全文获取类型
收费全文 | 1691篇 |
免费 | 91篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 29篇 |
综合类 | 6篇 |
化学工业 | 398篇 |
金属工艺 | 67篇 |
机械仪表 | 82篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 71篇 |
轻工业 | 189篇 |
水利工程 | 16篇 |
石油天然气 | 17篇 |
无线电 | 172篇 |
一般工业技术 | 338篇 |
冶金工业 | 135篇 |
原子能技术 | 15篇 |
自动化技术 | 191篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 83篇 |
2021年 | 114篇 |
2020年 | 78篇 |
2019年 | 77篇 |
2018年 | 89篇 |
2017年 | 77篇 |
2016年 | 61篇 |
2015年 | 50篇 |
2014年 | 76篇 |
2013年 | 130篇 |
2012年 | 81篇 |
2011年 | 101篇 |
2010年 | 83篇 |
2009年 | 66篇 |
2008年 | 67篇 |
2007年 | 67篇 |
2006年 | 49篇 |
2005年 | 46篇 |
2004年 | 45篇 |
2003年 | 28篇 |
2002年 | 17篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 37篇 |
1997年 | 23篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1786条查询结果,搜索用时 202 毫秒
101.
Andro Mondala Rafael Hernandez William Holmes Todd French Linda McFarland Darrell Sparks Monica Haque 《American Institute of Chemical Engineers》2013,59(11):4036-4044
The co‐fermentation of glucose and xylose by activated sludge microorganisms for the production of microbial oils for use as biodiesel feedstock was investigated. Various carbon sources at initial concentration of 60 g/L and C:N ratio 70:1 were investigated: xylose, glucose, and 2:1 and 1:2 (by mass) glucose/xylose mixtures. Oil accumulation ranged between 12 to 22% CDW, the highest of which was obtained when xylose was the sole substrate used. Kinetic modeling of the fermentation data showed that specific growth and oil accumulation rates were similar in all substrate types and the lipid coefficient ranged from 0.02 to 0.06 g/g of sugar consumed. The fatty acid methyl ester yield and composition of the lipids showed their suitability for conversion to biodiesel. Based on the results, lignocellulose sugars could be used as fermentation substrates by activated sludge microorganisms for enhancing the oil content of sewage sludge for its use as a sustainable biofuel feedstock source. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4036–4044, 2013 相似文献
102.
Roqia Ashraf Tariq Maqbool Mushtaq A. Beigh Arvind H. Jadhav Hasham S. Sofi Faheem A. Sheikh 《应用聚合物科学杂志》2021,138(25):50594
There is an extensive possibility of improving characteristics of fibers used in hard tissue engineering, being hydrophobic and less osteoconductive, resulting in the dynamic growth of new tissues. The current work focuses on the fabrication of nanofibers incorporated with titanium dioxide (TiO2) ''as osteoconductive'' and silver (Ag) ''as self-healing'' nanoparticles (NPs). The incorporation of AgNO3 by in situ method not only helped to impart the antibacterial activity but also changed the contact angle from 81 ± 03° in the case of pristine nanofibers to 74 ± 03°, 61 ± 03°, 50 ± 08°, and 39 ± 1.1°, in the composite scaffolds containing 0.01, 0.03, 0.05, and 0.07 M of Ag salts. The incubation in simulated body fluid at 37°C to induce mineralization on nanofiber scaffolds indicated Ca and P crystals' formation. The antibacterial activity showed significantly more toxicity toward E. coli (8.3 ± 0.9 mm) than S. aureus (1.2 ± 0.1 mm). Biocompatibility studies using MTT assay on the pre-osteoblasts showed that both TiO2 and Ag NPs present in the nanofibers are non-toxic to the bone-like cells. However, results show that a higher concentration of Ag NPs (i.e., 0.07 M) is toxic to cells growing. Finally, all the results suggest that the nanofiber scaffolds have considerable scope for future bone tissue engineering materials. 相似文献
103.
Shafqat Ali Khan Ghulam Dastagir Noor Ul Uza Akhtar Muhammad Rahim Ullah 《Microscopy research and technique》2020,83(6):636-646
The present study was conducted on characterization of morpho‐anatomical, phytochemical, and bio‐elemental analysis of root, stem, and leaf of Verbascum thapsus. Morphologically Verbascum is a biennial plant that flowers for a month and a half in mid‐ to late summer. Various organoleptic features of root, leaf, and stem were recorded. Anatomically the T. S of the root, stem, and leaf showed a typical dicot histological differentiation. Leaf possessed anomocytic stomata, crescent shape vascular bundles, and covered with long and stellate type trichomes while, stem contained collateral type of vascular bundles and a well‐developed pith to store phytochemicals responsible for various pharmacological activities. The powder drug study through scanning electron microscopy revealed the presence of various types of tissues. Branched, tree like and stellate trichomes in root and leaf help in absorption and reduce loss of water. These anatomical features are responsible for the survival of the plant as biennial. Four macro elements (Na, K, Ca, and Mg) and seven microelements (Cr, Cu, Fe, Mn, Ni, Zn, and Cd) and their concentrations in ppm were also studied using Atomic Absorption Spectroscopy. Phytochemical screening of methanolic extract showed existence of various secondary metabolites, while mucilage and anthraquinones was not detected. The present study helps to understand the taxonomic identification of the plant based on morpho‐anatomical features and throws the attention of the researchers to carry out the work for developing its various formulations, which can ultimately be beneficial for the human beings as well as animals. 相似文献
104.
