全文获取类型
收费全文 | 3556篇 |
免费 | 310篇 |
国内免费 | 2篇 |
专业分类
3868篇 |
出版年
2023年 | 17篇 |
2022年 | 27篇 |
2021年 | 62篇 |
2020年 | 33篇 |
2019年 | 50篇 |
2018年 | 93篇 |
2017年 | 79篇 |
2016年 | 104篇 |
2015年 | 168篇 |
2014年 | 208篇 |
2013年 | 269篇 |
2012年 | 305篇 |
2011年 | 262篇 |
2010年 | 174篇 |
2009年 | 161篇 |
2008年 | 226篇 |
2007年 | 209篇 |
2006年 | 220篇 |
2005年 | 199篇 |
2004年 | 205篇 |
2003年 | 192篇 |
2002年 | 175篇 |
2001年 | 39篇 |
2000年 | 24篇 |
1999年 | 36篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 29篇 |
1995年 | 32篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1960年 | 3篇 |
排序方式: 共有3868条查询结果,搜索用时 0 毫秒
81.
Tom Pinceel Bram Vanschoenwinkel Aline Waterkeyn Maarten P. M. Vanhove Adrian Pinder Brian V. Timms Luc Brendonck 《Hydrobiologia》2013,700(1):313-327
Australia, and especially South-Western Australia, is a diversity hotspot for large branchiopod crustaceans. A significant proportion of this diversity is found in the anostracans (Crustacea, Anostraca) and particularly in the diverse genus Branchinella with at least 34 species. Members of this genus are found exclusively in temporary aquatic habitats which are increasingly threatened by secondary salinization and other anthropogenic pressures. The development of adequate conservation strategies is therefore considered a priority. To define conservation units, however, thorough knowledge of the taxonomy and phylogenetic position of extant lineages is essential. We reconstructed a large scale phylogeny of the Australian Branchinella by analyzing the 16S mitochondrial gene of 31 presumed species, complemented with analysis of morphological structures holding taxonomic information. Results revealed the presence of at least three new cryptic species. On the other hand, some Branchinella lineages, surviving in environments subjected to contrasting selection regimes, appeared to be conspecific. This suggests substantial physiological plasticity or important adaptive variation present in some species, potentially enabling them to better cope with environmental change, such as secondary salinization. Overall, these results further illustrate the benefits of combining molecular markers and classic morphological taxonomy and phylogeny to assess biodiversity and define conservation units in cryptic groups. 相似文献
82.
Food security versus biodiversity protection: an example of land-sharing from East Africa 总被引:1,自引:0,他引:1
Jan Christian Habel Wolfgang W. Weisser Hilde Eggermont Luc Lens 《Biodiversity and Conservation》2013,22(6-7):1553-1555
The recent controversial debate on land-sharing versus land-sparing is clearly exemplified in the East African mountains, one of the most diverse biodiversity hotspots on our planet. In these areas, species richness is particularly concentrated in the mountain cloud forests which are surrounded by a sea of dry lowland savannas heavily encroached on by local communities. Sustainable land use practices in the lowlands, however, are necessary to safeguard the natural capital at higher elevations. The interdependence between sustainable land-use and conservation of biodiversity hotspots was underlined during a workshop held in the rural areas of Kenya, East Africa, early spring 2013. It was concluded that close links between livelihoods, natural capital and poverty remains a fundamental challenge in East Africa’s forest conservation efforts. 相似文献
83.
Arturo Roca-Rivada Cecilia Castelao Lucía L. Senin María O. Landrove Javier Baltar Ana Belén Crujeiras Luisa María Seoane Felipe F. Casanueva María Pardo 《PloS one》2013,8(4)
Exercise provides clear beneficial effects for the prevention of numerous diseases. However, many of the molecular events responsible for the curative and protective role of exercise remain elusive. The recent discovery of FNDC5/irisin protein that is liberated by muscle tissue in response to exercise might be an important finding with regard to this unsolved mechanism. The most striking aspect of this myokine is its alleged capacity to drive brown-fat development of white fat and thermogenesis. However, the nature and secretion form of this new protein is controversial. The present study reveals that rat skeletal muscle secretes a 25 kDa form of FNDC5, while the 12 kDa/irisin theoretical peptide was not detected. More importantly, this study is the first to reveal that white adipose tissue (WAT) also secretes FNDC5; hence, it may also behave as an adipokine. Our data using rat adipose tissue explants secretomes proves that visceral adipose tissue (VAT), and especially subcutaneous adipose tissue (SAT), express and secrete FNDC5. We also show that short-term periods of endurance exercise training induced FNDC5 secretion by SAT and VAT. Moreover, we observed that WAT significantly reduced FNDC5 secretion in fasting animals. Interestingly, WAT of obese animals over-secreted this hormone, which might suggest a type of resistance. Because 72% of circulating FNDC5/irisin was previously attributed to muscle secretion, our findings suggest a muscle-adipose tissue crosstalk through a regulatory feedback mechanism. 相似文献
84.
