全文获取类型
收费全文 | 61199篇 |
免费 | 6648篇 |
国内免费 | 4700篇 |
专业分类
电工技术 | 5562篇 |
综合类 | 5976篇 |
化学工业 | 8349篇 |
金属工艺 | 3762篇 |
机械仪表 | 4339篇 |
建筑科学 | 4773篇 |
矿业工程 | 1958篇 |
能源动力 | 1845篇 |
轻工业 | 4546篇 |
水利工程 | 1557篇 |
石油天然气 | 2574篇 |
武器工业 | 982篇 |
无线电 | 7509篇 |
一般工业技术 | 6084篇 |
冶金工业 | 2117篇 |
原子能技术 | 889篇 |
自动化技术 | 9725篇 |
出版年
2024年 | 240篇 |
2023年 | 771篇 |
2022年 | 1760篇 |
2021年 | 2505篇 |
2020年 | 1932篇 |
2019年 | 1458篇 |
2018年 | 1597篇 |
2017年 | 1834篇 |
2016年 | 1643篇 |
2015年 | 2646篇 |
2014年 | 3301篇 |
2013年 | 4120篇 |
2012年 | 4638篇 |
2011年 | 4865篇 |
2010年 | 4711篇 |
2009年 | 4615篇 |
2008年 | 4501篇 |
2007年 | 4382篇 |
2006年 | 4042篇 |
2005年 | 3287篇 |
2004年 | 2587篇 |
2003年 | 2155篇 |
2002年 | 2198篇 |
2001年 | 1973篇 |
2000年 | 1401篇 |
1999年 | 858篇 |
1998年 | 478篇 |
1997年 | 387篇 |
1996年 | 352篇 |
1995年 | 279篇 |
1994年 | 210篇 |
1993年 | 194篇 |
1992年 | 159篇 |
1991年 | 93篇 |
1990年 | 94篇 |
1989年 | 61篇 |
1988年 | 53篇 |
1987年 | 24篇 |
1986年 | 32篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1976年 | 3篇 |
1973年 | 4篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
本文将完全互补码(Complete Complementary Code, CCC)应用于多输入多输出(Multiple Input Multiple Output, MIMO)雷达目标探测中,针对具有非零多普勒的多目标检测问题,提出一种基于广义普洛黑-修-莫尔斯(Generalized Prouhet-Thue-Morse, GPTM)序列和二项式系数加权的信号处理方法。该方法分别在发射端和接收端进行处理,在发射端采用GPTM序列设计方法调整脉冲的发射顺序,以降低由多普勒引起的距离旁瓣;在接收端通过二项式设计(Binomial Design, BD)方法为各接收脉冲加上不同权重,扩大目标多普勒附近的清洁区。为综合上述两次处理的优势,将两次处理得到的距离多普勒谱进行逐点最小化处理,得到最终的距离多普勒谱,然后进行有序恒虚警检测。仿真结果表明,本文所提的信号处理方法具有良好的旁瓣抑制效果和多普勒分辨率,能够有效检测出非零多普勒目标。 相似文献
2.
Peng Wang Yan Li Yujiao Qu Baowei Wang Jingxin Sun Chunwei Miao Ming Huang He Huang Congxiang Zhang 《International Journal of Food Science & Technology》2022,57(6):3428-3439
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP. 相似文献
3.
针对现有的混凝土裂缝检测算法在各种复杂环境中检测精度不够、鲁棒性不强的问题,根据深度学习理论和U-net模型,提出一种全U型网络的裂缝检测算法。首先,依照原U-net模型路线构建网络;然后,在每个池化层后都进行一次上采样,恢复其在池化层之前的特征图规格,并将其与池化之前的卷积层进行融合,将融合之后的特征图作为新的融合层与原U-net网络上采样之后的网络层进行融合;最后,为了验证算法的有效性,在测试集中进行实验。结果表明,所提算法的平均精确率可达到83.48%,召回率为85.08%,F1为84.11%,相较于原U-net分别提升了1.48%,4.68%和3.29%,在复杂环境中也能提取完整裂缝,保证了裂缝检测的鲁棒性。 相似文献
4.
5.
Shuhai Liu Ming Han Xiaolong Feng Qiuhong Yu Long Gu Longfei Wang Yong Qin Zhong Lin Wang 《Advanced functional materials》2021,31(17):2010339
Utilizing inner-crystal piezoelectric polarization charges to control carrier transport across a metal-semiconductor or semiconductor–semiconductor interface, piezotronic effect has great potential applications in smart micro/nano-electromechanical system (MEMS/NEMS), human-machine interfacing, and nanorobotics. However, current research on piezotronics has mainly focused on systems with only one or rather limited interfaces. Here, the statistical piezotronic effect is reported in ZnO bulk composited of nanoplatelets, of which the strain/stress-induced piezo-potential at the crystals’ interfaces can effectively gate the electrical transport of ZnO bulk. It is a statistical phenomenon of piezotronic modification of large numbers of interfaces, and the crystal orientation of inner ZnO nanoplatelets strongly influence the transport property of ZnO bulk. With optimum preferred orientation of ZnO nanoplatelets, the bulk exhibits an increased conductivity with decreasing stress at a high pressure range of 200–400 MPa, which has not been observed previously in bulk. A maximum sensitivity of 1.149 µS m−1 MPa−1 and a corresponding gauge factor of 467–589 have been achieved. As a statistical phenomenon of many piezotronic interfaces modulation, the proposed statistical piezotronic effect extends the connotation of piezotronics and promotes its practical applications in intelligent sensing. 相似文献
6.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
7.
8.
9.
10.