全文获取类型
收费全文 | 1397篇 |
免费 | 55篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 11篇 |
综合类 | 5篇 |
化学工业 | 391篇 |
金属工艺 | 23篇 |
机械仪表 | 12篇 |
建筑科学 | 96篇 |
矿业工程 | 1篇 |
能源动力 | 29篇 |
轻工业 | 98篇 |
水利工程 | 3篇 |
无线电 | 120篇 |
一般工业技术 | 261篇 |
冶金工业 | 234篇 |
原子能技术 | 9篇 |
自动化技术 | 163篇 |
出版年
2022年 | 7篇 |
2021年 | 29篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 21篇 |
2014年 | 36篇 |
2013年 | 58篇 |
2012年 | 48篇 |
2011年 | 62篇 |
2010年 | 49篇 |
2009年 | 46篇 |
2008年 | 67篇 |
2007年 | 61篇 |
2006年 | 44篇 |
2005年 | 48篇 |
2004年 | 39篇 |
2003年 | 34篇 |
2002年 | 37篇 |
2001年 | 26篇 |
2000年 | 36篇 |
1999年 | 33篇 |
1998年 | 77篇 |
1997年 | 50篇 |
1996年 | 31篇 |
1995年 | 24篇 |
1994年 | 22篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 23篇 |
1975年 | 7篇 |
1974年 | 13篇 |
1973年 | 8篇 |
排序方式: 共有1456条查询结果,搜索用时 15 毫秒
1.
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
2.
3.
Separation tests using hollow-fibre modules were performed for the difficult selective extraction of trivalent actinides over fission lanthanides from acidic media. This article shows that with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine as the extractant, up to 94% americium could be extracted from 1.0 kmol/m3 HNO3, with minimal lanthanide co-extraction. Using a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid and tri-n-octyl phosphine oxide, tests were performed on extraction, lanthanide scrubbing and stripping. In the extraction test, up to 99.99% americium could be extracted from 0.5 kmol/m3 HNO3, with approximately one third of the lanthanides being co-extracted. Mass transfer calculations using a consistent set of input data showed good agreement with the experiments. 相似文献
4.
Summary Subject of this paper is the numerical investigation of the flow between impeller and casing of compressors of radial construction. The solution procedure is based on implicite difference equations, in which parameters of material such as heat conductivity, viscosity and density are variable. Because of the assumption of low density, laminar flow conditions are assumed. The computation method makes possible the determination of the torque coefficient as a function of Reynolds-and Mach number as well as of geometry and superposed throughflow.With 3 Figures 相似文献
5.
Under conditions typical of Harper-Dorn (H-D) creep the statistical slip-length may become comparable to, or even exceed,
the specimen diameter (a size effect). It is demonstrated that a consequence of such a size effect is that the rates of dislocation
storage and dynamic recovery are reduced and the static recovery rate will exceed the dynamic one. Under such conditions,
the analysis shows that the creep rate will scale linearly with the applied stress, a characteristic of H-D creep.
This article is based on a presentation made in the workshop entitled “Mechanisms of Elevated Temperature Plasticity and Fracture,”
which was held June 27–29, 2001, in San Diego, CA, concurrent with the 2001 Joint Applied Mechanics and Materials Summer Conference.
The workshop was sponsored by Basic Energy Sciences of the United States Department of Energy. 相似文献
6.
7.
Prostate cancer requires the attention of social workers in health care for three reasons: the growing elderly population which will increase the number diagnosed, the recent introduction of new treatments and the lack of social acceptability for this condition. Interventions for prostate cancer are specific to the stage of the disease. These individual, family and group interventions are a model for social work services to elderly men with other forms of cancer. Social workers have opportunity to research quality of life and decision-making issues to enhance medical practise in prostate cancer. 相似文献
8.
A simple model based on the Orowan equation and the dynamic evolution of the dislocation structure by generation and merging
of slipped areas is used to see which experimental results on creep of pure and solute-hardened crystalline materials can
or cannot be explained with regard to creep with refinement or coarsening of the dislocation structure and steady-state creep.
Quantitative deficiencies of the model for pure materials are discussed; most of them are related to neglection of subgrain
formation.
This article is based on a presentation made in the workshop entitled “Mechanisms of Elevated Temperature Plasticity and Fracture,”
which was held June 27–29, 2001, in San Diego, CA, concurrent with the 2001 Joint Applied Mechanics and Materials Summer Conference.
The workshop was sponsored by Basic Energy Sciences of the United States Department of Energy. 相似文献
9.
Study on the Role of Vitamin E as Nitrite Scavenger and N-Nitrosamine Inhibitor N-nitrosamine are known for their powerful carcinogenicity. They may be formed under acidic conditions by interaction of nitrosable amino substrates and nitrosating agents such as nitrite, nitrate and nitroso gases. Several of recent investigations demonstrate that certain micronutrients such as vitamin A, C, and E and trace elements selenium and zinc play an important role in cancer prevention. Because of their strong antioxidative, nitrite scavenging and free radical quenching properties, vitamin C and E are capable of inhibiting the peroxidation and nitrosation reaction. This paper summarizes the research work done up to date in the field of inhibition of N-nitrosamine formation by vitamin E. It also includes the latest results of our in vitro study on the inhibitory influence of vitamin E and a mixture of tocopherols as well as the cumulative effect of vitamin C and E on the formation of N-nitroso-N-methylaniline (NMNA). α-tocopherol and the mixture of tocopherols are capable of reducing nitrite concentration in hydrophilic reaction medium and thus inhibits the formation of N-nitrosamine. Both vitamins together have a stronger nitrite scavenger effect than either of them alone. The results of research work done up to date strongly suggest that both vitamins may play an important role in reducing the health hazard of some carcinogenic N-nitroso compounds. 相似文献
10.
The action mechanism for aggressive and highly pure media on fluoropolymer constructional elements is assumed to consist of two basic microeffects: destructive changes in the fluoropolymer and contamination of the environment. Our approach to a quantitative estimation of the physicochemical stability is based on logic similar to that of a thermodynamic model of a two‐component system. A fluoropolymer and changes in its microstructure are considered the first component of the system. The second component is composed of liquid media contaminated with fluoroorganic compounds extracted from the fluoropolymer. The proposed methods for delivering aggressive and highly pure fluids to consumers allow the exclusion of pollution from working areas with gaseous products through an exception to a number of intermediate stages of product transport. The discussed principles allow the creation of a modern, highly effective, and safe (with respect to the ecology and raw materials) production of aggressive liquid chemicals for consumers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 906–910, 2002 相似文献