全文获取类型
收费全文 | 186858篇 |
免费 | 9772篇 |
国内免费 | 5995篇 |
专业分类
电工技术 | 7988篇 |
技术理论 | 1篇 |
综合类 | 6595篇 |
化学工业 | 23308篇 |
金属工艺 | 10660篇 |
机械仪表 | 9029篇 |
建筑科学 | 8938篇 |
矿业工程 | 3081篇 |
能源动力 | 5176篇 |
轻工业 | 11575篇 |
水利工程 | 2496篇 |
石油天然气 | 5058篇 |
武器工业 | 885篇 |
无线电 | 26052篇 |
一般工业技术 | 30815篇 |
冶金工业 | 28760篇 |
原子能技术 | 2366篇 |
自动化技术 | 19842篇 |
出版年
2024年 | 440篇 |
2023年 | 1422篇 |
2022年 | 3020篇 |
2021年 | 4164篇 |
2020年 | 3138篇 |
2019年 | 2795篇 |
2018年 | 3473篇 |
2017年 | 3760篇 |
2016年 | 3639篇 |
2015年 | 4668篇 |
2014年 | 5970篇 |
2013年 | 9996篇 |
2012年 | 8653篇 |
2011年 | 10319篇 |
2010年 | 9099篇 |
2009年 | 9672篇 |
2008年 | 9582篇 |
2007年 | 9615篇 |
2006年 | 8740篇 |
2005年 | 7658篇 |
2004年 | 6072篇 |
2003年 | 5437篇 |
2002年 | 4929篇 |
2001年 | 4938篇 |
2000年 | 4397篇 |
1999年 | 4679篇 |
1998年 | 10482篇 |
1997年 | 7095篇 |
1996年 | 5583篇 |
1995年 | 3839篇 |
1994年 | 3335篇 |
1993年 | 3132篇 |
1992年 | 1941篇 |
1991年 | 1839篇 |
1990年 | 1716篇 |
1989年 | 1488篇 |
1988年 | 1301篇 |
1987年 | 944篇 |
1986年 | 960篇 |
1985年 | 950篇 |
1984年 | 837篇 |
1983年 | 710篇 |
1982年 | 721篇 |
1981年 | 696篇 |
1980年 | 586篇 |
1979年 | 484篇 |
1978年 | 421篇 |
1977年 | 538篇 |
1976年 | 965篇 |
1975年 | 302篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
3.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. 相似文献
4.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
5.
Tao Feng Mingde Tong Shuotian Yao Hejun Li Shifeng Wen Hongjiao Lin 《Journal of the European Ceramic Society》2021,41(1):158-166
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. 相似文献
6.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
7.
Fenqi Du Dongmei Yang Yue Sun Yang Jiao Feng Teng Haibo Fan 《Ceramics International》2021,47(4):4963-4971
Ultrawide band gap semiconductor materials have attracted considerable attention in recent years owing to their great potential in the photocatalytic field. In this study, Zn-doped Ga2O3 nanofibers with various concentrations were synthesized via electrospinning; they exhibited a superior photocatalytic degradation performance of rhodamine B dye compared to that of undoped Ga2O3 nanofibers. The Zn dopant replaced Ga sites via replacement doping, which could increase the concentration of oxygen vacancies and lead to enhanced photocatalytic properties. When the Zn concentration increased, a Ga2O3/ZnGa2O4 hybrid structure formed, which could further enhance the photocatalytic performance. The separation of photogenerated carriers due to Zn doping and heterojunctions were the primary causes of the enhanced photocatalytic performance. This study provides experimental data for the fabrication of high-performance photocatalysts based on Ga2O3 nanomaterials. 相似文献
8.
9.
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
10.
Recently, the successful synthesis of wafer-scale single-crystal graphene, hexagonal boron nitride (hBN), and MoS2 on transition metal surfaces with step edges boosted the research interests in synthesizing wafer-scale 2D single crystals on high-index substrate surfaces. Here, using hBN growth on high-index Cu surfaces as an example, a systematic theoretical study to understand the epitaxial growth of 2D materials on various high-index surfaces is performed. It is revealed that hBN orientation on a high-index surface is highly dependent on the alignment of the step edges of the surface as well as the surface roughness. On an ideal high-index surface, well-aligned hBN islands can be easily achieved, whereas curved step edges on a rough surface can lead to the alignment of hBN along with different directions. This study shows that high-index surfaces with a large step density are robust for templating the epitaxial growth of 2D single crystals due to their large tolerance for surface roughness and provides a general guideline for the epitaxial growth of various 2D single crystals. 相似文献