全文获取类型
收费全文 | 4125篇 |
免费 | 201篇 |
国内免费 | 14篇 |
专业分类
化学 | 2607篇 |
晶体学 | 31篇 |
力学 | 82篇 |
数学 | 537篇 |
物理学 | 686篇 |
无线电 | 397篇 |
出版年
2023年 | 34篇 |
2022年 | 49篇 |
2021年 | 67篇 |
2020年 | 70篇 |
2019年 | 65篇 |
2018年 | 72篇 |
2017年 | 90篇 |
2016年 | 164篇 |
2015年 | 113篇 |
2014年 | 174篇 |
2013年 | 309篇 |
2012年 | 304篇 |
2011年 | 321篇 |
2010年 | 189篇 |
2009年 | 187篇 |
2008年 | 246篇 |
2007年 | 221篇 |
2006年 | 183篇 |
2005年 | 212篇 |
2004年 | 143篇 |
2003年 | 155篇 |
2002年 | 125篇 |
2001年 | 39篇 |
2000年 | 54篇 |
1999年 | 39篇 |
1998年 | 43篇 |
1997年 | 45篇 |
1996年 | 30篇 |
1995年 | 30篇 |
1994年 | 23篇 |
1993年 | 35篇 |
1992年 | 17篇 |
1991年 | 26篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 34篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 28篇 |
1976年 | 14篇 |
1975年 | 19篇 |
1974年 | 15篇 |
排序方式: 共有4340条查询结果,搜索用时 9 毫秒
111.
112.
Ram Raghava Robert M. Caddell Lynn Buege Anthony G. Atkins 《Journal of Macromolecular Science: Physics》2013,52(4):655-665
The through thickness total strains of hydrostatically bulged domes of materials are usually determined indirectly. The in-plane circumferential strains are readily measured, and then constancy of volume is invoked to determine the “missing” or unknown strain. Some of our recent work with polymers has shown that volume constancy in large-scale deformation does not hold so that the usual computations of stress and strain during bulging of sheet may be in error. We describe an electrical device that reduces such errors by directly measuring the through thickness (and, thus, the thickness “strain”) for nonmetallic materials. 相似文献
113.
114.
115.
Jaime Portilla Ina Ontiveros Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(2):172-174
The molecular skeleton of the title compound, C11H9F3N4O2, is almost planar and exhibits a polarized (charge‐separated) electronic structure in the nitroaniline portion. Molecules are linked by N—H...N and C—H...O hydrogen bonds to form a chain in which centrosymmetric R22(6) and R22(16) rings alternate. 相似文献
116.
Francisco J. Fernandez-Luque David Pérez Félix Martínez Ginés Domènech Isabel Navarrete Juan Zapata Ramón Ruiz 《Ad hoc Networks》2013,11(3):907-925
DIA (Dispositivo Inteligente de Alarma, in Spanish) is an AAL (Ambient Assisted Living) system that allows to infer a potential dangerous action of an elderly person living alone at home. This inference is obtained by a specific sensorisation with sensor nodes (portables and fixes) and a reasoning layer embedded in a PC that learns of the users behaviour patterns and advices when actual one differs significantly of the normal patterns. In AAL systems, energy is a limited resource therefore sensor devices need to be properly managed to conserve energy. In this paper, we introduce the design and implementation of innovative and specific mechanisms at the sensory layer middleware which is capable of, first to discriminate spurious motion detections assuming that these signals do not resemble the patterns of real motion detections and, second to reduce the dynamics of messages by a sensor signal processing in order to compress the whole information in one single event. The middleware achieves power saving by modifying the raw information from sensors and adapting it to the predefined semantic of the reasoning layer. It manages the important task of data processing from sensors (raw information), and transfers the pre-processed information into the top layer of reasoning in a more energy efficient way. We also address the trade-off between reducing power consumption and reducing delay for incoming data. We present results from experiments using our implementation of these mechanisms at the middleware that comprises from node firmware to the PC driver. The number of messages of the proposed method with respect to the raw data is reduced by approximately 98.5%. The resources used in the PIR signal processing is reduced by approximately 85%. The resulting delay introduced is small (10–19 s) but system dynamics is slow enough to avoid contextualisation errors or reduction of system performance. We consider these results as very satisfactory. 相似文献
117.
Flash DSC crystallization study for blown film grade bimodal HDPE resins. I. Isothermal kinetics and its application of the blown film modeling 下载免费PDF全文
Cecilia D. Treviño‐Quintanilla Ramanan Krishnamoorti Jaime Bonilla‐Ríos 《Journal of Polymer Science.Polymer Physics》2016,54(23):2425-2431
Isothermal ultra‐cooling crystallization tests were conducted on three blown film grade bimodal HDPE resins using an ultrafast scanning calorimeter, the Flash DSC. Isothermal tests were performed to study the regime transition, the thermal nucleation and the spherulitical growth using the Hoffman‐Lauritzen theory in a range between 90 °C and 116 °C. Temperature profile estimations using such data were in good agreement with actual blown film process data. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2425–2431 相似文献
118.
119.
120.