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21.
Gupta Surbhi; Pandit Shashi Bhushan; Srinivasan Narayanaswamy; Chatterji Dipankar 《Protein engineering, design & selection : PEDS》2002,15(6):503-511
Mycobacterium tuberculosis is a globally successful pathogen,infecting more than one third of total world's population. Thesebacteria have the remarkable ability to persist in the hostfor long periods of time unrecognized by the immune system andthen to re-emerge later in life causing the disease. The physiologyof such persistent or dormant bacilli is not very well characterized.Some evidence suggests that the dormant bacilli survive in anutrient-deprived state that is similar to the stationary phaseof the bacteria with respect to gene expression and physiology.Under this assumption we have studied the survival of Mycobacteriumsmegmatis in carbon starvation conditions as a model for mycobacterialpersistence. M.smegmatis, being a fast-growing strain, servesas a good model to study starvation responses. Using the two-dimensionalelectrophoresis-based proteomics approach, we identified a proteinwhich was found to be expressed preferentially under starvationconditions. This protein is homologous to a family of proteinscalled Dps (DNA binding Protein from Starved cells) that areknown to protect DNA under various kinds of environmental stressesand its existence has, so far, not been reported in mycobacteria.Upon expression and purification of this protein, we observedthat it has non-specific DNA-binding ability. Formation of acage-like dodecamer structure is a characteristic feature ofDps. Using comparative modelling we were able to show that Dpsfrom M.smegmatis could form a dodecamer structure similar tothe crystal structure of Dps from Escherichia coli. 相似文献
22.
Tongchai Sriwiriyarat Clifford W. Randall Dipankar Sen 《Canadian Metallurgical Quarterly》2005,131(11):1540-1549
The Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment systems are activated sludge biological nutrient removal processes that have been enhanced by the addition of biofilm support media into the aerobic zone of the system to obtain year round nitrification in activated sludge systems that otherwise could not support it. The objective of this study was to develop a computer package called “IFAS” that allows steady-state simulation of IFAS wastewater treatment processes based on the International Association Water Quality general model for activated sludge and empirical equations for chemical oxygen demand (COD) uptake and nitrification on integrated fixed film developed at Virginia Tech. The current version of the IFAS program supports only sponge-type media; however, the model could be modified for other media if the appropriate equations and required parameters values are known. Data obtained from IFAS sponge media pilot scale plants treating a weak municipal wastewater supplemented by sodium acetate, urea, sodium bicarbonate, and potassium phosphates and operated at different aerobic mean cells residence times were used to evaluate the model with parameter values for nitrification and COD uptake rates developed in batch studies. The model-generated ammonia and soluble COD profiles were insignificantly different statistically from the experimental data. The IFAS model satisfactorily predicts carbonaceous removal and nitrification, and has the potential to be a useful tool for scientists and engineers seeking to design and optimize either IFAS or conventional biological nutrient removal activated sludge systems. 相似文献
23.
Moutusi Banerjee Abhisek Gupta Shyamal K. Saha Dipankar Chakravorty 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(28):3451-3457
Attachment of Li+ ion on graphene surface to realize Li+‐ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1‐aza‐15‐crown‐5, the cage‐like structure containing four oxygens that can bind Li+ ion through electrostatic interaction. Li+ migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye‐type relaxation behavior with β (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li+ migration arising due to cation‐π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li+‐ion battery. 相似文献
24.
AbstractIn refrigeration and air conditioning systems, the fin surface may become dry, fully wet or partially wet depending upon the psychometric, thermo-physical and geometric parameters. The current work is intended to determine the length of the dry portion, temperature distribution, performance and optimum design parameters of a T-shaped fin under partially wet condition. Temperature dependent thermal conductivity of the fin material is taken and the humidity ratio of saturated air is considered to vary linearly with the corresponding fin surface temperature. Considering these the governing equation of T-shaped fin becomes nonlinear and it has been solved analytically by using Homotopy Perturbation Method. The point of separation between the dry and wet portions of a T-shaped fin may be located either in the stem or flange part and hence, two cases having different governing equations and boundary conditions are analyzed in the current study. For the optimization study, Lagrange multiplier technique is employed and the results are obtained by maximizing the heat transfer rate for a constant fin volume. Further, a comparative study is presented between insulated and convective fin tip conditions. 相似文献
25.
Dipankar Saha 《Materials Research Bulletin》2011,46(8):1252-1256
The facile method of solution combustion was used to synthesize γ(L)-Bi2MoO6. The material was crystallized in a purely crystalline orthorhombic phase with sizes varying from 300 to 500 nm. Because the band gap was 2.51 eV, the degradation of wide variety of cationic and anionic dyes was investigated under solar radiation. Despite the low surface area (<1 m2/g) of the synthesized material, γ(L)-Bi2MoO6 showed high photocatalytic activity under solar radiation due to its electronic and morphological properties. 相似文献
26.
Dipankar Chatterjee Suman Chakraborty 《Metallurgical and Materials Transactions B》2005,36(6):743-754
The turbulent flow inside a laser-generated molten pool is investigated by an adapted large-eddy simulation (LES) model that
incorporates physical considerations pertaining to the solid-liquid phase change. A single-domain, fixed-grid enthalpy-porosity
approach is utilized to model the phase-change phenomena in the presence of a continuously evolving solid/liquid interface.
