全文获取类型
收费全文 | 938篇 |
免费 | 65篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 26篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 33篇 |
2015年 | 58篇 |
2014年 | 39篇 |
2013年 | 67篇 |
2012年 | 109篇 |
2011年 | 83篇 |
2010年 | 51篇 |
2009年 | 52篇 |
2008年 | 66篇 |
2007年 | 58篇 |
2006年 | 54篇 |
2005年 | 54篇 |
2004年 | 39篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1986年 | 2篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1004条查询结果,搜索用时 62 毫秒
121.
Carlos S. Grijalva-Eternod Jonathan C. K. Wells Mario Cortina-Borja Nuria Salse-Ubach M��lody C. Tondeur Carmen Dolan Chafik Meziani Caroline Wilkinson Paul Spiegel Andrew J. Seal 《PLoS medicine》2012,9(10)
Background
Households from vulnerable groups experiencing epidemiological transitions are known to be affected concomitantly by under-nutrition and obesity. Yet, it is unknown to what extent this double burden affects refugee populations dependent on food assistance. We assessed the double burden of malnutrition among Western Sahara refugees living in a protracted emergency.Methods and Findings
We implemented a stratified nutrition survey in October–November 2010 in the four Western Sahara refugee camps in Algeria. We sampled 2,005 households, collecting anthropometric measurements (weight, height, and waist circumference) in 1,608 children (6–59 mo) and 1,781 women (15–49 y). We estimated the prevalence of global acute malnutrition (GAM), stunting, underweight, and overweight in children; and stunting, underweight, overweight, and central obesity in women. To assess the burden of malnutrition within households, households were first classified according to the presence of each type of malnutrition. Households were then classified as undernourished, overweight, or affected by the double burden if they presented members with under-nutrition, overweight, or both, respectively.The prevalence of GAM in children was 9.1%, 29.1% were stunted, 18.6% were underweight, and 2.4% were overweight; among the women, 14.8% were stunted, 53.7% were overweight or obese, and 71.4% had central obesity. Central obesity (47.2%) and overweight (38.8%) in women affected a higher proportion of households than did GAM (7.0%), stunting (19.5%), or underweight (13.3%) in children. Overall, households classified as overweight (31.5%) were most common, followed by undernourished (25.8%), and then double burden–affected (24.7%).Conclusions
The double burden of obesity and under-nutrition is highly prevalent in households among Western Sahara refugees. The results highlight the need to focus more attention on non-communicable diseases in this population and balance obesity prevention and management with interventions to tackle under-nutrition. Please see later in the article for the Editors'' Summary 相似文献122.
Rita Brines Nuria Maicas María Luisa Ferrándiz Agnieszka Loboda Alicja Jozkowicz Jozef Dulak María José Alcaraz 《PloS one》2012,7(12)
Background
Heme oxygenase-1 (HO-1) is induced in many cell types as a defense mechanism against stress. We have investigated the possible role of endogenous HO-1 in the effector phase of arthritis using the K/BxN serum transfer model of arthritis in HO-1 heterozygous and homozygous knock-out mice.Methodology/Principal Findings
Arthritis was induced in C57/Black-6 xFVB (HO-1+/+, HO-1+/− and HO-1−/−) mice by intraperitoneal injection of 150 µl serum from arthritic K/BxN mice at days 0 and 2. Blood was collected and animals were sacrificed at day 10. Histological analysis was performed in ankle sections. The levels of inflammatory mediators were measured in serum and paw homogenates by enzyme-linked immunosorbent assay or Multiplex technology. The incidence of arthritis was higher in HO-1+/− and HO-1−/− groups compared with HO-1+/+. The inflammatory response was aggravated in HO-1+/− mice as shown by arthritic score and the migration of inflammatory cells that could be related to the enhancement of CXCL-1 production. In addition, the HO-1+/− group showed proteoglycan depletion significantly higher than HO-1+/+ mice. Serum levels of matrix metalloproteinase-3, monocyte chemotactic protein-1, plasminogen activator inhibitor-1, E-selectin and intercellular adhesion molecule-1 were increased in arthritic HO-1−/− mice, whereas vascular endothelial growth factor and some cytokines such as interferon-γ showed a reduction compared to HO-1+/+ or HO-1+/− mice. In addition, down-regulated gene expression of ferritin, glutathione S-reductase A1 and superoxide dismutase-2 was observed in the livers of arthritic HO-1+/− animals.Conclusion/Significance
Endogenous HO-1 regulates the production of systemic and local inflammatory mediators and plays a protective role in K/BxN serum transfer arthritis. 相似文献123.
Acosta JC Ferrándiz N Bretones G Torrano V Blanco R Richard C O'Connell B Sedivy J Delgado MD León J 《Molecular and cellular biology》2008,28(24):7286-7295
124.
