全文获取类型
收费全文 | 3096篇 |
免费 | 112篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 93篇 |
综合类 | 39篇 |
化学工业 | 756篇 |
金属工艺 | 69篇 |
机械仪表 | 135篇 |
建筑科学 | 116篇 |
矿业工程 | 24篇 |
能源动力 | 93篇 |
轻工业 | 303篇 |
水利工程 | 25篇 |
石油天然气 | 10篇 |
武器工业 | 2篇 |
无线电 | 283篇 |
一般工业技术 | 436篇 |
冶金工业 | 294篇 |
原子能技术 | 44篇 |
自动化技术 | 525篇 |
出版年
2023年 | 12篇 |
2022年 | 39篇 |
2021年 | 63篇 |
2020年 | 29篇 |
2019年 | 55篇 |
2018年 | 66篇 |
2017年 | 47篇 |
2016年 | 59篇 |
2015年 | 63篇 |
2014年 | 84篇 |
2013年 | 172篇 |
2012年 | 141篇 |
2011年 | 214篇 |
2010年 | 202篇 |
2009年 | 209篇 |
2008年 | 218篇 |
2007年 | 186篇 |
2006年 | 143篇 |
2005年 | 166篇 |
2004年 | 97篇 |
2003年 | 104篇 |
2002年 | 104篇 |
2001年 | 65篇 |
2000年 | 59篇 |
1999年 | 43篇 |
1998年 | 68篇 |
1997年 | 55篇 |
1996年 | 46篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 47篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 18篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 24篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1973年 | 7篇 |
1971年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有3247条查询结果,搜索用时 593 毫秒
41.
42.
The use and impacts of accelerated weathering of limestone (AWL; reaction: CO2+H2O+CaCO3→Ca2++2(HCO3−) is explored as a CO2 capture and sequestration method. It is shown that significant limestone resources are relatively close to a majority of CO2-emitting power plants along the coastal US, a favored siting location for AWL. Waste fines, representing more than 20% of current US crushed limestone production (>109 tonnes/yr), could provide an inexpensive or free source of AWL carbonate. With limestone transportation then as the dominant cost variable, CO2 mitigation costs of $3-$4/tonne appear to be possible in certain locations. Perhaps 10–20% of US point–source CO2 emissions could be mitigated in this fashion. It is experimentally shown that CO2 sequestration rates of 10−6 to 10−5 moles/sec per m2 of limestone surface area are achievable, with reaction densities on the order of 10−2 tonnes CO2 m−3day−1, highly dependent on limestone particle size, solution turbulence and flow, and CO2 concentration. Modeling shows that AWL would allow carbon storage in the ocean with significantly reduced impacts to seawater pH relative to direct CO2 disposal into the atmosphere or sea. The addition of AWL-derived alkalinity to the ocean may itself be beneficial for marine biota. 相似文献
43.
44.
Ken Naitoh 《Artificial Life and Robotics》2012,17(2):275-286
The inevitability of various particle masses for hadrons, quarks, leptons, atoms, biological molecules, liquid droplets of fossil fuel and water, living cells including microorganisms and cancers, multi-cellar systems such as organs, neural systems, and the brain, stars, galaxies, and the cosmos is synthetically revealed. This is possible because each flexible particle is commonly generated by a mode in which a larger particle breaks up into two smaller ones through a gourd shape with two lumps. These masses, sizes, frequencies, and diversity dominated by super-magic numbers including the silver ratio, in fractal nature can be derived by the fusion of the quasi-stability principle defined between absolute instability and neutral stability, the indeterminacy principle extended for quantum, statistical, and continuum mechanics, and the spherical Lie group theory. The analyses also result in a new mathematical definition of living beings and non-living systems and further explain the standard network patterns of various particles and also the relation between information, structure, and function, because the proposed theory based on gourds posits a new hyper-interdisciplinary physics that explains a very wide range of scales, while the Newton, Schr?dinger, and Boltzmann equations describe only a narrow range of scales. 相似文献
45.
Yun Liu Mengxue Wang Yin Liang Chen Wang Keiji Naruse Ken Takahashi 《International journal of molecular sciences》2021,22(4)
A thrombus in a coronary artery causes ischemia, which eventually leads to myocardial infarction (MI) if not removed. However, removal generates reactive oxygen species (ROS), which causes ischemia–reperfusion (I/R) injury that damages the tissue and exacerbates the resulting MI. The mechanism of I/R injury is currently extensively understood. However, supplementation of exogenous antioxidants is ineffective against oxidative stress (OS). Enhancing the ability of endogenous antioxidants may be a more effective way to treat OS, and exosomes may play a role as targeted carriers. Exosomes are nanosized vesicles wrapped in biofilms which contain various complex RNAs and proteins. They are important intermediate carriers of intercellular communication and material exchange. In recent years, diagnosis and treatment with exosomes in cardiovascular diseases have gained considerable attention. Herein, we review the new findings of exosomes in the regulation of OS in coronary heart disease, discuss the possibility of exosomes as carriers for the targeted regulation of endogenous ROS generation, and compare the advantages of exosome therapy with those of stem-cell therapy. Finally, we explore several miRNAs found in exosomes against OS. 相似文献
46.
