全文获取类型
收费全文 | 12806篇 |
免费 | 707篇 |
国内免费 | 419篇 |
专业分类
电工技术 | 501篇 |
技术理论 | 1篇 |
综合类 | 525篇 |
化学工业 | 749篇 |
金属工艺 | 351篇 |
机械仪表 | 838篇 |
建筑科学 | 627篇 |
矿业工程 | 222篇 |
能源动力 | 104篇 |
轻工业 | 699篇 |
水利工程 | 54篇 |
石油天然气 | 53篇 |
武器工业 | 110篇 |
无线电 | 2412篇 |
一般工业技术 | 891篇 |
冶金工业 | 398篇 |
原子能技术 | 131篇 |
自动化技术 | 5266篇 |
出版年
2024年 | 17篇 |
2023年 | 161篇 |
2022年 | 165篇 |
2021年 | 303篇 |
2020年 | 217篇 |
2019年 | 134篇 |
2018年 | 132篇 |
2017年 | 212篇 |
2016年 | 318篇 |
2015年 | 304篇 |
2014年 | 597篇 |
2013年 | 699篇 |
2012年 | 697篇 |
2011年 | 913篇 |
2010年 | 681篇 |
2009年 | 751篇 |
2008年 | 729篇 |
2007年 | 937篇 |
2006年 | 786篇 |
2005年 | 828篇 |
2004年 | 785篇 |
2003年 | 657篇 |
2002年 | 602篇 |
2001年 | 367篇 |
2000年 | 304篇 |
1999年 | 283篇 |
1998年 | 229篇 |
1997年 | 195篇 |
1996年 | 157篇 |
1995年 | 126篇 |
1994年 | 113篇 |
1993年 | 100篇 |
1992年 | 96篇 |
1991年 | 67篇 |
1990年 | 47篇 |
1989年 | 40篇 |
1988年 | 37篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
数字加速度传感器ADXL210在轨检仪中的应用 总被引:2,自引:0,他引:2
介绍了一种轨道检测仪及其重要传感器数字加速度传感器ADXL210的工作原理、功能、应用,并给出了ADXL210与MCS-51单片机的接口硬件电路和软件程序。 相似文献
93.
自动实时X射线检测技术在半导体制程控制中的应用 总被引:1,自引:0,他引:1
EckhardSperschneider 《电子工业专用设备》2003,32(5):27-31
对X光检测的不同技术在半导体制程上的应用作了详细的介绍;着重讨论了全旋倾斜(off-axis)X射线技术的特点和优势。 相似文献
94.
SDI接口数字监视设备的设计与实现 总被引:2,自引:0,他引:2
介绍了一种对SDV(串行数字视频)信号进行解码的设备设计方案,提出了该系统的总体构架,并对该系统的硬件设计、软件设计进行了全面的论述。设计的产品具有较高的性能价格比,已进入了推广阶段。 相似文献
95.
Abstract. A pth‐order random coefficient integer‐valued autoregressive [RCINAR(p)] model is proposed for count data. Stationarity and ergodicity properties are established. Maximum likelihood, conditional least squares, modified quasi‐likelihood and generalized method of moments are used to estimate the model parameters. Asymptotic properties of the estimators are derived. Simulation results on the comparison of the estimators are reported. The models are applied to two real data sets. 相似文献
96.
Recent research on annotation interfaces provides provocative evidence that anchored, annotation-based discussion environments
may lead to better conversations about a text. However, annotation interfaces raise complicated tradeoffs regarding screen
real estate and positioning. It is argued that solving this screen real estate problem requires limiting the number of annotations
displayed to users. In order to understand which annotations have the most learning value for students, this paper presents
two complementary studies examining the effects of annotations on students performing a reading-to-write task. The first study
used think-aloud protocols and a within-subjects methodology, finding that annotations appeared to provoke students to reflect
more critically upon the primary text. This effect was particularly strong when students encountered pairs of annotations
presenting different viewpoints on the same section of text. Student interviews suggested that annotations were most helpful
when they caused the reader to consider and weigh conflicting viewpoints. The second study used a between-subjects methodology
and a more naturalistic task to provide complementary evidence that annotations encourage more reflective responses to a text.
