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21.
Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.
IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported
that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method
can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to
study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni
immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening
the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress. 相似文献
22.
Microhardness measurements have been performed on untreated (virgin) and electrically stressed, solvent‐cast laboratory‐prepared samples of pure poly(phenylene oxide) (PPO), pure polystyrene (PS), and PPO : PS polyblends with different weight proportions. Results of such measurement on untreated polyblend sample show that microhardness (Hv) increases with increase in the content of PS up to 10 wt %, which attributed to the existence of homogeneous phase morphology. However, this feature is not observable in samples containing higher content of PS. Electrical stress is found to modify considerably the mechanical property of polymer. The effect of electric field on the microhardness of such samples (PPO : PS :: 90 : 10) has been characterized by the existence of a peak. Trapping of charge carriers in electrically stressed samples imparts hardening to the polyblend up to an applied step field of 190 kV/cm. However, the excessive charging beyond this step field value destroys this characteristic. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
23.
"Mega"-analysis was developed by M. Carlson and N. Miller (see record 1987-31249-001) as an extension of traditional meta-analytic procedures for conducting integrative reviews of existing research literatures. One such mega-analysis was conducted by Carlson and Miller to synthesize the literature on the relation between negative mood states and helping. That analysis found no support for a theoretical account (negative state relief) that had been confirmed previously by using various experimental approaches. In an attempt to reconcile the discrepancy, the logic and methods used in Carlson and Miller's mega-analysis of the negative mood-helping literature were examined, and several serious problems were found. These problems are discussed, and data are presented to show that the results of that mega-analysis, and perhaps all mega-analyses, should not be viewed with confidence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
24.
G.Y. Sha F.C. Jiang D. Wang D.K. Liu and R.T.Department of Mechanical Engineering Harbin Engineering University Harbin ChinaShenyang National Laboratory for Materials Science Institute of Metal Research The Chinese Academy of Sciences Shenyang China 《金属学报(英文版)》2002,15(6):556-560
An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application. 相似文献
25.
F. Otsubo K. Kishitake T. Akiyama T. Terasaki 《Journal of Thermal Spray Technology》2003,12(4):555-559
It is known that the corrosion resistance of stainless steel is deteriorated by blasting, but the reason for this deterioration
is not clear. A blasted austenitic stainless steel plate (JIS-SUS304) has been characterized with comparison to the scraped
and non-blasted specimens. The surface roughness of the blasted specimen is larger than that of materials finished with #180
paper. A martensite phase is formed in the surface layer of both blasted and scraped specimens. Compressive residual stress
is generated in the blasted specimen and the maximum residual stress is formed at 50–100 μm from the surface. The corrosion
potentials of the blasted specimen and subsequently solution treated specimen are lower than that of the non-blasted specimen.
The passivation current densities of the blasted specimens are higher those of the non-blasted specimen. The blasted specimen
and the subsequently solution treated specimen exhibit rust in 5% sodium chloride (NaCl) solution, while the non-blasted specimen
and ground specimen do not rust in the solution. It is concluded that the deterioration of corrosion resistance of austenitic
stainless steel through blasting is caused by the roughed morphology of the surface. 相似文献
26.
Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within
the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively
simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the
heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of
this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize
the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress
are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during
quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in
terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to
search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear
blank case study is used to demonstrate the optimization scheme. 相似文献
27.
28.
29.
In this paper we describe an apparatus for reproducibly measuring thermal shock resistance of thick polymer layers bonded to metals. The thermal shock behavior is discussed in terms of epoxy samples bonded to an aluminum substrate. It was found that both high resin toughness and low resin thermal expansion coefficient improved thermal shock resistance of thick coatings, but only a sample containing 60wt. % glass beads did not develop a failure crack. Effects of sample thickness, temperature gradient, and resin composition on thermal shock behavior are discussed. 相似文献
30.
David A. Woodford Donald R. VanSteele Mohammed J. Hyder 《Journal of the American Ceramic Society》1991,74(12):3142-3144
The development of a tensile testing methodology for ceramics which enables a stress vs strain-rate response to be measured at high temperature is described. The test involves a carefully controled stress relaxation test at constant total strain using an experimental procedure and phenomenological analysis previously developed for metallic materials. It is demonstrated here with preliminary tests on alumina at 1050° and 1150°C. This offers, with further development, the possibility of establishing design stresses associated with low strain-rate behavior for structural applications. The results demonstrate that data covering four decades of strain rate may be generated in tests lasting a few hours. The inelastic strain consists of substantial anelastic recoverable strain in addition to a permanent creep strain. 相似文献