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61.
To determine level of alcohol use/misuse and to examine correlates of these behaviors, 1,314 fourth-grade students were surveyed. The questionnaire included 55 items concerning tolerance of deviance, deviant self-image, self-efficacy, susceptibility to peer pressure, personal and peer approval of alcohol use, peer adjustment, parent nurturance and monitoring, family adjustment, parental permissiveness, peer use of alcohol, and exposure to alcohol. The items were factor analyzed and indices constructed. The indices generally had acceptable alpha coefficients (alpha = .61-.91); two exceptions were peer adjustment (alpha = .51) and parental permissiveness (alpha = .42). Tolerance of deviance, deviant self-image, susceptibility to peer pressure, personal and peer approval, peer use and exposure by peers, and parental permissiveness were positively correlated with alcohol use/misuse. Self-efficacy, child-parent interactions, family adjustment, and peer adjustment were negatively correlated with alcohol use/misuse. Implications for the design of family-based alcohol use/misuse prevention programs are discussed. 相似文献
62.
The escalating cost of medical care in the United States, especially in the past decade, has resulted in efforts to identify the factors contributing to rising costs. One factor often assumed to cause higher medical costs is the physician's fear of liability for not using the latest available technology. In this article, we report the results of a case study we conducted to better understand the relationship between the introduction and use of one particular technology, low-osmolar contrast agents, and liability concerns. Our study suggests that both clinicians and administrators are primarily guided by the medical benefits of low-osmolar contrast agents, and that liability concerns, although widespread, are of secondary importance. The inability to control this and similar technologies is likely to put a far greater strain on the nation's health care resources than is the practice of defensive medicine. These findings may be helpful to health policy makers, physicians, administrators, and legislators considering choices for health care reform in general and for medical liability reform in particular. 相似文献
63.
Compact conical antennas for wide-band coverage 总被引:7,自引:0,他引:7
A broadband antenna with a vertically polarized, omnidirectional electric field is studied. The design of the antenna and its feeding system in the wide frequency range from 20 to 1000 MHz is described and the driving-point impedance determined. Also calculated are the voltage standing-wave ratio (VSWR) and the input impedance of a transmission line connected to the antenna. More efficient operation at low frequencies is obtained by adding a length of transmission line to form a resonant section with the antenna. The effect of the different properties of the earth's surface on the field pattern is treated in a companion paper 相似文献
64.
The serum amyloid A (SAA) superfamily comprises a number of genes and proteins characterized from a range of mammalian species. The majority of members described to date are dramatically induced during the acute-phase response, suggesting an important short-term beneficial role in the response to tissue injury and inflammation. However, important disease associations have also been proposed for certain SAAs during chronic inflammation. The nomenclature of many of the superfamily members has been the result of comparisons with previously reported sequences implying disease association and/or functional relatedness between such members. The evolutionary relationships of the SAA superfamily members have been investigated by comparisons at both the amino acid and the nucleotide level. The results indicate that all members of the superfamily within a species have been undergoing concerted evolution. This has important implications in ascribing functions and disease associations to individual SAA superfamily members and indicates that designations should not be based on the extent of amino acid identity alone but should be made only following direct experimental observation of the proteins themselves. 相似文献
65.
66.
M. E. Fitzpatrick M. T. Hutchings J. E. King D. M. Knowles P. J. Withers 《Metallurgical and Materials Transactions A》1995,26(12):3191-3198
The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy
have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment
temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field
into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens
cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing.
Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress
field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the
specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated.
formerly Research Student, Department of Materials Science and Metallurgy, University of Cambridge
formerly Lecturer, Department of Materials Science and Metallurgy, University of Cambridge
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
67.
68.
Very high-order microring resonator filters for WDM applications 总被引:6,自引:0,他引:6
B.E. Little S.T. Chu P.P. Absil J.V. Hryniewicz F.G. Johnson F. Seiferth D. Gill V. Van O. King M. Trakalo 《Photonics Technology Letters, IEEE》2004,16(10):2263-2265
High-order microring resonators having from 1 to 11 coupled cavities are demonstrated. These filters exhibit low loss, flat tops, and out-of-band rejection ratios that can exceed 80 dB. They achieve performance that is suitable for commercial applications. 相似文献
69.
70.
A (time-dependent) model for an electrochemical cell, comprising a dilute binary electrolytic solution between two flat electrodes,
is formulated. The method of matched asymptotic expansions (taking the ratio of the Debye length to the cell width as the
small asymptotic parameter) is used to derive simplified models of the cell in two distinguished limits and to systematically
derive the Butler–Volmer boundary conditions. The first limit corresponds to a diffusion-limited reaction and the second to
a capacitance-limited reaction. Additionally, for sufficiently small current flow/large diffusion, a simplified (lumped-parameter)
model is derived which describes the long-time behaviour of the cell as the electrolyte is depleted. The limitations of the
dilute model are identified, namely that for sufficiently large half-electrode potentials it predicts unfeasibly large concentrations
of the ion species in the immediate vicinity of the electrodes. This motivates the formulation of a second model, for a concentrated
electrolyte. Matched asymptotic analyses of this new model are conducted, in distinguished limits corresponding to a diffusion-limited
reaction and a capacitance-limited reaction. These lead to simplified models in both of which a system of PDEs, in the outer
region (the bulk of the electrolyte), matches to systems of ODEs, in inner regions about the electrodes. Example (steady-state)
numerical solutions of the inner equations are presented. 相似文献