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71.
Tae Jo Ko Jung Whan Park Hee Sool Kim Sun Ho Kim 《The International Journal of Advanced Manufacturing Technology》2007,32(7-8):739-746
Once a machining process is finished, an inspection process is carried out to check whether the part is within dimensional
tolerances. A coordinate measuring machine (CMM) is a general metrological device for assessment of dimensions on the shop
floor. It cannot be ignored, however, that CMM measurements require significant resources in operating time and cost, which
has led to many studies into on-machine measurement (OMM) systems. This study aims to develop an OMM system with a noncontacting
laser displacement sensing apparatus and a computer-aided design (CAD) model for ease of operation, improved operating speed,
and free form profiling. The system is composed of two software modules, one for sensor alignment with the machine tool and
the other for measurement based on CAD/CAM (computer-aided machining). Consequently, the system was verified on the shop floor
at a numerical control (NC) machining center. 相似文献
72.
In this research, a remote control system has been developed and implemented, which combines autonomous obstacle avoidance
in real-time with force-reflective tele-operation. A teleoperated mobile robot is controlled by a local two-degrees-of-freedom
force-reflective joystick that a human operator holds while he is monitoring the screen. In the system, the force-reflective
joystick transforms the relation between a mobile robot and the environment to the operator as a virtual force which is generated
in the form of a new collision vector and reflected to the operator. This reflected force makes the tele-operation of a mobile
robot safe from collision in an uncertain and obstacle-cluttered remote environment. A mobile robot controlled by a local
operator usually takes pictures of remote environments and sends the images back to the operator over the Internet. Because
of limitations of communication bandwidth and the narrow viewangles of the camera, the operator cannot observe shadow regions
and curved spaces frequently. To overcome this problem, a new form of virtual force is generated along the collision vector
according to both distance and approaching velocity between an obstacle and the mobile robot, which is obtained from ultrasonic
sensors. This virtual force is transferred back to the two-degrees-of-freedom master joystick over the Internet to enable
a human operator to feel the geometrical relation between the mobile robot and the obstacle. It is demonstrated by experiments
that this haptic reflection improves the performance of a tele-operated mobile robot significantly. 相似文献
73.
Shen C.F. Chang S.J. Ko T.K. Shei S.C. Lai W.C. Chang C.S. Chen W.S. Huang S.P. Ku Y.W. Horng R.H. 《Optoelectronics, IET》2007,1(1):27-30
Nitride-based high power flip-chip near-ultraviolet (UV) light emitting diodes (LEDs) with a reflective mirror are fabricated by depositing Al onto a Si submount. It is demonstrated that the Al layer coated onto a Si submount can effectively reflect downward emitting photons for flip-chip LEDs. Although the operation voltage of the proposed LEDs is slightly increased, it is found that the output power is at least 30% higher than that of conventional LEDs. It is also found that flip-chip near-UV LEDs are more reliable than conventional non-flip-chip LEDs 相似文献
74.
75.
S. Daneshpour M. Koçak S. Langlade M. Horstmann 《International Journal of Fatigue》2009,31(10):1603-1612
Investigations on fatigue crack growth retardation due to single tensile and periodic multiple over load in strength undermatched laser beam welded 3.2 mm thick aerospace grade aluminium alloy 2139-T8 sheets are conducted. The effect of overload on the fatigue crack propagation behaviours of the homogenous base metal and welded panels (200 mm wide, centre cracked) was compared using experimental and FE analysis methods. The effective crack tip plasticity has been determined in homogeneous M(T) specimens using Irwin’s method and in both homogeneous and laser welded specimen by calculating crack tip plastic strain using FE analysis for single tensile overload. The crack retardation due to the overload in welded specimens is described by the Wheeler Model. The crack tip plastic zone size in the welded specimen was determined by FE analysis using maximum plastic zone extension at the mid sheet thickness. The results show that the Wheeler Model can be implemented to the highly heterogeneous undermatched weld to describe the crack retardation in fatigue following single tensile overload. Fatigue crack growth retardation due to single overload is found to be larger than the base metal. However, after periodic multiple overload, shorter crack retardation has occurred for undermatched welds than the base metal. 相似文献
76.
