全文获取类型
收费全文 | 445篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 74篇 |
金属工艺 | 5篇 |
机械仪表 | 34篇 |
建筑科学 | 14篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 24篇 |
水利工程 | 1篇 |
无线电 | 62篇 |
一般工业技术 | 98篇 |
冶金工业 | 50篇 |
原子能技术 | 12篇 |
自动化技术 | 64篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 33篇 |
2012年 | 13篇 |
2011年 | 20篇 |
2010年 | 13篇 |
2009年 | 21篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 3篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有462条查询结果,搜索用时 422 毫秒
101.
In general polymers are used in the form of composites (fiber reinforced, solid lubricated or both) in tribo-applications,
where they may encounter more than one type of wear situations or mechanisms to different extents. The area of investigating
the optimum concentration of fillers for best combination of tribo-performance in different wear modes and mechanical strength
is sparingly researched. In this paper, research findings on the influence of the contents of short carbon fibers (CF) and
PTFE (particulate form) in Polyamide (PA) 12 on friction and wear behavior in two wear modes (adhesive and fretting) have
been reported. With increase in contents of CF up to 30% (vol) most of the mechanical properties and tribo-performance improved
in adhesive and fretting wear modes. With a view to enhance it further, PTFE was added step by step in the best performing
composite (PA+30% CF). This boosted the tribo-performance further, however, at the cost of strength properties. With increase
in PTFE percentage (10, 15 and 20% by vol), specific wear rate (K
o) and friction coefficient (μ) both decreased appreciably in adhesive as well as fretting wear modes. The composite consisting of 30% CF and 20% PTFE showed
lowest values for μ and K
o rendering it the best tribo-combination for all practical purposes. The abrasive wear behavior of composites was also investigated.
However, wear performance in this mode showed exactly opposite trends. Inclusion of fibers or combination of fibers and PTFE
proved detrimental.
相似文献
J. BijweEmail: |
102.
I. Singh N. Bhatnagar 《The International Journal of Advanced Manufacturing Technology》2006,27(9-10):870-876
Drilling of fiber reinforced plastic (FRP) composite materials is a field open to a plethora of questions. Drilling-induced damage is a research area that has not been explored exhaustively. The present research endeavor is an effort to correlate drilling-induced damage with drilling parameters. Tool point geometry is considered a major factor that influences drilling-induced damage. Experiments were conducted and drilling-induced damage was quantified using the digital image processing technique. The results also reestablished the cutting speed to feed ratio as an important variable that influences drilling-induced damage. Mathematical models for thrust, torque, and damage are proposed that agree well with the experiments. 相似文献
103.
I. Singh N. Bhatnagar 《The International Journal of Advanced Manufacturing Technology》2006,27(9-10):877-882
Uni-directional glass fiber reinforced plastic (UD-FRP) composite materials are a feasible alternative to structural members that bear loads in only one direction. FRP composite materials have excellent properties in the direction of the fibers. Drilling- induced damage acts as an inhibitor to their application, as the holes act as stress concentration sites for failure under loading. The present study is an attempt to study the influence of drilling-induced damage on the residual tensile strength of uni-directional composite laminates and to propose a mathematical model correlating the residual strength with the drilling parameters. A finite element model (FEM) is also developed to study the drilling-induced damage in composite laminates. 相似文献
104.
Providing timely and cost-effective healthcare appears to be significantly desired. Factors such as computer skills and comprehension of instructions impact people’s perception of the accessibility of such alternatives, especially for medical professionals. There are limited studies examining the aforementioned factors in information systems (IS) literature in the context of medical teleconferencing (ehealth) from the patients’ perspective. Thus, the purpose of this research study was to examine the underlying structure of four factors, namely IS usage (ISU), computer self-efficacy (CSE), ethical severity of misusing IS (ESMIS), and the resistance to use IS (RESUIS). Based on data gathered from 140 participants, confirmatory factor analysis (CFA) was conducted, using the partial least squares (PLS) technique. Results indicated a very strong validity and reliability of the constructs, however, with a relatively low overall model predictability. Furthermore, the constructs of CSE and RESUIS appear to demonstrate significant contribution toward ISU. 相似文献
105.
ABSTRACT A number of parameters and an exhaustive material development and experimental procedure to determine the response variables like cutting forces, surface damage restricts the expensive experimental research. In this context, Finite Element Method (FEM) analysis can be used as a tool for the prediction of the various machining responses. A finite element analysis of the orthogonal machining of Uni-directional Glass Fiber Reinforced Plastic (UD-GFRP) laminates is presented in this study to understand the complex relation between fiber orientation, tool geometry, depth of cut on cutting forces and sub-surface damage. 相似文献
106.
