全文获取类型
收费全文 | 49428篇 |
免费 | 4689篇 |
国内免费 | 2546篇 |
学科分类
工业技术 | 56663篇 |
出版年
2024年 | 87篇 |
2023年 | 716篇 |
2022年 | 1181篇 |
2021年 | 1879篇 |
2020年 | 1451篇 |
2019年 | 1292篇 |
2018年 | 1455篇 |
2017年 | 1625篇 |
2016年 | 1478篇 |
2015年 | 1874篇 |
2014年 | 2448篇 |
2013年 | 2887篇 |
2012年 | 2966篇 |
2011年 | 3288篇 |
2010年 | 2838篇 |
2009年 | 2693篇 |
2008年 | 2700篇 |
2007年 | 2565篇 |
2006年 | 2658篇 |
2005年 | 2229篇 |
2004年 | 1647篇 |
2003年 | 1904篇 |
2002年 | 2186篇 |
2001年 | 1924篇 |
2000年 | 1427篇 |
1999年 | 1454篇 |
1998年 | 1028篇 |
1997年 | 869篇 |
1996年 | 869篇 |
1995年 | 686篇 |
1994年 | 585篇 |
1993年 | 459篇 |
1992年 | 308篇 |
1991年 | 227篇 |
1990年 | 177篇 |
1989年 | 157篇 |
1988年 | 155篇 |
1987年 | 93篇 |
1986年 | 55篇 |
1985年 | 35篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1976年 | 3篇 |
1971年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Long Jian Jiangping Hu Jun Wang Kaibo Shi Zhinan Peng Yaoru Yang Jiuke Huang 《International Journal of Control, Automation and Systems》2020,18(5):1094-1102
This paper studies the containment control problem of linear multi-agent systems (MASs) with a directed graph, where the states of the followers will asymp 相似文献
92.
Zhou Xiangyang Shi Yanjun Li Lingling Yu Ruifang Zhao Libo 《International Journal of Control, Automation and Systems》2020,18(6):1498-1509
International Journal of Control, Automation and Systems - This paper presents a high precision compound control scheme based on non-singular terminal sliding mode and extended state observer (ESO)... 相似文献
93.
歧口凹陷歧北次凹沙河街组三段页岩油地质特征与勘探突破 总被引:1,自引:0,他引:1
歧口凹陷歧北次凹沙河街组三段(沙三段)湖泛期细粒沉积发育、烃源岩品质好、页岩油资源丰富,但其研究尚处于起步阶段,在沧东凹陷孔店组二段湖相页岩油工业化开发的带动下,落实其勘探前景势成必然。为探究歧北次凹沙三段页岩油的地质特征及勘探潜力,依据F39X1井、QY10-1-1井等多口井的岩心、分析化验、测井资料和录井资料,对沙三段页岩层系的地质特征、页岩油类型与富集模式、甜点的空间分布规律等开展了综合研究。歧北次凹沙三段的矿物组成和岩石类型多样,主要包括灰质白云质页岩、长英质页岩、混合质页岩及微晶白云岩、亮晶生屑白云岩、粉砂岩等;烃源岩的总有机碳(TOC)含量主要分布在1%~3%,以Ⅱ型干酪根为主且指示热演化成熟度的镜质体反射率(Ro)普遍高于0.7%;储集空间主要包括粒间孔、晶间孔、生物体腔孔、有机孔及层理缝、构造(微)缝等;页岩油的超越效应明显(油饱和度指数平均为116.3 mg/g)、荧光显示良好。在歧北次凹沙三段中识别出单一型和夹层型2类页岩油,构建了高TOC滞留型页岩油和低TOC运移型页岩油2种富集模式,并建立了基于油饱和度指数、TOC和脆性指数等多参数的甜点定量评价方法及标准。针对甜点区部署了QY10-1-1水平井,其初期的折算产油量达103.5 t/d,预计可形成亿吨级增储新领域。勘探发现证实歧口凹陷的沙三段细粒岩段具备良好的页岩油勘探潜力。 相似文献
94.
95.
96.
