全文获取类型
收费全文 | 3692篇 |
免费 | 339篇 |
国内免费 | 5篇 |
出版年
2023年 | 17篇 |
2022年 | 26篇 |
2021年 | 85篇 |
2020年 | 49篇 |
2019年 | 69篇 |
2018年 | 91篇 |
2017年 | 73篇 |
2016年 | 136篇 |
2015年 | 199篇 |
2014年 | 219篇 |
2013年 | 284篇 |
2012年 | 302篇 |
2011年 | 290篇 |
2010年 | 191篇 |
2009年 | 160篇 |
2008年 | 199篇 |
2007年 | 205篇 |
2006年 | 196篇 |
2005年 | 205篇 |
2004年 | 195篇 |
2003年 | 178篇 |
2002年 | 164篇 |
2001年 | 38篇 |
2000年 | 31篇 |
1999年 | 39篇 |
1998年 | 54篇 |
1997年 | 32篇 |
1996年 | 20篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 24篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4036条查询结果,搜索用时 31 毫秒
1.
2.
Tom P. Moorhouse Cecilia A. L. Dahlsj? Sandra E. Baker Neil C. D'Cruze David W. Macdonald 《PloS one》2015,10(10)
Tourism accounts for 9% of global GDP and comprises 1.1 billion tourist arrivals per annum. Visits to wildlife tourist attractions (WTAs) may account for 20–40% of global tourism, but no studies have audited the diversity of WTAs and their impacts on the conservation status and welfare of subject animals. We scored these impacts for 24 types of WTA, visited by 3.6–6 million tourists per year, and compared our scores to tourists’ feedback on TripAdvisor. Six WTA types (impacting 1,500–13,000 individual animals) had net positive conservation/welfare impacts, but 14 (120,000–340,000 individuals) had negative conservation impacts and 18 (230,000–550,000 individuals) had negative welfare impacts. Despite these figures only 7.8% of all tourist feedback on these WTAs was negative due to conservation/welfare concerns. We demonstrate that WTAs have substantial negative effects that are unrecognised by the majority of tourists, suggesting an urgent need for tourist education and regulation of WTAs worldwide. 相似文献
3.
4.
Emily Olfson Catherine E. Cottrell Nicholas O. Davidson Christina A. Gurnett Jonathan W. Heusel Nathan O. Stitziel Li-Shiun Chen Sarah Hartz Rakesh Nagarajan Nancy L. Saccone Laura J. Bierut 《PloS one》2015,10(9)
The American College of Medical Genetics and Genomics (ACMG) recommends that clinical sequencing laboratories return secondary findings in 56 genes associated with medically actionable conditions. Our goal was to apply a systematic, stringent approach consistent with clinical standards to estimate the prevalence of pathogenic variants associated with such conditions using a diverse sequencing reference sample. Candidate variants in the 56 ACMG genes were selected from Phase 1 of the 1000 Genomes dataset, which contains sequencing information on 1,092 unrelated individuals from across the world. These variants were filtered using the Human Gene Mutation Database (HGMD) Professional version and defined parameters, appraised through literature review, and examined by a clinical laboratory specialist and expert physician. Over 70,000 genetic variants were extracted from the 56 genes, and filtering identified 237 variants annotated as disease causing by HGMD Professional. Literature review and expert evaluation determined that 7 of these variants were pathogenic or likely pathogenic. Furthermore, 5 additional truncating variants not listed as disease causing in HGMD Professional were identified as likely pathogenic. These 12 secondary findings are associated with diseases that could inform medical follow-up, including cancer predisposition syndromes, cardiac conditions, and familial hypercholesterolemia. The majority of the identified medically actionable findings were in individuals from the European (5/379) and Americas (4/181) ancestry groups, with fewer findings in Asian (2/286) and African (1/246) ancestry groups. Our results suggest that medically relevant secondary findings can be identified in approximately 1% (12/1092) of individuals in a diverse reference sample. As clinical sequencing laboratories continue to implement the ACMG recommendations, our results highlight that at least a small number of potentially important secondary findings can be selected for return. Our results also confirm that understudied populations will not reap proportionate benefits of genomic medicine, highlighting the need for continued research efforts on genetic diseases in these populations. 相似文献
5.
