首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   312篇
  免费   14篇
  326篇
  2023年   2篇
  2022年   8篇
  2021年   14篇
  2020年   6篇
  2019年   8篇
  2018年   9篇
  2017年   8篇
  2016年   20篇
  2015年   24篇
  2014年   12篇
  2013年   13篇
  2012年   19篇
  2011年   25篇
  2010年   15篇
  2009年   12篇
  2008年   20篇
  2007年   16篇
  2006年   23篇
  2005年   12篇
  2004年   10篇
  2003年   5篇
  2002年   3篇
  2001年   2篇
  2000年   1篇
  1999年   3篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1993年   2篇
  1992年   1篇
  1991年   3篇
  1990年   5篇
  1989年   3篇
  1988年   1篇
  1985年   1篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1977年   2篇
  1975年   2篇
  1973年   1篇
  1971年   1篇
  1963年   1篇
排序方式: 共有326条查询结果,搜索用时 15 毫秒
261.
Arrowroot (Maranta arundinacea. L) is an underutilized local crop potentially to be developed as carbohydrate source and functional food in Indonesia. The objectives of this research are to evaluate the immunostimulatory effects of arrowroot extracts in vitro by using animal cell culture techniques, and in vivo by using BALB/c mice. The arrowroot tuber extracts were prepared by heat-treatment at 121 °C for 20 min in distilled water. The IgM production stimulatory activity of arrowroot tuber extracts against human hybridoma HB4C5 cells and mouse splenocytes was assessed. The result indicated that the arrowroot tuber extract stimulated IgM production by HB4C5 cells and immunoglobulin (IgG, IgA and IgM) production by splenocytes in vitro. In addition, the arrowroot tuber extracts strongly enhanced interferon γ production by splenocytes. In vivo study indicated that the diet containing arrowroot extracts increased the serum IgG, IgA and IgM levels in mice. These results revealed that the arrowroot tuber extracts have immunostimulatory effects in vivo as well as in vitro.  相似文献   
262.
It is widely accepted that sea level changes intermittently inundated the Sunda Shelf throughout the Pleistocene, separating Java, Sumatra and Borneo from the Malay Peninsula and from each other. On this basis, the dynamics of the biodiversity hotspot of Sundaland is consistently regarded as solely contingent on glacial sea level oscillations, with interglacial highstands creating intermittent dispersal barriers between disjunct landmasses. However, recent findings on the geomorphology of the currently submerged Sunda shelf suggest that it subsided during the Pleistocene and that, over the Late Pliocene and Quaternary, is was never submerged prior to Marine Isotope Stage 11 (MIS 11, 400 ka). This would have enabled the dispersal of terrestrial organisms regardless of sea level variations until 400 ka and hampered movements thereafter, at least during interglacial periods. Existing phylogeographic data for terrestrial organisms conform to this scenario: available divergence time estimates reveal an 8- to 9-fold increase in the rate of vicariance between landmasses of Sundaland after 400 ka, corresponding to the onset of episodic flooding of the Sunda shelf. These results highlight how reconsidering the paleogeographic setting of Sundaland challenges understanding the mechanisms generating Southeast Asian biodiversity.  相似文献   
263.
The lipoglycoproteins of the WNT family act on seven transmembrane-spanning Class Frizzled receptors. Here, we show that WNT-5A evokes a proliferative response in a mouse microglia-like cell line (N13), which is sensitive to pertussis toxin, thus implicating the involvement of heterotrimeric G proteins of the Gi/o family. We continue to show that WNT-5A stimulation of N13 membranes and permeabilized cells evokes the exchange of GDP for GTP of pertussis toxin-sensitive G proteins employing [γ-35S]GTP assay and activity state-specific antibodies to GTP-bound Gi proteins. Our functional analysis of the PTX-sensitivity of WNT-induced G protein activation and PCR analysis of G protein and FZD expression patterns suggest that WNT-5A stimulation leads to the activation of Gi2/3 proteins in N13 cells possibly mediated by FZD5, the predominant FZD expressed. In summary, we provide for the first time molecular proof that WNT-5A stimulation results in the activation of heterotrimeric Gi2/3 proteins in mammalian cells with physiological protein stochiometry.  相似文献   
264.
Cyanobacteria (blue-green algae) are widely distributed Gram-negative oxygenic photosynthetic prokaryotes with a long evolutionary history. They have potential applications such as nutrition (food supplements and fine chemicals), in agriculture (as biofertilizer and in reclamation of saline USAR soils) and in wastewater treatment (production of exopolysaccharides and flocculants). In addition, they also produce wide variety of chemicals not needed for their normal growth (secondary metabolites) which show powerful biological activities such as strong antiviral, antibacterial, antifungal, antimalarial, antitumoral and anti-inflammatory activities useful for therapeutic purposes. In recent years, cyanobacteria have gained interest for producing biofuels (both biomass and H2 production). Because of their simple growth needs, it is potentially cost-effective to exploit cyanobacteria for the production of recombinant compounds of medicinal and commercial value. Recent advances in culture, screening and genetic engineering techniques have opened new ways to exploit the potential of cyanobacteria. This review analyses the sustainability of cyanobacteria to solve global problems such as food, energy and environmental degradation. It emphasizes the need to adopt multidisciplinary approaches and a multi-product production (biorefinery) strategy to harness the maximum benefit of cyanobacteria.  相似文献   
265.

