全文获取类型
收费全文 | 37014篇 |
免费 | 4502篇 |
国内免费 | 2452篇 |
专业分类
电工技术 | 3165篇 |
综合类 | 3906篇 |
化学工业 | 2949篇 |
金属工艺 | 889篇 |
机械仪表 | 2600篇 |
建筑科学 | 3436篇 |
矿业工程 | 632篇 |
能源动力 | 1114篇 |
轻工业 | 5492篇 |
水利工程 | 818篇 |
石油天然气 | 1474篇 |
武器工业 | 533篇 |
无线电 | 6058篇 |
一般工业技术 | 4418篇 |
冶金工业 | 1457篇 |
原子能技术 | 1090篇 |
自动化技术 | 3937篇 |
出版年
2024年 | 104篇 |
2023年 | 650篇 |
2022年 | 1203篇 |
2021年 | 1549篇 |
2020年 | 1497篇 |
2019年 | 1338篇 |
2018年 | 1179篇 |
2017年 | 1492篇 |
2016年 | 1666篇 |
2015年 | 1743篇 |
2014年 | 2270篇 |
2013年 | 2380篇 |
2012年 | 3132篇 |
2011年 | 3296篇 |
2010年 | 2189篇 |
2009年 | 2145篇 |
2008年 | 1885篇 |
2007年 | 2210篇 |
2006年 | 1940篇 |
2005年 | 1659篇 |
2004年 | 1273篇 |
2003年 | 1143篇 |
2002年 | 839篇 |
2001年 | 776篇 |
2000年 | 648篇 |
1999年 | 554篇 |
1998年 | 489篇 |
1997年 | 372篇 |
1996年 | 339篇 |
1995年 | 332篇 |
1994年 | 272篇 |
1993年 | 257篇 |
1992年 | 197篇 |
1991年 | 141篇 |
1990年 | 134篇 |
1989年 | 93篇 |
1988年 | 80篇 |
1987年 | 63篇 |
1986年 | 43篇 |
1985年 | 51篇 |
1984年 | 39篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1980年 | 28篇 |
1979年 | 24篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1959年 | 14篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Application of high‐temperature Fenton oxidation for the treatment of sulfonation plant wastewater 下载免费PDF全文
102.
103.
104.
105.
Bun-Hee Lee Young-Min Park Seung-Hwan Lee Miseon Shim 《International journal of molecular sciences》2015,16(3):6251-6265
Background: Animal and clinical studies have demonstrated that the loudness dependence of auditory evoked potentials (LDAEP) is inversely related to central serotonergic activity, with a high LDAEP reflecting weak serotonergic neurotransmission and vice versa, though the findings in humans have been less consistent. In addition, a high pretreatment LDAEP appears to predict a favorable response to antidepressant treatments that augment the actions of serotonin. The aim of this study was to test whether the baseline LDAEP is correlated with response to long-term maintenance treatment in patients with major depressive disorder (MDD). Methods: Scalp N1, P2 and N1/P2 LDAEP and standardized low resolution brain electromagnetic tomography-localized N1, P2, and N1/P2 LDAEP were evaluated in 41 MDD patients before and after they received antidepressant treatment (escitalopram (n = 32, 10.0 ± 4.0 mg/day), sertraline (n = 7, 78.6 ± 26.7 mg/day), and paroxetine controlled-release formulation (n = 2, 18.8 ± 8.8 mg/day)) for more than 12 weeks. A treatment response was defined as a reduction in the Beck Depression Inventory (BDI) score of >50% between baseline and follow-up. Results: The responders had higher baseline scalp P2 and N1/P2 LDAEP than nonresponders (p = 0.017; p = 0.036). In addition, changes in total BDI score between baseline and follow-up were larger in subjects with a high baseline N1/P2 LDAEP than those with a low baseline N1/P2 LDAEP (p = 0.009). There were significantly more responders in the high-LDAEP group than in the low-LDAEP group (p = 0.041). Conclusions: The findings of this study reveal that a high baseline LDAEP is associated with a clinical response to long-term antidepressant treatment. 相似文献
106.
