全文获取类型
收费全文 | 1171篇 |
免费 | 94篇 |
专业分类
1265篇 |
出版年
2022年 | 12篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 30篇 |
2018年 | 26篇 |
2017年 | 36篇 |
2016年 | 35篇 |
2015年 | 63篇 |
2014年 | 58篇 |
2013年 | 83篇 |
2012年 | 80篇 |
2011年 | 72篇 |
2010年 | 55篇 |
2009年 | 40篇 |
2008年 | 79篇 |
2007年 | 60篇 |
2006年 | 65篇 |
2005年 | 60篇 |
2004年 | 41篇 |
2003年 | 40篇 |
2002年 | 40篇 |
2001年 | 22篇 |
2000年 | 30篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1974年 | 7篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1956年 | 3篇 |
1943年 | 3篇 |
排序方式: 共有1265条查询结果,搜索用时 11 毫秒
81.
82.
Sciutto E Rosas G Cruz-Revilla C Toledo A Cervantes J Hernández M Hernándezt B Goldbaum FA de Aluja AS Fragoso G Larralde C 《The Journal of parasitology》2007,93(4):824-831
Review of experimental and observational evidence about various cestode infections of mammalian hosts revives hope for the development of an effective vaccine against adult intestinal tapeworms, the central protagonists in their transmission dynamics. As for Taenia solium, there are abundant immunological data regarding cysticercosis in humans and pigs, but information about human taeniasis is scarce. A single publication reporting protection against T. solium taeniasis by experimental primo infection and by vaccination of an experimental foster host, the immunocompetent female hamster, kindles the hope of a vaccine against the tapeworm to be used in humans, its only natural definitive host. 相似文献
83.
González Ramírez M Orozco Suárez S Salgado Ceballos H Feria Velasco A Rocha L 《Cellular and molecular neurobiology》2007,27(2):211-227
Effects of hyperthermia-induced seizures (HS) on GABAA and benzodiazepine (BDZ) receptor binding in immature rat brain were evaluated using in vitro autoradiography. HS were induced
in 10-days-old rats by a regulated stream of moderately heated air directed 50 cm above the animals. Rats were killed 30 min,
24 h or 20 days after HS and their brains were used for in vitro autoradiography experiments to determine GABAA and BDZ receptor binding. GABAA binding was significantly enhanced in all brain areas evaluated 30 min after HS, an effect that endures 24 h and 20 days
after seizures. Concerning BDZ receptor binding, a significant increase was detected in entorhinal and perirhinal cortices
and decreased in basolateral amygdala 30 min following HS. One day after HS, animals demonstrated enhanced BDZ binding in
the cingulate, frontal, posterior parietal, entorhinal, temporal and perirhinal cortices; striatum, accumbens, substantia
nigra pars compacta and amygdala nuclei. Twenty days after HS enhanced BDZ binding was restricted in the cingulated, frontal,
anterior and posterior parietal cortices, as well as in substantia nigra pars reticulata, whereas decreased values were found
in accumbens nucleus and substantia nigra pars compacta. Our data indicate differential effects of HS in GABAA and BDZ binding in immature brain. HS-induced GABAA and BDZ changes are different from those previously described in experimental models of temporal lobe epilepsy in adult animals. 相似文献
84.
Morales-Rodríguez I Yañez-Morales M Silva-Rojas HV García-de-Los-Santos G Guzmán-de-Peña DA 《Mycopathologia》2007,163(1):31-39
Fusarium
proliferatum, F. subglutinans, and F. verticillioides are known causes of ear and kernel rot in maize worldwide. In Mexico, only F. verticillioides and F. subglutinans, have been reported previously as causal agents of this disease. However, Fusarium isolates with different morphological characteristics to the species that are known to cause this disease were obtained in
the Highland-Valley region of this country from symptomatic and symptomless ears of native and commercial maize genotypes.
Moreover, while the morphological studies were not sufficient to identify the correct taxonomic position at the species level,
analyses based in the Internal Transcribed Spacer region and the Nuclear Large Subunit Ribosomal partial sequences allowed
for the identification of F. subglutinans, F. solani, and F. verticillioides, as well as four species (F. chlamydosporum, F. napiforme, F. poae, and F. pseudonygamai) that had not previously been reported to be associated with ear rot. In addition, F. napiforme and F. solani were absent from symptomless kernels. Phylogenetic analysis showed genetic changes in F. napiforme, and F. pseudonygamai isolates because they were not true clones, and probably constitute separate sibling species. The results of this study suggest
that the biodiversity of Fusarium species involved in ear rot in Mexico is greater than that reported previously in other places in the world. This new knowledge
will permit a better understanding of the relationship between all the species involved in ear rot disease and their relationship
with maize. 相似文献
85.