There are over one million described invertebrate species on Earth, the majority of which are likely to inhabit the highly biodiverse rain forests around the equator. These are some of the most vulnerable ecosystems on Earth due to the pressures of deforestation and climate change with many of their inhabitants at risk of extinction. Invertebrates play a major role in ecosystem functioning from decomposition and nutrient cycling to herbivory and pollination; however, while our understanding of these roles is improving, we are far from being able to predict the consequences of further deforestation, climate change, and biodiversity loss due to the lack of comparative data and the high proportion of species which remain to be discovered. As we move into an era of increased pressure on old-growth habitats and biodiversity, it is imperative that we understand how changes to invertebrate communities, and the extinction of species, affect ecosystems. Innovative and comprehensive methods that approach these issues are needed. Here, we highlight priorities for future tropical terrestrial invertebrate research such as the efficiency of sustainable land management, exploration of innovative methods for better understanding of invertebrate ecology and behavior, and quantifying the role of invertebrates in ecosystem functioning. 相似文献
6.
Cecilia Polacow Herzog 《Landscape and Ecological Engineering》2016,12(1):141-150
The city of Rio de Janeiro now covers what was formerly coastal Atlantic rainforest. Native biodiversity has been lost from most of the metropolitan area due to changes in land use, introduction of exotic species, and influence of foreign designs in public and private parks and gardens. This paper presents a multifunctional green infrastructure planning proposal to protect and regenerate native biodiversity in the last remaining natural ecosystem fragments in a watershed within the city’s limits. The proposal is based on social–ecological assessments and analyses. The watershed contains an extensive mangrove remnant surrounded by a protected massif partially covered by coastal Atlantic rainforest and is one of the very last productive landscapes where residents experience a strong sense of place. The strategy is to reconcile urban development with environmental achievements to conserve existing ecosystem patches, which will be connected by way of riparian corridors and other open spaces, such as streets, private yards and public areas, by using native species and ecological design. The green infrastructure framework is planned at the watershed scale. On a neighborhood and local scale, the plan is to promote public participation, develop new ecological aesthetics, encourage the planting of native species, and establish an innovative circulation system within a low-impact design framework to achieve various abiotic, biotic, and cultural goals. In addition to the economic benefits, accessible food production, rural tourism and ecotourism have the potential to unite people and nature within the city. 相似文献
7.
Cecilia Shiskin 《BMJ (Clinical research ed.)》1950,1(4668):1490-1491
8.
Seabirds are affected by changes in the marine ecosystem. The influence of climatic factors on marine food webs can be reflected in long-term seabird population changes. We modelled the survival and recruitment of the Mediterranean storm petrel (Hydrobates pelagicus melitensis) using a 21-year mark-recapture dataset involving almost 5000 birds. We demonstrated a strong influence of prebreeding climatic conditions on recruitment age and of rainfall and breeding period conditions on juvenile survival. The results suggest that the juvenile survival rate of the Mediterranean subspecies may not be negatively affected by the predicted features of climate change, i.e., warmer summers and lower rainfall. Based on considerations of winter conditions in different parts of the Mediterranean, we were able to draw inferences about the wintering areas of the species for the first time. 相似文献
9.
Cathrine Laustrup M?ller Rasmus Kj?bsted Pablo J. Enriori Thomas Elbenhardt Jensen Cecilia Garcia-Rudaz Sara A. Litwak Kirsten Raun J?rgen Wojtaszewski Birgitte Schjellerup Wulff Michael A. Cowley 《PloS one》2016,11(7)
The melanocortin system includes five G-protein coupled receptors (family A) defined as MC1R-MC5R, which are stimulated by endogenous agonists derived from proopiomelanocortin (POMC). The melanocortin system has been intensely studied for its central actions in body weight and energy expenditure regulation, which are mainly mediated by MC4R. The pituitary gland is the source of various POMC-derived hormones released to the circulation, which raises the possibility that there may be actions of the melanocortins on peripheral energy homeostasis. In this study, we examined the molecular signaling pathway involved in α-MSH-stimulated glucose uptake in differentiated L6 myotubes and mouse muscle explants. In order to examine the involvement of AMPK, we investigate α-MSH stimulation in both wild type and AMPK deficient mice. We found that α-MSH significantly induces phosphorylation of TBC1 domain (TBC1D) family member 1 (S237 and T596), which is independent of upstream PKA and AMPK. We find no evidence to support that α-MSH-stimulated glucose uptake involves TBC1D4 phosphorylation (T642 and S704) or GLUT4 translocation. 相似文献
10.
RNA and protein synthesis by sterile rat-liver mitochondria 总被引:2,自引:0,他引:2