全文获取类型
收费全文 | 24526篇 |
免费 | 108篇 |
国内免费 | 81篇 |
专业分类
系统科学 | 235篇 |
丛书文集 | 229篇 |
教育与普及 | 62篇 |
理论与方法论 | 165篇 |
现状及发展 | 10321篇 |
研究方法 | 1107篇 |
综合类 | 12160篇 |
自然研究 | 436篇 |
出版年
2017年 | 230篇 |
2012年 | 374篇 |
2011年 | 923篇 |
2010年 | 199篇 |
2008年 | 482篇 |
2007年 | 685篇 |
2006年 | 466篇 |
2005年 | 506篇 |
2004年 | 505篇 |
2003年 | 504篇 |
2002年 | 475篇 |
2001年 | 780篇 |
2000年 | 751篇 |
1999年 | 537篇 |
1994年 | 334篇 |
1992年 | 472篇 |
1991年 | 365篇 |
1990年 | 407篇 |
1989年 | 372篇 |
1988年 | 360篇 |
1987年 | 372篇 |
1986年 | 371篇 |
1985年 | 525篇 |
1984年 | 397篇 |
1983年 | 302篇 |
1982年 | 283篇 |
1981年 | 277篇 |
1980年 | 309篇 |
1979年 | 709篇 |
1978年 | 540篇 |
1977年 | 498篇 |
1976年 | 450篇 |
1975年 | 495篇 |
1974年 | 565篇 |
1973年 | 506篇 |
1972年 | 558篇 |
1971年 | 649篇 |
1970年 | 803篇 |
1969年 | 651篇 |
1968年 | 670篇 |
1967年 | 597篇 |
1966年 | 579篇 |
1965年 | 411篇 |
1959年 | 234篇 |
1958年 | 410篇 |
1957年 | 269篇 |
1956年 | 238篇 |
1955年 | 198篇 |
1954年 | 242篇 |
1948年 | 189篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Aristotle Said “Happiness is a State of Activity” — Predicting Mood Through Body Sensing with Smartwatches 总被引:1,自引:1,他引:0
Peter A. Gloor Andrea Fronzetti Colladon Francesca Grippa Pascal Budner Joscha Eirich 《系统科学与系统工程学报(英文版)》2018,27(5):586-612
We measure and predict states of Activation and Happiness using a body sensing application connected to smartwatches. Through the sensors of commercially available smartwatches we collect individual mood states and correlate them with body sensing data such as acceleration, heart rate, light level data, and location, through the GPS sensor built into the smartphone connected to the smartwatch. We polled users on the smartwatch for seven weeks four times per day asking for their mood state. We found that both Happiness and Activation are negatively correlated with heart beats and with the levels of light. People tend to be happier when they are moving more intensely and are feeling less activated during weekends. We also found that people with a lower Conscientiousness and Neuroticism and higher Agreeableness tend to be happy more frequently. In addition, more Activation can be predicted by lower Openness to experience and higher Agreeableness and Conscientiousness. Lastly, we find that tracking people’s geographical coordinates might play an important role in predicting Happiness and Activation. The methodology we propose is a first step towards building an automated mood tracking system, to be used for better teamwork and in combination with social network analysis studies. 相似文献
2.
Danielle Kamato Muhamad Ashraf Rostam Rebekah Bernard Terrence J. Piva Nitin Mantri Daniel Guidone Wenhua Zheng Narin Osman Peter J. Little 《Cellular and molecular life sciences : CMLS》2015,72(4):799-808
G protein-coupled receptor (GPCR) signalling is mediated through transactivation-independent signalling pathways or the transactivation of protein tyrosine kinase receptors and the recently reported activation of the serine/threonine kinase receptors, most notably the transforming growth factor-β receptor family. Since the original observation of GPCR transactivation of protein tyrosine kinase receptors, there has been considerable work on the mechanism of transactivation and several pathways are prominent. These pathways include the “triple membrane bypass” pathway and the generation of reactive oxygen species. The recent recognition of GPCR transactivation of serine/threonine kinase receptors enormously broadens the GPCR signalling paradigm. It may be predicted that the transactivation of serine/threonine kinase receptors would have mechanistic similarities with transactivation of tyrosine kinase pathways; however, initial studies suggest that these two transactivation pathways are mechanistically distinct. Important questions are the relative importance of tyrosine and serine/threonine transactivation pathways, the contribution of transactivation to overall GPCR signalling, mechanisms of transactivation and the range of cell types in which this phenomenon occurs. The ultimate significance of transactivation-dependent signalling remains to be defined but it appears to be prominent and if so will represent a new cell signalling frontier. 相似文献
3.
Photon emission of phagocytes in relation to stress and disease. 总被引:1,自引:0,他引:1
Phagocytes, the first-line cells of the body's defence mechanisms against invading pathogens, kill microorganisms by means of lysosomal degradative enzymes and highly toxic reactive oxygen intermediates. The reactive oxygen compounds are produced, in a process called the 'respiratory burst', by the NADPH oxidase complex in plasma membranes, and by myeloperoxidase in phagolysosomes after degranulation. These processes generate electronically excited states which, on relaxation, emit photons, giving rise to phagocyte chemiluminescence (CL). This paper describes the conditions for the measurement of CL, and reviews the activity of phagocytes from individuals undergoing stress or disease. The capability of phagocytes to emit photons reflects remarkably well the pathophysiological state of the host. In many cases even the magnitude of the stress, the presence of a pathogen in the body, or the activity of the disease can be estimated. Physiological changes, e.g. in the reproductive cycle, can also be predicted. 相似文献
4.
5.
W. Jadassohn E. Cherbuliez P. Boymond H. Isler 《Cellular and molecular life sciences : CMLS》1948,4(6):225-226
Summary The authors show the antibiotic activity of water-insoluble salts of hydrosoluble antibiotics in the case of penicillin G (salts of iron, copper, silver, gold, and uranium) and streptomycin (oleate). 相似文献
6.
1 Results Acid-doped polybenzimidazoles[1] are particularly appealing because of high proton conductivity with no or low humidification and promising fuel cells performances. PBI, in fact, contains basic functional groups which can easily interact with strong oxo-acids, such as H3PO4 and H2SO4. The acid partially protonates the polymer and partially is freely dispersed in the polymer backbone, so allowing proton migration via Grotthuss mechanism along the anionic chains[2]. Anyway, a technological limit... 相似文献
7.
8.
9.
10.