Tarsitano CA Paffaro VA Pauli JR da Silva GH Saad MJ Salgado I da Cruz-Höfling MA Hyslop S 《Cell and tissue research》2007,329(1):45-58
Chronic treatment of rats with N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) biosynthesis, results in hypertension mediated partly by enhanced angiotensin-I-converting enzyme (ACE) activity. We examined the influence of L-NAME on rat liver morphology, on hepatic glycogen, cholesterol, and triglyceride content, and on the activities of the cytochrome P450 isoforms CYP1A1/2, CYP2B1/2, CYP2C11, and CYP2E1. Male Wistar rats were treated with L-NAME (20 mg/rat per day via drinking water) for 2, 4, and 8 weeks, and their livers were then removed for analysis. Enzymatic induction was produced by treating rats with phenobarbital (to induce CYP2B1/2), beta-naphthoflavone (to induce CYP1A1/2), or pyrazole (to induce CYP2E1). L-NAME significantly elevated blood pressure; this was reversed by concomitant treatment with enalapril (ACE inhibitor) or losartan (angiotensin II AT(1) receptor antagonist). L-NAME caused vascular hypertrophy in hepatic arteries, with perivascular and interstitial fibrosis involving collagen deposition. Hepatic glycogen content also significantly increased. L-NAME did not affect fasting glucose levels but significantly reduced insulin levels and increased the insulin sensitivity of rats, based on an intraperitoneal glucose tolerance test. Immunoblotting experiments indicated enhanced phosphorylation of protein kinase B and of glycogen synthase kinase 3. All these changes were reversed by concomitant treatment with enalapril or losartan. L-NAME had no effect on hepatic cholesterol or triglyceride content or on the basal or drug-induced activities and protein expression of the cytochrome P450 isoforms. Thus, the chronic inhibition of NO biosynthesis produced hepatic morphological alterations and changes in glycogen metabolism mediated by the renin-angiotensin system. The increase in hepatic glycogen content probably resulted from enhanced glycogen synthase activity following the inhibition of glycogen synthase kinase 3 by phosphorylation. 相似文献
86.
87.
Heritability and genetic correlations of metabolic disease-related phenotypes in Mexico: preliminary report from the GEMM Family Study 总被引:1,自引:0,他引:1
Bastarrachea RA Kent JW Rozada G Cole SA López-Alvarenga JC Aradillas C Brito-Zurita O Cerda-Flores RM Ibarra-Costilla E Gallegos E Laviada-Molina H Hernandez-Escalante V Rosas J Machado A Vadillo F Ramos M Lazalde B Santa-Olalla J MacCluer JW Comuzzie AG 《Human biology; an international record of research》2007,79(1):121-129
Cardiovascular disease (CVD) is a major cause of mortality in the Republic of Mexico, and metabolic syndrome, a complex of CVD risk factors, is increasingly prevalent. To date, however, there have been few studies of the genetic epidemiology of metabolic syndrome in Mexico. As a first step in implementing the GEMM Family Study, a large, multicenter collaborative study, we recruited 375 individuals in 21 extended families, without ascertainment on disease, at 9 medical institutions across Mexico. Participants were measured for anthropometric (stature, weight, waist circumference) and hemodynamic (blood pressure, heart rate) phenotypes; glucose, cholesterol, and triglyceride levels were measured in fasting blood. Variance components-based quantitative genetic analyses were performed using SOLAR. All phenotypes except diastolic blood pressure were significantly heritable. Consistent with the definition of metabolic syndrome, many phenotypes exhibited significant environmental correlation, and significant genetic correlations were found between measures of adiposity and fasting glucose and fasting triglyceride levels. These preliminary data represent the first heritability estimates for many of these phenotypes in the Republic of Mexico and indicate that this study design offers excellent power for future gene discovery relative to metabolic disease. 相似文献
88.
Spatial and temporal distribution patterns of the macrozoobenthos assemblage in the salt marshes of Tejo estuary (Portugal) 总被引:1,自引:0,他引:1
The present study focuses on the spatial and temporal distribution of the macroinvertebrate community of the salt marsh areas
of the Tejo estuary, based on surveys conducted from autumn 1998 to summer 2000. Samples were collected quarterly in five
different intertidal areas along an elevation gradient in: mudflats, creek mouths, creeks, pioneer salt marsh areas and middle
marsh areas. A total of 36 benthic invertebrate taxa were identified. Insect larvae were the most well represented group,
with 10 taxa identified. Oligochaetes and ostracods were the most numerically abundant taxa, whereas bivalves dominated in
biomass. Benthic macroinvertebrate assemblages were dominated, both in number and biomass, by deposit feeders. Three distinct
macroinvertebrate assemblages were distinguished along the elevation gradient, based on species presence, density and biomass:
the unvegetated muddy areas with a macrobenthic assemblage composed mostly by infauna; the salt marsh pioneer areas of Spartina maritima in which several epibenthic taxa were found, as well as endobenthic taxa characteristic of muddy sediment; and the creek
margins, with epifauna taxa such as insect larvae and crustaceans and a low abundance of benthic infauna. Total biomass in
the unvegetated and Spartina areas was higher during spring and summer mainly due to the increase in biomass of Scrobicularia plana and Hydrobia ulvae. No decreases in the salt marsh macroinvertebrate biomass values were observed during the highest densities of their potential
nektonic predators (summer). This fact might indicate that macroinvertebrates are not a limiting resource for the nektonic
species, and that the natural biomass increment of these invertebrate species could be masking the predation/disturbance caused
by the nektonic species. 相似文献
89.
Endophytes are fungi that cause asymptomatic infections in leaves and stems of healthy plants. This study evaluated the presence of endophytic fungi on leaves of Rosa hybrida collected in Bogota, (Colombia) using histological techniques and light microscopy. Histological preparations showed fungal mycelium with few cells in the vascular tissue. Colonization of mesophyll cells was not observed. Visualization of fungal cells within plant tissues is a confirmatory test of the endophytic habitat of fungi isolated from leaves of Rosa hybrida. 相似文献
90.
Vallejos-Almirall Alejandro Riquelme Margarita Uribe Elena Agurto-Muñoz Cristian Rosas Anali Vergara Carola 《Journal of applied phycology》2022,34(5):2371-2382
Journal of Applied Phycology - Ultraviolet (UV) radiation generates cyclobutane pyrimidine dimer (CPD) photoproducts in the DNA of skin cells, causing photoaging and non-melanoma skin cancer.... 相似文献