全文获取类型
收费全文 | 3161篇 |
免费 | 112篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 56篇 |
综合类 | 17篇 |
化学工业 | 765篇 |
金属工艺 | 48篇 |
机械仪表 | 70篇 |
建筑科学 | 45篇 |
矿业工程 | 3篇 |
能源动力 | 142篇 |
轻工业 | 284篇 |
水利工程 | 19篇 |
石油天然气 | 15篇 |
无线电 | 322篇 |
一般工业技术 | 619篇 |
冶金工业 | 474篇 |
原子能技术 | 25篇 |
自动化技术 | 389篇 |
出版年
2023年 | 30篇 |
2022年 | 59篇 |
2021年 | 119篇 |
2020年 | 80篇 |
2019年 | 79篇 |
2018年 | 96篇 |
2017年 | 86篇 |
2016年 | 101篇 |
2015年 | 55篇 |
2014年 | 97篇 |
2013年 | 204篇 |
2012年 | 138篇 |
2011年 | 163篇 |
2010年 | 125篇 |
2009年 | 107篇 |
2008年 | 124篇 |
2007年 | 114篇 |
2006年 | 100篇 |
2005年 | 90篇 |
2004年 | 61篇 |
2003年 | 62篇 |
2002年 | 50篇 |
2001年 | 31篇 |
2000年 | 44篇 |
1999年 | 44篇 |
1998年 | 168篇 |
1997年 | 110篇 |
1996年 | 91篇 |
1995年 | 59篇 |
1994年 | 64篇 |
1993年 | 58篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 26篇 |
1984年 | 34篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 33篇 |
1975年 | 15篇 |
1974年 | 20篇 |
1972年 | 13篇 |
排序方式: 共有3293条查询结果,搜索用时 46 毫秒
111.
112.
3D Numerical study of temperature variation for subsonic rarefied gas flow in a microchannel is carried out using an in-house MPI-based parallelized DSMC code. The temperature drop in the microchannel decreases with an increase in the aspect ratio whereas it increases with an increase in the pressure ratio, the cross-aspect ratio (CAR), and the Knudsen number. 3D and 2D simulations results are compared and effect of the CAR and Knudsen number are brought out. Finally, a correlation that predicts the temperature drop is formulated along with a list of conditions that ensures a near isothermal flow. 相似文献
113.
Reena Shah 《Behaviour & Information Technology》2016,35(10):864-871
‘Selfie’, the Oxford Dictionary’s word of the year in 2013, has been gaining popularity as a global phenomenon and its usage is growing with technological advancements in front-facing cameras and photo-editing software. Earlier studies hold a lopsided view of either criticising selfies as ‘vain’ and ‘narcissist’ or appreciate them as ‘feel good’ for ‘positive identity formation’. The current study intends to take a fresh look at the act and explores reasons and motivators of young college students in India, as they take selfies and traces the usage pattern and its likely relationship with the motivators of selfie-taking. Qualitative data were gathered through a focused group discussion conducted among graduate students with an average of 23.5 years who volunteered to participate in the discussion. Results show that male and female students have varying reasons for taking selfies and it is often an act of fun and assertion of one’s right to ‘self-depiction’. Selfies have a life-cycle which ends after they receive reviews on the social media platform. Results from the study can aid policy-makers in India and theoretically add to the nascent field of literature in the area. 相似文献
114.
Shah Ghazanfar Ali Polette Arnaud Pernot Jean-Philippe Giannini Franca Monti Marina 《Engineering with Computers》2021,37(4):2891-2909
Engineering with Computers - This paper introduces a new fitting approach to allow an efficient part-by-part reconstruction or update of editable CAD models fitting the point cloud of a digitized... 相似文献
115.
Shipra Jain Jyoti Shah Nainjeet Singh Negi Chhemendra Sharma Ravinder Kumar Kotnala 《国际能源研究杂志》2019,43(9):4743-4755
Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm2 area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H3O+ ions diffuse through surface via proton hopping, while OH? ions migrate through interconnected defective crystallite boundaries resulting into high output cell current. 相似文献
116.
