全文获取类型
收费全文 | 8467篇 |
免费 | 599篇 |
国内免费 | 3篇 |
出版年
2023年 | 48篇 |
2022年 | 47篇 |
2021年 | 199篇 |
2020年 | 118篇 |
2019年 | 149篇 |
2018年 | 201篇 |
2017年 | 215篇 |
2016年 | 300篇 |
2015年 | 478篇 |
2014年 | 500篇 |
2013年 | 603篇 |
2012年 | 723篇 |
2011年 | 621篇 |
2010年 | 392篇 |
2009年 | 359篇 |
2008年 | 466篇 |
2007年 | 497篇 |
2006年 | 428篇 |
2005年 | 400篇 |
2004年 | 373篇 |
2003年 | 342篇 |
2002年 | 316篇 |
2001年 | 88篇 |
2000年 | 51篇 |
1999年 | 88篇 |
1998年 | 80篇 |
1997年 | 62篇 |
1996年 | 53篇 |
1995年 | 59篇 |
1994年 | 55篇 |
1993年 | 58篇 |
1992年 | 49篇 |
1991年 | 53篇 |
1990年 | 54篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 16篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 29篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1974年 | 21篇 |
1970年 | 17篇 |
排序方式: 共有9069条查询结果,搜索用时 15 毫秒
1.
2.
Ravi R. Sonani Rajesh P. Rastogi Richard Cogdell Bruno Robert Datta Madamwar 《Photosynthesis research》2018,136(2):171-181
Femtosecond transient absorption was used to study excitation decay in monomeric and trimeric cyanobacterial Photosystem I (PSI) being prepared in three states: (1) in aqueous solution, (2) deposited and dried on glass surface (either conducting or non-conducting), and (3) deposited on glass (conducting) surface but being in contact with aqueous solvent. The main goal of this contribution was to determine the reason of the acceleration of the excitation decay in dried PSI deposited on the conducting surface relative to PSI in solution observed previously using time-resolved fluorescence (Szewczyk et al., Photysnth Res 132(2):111–126, 2017). We formulated two alternative working hypotheses: (1) the acceleration results from electron injection from PSI to the conducting surface; (2) the acceleration is caused by dehydration and/or crowding of PSI proteins deposited on the glass substrate. Excitation dynamics of PSI in all three types of samples can be described by three main components of subpicosecond, 3–5, and 20–26 ps lifetimes of different relative contributions in solution than in PSI-substrate systems. The presence of similar kinetic components for all the samples indicates intactness of PSI proteins after their deposition onto the substrates. The kinetic traces for all systems with PSI deposited on substrates are almost identical and they decay significantly faster than the kinetic traces of PSI in solution. We conclude that the accelerated excitation decay in PSI-substrate systems is caused mostly by dense packing of proteins. 相似文献
3.
Daniela Giordano Roberta Russo Daniela Coppola Giovanna Altomonte Guido di Prisco Stefano Bruno Cinzia Verde 《Hydrobiologia》2015,761(1):293-312
Notothenioidei, the taxonomic group of teleosts that dominates the Southern Ocean and dwell in the Ross Sea at large, provide an example of marine species that underwent unique adaptations to life at low temperatures and high oxygen concentrations, resulting in morphological, physiological, genomic, and biochemical peculiarities in comparison with warm-water fish. Global Warming raises concerns over the fate of these stenothermal fish, as their adaptation has been accompanied by irreversible genomic losses, which suggest a poor genetic potential to adapt to warmer climates. Specifically, this review focuses on adaptation of proteins belonging to the globin superfamily, which include the respiratory proteins hemoglobin and myoglobin and the non-respiratory proteins neuroglobin and cytoglobin. Here, we describe their molecular adaptations to cold temperatures in the framework of the physiology of oxygen transport and management of oxidative stress in fish species largely populating the Ross Sea. 相似文献
4.
Anna Cleta Croce Uliana De Simone Mariapia Vairetti Andrea Ferrigno Eleonora Boncompagni Isabel Freitas Giovanni Bottiroli 《Photochemical & photobiological sciences》2008,7(9):1046-1053
Autofluorescence spectroscopy is a promising and powerful approach for an in vivo, real time characterization of liver functional properties. In this work, preliminary results on the dependence of liver autofluorescence parameters on the nutritional status are reported, with particular attention to vitamin A and lipid accumulation in liver tissue. Normally fed and 24 h starving rats were used as animal models. Histochemical and autofluorescence analysis showed that lipids and vitamin A colocalize in the liver parenchyma. Fasting condition results in a parallel increase in both lipids and vitamin A. Autofluorescence imaging and microspectrofluorometric analysis carried out on unfixed, unstained tissue sections under 366 nm excitation, evidenced differences in both spectral shape and response to continuous irradiation between liver biopsies from fed and starving rats. As to photobleaching, in particular, fitting analysis evidenced a reduction of about 85% of the signal attributable solely to vitamin A during the first 10 s of irradiation. The tissue whole emission measured in fed and starving rat livers exhibited reductions of about 35% and 52%, respectively, that are closely related to vitamin A contents. The findings open interesting perspectives for the set up of an in situ, real time diagnostic procedure for the assessment of liver lipid accumulation, exploiting the photophysical properties of vitamin A. 相似文献
5.
6.
7.
Bruno Schnssnig 《Plant Systematics and Evolution》1923,72(6-8):199-222
Ohne Zusammenfassung 相似文献
8.
Bruno Mack 《Plant Systematics and Evolution》1953,100(1-2):147-152
Ohne Zusammenfassung 相似文献
9.
Silva Bruno Garcia Damianovic Márcia Helena Rissato Zamariolli Foresti Eugenio 《Bioprocess and biosystems engineering》2018,41(8):1115-1120
Bioprocess and Biosystems Engineering - This study assessed the simultaneous nitrification and denitrification processes and remaining organic matter removal from anaerobic reactor effluent... 相似文献
10.
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