This study found that students who received annotated materials both perceived themselves and were perceived by instructors
as less reliant on unreflective summary strategies than students who received the same content but in a different format.
These findings indicate that the learning value of an annotation lies in its ability to provoke students to consider and weigh
new perspectives on the primary text. When selected effectively, annotations provide a critical scaffolding that can support
students’ critical thinking and argumentation activities. Collaborative digital libraries and applications for the Web 2.0
should be designed with this learning framework in mind. 相似文献
97.
Surface-based Transport Model for Mixed-Size Sediment 总被引:6,自引:0,他引:6
We present a transport model for mixed sand/gravel sediments. Fractional transport rates are referenced to the size distribution of the bed surface, rather than subsurface, making the model completely explicit and capable of predicting transient conditions. The model is developed using a new data set of 48 coupled observations of flow, transport, and bed surface grain size using five different sediments. The model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions. The model uses the full size distribution of the bed surface, including sand, and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models. The model shares some common elements with two previous surface-based transport models, but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow, transport rate, and sediments. 相似文献
98.
Extended Hyperbolic Model for Sand-to-Concrete Interfaces 总被引:1,自引:0,他引:1
Jesús E. Gómez George M. Filz Robert M. Ebeling 《Canadian Metallurgical Quarterly》2003,129(11):993-1000
A relatively simple, four-parameter extended hyperbolic model for interfaces was developed for use in soil-structure interaction analyses. The model accommodates arbitrary stress path directions and includes three important elements: (1) development of a yield surface during interface shear; (2) a formulation for yield-inducing shear stiffness that is applicable to any stress path orientation; and (3) a formulation for unloading-reloading shear stiffness. The model was evaluated against the results of shear tests performed at the interface between three different types of sand and a concrete surface under a variety of stress paths. Comparisons between measured and calculated interface response indicate that the model provides accurate estimates of the response of sand-to-concrete interfaces. 相似文献
99.
扫描式X光机及DDS在其运动控制中的应用 总被引:2,自引:0,他引:2
扫描式X光机是一种高精度,高性能的新型医疗设备,其显著优点在于大大降低了患者所受X光辐射剂量,可直接得到患者清晰的X光数字图像,缩短出片时间,X光片资料存储方便,便于实现远程诊断,该设备对运动控制部分的匀速性,平稳性和多次扫描的位置重复性的要求均很高。本文主要针对其运动控制部分的结构特点,分析了影响运动性能的主要原因,并将直接数字频率合成器应用于调速,从而实现了对其运动控制部分的要求。 相似文献
100.
Bench-scale reactor experiments were performed to study the dissolution of a binary naphthalene-in-nonane mixture nonaqueous phase liquid (NAPL) pool over a wide range of average pore water velocities, vx (≈0.1–60 m/day). Experimental NAPL pool dissolution flux values were determined using a steady-state mass balance approach. The experimental flux data were compared to model predictions made assuming either local equilibrium or mass-transfer limited conditions. The local equilibrium model could describe the trends in the average effluent concentration and dissolution flux with 0.110?m/day. Data determined to be under mass-transfer limited conditions were fit to the nonequilibrium model to estimate values for an overall mass-transfer coefficient. The calculated overall mass-transfer coefficients had an average value of 0.407 m/day and showed no correlation with vx, probably due to mass-transfer resistance becoming dominated by the diffusional resistance in the NAPL. These results suggest that the nonequilibrium approach is better suited for describing high velocity (vx>10?m/day) dissolution of multicomponent NAPL pools, and that flushing of groundwater at very high velocities may not be an effective approach for enhancing NAPL-pool dissolution flux. 相似文献