全文获取类型
收费全文 | 265篇 |
免费 | 8篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 7篇 |
综合类 | 2篇 |
化学工业 | 71篇 |
金属工艺 | 5篇 |
机械仪表 | 11篇 |
建筑科学 | 8篇 |
能源动力 | 4篇 |
轻工业 | 9篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 10篇 |
一般工业技术 | 28篇 |
冶金工业 | 101篇 |
原子能技术 | 1篇 |
自动化技术 | 18篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 3篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 34篇 |
1997年 | 20篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 8篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1961年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有279条查询结果,搜索用时 453 毫秒
61.
Cardiovascular disease is the leading cause of mortality in postmenopausal women in developed countries. A possible cardioprotective role of hormone replacement therapy (HRT) is suggested by epidemiologic studies of HRT and reduced risk of coronary heart disease, as well as by randomized trials of HRT and lipid subfractions. Estrogen has beneficial effects on the lipid profile, raising high-density lipoprotein cholesterol levels and reducing low-density lipoprotein cholesterol levels each by approximately 10%. Other possible biologic mechanisms include beneficial effects on vascular function, oxidative status, endothelial-dependent vasodilation, intimal hyperplasia and insulin sensitivity. Estrogen's net effects on coagulation and fibrinolysis are less clear. Estrogen replacement therapy is associated with decreased atherosclerosis in several animal models. However, most of the available data on HRT derive from observational studies or small randomized trials assessing biologic intermediates rather than clinical events. Further research, including large-scale randomized clinical trials, are required to evaluate definitively the role of estrogen replacement therapy, especially given uncertainties about the effects of combined estrogen-progestin therapy and the balance of benefits and risk of this common intervention in postmenopausal women. 相似文献
62.
63.
An experimental study was made of single fibers rotating and bending in Couette flow of a Newtonian liquid. A previous result for critical fiber buckling was re-tested and found satisfactory, and the transition between ‘springy’ and ‘snake’ rotation was delineated. The minimum radius, of curvature achieved during rotation in the “snake orbit” regime was measured as a function of fiber aspect ratio, Young's modulus, and fluid shear stress. Two correlations are presented which are constrained to satisfy limiting conditions for very stiff and very flexible fibers. Together with a result from thin rod theory, these correlations may be used to predict breaking conditions for fibers of known Young's modulus and ultimate tensile strength. Predictions are tested in experiments where two types of glass fiber are broken in suspension and found satisfactory. Results show that several reinforcing materials will probably break within the range of conditions covered by our experiments, or in a region which can be treated by extrapolation from our results. 相似文献
64.
A systematic surface fluorination of high-density polyethylene was carried out using CF4, CF3H, CF3Cl, and CF3Br, in a radio-frequency glow discharge. Based on ESCA and wettability measurements, all of these compounds provided a fluorocarbon layer on high-density polyethylene surface, but the fluorine to carbon ratio and extractability of the films were strongly dependent on the starting materials and the location of the sample specimen in the reactor chamber as well as the duration of the reaction. The results with vertically held, CF3H-treated samples showed a high level of nonextractable surface fluorination and very little change in wetting properties before and after extraction with CF2ClCFCl2. 相似文献
65.
Gui Zhi Li T. Matsuda A. Nishioka K. Miyata Y. Masubuchi K. Koyama C. U. Pittman 《应用聚合物科学杂志》2005,96(3):706-713
Polystyrene (PS) blends with rigid ladderlike polyphenylsilsesquioxane (PPSQ) were prepared by solution casting followed by hot pressing. The rheological properties of these blends were studied under dynamic shear and uniaxial elongation conditions. The loss modulus (G″) and dynamic shear viscosity (η*) of the 95/5 PP/PPSQ blend were slightly lower than those of pure PS at low frequencies (≤10?2 rad/s). However, the storage modulus (G′), G″, and η* of the other blends (90/10, 85/15, and 80/20) were higher than those of pure PS and increased with PPSQ content. The ηE data demonstrated that PS/PPSQ blends exhibited slightly weaker (5% PPSQ) or much weaker (10% PPSQ) strain hardening than PS. In contrast, the 85/15 and 80/20 PP/PPSQ blends showed strain softening, and the extent of strain softening increased with PPSQ content. PS entanglements might have been reduced by the specific interactions between PS and PPSQ, which locally ordered some PS molecules in the 95/5 blend sample, because most of the PPSQ might have been well dispersed in the PS continuous phase, and only a few small PPSQ particles (~1.3 μm) were formed because of good miscibility. However, at high PPSQ contents (≥10%), many larger hard PPSQ particles were formed, which acted as fillers during the rheological measurements. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 706–713, 2005 相似文献
66.