Water-lubricated polymer is attracting more and more interest from the industry. Adding nanoparticles is considered to be an effective way to improve the tribological performance. In this work, water-lubricated Polyetheretherketone (PEEK)-steel contacts were employed as the objects of study. A careful comparative study was made by investigating the effect of adding graphene oxide (GO) into water or into PEEK. Results show that adding GO into water can significantly reduce the wear and friction coefficient of pure PEEK, which is much more effective than adding GO into PEEK. Under the lubrication of GO aqueous dispersion, the wear of PEEK remains very low even under a harsh condition where the pressure reaches 50 MPa and the linear sliding speed is 0.7 m/s. Neat PEEK and GO/PEEK composites in pure water exhibit serious wear under this harsh condition. The excellent lubricating properties of GO aqueous dispersion are attributed to GO nanosheets entering into solid contacts, which can not only form a protective layer on steel counterpart repairing the worn surface, but also strongly adhere to the PEEK matrix resulting in an in situ-formed GO coating and prevent the scratch by steel counterpart. 相似文献
97.
98.
Fan Zhang Chuan Zhang Duchao Lv Jun Zhu Weisheng Cao Shuanglin Chen Rainer Schmid-Fetzer 《Journal of Phase Equilibria and Diffusion》2018,39(5):562-570
In this work, high throughput calculation (HTC) is used to identify composition regions with good glass forming ability (GFA) in the Al-Cu-Zr, Cu-Ni-Zr, Cu-Ti-Zr, Cu-Ni-Ti-Zr, Al-Cu-Ni-Ti-Zr, Mg-Ca-Cu, and Mg-Ca-Ni systems. The predicted composition regions agree well with those observed by experiments in the ternary systems, while less satisfactory agreement is found in the Cu-Ni-Ti-Zr quaternary and the Al-Cu-Ni-Ti-Zr quinary systems. The possible causes that lead to the deviation in the higher order systems are discussed. The major advantage of the HTC method used in this study is that it is simple and can be easily applied to multicomponent systems. The color maps of liquidus temperature and solidification range obtained by HTC provide a valuable guidance to the experimentalists, thus they can focus on the composition regions with high potential of forming bulk metallic glasses, avoid unnecessary trial-and-error test and save time and cost. This approach can also be combined with other criteria to filter compositions with better GFA. 相似文献
99.
Veronika Stahl Yuan Shi Werner Kraft Tim Lanz Peter Vetter Raouf Jemmali Fiona Kessel Dietmar Koch 《International Journal of Applied Ceramic Technology》2020,17(5):2040-2050
Thanks to their high energy density and thermal conductivity, metallic Phase Change Materials (mPCM) have shown great potential to improve the performance of thermal energy storage systems. However, the commercial application of mPCM is still limited due to their corrosion behavior with conventional container materials. This work first addresses on a fundamental level, whether carbon-based composite-ceramics are suitable for corrosion critical components in a thermal storage system. The compatibility between the mPCM AlSi12 and the Liquid Silicon Infiltration (LSI)-based carbon fiber reinforced silicon carbide (C/C-SiC) composite is then investigated via contact angle measurements, microstructure analysis, and mechanical testing after exposure. The results reveal that the C/C-SiC composite maintains its mechanical properties and microstructure after exposure in the strongly corrosive mPCM. Based on these results, efforts were made to design and manufacture a container out of C/C-SiC for the housing of mPCM in vehicle application. The stability of the component filled with mPCM was proven nondestructively via computer tomography (CT). Successful thermal input- and output as well as thermal storage ability were demonstrated using a system calorimeter under conditions similar to the application. The investigated C/C-SiC composite has significant application potential as a structural material for thermal energy storage systems with mPCM. 相似文献
100.
Ruilian Zhang Guoqing Shi Yuanni Wang Si Zhao Shafiq Ahmad Xiaochen Zhang 《影响评估与项目评价》2018,36(4):331-347
In order to analyze potential social risks, and achieve smooth implementation of investment activities in the China–Pakistan economic corridor (CPEC), we attempt to establish social impact and risk indicators. Both the impacts on the projects and the impacts of the projects are used to develop risk indicators in accordance with the literature review, reality and international standard principles. Using an analytic hierarchy process (AHP) and average value to analyze questionnaires of both Chinese and Pakistani respondents, we identify the importance of various risk indicators. The primary social risks of the western high mountain region include tribal obstacles and religious extremism. The social risks to the southeast coastal plains include preserving the historical and cultural heritage of the area and international protection of national parks. The social risks in north Kashmir include disputes, extremist threats, religious and cultural differences, and the protection of natural reserves. The social risks of the Xinjiang region primarily involve social issues faced by ethnic minorities and environmental pressures. 相似文献