全文获取类型
收费全文 | 946篇 |
免费 | 79篇 |
出版年
2023年 | 13篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 30篇 |
2017年 | 26篇 |
2016年 | 43篇 |
2015年 | 47篇 |
2014年 | 59篇 |
2013年 | 71篇 |
2012年 | 76篇 |
2011年 | 72篇 |
2010年 | 45篇 |
2009年 | 45篇 |
2008年 | 53篇 |
2007年 | 47篇 |
2006年 | 33篇 |
2005年 | 43篇 |
2004年 | 42篇 |
2003年 | 49篇 |
2002年 | 29篇 |
2001年 | 21篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1025条查询结果,搜索用时 171 毫秒
991.
P Torres E Ruíz C Rebolledo A Mira V Cubillos N Navarrete W Gesche A Montefusco L Valdés A Alberdi 《Boletín chileno de parasitología》1990,45(3-4):47-55
In April and December 1989, 35 fish from Lake Huillinco (42 degrees 48'S, 74 degrees 02'W) and 36 fish from Lake Natri (42 degrees 48'S, 73 degrees 50'W), in the Great Island of Chiloé (Chile) were examined. Coprological samples from 159 persons, 17 dogs, 19 pigs and 4 cats from around both lakes were examined for Diphyllobothrium spp. infection. In the Lake Huillinco the following helminths of fishes were determined: Contracaecum sp. and Hysterothylacium sp. in Salmo trutta, Cauque mauleanum and Eleginops maclovinus; Dichelyne (Cucullanellus) dichelyneformis in S. trutta and E. maclovinus and Scolex pleuronectis in S. trutta. One specimen of Mugil cephalus did not show helminth parasites. Prevalence of infection were greater for Contracaecum sp. in S. trutta (75.0%) and C. mauleanum (76.0%); and Hysterothylacium sp. in E. maclovinus (75.0%). Mean intensity was higher for D. (C.) dichelyneformis in E. maclovinus. Contracaecum sp. in S. trutta, Oncorhynchus mykiss, Oncorhynchus kisutch and Galaxias maculatus; Acanthocephalus sp. in S. trutta and G. maculatus, S. pleuronectis in O. mykiss and Cystidicoloides sp. in G. maculatus were determined at Lake Natri. Prevalence and intensity of infection were higher for Contracaecum sp. in S. trutta and O. kisutch. Infection by Diphyllobothrium sp. was determined in one domestic cat. Prevalence of infection by intestinal protozoan and helminths in human population only showed significative differences for Ascaris lumbricoides and Trichuris trichiura that were higher in the Lake Huillinco. Importance of natural infection by helminth parasites for fish in cultured condition and possible mechanisms of infections in relation to the diet of fishes are discussed. 相似文献
992.
Patrícia d‘Emery Alves Santos Virgínia Maria Barros de Lorena érica de Souza Fernandes Iana Rafaela Fernandes Sales Wheverton Ricardo Correia do Nascimento Yara de Miranda Gomes M?nica Camelo Pessoa de Azevedo Albuquerque Vlaudia Maria Assis Costa Valdênia Maria Oliveira de Souza 《Memórias do Instituto Oswaldo Cruz》2016,111(2):83-92
Schistosoma mansoni antigens in the early life alter homologous and
heterologous immunity during postnatal infections. We evaluate the immunity to
parasite antigens and ovalbumin (OA) in adult mice born/suckled by schistosomotic
mothers. Newborns were divided into: born (BIM), suckled (SIM) or born/suckled (BSIM)
in schistosomotic mothers, and animals from noninfected mothers (control). When
adults, the mice were infected and compared the hepatic granuloma size and
cellularity. Some animals were OA + adjuvant immunised. We evaluated hypersensitivity
reactions (HR), antibodies levels (IgG1/IgG2a) anti-soluble egg antigen and
anti-soluble worm antigen preparation, and anti-OA, cytokine production, and
CD4+FoxP3+T-cells by splenocytes. Compared to control group,
BIM mice showed a greater quantity of granulomas and collagen deposition, whereas SIM
and BSIM presented smaller granulomas. BSIM group exhibited the lowest levels of
anti-parasite antibodies. For anti-OA immunity, immediate HR was suppressed in all
groups, with greater intensity in SIM mice accompanied of the remarkable level of
basal CD4+FoxP3+T-cells. BIM and SIM groups produced less
interleukin (IL)-4 and interferon (IFN)-g. In BSIM, there was higher
production of IL-10 and IFN-g, but lower levels of IL-4 and
CD4+FoxP3+T-cells. Thus, pregnancy in schistosomotic mothers
intensified hepatic fibrosis, whereas breastfeeding diminished granulomas in
descendants. Separately, pregnancy and breastfeeding could suppress heterologous
immunity; however, when combined, the responses could be partially restored in
infected descendants. 相似文献
993.
