全文获取类型
收费全文 | 371613篇 |
免费 | 4250篇 |
国内免费 | 2445篇 |
专业分类
电工技术 | 7423篇 |
技术理论 | 8篇 |
综合类 | 2314篇 |
化学工业 | 50909篇 |
金属工艺 | 14122篇 |
机械仪表 | 11517篇 |
建筑科学 | 10636篇 |
矿业工程 | 1518篇 |
能源动力 | 10571篇 |
轻工业 | 35512篇 |
水利工程 | 3308篇 |
石油天然气 | 4651篇 |
武器工业 | 185篇 |
无线电 | 49495篇 |
一般工业技术 | 66892篇 |
冶金工业 | 70990篇 |
原子能技术 | 5298篇 |
自动化技术 | 32959篇 |
出版年
2022年 | 2232篇 |
2021年 | 3634篇 |
2020年 | 3038篇 |
2019年 | 3310篇 |
2018年 | 4256篇 |
2017年 | 4343篇 |
2016年 | 4784篇 |
2015年 | 3979篇 |
2014年 | 6212篇 |
2013年 | 17286篇 |
2012年 | 10312篇 |
2011年 | 14397篇 |
2010年 | 11497篇 |
2009年 | 12797篇 |
2008年 | 13440篇 |
2007年 | 13322篇 |
2006年 | 12466篇 |
2005年 | 11318篇 |
2004年 | 10599篇 |
2003年 | 10384篇 |
2002年 | 9768篇 |
2001年 | 10334篇 |
2000年 | 9250篇 |
1999年 | 10203篇 |
1998年 | 25466篇 |
1997年 | 17389篇 |
1996年 | 13285篇 |
1995年 | 9715篇 |
1994年 | 8500篇 |
1993年 | 8235篇 |
1992年 | 5560篇 |
1991年 | 5278篇 |
1990年 | 4938篇 |
1989年 | 4622篇 |
1988年 | 4359篇 |
1987年 | 3397篇 |
1986年 | 3312篇 |
1985年 | 3969篇 |
1984年 | 3527篇 |
1983年 | 3207篇 |
1982年 | 2964篇 |
1981年 | 2988篇 |
1980年 | 2710篇 |
1979年 | 2478篇 |
1978年 | 2242篇 |
1977年 | 2657篇 |
1976年 | 3619篇 |
1975年 | 1852篇 |
1974年 | 1736篇 |
1973年 | 1783篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes. 相似文献
92.
A temperature sensor using a fiber-optic Fabry-Perot interferometer is described. A pseudo-heterodyne detection scheme is adopted to read the light phase difference in the Fabry-Perot interference output. A higher harmonic components comparison method is used to stabilize the system and to increase detection linearity. This system realizes not only highly sensitive temperature sensing with good linearity and minimal adjusting error, but also application to the sensing of other physical quantities such as vibrations. Additionally, the signal-to-noise ratio and distortion of the detected signal are investigated as functions of fiber end reflectivity. These results will be useful in designing a high performance fiber-optic Fabry-Perot thermometer. 相似文献
93.
This paper discusses another generalization of the direct Routh table truncation method for interval systems. It is shown that the existing generalization of the direct Routh table truncation fails to produce a stable system, in contradiction to the equivalent result for fixed-coefficients systems. The present method guarantees a stable reduced order model for interval systems as well. 相似文献
94.
There will always be a premium on innovation and original approaches to old problems. Engineers and designers are constantly urged to think outside the box. In space shuttle technician Arlene S. Reese's case, she decided to think outside the world of traditional, 2D drafting. Working under tough deadline pressures for a shuttle lighting installation project, Reese and her design team decided to blend digital photographs and 3D assemblies to show other contractors precisely where and how the job should be built. The result was a faster, more effective method for planning electrical projects that has earned awards for her team and continues to produce benefits for the National Aeronautics and Space Administration (NASA). Reese and the managers at NASA say the design method can apply to many architectural and engineering disciplines. 相似文献
95.
96.
A survey of the state of SQA in Japan finds that the situation is much like, but slightly different than, that in the US. 相似文献
97.
The exfiltration of wastewater from sewer systems in urban areas causes a deterioration of soil and possibly groundwater quality. Beside the simulation of transport and degradation processes in the unsaturated zone and in the aquifer the analysis of the potential impact requires the estimation of quantity and temporal variation of wastewater exfiltration. Exfiltration can be assessed by the application of a leakage model. The hydrological approach was originally developed to simulate the interactions between the groundwater and surface water, it was adapted to allow for modelling of interactions between groundwater and sewer system. In order to approximate the exfiltration specific model parameters infiltration specific parameters were used as a basis. Scenario analysis of the exfiltration in the City of Dresden from 1997 to 1999 and during the flood event in August 2002 shows the variation and the extent of exfiltration rates. 相似文献
98.
RICHARD C. HULA 《Journal of Urban Affairs》1985,7(3):39-56
This paper attempts to measure the effect of a court-ordered desegregation plan on three aspects of the housing market in Dallas County, Texas. The indicators include sale price, number of sales, and proportion of home sales financed by conventional mortgages. Monthly data from 1969 to 1979 are analyzed using Box-Jenkins time series models. After best fit models are determined, various intervention terms are introduced into the models to assess the impact of both a 1975 Circuit Court Order and a 1976 District Court Order. The analysis suggests neither order had a measurable effect on the housing market in Dallas. 相似文献
99.
Analysis and synthesis of on-chip spiral inductors 总被引:3,自引:0,他引:3
This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs. 相似文献
100.
The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory. 相似文献