全文获取类型
收费全文 | 2084篇 |
免费 | 150篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 12篇 |
综合类 | 88篇 |
化学工业 | 89篇 |
金属工艺 | 50篇 |
机械仪表 | 81篇 |
建筑科学 | 64篇 |
矿业工程 | 15篇 |
能源动力 | 79篇 |
轻工业 | 1472篇 |
水利工程 | 2篇 |
石油天然气 | 13篇 |
武器工业 | 2篇 |
无线电 | 104篇 |
一般工业技术 | 71篇 |
冶金工业 | 30篇 |
原子能技术 | 6篇 |
自动化技术 | 64篇 |
出版年
2024年 | 17篇 |
2023年 | 36篇 |
2022年 | 58篇 |
2021年 | 63篇 |
2020年 | 82篇 |
2019年 | 78篇 |
2018年 | 69篇 |
2017年 | 71篇 |
2016年 | 63篇 |
2015年 | 84篇 |
2014年 | 125篇 |
2013年 | 136篇 |
2012年 | 103篇 |
2011年 | 131篇 |
2010年 | 99篇 |
2009年 | 80篇 |
2008年 | 86篇 |
2007年 | 104篇 |
2006年 | 108篇 |
2005年 | 106篇 |
2004年 | 74篇 |
2003年 | 70篇 |
2002年 | 67篇 |
2001年 | 38篇 |
2000年 | 40篇 |
1999年 | 44篇 |
1998年 | 37篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 10篇 |
1994年 | 25篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有2242条查询结果,搜索用时 15 毫秒
1.
2.
Zaidatul Akmal Othman Zaida Zakaria Joseph Bagi Suleiman Victor Udo Nna Aminah Che Romli Wan Syaheedah Wan Ghazali Mahaneem Mohamed 《International journal of molecular sciences》2021,22(8)
Obesity and hyperlipidemia are major risk factors for developing vascular diseases. Bee bread (BB) has been reported to exhibit some biological actions, including anti-obesity and anti-hyperlipidemic. This study aims to investigate whether bee bread can ameliorate vascular inflammation and impaired vasorelaxation activity through eNOS/NO/cGMP pathway in obese rats. Forty male Sprague-Dawley rats were randomly divided into four groups (n = 10/group), namely: control (normal group), obese rats (OB group), obese rats treated with bee bread (0.5 g/kg/day, OB/BB group) and obese rats treated with orlistat (10 mg/kg/day, OB/OR group). The latter three groups were given a high-fat diet (HFD) for 6 weeks to induced obesity before being administered with their respective treatments for another 6 weeks. After 12 weeks of the total experimental period, rats in the OB group demonstrated significantly higher Lee obesity index, lipid profile (total cholesterol, triglyceride, low-density lipoprotein), aortic proinflammatory markers (tumor necrosis factor-α, nuclear factor-κβ), aortic structural damage and impairment in vasorelaxation response to acetylcholine (ACh). Bee bread significantly ameliorated the obesity-induced vascular damage manifested by improvements in the lipid profile, aortic inflammatory markers, and the impaired vasorelaxation activity by significantly enhancing nitric oxide release, promoting endothelial nitric oxide synthase (eNOS) and cyclic guanosine monophosphate (cGMP) immunoexpression. These findings suggest that the administration of bee bread ameliorates the impaired vasorelaxation response to ACh by improving eNOS/NO/cGMP-signaling pathway in obese rats, suggesting its vascular therapeutic role. 相似文献
3.
荧光显示管直丝氧化物阴极有效逸出功的计算 总被引:1,自引:1,他引:0
阴极的逸出功是表征阴极发射能力的物理量,求定荧光显示管直丝氧化物阴极有效逸出功时,因其零场发射电流密度难于准确取值,温度无法直接测量,显得困难,须予解决,为此提出了一种计算阴极有产逸出功的办法,对某显示管的发射欠佳和“低温高效”的两种氧化物阴极的有效逸出功进行计算,有效逸出功率是靠测量相关物理量再同计算得出,精度不很高,文中所用办法也不例外,但所得结果能反映阴极发射能力,所需仪器少,是实用方法。 相似文献
4.
