全文获取类型
收费全文 | 2548篇 |
免费 | 81篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 161篇 |
综合类 | 4篇 |
化学工业 | 937篇 |
金属工艺 | 73篇 |
机械仪表 | 58篇 |
建筑科学 | 72篇 |
矿业工程 | 2篇 |
能源动力 | 94篇 |
轻工业 | 291篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 144篇 |
一般工业技术 | 455篇 |
冶金工业 | 68篇 |
原子能技术 | 64篇 |
自动化技术 | 202篇 |
出版年
2023年 | 10篇 |
2022年 | 35篇 |
2021年 | 56篇 |
2020年 | 34篇 |
2019年 | 36篇 |
2018年 | 49篇 |
2017年 | 43篇 |
2016年 | 62篇 |
2015年 | 37篇 |
2014年 | 86篇 |
2013年 | 157篇 |
2012年 | 120篇 |
2011年 | 174篇 |
2010年 | 100篇 |
2009年 | 144篇 |
2008年 | 143篇 |
2007年 | 133篇 |
2006年 | 100篇 |
2005年 | 115篇 |
2004年 | 98篇 |
2003年 | 89篇 |
2002年 | 88篇 |
2001年 | 62篇 |
2000年 | 47篇 |
1999年 | 44篇 |
1998年 | 37篇 |
1997年 | 42篇 |
1996年 | 43篇 |
1995年 | 30篇 |
1994年 | 41篇 |
1993年 | 29篇 |
1992年 | 28篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 29篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有2635条查询结果,搜索用时 0 毫秒
61.
62.
Kazushi Yamanaka Noritaka Nakaso Takeshi Fukiura Dong Youn Sim 《Electrical Engineering in Japan》2009,168(1):41-51
A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817 相似文献
63.
Cationic polymerization behavior of β‐methylglycidyl ether derivatives and physical properties of their cationically cured materials 下载免费PDF全文
β‐Methylglycidyl ethers have been applied to Electrical and Electronic adhesives. However, there is no report about the detailed polymerization behavior and physical properties of their cured products. Hence, we investigated cationic polymerization behavior of bisphenol A di(β‐methylglycidyl) ether (Me‐BADGE) and physical properties of the cured products containing Me‐BADGE. DSC analysis suggested that Me‐BADGE could be cured completely at lower temperature than bisphenol A diglycidyl ether (BADGE). Physical properties were analyzed by dynamic viscoelastic analysis. Glass transition temperature (Tg) of BADGE homopolymer was 194°C. In contrast, the copolymer of BADGE (50 wt %) with Me‐BADGE (50 wt %) showed Tg at 124°C. According to the data of E’ and tan δ, crosslink density of the cured products decreased with increasing the Me‐BADGE content. The analysis of cationic polymerization of monofunctional β‐methylglycidyl ether suggested that the cationic polymerization proceeded not only through oxonium cation but also through carbocation formed by ring‐opening reaction of oxonium cation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42377. 相似文献
64.
Detecting when the process has changed is a classical problem in sequential analysis and is an important practical issue in statistical process control. This article is concerned about the binomial cumulative sum (CUSUM) control chart, which is extensively applied to industrial process control, health care, public health surveillance, and other fields. For the binomial CUSUM, a maximum likelihood estimator has been proposed to estimate the change point. In our article, following a decision theoretic approach, we develop a new estimator that aims to improve the existing methods. For interval estimation, we propose a parametric bootstrap procedure to construct the confidence set of the change point. We compare our proposed method with the maximum likelihood estimator and Page's last zero estimator in terms of mean squared error by simulations. We find that the proposed method gives more unbiased and robust results than the existing procedures under various parameter designs. We analyze jewelry manufacturing data for illustration. 相似文献
65.
Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers 下载免费PDF全文
Shahin Kazemi Mohammad Reza Mohaddes Mojtahedi Wataru Takarada Takeshi Kikutani 《应用聚合物科学杂志》2014,131(6)
Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996. 相似文献
66.
Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior 下载免费PDF全文
In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO3 was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO3 mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO3 maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237. 相似文献
67.
The mechanical force to polymeric materials in vacuum at 77 K produces mechano radicals, mechano anions and mechano cations due to homogeneous and heterogeneous scissions of the covalent bonds comprising polymer main chain. The ionic degree of the covalent bond was estimated by calculating the “absolute ΔMulliken atomic charge,” which was defined as the difference between the Mulliken atomic charges of the two adjacent atoms comprising the covalent bond of the polymer main chain. The ionic yield of the covalent bond increased with increasing the absolute ΔMulliken atomic charge. The empirical formula for the ionic yield was obtained with the absolute ΔMulliken atomic charge, and indicates that the ionic yield could be estimated from its chemical structure. 相似文献
68.
Ninomiya Yuma Sasaki Hideaki Yoshikawa Takeshi Maeda Masafumi 《Metallurgical and Materials Transactions B》2019,50(1):407-415
Metallurgical and Materials Transactions B - The dissolution and passivation of pure Cu and Cu-5 wt pct Ag anodes in H2SO4-CuSO4 electrolyte were investigated by a direct... 相似文献
69.
Osteocytes connect with neighboring osteocytes and osteoblasts through their processes and form an osteocyte network. Shear stress on osteocytes, which is induced by fluid flow in the lacunae and canaliculi, has been proposed as an important mechanism for mechanoresponses. The lacunocanalicular structure is differentially developed in the compression and tension sides of femoral cortical bone and the compression side is more organized and has denser and thinner canaliculi. Mice with an impaired lacunocanalicular structure may be useful for evaluation of the relationship between lacunocanalicular structure and mechanoresponses, although their bone component cells are not normal. We show three examples of mice with an impaired lacunocanalicular structure. Ablation of osteocytes by diphtheria toxin caused massive osteocyte apoptosis, necrosis or secondary necrosis that occurred after apoptosis. Osteoblast-specific Bcl2 transgenic mice were found to have a reduced number of osteocyte processes and canaliculi, which caused massive osteocyte apoptosis and a completely interrupted lacunocanalicular network. Osteoblast-specific Sp7 transgenic mice were also revealed to have a reduced number of osteocyte processes and canaliculi, as well as an impaired, but functionally connected, lacunocanalicular network. Here, we show the phenotypes of these mice in physiological and unloaded conditions and deduce the relationship between lacunocanalicular structure and mechanoresponses. 相似文献
70.
Hideki Shige Toshitsugu Ishikawa Michio Suzukawa Masato Nishiwaki Takeshi Yamashita Kei Nakajima Toshimitsu Ito Kenji Higashi Makoto Ayaori Atsushi Yonemura Paul Nestel Haruo Nakamura 《Lipids》1998,33(12):1169-1175
The effects of vitamin E on cholesteryl ester (CE) metabolism in 1774 cells were examined. Pretreatment of 1774 cells with
vitamin E at concentrations above 50 μM significantly decreased acetylated low density lipoprotein (LDL)-induced incorporation
of [14C]oleate into CF in cells in a dose-dependent manner. This was partly due to vitamin E Also significantly inhibiting the uptake
of [3H]CE-labeled acetylated LDL by 1774 cells. A trend existed toward suppression of acyl-CoA:cholesterol acyltransferase (ACAT)
activity in the cell lysate at high vitamin E concentration, but there was no effect on hydrolysis of CE. These data indicate
that vitamin E reduces the uptake of modified LDL and suppresses ACAT activity, resulting in less cholesterol esterification
in macrophages; a novel mechanism underlying the antiatherogenic properties of vitamin E. 相似文献