全文获取类型
收费全文 | 1835篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 48篇 |
理论与方法论 | 21篇 |
现状及发展 | 1213篇 |
研究方法 | 79篇 |
综合类 | 419篇 |
自然研究 | 72篇 |
出版年
2020年 | 15篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 30篇 |
2014年 | 15篇 |
2013年 | 23篇 |
2012年 | 53篇 |
2011年 | 90篇 |
2010年 | 23篇 |
2009年 | 16篇 |
2008年 | 40篇 |
2007年 | 35篇 |
2006年 | 56篇 |
2005年 | 51篇 |
2004年 | 35篇 |
2003年 | 44篇 |
2002年 | 43篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 19篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1979年 | 35篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1975年 | 29篇 |
1974年 | 36篇 |
1973年 | 46篇 |
1972年 | 42篇 |
1971年 | 38篇 |
1970年 | 67篇 |
1969年 | 55篇 |
1968年 | 87篇 |
1967年 | 64篇 |
1966年 | 47篇 |
1965年 | 46篇 |
1964年 | 42篇 |
1963年 | 20篇 |
1962年 | 24篇 |
1961年 | 17篇 |
1959年 | 15篇 |
1958年 | 12篇 |
1957年 | 13篇 |
排序方式: 共有1852条查询结果,搜索用时 15 毫秒
811.
J. Marec Jarmila Keprtová Věra Spurná Eva Minářová J. Michl 《Cellular and molecular life sciences : CMLS》1977,33(1):33-34
Summary The uptake of exogenous3H-DNA by mammalian cells is increased in the presence of a specific serum protein complex — growth-promoting alpha-globulin (GPAG).3H-DNA is retained in the cell nucleus in a quantity 3 times higher than for control cultures without GPAG even after 47h of additional cultivation in the medium without3H-DNA. 相似文献
812.
Summary Ricinoleic acid was found in differentClaviceps sp., indicating that it is neither specific chemotaxonomic marker ofClaviceps purpurea, nor a specific indicator of peptide alkaloid synthesis. 相似文献
813.
Summary Serum from rats exposed for 3 days to 5 °C stimulated the multiplication of mouse heteroploid and human and rat diploid cells in culture. The response of the cells to this unspecific growth stimulation was related to the growth capacities of the different cell types. 相似文献
814.
J. Křivánek 《Cellular and molecular life sciences : CMLS》1978,34(5):574-575
Summary Topical application of concentrated solutions of KCl resulted in reduction of charging of tRNA 7 min after s.c. injection of L-(U-14C) leucine. Neither radioactivity nor pool size of the total amino acids changed during this period. 相似文献
815.
Summary Saline drinking combined with DOCA-treatment was found to decrease renal renin in weanlings at a higher rate than in adult rats, with a comparable saline consumption level. The decrease was not potentiated by uninephrectomy. 相似文献
816.
A. G. González J. M. Arteaga B. M. Fraga M. G. Hernández J. Fayos 《Cellular and molecular life sciences : CMLS》1978,34(5):554-554
Summary The molecular structure and absolute configurationI was assigned to jhanilactone, a new lactone fromEupatorium jhanii Robinson, on the basis of X-ray crystallography and circular dichroism data.Part 37 in the series Chemistry of the Composites. For Part 36, see A.G. González, J. Bermejo, I. Cabrera, G.M. Massanet, H. Mansilla and J.M. Amaro, Phytochemistry, submitted for publication.Acknowledgment. We thank Prof. S. García-Blanco, Instituto Rocasolano, Madrid for the use of an X-ray diffractometer and Prof D.N. Kirk, Westfield College, London for the CD data. 相似文献
817.
818.
The ability to process temporal information is fundamental to sensory perception, cognitive processing and motor behaviour of all living organisms, from amoebae to humans. Neural circuit mechanisms based on neuronal and synaptic properties have been shown to process temporal information over the range of tens of microseconds to hundreds of milliseconds. How neural circuits process temporal information in the range of seconds to minutes is much less understood. Studies of working memory in monkeys and rats have shown that neurons in the prefrontal cortex, the parietal cortex and the thalamus exhibit ramping activities that linearly correlate with the lapse of time until the end of a specific time interval of several seconds that the animal is trained to memorize. Many organisms can also memorize the time interval of rhythmic sensory stimuli in the timescale of seconds and can coordinate motor behaviour accordingly, for example, by keeping the rhythm after exposure to the beat of music. Here we report a form of rhythmic activity among specific neuronal ensembles in the zebrafish optic tectum, which retains the memory of the time interval (in the order of seconds) of repetitive sensory stimuli for a duration of up to approximately 20 s. After repetitive visual conditioning stimulation (CS) of zebrafish larvae, we observed rhythmic post-CS activities among specific tectal neuronal ensembles, with a regular interval that closely matched the CS. Visuomotor behaviour of the zebrafish larvae also showed regular post-CS repetitions at the entrained time interval that correlated with rhythmic neuronal ensemble activities in the tectum. Thus, rhythmic activities among specific neuronal ensembles may act as an adjustable 'metronome' for time intervals in the order of seconds, and serve as a mechanism for the short-term perceptual memory of rhythmic sensory experience. 相似文献
819.
Sánchez-Lavega A Orton GS Hueso R García-Melendo E Pérez-Hoyos S Simon-Miller A Rojas JF Gómez JM Yanamandra-Fisher P Fletcher L Joels J Kemerer J Hora J Karkoschka E de Pater I Wong MH Marcus PS Pinilla-Alonso N Carvalho F Go C Parker D Salway M Valimberti M Wesley A Pujic Z 《Nature》2008,451(7177):437-440
The atmospheres of the gas giant planets (Jupiter and Saturn) contain jets that dominate the circulation at visible levels. The power source for these jets (solar radiation, internal heat, or both) and their vertical structure below the upper cloud are major open questions in the atmospheric circulation and meteorology of giant planets. Several observations and in situ measurements found intense winds at a depth of 24 bar, and have been interpreted as supporting an internal heat source. This issue remains controversial, in part because of effects from the local meteorology. Here we report observations and modelling of two plumes in Jupiter's atmosphere that erupted at the same latitude as the strongest jet (23 degrees N). The plumes reached a height of 30 km above the surrounding clouds, moved faster than any other feature (169 m s(-1)), and left in their wake a turbulent planetary-scale disturbance containing red aerosols. On the basis of dynamical modelling, we conclude that the data are consistent only with a wind that extends well below the level where solar radiation is deposited. 相似文献
820.
Xiaoming Feng Bojie Fu Yuan Zhang Naiqing Pan Zhenzhong Zeng Hanqin Tian Yihe Lyu Yongzhe Chen Philippe Ciais Yingping Wang Lu Zhang Lei Cheng Fernando T.Maestre Marcos Fernández-Martínez Jordi Sardans Josep Pe?uelas 《科学通报(英文版)》2021,(14):1462-1471
Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we ca... 相似文献