全文获取类型
收费全文 | 7874篇 |
免费 | 1069篇 |
国内免费 | 479篇 |
专业分类
电工技术 | 247篇 |
技术理论 | 1篇 |
综合类 | 378篇 |
化学工业 | 1048篇 |
金属工艺 | 127篇 |
机械仪表 | 297篇 |
建筑科学 | 282篇 |
矿业工程 | 50篇 |
能源动力 | 692篇 |
轻工业 | 443篇 |
水利工程 | 156篇 |
石油天然气 | 117篇 |
武器工业 | 55篇 |
无线电 | 815篇 |
一般工业技术 | 533篇 |
冶金工业 | 134篇 |
原子能技术 | 420篇 |
自动化技术 | 3627篇 |
出版年
2024年 | 14篇 |
2023年 | 74篇 |
2022年 | 169篇 |
2021年 | 199篇 |
2020年 | 170篇 |
2019年 | 178篇 |
2018年 | 196篇 |
2017年 | 341篇 |
2016年 | 367篇 |
2015年 | 388篇 |
2014年 | 514篇 |
2013年 | 466篇 |
2012年 | 540篇 |
2011年 | 610篇 |
2010年 | 506篇 |
2009年 | 527篇 |
2008年 | 552篇 |
2007年 | 452篇 |
2006年 | 489篇 |
2005年 | 487篇 |
2004年 | 450篇 |
2003年 | 412篇 |
2002年 | 279篇 |
2001年 | 168篇 |
2000年 | 144篇 |
1999年 | 115篇 |
1998年 | 87篇 |
1997年 | 83篇 |
1996年 | 57篇 |
1995年 | 50篇 |
1994年 | 60篇 |
1993年 | 48篇 |
1992年 | 38篇 |
1991年 | 34篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1959年 | 2篇 |
排序方式: 共有9422条查询结果,搜索用时 15 毫秒
21.
In this paper we suggest a new statistical method of correcting the results of hot-line experiments for the effects of background sources and we use the new method to reassess the adequacy of three probability distributions proposed in the literature for image spread from line sources. The data are from sources labelled with 125I in semi-thin resin sections 0·4-0·8 μm in thickness. The new method reveals that two of the models describe the empirical distributions more closely than earlier analysis had suggested, and it confirms an increasing relationship between half distance of image spread and the thickness of the source. However, it also confirms that considerable ‘inter hot-line’ experimental variation remains, even after background correction. This suggests that multiple experiments are needed to produce reliable estimates of half distance. 相似文献
22.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech. 相似文献
23.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
24.
25.
Joel P. Martin J. Edward Swan II Robert J. Moorhead II Zhanping Liu Shangshu Cai 《Computer Graphics Forum》2008,27(3):991-998
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields. 相似文献
26.
Load bearing capacity of cracked specimens can be improved following pre-loading procedures like warm pre-stressing (WPS). In this paper, the effects of modes I and II pre-loading on fracture load of a central angled crack specimen are studied by finite element analysis. The specimen is reloaded either in mode I or in mode II. To predict the fracture load of cracked specimen after pre-loading, the maximum tensile stress (MTS) and maximum shear stress (MSS) criteria are used. It is shown that mode II fracture load is independent of pre-loading but the mode I fracture load is highly improved after warm pre-stressing. The mode mixity of the specimen is also changed when the pre-loading and reloading modes are not identical. An increase in the fracture load of the specimen following pre-loading may be due to change of failure mode as predicted by finite element analysis in this work. 相似文献
27.
介绍了平板显示控制芯片TO944的特点、功能、原理,并给出了基于T0944芯片的新型平板显示接口卡的软硬件实现方案,该方案具有电路简单、高可靠性、高性价比、高显示质量等优点,可用于各种不同类型与不同尺寸的平板显示器的显示。 相似文献
28.
首先简单叙述了C3I系统在军事上的应用,然后针对我国各类大中型城市的交通现状及特点,涉及到城市交通管理、道路管理、车辆管理和城市交通管理指挥中心站、区域指挥站及各交叉路口控制站,提出将C3I系统体系结构运用到民用城市交通管理中去的构想。 相似文献
29.
30.