全文获取类型
收费全文 | 187314篇 |
免费 | 10900篇 |
国内免费 | 6110篇 |
专业分类
电工技术 | 7993篇 |
技术理论 | 9篇 |
综合类 | 11555篇 |
化学工业 | 27505篇 |
金属工艺 | 10782篇 |
机械仪表 | 9626篇 |
建筑科学 | 10258篇 |
矿业工程 | 3377篇 |
能源动力 | 3975篇 |
轻工业 | 14266篇 |
水利工程 | 3362篇 |
石油天然气 | 5577篇 |
武器工业 | 1030篇 |
无线电 | 20263篇 |
一般工业技术 | 27036篇 |
冶金工业 | 6517篇 |
原子能技术 | 1383篇 |
自动化技术 | 39810篇 |
出版年
2024年 | 499篇 |
2023年 | 1778篇 |
2022年 | 3523篇 |
2021年 | 4550篇 |
2020年 | 3457篇 |
2019年 | 2712篇 |
2018年 | 17063篇 |
2017年 | 16569篇 |
2016年 | 12780篇 |
2015年 | 5043篇 |
2014年 | 5913篇 |
2013年 | 6711篇 |
2012年 | 10760篇 |
2011年 | 17652篇 |
2010年 | 15664篇 |
2009年 | 12579篇 |
2008年 | 13756篇 |
2007年 | 14296篇 |
2006年 | 6429篇 |
2005年 | 6211篇 |
2004年 | 4678篇 |
2003年 | 4175篇 |
2002年 | 3595篇 |
2001年 | 2672篇 |
2000年 | 2336篇 |
1999年 | 1918篇 |
1998年 | 1395篇 |
1997年 | 1055篇 |
1996年 | 964篇 |
1995年 | 695篇 |
1994年 | 567篇 |
1993年 | 395篇 |
1992年 | 342篇 |
1991年 | 270篇 |
1990年 | 164篇 |
1989年 | 144篇 |
1988年 | 99篇 |
1987年 | 76篇 |
1986年 | 59篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 43篇 |
1965年 | 46篇 |
1960年 | 32篇 |
1959年 | 43篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests. 相似文献
32.
Ye Wan Jun Tan Guangling Song Chuanwei Yan 《Metallurgical and Materials Transactions A》2006,37(7):2313-2316
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that
the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting
finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before. 相似文献
33.
关于我省数字化城市建设的几点思考 总被引:3,自引:0,他引:3
通过对国内外数字化城市建设现状的分析 ,结合我省实际情况 ,提出我省建设数字化城市的对策及建设内容和原则 ,强调政府的组织行为 ,发挥社会各界的积极性 ,充分利用现有资源 ,以建设数字化城市门户网站为先导 ,快速启动全省数字化城市建设。 相似文献
34.
35.
地震属性解释技术的研究及确定性分析 总被引:12,自引:3,他引:9
随着油气勘探开发的不断发展,储层预测、属性分析等技术得到了广泛的应用,在生产中取得了较好的效果。但地震属性的概念,分类方法,地震属性之间、地震属性与储层参数之间的相互关系仍较模糊,各种地震属性解释方法虽然种类繁多,但缺乏系统的研究,这使得地震属性在应用中存在较大的不确定性。文章通过系统研究地震属性的概念、储层地震响应的基本特征,提出了地震响应的核心是反映地震波在介质传播过程中的能量变化,所有能引起地震能量发生变化的介质的不均质性均可导致地震属性的变化,由此提出了一种新的地震属性分类方法,并认为大部分地震属性只是基本属性在不同域中的不同表现形式。在分析现有地震解释技术的基础上,提出了对地震属性解释的新认识,强调了地震属性对地层岩性油气藏勘探的重要性,对属性间的关系及地震属性解释技术的确定性进行了研究,提出了岩性油气藏地震解释的工作流程及对地震资料采集和处理的要求。 相似文献
36.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
37.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
38.
39.
Qin Song Zou Xubiao Zhong Yan Zhang Zhongdong 《中国炼油与石油化工》2006,(1):31-35
1 Introduction Propylene as an important feedstock for organic chemicals is mainly originated from steam cracking and catalytic cracking processes. During the FCC process the propylene content varies with the FCC catalyst and process technology adopted, resulting in significant difference in propylene concentration in the cracked product——LPG. The conventional FCC pro- cess generally gives a propylene yield of around 4%, while the FCC process with maximization of propylene yield can in… 相似文献
40.
大位移井钻柱振动规律研究与应用 总被引:5,自引:0,他引:5
在大位移井钻井工程中钻柱受着各种振动,当各种振动共振时,钻柱承受着非常大的动载,很容易受损,同时,钻柱的振动影响着井壁的稳定,严重威胁着井下的作业安全。以大位移井近井底的钻柱为研究对象,分析了钻柱振动行为所遵循的规律。采用线性分析法,获得了大位移井钻柱横向振动和扭转振动的频谱方程。同时获得了钻柱各种共振频率的分布。经分析表明:大位移井钻柱的横向振动和扭转振动的共振频率与实际钻井转速非常接近,应合理选择转速以减小钻柱共振的发生。文章的分析研究为大位移井钻柱动态行为的研究提供了理论依据。 相似文献