The governing transport equations are simultaneously solved by employing a control-volume formulation, in conjunction with
an appropriate enthalpy-updating closure scheme. To demonstrate the performance of the present model in the context of phase-change
materials processing, simulation of a typical high-power laser melting process is carried out, where effects of turbulent
transport can actually be realized. It is found that the present LES-based model is more successful in capturing the experimental
trends, in comparison to the k-ε-based turbulence models often employed to solve similar problems in contemporary research investigations. 相似文献
27.
Zoran Miljanic Ivan Seskar Khanh Le Dipankar Raychaudhuri 《Mobile Networks and Applications》2008,13(5):533-541
This paper presents the design goals and architecture of WiNC2R—the WINLAB Network Centric Cognitive radio hardware platform.
The platform has been designed for flexible processing at both the radio physical layer and MAC/network layers with sustained
bit-rates of ~10 Mbps and higher. The hardware prototype supports multi band operation with fast spectrum scanning, the ability
to dynamically switch between a number of OFDM and DSSS modems and multiple MAC protocols. The radio modems, MAC, and network-layer
protocols are implemented in a flexible manner using general-purpose processing engines and a set of dynamically configurable
hardware accelerators. An FPGA based platform implementation currently in progress is described in terms of key hardware components
including the software-defined modem, the flexible MAC engine and network-level processor. Preliminary prototyping results
are reported, and a roadmap for further evolution of the WiNC2R board is provided. 相似文献
28.
Numerical simulations are performed to investigate the real gas effects on shock/expansion fan interaction. Initial perfect gas simulations at low enthalpy capture the flow structures efficiently and outcomes are found to have excellent agreement with the analytical calculations. Furthermore, the simulations with the real gas solver for different enthalpies showed that the variation in enthalpy significantly changes the flow structures. It is observed that an increase in enthalpy leads to a decrease and increase in the postshock and postexpansion fan Mach numbers, respectively. Another important observation is the decrement in the peak pressure ratio with an increment in the enthalpy. These effects are noted to be more pronounced for Mars's environment due to the higher dependency of specific heat on temperature. 相似文献
29.
Dr. Avisek Mahapa Gopal Ch Samanta Dr. Krishnagopal Maiti Prof. Dipankar Chatterji Prof. Narayanaswamy Jayaraman 《Chembiochem : a European journal of chemical biology》2019,20(15):1966-1976
Lipomannan and lipoarabinomannan are integral components of the mycobacterial cell wall. Earlier studies demonstrated that synthetic arabinan and arabinomannan glycolipids acted as inhibitors of mycobacterial growth, in addition to exhibiting inhibitory activities of mycobacterial biofilm. Herein, it is demonstrated that synthetic mannan glycolipids are better inhibitors of mycobacterial growth, whereas lipoarabinomannan has a higher inhibition efficiency to biofilm. Syntheses of mannan glycolipids with a graded number of mannan moieties and an arabinomannan glycolipid are conducted by chemical methods and subsequent mycobacterial growth and biofilm inhibition studies are conducted on Mycobacterium smegmatis. Growth inhibition of (73±3) % is observed with a mannose trisaccharide containing a glycolipid, whereas this glycolipid did not promote biofilm inhibition activity better than that of arabinomannan glycolipid. The antibiotic supplementation activities of glycolipids on growth and biofilm inhibitions are evaluated. Increases in growth and biofilm inhibitions are observed if the antibiotic is supplemented with glycolipids, which leads to a significant reduction of inhibition concentrations of the antibiotic. 相似文献
30.
Vianni Chopra Jijo Thomas Swati Kaushik Swati Rajput Rajdeep Guha Bidya Mondal Sudip Naskar Dipankar Mandal Gaurav Chauhan Naibedya Chattopadhyay Deepa Ghosh 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(14):2204637
Interest in the development of new generation injectable bone cements having appropriate mechanical properties, biodegradability, and bioactivity has been rekindled with the advent of nanoscience. Injectable bone cements made with calcium sulfate (CS) are of significant interest, owing to its compatibility and optimal self-setting property. Its rapid resorption rate, lack of bioactivity, and poor mechanical strength serve as a deterrent for its wide application. Herein, a significantly improved CS-based injectable bone cement (modified calcium sulfate termed as CSmod), reinforced with various concentrations (0–15%) of a conductive nanocomposite containing gold nanodots and nanohydroxyapatite decorated reduced graphene oxide (rGO) sheets (AuHp@rGO), and functionalized with vancomycin, is presented. The piezo-responsive cement exhibits favorable injectability and setting times, along with improved mechanical properties. The antimicrobial, osteoinductive, and osteoconductive properties of the CSmod cement are confirmed using appropriate in vitro studies. There is an upregulation of the paracrine signaling mediated crosstalk between mesenchymal stem cells and human umbilical vein endothelial cells seeded on these cements. The ability of CSmod to induce endothelial cell recruitment and augment bone regeneration is evidenced in relevant rat models. The results imply that the multipronged activity exhibited by the novel-CSmod cement would be beneficial for bone repair. 相似文献