全文获取类型
收费全文 | 259572篇 |
免费 | 3804篇 |
国内免费 | 744篇 |
专业分类
电工技术 | 4732篇 |
综合类 | 800篇 |
化学工业 | 42845篇 |
金属工艺 | 9844篇 |
机械仪表 | 8076篇 |
建筑科学 | 6248篇 |
矿业工程 | 1570篇 |
能源动力 | 5681篇 |
轻工业 | 26663篇 |
水利工程 | 2704篇 |
石油天然气 | 5259篇 |
武器工业 | 59篇 |
无线电 | 27127篇 |
一般工业技术 | 47230篇 |
冶金工业 | 48416篇 |
原子能技术 | 6085篇 |
自动化技术 | 20781篇 |
出版年
2021年 | 2548篇 |
2019年 | 2337篇 |
2018年 | 3848篇 |
2017年 | 3765篇 |
2016年 | 4058篇 |
2015年 | 2568篇 |
2014年 | 4394篇 |
2013年 | 11132篇 |
2012年 | 6870篇 |
2011年 | 9180篇 |
2010年 | 7231篇 |
2009年 | 7971篇 |
2008年 | 8320篇 |
2007年 | 8445篇 |
2006年 | 7529篇 |
2005年 | 6596篇 |
2004年 | 6422篇 |
2003年 | 6451篇 |
2002年 | 6800篇 |
2001年 | 6516篇 |
2000年 | 5921篇 |
1999年 | 5767篇 |
1998年 | 13650篇 |
1997年 | 9619篇 |
1996年 | 7378篇 |
1995年 | 5689篇 |
1994年 | 5004篇 |
1993年 | 4918篇 |
1992年 | 3839篇 |
1991年 | 3523篇 |
1990年 | 3717篇 |
1989年 | 3581篇 |
1988年 | 3419篇 |
1987年 | 2992篇 |
1986年 | 3032篇 |
1985年 | 3507篇 |
1984年 | 3295篇 |
1983年 | 2977篇 |
1982年 | 2813篇 |
1981年 | 2909篇 |
1980年 | 2800篇 |
1979年 | 2676篇 |
1978年 | 2724篇 |
1977年 | 3036篇 |
1976年 | 3973篇 |
1975年 | 2414篇 |
1974年 | 2272篇 |
1973年 | 2419篇 |
1972年 | 1997篇 |
1971年 | 1882篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Julio E. Trevino Swati Mohan Alexandra E. Salinas Emilia Cueva Karen Lozano 《应用聚合物科学杂志》2021,138(28):50665
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some. 相似文献
5.
Katia Varani Fabrizio Vincenzi Silvia Pasquini Irene Blo Simona Salati Matteo Cadossi Monica De Mattei 《International journal of molecular sciences》2021,22(2)
Mesenchymal stem cells (MSCs) are the main cell players in tissue repair and thanks to their self-renewal and multi-lineage differentiation capabilities, they gained significant attention as cell source for tissue engineering (TE) approaches aimed at restoring bone and cartilage defects. Despite significant progress, their therapeutic application remains debated: the TE construct often fails to completely restore the biomechanical properties of the native tissue, leading to poor clinical outcomes in the long term. Pulsed electromagnetic fields (PEMFs) are currently used as a safe and non-invasive treatment to enhance bone healing and to provide joint protection. PEMFs enhance both osteogenic and chondrogenic differentiation of MSCs. Here, we provide extensive review of the signaling pathways modulated by PEMFs during MSCs osteogenic and chondrogenic differentiation. Particular attention has been given to the PEMF-mediated activation of the adenosine signaling and their regulation of the inflammatory response as key player in TE approaches. Overall, the application of PEMFs in tissue repair is foreseen: (1) in vitro: to improve the functional and mechanical properties of the engineered construct; (2) in vivo: (i) to favor graft integration, (ii) to control the local inflammatory response, and (iii) to foster tissue repair from both implanted and resident MSCs cells. 相似文献
6.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
7.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
8.
Jiajia Suo Bowen Yang Edoardo Mosconi Hyeon-Seo Choi YeonJu Kim Shaik M. Zakeeruddin Filippo De Angelis Michael Grätzel Hui-Seon Kim Anders Hagfeldt 《Advanced functional materials》2021,31(34):2102902
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions. 相似文献
9.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献
10.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献