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排序方式: 共有264条查询结果,搜索用时 15 毫秒
81.
Tuan Doan Khang Nguyen Phong Dam Nga Pham Quan Vu Thanh Huyen Vuong Thanh Huyen Pham Minh Thang Le 《化学工程与技术》2020,43(4):731-741
SAPO-34 is a crystalline microporous material, the characteristics of which are greatly influenced by synthetic parameters, especially the silica precursors and templates. In this study, the combination of templates and silica sources was optimized to obtain SAPO-34 phases in the purest form. The physicochemical properties of the thus-synthesized catalysts were characterized, and the Si environment in the SAPO-34 framework was analyzed. The catalytic performance in biomass gasification was investigated in a fixed-bed flow reactor. SAPO-34 synthesized with triethylamine/morpholine/tetraethylammonium hydroxide templates exhibited the highest total acidity, the smallest particle size, and high surface area, and produced a large amount of light hydrocarbons in biomass gasification. 相似文献
82.
Jute fibres were surface treated in order to enhance the interfacial interaction between jute natural fibres and an epoxy matrix. The fibres are exposed to alkali treatment in combination with organosilane coupling agents and aqueous epoxy dispersions. The surface topography and surface energy influenced by the treatments were characterized. Single fibre pull-out tests combined with SEM and AFM characterization of the fracture surfaces were used to identify the interfacial strengths and to reveal the mechanisms of failure. 相似文献
83.
84.
Although OFDM has become a widely used method for transmitting digital data on multicarrier frequencies in wideband digital communication, this scheme has barely been used for near field inductive communication. Therefore, in this paper, OFDM is applied to three inductive communication systems including two, three and four node systems in order to transmit data over inductive channels. Furthermore, the channel responses for these three circuits are analysed in details to clarify the accurate inductive channels for data transmission that were defined alternatively in other papers. Besides, the effects of second neighbour interaction on inductive systems are also included in this work. More importantly, the OFDM scheme has been simulated in MATLAB and implemented in MATLAB SIMULINK in order to verify the method in either theory or practice. The BER versus SNR performances obtained by simulation and implementation are compared with the theoretical results to verify the data transmission errors. 相似文献
85.
Ryan C. R. Gergely Stephen J. Pety Brett P. Krull Jason F. Patrick Thu Q. Doan Anthony M. Coppola Piyush R. Thakre Nancy R. Sottos Jeffrey S. Moore Scott R. White 《Advanced functional materials》2015,25(7):1043-1052
Complex multidimensional vascular polymers are created, enabled by sacrificial template materials of 0D to 3D. Sacrificial material consisting of the commodity biopolymer poly(lactic acid) is treated with a tin catalyst to accelerate thermal depolymerization, and formed into sacrificial templates across multiple dimensions and spanning several orders of magnitude in scale: spheres (0D), fibers (1D), sheets (2D), and 3D printed. Templates are embedded in a thermosetting polymer and removed using a thermal treatment process, vaporization of sacrificial components (VaSC), leaving behind an inverse replica. The effectiveness of VaSC is verified both ex situ and in situ, and the resulting structures are validated via flow rate testing. The VaSC platform is expanded to create vascular and porous architectures across a wide range of size and geometry, allowing engineering applications to take advantage of vascular designs optimized by biology. 相似文献
86.
