全文获取类型
收费全文 | 34816篇 |
免费 | 2732篇 |
国内免费 | 1265篇 |
专业分类
电工技术 | 1624篇 |
综合类 | 2015篇 |
化学工业 | 6116篇 |
金属工艺 | 1666篇 |
机械仪表 | 2000篇 |
建筑科学 | 3164篇 |
矿业工程 | 678篇 |
能源动力 | 1102篇 |
轻工业 | 2282篇 |
水利工程 | 526篇 |
石油天然气 | 1914篇 |
武器工业 | 222篇 |
无线电 | 4259篇 |
一般工业技术 | 4549篇 |
冶金工业 | 1825篇 |
原子能技术 | 451篇 |
自动化技术 | 4420篇 |
出版年
2024年 | 73篇 |
2023年 | 524篇 |
2022年 | 803篇 |
2021年 | 1245篇 |
2020年 | 950篇 |
2019年 | 828篇 |
2018年 | 890篇 |
2017年 | 1057篇 |
2016年 | 972篇 |
2015年 | 1251篇 |
2014年 | 1558篇 |
2013年 | 2013篇 |
2012年 | 2102篇 |
2011年 | 2265篇 |
2010年 | 1886篇 |
2009年 | 1895篇 |
2008年 | 1822篇 |
2007年 | 1792篇 |
2006年 | 1836篇 |
2005年 | 1623篇 |
2004年 | 1123篇 |
2003年 | 1001篇 |
2002年 | 989篇 |
2001年 | 831篇 |
2000年 | 886篇 |
1999年 | 966篇 |
1998年 | 940篇 |
1997年 | 778篇 |
1996年 | 770篇 |
1995年 | 643篇 |
1994年 | 504篇 |
1993年 | 461篇 |
1992年 | 315篇 |
1991年 | 234篇 |
1990年 | 236篇 |
1989年 | 169篇 |
1988年 | 132篇 |
1987年 | 92篇 |
1986年 | 74篇 |
1985年 | 52篇 |
1984年 | 45篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1973年 | 8篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ruochen Lan Qian Wang Chen Shen Rui Huang Jinying Bao Zhongping Zhang Lanying Zhang Huai Yang 《Advanced functional materials》2021,31(51):2106419
Stimuli-responsive photonic crystals (PCs) have been extensively studied due to their potential in fabrication of anti-counterfeiting devices and information storage. In this work, using Ca2+ ionic crosslinker, a cholesteric liquid crystalline network (CLCN) based PC able to simultaneously present visible and fluorescence pattern by moisture treatment is designed and prepared. The circularly polarized light from helical structure of CLCN makes the reflected pattern distinguishable under different circular polarizer, implying the unique advantage of this novel coating as anti-counterfeiting devices. More importantly, due to the thermochromic property of the liquid crystal monomers, permanent pattern is achievable by chemically crosslinking specific region at different temperature. By integrating chemically crosslinking and physically ionic crosslinking, a permanent pattern and a dynamic humidity responsive pattern can be incorporated in a single device, indicating the great potential of this novel photonic coating in information storage. 相似文献
42.
Machine Learning - Recently, some statistical topic modeling approaches have been widely applied in the field of supervised document classification. However, there are few researches on these... 相似文献
43.
Ningqin Deng He Tian Jian Zhang Jinming Jian Fan Wu Yang Shen Yi Yang Tian-Ling Ren 《半导体学报》2021,42(8):21-33
Black phosphorus(BP),an emerging two-dimensional material,is considered a promising candidate for next-genera-tion electronic and optoelectronic devices due to in-plane anisotropy,high mobility,and direct bandgap.However,BP devices face challenges due to their limited stability,photo-response speed,and detection range.To enhance BP with powerful electric-al and optical performance,the BP heterostructures can be created.In this review,the state-of-the-art heterostructures and their electrical and optoelectronic applications based on black phosphorus are discussed.Five parts introduce the perform-ance of BP-based devices,including black phosphorus sandwich structure by hBN with better stability and higher mobility,black phosphorus homojunction by dual-gate structure for optical applications,black phosphorus heterojunction with other 2D materials for faster photo-detection,black phosphorus heterojunction integration with 3D bulk material,and BP via As-doping tunable bandgap enabling photo-detection up to 8.2 μm.Finally,we discuss the challenges and prospects for BP electric-al and optical devices and applications. 相似文献
44.
