全文获取类型
收费全文 | 3169篇 |
免费 | 117篇 |
国内免费 | 16篇 |
学科分类
工业技术 | 3302篇 |
出版年
2023年 | 42篇 |
2022年 | 73篇 |
2021年 | 83篇 |
2020年 | 76篇 |
2019年 | 75篇 |
2018年 | 92篇 |
2017年 | 85篇 |
2016年 | 113篇 |
2015年 | 76篇 |
2014年 | 97篇 |
2013年 | 207篇 |
2012年 | 117篇 |
2011年 | 155篇 |
2010年 | 129篇 |
2009年 | 113篇 |
2008年 | 118篇 |
2007年 | 120篇 |
2006年 | 104篇 |
2005年 | 84篇 |
2004年 | 63篇 |
2003年 | 61篇 |
2002年 | 72篇 |
2001年 | 56篇 |
2000年 | 57篇 |
1999年 | 56篇 |
1998年 | 111篇 |
1997年 | 80篇 |
1996年 | 83篇 |
1995年 | 51篇 |
1994年 | 49篇 |
1993年 | 46篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 40篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1984年 | 22篇 |
1983年 | 32篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 35篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 22篇 |
1975年 | 11篇 |
1972年 | 10篇 |
排序方式: 共有3302条查询结果,搜索用时 15 毫秒
1.
Wireless Networks - Unmanned Aerial Vehicles (UAVs) deployed as flying base stations is a promising technology for enhancing the quality of service (QoS) and quick recovery from unexpected damages... 相似文献
2.
Novel lead-free (1-x)Ba0·9Ca0·1Ti0·9Zr0·1O3-xSrNb2O6 ceramics were synthesized via a two-step high energy ball milling process. The evolution of microstructural properties, phase transformation, and energy storage characteristics was comprehensively investigated to assess the applicability of material in multi-layered ceramic capacitors. The substitution of SrNb2O6 (SNO) in Ba0·9Ca0·1Ti0·9Zr0·1O3 (BTCZ) has resulted in substantial improvement in materials density along with a small increase in the grain size of the synthesized ceramic. A thorough microstructural investigation indicates an excellent dispersibility and compatibility between BTCZ and SNO phases. With an increase in SNO substitution, a transition from typical ferroelectric to relaxor ferroelectric has been observed, which has led to a significantly slimmer ferroelectric loop along with frequency dispersive dielectric properties. The optimized composition (i.e., x = 0.10) exhibits an ultra-high recoverable energy density of 2.68 J/cm3 along with a moderately high energy efficiency of 83.4%. Further, SNO substituted samples have also shown an enhancement in breakdown strength. The improvement in energy storage performance and breakdown strength of SNO substituted BTCZ composites are mainly attributed to relatively homogeneous grain morphology, optimum grain size, microstructural density, and improved grain boundary interface. 相似文献
3.
Bakhale Mugdha Hemalatha V. Dhanalakshmi Samiappan Kumar R. Siddharth Jain M. 《Wireless Personal Communications》2020,110(2):573-592
Wireless Personal Communications - A relatively new area of research and development is Swarm Robotics. It is a part of the swarm intelligence field. In the proposed paper, we shall use swarm... 相似文献
4.
Wireless Personal Communications - Effect of combination of dual split ring resonator and electromagnetic bandgap structures over substrate integrated waveguide and half-mode substrate integrated... 相似文献
5.
ABSTRACTIn India, of late, micro-irrigation has received considerable policy focus. However, as of 2017, only about 10% of the potential area is under micro-irrigation. The present study analyzes the pattern and equity issues of distribution of micro-irrigation in India and identifies the potential correlates. The regression analysis reveals that the stage of groundwater development and agro-climatic differences significantly influence the spread of micro-irrigation. The relatively low spread of micro-irrigation in states with over-exploited groundwater needs attention. Overall, the study points to the need to revamp the current micro-irrigation development programmes, which focus excessively on subsidy. 相似文献
6.
Harry G. Sherman Jacqueline M. Hicks Akhil Jain Jeremy J. Titman Prof. Cameron Alexander Snow Stolnik Frankie J. Rawson 《Chembiochem : a European journal of chemical biology》2019,20(8):1008-1013
A model cancer cell line was used to initiate polymerisation of pyrrole to form the conducting material polypyrrole. The polymerisation was shown to occur through the action of cytosolic exudates rather than that of the membrane redox sites that normally control the oxidation state of iron as ferricyanide or ferrocyanide. The data demonstrate for the first time that mammalian cells can be used to initiate synthesis of conducting polymers and suggest a possible route to detection of cell damage and/or transcellular processes through in situ and amplifiable signal generation. 相似文献
7.
Real-Time Systems - With continuous technology scaling, the power density and hence the temperature of Network-on-Chip (NoC) may increase rapidly. This in-turn degrades the performance of the chip... 相似文献
8.
To evaluate the fill of internal resorption cavities obturated with thermoplasticized gutta‐percha and GuttaFlow2 using CT scan. Twenty human maxillary anterior teeth were selected and root canals were prepared using ProTaper system to size F3. Irrigation was performed with 5 ml of 2.5% sodium hypochlorite (NaOCl) and 5 ml of 17% ethylenediaminetetraacetic acid (EDTA). Each root was then sectioned horizontally into two halves and semicircular cavities were prepared around the periphery of the root canal opening of each root half, using a round bur. Both the root halves were then fixed using cyanoacrylate glue. All the specimens were subjected to preoperative CT scan analysis to determine the volume of internal cavities. The samples were then randomly divided into two groups. In Group 1, the specimens were obturated with thermoplasticized gutta‐percha (E&Q system) and specimens in Group 2 were obturated using GuttaFlow2. All specimens were then subjected to postoperative CT scan analysis. The volume of voids in internal resorptive cavities were calculated, which was then used to estimate the amount of gutta‐percha filled. There was no significant difference in volume of internal resorptive cavities between thermoplasticized gutta‐percha and GuttaFlow2 groups before obturation (p = 0.466). However, after obturation there was a significant difference between both the groups, in which GuttaFlow2 demonstrated better fill (p = .014). Thermoplasticized gutta‐percha filled 81% of internal resorptive cavity while GuttaFlow2 filled 91%, respectively. GuttaFlow2 showed better fill than thermoplasticized gutta‐percha in the filling of internal resorptive cavities. 相似文献
9.
Singh Bikesh K. Jain Pankaj Banchhor Sumit K. Verma Kesari 《Multimedia Tools and Applications》2019,78(16):22421-22444
Multimedia Tools and Applications - Performance of computerized diagnostic systems yearning to be approved by medical regulatory bodies must meet the expectations of human experts. Highly accurate... 相似文献
10.