Spatial Heterogeneity of Bacterial Populations in Monomictic Lake Estanya (Huesca,Spain) 总被引:2,自引:0,他引:2
Bacterial population changes were investigated in the monomictic Lake Estanya by combining microscopic analysis and two molecular
methods involving the amplification of 16S rDNA genes using primers for the domain Bacteria and subsequent restriction fragment length polymorphism (PCR–RFLP) and denaturing gradient gel electrophoresis (PCR–DGGE).
Both approaches revealed the vertical distribution of predominant microbial morphotypes and phylotypes in both holomictic
and stratified periods, respectively, and showed that variations in structure and composition of bacterial populations are
occurring in this lake as a function of depth and time. Through principal component analysis (PCA), these shifts could be
related to different physicochemical parameters with temperature, oxygen concentration, and the incident light being of paramount
importance as structuring variables. Comparison of RFLP and DGGE profiles by scoring similarities using the Jaccard coefficient
and then building a multidimensional scaling map (MDS) showed equivalent results. Both techniques revealed that bacterial
populations, present in the whole water column in the holomictic period, showed a high similarity with those located in the
deeper part of the lake in the stratified period, evidencing that other factors, both biotic and abiotic, should also be considered
as a force driving change in the composition of the bacterial community. Furthermore, DGGE analysis showed that sequences
from prominent bands were affiliated to members of four major phyla of the domain Bacteria: Cyanobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria, most of which corresponded to heterotrophic bacterial populations involved in carbon, sulfide, and nitrogen biogeochemical
cycles, which were indistinguishable under the light microscope. 相似文献
125.
Manteca A Alvarez R Salazar N Yagüe P Sanchez J 《Applied and environmental microbiology》2008,74(12):3877-3886
Despite the fact that most industrial processes for secondary metabolite production are performed with submerged cultures, a reliable developmental model for Streptomyces under these culture conditions is lacking. With the exception of a few species which sporulate under these conditions, it is assumed that no morphological differentiation processes take place. In this work, we describe new developmental features of Streptomyces coelicolor A3(2) grown in liquid cultures and integrate them into a developmental model analogous to the one previously described for surface cultures. Spores germinate as a compartmentalized mycelium (first mycelium). These young compartmentalized hyphae start to form pellets which grow in a radial pattern. Death processes take place in the center of the pellets, followed by growth arrest. A new multinucleated mycelium with sporadic septa (second mycelium) develops inside the pellets and along the periphery, giving rise to a second growth phase. Undecylprodigiosin and actinorhodin antibiotics are produced by this second mycelium but not by the first one. Cell density dictates how the culture will behave in terms of differentiation processes and antibiotic production. When diluted inocula are used, the growth arrest phase, emergence of a second mycelium, and antibiotic production are delayed. Moreover, pellets are less abundant and have larger diameters than in dense cultures. This work is the first to report on the relationship between differentiation processes and secondary metabolite production in submerged Streptomyces cultures. 相似文献
126.
Garrido N Pérez-Martos A Faro M Lou-Bonafonte JM Fernández-Silva P López-Pérez MJ Montoya J Enríquez JA 《The Biochemical journal》2008,414(1):93-102
Cisplatin accumulates in mitochondria, which are a major target for this drug in cancer cells. Thus alterations in mitochondrial function have been implicated in cancer cell resistance to chemotherapeutic agents. Moreover, cisplatin toxic side effects seem to be associated with mitochondrial injury in vivo and in vitro. In order to clarify the potential effect of cisplatin in mtDNA (mitochondrial DNA) maintenance and expression, we have analysed rat liver mtDNA and mtRNA (mitochondrial RNA) synthesis as well as their stability under the influence of in vivo treatment or in vitro exposure to cisplatin. We show that cisplatin causes a direct and significant impairment of mtDNA and mtRNA synthesis and decreases steady-state levels of mtRNAs in isolated mitochondria. Furthermore, in vivo treatment of the animals with cisplatin exerts a protective effect from the impairment of mtRNA metabolism caused by in vitro exposure to the drug, by means of increased mitochondrial GSH levels after in vivo cisplatin treatment. 相似文献
127.