Shen CC Wu CC Liu Y Yu J Chang CC Lam DD Chou CJ Lo L Wei KY 《Analytical chemistry》2011,83(17):6842-6848
A rapid and precise standard-bracketing method has been developed for measuring femtogram quantity rare earth element (REE) levels in natural carbonate samples by inductively coupled plasma sector field mass spectrometry that does not require chemical separation steps. A desolvation nebulization system was used to effectively reduce polyatomic interference and enhance sensitivity. REE/Ca ratios are calculated directly from the intensities of the ion beams of (46)Ca, (139)La, (140)Ce, (141)Pr, (146)Nd, (147)Sm, (153)Eu, (160)Gd, (159)Tb, (163)Dy, (165)Ho, (166)Er, (169)Tm, (172)Yb, and (175)Lu using external matrix-matched synthetic standards to correct for instrumental ratio drifting and mass discrimination. A routine measurement time of 3 min is typical for one sample containing 20-40 ppm Ca. Replicate measurements made on natural coral and foraminiferal samples with REE/Ca ratios of 2-242 nmol/mol show that external precisions of 1.9-6.5% (2 RSD) can be achieved with only 10-1000 fg of REEs in 10-20 μg of carbonate. We show that different sources for monthly resolved coral ultratrace REE variability can be distinguished using this method. For natural slow growth-rate carbonate materials, such as sclerosponges, tufa, and speleothems, the high sample throughput, high precision, and high temporal resolution REE records that can be produced with this procedure have the potential to provide valuable time-series records to advance our understanding of paleoclimatic and paleoenvironmental dynamics on different time scales. 相似文献
87.
88.
Cao Y. Nguyen Kazushi Sano Tu Vu Tran Tan Thanh Doan 《The Annals of Regional Science》2013,50(3):685-703
This paper developed a relocation pattern for analyzing decisions regarding the relocation process of individual firms by using discrete choice models. Within this framework, three decision points in the relocation process are maintained in the micro-simulation modeling. The first decision that is move or non-move is modeled by using a binary logit form with the outcome of the probability of moving. The second decision, choosing the destination region, is modeled as a multinomial logit model with the outcome of the conditional probability of choosing a region. The final decision, choosing the new zone, is estimated by considering the spatial interactions. For example, the correlation among firms in the deterministic term and the spatial correlation among zones in the error term are considered by mixed logit models. The results of the study indicated that large firms and older firms have a lower probability of relocation. Moreover, this research found out that migrating firms are more attracted in regions with high accessibility. Finally, spatial factors and land prices in a given zone strongly affect the zone choice decision-making process of all firms. 相似文献
89.
Bui Huy Khoi Le Doan Dien Radomir Lsztity Andras Salg 《Journal of the science of food and agriculture》1987,39(2):137-143
The protein and amino acid composition of several rice and maize varieties grown in North Vietnam, and their digestibility, was determined. The protein content (N×5.95) of rice cultivars ranged from 7.0 to 10.8% of which 70–80% was in the glutelin fraction. The true digestibility was relatively good (87.6–91.8%). In general, lysine and threonine were found to be the first and second nutritionally limiting amino acids, except for two varieties, which had a low content of sulphur-containing amino acids. The protein content of maize cultivars ranged from 8.4 to 12.9%. Zein and glutelin were the main components occurring in near-equal quantities (except in the opaque-2 mutant). The overall amino acid distribution was similar to that of maize grown in other countries. Lysine levels were relatively low, and it was the first nutritionally limiting amino acid, except in the opaque-2 cultivar, tryptophan being the second one. The digestibility ranged from 87.5 to 91.1%. 相似文献
90.
A new method for analysing complex mixtures, 1H 2D n.m.r., was used to determine polyaromatics in crude gas oil mixtures. 2D NMR overcomes the lack of resolution due to crowded 1D spectra and provides structural information. In particular, TOCSY (total correlation spectroscopy) 2D n.m.r. is well suited to polyaromatics because these molecules give specific 2D fingerprints which can be easily recognized. These patterns were selected and analysed in two ways: (1) specific fingerprint recognition using a pure compound library; (2) using the mixing time τm of the TOCSY sequence. Variation of τm gives a change in cross-peak intensities. The intensity variation curves are characteristic of spin systems and hence of the structures of compounds. Alkylated substitutions were also studied. The compounds were quantified. This strategy was used to analyse crude gas oils and measure the contents of separated alkylated naphthalene isomers, biphenyls, anthracene, phenanthrene and benzothiophene. 相似文献