Grigory V. Merkin Lars Helge Stien Karin Pittman Ragnar Nortvedt 《Journal of food science》2014,79(6):E1137-E1141
Commercially collected records of Atlantic salmon (Salmo salar L.) muscle texture hardness were used to evaluate the effect of slaughter procedures and seasonality on texture quality. A database collected by Marine Harvest® contained flesh hardness records of Atlantic salmon slaughtered at processing plants in Norway from summer 2010 to summer 2011. The fish were slaughtered either by (1) percussion followed by automated bleeding (“Percussive”) or (2) live chilling with exposure to carbon dioxide (CO2) followed by manual severing gill arches and bleeding (“CO2”) or (3) live chilling with exposure to CO2 followed by percussive stunning and at the end automated bleeding (“CO2·percussive”). Hardness in salmon muscle cutlets was measured in Newtons (N) by Materials Testing Machine Zwick 500N. The hardness in salmon varied significantly over the study period (P < 0.05, mixed effect model) and showed the softest value of 21.2 (± 0.7) Newton (N) in summer 2011 and hardest 24.1 (± 0.2) N in autumn 2010. Slaughter procedures had a significant effect on salmon muscle hardness (P < 0.05, mixed effect model), where percussion followed by automated bleeding resulted in the hardest value (24.0 ± 0.4 N) as compared with CO2 stunning (21.8 ± 0.2 N) and combination of CO2 and percussive stunning (23.1 ± 0.15 N). CO2 is suspected as a causal factor in accelerated postmortem softening of the salmon muscle. 相似文献
67.
68.
Photoluminescence (PL) spectroscopy was used to monitor the efficiency of vanadium doping from a solid vanadium nitride source
during CVD growth of 4H silicon carbide. More than an order of magnitude increase of vanadium related infrared photoluminescence
in comparison to undoped samples was observed. By correcting the spectra for the contribution from the substrate, vanadium
was shown to be incorporated in the epitaxial layer during CVD and was responsible for the observed differences in photoluminescence
signal. Possible mechanisms of the vanadium transport to the growing layer and its incorporation are discussed. 相似文献
69.
Yongcheng Zhang Hossein Toghiani Jilei Zhang Yibin Xue Charles U. Pittman 《Journal of Materials Science》2009,44(8):2143-2151
Wood flour (WF)/polypropylene (PP) composites have been made by extrusion and hot press compression molding. The composite
water uptake and flexural properties were investigated. The composite fracture surfaces were studied by SEM. WF esterified
with octanoyl chloride was used in WF/PP composites to improve the composites’ water resistance. Maleated polypropylene (MAPP)
was also studied and compared with esterification by acid chlorides. Esterification by octanoyl chloride reduced the composite
water uptake. However, the C8 chain is still not long enough to form effective entanglements with the PP matrix. So, despite enhancements in hydrophobic
interactions, flexural strengths and flexural moduli decreased. MAPP (MW = 47000) polymer chains can entangle with the matrix
polypropylene molecules. Therefore, when MAPP’s maleic anhydride functions esterify WF surface hydroxyls, improved water resistance
and composite flexural properties were achieved. The modifier chain length is of critical importance and more important than
the surface density of hydrophobic groups for improving WF–PP interfacial adhesion and composite mechanical performance. 相似文献
70.
D. Ros K. Cassou B. Cros S. Daboussi J. DemaillyO. Guilbaud S. Kazamias J.-C. Lagron G. MaynardO. Neveu M. Pittman B. Zielbauer D. Zimmer T. KuhlS. Lacombe E. PorcelM.-A. du Penhoat P. ZeitounG. Mourou 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,653(1):76-79
LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam, which could also be used to produce synchronized XUV sources. In this contribution, the main results concerning both the development of XUV sources and their use for applications (irradiation of DNA samples) are presented, as well the present status and some perspectives for LASERIX. 相似文献