Rashid Jan Hassan Khan Poom Kumam Fairouz Tchier Rasool Shah Haifa Bin Jebreen 《计算机、材料和连续体(英文)》2021,68(3):3185-3201
It is eminent that partial differential equations are extensively meaningful in physics, mathematics and engineering. Natural phenomena are formulated with partial differential equations and are solved analytically or numerically to interrogate the system’s dynamical behavior. In the present research, mathematical modeling is extended and the modeling solutions Helmholtz equations are discussed in the fractional view of derivatives. First, the Helmholtz equations are presented in Caputo’s fractional derivative. Then Natural transformation, along with the decomposition method, is used to attain the series form solutions of the suggested problems. For justification of the proposed technique, it is applied to several numerical examples. The graphical representation of the solutions shows that the suggested technique is an accurate and effective technique with a high convergence rate than other methods. The less calculation and higher rate of convergence have confirmed the present technique’s reliability and applicability to solve partial differential equations and their systems in a fractional framework. 相似文献
117.
Dissociation of water molecule occurs on octahedrally coordinated unsaturated suface cations and oxygen vacancies created by lithium substitution in magnesium ferrite. Lower synthesis temperature of ferrite has generated nanopores in microstructure. Dissociated hydronium and hydroxyl ions are transported through surface and capillary diffusion in porous ferrite network towards attached Zn and Ag electrodes. Water molecule dissociation ability of nanoporous ferrite has been exploited to develop a green electrical energy cell, which is a combination of material science and electrode chemistry. The innovated cell has been nomenclatured as hydroelectric cell (HEC). When HEC is partially dipped in deionized water, spontaneously hydroxide and hydronium ions are produced by water molecule dissociation. Hydronium ions trapped in nanopores develop enough electric field that further dissociates physisorbed water molecules. Thereby, the process of water molecule dissociation is accelerated in a bigger way to increase ionic current in the cell. Oxidation of Zn electrode by hydroxide ion and reduction of H3O+ at Ag electrode develop voltage and electric current in the cell. The HEC cell of a 17 cm2 area is able to generate a short circuit current of 82 mA and 920 mV emf with a maximum output power of 74 mW, which is three order higher than reported output power 1.4 μW/cm2 produced by water in cement matrix. Hydroelectric cell performance is repetitive, stable and possesses potential to replace traditional ways of generating renewable energy in terms of cost and safety. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
118.
Bitumen extraction from oil sands is carried out in large separation cells using a water-based extraction process. Controlling
the Bitumen-froth and Middlings interface in these cells at an optimum level provides significant economical and environmental
benefits. Traditional sensors are not reliable in estimating this interface level and novel vision-based sensors have been
developed previously to overcome this problem. These sensors estimate the interface level and its confidence for separation
cells with a single sight glass. The confidence value only represents the turbidity of the interface and hence cannot be used
for control decision making in all process conditions. The current work describes an image differencing algorithm for interface
level detection which also facilitates the computation of a confidence estimate that is accurate in most process situations.
The confidence value is computed based on noise statistics, an appropriately chosen edge detection method and a change detection
algorithm. Another significant advantage of the algorithm is that both the interface level and the confidence estimation procedures
can be extended in a straight-forward manner to handle the presence of multiple sight glasses. Off-line results show that
the algorithm accurately detects the interface level in normal process conditions (with high confidence values) and outputs
correct confidence values in other situations with very low false-positive and false-negative error rates. On-line industrial
implementation results show that the vision sensor tracks the interface level very closely and results in significant automation
of plant. 相似文献
119.
Significant improvement for the functional properties of konjac glucomannan based on phase separation
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qing Huang Honghe Ge Weiping Jin Bakht R. Shah Shuxin Ye Ying Hu Bin Li Yijie Chen 《International Journal of Food Science & Technology》2016,51(11):2396-2405
Konjac glucomannan (KGM) serves as a stabiliser due to its high molecular weight and viscosity. However, these properties limit its addition in food products, especially in drinks. The main aim of this study was to improve the functional properties of KGM by a green and effective method, that is phase separation. It was found that increasing temperature accelerated phase separation of KGM/gum arabic mixture. KGM‐rich phase was characterised and its physical properties were investigated by different methods. Crystal property showed no significant changes after phase separation. Nevertheless, rheological properties indicated that the viscosities of samples after phase separation (FKGM) decreased dramatically. Their emulsifying capacities also improved. Moreover, the differences in molecular rearrangement at the oil–water interface were also studied by using interfacial rheology. These results suggested that FKGM with low viscosity had better interfacial properties, and thus may have potential applications as food ingredients. 相似文献
120.