全文获取类型
收费全文 | 291篇 |
免费 | 15篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 23篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 20篇 |
2009年 | 9篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
排序方式: 共有306条查询结果,搜索用时 15 毫秒
1.
Rosa Agudo Ciro Rico Carles Vilà Fernando Hiraldo José Antonio Donázar 《BMC evolutionary biology》2010,10(1):384
Background
Anthropogenic habitat modifications have led to the extinction of many species and have favoured the expansion of others. Nonetheless, the possible role of humans as a diversifying force in vertebrate evolution has rarely been considered, especially for species with long generation times. We examine the influence that humans have had on the colonization and phenotypic and genetic differentiation of an insular population of a long-lived raptor species, the Egyptian vulture (Neophron percnopterus). 相似文献2.
3.
Torella D Leosco D Indolfi C Curcio A Coppola C Ellison GM Russo VG Torella M Li Volti G Rengo F Chiariello M 《American journal of physiology. Heart and circulatory physiology》2004,287(6):H2850-H2860
Many older patients, because of their high prevalence of coronary artery disease, are candidates for percutaneous coronary interventions (PCI), but the effects of vascular aging on restenosis after PCI are not yet well understood. Balloon injury to the right carotid artery was performed in adult and old rats. Vascular smooth muscle cell (VSMC) proliferation, apoptotic cell death, together with Akt induction, telomerase activity, p27kip1, and endothelial nitric oxide synthase (eNOS) expression was assessed in isolated arteries. Neointima hyperplasia and vascular remodeling along with endothelial cell regeneration were also measured after balloon injury. Arteries isolated from old rats exhibited a significant reduction of VSMC proliferation and an increase in apoptotic death after balloon injury when compared with adult rats. In the vascular wall of adult rats, balloon dilation induced Akt phosphorylation, and this was barely present in old rats. In arteries from old rats, Akt-modulated cell cycle check points like telomerase activity and p27kip1 expression were decreased and increased, respectively, compared with adults. After balloon injury, old rats showed a significant reduction of neointima formation and an increased vascular negative remodeling compared with adults. These results were coupled by a marked delay in endothelial regeneration in aged rats, partially mediated by a decreased eNOS expression and phosphorylation. Interestingly, chronic administration of L-arginine prevented negative remodeling and improved reendothelialization after balloon injury in aged animals. A decreased neointimal proliferation, an impaired endothelial regeneration, and an increase in vascular remodeling after balloon injury were observed in aged animals. The molecular mechanisms underlying these responses seem to be a reduced Akt and eNOS activity. 相似文献
4.
5.
Michael Abberton Jacqueline Batley Alison Bentley John Bryant Hongwei Cai James Cockram Antonio Costa de Oliveira Leland J. Cseke Hannes Dempewolf Ciro De Pace David Edwards Paul Gepts Andy Greenland Anthony E. Hall Robert Henry Kiyosumi Hori Glenn Thomas Howe Stephen Hughes Mike Humphreys David Lightfoot Athole Marshall Sean Mayes Henry T. Nguyen Francis C. Ogbonnaya Rodomiro Ortiz Andrew H. Paterson Roberto Tuberosa Babu Valliyodan Rajeev K. Varshney Masahiro Yano 《Plant biotechnology journal》2016,14(4):1095-1098
Agriculture is now facing the ‘perfect storm’ of climate change, increasing costs of fertilizer and rising food demands from a larger and wealthier human population. These factors point to a global food deficit unless the efficiency and resilience of crop production is increased. The intensification of agriculture has focused on improving production under optimized conditions, with significant agronomic inputs. Furthermore, the intensive cultivation of a limited number of crops has drastically narrowed the number of plant species humans rely on. A new agricultural paradigm is required, reducing dependence on high inputs and increasing crop diversity, yield stability and environmental resilience. Genomics offers unprecedented opportunities to increase crop yield, quality and stability of production through advanced breeding strategies, enhancing the resilience of major crops to climate variability, and increasing the productivity and range of minor crops to diversify the food supply. Here we review the state of the art of genomic‐assisted breeding for the most important staples that feed the world, and how to use and adapt such genomic tools to accelerate development of both major and minor crops with desired traits that enhance adaptation to, or mitigate the effects of climate change. 相似文献
6.
Plant and Soil - The ecological study of root systems lags behind the understanding of the aboveground components of plant communities, mainly due to methodological challenges. As ecological root... 相似文献
7.
