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91.
Study on the Stability of Ion-exchange Resin Catalysts:Ⅰ. TGA as a Rapid Evaluating Method 总被引:1,自引:1,他引:0
Wilbert Tsao 《中国炼油与石油化工》2010,(2)
The thermal stability of five commercial ion-exchange resin catalysts was studied by means of thermal gravimetric analysis(TGA) at elevated temperatures of up to 600℃and isothermal temperatures in the range of 150℃and 200℃.Resin samples with different initial water contents were also investigated.The study indicated that TGA,as a complementary evaluating method for the plug flow reactor system approach,could be used as a fast analyzing means for study on the thermal stability of ion-exchange resin cataly... 相似文献
92.
This study presents a rapid and simple approach for creating silicon nanostructures using metal-assisted etching. The thickness of the metal layer was found to be a key process parameter affecting the surface morphology of silicon nanostructures. Au and Ag layers with a thickness of 3 nm, 5 nm, and 10 nm were used to study the effects of metal catalyst thickness on silicon nanostructure morphology. The experimental results show that the surface morphology of metal has a significant influence on the silicon nanostructure morphology, such that the silicon nanostructures transform from porous silicon surfaces into filament nanostructures or silicon nanowire with increasing thicknesses of both the Au and Ag metal layers. 相似文献
93.
Szu-Hsien Chen Ching-Ting Tsao Chih-Hao Chang Yi-Ting Lai Ming-Fung Wu Ching-Nan Chuang Hung-Chia Chou Chih-Kuang Wang Kuo-Haung Hsieh 《Materials science & engineering. C, Materials for biological applications》2013,33(5):2584-2594
Wound dressings of chitosan are biocompatible, biodegradable, antibacterial and hemostatic biomaterials. However, applications for chitosan are limited due to its poor mechanical properties. Here, we conducted an in vivo mouse angiogenesis study on reinforced poly(ethylene glycol) (PEG)-chitosan (RPC) hydrogels. RPC hydrogels were formed by cross-linking chitosan with PEGs of different molecular weights at various PEG to chitosan ratios in our previous paper. These dressings can keep the wound moist, had good gas exchange capacity, and was capable of absorbing or removing the wound exudate. We examined the ability of these RPC hydrogels and neat chitosan to heal small cuts and full-thickness skin defects on the backs of male Balb/c mice. Histological examination revealed that chitosan suppressed the infiltration of inflammatory cells and accelerated fibroblast proliferation, while PEG enhanced epithelial migration. The RPC hydrogels promoted wound healing in the small cuts and full layer wounds. The optimal RPC hydrogel had a swelling ratio of 100% and a water vapor transmission rate (WVTR) of about 2000 g/m2/day. In addition, they possess good mechanical property and appropriate degradation rates. Thus, the optimal RPC hydrogel formulation functioned effectively as a wound dressing and promoted wound healing. 相似文献
94.
Abstract Charge‐temperature, modified from bias‐temperature, technique is presented for the investigation of the interface properties of Al‐SiO2‐Si (P) MOS capacitors. By using this technique, the change of interface trap states was found to be related to the treatment of charge‐temperature agin gand consequently the distribution of the mobile charges inside the oxide. An equivalent equation is expressed for the evaluation of interface trap states from the measured C‐V data. In addition, a two‐region model describing the distributions of the mobile charges of the capacitor after various charge‐temperature agings is proposed for the experimental observations. And the fitting results indicate that the effective Debye length due to interface trap states is about 20 Å. 相似文献
95.
Drilling is the mostly used secondary machining of the fiber reinforced composite laminates, while the delamination occurs frequently at the drill exit in the workpiece. In the industrial experiences, core drill shows better drilling quality than twist drill. However, chip removal is a troublesome problem when using the core drill. Conventional compound core-special drills (core-special drills and step-core-special drills) are designed to avoid the chip removal clog in drilling. But the cutting velocity ratio (relative motion) between outer drill and inner drill is null for conventional compound core-special drills. The current study develops a new device and to solve the problems of relative motion and chip removal between the outer and inner drills in drilling CFRP composite laminates. In addition, this study investigates the influence of drilling parameters (cutting velocity ratio, feed rate, stretch, inner drill type and inner drill diameter) on thrust force of compound core-special drills. An innovative device can be consulted in application of compound core-special drill in different industries in the future. 相似文献
96.
