全文获取类型
收费全文 | 5521篇 |
免费 | 460篇 |
国内免费 | 126篇 |
学科分类
工业技术 | 6107篇 |
出版年
2024年 | 11篇 |
2023年 | 92篇 |
2022年 | 138篇 |
2021年 | 213篇 |
2020年 | 176篇 |
2019年 | 170篇 |
2018年 | 211篇 |
2017年 | 204篇 |
2016年 | 240篇 |
2015年 | 222篇 |
2014年 | 236篇 |
2013年 | 430篇 |
2012年 | 340篇 |
2011年 | 426篇 |
2010年 | 342篇 |
2009年 | 341篇 |
2008年 | 280篇 |
2007年 | 243篇 |
2006年 | 239篇 |
2005年 | 188篇 |
2004年 | 127篇 |
2003年 | 145篇 |
2002年 | 195篇 |
2001年 | 140篇 |
2000年 | 103篇 |
1999年 | 61篇 |
1998年 | 88篇 |
1997年 | 65篇 |
1996年 | 56篇 |
1995年 | 58篇 |
1994年 | 50篇 |
1993年 | 37篇 |
1992年 | 21篇 |
1991年 | 9篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 22篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 7篇 |
排序方式: 共有6107条查询结果,搜索用时 343 毫秒
51.
A pattern is a model or a template used to summarize and describe the behavior (or the trend) of data having generally some recurrent events. Patterns have received a considerable attention in recent years and were widely studied in the data mining field. Various pattern mining approaches have been proposed and used for different applications such as network monitoring, moving object tracking, financial or medical data analysis, scientific data processing, etc. In these different contexts, discovered patterns were useful to detect anomalies, to predict data behavior (or trend) or, more generally, to simplify data processing or to improve system performance. However, to the best of our knowledge, patterns have never been used in the context of Web archiving. Web archiving is the process of continuously collecting and preserving portions of the World Wide Web for future generations. In this paper, we show how patterns of page changes can be useful tools to efficiently archive Websites. We first define our pattern model that describes the importance of page changes. Then, we present the strategy used to (i) extract the temporal evolution of page changes, (ii) discover patterns, to (iii) exploit them to improve Web archives. The archive of French public TV channels France Télévisions is chosen as a case study to validate our approach. Our experimental evaluation based on real Web pages shows the utility of patterns to improve archive quality and to optimize indexing or storing. 相似文献
52.
This paper focuses on the problem of robust H ?? control of nonlinear switched systems with parameter uncertainty via the multiple Lyapunov functions (MLFs) approach. The uncertain parameters are assumed to be in a known compact set and are allowed to enter the system nonlinearly. Based on the explicit construction of Lyapunov functions, which avoids solving the Hamilton-Jacobi-Isaacs (HJI) inequalities, sufficient conditions for the solvability of the robust H ?? control problem of cascade nonlinear switched systems are derived under some switching signal. Then, the result is extended to solve the robust H ?? control problem of nonlinear switched systems in strict feedback form. Finally, the effectiveness of the proposed results is illustrated through a simulation example. 相似文献
53.
54.
Silvia Gazzin Matteo Dal Ben Michele Montrone Sri Jayanti Andrea Lorenzon Alessandra Bramante Cristina Bottin Rita Moretti Claudio Tiribelli 《International journal of molecular sciences》2021,22(1)
Bilirubin toxicity to the central nervous system (CNS) is responsible for severe and permanent neurologic damage, resulting in hearing loss, cognitive, and movement impairment. Timely and effective management of severe neonatal hyperbilirubinemia by phototherapy or exchange transfusion is crucial for avoiding permanent neurological consequences, but these therapies are not always possible, particularly in low-income countries. To explore alternative options, we investigated a pharmaceutical approach focused on protecting the CNS from pigment toxicity, independently from serum bilirubin level. To this goal, we tested the ability of curcumin, a nutraceutical already used with relevant results in animal models as well as in clinics in other diseases, in the Gunn rat, the spontaneous model of neonatal hyperbilirubinemia. Curcumin treatment fully abolished the landmark cerebellar hypoplasia of Gunn rat, restoring the histological features, and reverting the behavioral abnormalities present in the hyperbilirubinemic rat. The protection was mediated by a multi-target action on the main bilirubin-induced pathological mechanism ongoing CNS damage (inflammation, redox imbalance, and glutamate neurotoxicity). If confirmed by independent studies, the result suggests the potential of curcumin as an alternative/complementary approach to bilirubin-induced brain damage in the clinical scenario. 相似文献
55.
56.
Silicon - This paper presents recent progress in computational modeling on blend morphology of silicon nanowires (SiNWs) dispersed in a conjugated polymer poly(3-hexylthiophene) P3HT hybrid solar... 相似文献
57.
Faraz Montazersadgh Hao Zhang Anas Alkayal Benjamin Buckley Ben W.Kolosz Bing Xu Jin Xuan 《Frontiers of Chemical Science and Engineering》2021,15(1):208-219
Utilizing CO2 in an electro-chemical process and synthesizing value-added chemicals are amongst the few viable and scalable pathways in carbon capture and utilization technologies.CO2 electro-reduction is also counted as one of the main options entailing less fossil fuel consumption and as a future electrical energy storage strategy.The current study aims at developing a new electrochemical platform to produce low-carbon e-biofuel through multifunctional electrosynthesis and integrated co-valorisation of biomass feedstocks with captured CO2.In this approach,CO2 is reduced at the cathode to produce drop-in fuels(e.g.,methanol)while value-added chemicals(e.g.,selective oxidation of alcohols,aldehydes,carboxylic acids and amines/amides)are produced at the anode.In this work,a numerical model of a continuous-flow design considering various anodic and cathodic reactions was built to determine the most techno-economically feasible configurations from the aspects of energy efficiency,environment impact and economical values.The reactor design was then optimized via parametric analysis. 相似文献
58.
Mansour N. Ben Djeridi W. Mir L. El 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4360-4371
Journal of Inorganic and Organometallic Polymers and Materials - Nanoporous carbon matrix was prepared by the sol–gel process from pyrogallol-formaldehyde (PF) mixtures in water using picric... 相似文献
59.
60.
The molecular orientation at the outer surface of injection–stretch–blow‐molded bottles made from poly(ethylene terephthalate) was characterized and quantified by means of front‐surface reflection infrared spectroscopy based on a method developed previously. Results were obtained for two different bottle shapes (cylindrical and rectangular) molded at different injection mold temperatures (16, 38, and 60°C). For the cylindrical bottles, the preferred molecular chain orientation was found to be in the axial direction, with the Hermans orientation function near 0.3 for all three mold temperatures. For the less symmetrical rectangular bottles, a significant difference was observed between the large and small faces. For the large face, the orientation was mainly in the hoop direction; the Hermans orientation function was in the range of 0.3–0.5 and was essentially the same at all mold temperatures and positions along the bottle height. For the small face, on the other hand, the preferred orientation changed from the hoop direction near the bottom to the axial direction near the top, and the variation was more pronounced at lower mold temperatures. The utility of the front‐surface reflection technique was clearly demonstrated. It was also applied, with the use of an infrared microscope, to examine the orientation gradient across the wall thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1319–1327, 2007 相似文献