全文获取类型
收费全文 | 42720篇 |
免费 | 3639篇 |
国内免费 | 1560篇 |
专业分类
电工技术 | 4190篇 |
技术理论 | 1篇 |
综合类 | 3111篇 |
化学工业 | 6861篇 |
金属工艺 | 3617篇 |
机械仪表 | 2795篇 |
建筑科学 | 3448篇 |
矿业工程 | 2264篇 |
能源动力 | 1592篇 |
轻工业 | 4193篇 |
水利工程 | 1007篇 |
石油天然气 | 2044篇 |
武器工业 | 424篇 |
无线电 | 1533篇 |
一般工业技术 | 4062篇 |
冶金工业 | 4276篇 |
原子能技术 | 581篇 |
自动化技术 | 1920篇 |
出版年
2024年 | 185篇 |
2023年 | 554篇 |
2022年 | 1140篇 |
2021年 | 1284篇 |
2020年 | 1301篇 |
2019年 | 1000篇 |
2018年 | 1028篇 |
2017年 | 1288篇 |
2016年 | 1323篇 |
2015年 | 1390篇 |
2014年 | 2433篇 |
2013年 | 2457篇 |
2012年 | 2864篇 |
2011年 | 2945篇 |
2010年 | 2216篇 |
2009年 | 2191篇 |
2008年 | 1901篇 |
2007年 | 2668篇 |
2006年 | 2649篇 |
2005年 | 2275篇 |
2004年 | 2042篇 |
2003年 | 1795篇 |
2002年 | 1631篇 |
2001年 | 1426篇 |
2000年 | 1156篇 |
1999年 | 977篇 |
1998年 | 770篇 |
1997年 | 629篇 |
1996年 | 537篇 |
1995年 | 448篇 |
1994年 | 408篇 |
1993年 | 270篇 |
1992年 | 204篇 |
1991年 | 145篇 |
1990年 | 99篇 |
1989年 | 100篇 |
1988年 | 52篇 |
1987年 | 37篇 |
1986年 | 17篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1959年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
介绍了通过初级颜料的润湿、研磨与分散、稳定处理技术,使助剂和树脂均匀地包裹在颜料表面,并通过特殊工艺制得水性和油性色浆粉,并赋予了很好的速溶性和分散性。 相似文献
12.
在内径120 mm的半圆柱形内循环流化床中,以平均粒径387 nm的Ti O2为原料,考察了单独通入流化气、射流气和同时通入流化气和射流气三种流化方式下超细粉的流化特性以及射流气速对超细粉聚团尺寸的影响。结果表明:同时通入流化气和射流气时,流化气能促进粉体循环,消除环隙死区;高速射流能有效破碎聚团,显著减小聚团尺寸,从而使超细粉在环隙区与导流管之间形成稳定循环,小聚团在环隙区实现平稳流态化。随着射流气速的增大,聚团尺寸减小,粒度分布变窄,在射流气速分别为60,90,120,150 m/s的条件下,聚团平均直径分别为194,158,147,135μm。 相似文献
13.
14.
Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent
下载免费PDF全文
![点击此处可从《火与材料》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The relationship between the particle size distribution and the extinguishing effectiveness of the new K‐powder fire extinguishing agent has been studied experimentally, to explore the reason of the great extinguishing efficiency exhibited by the new K‐powder fire extinguishing agent on Class B fire (liquid fuel fire). The results of the experiment showed that the extinguishing effectiveness increased along with the decrease of the particle size distribution. In addition, a sharp discontinuity appeared around the limiting size, about 40 μm. The powder with the particle size below 40 μm exhibited highly effective extinguishing with the minimum effective extinguishing concentration Cxr = 23 g·m?3, while the powder with the particle size above 40 μm exhibited little fire extinguishing efficiency. Compared with other fire extinguishing agents produced by different substances, the new K‐powder fire extinguishing has the bigger limiting size. That means, in the same particle size distribution, the new K‐powder fire extinguishing agent contains more highly effective powder than others contain, and is more effective. 相似文献
15.
16.