Ma Guadalupe Valadez-Bustos Gerardo Armando Aguado-Santacruz Axel Tiessen-Favier Alejandrina Robledo-Paz Abel Muñoz-Orozco Quintin Rascón-Cruz Amalio Santacruz-Varela 《Analytical biochemistry》2016
Glycine betaine is a quaternary ammonium compound that accumulates in a large variety of species in response to different types of stress. Glycine betaine counteracts adverse effects caused by abiotic factors, preventing the denaturation and inactivation of proteins. Thus, its determination is important, particularly for scientists focused on relating structural, biochemical, physiological, and/or molecular responses to plant water status. In the current work, we optimized the periodide technique for the determination of glycine betaine levels. This modification permitted large numbers of samples taken from a chlorophyllic cell line of the grass Bouteloua gracilis to be analyzed. Growth kinetics were assessed using the chlorophyllic suspension to determine glycine betaine levels in control (no stress) cells and cells osmotically stressed with 14 or 21% polyethylene glycol 8000. After glycine extraction, different wavelengths and reading times were evaluated in a spectrophotometer to determine the optimal quantification conditions for this osmolyte. Optimal results were obtained when readings were taken at a wavelength of 290 nm at 48 h after dissolving glycine betaine crystals in dichloroethane. We expect this modification to provide a simple, rapid, reliable, and cheap method for glycine betaine determination in plant samples and cell suspension cultures. 相似文献
994.
995.
996.
Maria S. Fadeeva Cinthia Núñez Yulia V. Bertsova Guadalupe Espín & Alexander V. Bogachev 《FEMS microbiology letters》2008,279(1):116-123
The catalytic properties of sodium-translocating NADH:quinone oxidoreductases (Na+ -NQRs) from the marine bacterium Vibrio harveyi , the enterobacterium Klebsiella pneumoniae , and the soil microorganism Azotobacter vinelandii have been comparatively analyzed. It is shown that these enzymes drastically differ in their affinity to sodium ions. The enzymes also possess different sensitivity to inhibitors. Na+ -NQR from A. vinelandii is not sensitive to low 2- n -heptyl-4-hydroxyquinoline N-oxide (HQNO) concentrations, while Na+ -NQR from K. pneumoniae is fully resistant to either Ag+ or N-ethylmaleimide. All the Na+ -NQR-type enzymes are sensitive to diphenyliodonium, which is shown to modify the noncovalently bound FAD of the enzyme. 相似文献
997.
998.
Oscar David Kirstein Guadalupe Ayora-Talavera Edgar Koyoc-Cardea Daniel Chan Espinoza Azael Che-Mendoza Azael Cohuo-Rodriguez Pilar Granja-Prez Henry Puerta-Guardo Norma Pavia-Ruz Mike W. Dunbar Pablo Manrique-Saide Gonzalo M. Vazquez-Prokopec 《PLoS neglected tropical diseases》2021,15(1)
Arbovirus infection in Aedes aegypti has historically been quantified from a sample of the adult population by pooling collected mosquitoes to increase detectability. However, there is a significant knowledge gap about the magnitude of natural arbovirus infection within areas of active transmission, as well as the sensitivity of detection of such an approach. We used indoor Ae. aegypti sequential sampling with Prokopack aspirators to collect all mosquitoes inside 200 houses with suspected active ABV transmission from the city of Mérida, Mexico, and tested all collected specimens by RT-PCR to quantify: a) the absolute arbovirus infection rate in individually tested Ae. aegypti females; b) the sensitivity of using Prokopack aspirators in detecting ABV-infected mosquitoes; and c) the sensitivity of entomological inoculation rate (EIR) and vectorial capacity (VC), two measures ABV transmission potential, to different estimates of indoor Ae. aegypti abundance. The total number of Ae. aegypti (total catch, the sum of all Ae. aegypti across all collection intervals) as well as the number on the first 10-min of collection (sample, equivalent to a routine adult aspiration session) were calculated. We individually tested by RT-PCR 2,161 Aedes aegypti females and found that 7.7% of them were positive to any ABV. Most infections were CHIKV (77.7%), followed by DENV (11.4%) and ZIKV (9.0%). The distribution of infected Aedes aegypti was overdispersed; 33% houses contributed 81% of the infected mosquitoes. A significant association between ABV infection and Ae. aegypti total catch indoors was found (binomial GLMM, Odds Ratio > 1). A 10-min indoor Prokopack collection led to a low sensitivity of detecting ABV infection (16.3% for detecting infected mosquitoes and 23.4% for detecting infected houses). When averaged across all infested houses, mean EIR ranged between 0.04 and 0.06 infective bites per person per day, and mean VC was 0.6 infectious vectors generated from a population feeding on a single infected host per house/day. Both measures were significantly and positively associated with Ae. aegypti total catch indoors. Our findings provide evidence that the accurate estimation and quantification of arbovirus infection rate and transmission risk is a function of the sampling effort, the local abundance of Aedes aegypti and the intensity of arbovirus circulation. 相似文献
999.
