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排序方式: 共有2125条查询结果,搜索用时 15 毫秒
71.
Shinichi Itoh Kenji UenoRyuji Ohkubo Hidenori SagehashiYoshisato Funahashi Tetsuya Yokoo 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,654(1):527-531
We investigated the irradiation properties of the components of a T0 chopper. The organic materials in the rotor bearing grease, the magnetic fluids in seals, and the rubber in the timing belt, as well as the semiconductor materials in the rotation sensor and motor encoder, were all irradiated with high-energy γ-rays up to 100 kGy. No significant damage that shortens the lifetime of a T0 chopper was observed for the mechanical components. However, the semiconductor components were damaged by the irradiation. For the rotation sensor system detecting the rotor phase, the signal from a marker on the rotor shaft was transmitted outside the shielding by an optical fiber with radiation-proofing and the electrical circuits were removed from the beamline shielding. The lifetime of the motor encoder possibly meets the requirement for the maintenance period of the T0 chopper. 相似文献
72.
Ryo Watada Makoto Ohsaki Yoshihiro Kanno 《Structural and Multidisciplinary Optimization》2011,43(4):459-471
Uniqueness and symmetry of solution are investigated for topology optimization of a symmetric continuum structure subjected
to symmetrically distributed loads. The structure is discretized into finite elements, and the compliance is minimized under
constraint on the structural volume. The design variables are the densities of materials of elements, and intermediate densities
are penalized to prevent convergence to a gray solution. A path of solution satisfying conditions for local optimality is
traced using the continuation method with respect to the penalization parameter. It is shown that the rate form of the solution
path can be formulated from the optimality conditions, and the uniqueness and bifurcation of the path are related to eigenvalues
and eigenvectors of the Jacobian of the governing equations. This way, local uniqueness and symmetry breaking process of the
solution are rigorously investigated through the bifurcation of a solution path. 相似文献
73.
Acid catalyzed reactions of 1-octene on TiO2 in sub- and supercritical water were investigated (T = 250-450 °C, P = 11-33 MPa). The main products were 2-octene and 2-octanol. Additionally, other liner C8 alkenes and liner secondary C8 alcohols were produced as by-products. Through kinetic analysis, acid catalyzed reactions can divide into the reaction catalyzed by Lewis acidic sites on TiO2 and the reaction catalyzed by protons produced by the dissociation of water molecules. Each type of the reaction is affected by water density or ionic product of water, respectively, therefore, reaction mechanism changes with temperature and pressure. From the contribution of each reaction type, the temperature dependence of cis/trans ratio of produced 2-octene could also be explained. 相似文献
74.
Takagi S Frukhtbeyn S Chow LC Sugawara A Fujikawa K Ogata H Hayashi M Ogiso B 《Journal of research of the National Institute of Standards and Technology》2010,115(4):267-276
This study reports for the first time in vitro and in vivo properties of fluorapatite (FA)-forming calcium phosphate cements (CPCs). The experimental cements contained from (0 to 3.1) mass % of F, corresponding to presence of FA at levels of approximately (0 to 87) mass %. The crystallinity of the apatitic cement product increased greatly with the FA content. When implanted subcutaneously in rats, the in vivo resorption rate decreased significantly with increasing FA content. The cement with the highest FA content was not resorbed in soft tissue, making it the first known biocompatible and bioinert CPC. These bioinert CPCs might be useful for applications where slow or no resorption of the implant is required to achieve the desired clinical outcome. 相似文献
75.
A relationship between emission characteristics of Ba atom as an emitter material and temperature distributions of an electrode in a fluorescent lamp is described, which is measured by using laser-induced fluorescence and black-body radiation method, respectively. In a virgin lamp, a hot spot observed at the electrode edge connected to the power supply is the main source of Ba atom emission. In a long-term-used lamp, it is shown that Ba atom emission, thermionic electron emission in cathode half-cycle and electron collection in anode half-cycle are most active on the hot spot appearing on the center of the electrode. 相似文献
76.
Makoto Muranaka 《Materials Letters》2010,64(8):969-9897
Poly(ethylene glycol)-block-polylactide (PEG-PLA) nanoparticles were prepared through the oil-in-water (O/W, ethyl acetate/water) emulsion technique using oil-soluble PEG-PLA in the presence of water-soluble PEG-PLA as a surfactant. The particle diameter decreased with increasing water-soluble PEG-PLA concentration, the smallest averaged diameter was 75 nm. From these results, it was found that water-soluble PEG-PLA acted as a surfactant which prevents further coalescence of droplets. In addition, the particles diameter decreased with increasing hydrophile-lipophile balance of oil-soluble PEG-PLA in the absence of water-soluble PEG-PLA. In contrast, the particle diameter was constant in the presence of water-soluble PEG-PLA. Therefore, the capability of water-soluble PEG-PLA as a surfactant was more excellent than that of oil-soluble PEG-PLA. 相似文献
77.
The paper presents two types of a passive safety containment for a near future BWR. They are named Mark S and Mark X containment. One of their common merits is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. The PCV pressure can be moderated within the design pressure. Another merit is the capability to submerge the PCV and the RPV above the core level. The third merit is robustness against external events such as a large commercial airplane crash. Both the containments have a passive cooling core catcher that has radial cooling channels. The Mark S containment is made of reinforced concrete and applicable to a large power BWR up to 1830 MWe. The Mark X containment has the steel secondary containment and can be cooled by natural circulation of outside air. It can accommodate a medium power BWR up to 1380 MWe. In both cases the plants have active and passive safety systems constituting in-depth hybrid safety (IDHS). The IDHS provides not only hardware diversity between active and passive safety systems but also more importantly diversity of the ultimate heat sinks between the atmosphere and the sea water. Although the plant concept discussed in the paper uses well-established technology, plant performance including economy is innovatively and evolutionally improved. Nothing is new in the hardware but everything is new in the performance. 相似文献
78.
79.
Chunquan Xu Aiguo Ming Takeharu Nagaoka Makoto Shimojo 《Journal of Intelligent and Robotic Systems》2009,56(3):277-299
In this paper we discuss our simulation and empirical study of a golf swing motion controller for a two-link golf swing robot.
We distinguish two variants of the whole golf swing termed as hitting problem and stopping problem. For the hitting problem
arising from backswing and downswing, we map the task into the output of a target dynamic system—a harmonic oscillator—under
energy control. For the stopping problem that arises from follow-through, we propose a Proportional plus Gravity and Coupling
Torque Compensation (PGCTC) feedback controller. Preliminary simulation study shows the proposed controllers solve the hitting
problem and the stopping problem respectively. The controllers are implemented on a physical robot. Experimental results indicate
the robot is able to perform desired golf swing-backswing, downswing, and follow-through. We also give a preliminary analysis
on the proposed method to understand its merits and weaknesses. 相似文献
80.
In this study we revisit Weiser’s (1991) [5] vision of seamlessly integrated computing. We focus on nomadic workers who rely extensively on mobile technologies to conduct work. Using Star and Ruhleder’s (1996) [10] properties of infrastructure, we discuss how nonroutine users of infrastructure face particular challenges. We conducted an ethnographic investigation of nomadic workers in a large distributed organization. We examined strategies that they use to assemble their mobile office, to seek resources, and to synchronize with others across time zones. We discuss how their strategies are challenged by their lack of local knowledge of infrastructure. Our results suggest that until the field of pervasive computing can attain Weiser’s vision, the very users of ubiquitous computing need infrastructure to be visible. We discuss the implications for a design to support nomadic work. 相似文献