Qiang Wang Lei Shen Tong Xue Gao Cheng Cheng Zhi Huang Hong Jin Fan Yuan Ping Feng 《Advanced functional materials》2021,31(2):2002187
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures. 相似文献
45.
Science China Technological Sciences - Despite the great success achieved by convolutional neural networks in addressing the raindrop removal problem, the still relatively blurry results call for... 相似文献
46.
A novel Fe-enriched lamella sandwich phase (χ-phase) has been found to precipitate along the basal (0001)Mg planes in the heat-treated Mg-Gd-Fe alloy and its structure is clearly revealed by means of atomic-resolution transmission electron microscopy.The layered χ-phase only has a thickness of mono-unit-cell and consists invariably of ten atomic layers stacking along the[0001]Mg direction,of which the outermost atomic layers had larger in-plane atom-pillar spacing than the inner layers.Fe/Gd atoms are mainly enriched in the outer four atomic layers in the χ-phase,forming two structurally unsymmetrical four-layer shells to sandwich the middle two Mg layers.An atomic model has been proposed for this layered sandwich-structured χ-phase. 相似文献
47.
利用信息可视化软件Cite Space,将2007年至2021年间WOS数据库中与城市公园小气候热舒适性相关的1445篇文献作为研究对象进行分析,制作相关知识图谱,可以实现研究前沿、研究热点、未来的发展趋势的可视化,为以后的研究提供参照. 相似文献
48.
The continuous and dense Ti–N compound layers with a thickness ranging from 0.7 to 2.1 μm were formed on the titanium by plasma nitriding at 700 °C for different times with hollow cathode discharge assistance. Scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the nitrided layer. XRD and XPS results showed that the compound layer was mainly composed of Ti2N phase. The corrosion current density of 4 h nitrided titanium was 0.016 μA/cm2 (cathode) and 0.03 μA/cm2 (anode), respectively. The electrical conductivity of samples was evaluated by means of the interfacial contact resistance (ICR). The value of 4 h nitrided titanium was 4.94 mΩ-cm2 which was much lower than that of original titanium 26.25 mΩ-cm2 under applied force of 150 Ncm?2 after corrosion test. The results showed that the electrical conductivity and corrosion resistance of the titanium bipolar plates (BPs) were apparently improved with the formation of Ti2N compound layer. 相似文献
49.
Yang Jinmeng Zhao Lanhao Shen Zhenzhong Gan Lei Xu Liqun 《Bulletin of Engineering Geology and the Environment》2021,80(3):2671-2685
Bulletin of Engineering Geology and the Environment - In large-scale hydropower projects, the anti-seepage curtain is an important measure to reduce the leakage of reservoirs and ensure the... 相似文献
50.
Yanru Shen Yongqi Tong Yuhao Zhao Lin Zhang Shi Bu Weigang Xu Chenye Pan Hong Ding Zhengjun Yang 《Advanced Powder Technology》2021,32(6):1858-1868
Aiming at the problems of low collection efficiency of fine particulate matter and large area occupied by existing electrostatic precipitators (ESP), a new type of horizontal electrode ESP is proposed. It has the advantages of accelerating turbulent coalescence, increasing the effective dust collecting area and increasing the particle driving speed. The performance of the new type of ESP is systematic studied through simulation and experiment at the same time, and the results matches well. By comparing the dust removal effect of the horizontal electrode ESP and the conventional ESP, it can be concluded that the horizontal electrode ESP has a better dust removal efficiency, and can still maintain a better dust removal effect under high air velocity. The dust removal efficiency of new ESP can reach above 98% under the experimental conditions. 相似文献