全文获取类型
收费全文 | 527418篇 |
免费 | 8287篇 |
国内免费 | 1465篇 |
专业分类
电工技术 | 9609篇 |
综合类 | 529篇 |
化学工业 | 78572篇 |
金属工艺 | 20056篇 |
机械仪表 | 15301篇 |
建筑科学 | 12801篇 |
矿业工程 | 2276篇 |
能源动力 | 14672篇 |
轻工业 | 47138篇 |
水利工程 | 5238篇 |
石油天然气 | 9350篇 |
武器工业 | 37篇 |
无线电 | 60639篇 |
一般工业技术 | 102548篇 |
冶金工业 | 103825篇 |
原子能技术 | 10583篇 |
自动化技术 | 43996篇 |
出版年
2021年 | 5108篇 |
2020年 | 3666篇 |
2019年 | 4723篇 |
2018年 | 8014篇 |
2017年 | 7778篇 |
2016年 | 8180篇 |
2015年 | 5708篇 |
2014年 | 9439篇 |
2013年 | 24385篇 |
2012年 | 14857篇 |
2011年 | 20414篇 |
2010年 | 15994篇 |
2009年 | 17871篇 |
2008年 | 18272篇 |
2007年 | 17929篇 |
2006年 | 15618篇 |
2005年 | 14307篇 |
2004年 | 13671篇 |
2003年 | 13461篇 |
2002年 | 12692篇 |
2001年 | 12890篇 |
2000年 | 11907篇 |
1999年 | 12640篇 |
1998年 | 32962篇 |
1997年 | 22965篇 |
1996年 | 17506篇 |
1995年 | 13091篇 |
1994年 | 11318篇 |
1993年 | 11020篇 |
1992年 | 7939篇 |
1991年 | 7442篇 |
1990年 | 7278篇 |
1989年 | 7037篇 |
1988年 | 6483篇 |
1987年 | 5781篇 |
1986年 | 5675篇 |
1985年 | 6283篇 |
1984年 | 5924篇 |
1983年 | 5184篇 |
1982年 | 4909篇 |
1981年 | 4977篇 |
1980年 | 4714篇 |
1979年 | 4620篇 |
1978年 | 4418篇 |
1977年 | 5292篇 |
1976年 | 6917篇 |
1975年 | 3752篇 |
1974年 | 3506篇 |
1973年 | 3634篇 |
1972年 | 2957篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
Mohamad A.A. Attia Roberto Orrù Francesco Delogu Selena Montinaro Sebastiano Garroni Emad M.M. Ewais Giacomo Cao 《Journal of the American Ceramic Society》2015,98(5):1453-1459
The effects produced by annealing Y2O3 nanopowders on their spark plasma sintering (SPS) behavior are systematically investigated in this work. It is found that the annealed powders display higher sinterability with respect to the as‐received ones. Indeed, the maximum densification level reached from pristine powders is about 97.5%, whereas density decreases when further increasing either the sintering temperature or the dwell time. In contrast, the density of SPS products obtained from pretreated powder monotonically increases with temperature and processing time, thus leading to fully dense materials in 30 min at 1050°C and 60 MPa. Correspondingly, it is found that the annealing treatment markedly inhibits grain coarsening during SPS. Thus, dense translucent samples with grain size below 100 nm can be attained from annealed powders. On the other hand, white‐opaque specimens with significantly coarser microstructures (up to 1‐μm‐sized grains) are obtained when pristine powders are directly processed under the same sintering conditions. Furthermore, it is observed that the annealing treatment of SPS samples in air allows for graphite contamination removal, whereas no improvement in term of light transmittance is produced. 相似文献
135.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
136.
137.
138.
Hoang V. Le Phuong T. Pham Ly T. Le Anh D. Nguyen Ngoc Quang Tran Phong D. Tran 《International Journal of Hydrogen Energy》2021,46(44):22852-22863
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3. 相似文献
139.
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,... 相似文献
140.
Yingcai Bi Menglu Lan Jiaxin Li Shupeng Lai Ben M. Chen 《Asian journal of control》2019,21(4):1732-1744
Micro Aerial Vehicles (MAVs) have great potentials to be applied for indoor search and rescue missions. In this paper, we propose a modular lightweight design of an autonomous MAV with integrated hardware and software. The MAV is equipped with the 2D laser scanner, camera, mission computer and flight controller, running all the computation onboard in real time. The onboard perception system includes a laser‐based SLAM module and a custom‐designed visual detection module. A dual Kalman filter design provides robust state estimation by multiple sensor fusion. Specifically, the fusion module provides robust altitude measurement in the circumstance of surface changing. In addition, indoor‐outdoor transition is explicitly handled by the fusion module. In order to efficiently navigate through obstacles and adapt to multiple tasks, a task tree‐based mission planning method is seamlessly integrated with path planning and control modules. The MAV is capable of searching and rescuing victims from unknown indoor environments effectively. It was validated by our award‐winning performance at the 2017 International Micro Air Vehicle Competition (IMAV 2017), held in Toulouse, France. The performance video is available on https://youtu.be/8H19ppS_VXM . 相似文献