全文获取类型
收费全文 | 397篇 |
免费 | 35篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 66篇 |
金属工艺 | 15篇 |
机械仪表 | 16篇 |
建筑科学 | 3篇 |
能源动力 | 19篇 |
轻工业 | 49篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 54篇 |
一般工业技术 | 89篇 |
冶金工业 | 8篇 |
原子能技术 | 3篇 |
自动化技术 | 104篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 19篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 38篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 37篇 |
2012年 | 15篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 26篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1970年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有432条查询结果,搜索用时 15 毫秒
81.
Harish K. Patney Christina Nordlund Adam Moy Harry Rose Brent Young Michael A. Wilson 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(6):941-971
Abstract Graphite has normally been used to synthesise fullerenes and nanotubes. However, coal is a cheaper and more suitable industrial material. Because coal is a molecular solid, unlike graphite, the mechanism by which fullerene and nanotubes are formed is different. Moreover, other products such as polyaromatic hydrocarbons (PAHs) and microfibres are also formed. In this review, the mechanism of formation of fullerene and nanotubes from coal is discussed. It is shown that the pathway involved is other than through the C1 intermediate route. The influence of other elements in coal such as hydrogen, oxygen, sulfur and iron is also discussed. It appears that, hydrogen, oxygen, iron and sulfur affect the yield and type of fullerenes and nanotubes formed. 相似文献
82.
Naif H. Alsharif Said A. Farha Al‐Said Mark A. Birch Benjamin R. Horrocks Harish K. Datta 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(21):3685-3692
The lack of an in vitro real‐time osteoclast (OC) activity assay has hampered mechanistic studies of bone resorption. Such an assay is developed, employing a hydroxyapatite matrix impregnated with alkyl‐capped silicon nanocrystals, which is capable of monitoring the time‐course of resorption by single osteoclasts. Resorption of the matrix by OC releases the nanocrystals, which are internalized by the cell and detected as an increase in OC luminescence. This particular choice of nanocrystals is motivated by their bright pH‐independent luminescence, proportional to concentration, and by their rapid uptake without cytotoxicity. In this in vitro assay, OCs are inhibited by calcitonin (CT) and methyl‐β‐cyclodextrin (MCD), and stimulated by receptor activator of nuclear factor kappa‐B ligand (RANKL) in the expected manner. The kinetics of the assay exhibit a lag phase representing cell attachment and commencement of resorption processes, followed by a growth of cell luminescence intensity, and the whole time‐course is satisfactorily described by the logistic equation. 相似文献
83.
Niraj Chawake Sri Harish Kumar Paleti B. S. Murty Ravi S. Kottada 《Transactions of the Indian Institute of Metals》2013,66(4):419-424
In the present work, nanocrystalline FeAl and FeAl–Al2O3 composite were synthesized by high energy ball milling and subsequent compaction by spark plasma sintering. Microstructural changes during all stages of processing are studied using X-ray analysis. After 20 h of milling, the disordered FeAl and some amount of Fe rich solid solution was obtained in both of these compositions. Subsequent heat treatment results in formation of ordered FeAl. However, disordering of FeAl was observed in both compositions after spark plasma sintering. Nanocrystallinity is retained in both the compositions even after sintering at high temperature of 1,000 °C. Very high hardness of ~575 HV1 and ~600 HV1 was exhibited by FeAl and FeAl–Al2O3 composite. 相似文献
84.
Traditionally, reliability based design optimization (RBDO) is formulated as a nested optimization problem. For these problems the objective is to minimize a cost function while satisfying the reliability constraints. The reliability constraints are usually formulated as constraints on the probability of failure corresponding to each of the failure modes or a single constraint on the system probability of failure. The probability of failure is usually estimated by performing a reliability analysis. The difficulty in evaluating reliability constraints comes from the fact that modern reliability analysis methods are themselves formulated as an optimization problem. Solving such nested optimization problems is extremely expensive for large scale multidisciplinary systems which are likewise computationally intensive. In this research, a framework for performing reliability based multidisciplinary design optimization using approximations is developed. Response surface approximations (RSA) of the limit state functions are used to estimate the probability of failure. An outer loop is incorporated to ensure that the approximate RBDO converges to the actual most probable point of failure. The framework is compared with the exact RBDO procedure. In the proposed methodology, RSAs are employed to significantly reduce the computational expense associated with traditional RBDO. The proposed approach is implemented in application to multidisciplinary test problems, and the computational savings and benefits are discussed. 相似文献
85.