Shannon M. Fast Marta C. González James M. Wilson Natasha Markuzon 《Journal of the Royal Society Interface》2015,12(104)
Epidemic trajectories and associated social responses vary widely between populations, with severe reactions sometimes observed. When confronted with fatal or novel pathogens, people exhibit a variety of behaviours from anxiety to hoarding of medical supplies, overwhelming medical infrastructure and rioting. We developed a coupled network approach to understanding and predicting social response. We couple the disease spread and panic spread processes and model them through local interactions between agents. The social contagion process depends on the prevalence of the disease, its perceived risk and a global media signal. We verify the model by analysing the spread of disease and social response during the 2009 H1N1 outbreak in Mexico City and 2003 severe acute respiratory syndrome and 2009 H1N1 outbreaks in Hong Kong, accurately predicting population-level behaviour. This kind of empirically validated model is critical to exploring strategies for public health intervention, increasing our ability to anticipate the response to infectious disease outbreaks. 相似文献
107.
Boundary colors are observed when light from a scene is dispersed by a prism or diffraction grating. We discovered that patterns with repeating black and white stripes can produce repeating bands of boundary colors with two hues. These hues are virtually constant as measured by chromaticity or CIELAB. We found seven cases of this kind using a new appearance model for boundary colors. The model correctly predicts that green and magenta bands recur as stripe widths and dispersion strength vary. The first green/magenta case in the sequence traces out an accurate ellipse in XYZ color space. Green and magenta bands are prominent in supernumerary rainbows and interference rings, and we explain why that might be the case. The explanation is based on an interesting property of the visible spectrum. In addition to the green/magenta cases, the other cases are orange/cyan, yellowish‐green/purple, and yellow/violet. The success of the boundary color appearance model implies that bands are perceived as if the wavelength responses of the cones were essentially independent, which contradicts the actual behavior of cones. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 135–146, 2015 相似文献
108.
《Measurement》2015
A new approach of frequency shifting by rotating kernel is proposed to improve the performance of a spatial filtering velocimeter, used to provide accurate velocity information for a vehicle self-contained navigation system. A linear CMOS image sensor was employed both as a spatiotemporal differential spatial filter and as a photodetector. The filtering operation was fully performed in FPGA and is realized by applying a rotating kernel to the pixel values of the image. Theoretical analysis showed this method could double the maximum measurable velocity. The power spectrum of the output signal was obtained by fast Fourier transform (FFT), and was corrected by a frequency spectrum correction algorithm, named energy centrobaric correction. This velocimeter was used to measure the moving velocities of a conveyor belt. Experimental results verified the method’s ability of reducing the output signal frequency and standard uncertainty of velocity measurement. What is more, the undesired output introduced by frequency shifting to the power spectrum of the output signal was deeply investigated and a new method was proposed to eliminate the undesired component in output signals. This velocimeter aims at providing accurate velocity information for vehicle autonomous navigation system. 相似文献
109.
Nowadays, the rapid development of the internet calls for a high performance file system, and a lot of efforts have already been devoted to the issue of assigning nonpartitioned files in a parallel file system with the aim of pursuing a prompt response to requests. Yet most of the existing strategies still fail to bring about an optimal performance on system mean response time metrics, and new strategies which can achieve better performance in terms of mean response time become indispensable for parallel file systems. This paper, while addressing the issue of assigning nonpartitioned files in parallel file systems where the file accesses exhibit Poisson arrival rates and fixed service times, presents an on-line file assignment strategy, named prediction-based dynamic file assignment (PDFA), to minimize the mean response time among disks under different workload conditions, and a comparison of the PDFA with the well-known file assignment algorithms, such as HP and SOR. Comprehensive experimental results show that PDFA is able to improve the performance consistently in terms of mean response time among all algorithms for comparison. 相似文献
110.
To assess the dynamic impact of intermittency of rapidly increasing solar photovoltaic generation on the grid, this article presents the modeling and integration of the components that need to be considered, including the solar photovoltaic plant, battery energy storage system, grid-tied interface, and associated control systems. The complexity and accuracy of these models are suitable for evaluating the transient impact on bulk power systems. Of particular interest is the grid inertial response in such situations as different penetration levels of solar generation and fast cloud transient induced solar generation decrease coupled with outages that recurrently occur in the grid, e.g., a generator trip. The impact of such events on the grid frequency responses is investigated using a simplified simulation approach to account for the locational or spatial irradiance variation patterns and cloud movements. Responsive battery energy storage systems are recognized as an effective means to improve the inertial response. 相似文献