全文获取类型
收费全文 | 563640篇 |
免费 | 7837篇 |
国内免费 | 1847篇 |
专业分类
电工技术 | 10692篇 |
综合类 | 454篇 |
化学工业 | 82487篇 |
金属工艺 | 20053篇 |
机械仪表 | 15840篇 |
建筑科学 | 14674篇 |
矿业工程 | 1560篇 |
能源动力 | 14555篇 |
轻工业 | 53222篇 |
水利工程 | 4557篇 |
石油天然气 | 4537篇 |
武器工业 | 20篇 |
无线电 | 74964篇 |
一般工业技术 | 104277篇 |
冶金工业 | 113080篇 |
原子能技术 | 8279篇 |
自动化技术 | 50073篇 |
出版年
2021年 | 3610篇 |
2019年 | 3459篇 |
2018年 | 5490篇 |
2017年 | 5572篇 |
2016年 | 5859篇 |
2015年 | 4582篇 |
2014年 | 7612篇 |
2013年 | 25303篇 |
2012年 | 13392篇 |
2011年 | 19046篇 |
2010年 | 14885篇 |
2009年 | 17201篇 |
2008年 | 18259篇 |
2007年 | 18724篇 |
2006年 | 16874篇 |
2005年 | 15743篇 |
2004年 | 15349篇 |
2003年 | 14913篇 |
2002年 | 14455篇 |
2001年 | 14855篇 |
2000年 | 13855篇 |
1999年 | 14824篇 |
1998年 | 36640篇 |
1997年 | 25840篇 |
1996年 | 20155篇 |
1995年 | 15384篇 |
1994年 | 13669篇 |
1993年 | 13357篇 |
1992年 | 9604篇 |
1991年 | 9243篇 |
1990年 | 8831篇 |
1989年 | 8464篇 |
1988年 | 8024篇 |
1987年 | 6692篇 |
1986年 | 6681篇 |
1985年 | 8036篇 |
1984年 | 7392篇 |
1983年 | 6462篇 |
1982年 | 6003篇 |
1981年 | 6128篇 |
1980年 | 5618篇 |
1979年 | 5399篇 |
1978年 | 5131篇 |
1977年 | 6246篇 |
1976年 | 8431篇 |
1975年 | 4294篇 |
1974年 | 4122篇 |
1973年 | 3960篇 |
1972年 | 3250篇 |
1971年 | 2797篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. 相似文献
74.
The patent literature concerning thermal spraying for biomedical applications is reviewed in this contribution. The patents were compiled from multiple databases search spanning the 2005-2018 period. For clarity and ease of reading, the results have been grouped into sections according to four individual material groups (apatites, titanium, oxide ceramics, other), with the secondary sorting criterion being related to the specific bioapplication areas (maxillofacial, orthopedic, methods). Lastly, the patents are grouped according to the selected thermal spray method within the individual subsections. In the paper, recent R&D trends in this field are further identified and briefly commented. 相似文献
75.
76.
77.
78.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献
79.
80.
Joshua C. Price Simon J. Levett Valentin Radu David A. Simpson Aina Mogas Barcons Christopher F. Adams Melissa L. Mather 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits. 相似文献