Suman Labala Praveen Kumar Mandapalli Shubhmita Bhatnagar 《Drug development and industrial pharmacy》2015,41(8):1302-1310
Objective: The objective of this study is to prepare and characterize polymeric self-assembled layer-by-layer microcapsules (LbL-MC) to deliver a model protein, bovine serum albumin (BSA). The aim is to compare the BSA encapsulation in LbL-MC using co-precipitation and adsorption methods.Materials and methods: In co-precipitation method, BSA was co-precipitated with growing calcium carbonate particles to form a core template. Later, poly(styrene sulfonate) and poly(allylamine hydrochloride) were sequentially adsorbed onto the CaCO3 templates. In adsorption method, preformed LbL-MC were incubated with BSA and encapsulation efficiency is optimized for pH and salt concentration. Free and BSA-encapsulated LbL-MC were characterized using Zetasizer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and differential scanning calorimeter. Later, in vitro release studies were performed using dialysis membrane method at pH 4, 7.4 and 9.Results and discussion: Results from Zetasizer and SEM showed free LbL-MC with an average size and zeta-potential of 2.0?±?0.6?μm and 8.1?±?1.9?mV, respectively. Zeta-potential of BSA-loaded LbL-MC was (–)7.4?±?0.7?mV and (–)5.7?±?1.0?mV for co-precipitation and adsorption methods, respectively. In adsorption method, BSA encapsulation in LbL-MC was found to be greater at pH 6.0 and 0.2?M NaCl. Co-precipitation method provided four-fold greater encapsulation efficiency (%) of BSA in LbL-MC compared with adsorption method. At pH 4, the BSA release from LbL-MC was extended up to 120?h. Polyacrylamide gel electrophoresis showed that BSA encapsulated in LBL-MC through co-precipitation is stable toward trypsin treatment.Conclusion: In conclusion, co-precipitation method provided greater encapsulation of BSA in LbL-MC. Furthermore, LbL-MC can be developed as carriers for pH-controlled protein delivery. 相似文献
107.
Rohit R. Shahi Ashish Bhatnagar Sunita K. Pandey Viney Dixit O.N. Srivastava 《International Journal of Hydrogen Energy》2014
The present investigations are focused on the effect of different Ti-based catalysts (Ti, TiO2, TiCl3 and TiF3) on de/re-hydrogenation characteristics of nanocrystalline MgH2. Desorption temperature of milled MgH2 lowers from 380 to 350, 340, 310 and 260 °C with the addition of Ti, TiO2, TiCl3 and TiF3 respectively. The rehydrogenation characteristics are also improved through the deployment of Ti-based catalysts. Among all Ti based additives, TiF3 is found to be the most effective catalyst for hydrogen sorption from nano MgH2. The better catalytic effect of TiF3 over other Ti-based catalyst can be explained on the basis of temperature programmed reduction (TPR) studies. TPR experiments performed for different Ti additives, reveals that there is no oxidation/reduction reaction below 400 °C except for TiF3. The TPR profile of TiF3 shows some oxidation/reduction reaction exhibits at 200 °C. In order to further improve the sorption characteristics and cyclability of TiF3 catalyzed nano MgH2, we have investigated the effect of SWCNTs in MgH2+TiF3 sample. De/rehydrogenation characteristics reveal the synergistic effect of SWCNTs and TiF3 in MgH2+TiF3 sample. The details of the improvement in sorption behavior of MgH2–TiF3 in presence of SWCNTs are described and discussed. 相似文献
108.
Braj Gaurav Sharma Kushagra Khanna Neeraj Kumar Dhruv K. Nishad Mitra Basu Aseem Bhatnagar 《Drug development and industrial pharmacy》2017,43(11):1759-1769
Calcium chloride is an essential calcium channel agonist which plays an important role in the contraction of muscles by triggering calcium channel. First time hypothesized about its role in the treatment of GER (gastro-esophageal reflux) and vomiting disorder due to its local action. There are two objectives covered in this study as first, the development and optimization of floating formulation of calcium chloride and another objective was to evaluate optimized formulation through gamma scintigraphy in human subjects. Gastro retentive formulation of calcium chloride was prepared by direct compression method. Thirteen tablet formulations were designed with the help of sodium chloride, HPMC-K4M, and carbopol-934 along with effervescing agent sodium bicarbonate and citric acid. Formulation (F8) fitted best for Korsmeyer–Peppas equation with an R2 value of 0.993. The optimized formulation was radiolabelled with 99mTc-99?m pertechnetate for its evaluation by gamma scintigraphy. Gastric retention (6?h) was evaluated by gamma scintigraphy in healthy human subjects and efficacy of present formulation confirmed in GER positive human subjects. Gamma scintigraphy results indicated its usefulness in order to manage GERD. Stability studies of the developed formulation were carried out as per ICH guidelines for region IV and found out to be stable for 24?months. 相似文献
109.
Preeti Verma Poornendu Chaturvedi J. S. B. S. Rawat Manohar Kumar Surendra Pal Mahesh Bal D. S. Rawal Harsh Hanuman Prasad Vyas Partha Ghosal P. K. Bhatnagar 《Journal of Materials Science: Materials in Electronics》2007,18(6):677-680
Activation of abnormal emitting sites in Carbon Nano Tube (CNT) field emitters and their elimination is reported. CVD grown,
patterned CNT was used as cathode for field emission studies. We encountered the problem of current non-uniformity in CNT
cathode. This non-uniformity was attributed to abnormally active emitting sites during voltage ramp-up. The sudden increase
in current resulted in region of positive slope in F–N curve, which can’t be explained by conventional F–N theory. Also the
grown CNTs can be a mixture of metallic and semi conducting nature, which may cause deviation from the conventional F–N theory.
We could eliminate abnormally active sites by electric field treatment, thereby increasing current uniformity and stability.
The work is underway to understand the deviation in FN curve at high fields. 相似文献
110.
Biomass has been recognized as a major world renewable energy source to supplement declining fossil fuel sources of energy. Biomass derived transportation fuels have not only the potential to replace conventional fuels but can also be utilized as blending components for improving the quality of these fuels. The biocrude obtained from Euphorbia antisyphilitica, identified as the most potential petrocrop was investigated as a potential source for liquid fuels. The feed was studied for yield conversion data under different catalyst to feed ratio at various temperatures. Maximum middle distillates selectivity was observed at catalyst/oil ratio 4 and 6 and reaction temperature 500 °C. The main constituents of the gaseous products are C3, C4 and C5. The liquid fuels are highly aromatic with low olefinic content. 相似文献