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41.
微合金钢模拟焊接热影响区组织和韧性研究 总被引:3,自引:0,他引:3
采用焊接模拟试验方法,研究了不同峰值温度(Tmax)和不同冷却时间(t8/5),对合Ti-N、TI-NB-N两种微合金钢热影响(HAZ)显微组织、奥氏体晶粒度、冲击韧性影响。试验结果表明:Ti-N钢焊接热影响区比Ti-Nb-n钢具有更高的冲击韧性、更适用于大线能量的焊接条件。 相似文献
42.
《Materials and Manufacturing Processes》2006,21(8):819-823
Linear elastic fracture mechanics was used to optimize the vacuum heat-treatment procedures for conventional hot-work AISI H11 tool steel. The fracture toughness was determined with non-standard, circumferentially notched and fatigue-precracked tensile-test specimens. The fracture-testing method is sensitive to changes caused by variations in the microstructure resulting from the austenitizing and tempering temperatures as well as the homogeneity of the material itself. The combined tempering diagram- Rockwell-C hardness, Fracture toughness KIc, Tempering temperature was used for the choice of the vacuum heat-treatment parameters necessary to obtain the best properties for a given application with respect to the investigated steel. 相似文献
43.
Theoretical Analysis of the Fiber Pullout and Pushout Tests 总被引:4,自引:0,他引:4
Ronald J. Kerans Triplicane A. Parthasarathy 《Journal of the American Ceramic Society》1991,74(7):1585-1596
The fiber pullout and pushout tests have been analyzed to predict the load-displacement behavior in terms of fiber/matrix interface parameters. The effects of residual axial strain in the fiber and fiber surface topography were included. The residual axial strain was found to be a significant parameter. It is shown that the interface failure can be progressive or catastrophic. In the case of a progressive failure of the interface, the load-displacement curve is nonlinear. The portion of the curve from above the first nonlinearity to near the peak load can be predicted in terms of parameters of the interface, viz., the friction coefficient, the radial stress at the interface, the fracture toughness of the interface, and the residual axial strain in the fiber. Values for these parameters can be obtained from a single loaddeflection curve. The peak load and load drop, which are usually reported, are found not to be directly relatable to any interface property, since the length of the last portion of the fiber to debond is influenced by end effects and hence not easily predicted. However, for data which describe the peak load as a function of initial embedded length, that factor can be eliminated and the data reduced to yield the relevant interface parameters. In pullout, the peak and friction loads saturate with large specimen thickness. Catastrophic failure is favored when the debond initiation load is high or when residual stress is low. Finally, a methodology to extract interface parameters from experimental data is suggested. 相似文献
44.
G. SAID 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(8):606-614
Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (KIc) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed. 相似文献
45.
46.
Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications.
In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels
an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported
by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture
resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work
of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing
a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive
strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has
good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets
the requirements of performance and cost rendering it an attractive option for advanced structural applications. 相似文献
47.
Nanoadhesives of epoxy resin are synthesized and evaluated. They are organically modified by multiwalled carbon nanotubes (MWCNT) (1% by weight) as reinforcement. Tensile tests are conducted on multiple identical unnotched and notched specimens to evaluate the overloading and fracture behavior of the nanoadhesives and are compared with the neat epoxy resin. In comparison with the neat epoxy, it is found that the 1% MWCNT reinforcement increased the ultimate and residual strength by about 29% and 56%, respectively. In comparison with the neat resin, there is a 265% increase in the fracture toughness of the MWCNT adhesive. Fracture surface analysis revealed the various mechanisms by which the MWCNT adhesives acquire their superior strength and toughness in comparison with the neat resin. 相似文献
48.
49.
The surface-crack-in-flexure (SCF) method uses a Knoop indenter to create small, semielliptical surface precracks in beam specimens. Lateral cracks may interfere with the primary median crack and cause errors of up to 10% in determination of fracture toughness, particularly for materials for which the fracture toughness is ∼3 MPa·m1/2 or less. Although the residual-stress-damage zone is ground or polished away by hand by removing 4.5–5 times the indentation depth, this amount may not be sufficient to completely remove the lateral cracks in low-fracture-toughness materials. A series of tests were conducted on sintered alpha silicon carbide with different amounts of material removed after indentation. Once the lateral cracks were fully removed, the SCF results concurred with single-edged-precracked-beam and chevron-notched-beam data collected in accordance with ASTM Designation C1421. A simple remedy for the SCF method is to examine the outer ground surface for remnants of lateral cracks before fracture and to remove more material if necessary. 相似文献
50.
本文介绍一种作者自己设计的疲劳裂纹装置.它可以代替价格昂贵的高频疲劳试验机;用于对三点弯曲试件预制疲劳裂纹.该装置结构简单,容易制造.投资少,附加在车床上即可工作. 相似文献