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161.
Two obvious emissions are observed from the ZnS clusters encapsulated in zeolite-Y. The emissionaround 355 nm is sharp and weak, locating at the onset of the absorption edge. The bandaround 535 nm is broad. Strong and Stokes-shifted. Both the two emissions shift to blue andtheir intensities firstly increase then decrease as the loading of ZnS in zeolite-Y or clusters sizedecreases. Through investigation, the former is attributed to the excitonic fluorescence, andthe latter to the trapped luminescence from surface States. The cluster size-dependence of theluminescence may be explained qualitatively by considering both the carrier recombination andthe nonradiative recombination rates. Four peaks appearing in the excitation spectra are assignedto the transitions of 1S-1S, 1S-1P, 1S-1D and sudsce state, respectively. The excitation spectraof the clusters do not coincide with their absorption spectra. The states splitted by quantum-sizeconfinement are detected in the excitation spectra, but could not be differentiated in the opticalabsorption spectra due to inhomogeneous broadening. The size-dependence of the excitationspectra is similar to that of the absorption spectra. Both the excitation spectra of excitonicand of trapped emissions are similar, but change in relative intensity and shift in position areobserved. 相似文献
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164.
柴达木盆地鱼卡地区中侏罗统石门沟组发育多层油页岩,通过对YYY-1井全井岩心观察和地化分析,在页岩段和含煤段识别出两种类型油页岩。上部页岩段油页岩发育于深湖—半深湖环境中,含油率中等,单层和累计厚度均较大,w(TOC)为5.97%~15.35%,S_1+S_2为29.71~118.62 mg/g,有机质类型主要为Ⅰ型、Ⅱ1型,有机质来源主要以藻类体湖泊生物为主;下部含煤段油页岩发育于湖沼环境中,含油率较高,单层和累计厚度均较小,且与煤和炭质泥岩互层,w(TOC)为13.80%~48.80%,S_1+S_2为39.31~162.12mg/g,有机质类型主要为Ⅱ2型,有机质来源以陆源高等植物为主。沉积环境和有机质来源是影响这两种油页岩矿床差异的关键因素。 相似文献
165.
Changhu Xing Troy Munro Colby Jensen Benjamin White Heng Ban 《International Journal of Thermophysics》2014,35(8):1512-1525
The transient electrothermal technique has been shown to be an important method for the thermal characterization of fine fibers. However, this study shows that the accuracy of this method hinges on the proper consideration of several sample parameters including the initial electrical resistance and the emissivity of the sample. Such consideration is verified through measurement of platinum samples with various lengths. A multi-level heating scheme is proposed to mitigate the high sensitivity to the initial sample electrical resistance resulting in a demonstrated precision uncertainty of \({<}3~\%\) . Using a recently expanded thermal model accounting for heretofore neglected heat losses, the emissivity of the sample may be measured simultaneously with thermal conductivity. The influence of the vacuum level is demonstrated by the results of measurements at two vacuum levels \({<}0.001\hbox { Pa}\) (diaphragm plus turbo pumps) and \({\sim } 2\hbox { Pa}\) (regular rotary vane pump). Neglecting these considerations can produce seemingly viable measurement results having significant bias error. Based on the characteristics of the expanded model, a new approach is presented that takes advantage of the simplicity of the reduced model, which neglects lateral heat losses from the sample, to obtain sample thermal properties that are independent of heat loss effects. Lastly, several experimental results validate the new model. 相似文献
166.
17型车钩钩体易出现铸件尺寸精度超差的问题,通过芯盒工艺参数的修整,使钩体的钩尾销孔及厚度尺寸符合设计要求,提高了钩体铸造质量,钩体的组装合格率大为改善。 相似文献
167.
When normal human fibroblast cells (MRC-5) received a priming irradiation of 3-20 mGy 4 h prior to irradiation with 1000 mGy, the number of DNA double-stranded breaks (DSBs) decreased significantly to 18.2-18.7 per cell compared with 21 per cell when there was no priming irradiation. This result indicates that a priming irradiation of 3-20 mGy induces a radioadaptive response in MRC-5. The authors' previous study had indicated that DSBs induced by ≤ 20 mGy are due to a radiation-induced bystander effect. These findings suggest that radiation-induced bystander effects might contribute to induction of the radioadaptive response. To test this hypothesis, MRC-5 were suspended in lindane, an inhibitor of radiation-induced bystander effects, which was added to the medium for the priming irradiation of 3-20 mGy. Lindane inhibited the protective effect of priming irradiation on DSBs caused by subsequent irradiation with 1000 mGy. Thus, radiation-induced bystander effects may play a role in radioadaptive responses. 相似文献
168.
A.R. Khoei E. Ban P. Banihashemi M.J. Abdolhosseini Qomi 《Materials science & engineering. C, Materials for biological applications》2011,31(2):452-457
Carbon nanotubes (CNTs) are excellent candidates for torsional elements used in nanoelectro-mechanical systems (NEMS). Simulations show that after being twisted to a certain angle, they buckle and lose their mechanical strength. In this paper, classical molecular dynamics simulations are performed on single-walled carbon nanotubes (CNTs) to investigate the effects of torsion speed and temperature on CNT torsional properties. The AIREBO potential is employed to describe the bonded interactions between carbon atoms. The MD simulations clearly show that the buckling of CNTs in torsion is a reversible process, in which by unloading the buckled CNT in opposite direction, it returns to its original configuration. In addition, the numerical results reveal that the torsional shear modulus of CNTs increases by increasing the temperature and decreasing the torsion speed. Furthermore, the buckling torsion angle of CNTs increases by increasing the torsion speed and decreasing the temperature. Finally, it is observed that torsional properties of CNTs are highly affected by speed of twist and temperature of the nanotubes. 相似文献
169.
Applying face alignment after face detection exerts a heavy influence on face recognition. Many researchers have recently investigated face alignment using databases collected from images taken at close distances and with low magnification. However, in the cases of home‐service robots, captured images generally are of low resolution and low quality. Therefore, previous face alignment research, such as eye detection, is not appropriate for robot environments. The main purpose of this paper is to provide a new and effective approach in the alignment of small and blurred faces. We propose a face alignment method using the confidence value of Real‐AdaBoost with a modified census transform feature. We also evaluate the face recognition system to compare the proposed face alignment module with those of other systems. Experimental results show that the proposed method has a high recognition rate, higher than face alignment methods using a manually‐marked eye position. 相似文献
170.
Georgios Aristomenopoulos Timotheos Kastrinogiannis Zhaojun Li Symeon Papavassiliou 《Mobile Networks and Applications》2011,16(4):490-504
In this paper the problem of seamless mobility and proficient joint radio resource management over an all-IP internetworked
wireless heterogeneous environment is addressed. Nodes’ autonomicity is envisioned as the enabler to devise a Quality of Service
(QoS) aware architecture for supporting a variety of services, founded on a common utility based framework that provides enhanced
flexibility in reflecting different access networks’ type of resources and diverse QoS prerequisites, under a unified QoS-aware
resource allocation optimization problem. This allows a more in-depth intrinsic wireless network convergence, beyond All-IP,
driven by QoS-oriented resource management. This vision is demonstrated and instantiated for integrated WLAN and cellular
(both CDMA and OFDMA) networks, providing a viable path towards the evolution and realization of the future wireless networking
paradigm. Initial numerical results demonstrate the effectiveness of the proposed architecture and reveal the benefits of
such a service oriented paradigm against other existing access oriented autonomic designs. 相似文献