全文获取类型
收费全文 | 4117篇 |
免费 | 398篇 |
出版年
2024年 | 10篇 |
2023年 | 42篇 |
2022年 | 95篇 |
2021年 | 175篇 |
2020年 | 69篇 |
2019年 | 111篇 |
2018年 | 125篇 |
2017年 | 99篇 |
2016年 | 202篇 |
2015年 | 257篇 |
2014年 | 255篇 |
2013年 | 287篇 |
2012年 | 401篇 |
2011年 | 324篇 |
2010年 | 199篇 |
2009年 | 175篇 |
2008年 | 237篇 |
2007年 | 225篇 |
2006年 | 199篇 |
2005年 | 174篇 |
2004年 | 184篇 |
2003年 | 128篇 |
2002年 | 142篇 |
2001年 | 20篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 30篇 |
1997年 | 19篇 |
1996年 | 18篇 |
1995年 | 10篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 4篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1902年 | 3篇 |
1900年 | 3篇 |
排序方式: 共有4515条查询结果,搜索用时 15 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.
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
5.
6.
G.D.W. Curtis R.G. Mitchell Andrea F. King Emma J. Griffin 《Letters in applied microbiology》1989,8(3):95-98
A new medium has been developed for the isolation of Listeria monocytogenes from clinical specimens with a mixed flora. Almost complete inhibition of unwanted organisms was achieved and recognition of colonies of Listeria spp. was usually possible after 24 h using the aesculin-ferric ammonium citrate indicator system. Compared to McBride agar the new medium was more inhibitory to representative contaminating species in pure culture and more successful in isolating small numbers of L. monocytogenes from artificially seeded clinical specimens. 相似文献
7.
8.
9.
Giuseppe Frenguelli Emma Bricchi Bruno Romano Gianfranco Mincigrucci Francesco Ferranti Evasio Antognozzi 《Aerobiologia》1992,8(3):415-418
Summary 7 years of airborne pollen monitoring in Perugia (central Italy) were used to determine the temperature requirements to break dormancy and to resume growth and bloom ofCorylus avellana L.,Corylus needs 1000 chill-units to complete its dormancy and this value, in the Perugian area, is met by the end of December or the first days of January. MoreoverCorylus trees require 220 growth degree hours before they are able to flower. If air temperature is high, this value can be achieved in only 10 days, but if the temperature remains too low, the heat accumulation can require up to 35 days. With these parameters it is possible to build a model to predict the date of the beginning ofCorylus avellana pollen season. 相似文献
10.
Morphological changes in clostridial isolates after animal passage with other flora in mixed infections were studied by utilizing a subcutaneous abscess model in mice. We used 26 isolates of 7 clostridial species, and one isolate each of Bacteroides fragilis and Klebsiella pneumoniae. Abscesses were induced by all 7 Clostridium perfringens and 3 Clostridium butyricum isolates and by some of the other isolates. A thick granular wall prior to animal inoculation was shown only in C. perfringens, C. butyricum, and C. difficile. This structure was observed in other clostridia only following their animal passage alone or when co-inoculated with K. pneumoniae or B. fragilis. 相似文献