全文获取类型
收费全文 | 8993篇 |
免费 | 603篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 98篇 |
综合类 | 8篇 |
化学工业 | 2324篇 |
金属工艺 | 143篇 |
机械仪表 | 187篇 |
建筑科学 | 424篇 |
矿业工程 | 20篇 |
能源动力 | 278篇 |
轻工业 | 793篇 |
水利工程 | 59篇 |
石油天然气 | 20篇 |
无线电 | 1045篇 |
一般工业技术 | 1587篇 |
冶金工业 | 1118篇 |
原子能技术 | 106篇 |
自动化技术 | 1401篇 |
出版年
2022年 | 35篇 |
2021年 | 114篇 |
2020年 | 105篇 |
2019年 | 160篇 |
2018年 | 198篇 |
2017年 | 214篇 |
2016年 | 281篇 |
2015年 | 214篇 |
2014年 | 304篇 |
2013年 | 551篇 |
2012年 | 422篇 |
2011年 | 497篇 |
2010年 | 423篇 |
2009年 | 427篇 |
2008年 | 438篇 |
2007年 | 387篇 |
2006年 | 395篇 |
2005年 | 308篇 |
2004年 | 305篇 |
2003年 | 267篇 |
2002年 | 246篇 |
2001年 | 180篇 |
2000年 | 148篇 |
1999年 | 127篇 |
1998年 | 214篇 |
1997年 | 180篇 |
1996年 | 161篇 |
1995年 | 159篇 |
1994年 | 165篇 |
1993年 | 138篇 |
1992年 | 106篇 |
1991年 | 76篇 |
1990年 | 103篇 |
1989年 | 91篇 |
1988年 | 76篇 |
1987年 | 80篇 |
1986年 | 59篇 |
1985年 | 119篇 |
1984年 | 105篇 |
1983年 | 93篇 |
1982年 | 84篇 |
1981年 | 114篇 |
1980年 | 75篇 |
1979年 | 88篇 |
1978年 | 34篇 |
1977年 | 74篇 |
1976年 | 75篇 |
1975年 | 61篇 |
1974年 | 49篇 |
1973年 | 49篇 |
排序方式: 共有9611条查询结果,搜索用时 15 毫秒
11.
Nielsen Guillaume Coudert Lucie Janin Amelie Blais Jean Francois Mercier Guy 《Mine Water and the Environment》2019,38(1):104-118
Mine Water and the Environment - Acid mine drainage (AMD) is a major environmental challenge for the mining industry in northern climates. Laboratory-scale experiments were conducted to test... 相似文献
12.
13.
14.
Multimedia Tools and Applications - Color Space Conversion (CSC) in image processing applications, demands computationally simple floating point multipliers consuming less area and power. This... 相似文献
15.
We developed a simple solution mixing and molding process for the incorporation of graphene nano-flakes (GNFs) in polymer films. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(ethylene-co-methacrylic acid) (PEMAA) were used for preparation of the samples. The orientation and stacking of GNFs were confirmed using a scanning electron microscope. The thermal conductivity values for these composites were obtained using (1) laser flash method (commercially available) and (2) an optothermal Raman (OTR) technique (homemade device). The former measures the thermal diffusivity (α) and one needs to measure the density (ρ) and the heat capacity (Cp) of the composites in order to measure the in-plane thermal conductivity (κ = α.ρ.Cp), while the latter measures the in-plane thermal conductivity directly from the relation between the excitation power and the position of the Raman resonance. The data obtained from Raman spectroscopy were analyzed, assuming heat propagation in three and two dimensions. The Raman results obtained based on the two-dimensional model were very close to the results obtained using the laser flash method with less than 10% difference. The OTRspectroscopy was found to be a promising technique for measuring the in-plane thermal conductivity of carbon-based polymer composites. PVDF-HFP and PEMAA composite films with very high in-plane thermal conductivity (25 W m−1 K−1) were obtained through the incorporation of GNFs (20 wt % concentration). Considering a very low thermal conductivity of these polymers (<0.2 W m−1 K−1), this corresponds to a large enhancement of roughly 12 400%. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48927. 相似文献
16.
Naila Boudaoud Samira Benali Rosica Mincheva Hamid Satha Jean‐Marie Raquez Philippe Dubois 《Polymer International》2018,67(10):1393-1400
The hydrolytic degradation of poly(l ‐lactic acid)/poly(methyl methacrylate) (PLLA/PMMA) blends was carried out by the immersion of thin films in buffer solutions (pH = 7.24) in a shaking water bath at 60 °C for 38 days. The PLA/PMMA blends (0/100; 30/70; 50/50; 70/30; 100/0) were obtained by melt blending using a Brabender internal mixer and shaped into thin films of about 150 µm in thickness. Considering that PMMA does not undergo hydrolytic degradation, that of PLLA was followed via evolution of PLA molecular weight (recorded by size exclusion chromatography), thermal parameters (differential scanning calorimetry (DSC)) and morphology of the films (scanning transmission electron microscopy). The results reveal a completely different degradation pathway of the blends depending on the polymethacrylate/polyester weight ratio. DSC data suggest that, during hydrolysis at higher PMMA content, the polyester amorphous chains, more sensitive to water, are degraded before being able to crystallize, while at higher PLLA content, the crystallization is favoured leading to a sample more resistant to hydrolysis. In other words, and quite unexpectedly, increasing the content of water‐sensitive PLLA in the PLLA/PMMA blends does not mean de facto faster hydrolytic degradation of the resulting materials. © 2018 Society of Chemical Industry 相似文献
17.
18.
19.
20.
Neska El Haouij Raja Ghozi Jean‐Michel Poggi Sylvie Sevestre‐Ghalila Mriem Jaïdane 《Quality and Reliability Engineering International》2019,35(5):1502-1513
This paper characterizes stress levels via a self‐similarity analysis of the electrodermal activity (EDA) collected in a real‐world driving context. To characterize the EDA richness over scales, the fractional Brownian motion (FBM) process and its corresponding exponent H, estimated via a wavelet‐based approach, are used. Specifically, an automatic scale range selection is proposed in order to detect the linearity in a log scale diagram. The procedure is applied to the EDA signals, from the open database drivedb, originally captured on the foot and the hand of the drivers during a real‐world driving experiment, designed to evoke different levels of arousal and stress. The estimated Hurst exponent H offers a distinction in stress levels when driving in highway versus city, with a reference to restful state of minimal stress level. Specifically, the estimated H values tend to decrease when the driving environmental complexity increases. In addition, the estimated H values on the foot EDA signals allow a better characterization of the driving task than that of hand EDA. The self‐similarity analysis was applied to various physiological signals in literature but not to the EDA so far, a signal which was found to correlate most with human affect. The proposed analysis could be useful in real‐time monitoring of stress levels in urban driving spaces, among other applications. 相似文献