全文获取类型
收费全文 | 252837篇 |
免费 | 2794篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 4808篇 |
综合类 | 193篇 |
化学工业 | 36118篇 |
金属工艺 | 9507篇 |
机械仪表 | 7544篇 |
建筑科学 | 6072篇 |
矿业工程 | 880篇 |
能源动力 | 7225篇 |
轻工业 | 21098篇 |
水利工程 | 2202篇 |
石油天然气 | 3230篇 |
武器工业 | 15篇 |
无线电 | 34277篇 |
一般工业技术 | 49970篇 |
冶金工业 | 48534篇 |
原子能技术 | 5075篇 |
自动化技术 | 19753篇 |
出版年
2021年 | 2173篇 |
2020年 | 1560篇 |
2019年 | 1918篇 |
2018年 | 3273篇 |
2017年 | 3311篇 |
2016年 | 3398篇 |
2015年 | 2219篇 |
2014年 | 3955篇 |
2013年 | 11473篇 |
2012年 | 6233篇 |
2011年 | 8573篇 |
2010年 | 6904篇 |
2009年 | 7883篇 |
2008年 | 8402篇 |
2007年 | 8294篇 |
2006年 | 7364篇 |
2005年 | 6497篇 |
2004年 | 6282篇 |
2003年 | 6553篇 |
2002年 | 6035篇 |
2001年 | 6513篇 |
2000年 | 5973篇 |
1999年 | 6388篇 |
1998年 | 16480篇 |
1997年 | 11408篇 |
1996年 | 8792篇 |
1995年 | 6606篇 |
1994年 | 5901篇 |
1993年 | 5842篇 |
1992年 | 4131篇 |
1991年 | 4020篇 |
1990年 | 3857篇 |
1989年 | 3648篇 |
1988年 | 3559篇 |
1987年 | 3017篇 |
1986年 | 2941篇 |
1985年 | 3206篇 |
1984年 | 2926篇 |
1983年 | 2828篇 |
1982年 | 2636篇 |
1981年 | 2542篇 |
1980年 | 2461篇 |
1979年 | 2305篇 |
1978年 | 2107篇 |
1977年 | 2604篇 |
1976年 | 3562篇 |
1975年 | 1764篇 |
1974年 | 1729篇 |
1973年 | 1665篇 |
1972年 | 1465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Die Regelung über die Erlangung der Parteistellung übergangener Nachbarn durch Geltendmachung von Einwendungen bis l?ngstens
drei Monate nach dem angezeigten Baubeginn ist wegen der Anknüpfung an einen untauglichen Zeitpunkt verfassungswidrig. 相似文献
102.
M E Rentschler S R Platt K Berg J Dumpert D Oleynikov S M Farritor 《IEEE transactions on information technology in biomedicine》2008,12(1):66-75
Long-term human space exploration will require contingencies for emergency medical procedures including some capability to perform surgery. The ability to perform minimally invasive surgery (MIS) would be an important capability. The use of small incisions reduces surgical risk, but also eliminates the ability of the surgeon to view and touch the surgical environment directly. Robotic surgery, or telerobotic surgery, may provide emergency surgical care in remote or harsh environments such as space flight, or extremely forward environments such as battlefields. However, because current surgical robots are large and require extensive support personnel, their implementation has remained limited in forward environments, and they would be difficult, or impossible, to use in space flight or on battlefields. This paper presents experimental analysis of miniature fixed-base and mobile in vivo robots to support MIS surgery in remote and harsh environments. The objective is to develop wireless imaging and task-assisting robots that can be placed inside the abdominal cavity during surgery. Such robots will provide surgical task assistance and enable an on-site or remote surgeon to view the surgical environment from multiple angles. This approach is applicable to long-duration space flight, battlefield situations, and for traditional medical centers and other remote surgical locations. 相似文献
103.
E. M. Zobov M. E. Zobov F. S. Gabibov I. K. Kamilov F. I. Manyakhin E. K. Naimi 《Semiconductors》2008,42(3):277-280
The results of the effect of ultrasonic treatment of ZnSe crystals on the structure of the energy spectrum of electronic states of centers with deep levels forming photoelectric and luminescent properties of this compound are presented. It is for the first time proved experimentally that the climb of edge dislocations under the effect of ultrasound leads to regrouping and generation of defects forming deep levels, which manifest themselves in phenomena of photosensitivity and radiative recombination. 相似文献
104.
Rajoo R. Lim S.S. Wong E.H. Hnin W.Y. Seah S.K.W. Tay A.A.O. Iyer M. Tummala R.R. 《Advanced Packaging, IEEE Transactions on》2008,31(2):377-385
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps. 相似文献
105.
Zhiping Lin Xu L. Bose N.K. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(1):445-461
106.
Effect of Thickness of the p-AlGaN Electron Blocking Layer on the Improvement of ESD Characteristics in GaN-Based LEDs 总被引:1,自引:0,他引:1
Chung-Hsun Jang Sheu J.K. Tsai C.M. Shei S.C. Lai W.C. Chang S.J. 《Photonics Technology Letters, IEEE》2008,20(13):1142-1144
The following letter presents a study regarding GaN-based light-emitting diodes (LEDs) with p-type AlGaN electron blocking layers (EBLs) of different thicknesses. The study revealed that the LEDs could endure higher electrostatic discharge (ESD) levels as the thickness of the AlGaN EBL increased. The observed improvement in the ESD endurance ability could be attributed to the fact that the thickened p-AlGaN EBL may partly fill the dislocation-related pits that occur on the surface of the InGaN-GaN multiple-quantum well (MQW) and that are due to the strain and the low-temperature-growth process. If these dislocation-related pits are not partly suppressed, they will eventually result in numerous surface pits associated with threading dislocations that intersect the InGaN-GaN (MQW), thereby reducing the ESD endurance ability. The results of the experiment show that the ESD endurance voltages could increase from 1500 to 6000 V when the thickness of the p-AlGaN EBL in the GaN LEDs is increased from 32.5 to 130 nm, while the forward voltages and light output powers remained almost the same. 相似文献
107.
108.
109.
Theoretical and experimetal methods have been developed to characterize the effect of mechanical loading on the mesoscopic
and macroscopic mechanical state of polycrystalline materials. Ferritic and austenitic single-phase materials were first analyzed,
then phase interaction was studied in a multiductile phase material (austeno-ferritic duplex steel) and a natural reinforced
composite (pearlitic steel). The theoretical method is based on the self-consistent approach in which elastic and plastic
characteristics of the phases have been applied through the micromechanical behavior of single-crystal-using slip systems
and microscopic hardening. The effects of a crystallographic texture and phase interaction during loading and after unloading
were studied. The elastic and plastic anisotropy of the grains having the same crystallographic orientation were assessed
by diffraction strain analysis. The simulation was compared with the experiments performed using the X-ray diffraction technique.
In the considered duplex and pearlitic steels, it was observed that the ferrite stress state is much lower than the austenite
and cementite ones. The results of diffraction strain distribution have showed the pertinence of the models and give valuable
information, for example, for the yield stress and the hardening parameters of each phase in a two-phase material. 相似文献
110.