Background

Soil-transmitted helminths (STHs) infect over a billion individuals worldwide. In India, 241 million children are estimated to need deworming to avert the negative consequences STH infections can have on child health and development. In February-April 2011, 17 million children in Bihar State were dewormed during a government-led school-based deworming campaign. Prior to programme implementation, a study was conducted to assess STH prevalence in the school-age population to direct the programme. The study also investigated risk factors for STH infections, including caste, literacy, and defecation and hygiene practices, in order to inform the development of complementary interventions.

Methods

A cross-sectional survey was conducted among children in 20 schools in Bihar. In addition to providing stool samples for identification of STH infections, children completed a short questionnaire detailing their usual defecation and hand-hygiene practices. Risk factors for STH infections were explored.

Results

In January-February 2011, 1279 school children aged four to seventeen provided stool samples and 1157 children also completed the questionnaire. Overall, 68% of children (10-86% across schools) were infected with one or more soil-transmitted helminth species. The prevalence of ascariasis, hookworm and trichuriasis was 52%, 42% and 5% respectively. The majority of children (95%) practiced open defecation and reported most frequently cleansing hands with soil (61%). Increasing age, lack of maternal literacy and certain castes were independently associated with hookworm infection. Absence of a hand-washing station at the schools was also independently associated with A. lumbricoides infection.

Conclusions

STH prevalence in Bihar is high, and justifies mass deworming in school-aged children. Open defecation is common-place and hands are often cleansed using soil. The findings reported here can be used to help direct messaging appropriate to mothers with low levels of literacy and emphasise the importance of water and sanitation in the control of helminths and other diseases.  相似文献   
266.
267.
268.

Nondermatophyte molds (NDM) and dematiaceous molds are less frequently implicated as the etiological agents of tinea-like infections of the foot. Among the etiological agents, Hendersonula toruloidea (now, Nattrassia mangiferae), Scytalidium hyalinum, Alternaria species (spp.), and Fusarium spp. are infrequently associated with foot mycoses. Nodulisporium (N.) spp. is a mitosporic NDM, which has been implicated in human infections like cerebral phaeohyphomycosis and allergic fungal sinusitis. Here, we report N. griseobrunneum in a 9-year-old female with mycosis of the plantar surface of foot mimicking a tinea pedis. Potassium hydroxide mount of skin specimen demonstrated dichotomous branching septate hyphae. Fungal culture and molecular sequencing established N. griseobrunneum as the etiological agent. Antifungal susceptibility testing revealed lower MICs to all seven drugs tested including itraconazole (ITR). The patient was treated with ITR and topical terbinafine. To the best of our knowledge, this is the first communication depicting molecular confirmation of the etiologic agent and antifungal susceptibility data of the mycosis of the plantar surface of foot owing to N. griseobrunneum from India.

  相似文献   
269.
Positron emission tomography (PET) neuroimaging and behavioral assays in rodents are widely used in neuroscience. PET gives insights into the molecular processes of neuronal communication, and behavioral methods analyze the actions that are associated with such processes. These methods have not been directly integrated, because PET studies in animals have until now required general anesthesia to immobilize the subject, which precludes behavioral studies. We present a method for imaging awake, behaving rats with PET that allows the simultaneous study of behavior. Key components include the 'rat conscious animal PET' or RatCAP, a miniature portable PET scanner that is mounted on the rat's head, a mobility system that allows considerable freedom of movement, radiotracer administration techniques and methods for quantifying behavior and correlating the two data sets. The simultaneity of the PET and behavioral data provides a multidimensional tool for studying the functions of different brain regions and their molecular constituents.  相似文献   
270.
The aims of this study were to demonstrate the feasibility of centrally collecting and processing high-quality cerebrospinal fluid (CSF) samples for proteomic studies within a multi-center consortium and to identify putative biomarkers for medulloblastoma in CSF. We used 2-DE to investigate the CSF proteome from 33 children with medulloblastoma and compared it against the CSF proteome from 25 age-matched controls. Protein spots were subsequently identified by a combination of in-gel tryptic digestion and MALDI-TOF TOF MS analysis. On average, 160 protein spots were detected by 2-DE and 76 protein spots corresponding to 25 unique proteins were identified using MALDI-TOF. Levels of prostaglandin D2 synthase (PGD2S) were found to be six-fold decreased in the tumor samples versus control samples (p<0.00001). These data were further validated using ELISA. Close examination of PGD2S spots revealed the presence of complex sialylated carbohydrates at residues Asn(78) and Asn(87) . Total PGD2S levels are reduced six-fold in the CSF of children with medulloblastoma most likely representing a host response to the presence of the tumor. In addition, our results demonstrate the feasibility of performing proteomic studies on CSF samples collected from patients at multiple institutions within the consortium setting.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号