全文获取类型
收费全文 | 2780篇 |
免费 | 110篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 149篇 |
综合类 | 11篇 |
化学工业 | 695篇 |
金属工艺 | 75篇 |
机械仪表 | 80篇 |
建筑科学 | 118篇 |
矿业工程 | 8篇 |
能源动力 | 100篇 |
轻工业 | 246篇 |
水利工程 | 10篇 |
石油天然气 | 18篇 |
无线电 | 224篇 |
一般工业技术 | 520篇 |
冶金工业 | 360篇 |
原子能技术 | 101篇 |
自动化技术 | 192篇 |
出版年
2024年 | 7篇 |
2023年 | 32篇 |
2022年 | 43篇 |
2021年 | 81篇 |
2020年 | 42篇 |
2019年 | 42篇 |
2018年 | 53篇 |
2017年 | 47篇 |
2016年 | 63篇 |
2015年 | 43篇 |
2014年 | 65篇 |
2013年 | 149篇 |
2012年 | 114篇 |
2011年 | 151篇 |
2010年 | 114篇 |
2009年 | 120篇 |
2008年 | 115篇 |
2007年 | 114篇 |
2006年 | 95篇 |
2005年 | 82篇 |
2004年 | 72篇 |
2003年 | 87篇 |
2002年 | 92篇 |
2001年 | 69篇 |
2000年 | 55篇 |
1999年 | 46篇 |
1998年 | 140篇 |
1997年 | 98篇 |
1996年 | 108篇 |
1995年 | 58篇 |
1994年 | 55篇 |
1993年 | 53篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1971年 | 6篇 |
排序方式: 共有2907条查询结果,搜索用时 140 毫秒
101.
102.
Jun Koyanagi Hideo Nagayama Satoru Yoneyama Takahira Aoki 《Mechanics of Time-Dependent Materials》2016,20(2):219-232
This paper presents the time dependence of the mesoscopic strain of a triaxial woven carbon-fiber-reinforced polymer under creep loading measured using digital image correlation (DIC). Two types of DIC techniques were employed for the measurement: conventional subset DIC and mesh DIC. Static tensile and creep tests were carried out, and the time dependence of the mesoscopic strain distribution was investigated by applying these techniques. The ultimate failure of this material is dominated by inter-bundle decohesion caused by relative rigid rotation and relating shear stress. Therefore, these were focused on in the present study. During the creep tests, the fiber directional strain, shear strain, and rotation were monitored using the DIC, and the mechanism for the increase in the specimen’s macro-strain over time was investigated based on the results obtained by the DIC measurement. 相似文献
103.
Takashi MINAMI Shohei ARAI Naoki KENMOCHI Hiroaki YASHIRO Chihiro TAKAHASHI Shinji KOBAYASHI Tohru MIZUUCHI Shinsuke OHSHIMA Satoshi YAMAMOTO Hiroyuki OKADA Kazunobu NAGASAKI Yuji NAKAMURA Kiyoshi HANATANI Shigeru KONOSHIMA Fumimichi SANO 《等离子体科学和技术》2013,(3):240-243
A new high repetition rate Nd:YAG Thomson scattering system is developed for the Heliotron J helical device.A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma.The system has 25 spatial points with ~10mm resolution.Two high repetition Nd:YAG lasers (>550mJ@ 50Hz) realize the measurement of the time evolution of the plasma profile with ~10ms time intervals.Scattered light is collected by a large concave mirror (D=800 mm,f/2.25) with a solid angle of ~100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form.The signal is amplified by newly designed fast preamplifiers with DC and AC output,which reduces the low frequency background noise.The signals are digitized with a multi-event QDC,fast gated integrators.The data acquisition is performed by a VME-based system operated by the CINOS. 相似文献
104.
Nanoimprint lithography has two basic steps. The first is the imprint step in which a mold with nanostructures on its surface is pressed into a resin film on a substrate, followed by removal of the mold. The second step is the residual layer removal by a reactive ion etching (RIE). There is no report whether the properties of the imprinted structure after RIE change or not. In this work, the authors evaluated the Young’s modulus of the imprinted pillar after residual layer removal by RIE. In this experiment, hydrogen silsesquioxane (HSQ), a type of spin-on-glass, was used as an imprint material. The residual layer was etched by RIE using CHF3 gas. The Young’s modulus of imprinted pillar after RIE was measured via cantilever method. The Young’s modulus of HSQ pillar after RIE was twice as much as that of HSQ pillar before RIE. From the Fourier transform infrared measurement, it was founds the chemical structure of HSQ was changed by forming network structure due to heating by RIE plasma energy. These results indicate that the mechanical property of imprinted structure was changed in the residual layer removal step by using RIE. 相似文献
105.
