全文获取类型
收费全文 | 114429篇 |
免费 | 11663篇 |
国内免费 | 8099篇 |
专业分类
电工技术 | 9279篇 |
技术理论 | 3篇 |
综合类 | 9874篇 |
化学工业 | 15493篇 |
金属工艺 | 7506篇 |
机械仪表 | 7953篇 |
建筑科学 | 9173篇 |
矿业工程 | 3767篇 |
能源动力 | 3481篇 |
轻工业 | 8634篇 |
水利工程 | 3226篇 |
石油天然气 | 5193篇 |
武器工业 | 1442篇 |
无线电 | 13795篇 |
一般工业技术 | 11671篇 |
冶金工业 | 4441篇 |
原子能技术 | 1741篇 |
自动化技术 | 17519篇 |
出版年
2024年 | 509篇 |
2023年 | 1529篇 |
2022年 | 3248篇 |
2021年 | 4582篇 |
2020年 | 3379篇 |
2019年 | 2778篇 |
2018年 | 2977篇 |
2017年 | 3552篇 |
2016年 | 3284篇 |
2015年 | 4901篇 |
2014年 | 6222篇 |
2013年 | 7237篇 |
2012年 | 8655篇 |
2011年 | 9462篇 |
2010年 | 8901篇 |
2009年 | 8509篇 |
2008年 | 8720篇 |
2007年 | 8402篇 |
2006年 | 7740篇 |
2005年 | 6194篇 |
2004年 | 4653篇 |
2003年 | 3635篇 |
2002年 | 3561篇 |
2001年 | 3007篇 |
2000年 | 2391篇 |
1999年 | 1592篇 |
1998年 | 923篇 |
1997年 | 776篇 |
1996年 | 634篇 |
1995年 | 520篇 |
1994年 | 402篇 |
1993年 | 312篇 |
1992年 | 209篇 |
1991年 | 164篇 |
1990年 | 127篇 |
1989年 | 119篇 |
1988年 | 74篇 |
1987年 | 59篇 |
1986年 | 58篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 26篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1959年 | 23篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Identifying the key factors of the disaster-related information propagation process can provide decision support for disaster management. This study characterizes the effects of content types, location, and social capital of social media users on the virality of disaster-related information. We found through the Weibo dataset of the Yiliang earthquake that the virality of different types of information can vary on the basis of the social capital of users who post the information. This study fills the current research gaps by examining the individual and joint effects of the content and creator characteristics on the virality of disaster-related information. 相似文献
52.
Applied Intelligence - Personnel performance is a key factor to maintain core competitive advantages. Thus, predicting personnel future performance is a significant research domain in human... 相似文献
53.
Morphology and geometry of melted zones, cooling rates, microstructure and microhardness in the laser-glazed Fe-4%C-10%Sn alloy have been investigated. The computer simulation on the basis of the moving gaussian source model was used successfully to predict the maximum width and depth of the melted zone and the cooling rate. The microstructure from the surface to the bottom of the laser-melted zone is a non-crystalline phase, dendritic grains and a microcrystalline zone successively. Values of the averaged-spacing of the non-crystalline phase are 0.2056 and 0.1219nm, respectively; twinned martensites, having an axial ratioc/a of 1.128, existed in dendritic grains, and carbides of Fe3 C at the interdendritic regions; the microcrystalline zone was composed of -Fe and a new bet (a=0.415 nm,c=0.955 nm) phase. The different microstructure in the melted zone can be explained by the results of the heat flow calculation. A fine eutectic structure (-Fe + Fe3C) was observed in heat-affected zones. Microhardness of the eutectic structure can be predicted by the empirical relation of fracture stress to the interlamellar spacing of pearlite. 相似文献
54.
1 INTRODUCTIONTheorthorhombicalloysareofgreattech nolog icalinterestinhightemperatureapplicationssincetheyhaveagoodbalanceamongst 相似文献
55.
Qiu Jun Wang Yueting Wu Peng Jiang Shan Cui Kaibo Chen Guowei Liu Dongliang Cui Guangwen 《Journal of Porous Materials》2021,28(6):1675-1687
Journal of Porous Materials - The dynamics and thermodynamics of adsorption of hexadecyl ammonium with different numbers of carbon chains in montmorillonite (Mt) with different layer charge density... 相似文献
56.
脲醛呋喃树脂中的含氮量,一般采用克氏定氮法,方法繁琐,费时较长,不利于快速分析的要求,本文利用气相色谱法对脲醛呋喃树脂中的氮含量进行分析测定,并建立了测定方法.方法简捷、快速、重现性好,加标回收率在100.8~109.0之间,准确度较高,可很好的满足工业生产中快速分析的要求. 相似文献
57.
Shuya Liang Miaomiao Wang Jun Wang Guanzhi Chen 《Chembiochem : a European journal of chemical biology》2021,22(22):3184-3189
To overcome high toxicity, low bioavailability and poor water solubility of chemotherapeutics, a variety of drug carriers have been designed. However, most carriers are severely limited by low drug loading capacity and adverse side effects. Here, a new type of metal-drug nanoparticles (MDNs) was designed and synthesized. The MDNs self-assembled with Fe(III) ions and drug molecules through coordination, resulting in nanoparticles with high drug loading. To assist systemic delivery and prolong circulation time, the obtained MDNs were camouflaged with red blood cell (RBCs) membranes (RBCs@Fe-DOX MDNs) to improve their stability and dispersity. The RBCs@Fe-DOX MDNs presented pH-responsive release functionalities, resulting in drug release accelerated in acidic tumor microenvironments. The outstanding in vitro and in vivo antitumor therapeutic outcome was realized by RBCs@Fe-DOX MDNs. This study provides an innovative design guideline for chemotherapy and demonstrates the great capacity of nanomaterials in anticancer treatments. 相似文献
58.
59.
60.