全文获取类型
收费全文 | 570篇 |
免费 | 18篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 102篇 |
金属工艺 | 8篇 |
机械仪表 | 14篇 |
建筑科学 | 51篇 |
矿业工程 | 3篇 |
能源动力 | 20篇 |
轻工业 | 48篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 50篇 |
一般工业技术 | 129篇 |
冶金工业 | 77篇 |
原子能技术 | 2篇 |
自动化技术 | 73篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 32篇 |
2012年 | 30篇 |
2011年 | 49篇 |
2010年 | 33篇 |
2009年 | 42篇 |
2008年 | 45篇 |
2007年 | 36篇 |
2006年 | 32篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有588条查询结果,搜索用时 156 毫秒
51.
52.
Stein Catherine H.; Abraham Kristen M.; Bonar Erin E.; Leith Jaclyn E.; Kraus Shane W.; Hamill Alexis C.; Gumber Shinakee; Hoffmann Erica; Fogo Wendy R. 《Canadian Metallurgical Quarterly》2011,25(3):449
The present intergenerational study examined the perceived impact of the recent U.S. economic crisis on a sample of 68 young adult–parent dyads. The relative contribution of perceived economic pressure, reports of adult child–parent relationship quality, and concerns about the economic future in accounting for variation in self-reports of psychological distress for adult children and their middle-aged parents were examined. Parents' concerns about their children's economic future accounted for variation in their reports of anxiety and depressed mood above and beyond that of perceived economic pressures and their views of the parent–child relationship. In contrast, for young adults, reports of personal economic pressure were generally related to self-reported anxiety and depressed mood. Implications of findings for research and practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
53.
Effect of the Interfacial Transition Zone on the Conductivity of Portland Cement Mortars 总被引:3,自引:0,他引:3
John D. Shane Thomas O. Mason Hamlin M. Jennings Edward J. Garboczi Dale P. Bentz 《Journal of the American Ceramic Society》2000,83(5):1137-1144
The electrical conductivity of portland cement mortars was determined experimentally as a function of the volume fraction of sand and the degree of hydration. The results were analyzed using theoretical models that represent the mortars as three-phase, interactive composites. The three phases are the matrix paste, the aggregate, and the thin interfacial transition zone between the two. The microstructure and properties of the conductive phases (the transition zone and the matrix paste) were determined by a micrometer-scale microstructural model, and were used in conjunction with random-walk algorithms and differential-effective medium theory to determine the overall mortar conductivities. The presence of the transition zone was not found to significantly affect the global electrical conductivity of the mortar. However, there were significant differences in conductivity between the transition zone and matrix pastes when examined on a local level. These differences were found to vary with hydration and were most significant when the degree of hydration was between 0.5 and 0.8. 相似文献
54.
Bergmans and Cover identified the capacity region of the Gaussian degraded broadcast channel, where different receivers observe the transmitted signal with different signal-to-noise ratios. This letter presents a superposition turbo-coding scheme that performs within 1 dB of the capacity region boundary of the degraded broadcast channel at a bit-error rate of 10/sup -5/. 相似文献
55.
A method is proposed for finding the best stable and invertible approximations for an autoregressive moving average (ARMA) system, relative to a general quadratic metric in the coefficient space. Mathematically, the problem is equivalent to projecting the regression and moving average vectors of the system onto the set S of coefficients of monic Schur polynomials. The geometry of S is too complex to allow the problem to be approached directly in the ARMA coefficient space. A solution is obtained by constrained steepest descent in the hypercube of reflection coefficients, which is homomorphic to S 相似文献
56.
57.
Mathematical methods for the analysis of color scanning filters 总被引:1,自引:0,他引:1
The problem of the sensitivity analysis of color scanning filters is addressed in this paper. The second differential of the mean square DeltaE(ab) error provides a means of calculating the sensitivity of the mean square DeltaE(ab) error to filter fabrication errors. Tolerances on the allowable change in the mean square DeltaE(ab) error are used to define bounds on the filter fabrication errors at all wavelengths and at single wavelengths. 相似文献
58.
59.
Shane P. Windsor Richard J. Bomphrey Graham K. Taylor 《Journal of the Royal Society Interface》2014,11(91)
Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight. 相似文献
60.
Roth MJ Plymire DA Chang AN Kim J Maresh EM Larson SE Patrie SM 《Analytical chemistry》2011,83(24):9586-9592
The compatibility of superficially porous (SP) resin for label-free intact protein analysis with online capillary LC/MS is demonstrated to give improved chromatographic resolution, sensitivity, and reproducibility. The robustness of the platform was measured against several samples of varying complexity and sample loading amount. The results indicate that capillary SP columns provide high loading capacities and that ~6 s chromatographic peak widths are typical for standard proteins in simple mixtures and proteins isolated from cell and tissue lysates. Subfemtomole detection limits for standard proteins were consistently observed, with the lowest levels at 12 amol for ubiquitin. The analysis of total heart homogenates shows that capillary SP columns provide theoretical peak capacity of 106 protein forms with 30 min total analysis time and enabled detection of proteins from complex mixtures with a single high-resolution scan. The SPLC/MS platform also detected 343 protein forms from two HeLa acid extract replicate analyses that consumed 5 × 10(4) cells and 30 min analysis time, each. Comparison of all the species observed in each HeLa replicate showed 90% overlap (309 forms) with a Pearson correlation coefficient of 89.9% for the common forms observed in the replicates. Efficient acid extract of 1 × 10(4) HeLa cells allowed reproducible detection of common modification states and members from all five of the histone families and demonstrated that capillary SPLC/MS supports reproducible label-free profiling of histones in <15 min total analysis time. The data presented demonstrate that a capillary LC/MS platform utilizing superficially porous stationary phase and a LTQ-Orbitrap FT-MS is fast, sensitive, and reproducible for intact protein profiling from small tissue and cell amounts. 相似文献