全文获取类型
收费全文 | 5615篇 |
免费 | 390篇 |
国内免费 | 2篇 |
出版年
2023年 | 37篇 |
2022年 | 72篇 |
2021年 | 142篇 |
2020年 | 101篇 |
2019年 | 113篇 |
2018年 | 161篇 |
2017年 | 145篇 |
2016年 | 209篇 |
2015年 | 300篇 |
2014年 | 281篇 |
2013年 | 409篇 |
2012年 | 471篇 |
2011年 | 463篇 |
2010年 | 290篇 |
2009年 | 235篇 |
2008年 | 341篇 |
2007年 | 311篇 |
2006年 | 280篇 |
2005年 | 255篇 |
2004年 | 219篇 |
2003年 | 217篇 |
2002年 | 184篇 |
2001年 | 72篇 |
2000年 | 64篇 |
1999年 | 55篇 |
1998年 | 40篇 |
1997年 | 42篇 |
1996年 | 31篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 34篇 |
1992年 | 31篇 |
1991年 | 18篇 |
1990年 | 34篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1974年 | 20篇 |
1973年 | 9篇 |
1966年 | 7篇 |
排序方式: 共有6007条查询结果,搜索用时 62 毫秒
991.
Soňa Kucharíková Patrick Van Dijck Magdaléna Lisalová Helena Bujdáková 《Central European Journal of Biology》2010,5(3):318-323
In the last decade, infections caused by Candida glabrata have become more serious, particularly due to its decreased susceptibility to azole derivatives and its ability to form biofilm.
Here we studied the resistance profile of 42 C. glabrata clinical isolates to different azoles, amphotericin B and echinocandins. This work was also focused on the ability to form
biofilm which plays a role in the development of antifungal resistance. The minimal inhibitory concentration testing to antifungal
agents was performed according to the CLSI (Clinical and Laboratory Standards Institute) M27-A3 protocol. Quantification of
biofilm was done by XTT reduction assay. All C. glabrata clinical isolates were resistant to itraconazole and sixteen also showed resistance to fluconazole. All isolates remained
susceptible to voriconazole. Amphotericin B was efficient in a concentration range of 0.125–1 mg/L. The most effective antifungal
agents were micafungin and caspofungin with the MIC100 values of ≤0.0313–0.125 mg/L. Low concentrations of these agents reduced biofilm formation as well. Our results show that
resistance of different C. glabrata strains is azole specific and therefore a single azole resistance cannot be assumed to indicate general azole resistance.
Echinocandins proved to have very high efficacy against clinical C. glabrata strains including those with ability to form biofilm. 相似文献
992.
Background
γ-Secretase is an intramembrane aspartyl protease whose cleavage of the amyloid precursor protein (APP) generates the amyloid β-peptide (Aβ) and the APP intracellular domain. Aβ is widely believed to have a causative role in Alzheimer''s disease pathogenesis, and therefore modulation of γ-secretase activity has become a therapeutic goal. Besides APP, more than 50 substrates of γ-secretase with different cellular functions during embryogenesis as well as adulthood have been revealed. Prior to γ-secretase cleavage, substrates are ectodomain shedded, producing membrane bound C-terminal fragments (CTFs).Principal Findings
Here, we investigated γ-secretase cleavage of five substrates; APP, Notch1, N-cadherin, ephrinB and p75 neurotrophin receptor (p75-NTR) in membranes isolated from embryonic, young or old adult rat brain by analyzing the release of the corresponding intracellular domains (ICDs) or Aβ40 by western blot analysis and ELISA respectively. The highest levels of all ICDs and Aβ were produced by embryonic membranes. In adult rat brain only cleavage of APP and Notch1 could be detected and the Aβ40 and ICD production from these substrates was similar in young and old adult rat brain. The CTF levels of Notch1, N-cadherin, ephrinB and p75-NTR were also clearly decreased in the adult brain compared to embryonic brain, whereas the APP CTF levels were only slightly decreased.Conclusions
In summary our data suggests that γ-secretase dependent ICD production is down-regulated in the adult brain compared to embryonic brain. In addition, the present approach may be useful for evaluating the specificity of γ-secretase inhibitors. 相似文献993.
