全文获取类型
收费全文 | 4311篇 |
免费 | 253篇 |
国内免费 | 9篇 |
出版年
2023年 | 42篇 |
2022年 | 61篇 |
2021年 | 129篇 |
2020年 | 91篇 |
2019年 | 108篇 |
2018年 | 135篇 |
2017年 | 127篇 |
2016年 | 155篇 |
2015年 | 219篇 |
2014年 | 290篇 |
2013年 | 304篇 |
2012年 | 331篇 |
2011年 | 364篇 |
2010年 | 229篇 |
2009年 | 162篇 |
2008年 | 246篇 |
2007年 | 194篇 |
2006年 | 185篇 |
2005年 | 168篇 |
2004年 | 139篇 |
2003年 | 126篇 |
2002年 | 113篇 |
2001年 | 63篇 |
2000年 | 76篇 |
1999年 | 58篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 11篇 |
1994年 | 30篇 |
1993年 | 19篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1972年 | 7篇 |
1971年 | 9篇 |
排序方式: 共有4573条查询结果,搜索用时 15 毫秒
141.
Background
The increasing use of zebrafish model has not been accompanied by the evolution of proper anaesthesia for this species in research. The most used anaesthetic in fishes, MS222, may induce aversion, reduction of heart rate, and consequently high mortality, especially during long exposures. Therefore, we aim to explore new anaesthetic protocols to be used in zebrafish by studying the quality of anaesthesia and recovery induced by different concentrations of propofol alone and in combination with different concentrations of lidocaine.Material and Methods
In experiment A, eighty-three AB zebrafish were randomly assigned to 7 different groups: control, 2.5 (2.5P), 5 (5P) or 7.5 μg/ml (7.5P) of propofol; and 2.5 μg/ml of propofol combined with 50, (P/50L), 100 (P/100L) or 150 μg/ml (P/150L) of lidocaine. Zebrafish were placed in an anaesthetic water bath and time to lose the equilibrium, reflex to touch, reflex to a tail pinch, and respiratory rate were measured. Time to gain equilibrium was also assessed in a clean tank. Five and 24 hours after anaesthesia recovery, zebrafish were evaluated concerning activity and reactivity. Afterwards, in a second phase of experiments (experiment B), the best protocol of the experiment A was compared with a new group of 8 fishes treated with 100 mg/L of MS222 (100M).Results
In experiment A, only different concentrations of propofol/lidocaine combination induced full anaesthesia in all animals. Thus only these groups were compared with a standard dose of MS222 in experiment B. Propofol/lidocaine induced a quicker loss of equilibrium, and loss of response to light and painful stimuli compared with MS222. However zebrafish treated with MS222 recovered quickly than the ones treated with propofol/lidocaine.Conclusion
In conclusion, propofol/lidocaine combination and MS222 have advantages in different situations. MS222 is ideal for minor procedures when a quick recovery is important, while propofol/lidocaine is best to induce a quick and complete anaesthesia. 相似文献142.
Mariana Milano Milton Ozório Moraes Rodrigo Rodenbusch Caroline Xavier Carvalho Melaine Delcroix Gabriel Mousquer Lucas Laux da Costa Gisela Unis Elis Regina Dalla Costa Maria Lucia Rosa Rossetti 《PloS one》2016,11(2)
In Mycobacterium tuberculosis (MTB) infection, the complex interaction of host immune system and the mycobacteria is associated with levels of cytokines production that play a major role in determining the outcome of the disease. Several single-nucleotide polymorphisms (SNPs) in cytokine genes have been associated with tuberculosis (TB) outcome. The aim of this study was to evaluate the association between previously reported SNPs IL2–330 T>G (rs2069762); IL4–590 C>T (rs2243250); IL6–174 G>C (rs1800795); IL10–592 A>C (rs1800872); IL10–1082 G>A (rs1800896); IL17A -692 C>T (rs8193036); IL17A -197 G>A (rs2275913); TNF -238 G>A (rs361525); TNF -308 G>A (rs1800629) and IFNG +874 T>A (rs2430561) and pulmonary TB (PTB) susceptibility. We conducted a case-control study in individuals from Southern Brazil who were recruited between February 2012 and October 2013 in a high incidence TB city. We performed a multiplex genotyping assay in 191 patients with PTB and 175 healthy subjects. Our results suggest a decreased risk for PTB development associated with the IL17A -197A allele (OR = 0.29; p = 0.04), AA genotype (OR = 0.12; p = 0.04) and A carrier (AG/AA) (OR = 0.29; p = 0.004) and IL6 -174C carrier (CC/CG) (OR = 0.46; p = 0.04). We could not properly analyze IL17A -692 C>T (rs8193036) and IFNG +874T>A due to genotypic inconsistencies and found no evidence of association for the IL2, IL4, IL10 and TNF polymorphisms and PTB. In conclusion, our results show a protective effect of IL17 and IL6 polymorphisms on PTB outcome in Southern Brazilian population. 相似文献
143.