Life within the soil is vital for maintaining life on Earth due to the numerous ecosystem services that it provides. However, there is evidence that pressures on the soil biota are increasing which may undermine some of these ecosystem services. Current levels of belowground biodiversity are relatively poorly known, and so no benchmark exists by which to measure possible future losses of biodiversity. Furthermore, the relative risk that each type of anthropogenic pressures places on the soil biota remains unclear. Potential threats to soil biodiversity were calculated through the use of a composite score produced from data collected from 20 international experts using the budget allocation methodology. This allowed relative weightings to be given to each of the identified pressures for which data were available in the European Soil Data Centre (ESDC). A total of seven different indicators were used for calculating the composite scores. These data were applied through a model using ArcGIS to produce a spatial analysis of composite pressures on soil biodiversity at the European scale. The model highlights the variation in the composite result of the potential threats to soil biodiversity. A sensitivity analysis demonstrated that the intensity of land exploitation, both in terms of agriculture and use intensity, as well as in terms of land‐use dynamics, were the main factors applying pressure on soil biodiversity. It is important to note that the model should not be viewed as an estimate of the current level of soil biodiversity in Europe, but as an estimate of pressures that are currently being exerted. The results obtained should be seen as a starting point for further investigation on this relatively unknown issue and demonstrate the utility of this type of model which may be applied to other regions and scales. 相似文献
8.
Zyanya Reyes-Castillo Ana Laura Pereira-Suárez Claudia Azucena Palafox-Sanchez Héctor Rangel-Villalobos Ciro Estrada-Chávez Edith Oregón-Romero Luis Ignacio Angel-Chávez Salvador Muñoz-Barrios Miriam Ruth Bueno-Topete José Francisco Muñoz-Valle 《Gene》2013
Prolactin (PRL) is a hormone–cytokine that has been involved in autoimmunity due to its immunoregulatory and lymphoproliferative effects. It is produced by various extrapituitary sites including immune cells, under control of a superdistal promoter that contains a single nucleotide polymorphism − 1149 G/T previously associated with rheumatoid arthritis (RA) susceptibility in European population. The aim of this study was to investigate the association of the extrapituitary PRL − 1149 G/T promoter polymorphism with clinical parameters, clinical activity and disability indices in RA patients from Western Mexico and to analyze the PRL mRNA expression according to the PRL − 1149 G/T promoter polymorphism in total leucocytes from RA patients and controls. We conducted a case–control study that included 258 RA patients and 333 control subjects (CS). The DNA samples were genotyped using the PCR–RFLP method and the PRL mRNA expression was determined by quantitative real time PCR. PRL serum levels and antibodies to cyclic citrullinated peptides (anti-CCP) were measured with ELISA. We found significant differences in the genotype (p = 0.022) and allelic (p = 0.046) distribution of the polymorphism between RA patients and control subjects. According to the dominant genetic model, there is an association between the T allele (GT + TT genotypes) and decreased RA susceptibility in comparison to the G allele carriers (GG genotype) (OR 0.64, 95% CI 0.45–0.92; p = 0.011). The T allele carriers (GT + TT genotypes) had lower titers of anti-CCP antibodies in comparison to the G allele carriers (GG genotype) (median, 66 U/mL vs. 125 U/mL; p = 0.03). Furthermore, the GG homozygotes had higher PRL mRNA expression in comparison to the GT heterozygotes, and this latter with respect to the TT homozygotes, in both groups (RA: 1 > 0.72 > 0.19; CS: 1 > 0.54 > 0.28). However, PRL serum levels were similar in both groups. Our results suggest that the PRL − 1149 T allele is a genetic marker for decreased RA susceptibility and is associated with lower titers of anti-CCP antibodies in Mexican population. We also suggest influence of genotype upon PRL mRNA expression. 相似文献
9.
10.
Juan P. de-Torres Jose M. Marín Víctor Pinto-Plata Miguel Divo Pablo Sanchez-Salcedo Jorge Zagaceta Javier J. Zulueta Juan Berto Carlos Cabrera Bartolome R. Celli Ciro Casanova 《PloS one》2016,11(4)
BackgroundThe Global Initiative for Obstructive Lung Diseases (GOLD) defines COPD as a disease that is usually progressive. GOLD also provides a spirometric classification of airflow limitation. However, little is known about the long-term changes of patients in different GOLD grades.ObjectiveExplore the proportion and characteristics of COPD patients that change their spirometric GOLD grade over long-term follow-up.MethodsPatients alive for at least 8 years since recruitment and those who died with at least 4 years of repeated spirometric measurements were selected from the BODE cohort database. We purposely included the group of non survivors to avoid a “survival selection” bias. The proportion of patients that had a change (improvement or worsening) in their spirometric GOLD grading was calculated and their characteristics compared with those that remained in the same grade.ResultsA total of 318 patients were included in the survivor and 217 in the non-survivor groups. Nine percent of survivors and 11% of non survivors had an improvement of at least one GOLD grade. Seventy one percent of survivors and non-survivors remained in the same GOLD grade. Those that improved had a greater degree of airway obstruction at baseline.ConclusionsIn this selected population of COPD patients, a high proportion of patients remained in the same spirometric GOLD grade or improved in a long-term follow-up. These findings suggest that once diagnosed, COPD is usually a non-progressive disease. 相似文献