全文获取类型
收费全文 | 1438篇 |
免费 | 151篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 31篇 |
2020年 | 22篇 |
2019年 | 23篇 |
2018年 | 25篇 |
2017年 | 32篇 |
2016年 | 57篇 |
2015年 | 89篇 |
2014年 | 107篇 |
2013年 | 103篇 |
2012年 | 136篇 |
2011年 | 108篇 |
2010年 | 76篇 |
2009年 | 55篇 |
2008年 | 96篇 |
2007年 | 91篇 |
2006年 | 77篇 |
2005年 | 61篇 |
2004年 | 58篇 |
2003年 | 44篇 |
2002年 | 58篇 |
2001年 | 16篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有1589条查询结果,搜索用时 15 毫秒
991.
Felix R. Kayigamba Mirjam I. Bakker Judith Lammers Veronicah Mugisha Emmanuel Bagiruwigize Anita Asiimwe Maarten F. Schim. van der Loeff 《PloS one》2014,9(4)
Introduction
Routine provider-initiated HIV testing and counselling (PITC) may increase HIV testing rates, but whether PITC is acceptable to health facility (HF) attendees is unclear. In the course of a PITC intervention study in Rwanda, we assessed the acceptability of PITC, reasons for being or not being tested and factors associated with HIV testing.Methods
Attendees were systematically interviewed in March 2009 as they left the HF, regarding knowledge and acceptability of PITC, history of testing and reasons for being tested or not. Subsequently, PITC was introduced in 6 of the 8 HFs and a second round of interviews was conducted. Independent factors associated with testing were analysed using logistic regression. Randomly selected health care workers (HCWs) were also interviewed.Results
1772 attendees were interviewed. Over 95% agreed with the PITC policy, both prior to and after implementation of PITC policy. The most common reasons for testing were the desire to know one’s HIV status and having been offered an HIV test by an HCW. The most frequent reasons for not being tested were known HIV status and test not being offered. In multivariable analysis, PITC, age ≥15 years, and not having been previously tested were factors significantly associated with testing. Although workload was increased by PITC, HIV testing rates increased and HCWs overwhelmingly supported the policy.Conclusion
Among attendees and HCWs in Rwandan clinics, the acceptability of PITC was very high. PITC appeared to increase testing rates and may be helpful in prevention and early access to treatment. 相似文献992.
Maarten C. Eisma Henk A. W. Schut Margaret S. Stroebe Jan van den Bout Wolfgang Stroebe Paul A. Boelen 《PloS one》2014,9(8)
Rumination is a risk factor in adjustment to bereavement. It is associated with and predicts psychopathology after loss. Yet, the function of rumination in bereavement remains unclear. In the past, researchers often assumed rumination to be a maladaptive confrontation process. However, based on cognitive avoidance theories of worry in generalised anxiety disorder (GAD) and rumination after post-traumatic stress disorder (PTSD), others have suggested that rumination may serve to avoid painful aspects of the loss, thereby contributing to complicated grief. To examine if rumination is linked with loss avoidance, an eye-tracking study was conducted with 54 bereaved individuals (27 high and 27 low ruminators). On 24 trials, participants looked for 10 seconds at a picture of the deceased and a picture of a stranger, randomly combined with negative, neutral or loss-related words. High ruminators were expected to show initial vigilance followed by subsequent disengagement for loss stimuli (i.e., picture deceased with a loss word) in the first 1500 ms. Additionally, we expected high ruminators to avoid these loss stimuli and to show attentional preference for non-loss-related negative stimuli (i.e., picture stranger with a negative word) on longer exposure durations (1500–10000 ms). Contrary to expectations, we found no evidence for an effect of rumination on vigilance and disengagement of loss stimuli in the first 1500 ms. However, in the 1500–10000 ms interval, high ruminators showed shorter gaze times for loss stimuli and longer gaze times for negative (and neutral) non-loss-related stimuli, even when controlling for depression and complicated grief symptom levels. Effects of rumination on average fixation times mirrored these findings. This suggests that rumination and loss avoidance are closely associated. A potential clinical implication is that rumination and grief complications after bereavement may be reduced through the use of exposure and acceptance-based therapeutic techniques. 相似文献
993.
Stoichiometric homeostasis is the ability of an organism to keep its body chemical composition constant, despite varying inputs. Stoichiometric homeostasis therefore constrains the metabolic needs of consumers which in turn often feed on resources not matching these requirements. In a broader context, homeostasis also relates to the capacity of an organism to maintain other biological parameters (e.g. body temperature) at a constant level over ambient environmental variations. Unfortunately, there are discrepancies in the literature and ecological and physiological definitions of homeostasis are disparate and partly contradictory. Here, we address this matter by reviewing the existing knowledge considering two distinct groups, regulators and conformers and, based on examples of thermo- and osmoregulation, we propose a new approach to stoichiometric homeostasis, unifying ecological and physiological concepts. We suggest a simple and precise graphical way to identify regulators and conformers: for any given biological parameter (e.g. nutrient stoichiometry, temperature), a sigmoidal relation between internal and external conditions can be observed for conformers while an inverse sigmoidal response is characteristic of regulators. This new definition and method, based on well-studied physiological mechanisms, unifies ecological and physiological approaches and is a useful tool for understanding how organisms are affected by and affect their environment. 相似文献
994.
