全文获取类型
收费全文 | 1543篇 |
免费 | 46篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 194篇 |
金属工艺 | 9篇 |
机械仪表 | 18篇 |
建筑科学 | 32篇 |
能源动力 | 24篇 |
轻工业 | 67篇 |
水利工程 | 8篇 |
石油天然气 | 16篇 |
无线电 | 140篇 |
一般工业技术 | 222篇 |
冶金工业 | 675篇 |
原子能技术 | 46篇 |
自动化技术 | 126篇 |
出版年
2022年 | 13篇 |
2021年 | 21篇 |
2019年 | 18篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 27篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 42篇 |
2010年 | 41篇 |
2009年 | 34篇 |
2008年 | 44篇 |
2007年 | 35篇 |
2006年 | 36篇 |
2005年 | 28篇 |
2004年 | 20篇 |
2003年 | 25篇 |
2002年 | 37篇 |
2001年 | 16篇 |
2000年 | 26篇 |
1999年 | 30篇 |
1998年 | 146篇 |
1997年 | 105篇 |
1996年 | 74篇 |
1995年 | 46篇 |
1994年 | 55篇 |
1993年 | 39篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 29篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 32篇 |
1976年 | 44篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1972年 | 15篇 |
1970年 | 11篇 |
排序方式: 共有1590条查询结果,搜索用时 12 毫秒
71.
72.
73.
Stachowski Alicia A.; Kaplan Seth A.; Waller Mary J. 《Canadian Metallurgical Quarterly》2009,94(6):1536
Organizations increasingly rely on teams to respond to crises. While research on team effectiveness during nonroutine events is growing, naturalistic studies examining team behaviors during crises are relatively scarce. Furthermore, the relevant literature offers competing theoretical rationales concerning effective team response to crises. In this article, the authors investigate whether high- versus average-performing teams can be distinguished on the basis of the number and complexity of their interaction patterns. Using behavioral observation methodology, the authors coded the discrete verbal and nonverbal behaviors of 14 nuclear power plant control room crews as they responded to a simulated crisis. Pattern detection software revealed systematic differences among crews in their patterns of interaction. Mean comparisons and discriminant function analysis indicated that higher performing crews exhibited fewer, shorter, and less complex interaction patterns. These results illustrate the limitations of standardized response patterns and highlight the importance of team adaptability. Implications for future research and for team training are included. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Martin L. Kaplan 《Polymer Engineering and Science》1991,31(10):689-698
The kinetics of the sorption characteristics of seven different solvents has been measured at 22°, 40°, and 50°C in several cured epoxies. In addition to water, the organic solvents methanol, acetone, isopropanol, ethyl acetate, 1,2-dichloroethane, and toluene were examined. The resin, diglycidyl ether of bisphenol A, was cured with four hardeners, each one resulting in a different epoxy material. The curing agents include triethylenetetramine, nadic methylanhydride, dicyandiamide and m-phenylenediamine, all commonly used substances. Data were analyzed using Fick's diffusion equation. In general, three types of behavior were observed, Fickian diffusion, Case II diffusion, and anomalous diffusion. Fickian or anomalous behavior dominated at all temperatures. Diffusion was both material and solvent dependent. The anomalous nature of isopropanol was noted. Although chemically similar to methanol and about the same size, as acetone, isopropanol is sorbed at a much lower rate. A combination of physical and chemical effects appeared to be responsible for the observations in the epoxies. Diffusion coefficients were estimated for all penetrants and were mostly in the range of 10?9 to 10?11 cm2/s. Where appropriate, apparent activation energies for diffusion were calculated from the kinetic curves. 相似文献
75.
Yaniv Ganor Doron Shilo Nadege Zarrouati Richard D. James 《Sensors and actuators. A, Physical》2009,150(2):277-279
A new method for propulsion using a Ni2MnGa ferromagnetic shape memory flapper is introduced. We optically examine the magnetic field induced strain of pure shear by means of a state of the art generator that provides alternating magnetic fields of 7000 Oe at frequencies of up to 100 Hz. Preliminary measurements show local shear deformation of about 5%, which open new frontiers in propulsion mechanisms. 相似文献
76.