ABSTRACT: Grain of the soft white wheat cultivar Harus was harvested weekly from anthesis to maturity and fructooligosaccharides (FOS) contents were determined by reversed-phase high-performance liquid chromatography. Tests were carried out to determine the effect of adding immature wheat meal to a base flour of cultivar Russ (hard red spring) on the quality characteristics of bread. FOS content was also analyzed in baked bread, and the effect of transglutaminase in improving bread quality was examined. Marked decreases in FOS contents, such as 1-kestose and nystose, were observed with grain maturation. The overall quality of bread appeared to be acceptable, and the added FOS were retained after baking. 相似文献
5.
介绍了一种新型双族流平焰烧嘴的设计思路、结构参数及工业试验结果。其结构特点是每个部件都易装易卸,其煤气旋流器的位置可根据煤气压力变化进行调节,无需稳焰器就可保证煤气压力在较大范围波动时,都可形成稳定的平展火焰。 相似文献
6.
Effect of Flour Quality, Ascorbic Acid, and DATEM on Dough Rheological Parameters and Hearth Loaves Characteristics 总被引:1,自引:0,他引:1
ABSTRACT: The effects of protein quality, protein content, ascorbic acid, diacetyl tartaric acid ester of monoglyc-erides (DATEM), and their interactions on dough rheology and hearth bread properties were studied by size-exclusion fast protein liquid chromatography, Kieffer Dough & Gluten Extensibility Rig, and small-scale baking of hearth loaves. The effect of protein content was either positive or negative on hearth loaf characteristics, form ratio, and area, depending on the amount of the largest glutenin polymers in the flour. Ascorbic acid brought out the potential in the wheat flour known as protein quality. Ascorbic acid and DATEM strengthened the doughs and improved hearth bread characteristics. 相似文献
7.
A. A. Korobkin 《Journal of Engineering Mathematics》2007,58(1-4):121-139
The paper deals with the two-dimensional unsteady problem of the impact of a liquid parabola onto a rigid flat plate at a
constant velocity. The liquid is assumed ideal and incompressible and its flow potential. The initial stage of the impact
is the main concern in this study. The non-dimensional half-width of the contact region between the impacting liquid and the
plate plays the role of a small parameter in this problem. The flow region is subdivided into four parts: (i) the main flow
region, the dimension of which is of the order of the contact-region width, (ii) the jet-root region, where the curvature
of the free surface is very high and the flow is strongly nonlinear, (iii) the jet region, where the flow is approximately
one-dimensional, (iv) the far-field region, where the flow is approximately uniform at the initial stage of impact. A second-order
solution in the main flow region has been derived and matched to the first-order inner solution in the jet-root region. The
matching conditions provide an estimate of the dimension of the contact region for small time. Pressure distributions in both
the main flow region and the inner region are derived. The accuracy of the obtained asymptotic formulae is estimated. The
second-order hydrodynamic force acting on the plate is obtained and compared with available experimental data. A fairly good
agreement is reported. 相似文献
8.
金刚石光电导探测器研制及在软X光测量中的初步应用 总被引:1,自引:0,他引:1
介绍了我们自己设计制造的天然Ⅱa型金刚石光导探测器的结构,原理,制造工艺,实验标定及其在ICF实验中软X光测量中的应用等。 相似文献
9.
10.
Babur Ozcelik Mahmut Bayramoglu 《International Journal of Machine Tools and Manufacture》2006,46(12-13):1395-1402
Surface roughness is one of the most important requirements in machining process. The surface roughness value is a result of the tool wear. When tool wear increase, the surface roughness also increases. The determination of the sufficient cutting parameters is a very important process obtained by means of both minimum surface roughness values and long tool life. The statistical models were developed to predict the surface roughness.This paper presents the development of a statistical model for surface roughness estimation in a high-speed flat end milling process under wet cutting conditions, using machining variables such as spindle speed, feed rate, depth of cut, and step over. First- and second-order models were developed using experimental results of a rotatable central composite design, and assessed by means of various statistical tests. The highest coefficient of correlation (Radj2) (88%) was obtained with a 10-parameter second-order model. Meanwhile, a time trend was observed in residual values between model predictions and experimental data, reflecting the probable effect of the tool wear on surface roughness. Thus, in order to enhance the estimation capability of the model, another independent variable was included into the model to account for the effect of the tool wear, and the total operating time of the tool was selected as the most suitable variable for this purpose. By inserting this new variable as a linear term into the model, Radj2 was increased to 94% and a good fit was observed between the model predictions and supplementary experimental data.In this study, it was observed that, the order of significance of the main variables is as X5>X3>X4>X1>X2 (total machining time, depth of cut, step over, spindle speed and feed rate, respectively). 相似文献