Seyedeh Nooshin Banitaba Dariush Semnani Elahe Heydari‐Soureshjani Behzad Rezaei Ali A Ensafi Ahmadreza Taghipour‐Jahromi 《Polymer International》2020,69(8):675-687
In this study, solvent‐free nanofibrous electrolytes were fabricated through an electrospinning method. Polyethylene oxide (PEO), lithium perchlorate and ethylene carbonate were used as polymer matrix, salt and plasticizer respectively in the electrolyte structures. Keggin‐type hetero polyoxometalate (Cu‐POM@Ru‐rGO, Ni‐POM@Ru‐rGO and Co‐POM@Ru‐rGO (POM, polyoxometalate; rGO, reduced graphene oxide)) nanoparticles were synthesized and inserted into the PEO‐based nanofibrous electrolytes. TEM and SEM analyses were carried out for further evaluation of the synthesized filler structures and the electrospun nanofibre morphologies. The fractions of free ions and crystalline phases of the as‐spun electrolytes were estimated by obtaining Fourier transform infrared and XRD spectra, respectively. The results showed a significant improvement in the ionic conductivity of the nanofibrous electrolytes by increasing filler concentrations. The highest ionic conductivity of 0.28 mS cm?1 was obtained by the introduction of 0.49 wt% Co‐POM@Ru‐rGO into the electrospun electrolyte at ambient temperature. Compared with solution‐cast polymeric electrolytes, the electrospun electrolytes present superior ionic conductivity. Moreover, the cycle stability of the as‐spun electrolytes was clearly improved by the addition of fillers. Furthermore, the mechanical strength was enhanced with the insertion of 0.07 wt% fillers to the electrospun electrolytes. The results implied that the prepared nanofibres are good candidates as solvent‐free electrolytes for lithium ion batteries. © 2020 Society of Chemical Industry 相似文献
17.
This paper deals with the investigation of the effect of hygrothermal conditions on the bending of nanoplates using Levy type solution model employing the state-space concept. The nanoplates are assumed to be subjected to a hygrothermal environment. The two-unknown function plate theory is used to derive the governing differential equations on the basis of Eringen's nonlocal elasticity theory. The governing equations contain the small scale effect as well as hygrothermal and mechanical effects. These equations are converted into a set of first-order linear ordinary differential equations with constant coefficients. Analytical solution of bending response for nanoplates under combinations of simply supported, clamped and free boundary conditions is obtained. Comparison of the results with those being in the open literature is made. The influences played by small scale parameter, temperature rise, the degree of moisture concentration, boundary conditions, plate aspect ratio and side-to-thickness ratio are studied. 相似文献
18.
通过对接轨站设置位置和布置图型主要影响因素的分析。按照能够充分反映接轨站作业特点的交接方式。对接轨站所采用的布置图型进行了归纳和分类。 相似文献
19.
汽油烃类族组成测试方法对比 总被引:1,自引:0,他引:1
介绍了使用荧光指示剂吸附色谱法、多维气相色谱法的测定影响因素和近红外光谱快速法的分析特点以及三种方法在汽油族组成测定中的应用,并就三种方法对同一试样的测定结果进行了对比,找出各种测定方法容易产生误差的原因及分析对策。 相似文献
20.
国际石油合同中的风险与对策 总被引:3,自引:0,他引:3
王灵碧 《油气地质与采收率》2006,13(5):98-102
石油公司从事跨国石油勘探开发活动,必然受到国际石油合同的影响和制约。国际石油合同包括租让制合同、产品分成合同、风险服务合同、回购合同、联合经营和国家石油公司私有化6类。石油合同风险分为地质风险、技术风险、财务风险、商业风险和政治风险5种类型。通过全面分析国际石油合同及其风险的类型和特点,认为在油气勘探开发项目的不同阶段风险管理的重点不同,石油公司必须建立科学的投资决策程序,采取定量与定性相结合的风险分析和投资决策方法,合理利用资源国财税制度等措施规避和降低风险,对中国的石油公司从事跨国石油勘探开发具有重要意义。 相似文献