全文获取类型
收费全文 | 868篇 |
免费 | 55篇 |
专业分类
923篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 28篇 |
2020年 | 11篇 |
2019年 | 28篇 |
2018年 | 27篇 |
2017年 | 17篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 50篇 |
2013年 | 52篇 |
2012年 | 75篇 |
2011年 | 78篇 |
2010年 | 53篇 |
2009年 | 55篇 |
2008年 | 72篇 |
2007年 | 62篇 |
2006年 | 53篇 |
2005年 | 42篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1983年 | 3篇 |
1953年 | 1篇 |
排序方式: 共有923条查询结果,搜索用时 15 毫秒
11.
The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. xbohemica. By using flow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. xbohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. xbohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described briefly and the possible origins of the cytotypes discussed. 相似文献
12.
13.
Inside Back Cover: The conformation of bovine serum albumin adsorbed to the surface of single all‐dielectric nanoparticles following light‐induced heating (J. Biophotonics 7/2018) 下载免费PDF全文
Andrei A. Krasilin Katerina Volodina Arina A. Sukhova Mihail I. Petrov Dmitry A. Zuev Vyacheslav A. Dyachuk Valentin A. Milichko 《Journal of biophotonics》2018,11(7)
Germanium vs Silicon: All‐dielectric nanoparticles provides the heat resistance for proteins under light‐induced heating. Further details can be found in the article by Andrei A. Krasilin et al. ( e201700322 )
14.
15.
Zhang J Bao S Furumai R Kucera KS Ali A Dean NM Wang XF 《Molecular and cellular biology》2005,25(22):9910-9919
In response to DNA damage or replication stress, the protein kinase ATR is activated and subsequently transduces genotoxic signals to cell cycle control and DNA repair machinery through phosphorylation of a number of downstream substrates. Very little is known about the molecular mechanism by which ATR is activated in response to genotoxic insults. In this report, we demonstrate that protein phosphatase 5 (PP5) is required for the ATR-mediated checkpoint activation. PP5 forms a complex with ATR in a genotoxic stress-inducible manner. Interference with the expression or the activity of PP5 leads to impairment of the ATR-mediated phosphorylation of hRad17 and Chk1 after UV or hydroxyurea treatment. Similar results are obtained in ATM-deficient cells, suggesting that the observed defect in checkpoint signaling is the consequence of impaired functional interaction between ATR and PP5. In cells exposed to UV irradiation, PP5 is required to elicit an appropriate S-phase checkpoint response. In addition, loss of PP5 leads to premature mitosis after hydroxyurea treatment. Interestingly, reduced PP5 activity exerts differential effects on the formation of intranuclear foci by ATR and replication protein A, implicating a functional role for PP5 in a specific stage of the checkpoint signaling pathway. Taken together, our results suggest that PP5 plays a critical role in the ATR-mediated checkpoint activation. 相似文献
16.
We investigate whether the fourth intracellular loop (IL4) of D1 and D5 dopaminergic receptors (D1R, D5R) confers D1-like subtype-specific signaling properties. Using chimeric receptors (D1R-IL4B and D5R-IL4A), we show that swapping of IL4 leads to a switch in dopamine affinity and constitutive activity of D1R and D5R. Dopamine potency was reduced for both chimeras in comparison with wild-type receptors. Moreover, dopamine-mediated maximal activation was drastically increased in cells expressing D1R-IL4B when compared with those harboring D5R-IL4A or wild-type receptors. In conclusion, IL4 plays a pivotal role in imparting subtype-specific ligand binding and activation properties to highly homologous seven-transmembrane receptors. 相似文献
17.
<Emphasis Type="Italic">Daphnia galeata</Emphasis> in the deep hypolimnion: spatial differentiation of a “typical epilimnetic” species 总被引:1,自引:1,他引:1
One of the most serious threats to tropical mangrove ecosystems caused by shrimp farming activities is the poor management
of pond waste materials. We hypothesise that mangroves can tolerate chemical residues discharged from shrimp farms and can
be used as biofilters, but the capability of mangroves to cope with solid sediments dredged from shrimp ponds is limited.
Our study in Pak Phanang, Thailand, confirmed that the excess sediments discharged from nearby shrimp ponds reduced mangrove
growth rates and increased mortality rates. A series of transformed multi-temporal satellite images was used in combination
with the field data to support this claim. In addition, a comparison between four dominant mangrove species revealed that
Avicennia marina could tolerate sedimentation rates of >6 cm year−1, while Bruguiera cylindrica tolerated sedimentation rates of 5 cm year−1 (total sediment depth = 25 cm) before dying, while Excoecaria agallocha and Lumnitzera racemosa performed intermediate. This outcome implied that in our situation A. marina and to lesser extent E. agallocha and L. racemosa could be more effective as biofilters than B. cylindrica, as they may survive the sedimentation longer in the disposal areas. Further studies on the impact of sedimentation and chemical
pollution of shrimp farm wastes on mangrove mortality and growth are required. 相似文献
18.
Andrew J. K. Conlan Trevelyan J. McKinley Katerina Karolemeas Ellen Brooks Pollock Anthony V. Goodchild Andrew P. Mitchell Colin P. D. Birch Richard S. Clifton-Hadley James L. N. Wood 《PLoS computational biology》2012,8(10)
The number of cattle herds placed under movement restrictions in Great Britain (GB) due to the suspected presence of bovine tuberculosis (bTB) has progressively increased over the past 25 years despite an intensive and costly test-and-slaughter control program. Around 38% of herds that clear movement restrictions experience a recurrent incident (breakdown) within 24 months, suggesting that infection may be persisting within herds. Reactivity to tuberculin, the basis of diagnostic testing, is dependent on the time from infection. Thus, testing efficiency varies between outbreaks, depending on weight of transmission and cannot be directly estimated. In this paper, we use Approximate Bayesian Computation (ABC) to parameterize two within-herd transmission models within a rigorous inferential framework. Previous within-herd models of bTB have relied on ad-hoc methods of parameterization and used a single model structure (SORI) where animals are assumed to become detectable by testing before they become infectious. We study such a conventional within-herd model of bTB and an alternative model, motivated by recent animal challenge studies, where there is no period of epidemiological latency before animals become infectious (SOR). Under both models we estimate that cattle-to-cattle transmission rates are non-linearly density dependent. The basic reproductive ratio for our conventional within-herd model, estimated for scenarios with no statutory controls, increases from 1.5 (0.26–4.9; 95% CI) in a herd of 30 cattle up to 4.9 (0.99–14.0) in a herd of 400. Under this model we estimate that 50% (33–67) of recurrent breakdowns in Britain can be attributed to infection missed by tuberculin testing. However this figure falls to 24% (11–42) of recurrent breakdowns under our alternative model. Under both models the estimated extrinsic force of infection increases with the burden of missed infection. Hence, improved herd-level testing is unlikely to reduce recurrence unless this extrinsic infectious pressure is simultaneously addressed. 相似文献
19.
20.
Katerina A. Christopoulos Susan Olender Andrea M. Lopez Helen-Maria Lekas Jessica Jaiswal Will Mellman Elvin Geng Kimberly A. Koester 《PLoS medicine》2015,12(8)