Keep wetlands wet: the myth of sustainable development of tropical peatlands – implications for policies and management
下载免费PDF全文
![点击此处可从《Global Change Biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stephanie Evers Catherine M. Yule Rory Padfield Patrick O'Reilly Helena Varkkey 《Global Change Biology》2017,23(2):534-549
Pristine tropical peat swamp forests (PSFs) represent a unique wetland ecosystem of distinctive hydrology which support unique biodiversity and globally significant stores of soil carbon. Yet in Indonesia and Malaysia, home to 56% of the world's tropical peatland, they are subject to considerable developmental pressures, including widespread drainage to support agricultural needs. In this article, we review the ecology behind the functioning and ecosystem services provided by PSFs, with a particular focus on hydrological processes as well as the role of the forest itself in maintaining those services. Drawing on this, we review the suitability of current policy frameworks and consider the efficacy of their implementation. We suggest that policies in Malaysia and Indonesia are often based around the narrative of oil palm and other major monocrops as drivers of prosperity and development. However, we also argue that this narrative is also being supported by a priori claims concerning the possibility of sustainability of peat swamp exploitation via drainage‐based agriculture through the adherence to best management practices. We discuss how this limits their efficacy, uptake and the political will towards enforcement. Further, we consider how both narratives (prosperity and sustainability) clearly exclude important considerations concerning the ecosystem value of tropical PSFs which are dependent on their unimpacted hydrology. Current research clearly shows that the actual debate should be focused not on how to develop drainage‐based plantations sustainably, but on whether the sustainable conversion to drainage‐based systems is possible at all. 相似文献
994.
995.
E. P. Silva Jr. L. S. Borges C. Mendes-da-Silva S. M. Hirabara 《Free radical research》2017,51(3):281-293
Reactive species have great importance in sports performance, once they can directly regulate energy production, muscular contraction, inflammation, and fatigue. Therefore, the redox control is essential for athletes’ performance. Studies demonstrated that l-arginine has an important role in the synthesis of urea, cell growth and production of nitric oxide, moreover, there are indications that it is also able to induce benefits to muscle antioxidant system through the upregulation of some antioxidant enzymes, and by inhibiting some pathways of reactive species production. Therefore, the aim of this study was to evaluate the effects of l-arginine supplementation on performance and oxidative stress of male rats (trained or not), submitted to a single session of high intensity exercise. Forty male Wistar rats were divided into four groups, control (C), control+l-arginine (C?+?A), trained (T), and trained+l-arginine (T?+?A). The aerobic training was conducted for 8 weeks. Data of maximum speed and time from tests were used as indicators of performance. Variables related to oxidative stress and antioxidant system were also evaluated. Aerobic training was capable to induce enhancements on animals’ exercise performance and on their redox state. Additionally, supplementation improved rats’ physical performance on both groups, control and trained. Different improvements between groups on the antioxidant capacity were observed. Nevertheless, considering the ergogenic effect of l-arginine and the lack of all positive adaptations promoted by the exercise training, untrained animals may be more exposed to oxidative damages after the practice of intense exercises. 相似文献
996.
997.
998.
999.
Tina Christmann Bruno H. P. Rosado Guillaume Delhaye Ilaíne S. Matos Julia S. Drummond Helena L. Roland Yan C. Moraes Imma Oliveras Menor 《Ecology and evolution》2021,11(15):10164
AimsAmidst the Campos de Altitude (Highland Grasslands) in the Brazilian Atlantic Forest, woody communities grow either clustered in tree islands or interspersed within the herbaceous matrix. The functional ecology, diversity, and biotic processes shaping these plant communities are largely unstudied. We characterized the functional assembly and diversity of these tropical montane woody communities and investigated how they fit within Grime''s CSR (C—competitor, S—stress‐tolerant, R—ruderal) scheme, what functional trade‐offs they exhibit, and how traits and functional diversity vary in response to bamboo presence/absence.MethodsTo characterize the functional composition of the community, we sampled five leaf traits and wood density along transects covering the woody communities both inside tree islands and outside (i.e., isolated woody plants in the grasslands community). Then, we used Mann–Whitney test, t test, and variation partitioning to determine the effects of inside versus outside tree island and bamboo presence on community‐weighted means, woody species diversity, and functional diversity.ResultsWe found a general SC/S strategy with drought‐related functional trade‐offs. Woody plants in tree islands had more acquisitive traits than those within the grasslands. Trait variation was mostly taxonomically than spatially driven, and species composition varied between inside and outside tree islands. Leaf thickness, wood density, and foliar water uptake were unrelated to CSR strategies, suggesting independent trait dimensions and multiple drought‐coping strategies within the predominant S strategy. Islands with bamboo presence showed lower Simpson diversity, lower functional dispersion, lower foliar water uptake, and greater leaf thickness than in tree islands without bamboo.ConclusionsThe observed functional assembly hints toward large‐scale environmental abiotic filtering shaping a stress‐tolerant community strategy, and small‐scale biotic interactions driving small‐scale trait variation. We recommend experimental studies with fire, facilitation treatments, ecophysiological and recruitment traits to elucidate on future tree island expansion and community response to climate change. 相似文献
1000.
José Ivo Baldani Veronica Massena Reis Sandy Sampaio Videira Lúcia Helena Boddey Vera Lúcia Divan Baldani 《Plant and Soil》2014,384(1-2):413-431