Hong Tsao Olga Rechkoblit Shantu Amin Nicholas E. Geacintov 《Polycyclic Aromatic Compounds》2013,33(1-4):1-10
Adducts derived from the binding of the (+)-7R,8S,9S,10R and (?)-7S,8R,9R,10S enantiomers of r7,t8-dihydrodiol-t9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) to 2′-deoxyguanosine residues in DNA are known to induce mutations due to error-prone DNA replication. Because the conformational properties of these lesions may be important in these phenomena, we have examined the effects of the stereoisomeric (+)- and (?)-trans-anti-[BP]-N 2-dG lesions positioned site-specifically at or near primer/template oligonucleotide junctions on DNA bending using high resolution gel electrophoresis. Remarkable differences in electrophoretic mobilities μ are observed in the two adducts derived from the tumorigenic (+)-anti-BPDE, and the non-tumorigenic (?)-anti-BPDE enantiomer. With the (+)-trans lesion positioned on the template strand adjacent to the 3′-end of the primer strand, a remarkable decrease in μ is observed. This suggests the existence of a bend at the single strand-double strand junction. Only modest decreases in μ are observed in the case of the (?)-trans lesion, or when the 3′-end is opposite to, or more distant from the lesion site. These observations are discussed in terms of the known NMR solution structures of these lesions in the same sequence context, and the properties of primer/template DNA in polymerases. 相似文献
97.
Worldwide Interoperability for Microwave Access (WiMAX) technology, which is based on the IEEE 802.16 standard, supports different quality of service (QoS) for different services. WiMAX is expected to support QoS in real-time applications such as Voice over Internet Protocol (VoIP). When network congestion occurs, the VoIP bit rate needs to be adjusted to achieve the best speech quality. In this study, we propose a new scheme called Adaptive VoIP Level Coding (AVLC). This scheme takes into consideration network conditions (packet delay and packet loss) and a connection’s modulation scheme. The amount of data that can be transmitted increases with the speed of the modulation scheme. When network congestion occurs, AVLC scheme prioritizes reducing the bit rate of a connection that has a slower modulation scheme to mitigate congestion. Depending on network conditions, such as modulation scheme, packet delay, packet loss, and residual time slot, we use the G.722.2 codec to adjust each connection’s bit rate. Simulations are conducted to test the performance (network delay, packet loss, number of modulation symbols, and R-score) of the proposed scheme. The simulation results indicate that speech quality is improved by the use of AVLC. 相似文献
98.
Drilling is an indispensible machining process for building a load-carrying structure of composite materials. Delamination defect is often produced at the exit of drilling, which threatens the service safety of the structure. There are back-up methods to reduce delamination when drilling the open flat-plate composite structure, but none for drilling into the curved-surface or hollow-shape structures. This study describes an innovative method using electromagnet and the deformable inexpensive colloid mixed with iron powder to produce magnetic back-up force at drilling exit to suppress delamination in industrial tube parts. The delamination extent can be reduced by 60–80%. The optimal volume ratio of powder-to-colloid is found 1:3. 相似文献
99.
For 10GBASE-T systems, variation in a multiple-input-multiple-output (MIMO) channel degrades the decision-point signal-to-noise ratio (DP-SNR) owing to imperfect pre-equalisation in the Tomlinson-Harashima precoding (THP) at the transmitter sides and catastrophic error propagation in far-end crosstalk (FEXT) cancellation at the receiver sides. Moreover, by using fixed THP coefficients during data transmission, as specified in the 10GBASE-T standard, and the non-linearity of THP pose challenges in the design of adaptive receivers. The authors propose an adaptive two-stage equalisation and FEXT cancellation (TS-EFC) architecture without updating the THP coefficients to combat channel variation at both the transmitter and receiver sides. In the first stage, we propose a new non-decision-directed FEXT canceller at the transmitter side using a joint training architecture to avoid error propagation. In the second stage, we devise an adaptive MIMO equaliser together with a novel pre-processing unit at the receiver side to combat channel variation. The pre-processing unit can eliminate the non-linearity issue by estimating both effective data sequences and precoded channel inputs. In addition, we develop a block least mean square algorithm that exploits the properties of two-dimensional modulated symbols for updating coefficients of the adaptive MIMO equaliser. Simulation results show that our TS-EFC architecture is robust against channel variation and significantly improves the DP-SNR. It eliminates the error propagation and also achieves faster convergence rates during the adaptation process. 相似文献
100.
For development of a lead-free composite solder for advance electrical components, a series of Sn3.5Ag0.25Cu (SAC) solders containing TiO2 nanopowders have been studied. The results showed that the addition of 0.25–1 wt.% TiO2 nanopowders into the lead-free SAC solder caused its liquidus temperature to increase by about 3.5–5.9 °C. Metallographic observations of the lead-free SAC composite solders revealed a reduction in the grain size of β-Sn, Ag3Sn phase and Ag3Sn phase located between the spacing lamellae. In terms of mechanical behavior, the addition of larger weight fractions of TiO2 nanopowders in lead-free SAC solder matrix led to an improvement in microhardness, 0.2%YS and UTS. However, ductility of the lead-free SAC composite solders was observed to decrease. 相似文献