Harish Agarwal Shawn E. Gano Victor M. Pérez Chandan K. Mozumder Layne T. Watson 《工程优选》2013,45(6):593-607
In reliability based design optimization, a methodology for finding optimized designs characterized with a low probability of failure the main objective is to minimize a merit function while satisfying the reliability constraints. Traditionally, these have been formulated as a double-loop (nested) optimization problem, which is computationally intensive. A new efficient unilevel formulation for reliability based design optimization was developed by the authors in earlier studies, where the lower-level optimization was replaced by its corresponding first-order Karush–Kuhn–Tucker (KKT) necessary optimality conditions at the upper-level optimization and imposed as equality constraints. But as most commercial optimizers are usually numerically unreliable when applied to problems accompanied by many equality constraints, an optimization framework for reliability based design using the unilevel formulation is developed here. Homotopy methods are used for constraint relaxation and to obtain a relaxed feasible design and heuristic scheme is employed to update the homotopy parameter. 相似文献
86.
87.
In a rotor bearing system operating with constant angular acceleration, after passing through the critical speed, typical beat characteristics are observed because the transverse vibration response contains both excited and natural motion, and shortly after passing resonance, vibrations with close frequencies appear. The present study explains a method for estimating damping of rotor bearing systems from transient beat vibration signals observed during run up stage. A mathematical derivation to prove that a part of run-up vibration of the rotor system consists of beat phenomenon when the system crosses critical speed. It is also observed from the mathematical model that the beat vibrations depend on the damping in the system. This beat response is considered for Hilbert analysis and the damping is estimated. Increase in angular acceleration of the rotor will increase the damping. This paper investigates how the damping varies with respect to different angular acceleration values of the rotor bearing system. Experimental validation of the beat phenomenon and damping estimation are done for the rotor system. The proposed method is validated by using half-power band width method applied to run-up response. 相似文献
88.
Antioxidant activity and hepatoprotective potential of Phyllanthus niruri, a widely used medicinal plant, were investigated. Methanolic and aqueous extract of leaves and fruits of P. niruri showed inhibition of membrane lipid peroxidation (LPO), scavenging of 1,1-diphenyl-2picrylhydrazyl (DPPH) radical and inhibition of reactive oxygen species (ROS) in vitro. Antioxidant activity of the extracts were also demonstrable in vivo by the inhibition of the carbon tetrachloride (CCl4) – induced formation of lipid peroxides in the liver of rats by pretreatment with the extracts. CCl4 – induced hepatotoxicity in rats, as judged by the raised serum enzymes, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT), was prevented by pretreatment with the extracts, demonstrating the hepatoprotective action of P. niruri. 相似文献
89.
S. Omar S. Mandal A. Ashok A.R. Harish M. Katiyar 《Microelectronics Reliability》2011,51(12):2173-2178
This paper reports the analysis of key parameters affecting voltage transfer characteristics of pseudo PMOS organic inverters. Pentacene has been used as active material for PMOS Organic Thin Film transistor (OTFT). We have used two different inverter configurations for thorough analysis. Each configuration comprises of an enhancement mode driver (VThreshold = −9.7 V) and a depletion mode load (VThreshold = 11.7 V). First configuration has its source and gate terminals shorted. While, second configuration differs with its drain and gate terminals shorted. In order to surmise the theoretical performance of the inverters, we have used load matching technique. After investigating various parameters such as inverting gain, noise margin values (immunity to noise error signals) and threshold voltage value, influencing the voltage inverting efficiency of the two configurations mentioned above, it was found that an inverter with shorted source-gate load configuration is better of the two due to privileges such as saturation mode operation of load, low driver current with early saturation of enhancement mode driver, which facilitates full swing output voltage operation. Second configuration with shorted drain-gate load, lacks saturation mode operation of load and fails to deliver high voltage swing along with acceptable noise margin values and inverting gain. 相似文献
90.
Prof. Dr. Sakuntala Chatterjee Dr. Ramanna Harish Prof. Dr. Gunter M. Schütz 《化学,工程师,技术》2013,85(11):1671-1679
In the past, the investigation of catalytic reactivity enhancement through molecular traffic control (MTC) by means of dynamical Monte Carlo simulations of catalysis was initiated in simple, idealized zeolite channel networks. These results are reviewed here and, emphasizing more recent work, the conditions of reactivity enhancement through MTC are examined for a realistic channel topology based on the pore structure of the zeolite TNU‐9. For a wide range of reaction rates a very strong MTC effect can be found that increases with grain size. This effect is argued to be a generic feature of a certain class of zeolite pore topologies. 相似文献