I. S. Batraev E. S. Prokhorov V. Yu. Ul’yanitskii 《Combustion, Explosion, and Shock Waves》2014,50(3):315-322
The results of numerical modeling and experimental realization of the impact of a chemically reacting gas flow on powder particles during profiling (diameter increase while maintaining volume) of the barrel combustion chamber of a unit for detonation spraying are given. The passage from the combustion chamber into the barrel muzzle is made using connecting taper sleeves with a small narrowing angle. It is shown that such profiling can significantly reduce the barrel size without compromising the technological capabilities of the detonation unit. 相似文献
105.
The enhanced photocatalytic activity of Na0.9Mg0.45Ti3.55O8 co‐loaded with silver and platinum
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jing‐Zhou Wang Ze‐Qing Guo Jian‐Ping Zhou Yu‐Xi Lei Xuan‐Xuan Shi Qadeer Ul Hassan 《国际能源研究杂志》2018,42(3):1056-1065
Noble metals Ag and Pt were loaded on Na0.9Mg0.45Ti3.55O8 (NMTO) by chemical bath deposition method, which was synthesized firstly in our recent work. The scanning electron microscopy and transmission electron microscopy results show that Ag and Pt nanoparticles were distributed on the different surfaces of NMTO. NMTO loaded with Ag and Pt can efficiently enhance the separation of photogenerated electron‐hole pairs, exhibiting much higher photodegradative ability for methylene blue and rhodamine B than the pure NMTO. The best weight concentrations of Ag and Pt are 9.00% and 3.70%, respectively. The electrostatic field is built in the Schottky barrier between NMTO and noble metals, leading to the energy band bending. Then, photogenerated electrons and holes are efficiently separated to enhance the photocatalytic activity. 相似文献
106.
Isolation and identification of phosphate‐solubilizing microorganisms and distribution of orthophosphate in different seasons from sewage‐fed East Kolkata Wetland
下载免费PDF全文
![点击此处可从《Lakes & Reservoirs: Research and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Subinoy Mondal Smaranya Haque Debajyoti Kundu Deblina Dutta Apurba Ratan Ghosh 《Lakes & Reservoirs: Research and Management》2018,23(3):261-270
This study focused on isolation and identification of possible phosphate‐solubilizing bacteria (PSB ) from the sewage‐fed East Kolkata Wetland (EKWL ), a prospective water resource for pisciculture. In addition, different limnological parameters have been correlated with orthophosphate and seasonal variations. PSB have been isolated in Pikovskaya medium and identified morphologically and biochemically and finally analysed by 16S rDNA gene sequence. Limnological studies involving temperature (potentiometric), pH (potentiometric), dissolved oxygen (iodometric), ammonia‐nitrogen (spectrophotometric) and orthophosphate (spectrophotometric) concentrations were conducted. The results of this study established the presence of Bacillus megaterium , a potential PSB in EKWL . The activity of B. megaterium is also supported by the seasonal orthophosphate variations. The changes in concentration of other limnological parameters were also prominent. The water quality parameters of temperature (r = 0.886), dissolved oxygen (r = 0.729) and ammonia‐nitrogen (r = 0.396) concentrations exhibited a positive correlation with orthophosphate and a negative correlation with pH (r = ?0.699). The B. megaterium obtained in this study, exhibited a significant alteration in regard to orthophosphate content and relationships with other factors. Further experiment on the soluble phosphorus solubilization potential of B. megaterium revealed the biological availability of phosphorus was increased by threefold after 120 hr of incubation, with the decreasing pH value, although the phytase activity was 0.419 U/ml. PSB have a vital function in plant nutrition in supplying phosphate, essential nutrients and its uptake results in appropriate functioning and metabolism of different aquatic plants and organisms. PSB are competent biofertilizer to amplify aquaculture production for sustainable development. 相似文献
107.
108.
109.
Md Hossain Ali Ismail Abustan Md Ashiqur Rahman Abu Ahmed Mokammel Haque 《Water Resources Management》2012,26(3):623-641
Water is essential for economic, social, and environmental development. Global water resources are vulnerable due to increasing
demand related to population growth, pollution potential, and climate change. Competition for water between different sectors
is increasing. To meet the increasing demand, the use of groundwater is increasing worldwide. In this paper, the water-table
dynamics of the north-eastern region of Bangladesh were studied using the MEKESENS software. This study reveals that the depth
to water-table (WT) of almost all the wells is declining slowly. In many cases, the depth will approximately double by the
year 2040, and almost all will double by 2060, if the present trend continues. If the decline of the water-table is allowed
to continue in the long run, the result could be a serious threat to the ecology and to the sustainability of food production,
which is vital for the nation’s food security. Therefore, necessary measures should be taken to sustain water resources and
thereby agricultural production. Demand-side management of water and the development of alternative surface water sources
seem to be viable strategies for the area. These strategies could be employed to reduce pressure on groundwater and thus maintain
the sustainability of the resource. 相似文献
110.
M. Grujicic G. Arakere W. C. Bell H. Marvi H. V. Yalavarthy B. Pandurangan I. Haque G. M. Fadel 《Journal of Materials Engineering and Performance》2010,19(3):301-313
The effect of materials processing- and component manufacturing-induced uncertainties in material properties and component
shape and size on the reliability of component performance is investigated. Specifically, reliability of a suspension system
component from a high-mobility multipurpose wheeled vehicle which typically can fail under low-cycle strain-based fatigue
conditions is analyzed. Toward that end, the most advanced reliability-based design optimization methods available in the
literature were combined with the present understanding of low-cycle fatigue durability and applied to the component in question.
This entailed intricate integration of several computational tools such as multibody vehicle dynamics, finite-element simulations,
and fatigue strain-life assessment/prediction techniques. The results obtained clearly revealed the importance of consideration
of material property uncertainties in attaining vehicle performance of critical structural components in complex systems (e.g.,
a vehicle). 相似文献