Michael Brunner Stephen Wachtel Marijo Kent Maarten Drost Alan Goff Keith Betteridge 《Differentiation; research in biological diversity》1987,35(2):122-125
A newly developed enzyme-linked immunosorbent assay (ELISA) was applied for studying H-Y antigen in buffaloes, cattle, horses and humans. A monoclonal H-Y antibody was absorbed with cells from males or females and was then tested against fluid samples known to contain soluble H-Y antigen. In this system, positive absorption manifested itself by a fall in optical density relative to the optical density scored using unabsorbed antibody; this finding signified the presence of H-Y in the absorbing cells. In each of the four species, the fall in optical density was pronounced after absorption with male cells, but some decrease was also evident after absorption with female cells, indicating a degree of nonspecific attachment of the antibody. 相似文献
995.
996.
Celia J. Vogel Marjon A. Smit Gianluca Maddalo Patricia A. Possik Rolf W. Sparidans Sjoerd H. van der Burg Els M. Verdegaal Albert J. R. Heck Ahmed A. Samatar Jos H. Beijnen A. F. Maarten Altelaar Daniel S. Peeper 《Pigment cell & melanoma research》2015,28(3):307-317
No effective targeted therapy is currently available for NRAS mutant melanoma. Experimental MEK inhibition is rather toxic and has only limited efficacy in clinical trials. At least in part, this is caused by the emergence of drug resistance, which is commonly seen for single agent treatment and shortens clinical responses. Therefore, there is a dire need to identify effective companion drug targets for NRAS mutant melanoma. Here, we show that at concentrations where single drugs had little effect, ROCK inhibitors GSK269962A or Fasudil, in combination with either MEK inhibitor GSK1120212 (Trametinib) or ERK inhibitor SCH772984 cooperatively caused proliferation inhibition and cell death in vitro. Simultaneous inhibition of MEK and ROCK caused induction of BimEL, PARP, and Puma, and hence apoptosis. In vivo, MEK and ROCK inhibition suppressed growth of established tumors. Our findings warrant clinical investigation of the effectiveness of combinatorial targeting of MAPK/ERK and ROCK in NRAS mutant melanoma. 相似文献
997.
Zoonotic pathogens that cause devastating morbidity and mortality in humans may be relatively harmless in their natural reservoir hosts. The tick-borne bacterium Borrelia burgdorferi causes Lyme disease in humans but few studies have investigated whether this pathogen reduces the fitness of its reservoir hosts under natural conditions. We analyzed four years of capture-mark-recapture (CMR) data on a population of white-footed mice, Peromyscus leucopus, to test whether B. burgdorferi and its tick vector affect the survival of this important reservoir host. We used a multi-state CMR approach to model mouse survival and mouse infection rates as a function of a variety of ecologically relevant explanatory factors. We found no effect of B. burgdorferi infection or tick burden on the survival of P. leucopus. Our estimates of the probability of infection varied by an order of magnitude (0.051 to 0.535) and were consistent with our understanding of Lyme disease in the Northeastern United States. B. burgdorferi establishes a chronic avirulent infection in their rodent reservoir hosts because this pathogen depends on rodent mobility to achieve transmission to its sedentary tick vector. The estimates of B. burgdorferi infection risk will facilitate future theoretical studies on the epidemiology of Lyme disease. 相似文献
998.
999.
Sophie Graefe Dominique Dufour Maarten van Zonneveld Fernando Rodriguez Alonso Gonzalez 《Biodiversity and Conservation》2013,22(2):269-300
Peach palm (Bactris gasipaes) is a multi-purpose palm tree native to tropical Latin America, which is predominantly cultivated by smallholders in agroforestry systems. The fruits are rich in starch and contribute importantly to food security and the cash income of farmers who cultivate them. Complex value chains have emerged that link producers to consumers, but irregular product quality and market chain inequalities undermine the economic well-being of producers and retailers. Peach palm is genetically diverse, but screening for traits of commercial and nutritional interest is required to enhance the use of its genetic resources. Alliances between public organizations and private enterprises are needed to realize the potential for processing novel products from peach palm, especially in the pharmaceutical and cosmetic sectors. The diverse challenges that emerge at different stages of production, processing and marketing require participatory research that directly involves stakeholders from the beginning. 相似文献
1000.
Most landscape genetic studies assess the impact of landscape elements on species' dispersal and gene flow. Many of these studies perform their analysis on all possible population pairs in a study area and do not explicitly consider the effects of spatial scale and population network topology on their results. Here, we examined the effects of spatial scale and population network topology on the outcome of a landscape genetic analysis. Additionally, we tested whether the relevant spatial scale of landscape genetic analysis could be defined by population network topology or by isolation‐by‐distance (IBD) patterns. A data set of the wetland grasshopper Stethophyma grossum, collected in a fragmented agricultural landscape, was used to analyse population network topology, IBD patterns and dispersal habitats, using least‐cost transect analysis. Landscape genetic analyses neglecting spatial scale and population network topology resulted in models with low fits, with which a most likely dispersal habitat could not be identified. In contrast, analyses considering spatial scale and population network topology resulted in high model fits by restricting landscape genetic analysis to smaller scales (0–3 km) and neighbouring populations, as represented by a Gabriel graph. These models also successfully identified a likely dispersal habitat of S. grossum. The above results suggest that spatial scale and potentially population network topology should be more explicitly considered in future landscape genetic analyses. 相似文献