas products are H2O, N2O, CO2, and NO2. Based on the new crystalline densities, the detonation velocity and pressure predicted by EXPLO5 are 9062 m s?1 and 36.4 GPa, respectively.  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