The phrase “not in my backyard” (NIMBY) refers to the well-known social phenomena in which residents oppose the construction or location of undesirable facilities near their homes. Examples of such facilities include electric transmission lines, recycling centers and crematoria. Due to the opposition typically encountered in constructing an undesirable facility, the facility planner should understand the nature of the NIMBY phenomena and consider it as a key factor in determining facility location. We examine the characteristics of NIMBY phenomena and suggest two alternative mathematical optimization models with the objective of minimizing the total degree of NIMBY sentiments. Genetic algorithms are proposed to solve our linear and nonlinear integer programs. The results obtained via genetic algorithms for our linear integer programs are compared with those of CPLEX to evaluate their performance. The nonlinear programs are tested with various allocation policies. Sensitivity analysis is conducted about several system parameters. 相似文献
77.
Wildfire smoke detection is particularly important for early warning systems, because smoke usually rises before flames arise. Therefore, this paper presents an automatic wildfire smoke detection method using computer vision and pattern recognition techniques. First, candidate blocks are identified using key-frame differences and nonparametric smoke color models to detect smoke-colored moving objects. Subsequently, three-dimensional spatiotemporal volumes are built by combining the candidate blocks in the current key-frame with the corresponding blocks in previous frames. A histogram of oriented gradient (HOG) is extracted, and a histogram of oriented optical flow (HOOF) is extracted as a temporal feature based on the fact that the direction of smoke diffusion is upward owing to thermal convection. From spatiotemporal features of training data, a visual codebook and a bag-of-features (BoF) histogram are generated using our proposed weighting scheme. For smoke verification, a random forest classifier is built during the training phase using the BoF histogram. The random forest with the BoF histogram can increase the detection accuracy performance when compared with related methods and allow smoke detection to be carried out in near real time. 相似文献
78.
Rong Chen Shujian Li Ko Tae Jo Pengnan Li Yong Jiang Changping Li Qiulin Niu 《Journal of Mechanical Science and Technology》2020,34(3):1219-1225
Journal of Mechanical Science and Technology - As a kind of typical structure, the hat-shaped structure (HSS) is widely used in carbon fiber reinforced plastics (CFRP) aircraft parts. In this work,... 相似文献
79.
Im Deok Jung Min Kook Cho Kong Myeong Bae Sang Min Lee Phill Gu Jung Ho Kyung Kim Sung Sik Kim Jong Soo Ko 《ETRI Journal》2008,30(5):747-749
We introduce a pixel‐structured scintillator realized on a flexible polymeric substrate and demonstrate its feasibility as an X‐ray converter when it is coupled to photosensitive elements. The sample was prepared by filling Gd2O2S:Tb scintillation material into a square‐pore‐shape cavity array fabricated with polyethylene. For comparison, a sample with the conventional continuous geometry was also prepared. Although the pixelated geometry showed X‐ray sensitivity of about 58% compared with the conventional geometry, the resolving power was improved by about 70% above a spatial frequency of 3 mm?1. The spatial frequency at 10% of the modulation‐transfer function was about 6 mm?1. 相似文献
80.
Multicasting is a useful communication method in wireless mesh networks (WMNs). Many applications in WMNs require efficient
and reliable multicast communications, i.e., high delivery ratio with low overhead among a group of recipients. In spite of
its significance, little work has been done on providing such multicast service in multi-channel WMNs. Traditional multicast
protocols for wireless and multi-hop networks tend to assume that all nodes, each of which is equipped with a single interface,
collaborate on the same channel. This single-channel assumption is not always true, as WMNs often provide nodes with multiple
interfaces to enhance performance. In multi-channel and multi-interface (MCMI) WMNs, the same multicast data must be sent
multiple times by a sender node if its neighboring nodes operate on different channels. In this paper, we try to tackle the
challenging issue of how to design a multicast protocol more suitable for MCMI WMNs. Our multicast protocol builds multicast
paths while inviting multicast members, and tries to allocate the same channel to neighboring members in a bottom-up manner.
By unifying fixed channels of one-hop multicast neighbors, the proposed algorithm can improve the performance such as reducing
multicast data transmission overhead and delay, while managing a successful delivery ratio. In order to prove such expectation
on the performance, we have implemented and evaluated the proposed solution on the real testbed having the maximum 24 nodes,
each of which is equipped with two IEEE 802.11a Atheros WLAN cards. 相似文献