全文获取类型
收费全文 | 797篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 192篇 |
金属工艺 | 17篇 |
机械仪表 | 24篇 |
建筑科学 | 15篇 |
能源动力 | 67篇 |
轻工业 | 27篇 |
水利工程 | 12篇 |
无线电 | 97篇 |
一般工业技术 | 189篇 |
冶金工业 | 67篇 |
原子能技术 | 3篇 |
自动化技术 | 112篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 32篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 48篇 |
2017年 | 24篇 |
2016年 | 47篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 56篇 |
2012年 | 42篇 |
2011年 | 46篇 |
2010年 | 29篇 |
2009年 | 46篇 |
2008年 | 60篇 |
2007年 | 40篇 |
2006年 | 20篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 17篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 16篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有828条查询结果,搜索用时 31 毫秒
81.
S. Sathiya Naarayan D.V.T.G. Pavan Kumar Satish Chandra 《Engineering Failure Analysis》2009,16(7):2255-2273
Riveted lap joints are being used widely in civil aircraft structures. Conventional design procedures assume that the joint can be designed as if all rivets carry load equally. As found in literature associated with fatigue and fracture, forensic studies on structural failures, this assumption is not entirely valid. In this paper, the regulatory codes for civil aircraft as applicable to riveted joints in the form of FAR 25 regulations are briefly reviewed. The regulatory code discusses safety factors in an implied way, but has little specific recommendations for riveted joints. However, studies on the failures of specific aircraft illustrated in this paper add to the argument that both static strength and life are affected by the initial design procedures for the riveted joints. In this paper, finite element models for metal–metal, composite–metal, composite–composite lap joints are studied. A three row lap joint used in commercial aircraft and which was part of failure studies is also examined. Unequal rivet loads and in cases, nearly 50% more than conventional design has been seen in linear finite element analysis. Elasto-plastic analysis using rivet flexibility shows re-distribution of loads. Based on these observations, the effect of rivet loads on life estimation including the use of concepts such as by-pass stresses is discussed. These results have implications for static strength at ultimate load, damage tolerance and fail safety and are discussed in this paper. Next, in a composite–composite lap joint, the influence of ply-angle on the rivet loads is studied. Also, a composite–metal lap joint is studied for the rivet load distribution and life estimation. It is found that the load shared by the rivet rows in a composite–metal lap joint are not symmetric and therefore are more susceptible to cracking and subsequent failure as the unequal distribution can cause some of the rivet loads to be high. In conclusion, the issue of fail safe and damage tolerant design of civil aircraft structures with riveted joints are addressed, especially the implication of unequal load distribution on the failures of such joints and it is suggested that these unequal rivet load distributions be catered for at the early design stage itself via finite element analysis and the possibility of an over-arching safety factor could be considered that incorporates both ultimate load and damage tolerance conditions. 相似文献
82.
Seong Jin Park Pavan Suri Eugene Olevsky Randall M. German 《Journal of the American Ceramic Society》2009,92(7):1410-1413
The classical master sintering curve (MSC) is derived from empirical sintering model and is applicable over a range of heating rates and temperatures. For simplicity, the MSC approach was modified by assuming one dominant densification mechanism to evaluate and predict densification response. However, the concept of MSC can be extended well beyond the original formulation or the subsequent simplifications. To this effect, generalized formulations are proposed based on several constitutive equations including both grain growth and densification. These formulations can be used very effectively to obtain material properties that in turn can be used in finite-element method to improve the accuracy of the simulations. 相似文献
83.
Sean X. Liu Pavan Mamidipally Ming Peng Leland M. Vane 《Chemical Engineering Communications》2005,192(10):1386-1404
Concentration polarization is a phenomenon that is inherent in all membrane separation processes, which is difficult if not impossible to measure experimentally. Concentration polarization in a pervaporation module causes flux decline and is therefore an important issue in predicting the performance of the membrane unit for evaluation and optimization. Short-form (small L/D ratio) membrane configurations, commonly used for membrane evaluations or certain material separations, compound the complexity of process modeling that addresses concentration polarization since a substantial portion of the membrane flow channel would be considered as an “entrance region” based on the flow profile that is not fully developed. This article employed the classic boundary layer theory, combined with mass transfer phenomena in a pervaporation process that is used in volatile organic compound (VOC) removal from contaminated water sources, to theoretically analyze the concentration polarization severity in the entrance region of a flat sheet membrane module. 相似文献
84.
Larcher L. Pavan P. Pietri S. Albani L. Marmiroli A. 《Electron Devices, IEEE Transactions on》2002,49(2):301-307
This paper presents for the first time a new compact SPICE model of floating gate nonvolatile memory cells capable to reproduce effectively the complete DC electrical behavior in every bias conditions. This model features many advantages compared to previous ones: it is simple and easy to implement since it uses SPICE circuit elements, is scalable, and its computational time is not excessive. It is based on a new procedure that calculates the floating gate voltage without using fixed capacitive coupling coefficients, thus improving the floating gate voltage estimate that is fundamental for the correct modeling of cell operations. Moreover, this model requires only the usual parameters adopted for SPICE-like models of MOS transistors plus the floating gate-control gate capacitance, making it very attractive to industry as the same parameter extraction procedure used for MOS transistors can be directly applied. The model we propose has been validated on E2PROM and flash memory cells manufactured in existing technology (0.35 μm and 0.25 μm) by STMicroelectronics 相似文献
85.
