全文获取类型
收费全文 | 7210篇 |
免费 | 593篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 57篇 |
综合类 | 5篇 |
化学工业 | 1701篇 |
金属工艺 | 123篇 |
机械仪表 | 172篇 |
建筑科学 | 202篇 |
矿业工程 | 12篇 |
能源动力 | 255篇 |
轻工业 | 1231篇 |
水利工程 | 73篇 |
石油天然气 | 32篇 |
无线电 | 361篇 |
一般工业技术 | 1254篇 |
冶金工业 | 1020篇 |
原子能技术 | 40篇 |
自动化技术 | 1277篇 |
出版年
2024年 | 11篇 |
2023年 | 74篇 |
2022年 | 155篇 |
2021年 | 283篇 |
2020年 | 199篇 |
2019年 | 209篇 |
2018年 | 293篇 |
2017年 | 289篇 |
2016年 | 331篇 |
2015年 | 261篇 |
2014年 | 327篇 |
2013年 | 558篇 |
2012年 | 423篇 |
2011年 | 563篇 |
2010年 | 379篇 |
2009年 | 369篇 |
2008年 | 338篇 |
2007年 | 326篇 |
2006年 | 206篇 |
2005年 | 195篇 |
2004年 | 152篇 |
2003年 | 117篇 |
2002年 | 142篇 |
2001年 | 102篇 |
2000年 | 86篇 |
1999年 | 85篇 |
1998年 | 339篇 |
1997年 | 236篇 |
1996年 | 163篇 |
1995年 | 101篇 |
1994年 | 63篇 |
1993年 | 68篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 18篇 |
1989年 | 27篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1977年 | 16篇 |
1976年 | 27篇 |
1975年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有7815条查询结果,搜索用时 187 毫秒
1.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
2.
Esperanza González-Redondo 《建筑学研究前沿(英文版)》2022,11(2):255-277
The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector. 相似文献
3.
4.
5.
Alberto Ballesteros Ester Laguna-Gutierrez Paula Cimavilla-Roman Maria Luisa Puertas Antonio Esteban-Cubillo Julio Santaren Miguel Angel Rodriguez-Perez 《应用聚合物科学杂志》2021,138(46):51373
In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear rheology and X-ray micro-computed tomography. Sepiolites treated with quaternary ammonium salts (O-QASEP) are better dispersed in the PS matrix than natural sepiolites (N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A percolated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEP and 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O-QASEP present the lowest cell size and the most homogeneous cellular structures. 相似文献
6.
Dr. Alejandra A. Carriles Alberto Mills Dr. María-José Muñoz-Alonso Dr. Dolores Gutiérrez Dr. Juan M. Domínguez Prof. Dr. Juan A. Hermoso Prof. Dr. Federico Gago 《Chembiochem : a European journal of chemical biology》2021,22(2):374-391
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades. 相似文献
7.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
8.
9.
Luca Cornolti Simone Martinelli Giovanni Bianchi Alberto Ortona 《Journal of the American Ceramic Society》2019,102(5):2304-2315
In this work, we investigated a procedure which exploits microwave ovens to produce SiC- based components by reactive melt infiltration of silicon into graphite preforms. The employed oven is designed to grant optical access to the sample surface, which allows to measure its temperature evolution though a noncontact pyrometer. This signal was used as a feedback to control the power provided to the preform and as an experimental output whose analysis provides insight into the reaction mechanism. Specifically, it is found that complete infiltration is achieved much before the end of the reaction. The latter is not fully self-sustained as the global reaction rate continuously decreases with time until it is no more able to keep the temperature above the silicon solidification value. At that point, the reaction stops. The analysis of the processed samples proved that this procedure allows producing fully infiltrated samples without material failure by adjusting the heat provided during the infiltration stage rather than by tuning the preform structure and composition, which is the usual approach. The proposed method is less time and energy consuming than the standard one. 相似文献