Changes in chemical constituents during the maturation and ripening of two commercially important pomegranate accessions 总被引:2,自引:0,他引:2
Elinor Shwartz Ira Glazer Irit Bar-Ya’akov Ifat Matityahu Igal Bar-Ilan Doron Holland Rachel Amir 《Food chemistry》2009
Pomegranate juice is well known for its health beneficial compounds. This study was undertaken to investigate changes in the major chemical composition in arils and peels during fruit maturation in two Israeli commercial accessions, ‘Wonderful’ and ‘Rosh-Hapered.’ In both accessions, the levels of total phenolic, antioxidant activity and hydrolysable tannins were reduced in the peels during maturation, while the anthocyanin level increased. The results show that the sugar content in the aril juice increased in both accessions while the levels of acidity and of citric acid decreased. However, these two accessions differed in other parameters in the aril juice, i.e., while the antioxidant and total phenolic contents significantly decreased in ‘Rosh-Hapered’, these changes were not observed in ‘Wonderful’. The anthocyanin level, however, increased in ‘Wonderful’ but did not change in ‘Rosh-Hapered.’ This knowledge could help establish the optimum harvest date ensuring the maximum nutritional properties of pomegranates. 相似文献
77.
Xu C Miller EJ Zhang S Li HP Ho YF Schwehr KA Kaplan DI Otosaka S Roberts KA Brinkmeyer R Yeager CM Santschi PH 《Environmental science & technology》2011,45(23):9975-9983
In order to investigate the distributions and speciation of (129)I (and (127)I) in a contaminated F-Area groundwater plume of the Savannah River Site that cannot be explained by simple transport models, soil resuspension experiments simulating surface runoff or stormflow and erosion events were conducted. Results showed that 72-77% of the newly introduced I(-) or IO(3)(-) were irreversibly sequestered into the organic-rich riparian soil, while the rest was transformed by the soil into colloidal and truly dissolved organo-iodine, resulting in (129)I remobilization from the soil greatly exceeding the 1 pCi/L drinking water permit. This contradicts the conventional view that only considers I(-) or IO(3)(-) as the mobile forms. Laboratory iodination experiments indicate that iodine likely covalently binds to aromatic structures of the soil organic matter (SOM). Under very acidic conditions, abiotic iodination of SOM was predominant, whereas under less acidic conditions (pH ≥5), microbial enzymatically assisted iodination of SOM was predominant. The organic-rich soil in the vadose zone of F-Area thus acts primarily as a "sink," but may also behave as a potentially important vector for mobile radioiodine in an on-off carrying mechanism. Generally the riparian zone provides as a natural attenuation zone that greatly reduces radioiodine release. 相似文献
78.
79.
B. Z. Kaplan D. Yardeni 《International Journal of Circuit Theory and Applications》1991,19(3):309-315
The paper treats the development of a non-linearly stabilized oscillator model for generating four sine waves in quadrature. the treatment appears important although quadrature signals can also be generated by a well-known twophase oscillator. the latter generates only two of the signals needed in a four-phase system, but the rest of the phases signals could nevertheless be generated by simply inverting the two existing signals. For certain applications, however, the generation of all four signals in a completely cyclic and symmetrical manner is preferable. This method of generation is dealt with in the present paper. A previous paper of ours has treated a system of a similar objective. the present system, however, is much simpler. This simplicity is manifested not only through the mathematical representation but also when an electronic realization of the system is considered. the present model realization appears considerably less expensive, since the number of necessarily non-linear operations is much reduced. This reduction is due to the fact that the non-linearly stabilized model imbeds a ‘partially conservative’ linear oscillator. the concept of ‘partial conservativity’ has been introduced recently. the present work treats comprehensively the advantages that are gained by imbedding a partially conservative oscillator. 相似文献
80.
R Arens B Wright J Elliott H Zhao PP Wang LW Brown T Namey P Kaplan 《Canadian Metallurgical Quarterly》1998,133(5):670-674
Difficulty differentiating physiologic genu varum from early Blount's disease persists. Drennan's metaphyseal-diaphyseal (MD) angle remains the most consistently valuable radiographic parameter despite measurement error. Clinical risk factors also should be considered. All patients receiving orthoses for genu varum since 1985 were reviewed. The focus of the study was those patients with an MD angle of >16 degrees or between 9 and 16 degrees with a clinical risk factor for progression. Risk factors considered were ligamentous instability, obesity, asymmetry, and being female, black, or Hispanic. Thirty-eight patients with 60 tibiae were included. The success rate was 90%. Risk factors for failure (six cases) were instability, obesity, and delayed bracing. In cases with MD angles >16 degrees, the success rate was 86%. The results of orthotic treatment, restricted to patients meeting the stated parameters, represent improvement on the reported natural history. 相似文献