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排序方式: 共有221条查询结果,搜索用时 15 毫秒
1.
We have investigated the reaction kinetics of a liquid prepolymer DGEBA with isophorone diamine (IPD) and menthane diamine (MNDA). IPD is 10 times more reactive than MNDA. With mixtures of these two hardeners we have the possibility to control the reactivity of the curing agent and the pot life of the system. The kinetic results can be described with a single conversion temperature-phase diagram and interpreted with the classical autocatalytic epoxyprimary and secondary amine hydrogens addition. The differences between IPD and MNDA can be explained by the steric hindrance around the amine group of MNDA and also by the difficulty to obtain pure MNDA without oxidation. 相似文献
2.
In this paper, we provide a necessary infrastructure to define an abstract state exploration in the HOL theorem prover. Our infrastructure is based on a deep embedding of the Multiway Decision Graphs (MDGs) theory in HOL. MDGs generalize Reduced Ordered Binary Decision Diagrams (ROBDDs) to represent and manipulate a subset of first-order logic formulae. The MDGs embedding is based on the logical formulation of an MDG as Directed Formulae (DF). Then, the MDGs operations are defined and the correctness pro... 相似文献
3.
Adnan Hasan Bdair Aighuraibawi Selvakumar Manickam Rosni Abdullah Zaid Abdi Alkareem Alyasseri Ayman Khallel Dilovan Asaad Zebari Hussam Mohammed Jasim Mazin Mohammed Abed Zainb Hussein Arif 《计算机系统科学与工程》2023,47(1):553-574
Internet Protocol version 6 (IPv6) is the latest version of IP that goal to host 3.4 × 1038 unique IP addresses of devices in the network. IPv6 has introduced new features like Neighbour Discovery Protocol (NDP) and Address Auto-configuration Scheme. IPv6 needed several protocols like the Address Auto-configuration Scheme and Internet Control Message Protocol (ICMPv6). IPv6 is vulnerable to numerous attacks like Denial of Service (DoS) and Distributed Denial of Service (DDoS) which is one of the most dangerous attacks executed through ICMPv6 messages that impose security and financial implications. Therefore, an Intrusion Detection System (IDS) is a monitoring system of the security of a network that detects suspicious activities and deals with a massive amount of data comprised of repetitive and inappropriate features which affect the detection rate. A feature selection (FS) technique helps to reduce the computation time and complexity by selecting the optimum subset of features. This paper proposes a method for detecting DDoS flooding attacks (FA) based on ICMPv6 messages using a Binary Flower Pollination Algorithm (BFPA-FA). The proposed method (BFPA-FA) employs FS technology with a support vector machine (SVM) to identify the most relevant, influential features. Moreover, The ICMPv6-DDoS dataset was used to demonstrate the effectiveness of the proposed method through different attack scenarios. The results show that the proposed method BFPA-FA achieved the best accuracy rate (97.96%) for the ICMPv6 DDoS detection with a reduced number of features (9) to half the total (19) features. The proven proposed method BFPA-FA is effective in the ICMPv6 DDoS attacks via IDS. 相似文献
4.
Bahaa M. Kamel M. El-Sherbiny K. A. Abed M. Abd-Rabou 《Fullerenes, Nanotubes and Carbon Nanostructures》2017,25(7):429-434
The effect of graphene nanosheets (GNS) on the rheological characteristics and thermal conductivity of calcium grease used in marine applications, and water pumps for lower demanding applications, has been experimentally evaluated in this paper. Various volume fractions of GNS (0.5, 1, 2, 3, and 4% wt.) have been immersed in the grease aiming at finding the better percentages that improve the properties of nanogrease. The rheological characteristics and thermal conductivity were evaluated with a Brookfield Rheometer DV-III ULTRA and KD2 thermal analyzer, respectively. The results of the modified calcium grease indicated that the best concentration of GNS is 3% wt. The rheological characteristics of the grease with a different volume fraction of GNS indicated a non-Newtonian behavior. Thermal conductivity of nanogreas also increases with an increase of GNS volume fraction. Moreover, the apparent viscosity, shear stress and dropping point increase by 59%, 52%, and 65%, respectively, with increasing GNS volume fraction. 相似文献
5.
Two modified electrodes (Pb/PbO2 and C/PbO2) were prepared by electrodepositing a lead oxide layer on lead and carbon sub-strates. These modified electrodes were used as anodes for the generation of sodium hypochlorite (NaOCl) from sodium chloride solution. Different operating conditions and factors affecting the treatment process of NaOCl generation, including current density, pH values, con-ductive electrolytes, and electrolysis time, were studied and optimized. By comparison the C/PbO2 electrode shows a higher efficiency than the Pb/PbO2 electrode for the generation of NaOCl. 相似文献
6.