NM Macias-Gomez E Leal Ugarte M Gutiérrez-Angulo G Domínguez-Quezada H Rivera P Barros-Nuñez 《Journal of medical case reports》2012,6(1):301
ABSTRACT: INTRODUCTION: Beckwith--Wiedemann syndrome is an overgrowth syndrome that is characterized by hypoglycemia at birth, coarse face, hemihypertrophy and an increased risk to develop embryonal tumors. In approximately 15% of patients, the inheritance is autosomal dominant with variable expressivity and incomplete penetrance, whereas the remainder of Beckwith--Wiedemann syndrome cases are sporadic. Beckwith--Wiedemann syndrome molecular etiologies are complex and involve the two imprinting centers 1 (IC1) and 2 (IC2) of 11p15 region. This case report describes, for the first time, the unusual association of ovotesticular disorder in a patient from Morelia, Mexico with Wiedemann-Beckwith syndrome. CASE PRESENTATION: We report the case of a Mexican six-year-old girl with Beckwith--Wiedemann Syndrome, ambiguous genitalia, and bilateral ovotestes. She has a 46,XX karyotype without evidence of Y-chromosome sequences detected by fluorescence in situ hybridization with both SRY and wcp-Y probes. CONCLUSION: Although a random association between these two conditions cannot be excluded, future analysis of this patient with Beckwith--Wiedemann syndrome and 46,XX ovotesticular disorder may lead to new insights into these complex pathologies. We speculate that a possible misregulation in the imprinted genes network has a fundamental role in the coexistence of these two disorders. 相似文献
1000.
E. Valdés-Correcher Esther Rodriguez Yvonne J. M. Kemp Martin J. Wassen Joris P. G. M. Cromsigt 《Acta theriologica》2018,63(4):455-466
Woody plant encroachment has increased across the globe and threatens biodiversity associated with open habitats. In order to prevent or reduce woody encroachment, conservation managers across Europe introduce large mammalian herbivores. While up to recently, managers were mostly using free-ranging domestic cattle and horses for this, there is an increasing interest in the use of European bison for nature management. However, we lack studies that compare the impact of these different grazers on vegetation. We report results from a unique grazing pilot in the National Park Zuid-Kennemerland, a heterogeneous coastal dune landscape in the Netherlands, where European bison, horses, and cattle were introduced to reverse the encroachment of grass and shrub species. We present results of an 8-year study on the development of woody and grassy vegetation on fixed transects in three different grazing areas within the national park; one area with European bison and horses, one area with cattle and horses, and one area where these large grazers were excluded. In all three areas, rabbit, fallow deer, and roe deer were present. Over time, we observed strong reductions in the vitality of several woody species, such as spindle tree, and this decline was similar across all areas. Grass height and cover also declined and the proportion of herbs increased in all three grazing areas in similar ways. However, the type of herbivore use (debarking, foraging on buds, branches) of several woody species differed significantly among areas. For instance, maple tree was only debarked in the E. bison area, while hawthorn branches were eaten significantly more in the cattle than in the bison area. Due to differences in herbivore densities among areas, it was difficult to draw strong conclusions on how the different herbivore species differed in their impact, but, importantly, we found that grazing regimes with bison can lead to as strong effects on vegetation structure and composition as grazing regimes with cattle. This is an important result since certain conditions, such as legal aspects, may motivate managers to introduce a wild large grazer rather than a domesticated one. 相似文献