Concepta McManus Júlio Otávio Jardim Barcellos Bruna Krummenauer Formenton Potira Meirelles Hermuche Osmar Abílio de Carvalho Jr RenatoFontes Guimar?es Miguelangelo Gianezini Eduardo Antunes Dias Vinícius do Nascimento Lampert Daniele Zago José Braccini Neto 《PloS one》2016,11(1)
Movement of livestock production within a country or region has implications for genetics, adaptation, well-being, nutrition, and production logistics, particularly in continental-sized countries, such as Brazil. Cattle production in Brazil from 1977 to 2011 was spatialized, and the annual midpoint of production was calculated. Changes in the relative production and acceleration of production were calculated and spatialized using ARCGIS®. Cluster and canonical discriminant analyses were performed to further highlight differences between regions in terms of cattle production. The mean production point has moved from the Center of Minas Gerais State (in the southeast region) to the North of Goiás State (in the Midwest region). This reflects changes in environmental factors, such as pasture type, temperature and humidity. Acceleration in production in the northern region of Brazil has remained strong over the years. More recently, “traditional” cattle-rearing regions, such as the south and southeast, showed a reduction in growth rates as well as a reduction in herd size or internal migration over the period studied. These maps showed that this movement tends to be gradual, with few regions showing high acceleration or deceleration rates. 相似文献
144.
145.
146.
147.
Discovery of A-type procyanidin dimers in yellow raspberries by untargeted metabolomics and correlation based data analysis 总被引:1,自引:0,他引:1
Elisabete Carvalho Pietro Franceschi Antje Feller Lorena Herrera Luisa Palmieri Panagiotis Arapitsas Samantha Riccadonna Stefan Martens 《Metabolomics : Official journal of the Metabolomic Society》2016,12(9):144
Introduction
Raspberries are becoming increasingly popular due to their reported health beneficial properties. Despite the presence of only trace amounts of anthocyanins, yellow varieties seems to show similar or better effects in comparison to conventional raspberries.Objectives
The aim of this work is to characterize the metabolic differences between red and yellow berries, focussing on the compounds showing a higher concentration in yellow varieties.Methods
The metabolomic profile of 13 red and 12 yellow raspberries (of different varieties, locations and collection dates) was determined by UPLC–TOF-MS. A novel approach based on Pearson correlation on the extracted ion chromatograms was implemented to extract the pseudospectra of the most relevant biomarkers from high energy LC–MS runs. The raw data will be made publicly available on MetaboLights (MTBLS333).Results
Among the metabolites showing higher concentration in yellow raspberries it was possible to identify a series of compounds showing a pseudospectrum similar to that of A-type procyanidin polymers. The annotation of this group of compounds was confirmed by specific MS/MS experiments and performing standard injections.Conclusions
In berries lacking anthocyanins the polyphenol metabolism might be shifted to the formation of a novel class of A-type procyanidin polymers.148.
149.
Ana Paula Kallaur Josiane Lopes Sayonara Rangel Oliveira Andrea Name Colado Simão Edna Maria Vissoci Reiche Elaine Regina Delicato de Almeida Helena Kaminami Morimoto Wildea Lice Carvalho Jennings de Pereira Daniele Frizon Alfieri Sueli Donizete Borelli Domacio Ramon Kaimen-Maciel Michael Maes 《Molecular neurobiology》2016,53(8):5191-5202
150.
Peter Zeilhofer Débora Fernandes Calheiros Márcia Divina de Oliveira Eliana Freire Gaspar de Carvalho Dores Gilson Alberto Rosa Lima Ibraim Fantin-Cruz 《Wetlands Ecology and Management》2016,24(6):697-716
Water quality time series available for major tropical floodplains commonly have low temporal resolutions and irregular sampling frequencies. Here we examine such data using singular spectrum analysis, a non-parametric time series analysis technique, to assess the typical cyclical variations and long-term trends in upland Cerrado and lowland floodplain reaches of three rivers that are tributaries to the Pantanal in Brazil to evaluate ecological state and impact level, and develop recommendations for improved monitoring of Cerrado–Pantanal river systems. Both upland and lowland reaches have their average water quality cycles linked to a monocyclical hydrological regime. Amplitudes of nutrient concentrations (N, P) and Turbidity are higher in the uplands, whereas cyclical oxygen variations are up to two times higher in the floodplain reaches. SSA showed that trend extraction is possible for parameters with lower intra-annual variations and were found to be partially opposing (oxygen) in upland (negative trend) and floodplain (positive trend) stations. Land use intensification in the uplands is reflected by N concentrations in upland reaches. In the floodplain, the Paraguay river was found under a slight TN enrichment regime of about 0.02 mg L?1 per year between 1995 and 2009. Assuming a fixed budget for institutional water quality monitoring, we recommend a reduction of the 150 registered sampling gauges by environmental agencies in the Brazilian Pantanal and its contribution area, 95 % of them with less than four samples per year, in favor of using the same resources for increased sampling frequency at a smaller number of sites. 相似文献