George Z. Voyiadjis Farid H. Abed 《International journal for numerical methods in engineering》2006,67(7):933-959
An implicit objective stress update algorithm is proposed for a hypoelastic–viscoplastic model. A thermal/dynamic yield function, which is derived based on the thermal activation analysis and dislocation interaction mechanisms, is used, along with the Consistency approach and the framework of additive viscoplasticity, in deriving the proposed model for fcc metals. The corotational formulation approach is utilized in developing the proposed model in the finite deformation field. For the case of the Newton–Raphson iteration method, a new expression for the consistent (algorithmic) tangent stiffness matrix of rate‐dependent metals is derived by direct linearization of the stress update algorithm. Finite element simulations are performed by implementing the proposed viscoplasticity constitutive models in the commercial finite element program ABAQUS. Numerical implementation for a simple tensile problem is used for validating the material parameters of the OFHC Copper under low and high strain rates and temperatures. The numerical results of the adiabatic true stress–true strain curves compare very well with the experimental data. The effectiveness of the present approach is tested by studying strain localization in a simple plane strain problem. Results indicate excellent performance of the present framework in describing the strain localization problem and in obtaining mesh‐independent results. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
Grimandi G Soueidan A Anjrini AA Badran Z Pilet P Daculsi G Faucheux C Bouler JM Guicheux J 《Microscopy research and technique》2006,69(8):606-612
The increased generation and up-regulated activity of bone resorbing cells (osteoclasts) play a part in the impairment of bone remodeling in many bone diseases. Numerous drugs (bisphosphonates, calcitonin, selective estrogen receptor modulators) have been proposed to inhibit this increased osteoclastic activity. In this report, we describe a pit resorption assay quantified by scanning electron microscopy coupled with image analysis. Total rabbit bone cells with large numbers of osteoclasts were cultured on dentin slices. The whole surface of the dentin slice was scanned and both the number of resorption pits and the total resorbed surface area were measured. Resorption pits appeared at 48 h and increased gradually up to 96 h. Despite the observation of a strong correlation between the total resorption area and the number of pits, we suggest that area measurement is the most relevant marker for osteoclastic activity. Osteotropic factors stimulating or inhibiting osteoclastic activity were used to test the variations in resorption activity as measured with our method. This reproducible and sensitive quantitative method is a valuable tool for screening for osteoclastic inhibitors and, more generally, for investigating bone modulators. 相似文献
8.
In this paper we propose an automatic methodology to verify the soundness of model checking reduction techniques. The idea is to use the consistency of the specifications to verify if the reduced model is faithful to the original one. The user provides the reduction technique, the specification and the system under verification. Then, using Higher Order Logic he verifies automatically if the reduction technique is soundly applied. The method is completely defined in an MDG–HOL special integration platform that combines an automatic high level model checking tool Multiway Decision Graphs (MDGs) within the HOL theorem prover. We provide two case studies, the first one is the reduction using SAT–MDG of an Island Tunnel Controller and the second one is the MDG–HOL assume-guarantee reduction of the Look-Aside Interface. The obtained results of our approach offer a considerable gain in terms of the correctness of heuristics and reduction techniques as applied to commercial model checking, however a small penalty is paid in terms of CPU time and memory usage. 相似文献
9.
Bassam Jamil Mohd Sa’ed Abed Bassam Na’ami Thaier Hayajneh 《Signal, Image and Video Processing》2013,7(6):1029-1040
Security and imperceptibility are fundamental issues for steganography. This paper presents a multi-level steganography system based on concealing and deception. Basically, the secret image is embedded in a cover image, which in turn is embedded in another higher-level cover image. Each steganography level provides additional security, with lower levels implemented using stronger steganography methods. Furthermore, in the event that the higher level steganography is compromised, it would include misleading information to deceive the attacker that he/she is successfully eavesdropping. One challenge of hierarchical system is retaining hidden data in lower level in a higher level stenographic technique. To mitigate this issue, we designed a novel technique which combines discrete cosine transform and least significant bit (LSB). The technique objective is to maximize the capacity and invisibility of the secret image with minimal modification to the cover image (at most k-bits per block). The performance (capacity and peak signal-to-noise ratio) of the proposed method has superior performance compared with LSB since it combines the benefits of 1-bit and 3-bit LSBs. Furthermore, the paper demonstrates that the secret message is successfully embedded and extracted in two-level steganography system with peak signal-to-nose ratio greater than 20 dB. 相似文献
10.
Mouna Hamouda Insaf Handous Nasr Ben Dhia Samia Ayachi Ahmed Letaief Sabra Aloui Ammeur Frih Habib Skhiri Habib Khochtali Mezri Elmay 《Hemodialysis international. International Symposium on Home Hemodialysis》2012,16(4):497-503
Brown tumors (BTs) are relatively uncommon but they are serious complications of renal osteodystrophy. The objective of this study was to analyze the clinical, biological, and radiological characteristics of 16 patients with BTs provoked by secondary hyperparathyroidism (sHPT) and its response to the decrease in parathyroid hormone levels after parathyroidectomy (PTX). The management of that uncommon condition was also reviewed. We conducted a retrospective study including 16 end‐stage renal disease patients who underwent subtotal PTX between 1997 and 2007 for severe sHPT with BTs. Our study included 10 men and 6 women, whose average age was 34 years. All patients were on dialysis. Ten of them were on dialysis for more than 5 years. The median duration on dialysis was 84 months. Patients included suffered from swellings associated with functional limitations. BTs had multiple locations in 7 patients. Jaw was the most frequent location (62%). Radiography and tomodensitometry demonstrated a mixed radio lucent and radio‐opaque lesions with an expansion of the cortical bone. Bone scan demonstrated an increased uptake of lesions. Chirurgical treatment was indicated in all cases because of severe refractory sHPT with functional limitations and/or disfiguring deformities. In all cases, BTs stopped its progression and even decreased in size. However, it was insufficient in four cases, which required a surgical resection. PTX remains an efficacious approach in resistant cases of sHPT with persistent BTs. 相似文献