Invert traps have been successfully used to collect sediments at convenient locations within the sewer network, where large volumes of solids can be stored. In the present study, experiments have been performed in 15 cm wide and 5 m long channel for the measurement of retention ratios of five different invert trap configurations (namely, rectangular, trapezoidal with one side vertical, trapezoidal, trapezoidal with rectangular base, rectangular with trapezoidal base) having top width of 32 cm and depth of 28 cm with slots of three different sizes (namely, 5, 9 and 15 cm) for the flow of seven different sediment types (namely, two types of sand, glass beads and four types of plastic beads) at different flow rates for each trap. The flow rates selected in present study cover entire range of flow rate expected in channels during dry weather flow and monsoon. Flow field and retention ratio predictions for each invert trap configuration have been carried out using CFD modeling with the help of FLUENT software using Renormalization Group (RNG) k–ε along with Discrete Phase Model (DPM). The simulation results are capable of showing particle trajectories, the effect of flow rate and trap geometry on the flow patterns, developed within the trap. Based on CFD modeling and experimental measurements, it is concluded that the invert trap having rectangular shape with trapezoidal base is the most efficient trap configuration with highest sediment retention ratio. 相似文献
106.
107.
针对超高强钢在机械行业的广泛使用,焊接接头易出现淬硬脆化、裂纹等缺陷的情况,采用焊条电弧焊(SMAW)和药芯气体保护焊(FCAW-GS)组合的焊接方法,对API X52管线钢与Corus RQT 701超高强钢的焊接进行了工艺试验,并进行常规力学性能试验。结果表明,通过合理匹配焊接工艺参数,严格控制低热输入量及层间温度,实现了小熔合比的异种钢焊接,且焊接接头具有良好的力学性能,达到了标准和规格书的要求;异种高强钢焊接,采用SMAW打底焊接和FCAWGS填充并盖面的方法,焊接效率较单纯采用焊条电弧焊工艺提高2倍以上。 相似文献
108.
Yuki Sagawa Yuji Masubuchi Shinichi Kikkawa 《Journal of the American Ceramic Society》2019,102(1):109-117
Coloration of amorphous silica powder containing titania was investigated by nitridation in an ammonia flow. The oxide precursors were obtained by the hydrolysis of a mixture of tetraethyl orthosilicate (TEOS) and tetrabutoxy titanium (TBT). The color changed with the amount of TBT in the mixture, the hydrolysis pH and the ammonolysis temperature. The original white color of the 8 mol% TBT powder hydrolyzed under basic pH conditions changed to pale goldenrod at 700°C, then to dark olive green at 800°C, and further darkened with increasing ammonolysis temperature. A steel-blue color appeared at 900°C for the powder obtained with 3 mol% TBT, and increased in darkness at 1000°C. A similar bluish color was observed for powders obtained by acidic hydrolysis after ammonolysis above 900°C, and this was independent of the amount of titania, although the chroma decreased with increasing firing temperature for the powder with 3 mol% TBT. The ammonolysis powder products were characterized using X-ray diffraction (XRD), electron probe micro analysis (EPMA), transmission electron microscopy-electron energy-loss spectroscopy (TEM-EELS), scanning transmission electron microscopy-high-angle annular dark-field imaging (STEM-HAADF) and Ti–K edge X-ray absorption fine structure (XAFS). The color change was related to both precipitated TiN nanocrystals and residual titanium in the amorphous silica matrix. The TiN exhibited a goldish reflection and also plasmonic absorption from light blue to gray depending on the TiN crystallite size. The plasmonic absorption and resonance of nanocrystalline TiN will be useful similarly to that of gold in nanotechnology for various kinds of energy application. 相似文献
109.
This work compares the intercalation of K, Na, and Li in KxVPO4F (x ~ 0). The KxVPO4F (x ~ 0) cathode delivers reversible capacities of ≈90–100 mAh g?1 in K, Na, and Li cells, at an average voltage of ≈4.33 V for K, ≈3.98 V for Na, and ≈3.96 V for Li. This is so far the highest average voltage known for a K‐intercalation cathode. The lower voltage of Li insertion compared to Na is attributable to undercoordinated Li ions in the KxVPO4F (x ~ 0) framework. While the material shows high rate capability for all the alkali ions, Li migration in KxVPO4F (x ~ 0) is more difficult than with Na and K. This work suggests that a large cavity is not always good for insertion of alkali ions and cathode materials need to be suitably tailored to each intercalating ion species. 相似文献
110.
Koji Kamagata Christina Andica Ayumi Kato Yuya Saito Wataru Uchida Taku Hatano Matthew Lukies Takashi Ogawa Haruka Takeshige-Amano Toshiaki Akashi Akifumi Hagiwara Shohei Fujita Shigeki Aoki 《International journal of molecular sciences》2021,22(10)
There has been an increasing prevalence of neurodegenerative diseases with the rapid increase in aging societies worldwide. Biomarkers that can be used to detect pathological changes before the development of severe neuronal loss and consequently facilitate early intervention with disease-modifying therapeutic modalities are therefore urgently needed. Diffusion magnetic resonance imaging (MRI) is a promising tool that can be used to infer microstructural characteristics of the brain, such as microstructural integrity and complexity, as well as axonal density, order, and myelination, through the utilization of water molecules that are diffused within the tissue, with displacement at the micron scale. Diffusion tensor imaging is the most commonly used diffusion MRI technique to assess the pathophysiology of neurodegenerative diseases. However, diffusion tensor imaging has several limitations, and new technologies, including neurite orientation dispersion and density imaging, diffusion kurtosis imaging, and free-water imaging, have been recently developed as approaches to overcome these constraints. This review provides an overview of these technologies and their potential as biomarkers for the early diagnosis and disease progression of major neurodegenerative diseases. 相似文献