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991.
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
992.
993.
Seok Jin Lim Suk Jae Jeong Kyung Sup Kim Myon Woong Park 《The International Journal of Advanced Manufacturing Technology》2006,28(5-6):618-625
Today’s business environment is experiencing as a period of expansion and the globalization. Therefore, a distribution plan
with low cost and high customer satisfaction in supply chain management (SCM) has been widely investigated. The purpose of
this study is to establish optimal distribution planning in the supply chain. In this paper, a hybrid approach involving a
genetic algorithm (GA) and simulation is presented to solve this problem. The GA is employed in order to quickly generate
feasible distribution sequences. Considering uncertain factors such as queuing, breakdowns and repairing time in the supply
chain, the simulation is used to minimize completion time for the distribution plan. The computational results for an example
of a simple supply chain are given and discussed to validate the proposed approach. We obtained a more realistic distribution
plan with optimal completion time by performing the iterative hybrid GA simulation procedure which reflects the stochastic
nature of supply chains. 相似文献
994.
Hyunpung Park Kwan H. Lee 《The International Journal of Advanced Manufacturing Technology》2005,27(3-4):313-320
Parametric modeling technology is difficult to apply to freeform mesh models since there is no efficient way to impose geometric
constraints. In this paper, we propose a novel method to control freeform mesh models parametrically. Our approach is to construct
a control mesh that surrounds an object model and then impose constraints on it. The control mesh is parametrically controlled
and the shape of the object model is modified by using an existing freeform deformation method.
This paper is mainly concerned with automated construction of a control mesh and treatment of geometric constraints. Procedures
for creating a control mesh are as follows: 1) determine the optimal orientation of the model, 2) project the model along
three axes and extract contours, 3) create 2D control polygons for the contours, and 4) construct the 3D control mesh from
the 2D control polygons. Geometric constraints are imposed on the edges and faces of a control mesh. Types of constraints
are given by either a relative relationship between elements or an absolute displacement. A new control mesh is calculated
by solving these constraints and the original model is modified accordingly. We tested our algorithms for two freeform models. 相似文献
995.
Kono Y Park C Sakamaki T Kenny-Benson C Shen G Wang Y 《The Review of scientific instruments》2012,83(3):033905
An integration of multi-angle energy-dispersive x-ray diffraction and ultrasonic elastic wave velocity measurements in a Paris-Edinburgh cell enabled us to simultaneously investigate the structures and elastic wave velocities of amorphous materials at high pressure and high temperature conditions. We report the first simultaneous structure and elastic wave velocity measurement for SiO(2) glass at pressures up to 6.8 GPa at around 500°C. The first sharp diffraction peak (FSDP) in the structure factor S(Q) evidently shifted to higher Q with increasing pressure, reflecting the shrinking of intermediate-range order, while the Si-O bond distance was almost unchanged up to 6.8 GPa. In correlation with the shift of FSDP position, compressional wave velocity (Vp) and Poisson's ratio increased markedly with increasing pressure. In contrast, shear wave velocity (Vs) changed only at pressures below 4 GPa, and then remained unchanged at ~4.0-6.8 GPa. These observations indicate a strong correlation between the intermediate range order variations and Vp or Poisson's ratio, but a complicated behavior for Vs. The result demonstrates a new capability of simultaneous measurement of structures and elastic wave velocities at high pressure and high temperature conditions to provide direct link between microscopic structure and macroscopic elastic properties of amorphous materials. 相似文献
996.
Eun-Goo Kang Sung-Jun Park Sang-Jo Lee 《The International Journal of Advanced Manufacturing Technology》2005,25(7-8):647-651
The measurement of cutting force is one of the most frequently used techniques for monitoring machining processes. Its widespread application ranges from tool condition identification, feedback control and cutting system design to process optimization.This paper suggests another system for measuring cutting force in milling processes. Generally, tool dynamometers are taken into account for the most appropriate cutting force measuring tool in the analysis of a cutting mechanism. However, high prices and limited working space make in situ systems difficult for a controllable milling process. Although an alternative suggestion is to use an AC current from a servomotor, it is unsuitable for cutting force monitoring because of a small upper frequency limit and noise.The suggested cutting force measuring system is composed of two piezo load cells placed between the moving table bracket and the nut flange of the ball screw. It has many advantages, such as lower cost and a wider measurement range than the tool dynamometer, over using the built-in feeding system and the low-cost piezo load cell for applying a conventional machining center.This paper focuses on the performance test of a newly developed measuring system. By comparing the cutting force between the tool dynamometer and the system developed from a series of end milling experiments, the accuracy of the cutting force measurement system was verified. Linearity, transverse sensitivity and the upper frequency limit of the system were verified by experiment. 相似文献
997.
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
998.
Park KH Lee SQ Kim EK Moon SE Cho YH Gokarna A Jin LH Kim S Cho W Lee YI 《Ultramicroscopy》2008,108(10):1319-1324
We have developed a low cost and a highly compact bio-chip detection technology by modifying a commercially available optical pick-up head for CD/DVD. The highly parallel and miniaturized hybridization assays are addressed by the fluorescence emitted by the DNA-chip using the optical pick-up head. The gap between the objective lens and the bio-chip is regulated by the focus servo during the detection of the fluorescence signal. High-resolution and high-speed scanning is effectively realized by this simple scanning system instead of utilizing high-precision mechanism. Regardless of achievement of effective detection mechanism, the technique of fluorescence detection can prove to be disadvantageous because of the low stability of the dyes with low S/N ratio and an expensive setup such as a PMT detector is always required for fluorescence detection. We propose, for the first time, a novel scanning scheme based on metal nanoparticles in combination with a bio-chip substrate having a phase change recording layer. We found that the phase change process is highly affected by the existence of the densely condensed metal nanoparticles on the phase change layer during the writing process of the pick-up head. 相似文献
999.
1000.
Hong-Jai Park Hyeon-Soo Park Jae-Ung Lee Alfred L. M. Bothwell Je-Min Choi 《International journal of molecular sciences》2016,17(8)
Peroxisome proliferator-activated receptor gamma (PPARγ) has recently been recognized to regulate adaptive immunity through Th17 differentiation, Treg functions, and TFH responses. However, its role in adaptive immunity and autoimmune disease is still not clear, possibly due to sexual differences. Here, we investigated in vitro treatment study with the PPARγ agonist pioglitazone to compare Th1, Th2, and Th17 differentiation in male and female mouse splenic T cells. Pioglitazone treatment significantly inhibited various effector T cell differentiations including Th1, Th2, and Th17 cells from female naïve T cells, but it selectively reduced IL-17 production in male Th17 differentiation. Interestingly, pioglitazone and estradiol (E2) co-treatment of T cells in males inhibited differentiation of Th1, Th2, and Th17 cells, suggesting a mechanism for the greater sensitivity of PPARγ to ligand treatment in the regulation of effector T cell differentiation in females. Collectively, these results demonstrate that PPARγ selectively inhibits Th17 differentiation only in male T cells and modulates Th1, Th2, and Th17 differentiation in female T cells based on different level of estrogen exposure. Accordingly, PPARγ could be an important immune regulator of sexual differences in adaptive immunity. 相似文献