Regression Model for Daily Maximum Stream Temperature 总被引:3,自引:0,他引:3
David W. Neumann Balaji Rajagopalan Edith A. Zagona 《Canadian Metallurgical Quarterly》2003,129(7):667-674
An empirical model is developed to predict daily maximum stream temperatures for the summer period. The model is created using a stepwise linear regression procedure to select significant predictors. The predictive model includes a prediction confidence interval to quantify the uncertainty. The methodology is applied to the Truckee River in California and Nevada. The stepwise procedure selects daily maximum air temperature and average daily flow as the variables to predict maximum daily stream temperature at Reno, Nev. The model is shown to work in a predictive mode by validation using three years of historical data. Using the uncertainty quantification, the amount of required additional flow to meet a target stream temperature with a desired level of confidence is determined. 相似文献
86.
Rao Balaji M.; Girvin Andrew T.; Ciardelli Thomas; Lauffenburger Douglas A.; Wittrup K.Dane 《Protein engineering, design & selection : PEDS》2003,16(12):1081-1087
Stimulation of T-cells by IL-2 has been exploited for treatmentof metastatic renal carcinoma and melanoma. However, a narrowtherapeutic window delimited by negligible stimulation of T-cellsat low picomolar concentrations and undesirable stimulationof NK cells at nanomolar concentrations hampers IL-2-based therapies.We hypothesized that increasing the affinity of IL-2 for IL-2R 相似文献
87.
John L. Johnson Lye King Tan Pavan Suri Randall M. German 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(10):30-34
Powder injection molding can be used to fabricate bi-material components that provide unique functionality such as a combination
of toughness and wear resistance. Successful processing of these components requires minimization of internal stresses during
sintering. In this article, the stresses generated during co-sintering of concentric rings are analyzed, compared to the materials’
strengths, and correlated with defects. The results provide guidelines for determining the compatibility of various materials
and the effect of component geometry.
For more information, contact John L. Johnson, AMTellect, 302 South Burrowes Street, State College, PA 16801; (814) 861-8090;
fax (814) 861-8003; e-mail john@amtellect.com. 相似文献
88.
JZ Gu ED Carstea C Cummings JA Morris SK Loftus D Zhang KG Coleman AM Cooney ME Comly L Fandino C Roff DA Tagle WJ Pavan PG Pentchev MA Rosenfeld 《Canadian Metallurgical Quarterly》1997,94(14):7378-7383
Niemann-Pick disease type C (NP-C) is an autosomal recessive lipidosis linked to chromosome 18q11-12, characterized by lysosomal accumulation of unesterified cholesterol and delayed induction of cholesterol-mediated homeostatic responses. This cellular phenotype is identifiable cytologically by filipin staining and biochemically by measurement of low-density lipoprotein-derived cholesterol esterification. The mutant Chinese hamster ovary cell line (CT60), which displays the NP-C cellular phenotype, was used as the recipient for a complementation assay after somatic cell fusions with normal and NP-C murine cells suggested that this Chinese hamster ovary cell line carries an alteration(s) in the hamster homolog(s) of NP-C. To narrow rapidly the candidate interval for NP-C, three overlapping yeast artificial chromosomes (YACs) spanning the 1 centimorgan human NP-C interval were introduced stably into CT60 cells and analyzed for correction of the cellular phenotype. Only YAC 911D5 complemented the NP-C phenotype, as evidenced by cytological and biochemical analyses, whereas no complementation was obtained from the other two YACs within the interval or from a YAC derived from chromosome 7. Fluorescent in situ hybridization indicated that YAC 911D5 was integrated at a single site per CT60 genome. These data substantially narrow the NP-C critical interval and should greatly simplify the identification of the gene responsible in mouse and man. This is the first demonstration of YAC complementation as a valuable adjunct strategy for positional cloning of a human gene. 相似文献
89.
A scale modeled discus data buoy was tested for its motion characteristics under the action of wave groups of different frequencies in a wave tank. The wave groups were theoretically simulated based on the methodology of Xu et al., (1993, Statistical simulation of wave groups, Applied Ocean Research, 15, 217–226) and then converted to paddle displacement signals to drive the wave maker. The motion responses of the buoy model were measured using potentiometers as well as with a non-contact motion tracking camera system. The details of the model, instrumentation, testing conditions and the analysis are presented. The displacement and wave elevation time histories were analysed through statistical, envelope, wavelet transform and phase-time approaches to detect the wave groupiness. The effect of groupiness parameters on the surge, heave and pitch motions of the buoy are detailed in this paper. 相似文献
90.
Kaushik Biswas Sathravada Balaji Debarati Ghosh Annapurna Kalyandurg 《International Journal of Applied Glass Science》2017,8(2):204-215
In this work, effect of glass composition as well as ceramization on visible and near-infrared (NIR) luminescence properties along with their decay dynamics of Er3+ ions has been compared considering two different oxyfluoride glasses yielding BaF2 and BaGdF5 nanocrystals. Both the glass systems have exhibited an intense normal and upconversion green emission under ultraviolet (378 nm) and NIR (978 nm) excitations, respectively. A remarkable enhancement of these emission intensities is observed for gadolinium-(Gd) containing glasses. Interestingly, NIR fluorescence intensity from Er3+ ions at 1540 nm has showed marginal decrease in gadolinium-containing glass which is attributed to occurrence of strong excited-state absorption (ESA) due to higher fluorine content ensuing an augmentation of upconversion green emission with a concomitant decrease in NIR emission. The quadratic dependence of upconversion green emission intensity on its pump power for all the samples revealed biphotonic absorption process from ground-state 4I15/2 to the excited-state 4I11/2 followed by ESA of second photon to the 4F7/2 level. The intense green upconversion emission as well as enhanced NIR fluorescence lifetimes indicate the suitability of these glass/glass ceramics for upconversion lasers and amplification in the third telecom window. 相似文献