全文获取类型
收费全文 | 710篇 |
免费 | 0篇 |
专业分类
化学工业 | 9篇 |
金属工艺 | 1篇 |
建筑科学 | 6篇 |
能源动力 | 1篇 |
轻工业 | 3篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 7篇 |
一般工业技术 | 3篇 |
冶金工业 | 660篇 |
自动化技术 | 18篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 26篇 |
1998年 | 206篇 |
1997年 | 120篇 |
1996年 | 78篇 |
1995年 | 48篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 14篇 |
1976年 | 33篇 |
1975年 | 2篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有710条查询结果,搜索用时 15 毫秒
61.
LJ Seidman KB Benedict J Biederman JH Bernstein K Seiverd S Milberger D Norman E Mick SV Faraone 《Canadian Metallurgical Quarterly》1995,36(8):1459-1473
This study evaluates the performance of boys with Attention Deficit Hyperactivity Disorder (ADHD) on the Rey-Osterrieth Complex Figure (ROCF) taking into consideration familiality and comorbid psychiatric and learning disorders (LD). Sixty-five children with ADHD performed at developmentally lower levels of Copy Organization and Recall Style than did 45 controls. ADHD children with LD scored significantly lower on Copy Organization than did ADHD children without LD, whereas psychiatric comorbidity and familiality had no effect. These results suggest that a developmental analysis of the ROCF identifies organizational difficulties associated with ADHD and that these impairments cannot simply be attributed to comorbidities associated with ADHD. 相似文献
62.
Q Li W Wang KB Berst A Claiborne L Hasvold K Raye M Tufano A Nilius LL Shen R Flamm J Alder K Marsh D Crowell DT Chu JJ Plattner 《Canadian Metallurgical Quarterly》1998,8(15):1953-1958
The 8-position side chain of 2-pyridones is believed to be involved in the binding with bacterial DNA gyrase to form the ternary complex, making them very important for the activity of 2-pyridones. A series of 2-pyridones having fluoro-substituted amines at the 8-position has been synthesized and their antibacterial activities and parmacokinetic properties are reported. 相似文献
63.
Behavioral geneticists and evolutionary psychologists have generally pursued human behavioral analyses with little theoretical or methodological exchange. However, significant benefits might accrue from increased communication between these disciplines. The primary goals of this article are (1) to identify meaningful junctures between behavioral genetics and evolutionary psychology, (2) to describe behavioral genetic research designs and their applications to evolutionary analyses, and (3) to reassess current personality research in light of behavioral genetic and evolutionary concepts and techniques. The five-factor model of personality is conceptualized as subsuming variation in normative species-typical systems with adaptive functions in the human environment of evolutionary adaptation. Considered as universal evolved mechanisms, personality systems are often seen in dynamic conflict within individuals and as highly compartmentalized in their functioning between settings. However, genetically influenced individual differences in personality may also be understood within an evolutionary framework. Studies of the heritability of personality traits indicate broad-sense heritabilities in the 0.40-0.50 range with evidence of substantial nonadditive genetic variation and nonshared environmental influences. Evidence indicates that evolutionary theory (e.g., inclusive fitness theory) predicts patterns of social interaction (e.g., cooperation and bereavement) in relatives. Furthermore, variation in personality may constitute a range of viable strategies matching the opportunities available in the complex niche environment of human societies. Within this wide range of viable strategies, personality variation functions as a resource environment for individuals in the sense that personality variation is evaluated according to the interests of the evaluator (e.g., friendships, coalitions, or mate choice). 相似文献
64.
65.
66.
BACKGROUND: The human tympanic membrane has reasonably good sound transmission properties and withstands high static pressure loads. Destruction of the tympanic membrane resulting from middle ear diseases or trauma may be repaired by different types of grafts. Middle ear surgery mostly uses autologous temporal fascia, cartilage, or cartilage perichondrium transplants which differ in their acoustical characteristics and mechanical strength. METHODS: We have investigated the acoustical and mechanical properties of these materials and compared them with human tympanic membranes by constructing an ear canal-tympanic membrane model. Fresh human tympanic membrane, fascia, perichondrium, and cartilage preparations were exposed to static pressures up to 4 kPa and white noise sound pressure levels of 70 dB. The vibrational amplitudes and displacements due to static pressure were measured by laser Doppler vibrometry. RESULTS: The temporal fascia and perichondrium show similar amplitude frequency responses compared to the tympanic membrane for dynamic excitation. The displacement of these materials at static pressures above 4 kPa indicates a higher compliance than the tympanic membrane. The acoustical and mechanical properties of cartilage transplants are determined by the thickness of the slices. Thin cartilage slices are less stable although their frequency response is comparable to the intact tympanic membrane. Layer thickness above 500 microns result in a decrease of vibration amplitudes. CONCLUSIONS: Cartilage is an excellent transplant material which provides a better prognosis than soft materials in cases of ventilation disorders with long-term middle ear pressure problems. Large cartilage slice transplants should not exceed layer thickness of 500 microns in order to minimize transmission loss. 相似文献
67.
KB Arbogast KL Thibault BS Pinheiro KI Winey SS Margulies 《Canadian Metallurgical Quarterly》1997,30(7):757-759
Accurate mechanical property data obtained at large shear deformations and high frequencies are a fundamental component of realistic numerical simulations of soft tissue injury. Although many commercial systems exist for testing shear properties of viscoelastic materials with properties similar to soft biological tissue, none are capable of determining properties at high loading rates necessary for modeling soft tissue injury. Previous custom shear testing systems, though capable of high-frequency loading, indirectly measure tissue properties by using analytical corrections for inertial effects. To address these limitations, a new custom designed oscillatory shear testing apparatus (STA) capable of testing soft biological tissues in simple shear has been constructed and validated. Through a proper selection of sample thickness, direct measurement of material properties at high frequencies is achieved mechanically without analytical inertial adjustments. The complex shear modulus of three mixtures of silicone gel with viscoelastic properties in a range similar to soft biological tissue was characterized in the STA over a dynamic frequency range of 20-200 Hz and validated with a commercially available solids rheometer. The frequency-dependent complex shear modulus measurements of the STA were within 10% of the rheometer measurements for all mixtures over the entire frequency range tested. The STA represents substantive improvement over current shear testing methods by providing direct measurement of the shear behavior of soft viscoelastic material at high frequencies. Mechanical property data gained from this device will provide a more realistic basis for numerical simulations of biological structures. 相似文献
68.
69.
KB Kahen 《Canadian Metallurgical Quarterly》1991,43(14):11745-11753
70.
In recent years considerable attention has been given to the effects of universal, first-dollar coverage for health care services as provided under Canada's health care system. However, no consideration has been given to the stability of these effects through periods of changing economic climate. In this paper we consider the extent to which the achievements of the Canadian approach to health care funding have been maintained in the presence of increasing attention to cost containment. Multivariate analyses are used to (a) explain variations in utilization of family physician services among the population and (b) explore the relationship between utilization and need for periods of differing economic circumstances. We observe that the relative importance of differences in need in explaining variations in use among the population was less in the period when cost containment was of greater concern. These findings indicate that policymakers cannot assume that removing financial barriers to access to service, although important in achieving a more equitable distribution of service utilization, may be sufficient to sustain such distributions during time of constraint. 相似文献