全文获取类型
收费全文 | 12802篇 |
免费 | 1752篇 |
国内免费 | 992篇 |
专业分类
电工技术 | 1224篇 |
综合类 | 1458篇 |
化学工业 | 1533篇 |
金属工艺 | 769篇 |
机械仪表 | 918篇 |
建筑科学 | 1065篇 |
矿业工程 | 418篇 |
能源动力 | 330篇 |
轻工业 | 1511篇 |
水利工程 | 517篇 |
石油天然气 | 378篇 |
武器工业 | 119篇 |
无线电 | 1356篇 |
一般工业技术 | 983篇 |
冶金工业 | 706篇 |
原子能技术 | 313篇 |
自动化技术 | 1948篇 |
出版年
2024年 | 89篇 |
2023年 | 220篇 |
2022年 | 546篇 |
2021年 | 729篇 |
2020年 | 496篇 |
2019年 | 328篇 |
2018年 | 397篇 |
2017年 | 382篇 |
2016年 | 388篇 |
2015年 | 592篇 |
2014年 | 692篇 |
2013年 | 836篇 |
2012年 | 1025篇 |
2011年 | 1043篇 |
2010年 | 1015篇 |
2009年 | 982篇 |
2008年 | 1045篇 |
2007年 | 982篇 |
2006年 | 865篇 |
2005年 | 712篇 |
2004年 | 480篇 |
2003年 | 379篇 |
2002年 | 335篇 |
2001年 | 297篇 |
2000年 | 249篇 |
1999年 | 136篇 |
1998年 | 47篇 |
1997年 | 36篇 |
1996年 | 42篇 |
1995年 | 30篇 |
1994年 | 24篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1964年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Poly(L ‐lactic acid) (PLLA) scaffolds with pore diameters from several micrometers to ~300 μm were fabricated by a specially elaborated thermally induced phase separation technique. Two different coarsening protocols, i.e., normal coarsening and multi‐step coarsening were compared in consideration of phase separation and domain growth. A normal coarsening route produced scaffolds with pore size from several micrometers to 150 μm depending on the coarsening time after phase separation, accompanying with the emergence of isolated pores at long time coarsening. Scaffolds with large pores with size up to ~300 μm were fabricated by the two‐step coarsening technique, e.g., the PLLA‐solvent (dioxane/water) system was coarsened at a temperature after phase separation for a period, followed by coarsening at a lower temperature for another period. In parallel with formation of the large pores, the interconnectivity between pores was also improved, which was evidenced by scanning electron microscopy, gelatin solution pervasion, and collagen entrapment. The present technique provides the ability to produce scaffolds with high purity, controllable microstructures, and ease of modification, and hence can be widely used in tissue engineering field. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3336–3342, 2006 相似文献
72.
73.
74.
75.
76.
海上漏油的频繁发生以及采油废水、工业含油污水的大量排放造成水资源大片污染和生态系统平衡的严重破坏。目前,从水体中分离油品和有机污染物已受到越来越多的商业和学术的关注。石墨烯基气凝胶是由二维石墨烯片层组装成的三维宏观材料,因其孔隙率高、比表面积大、密度低、机械性能强等特点在油水分离领域具有广阔的应用前景,已成为当今的研究热点之一。本文结合最新研究进展系统地总结了石墨烯基气凝胶的结构设计、组装及干燥方法,归纳了近年来其在油水分离中的应用进展,并对石墨烯基气凝胶在油水分离领域的研究现状和未来研究方向做了简要评述,以期为该领域的深入探索提供新的视角。 相似文献
77.
Claudia Szabo Quan Z. Sheng Trent Kroeger Yihong Zhang Jian Yu 《Journal of Grid Computing》2014,12(2):245-264
An important challenge for the adoption of cloud computing in the scientific community remains the efficient allocation and execution of data-intensive scientific workflows to reduce execution time and the size of transferred data. The transferred data overhead is becoming significant with emerging scientific workflows that have input/output files and intermediate data products ranging in the hundreds of gigabytes. The allocation of scientific workflows on public clouds can be described through a variety of perspectives and parameters, and has been proved to be NP-complete. This paper proposes an evolutionary approach for task allocation on public clouds considering data transfer and execution time. In our framework, a solution is represented using an allocation chromosome that encodes the allocation of tasks to nodes, and an ordering chromosome that defines the execution order according to the scientific workflow representation. We propose a multi-objective optimization that relies on a cloud cost model and employs tailored evolution operators. Starting from a population of possible solutions, we employ crossover and mutation operators on both chromosomes aiming at optimizing the data transferred between nodes as well as the total workflow runtime. The crossover operators combine parts of solutions to reduce data overhead, whereas the mutation operators swamp between parts of the same chromosome according to pre-defined rules. Our experimental study compares between the proposed approach and current state-of-the art approaches using synthetic and real-life workflows. Our algorithm performs similarly to existing heuristics for small workflows and shows up to 80 % improvements for larger synthetic workflows. To further validate our approach we compare between the allocation and scheduling obtained by our approach with that obtained by popular scientific workflow managers, when real workflows with hundreds of tasks are executed on a public cloud. The results show a 10 % improvement in runtime over existing schedulers, caused by a 80 % reduction in transferred data and optimized allocation and ordering of tasks. This improved data locality has greater impact as it can be employed to improve and study data provenance and facilitate data persistence for scientific workflows. 相似文献
78.
低温甲醇洗技术在20万 t/a 甲醇装置中的应用 总被引:3,自引:0,他引:3
简单介绍了上海焦化总厂20万t/a甲醇装置中低温甲醇洗脱硫脱碳技术的应用情况。经过一年多的稳定运行,证明该技术工艺先进成熟,净化气质量稳定,满足生产需要,在以煤为原料的煤气脱硫脱碳中的应用是成功的。 相似文献
79.
80.