47.
Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion and hydrogen permeation characteristics of Zn-Ni-Cd alloy coatings electrodeposited from alkaline bath were studied and compared with those of Cd and Zn-Ni coatings obtained using commercial baths. Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion potential of this Zn-Ni-Cd coating was −0.62 V vs. SCE, which is still negative potential compared to iron. The corrosion rate of Zn-Ni-Cd coated steel was 0.073 mm y−1, which is estimated in a solution at a pH of 7. This value is much lower than the corrosion rate of Zn-Ni alloy (0.502 mm y−1) and Cd (0.306 mm y−1) coatings deposited from commercial baths. Zn-Ni-Cd alloys are also demonstrated to have superior hydrogen permeation inhibition properties compared to Cd and Zn-Ni coatings. Kinetic parameters of hydrogen permeation such as the transfer coefficient, α, the modified exchange current density, i0′, thickness dependent adsorption-absorption rate constant, k″, recombination rate constant, k3, surface hydrogen coverage, θs, were evaluated by applying a mathematical model to analyze experimental results. 相似文献
48.
Currently available information on droplet coalescence and break-up rates in turbulent flows in mixing vessels can be used to control drop sizes in dispersed phase equipment. The effect of drop size distributions on the selectivity and productivity in multi-reaction systems is examined in this paper.
The reaction system features the primary desired product (C) as resulting from reaction (in the bulk phase) between a reactant (A) in the drop phase and a second reactant (B) in the bulk phase. An adverse reaction is also envisaged which consumes (C) by further reaction with (B) to form a waste product. While small drops promote conversion because of large interfacial area, larger drops promote selectivity because of the facility of the product to re-enter the drop phase avoiding further reaction (to form waste) in the bulk phase. The effect of the bivariate distribution of drop size and reactant (A) concentration in the feed to a continuous stirred tank reactor on the selectivity and productivity of (C) is investigated within the framework of film theory while neglecting drop dynamics such as coalescence and break-up.
The results show the selectivity can be substantially improved by controlling drop size and distribution of the reactants among the differently sized droplets. Contrary to conventional wisdom which emphasizes creation of interfacial area by promoting very small droplets, it emerges that optimal distributions of drop size and reactant concentration which maximize productivity of the desired product exist. The practical implications are discussed. 相似文献
The reaction system features the primary desired product (C) as resulting from reaction (in the bulk phase) between a reactant (A) in the drop phase and a second reactant (B) in the bulk phase. An adverse reaction is also envisaged which consumes (C) by further reaction with (B) to form a waste product. While small drops promote conversion because of large interfacial area, larger drops promote selectivity because of the facility of the product to re-enter the drop phase avoiding further reaction (to form waste) in the bulk phase. The effect of the bivariate distribution of drop size and reactant (A) concentration in the feed to a continuous stirred tank reactor on the selectivity and productivity of (C) is investigated within the framework of film theory while neglecting drop dynamics such as coalescence and break-up.
The results show the selectivity can be substantially improved by controlling drop size and distribution of the reactants among the differently sized droplets. Contrary to conventional wisdom which emphasizes creation of interfacial area by promoting very small droplets, it emerges that optimal distributions of drop size and reactant concentration which maximize productivity of the desired product exist. The practical implications are discussed. 相似文献
49.
1H dipolar decoupled 13C n.m.r. experiments with the aid of the magic angle spinning technique have been used to determine the graft content and the isomer content of the polybutadiene grafts in a graft copolymer with isotactic polypropylene. 相似文献
50.
Traditional methods based on the product of exponentials (POE) formula are parametrically continuous and complete for the calibration of the kinematic parameters of serial robots. However, these methods are not minimal due to the constraints of joint twists. This paper puts forward a new POE-based model, whose parameters are totally independent and conform to the formula of minimality. This is the first model that simultaneously satisfies the requirements of parametric continuity, completeness, and minimality with uniform and generic modeling rules. The proposed approach avoids the operations of normalization and orthogonalization which are necessary redundancy elimination steps with the traditional model. Simulations on a SCARA robot and experiments on an ABB IRB 120 robot prove that the new model outperforms in convergence, accuracy, and efficiency. 相似文献