全文获取类型
收费全文 | 4679篇 |
免费 | 475篇 |
专业分类
5154篇 |
出版年
2023年 | 45篇 |
2022年 | 97篇 |
2021年 | 179篇 |
2020年 | 67篇 |
2019年 | 117篇 |
2018年 | 133篇 |
2017年 | 103篇 |
2016年 | 215篇 |
2015年 | 266篇 |
2014年 | 267篇 |
2013年 | 303篇 |
2012年 | 411篇 |
2011年 | 360篇 |
2010年 | 207篇 |
2009年 | 178篇 |
2008年 | 250篇 |
2007年 | 248篇 |
2006年 | 200篇 |
2005年 | 192篇 |
2004年 | 206篇 |
2003年 | 145篇 |
2002年 | 176篇 |
2001年 | 43篇 |
2000年 | 52篇 |
1999年 | 45篇 |
1998年 | 37篇 |
1997年 | 24篇 |
1996年 | 33篇 |
1995年 | 25篇 |
1994年 | 28篇 |
1993年 | 25篇 |
1992年 | 31篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 23篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 13篇 |
1975年 | 15篇 |
1973年 | 19篇 |
1970年 | 17篇 |
排序方式: 共有5154条查询结果,搜索用时 0 毫秒
1.
Emma Bricchi Marco Fornaciari Claudia Giannoni Francesca Greco Daniela Fascini Giuseppe Frenguelli Gianfranco Mincigrucci Bruno Romano 《Aerobiologia》1992,8(3):401-406
Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria. 相似文献
2.
3.
4.
5.
6.
7.
Yiwen Sun Zexuan Zhu Siping Chen Jega Balakrishnan Derek Abbott Anil T. Ahuja Emma Pickwell-MacPherson 《PloS one》2012,7(11)
The GP2 peptide is derived from the Human Epidermal growth factor Receptor 2 (HER2/nue), a marker protein for breast cancer present in saliva. In this paper we study the temperature dependent behavior of hydrated GP2 at terahertz frequencies and find that the peptide undergoes a dynamic transition between 200 and 220 K. By fitting suitable molecular models to the frequency response we determine the molecular processes involved above and below the transition temperature (T
D). In particular, we show that below T
D the dynamic transition is dominated by a simple harmonic vibration with a slow and temperature dependent relaxation time constant and that above T
D, the dynamic behavior is governed by two oscillators, one of which has a fast and temperature independent relaxation time constant and the other of which is a heavily damped oscillator with a slow and temperature dependent time constant. Furthermore a red shifting of the characteristic frequency of the damped oscillator was observed, confirming the presence of a non-harmonic vibration potential. Our measurements and modeling of GP2 highlight the unique capabilities of THz spectroscopy for protein characterization. 相似文献
8.
9.
10.
Molecular characterization of glutamic acid/glutamine-rich secretory proteins from rat submandibular glands 总被引:3,自引:0,他引:3
L Mirels G S Bedi D P Dickinson K W Gross L A Tabak 《The Journal of biological chemistry》1987,262(15):7289-7297
A family of abundant rat submandibular gland secretory proteins has been identified in glandular extracts and characterized. By amino acid analysis these proteins contain approximately 35% glutamic acid and glutamine plus 14% proline. They have therefore been named "Glx-rich proteins" (GRP). Plasmids containing cDNAs for a GRP have been isolated from a cDNA library prepared from rat submandibular gland poly(A)+RNA. The nucleotide sequence of these cDNAs have been determined. Approximately half of the protein coding sequence is composed of a 23-residue tandem repeat which is repeated five times. The first four repeats are highly conserved at both the nucleotide and amino acid level and consist of the prototype sequence: Asn-Gln-Glu-Pro-Pro-Ala-Thr-Ser-Gly-Ser-Glu-Glu-Glu-Gln-Gln-Gln-Gln-Glu- Pro-Thr-Gln-Ala-Glu. The expression of GRP appears to be specific to the submandibular gland. In vitro assays demonstrate that the GRP have a marked affinity for hydroxyapatite. This suggests that GRP may play a role in the formation of the protective acquired pellicle at the saliva-tooth interface. 相似文献