Parvatrema australis (Szidat, 1962) Szidat, 1965 was described based on larval stages found in specimens of the mussel Mytilus edulis from the Buenos Aires Province, Argentina. Although Szidat later examined hundreds of mussels, this parasite has never been found again until now. In the present study, larval stages, including germinal sacs, found in mytilids from the Patagonian coast were identified as P. australis. Metacercariae were incubated in vitro at 39 degrees C in physiological solution for 18-20 hours, by which time 80% of the specimens had eggs. P. australis is redescribed, on the basis of infective metacercariae and adults obtained in the laboratory, and is reassigned to Gymnophallus Odhner, 1900, the genus in which it was originally described. The generic diagnosis of Gymnophallus is here amended to include as diagnostic characters the presence or absence of the lateral lips, the form and position of the vitellarium (compact or follicular) and the presence of a pars prostatica (i.e. prostatic cells open into proximal part of the ejaculatory duct). The validity of some characters (i.e. the presence of lateral lips of the oral sucker, the form of the vitellarium and excretory vesicle, the extent of the uterus) as diagnostic at the generic level within the family Gymnophallidae is discussed. It is proposed that the least unambiguous characters that can be used to distinguish gymnophallid genera include the position of the ovary, the presence of a ventral pit and a pars prostatica, and caecal diverticula. 相似文献
128.
Multifunctional nanoparticles--properties and prospects for their use in human medicine 总被引:3,自引:0,他引:3
A major aim of medicine has long been the early and accurate diagnosis of clinical conditions, providing an efficient treatment without secondary effects. With the emergence of nanotechnology, the achievement of this goal seems closer than ever. To this end, the development of novel materials and devices operating at the nanoscale range, such as nanoparticles, provides new and powerful tools for imaging, diagnosis and therapy. This review focuses on the significant improvements in performance that nanoparticles offer compared with existing technologies relevant to medicine. Specifically, we address the design of multifunctional nanoparticles as an alternative system for drug and gene delivery, which has great potential for therapy in areas, such as cancer and neuropathologies. Moreover, we discuss the controversy generated by the possible toxic health effects of nanoparticles. 相似文献
129.
Argueta-Donohué J Carrillo N Valdés-Reyes L Zentella A Aguirre-García M Becker I Gutiérrez-Kobeh L 《Experimental parasitology》2008,120(1):1-9
Dendritic cells (DC) and macrophages (Mφ) are well known as important effectors of the innate immune system and their ability to produce IL-12 indicates that they possess the potential of directing acquired immunity toward a Th1-biased response. Interestingly, the intracellular parasite Leishmania has been shown to selectively suppress Mφ IL-12 production and are DC the principal source of this cytokine. The molecular details of this phenomenon remain enigmatic. In the present study we examined the effect of Leishmania mexicana lipophosphoglycan (LPG) on the production of IL-12, TNF-α, and IL-10 and nuclear translocation of NF-κB. The results show that LPG induced more IL-12 in human DC than in monocytes. This difference was due in part to nuclear translocation of NF-κB, since LPG induced more translocation in DC than in monocytes. These results suggest that Leishmania LPG impairs nuclear translocation of NF-κB in monocytes with the subsequent decrease in IL-12 production. 相似文献
130.
Elena Diaz Almela Nuria Marbà Elvira Álvarez Rocío Santiago Regino Martínez Carlos M. Duarte 《Aquatic Botany》2008
Patch dynamics of the Mediterranean slow-growing seagrass Posidonia oceanica was studied in two shallow sites (3–10 m) of the Balearic Archipelago (Spain) through repeated censuses (1–2 year−1). In the sheltered site of Es Port Bay (Cabrera Island), initial patch density (October 2001) was low: 0.05 patches m−2, and the patch size (number of shoots) distribution was bimodal: most of the patches had less than 6 shoots or between 20 and 50 shoots. Mean patch recruitment in Es Port Bay (0.006 ± 0.002 patches m−2 year−1) exceeded mean patch loss (0.001 ± 0.001 patches m−2 year−1), yielding positive net patch recruitment (0.004 ± 0.003 patches m−2 year−1) and a slightly increased patch density 3 years later (July 2004, 0.06 patches m−2). In the exposed site of S’Estanyol, the initial patch density was higher (1.38 patches m−2, August 2003), and patch size frequency decreased exponentially with size. Patch recruitment (0.26 patches m−2 year−1) and loss (0.24 patches m−2 year−1) were high, yielding a slightly increased patch density in the area 1 year later (October 2004, 1.40 patches m−2). Most recruited patches consisted of rooting vegetative fragments of 1–2 shoots. Seedling recruitment was observed in Summer 2004 at both sites. Episodic, seedling recruitment comprised 30% and 25% of total patch recruitment in Es Port Bay and S’Estanyol, respectively. Patch survival increased with patch size and no direct removal was observed among patches of 5 shoots or more. Most patches grew along the study, shifting patch distribution towards larger sizes. Within the size range studied (1–150 shoots), absolute shoot recruitment (shoots year−1) increased linearly with patch size (R2 = 0.64, p < 4 × 10−5, N = 125), while specific shoot recruitment was constant (about 0.25 ± 0.05 year−1), although its variance was large for small patches. Given the slow growth rate and the high survival of patches with 5 or more shoots, even the low patch recruitment rates reported here could play a significant role in the colonisation process of P. oceanica. 相似文献