全文获取类型
收费全文 | 1683篇 |
免费 | 64篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 284篇 |
金属工艺 | 12篇 |
机械仪表 | 32篇 |
建筑科学 | 79篇 |
矿业工程 | 2篇 |
能源动力 | 33篇 |
轻工业 | 206篇 |
水利工程 | 12篇 |
石油天然气 | 11篇 |
无线电 | 68篇 |
一般工业技术 | 381篇 |
冶金工业 | 480篇 |
原子能技术 | 6篇 |
自动化技术 | 136篇 |
出版年
2023年 | 18篇 |
2022年 | 24篇 |
2021年 | 56篇 |
2020年 | 38篇 |
2019年 | 31篇 |
2018年 | 39篇 |
2017年 | 35篇 |
2016年 | 38篇 |
2015年 | 32篇 |
2014年 | 48篇 |
2013年 | 95篇 |
2012年 | 97篇 |
2011年 | 127篇 |
2010年 | 89篇 |
2009年 | 83篇 |
2008年 | 107篇 |
2007年 | 94篇 |
2006年 | 95篇 |
2005年 | 82篇 |
2004年 | 74篇 |
2003年 | 60篇 |
2002年 | 65篇 |
2001年 | 39篇 |
2000年 | 35篇 |
1999年 | 20篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 29篇 |
1995年 | 23篇 |
1994年 | 18篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1747条查询结果,搜索用时 31 毫秒
31.
Different analytical expressions for the membrane potential distribution of membranes subject to synaptic noise have been proposed and can be very helpful in analyzing experimental data. However, all of these expressions are either approximations or limit cases, and it is not clear how they compare and which expression should be used in a given situation. In this note, we provide a comparison of the different approximations available, with an aim of delineating which expression is most suitable for analyzing experimental data. 相似文献
32.
33.
34.
A numerical simulation of the aircraft impact into the exterior columns of the World Trade Center (WTC) was done using LS-DYNA. For simplification, the fuselage was modeled as a thin-walled cylinder, the wings were modeled as box beams with a fuel pocket, and the engines were represented as rigid cylinders. The exterior columns of the WTC were represented as box beams. Actual masses, material properties and dimensions of the Boeing 767 aircraft and the exterior columns of the WTC were used in this analysis. It was found that about 46% of the initial kinetic energy of the aircraft was used to damage columns. The minimum impact velocity of the aircraft to just penetrate the exterior columns would be 130?m/s. It was also found that a Boeing 767 traveling at top speed would not penetrate exterior columns of the WTC if the columns were thicker than 20?mm. 相似文献
35.
36.
Schultheiss Oliver C.; Pang Joyce S.; Torges Cynthia M.; Wirth Michelle M.; Treynor Wendy 《Canadian Metallurgical Quarterly》2005,5(1):41
Participants (N = 216) were administered a differential implicit learning task during which they were trained and tested on 3 maximally distinct 2nd-order visuomotor sequences, with sequence color serving as discriminative stimulus. During training, 1 sequence each was followed by an emotional face, a neutral face, and no face, using backward masking. Emotion (joy, surprise, anger), face gender, and exposure duration (12 ms, 209 ms) were varied between participants; implicit motives were assessed with a picture-story exercise. For power-motivated individuals, low-dominance facial expressions enhanced and high-dominance expressions impaired learning. For affiliation-motivated individuals, learning was impaired in the context of hostile faces. These findings did not depend on explicit learning of fixed sequences or on awareness of sequence-face contingencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
Berger Andrea; Sadeh Michelle; Tzur Gabriel; Shuper Avinoam; Kornreich Liora; Inbar Dov; Cohen Ian J.; Michowiz Shalom; Yaniv Isaac; Constantini Shlomi; Kessler Yoav; Merian Nachshon 《Canadian Metallurgical Quarterly》2005,19(3):362
The authors of this study investigated task switching following cerebellar damage. The study group consisted of 7 children and adolescents (M age = 13.8 years) who underwent surgical removal of a benign posterior fossa tumor. They were tested at a sufficient interval after surgery (M lag = 6.13 years) for restoration of normal cognitive skills and intelligence. Although all showed normal learning of the task compared with control participants, when rapid behavioral changes were required (short preparation time), they exhibited behavioral rigidity manifested by enhanced switching cost. These results are in line with another study on serial reaction time with the same patients (A. Berger et al., in press). They have important implications for our understanding of the cognitive sequelae of early cerebellar damage as well as the involvement of the cerebellum in task switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Neiss Michelle B.; Stevenson Jim; Sedikides Constantine; Kumashiro Madoka; Finkel Eli J.; Rusbult Caryl E. 《Canadian Metallurgical Quarterly》2005,89(4):593
Complementary approaches examined the relations among executive self, self-esteem, and negative affectivity. A cross-sectional (N = 4,242) and a longitudinal (N = 158) study established that self-esteem mediated the relation between executive self and negative affectivity. A 3rd study (N = 878 twin pairs) replicated this pattern and examined genetic and environmental influences underlying all 3 phenotypes. Covariation among the 3 phenotypes reflected largely common genetic influences, although unique genetic effects explained variability in both executive self and negative affectivity. Executive self was influenced by shared environmental influences unique from those affecting self-esteem and negative affectivity. Nonshared environmental influences accounted for the majority of variance in each construct and were primarily unique to each. The unique genetic and nonshared environmental influences support the proposition that the executive self, self-esteem, and negative affectivity capture distinct and important differences between people. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Detecting image orientation based on low-level visual content 总被引:1,自引:0,他引:1
Accurately and automatically detecting image orientation is of great importance in intelligent image processing. In this paper, we present automatic image orientation detection algorithms based on both the luminance (structural) and chrominance (color) low-level content features. The statistical learning support vector machines (SVMs) are used in our approach as the classifiers. The different sources of the extracted image features, as well as the binary classification nature of SVM, require our system to be able to integrate the outputs from multiple classifiers. Both static combiner (averaging) and trainable combiner (also based on SVMs) are proposed and evaluated in this work. Furthermore, two rejection options (regular and re-enforced ambiguity rejections) are employed to improve orientation detection accuracy by sieving out images with low confidence values during the classification. Large amounts of experiments have been conducted on a database of more than 14,000 images to validate our approaches. Discussions and future directions for this work are also addressed at the end of the paper. 相似文献
40.
Yue Esther L.; Cleland Thomas A.; Pavlis Michelle; Linster Christiane 《Canadian Metallurgical Quarterly》2004,118(1):184
Dopaminergic modulation of cortical activity has been implicated in the formation of reward associations. There is abundant evidence for dopaminergic effects on olfactory processing. Using an olfactory discrimination task, the authors show that D? and D? dopamine receptors can regulate rats' olfactory discrimination capacities and that the effects of receptor activation functionally oppose one another. Injection of either the D? agonist SKF 38393 (10 mg/kg) or the D? antagonist spiperone (0.62 mg/kg) facilitated the discrimination of similar odorants but had no effect on the discrimination of dissimilar odorants, whereas both the D, antagonist SCH 23390 (0.025 mg/kg) and the D? agonist quinpirole (0.2 mg/kg) significantly impaired rats' ability to discriminate similar and dissimilar odorants. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献