Sophie Pinel Jihane Mriouah Marc Vandamme Alicia Chateau Fran?ois Plénat Eric Guérin Luc Taillandier Valérie Bernier-Chastagner Jean-Louis Merlin Pascal Chastagner 《PloS one》2013,8(7)
In high-grade gliomas, the identification of patients that could benefit from EGFR inhibitors remains a challenge, hindering the use of these agents. Using xenografts models, we evaluated the antitumor effect of the combined treatment “gefitinib + radiotherapy” and aimed to identify the profile of responsive tumors. Expression of phosphorylated proteins involved in the EGFR-dependent signaling pathways was analyzed in 10 glioma models. We focused on three models of anaplastic oligodendrogliomas (TCG2, TCG3 and TCG4) harboring high levels of phospho-EGFR, phospho-AKT and phospho-MEK1. They were treated with gefitinib (GEF 75 mg/kg/day x 5 days/week, for 2 weeks) and/or fractionated radiotherapy (RT: 5x2Gy/week for 2 weeks). Our results showed that GEF and/or RT induced significant tumor growth delays. However, only the TCG3 xenografts were highly responsive to the combination GEF+RT, with ∼50% of tumor cure. Phosphoproteins analysis five days after treatment onset demonstrated in TCG3 xenografts, but not in TCG2 model, that the EGFR-dependent pathways were inhibited after GEF treatment. Moreover, TCG3-bearing mice receiving GEF monotherapy exhibited a transient beneficial therapeutic response, rapidly followed by tumor regrowth, along with a major vascular remodeling. Taken together, our data evoked an “EGFR-addictive” behavior for TCG3 tumors. This study confirms that combination of gefitinib with fractionated irradiation could be a potent therapeutic strategy for anaplastic oligodendrogliomas harboring EGFR abnormalities but this treatment seems mainly beneficial for “EGFR-addictive” tumors. Unfortunately, neither the usual molecular markers (EGFR amplification, PTEN loss) nor the basal overexpression of phosphoproteins were useful to distinguish this responsive tumor. Evaluating the impact of TKIs on the EGFR-dependent pathways during the treatment might be more relevant, and requires further validation. 相似文献
85.
86.
87.
Luc Villandre David A. Stephens Aurelie Labbe Huldrych F. Günthard Roger Kouyos Tanja Stadler The Swiss HIV Cohort Study 《PloS one》2016,11(2)
Background
Transmission patterns of sexually-transmitted infections (STIs) could relate to the structure of the underlying sexual contact network, whose features are therefore of interest to clinicians. Conventionally, we represent sexual contacts in a population with a graph, that can reveal the existence of communities. Phylogenetic methods help infer the history of an epidemic and incidentally, may help detecting communities. In particular, phylogenetic analyses of HIV-1 epidemics among men who have sex with men (MSM) have revealed the existence of large transmission clusters, possibly resulting from within-community transmissions. Past studies have explored the association between contact networks and phylogenies, including transmission clusters, producing conflicting conclusions about whether network features significantly affect observed transmission history. As far as we know however, none of them thoroughly investigated the role of communities, defined with respect to the network graph, in the observation of clusters.Methods
The present study investigates, through simulations, community detection from phylogenies. We simulate a large number of epidemics over both unweighted and weighted, undirected random interconnected-islands networks, with islands corresponding to communities. We use weighting to modulate distance between islands. We translate each epidemic into a phylogeny, that lets us partition our samples of infected subjects into transmission clusters, based on several common definitions from the literature. We measure similarity between subjects’ island membership indices and transmission cluster membership indices with the adjusted Rand index.Results and Conclusion
Analyses reveal modest mean correspondence between communities in graphs and phylogenetic transmission clusters. We conclude that common methods often have limited success in detecting contact network communities from phylogenies. The rarely-fulfilled requirement that network communities correspond to clades in the phylogeny is their main drawback. Understanding the link between transmission clusters and communities in sexual contact networks could help inform policymaking to curb HIV incidence in MSMs. 相似文献88.
Aline De Vleminck Koen Pardon Kim Beernaert Dirk Houttekier Robert Vander Stichele Luc Deliens 《PloS one》2016,11(4)
ObjectivesTo explore how GPs conceptualise advance care planning (ACP), based on their experiences with ACP in their practice.MethodsFive focus groups were held with 36 GPs. Discussions were analysed using a constant comparative method.ResultsFour overarching themes in the conceptualisations of ACP were discerned: (1) the organisation of professional care required to meet patients’ needs, (2) the process of preparing for death and discussing palliative care options, (3) the discussion of care goals and treatment decisions, (4) the completion of advance directives. Within these themes, ACP was both conceptualised in terms of content of ACP and/or in terms of tasks for the GP. A specific task that was mentioned throughout the discussion of the four different themes was (5) the task of actively initiating ACP by the GP versus passively waiting for patients’ initiation.ConclusionsThis study illustrates that GPs have varying conceptualisations of ACP, of which some are more limited to specific aspects of ACP. A shared conceptualisation and agreement on the purpose and goals of ACP is needed to ensure successful implementation, as well as a systematic integration of ACP in routine practice that could lead to a better uptake of all the important elements of ACP. 相似文献
89.
90.