全文获取类型
收费全文 | 80151篇 |
免费 | 8940篇 |
国内免费 | 5724篇 |
专业分类
电工技术 | 6205篇 |
技术理论 | 3篇 |
综合类 | 7515篇 |
化学工业 | 11710篇 |
金属工艺 | 5202篇 |
机械仪表 | 5241篇 |
建筑科学 | 6770篇 |
矿业工程 | 2810篇 |
能源动力 | 2354篇 |
轻工业 | 7043篇 |
水利工程 | 2016篇 |
石油天然气 | 3481篇 |
武器工业 | 803篇 |
无线电 | 9057篇 |
一般工业技术 | 8053篇 |
冶金工业 | 3306篇 |
原子能技术 | 1327篇 |
自动化技术 | 11919篇 |
出版年
2024年 | 223篇 |
2023年 | 1413篇 |
2022年 | 2643篇 |
2021年 | 3696篇 |
2020年 | 2726篇 |
2019年 | 2387篇 |
2018年 | 2443篇 |
2017年 | 2630篇 |
2016年 | 2260篇 |
2015年 | 3372篇 |
2014年 | 4145篇 |
2013年 | 4920篇 |
2012年 | 5574篇 |
2011年 | 5872篇 |
2010年 | 5505篇 |
2009年 | 5172篇 |
2008年 | 5383篇 |
2007年 | 5078篇 |
2006年 | 4803篇 |
2005年 | 3786篇 |
2004年 | 3089篇 |
2003年 | 3146篇 |
2002年 | 3949篇 |
2001年 | 3342篇 |
2000年 | 2012篇 |
1999年 | 1314篇 |
1998年 | 704篇 |
1997年 | 620篇 |
1996年 | 590篇 |
1995年 | 482篇 |
1994年 | 385篇 |
1993年 | 267篇 |
1992年 | 228篇 |
1991年 | 133篇 |
1990年 | 120篇 |
1989年 | 95篇 |
1988年 | 81篇 |
1987年 | 40篇 |
1986年 | 37篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 13篇 |
1965年 | 2篇 |
1960年 | 1篇 |
1959年 | 7篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
非调质钢50MnSiV(/%:0. 50C,0.52S,1.20Mn,0.010P,0.025S,0.15Cr,0.10V,0.015Ti,0.015N)制造的新能源汽车电机轴,省去传统调质钢20CrMnTiH渗碳热处理和矫正精整工序,不仅可提高材料95%利用率和2天交货周期,还可以降低25%成本。50MnSiV钢抗拉强度1100 MPa、屈服强度858 MPa、冲击功48J。其静扭扭矩(4697 Nm)、疲劳寿命(±1600 Nm双向扭转12万次、±1400 Nm双向扭转27万次)较渗碳20CrMnTiH钢提高了27%和93%~140%,并且其性能指标和8万公里的路试结果均满足电机轴的技术要求。 相似文献
82.
针对田湾核电站机组功率运行期间堆外核测系统因故障而出现核功率突变的现象,通过对故障现象、信号处理原理、设备功能等的分析,总结归纳了较优的故障处理方法,便于维护人员能快速、有效地处理故障,降低故障处理对机组带来的停堆风险,保障机组安全稳定运行. 相似文献
83.
Jianlei Kuang Ting Xiao Xianjie Hou Qianfang Zheng Qi Wang Peng Jiang Wenbin Cao 《Ceramics International》2019,45(9):11660-11667
Thin thickness is always the pursuit of excellent electromagnetic wave absorbing materials. Herein, SiC nanowires with worm-like morphology were synthesized by microwave heating the mixture of expanded graphite and silica. The worm-like SiC nanowires exhibit an excellent microwave absorption ability at a thin thickness. With the filling ratio of SiC nanowires increases in the matrix, the dielectric loss and microwave absorbing ability are significantly enhanced; meanwhile the number of absorption peaks is gradually increased, and the absorption peaks also move toward a thinner thickness. When the nanowires filling ratio was 40?wt%, the minimum reflection loss reached down to ?35.2?dB and the effective absorption (RL?<??10?dB) bandwidth was 1.8?GHz?at a thickness of 1.3?mm. The possible growth mechanism of the worm-like SiC nanowires is that the intermediate reaction gas phases, SiO and CO, were confined in the relatively independent tiny pores of expanded graphite. This resulting in an excessive local gas phase pressure, which causes the nanowire growth direction changes randomly. 相似文献
84.
85.
86.
87.
Photothermal therapy (PTT) mediated by nanomaterial has become an attractive tumor treatment method due to its obvious advantages. Among various nanomaterials, melanin-like nanoparticles with nature biocompatibility and photothermal conversion properties have attracted more and more attention. Melanin is a natural biological macromolecule widely distributed in the body and displays many fascinating physicochemical properties such as excellent biocompatibility and prominent photothermal conversion ability. Due to the similar properties, Melanin-like nanoparticles have been extensively studied and become promising candidates for clinical application. In this review, we give a comprehensive introduction to the recent advancements of melanin-like nanoparticles in the field of photothermal therapy in the past decade. In this review, the synthesis pathway, internal mechanism and basic physical and chemical properties of melanin-like nanomaterials are systematically classified and evaluated. It also summarizes the application of melanin-like nanoparticles in bioimaging and tumor photothermal therapy (PTT)in detail and discussed the challenges they faced in clinical translation rationally. Overall, melanin-like nanoparticles still have significant room for development in the field of biomedicine and are expected to applied in clinical PTT in the future. 相似文献
88.
Mei Ying Liu Tu Lai Sun Xiao Li Zhu Xiao Qiang Liu He Tian Xiang Ming Chen 《Journal of the American Ceramic Society》2021,104(12):6393-6403
Hexagonal rare-earth ferrites (h-RFeO3) have attracted much scientific attention due to their room-temperature multiferroicity. However, it is still a hard job to obtain h-RFeO3 bulk materials because of the meta-stability of such hexagonal phase, and the evaluation of room-temperature ferroelectric and magnetoelectric characteristics in such materials is also a challengeable issue. In the present work, Yb1−xInxFeO3 ceramics with the stable hexagonal structure were obtained by introducing chemical pressure, where the unique ferroelectric domain structures of sixfold vortex combined with tenfold vortex with a typical size of ~400 nm were determined. Symmetry of the present system evolved from centrosymmetric orthorhombic Pbnm (x = 0–0.4) to non-centrosymmetric hexagonal P63cm (x = 0.5 and 0.6) with a ferroelectric polarization up to 3.2 μC/cm2, and finally to centrosymmetric hexagonal P63/mmc (x = 0.7 and 0.8). The Curie point decreased monotonically from 723 K to a temperature below room temperature with increasing x, and the antiferromagnetic phase transition above room temperature was determined for all compositions. Meanwhile, a large linear magnetoelectric coefficient (αME) up to 0.96 mV/cm Oe was obtained at room temperature, and this indicated the great application potential for magnetoelectric devices. 相似文献
89.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
90.
探讨长治市手足口病(HFMD)与气象因素的关联关系.利用Apriori关联规则算法挖掘不同气象因素组合引发手足口病的频繁程度.长治市手足口病的周高发、中等发病率与前一周的平均水汽压、气温具有显著相关性.而周低发病率与前一周的气温(最低、平均)、降水量存在显著相关性.长治市手足口病周发病率与气象因素存在一定的关联性,应根据气象条件进行流行风险评估,及时采取相应的防控措施. 相似文献