全文获取类型
收费全文 | 2312篇 |
免费 | 148篇 |
国内免费 | 2篇 |
专业分类
2462篇 |
出版年
2023年 | 19篇 |
2022年 | 28篇 |
2021年 | 63篇 |
2020年 | 29篇 |
2019年 | 52篇 |
2018年 | 43篇 |
2017年 | 39篇 |
2016年 | 63篇 |
2015年 | 97篇 |
2014年 | 117篇 |
2013年 | 169篇 |
2012年 | 174篇 |
2011年 | 162篇 |
2010年 | 110篇 |
2009年 | 90篇 |
2008年 | 117篇 |
2007年 | 111篇 |
2006年 | 109篇 |
2005年 | 89篇 |
2004年 | 67篇 |
2003年 | 51篇 |
2002年 | 55篇 |
2001年 | 61篇 |
2000年 | 29篇 |
1999年 | 39篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 16篇 |
1995年 | 17篇 |
1994年 | 9篇 |
1993年 | 15篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 29篇 |
1989年 | 23篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1977年 | 12篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1973年 | 13篇 |
1967年 | 8篇 |
排序方式: 共有2462条查询结果,搜索用时 15 毫秒
71.
72.
Madhura S. Mehta Sonia C. Dolfi Roman Bronfenbrener Erhan Bilal Chunxia Chen Dirk Moore Yong Lin Hussein Rahim Seena Aisner Romona D. Kersellius Jessica Teh Suzie Chen Deborah L. Toppmeyer Dan J. Medina Shridar Ganesan Alexei Vazquez Kim M. Hirshfield 《PloS one》2013,8(7)
Several epidemiological studies have suggested a link between melanoma and breast cancer. Metabotropic glutamate receptor 1 (GRM1), which is involved in many cellular processes including proliferation and differentiation, has been implicated in melanomagenesis, with ectopic expression of GRM1 causing malignant transformation of melanocytes. This study was undertaken to evaluate GRM1 expression and polymorphic variants in GRM1 for associations with breast cancer phenotypes. Three single nucleotide polymorphisms (SNPs) in GRM1 were evaluated for associations with breast cancer clinicopathologic variables. GRM1 expression was evaluated in human normal and cancerous breast tissue and for in vitro response to hormonal manipulation. Genotyping was performed on genomic DNA from over 1,000 breast cancer patients. Rs6923492 and rs362962 genotypes associated with age at diagnosis that was highly dependent upon the breast cancer molecular phenotype. The rs362962 TT genotype also associated with risk of estrogen receptor or progesterone receptor positive breast cancer. In vitro analysis showed increased GRM1 expression in breast cancer cells treated with estrogen or the combination of estrogen and progesterone, but reduced GRM1 expression with tamoxifen treatment. Evaluation of GRM1 expression in human breast tumor specimens demonstrated significant correlations between GRM1 staining with tissue type and molecular features. Furthermore, analysis of gene expression data from primary breast tumors showed that high GRM1 expression correlated with a shorter distant metastasis-free survival as compared to low GRM1 expression in tamoxifen-treated patients. Additionally, induced knockdown of GRM1 in an estrogen receptor positive breast cancer cell line correlated with reduced cell proliferation. Taken together, these findings suggest a functional role for GRM1 in breast cancer. 相似文献
73.
A population of multipotent stem cells capable of differentiating into neurons and glia has been isolated from adult intestine in humans and rodents. While these cells may provide a pool of stem cells for neurogenesis in the enteric nervous system (ENS), such a function has been difficult to demonstrate in vivo. An extensive study by Joseph et al. involving 108 rats and 51 mice submitted to various insults demonstrated neuronal uptake of thymidine analog BrdU in only 1 rat. Here we introduce a novel approach to study neurogenesis in the ENS using an ex vivo organotypic tissue culturing system. Culturing longitudinal muscle and myenteric plexus tissue, we show that the enteric nervous system has tremendous replicative capacity with the majority of neural crest cells demonstrating EdU uptake by 48 hours. EdU+ cells express both neuronal and glial markers. Proliferation appears dependent on the PTEN/PI3K/Akt pathway with decreased PTEN mRNA expression and increased PTEN phosphorylation (inactivation) corresponding to increased Akt activity and proliferation. Inhibition of PTEN with bpV(phen) augments proliferation while , a PI3K inhibitor, blocks it. These data suggest that the ENS is capable of neurogenesis in a PTEN dependent manner. LY294002相似文献
74.
75.
Shankar Prinja Pankaj Bahuguna Pavitra Mohan Sarmila Mazumder Sunita Taneja Nita Bhandari Henri van den Hombergh Rajesh Kumar 《PloS one》2016,11(1)
Introduction
Despite the evidence for preventing childhood morbidity and mortality, financial resources are cited as a constraint for Governments to scale up the key health interventions in some countries. We evaluate the cost effectiveness of implementing IMNCI program in India from a health system and societal perspective.Methods
We parameterized a decision analytic model to assess incremental cost effectiveness of IMNCI program as against routine child health services for infant population at district level in India. Using a 15-years time horizon from 2007 to 2022, we populated the model using data on costs and effects as found from a cluster-randomized trial to assess effectiveness of IMNCI program in Haryana state. Effectiveness was estimated as reduction in infant illness episodes, deaths and disability adjusted life years (DALY). Incremental cost per DALY averted was used to estimate cost effectiveness of IMNCI. Future costs and effects were discounted at a rate of 3%. Probabilistic sensitivity analysis was undertaken to estimate the probability of IMNCI to be cost effective at varying willingness to pay thresholds.Results
Implementation of IMNCI results in a cumulative reduction of 57384 illness episodes, 2369 deaths and 76158 DALYs among infants at district level from 2007 to 2022. Overall, from a health system perspective, IMNCI program incurs an incremental cost of USD 34.5 (INR 1554) per DALY averted, USD 34.5 (INR 1554) per life year gained, USD 1110 (INR 49963) per infant death averted. There is 90% probability for ICER to be cost effective at INR 2300 willingness to pay, which is 5.5% of India’s GDP per capita. From a societal perspective, IMNCI program incurs an additional cost of USD 24.1 (INR 1082) per DALY averted, USD 773 (INR 34799) per infant death averted and USD 26.3 (INR 1183) per illness averted in during infancy.Conclusion
IMNCI program in Indian context is very cost effective and should be scaled-up as a major child survival strategy. 相似文献76.
77.
Qingling Zhang Michael Cox Zhike Liang Folke Brinkmann Paul A Cardenas Rachael Duff Pankaj Bhavsar William Cookson Miriam Moffatt Kian Fan Chung 《PloS one》2016,11(4)
BackgroundThe lower airways harbor a community of bacterial species which is altered in asthma.ObjectivesWe examined whether the lower airway microbiota were related to measures of asthma severity.MethodsWe prospectively recruited 26 severe asthma, 18 non-severe asthma and 12 healthy subjects. DNA was extracted from induced sputum and PCR amplification of the V3-V5 region of bacterial 16S rRNA gene was performed.ResultsWe obtained 138,218 high quality sequences which were rarefied at 133 sequences/sample. Twenty OTUs had sequences ≥1% of total. There were marked differences in the distribution of Phyla between groups (P = 2.8x10-118). Bacteroidetes and Fusobacteria were reduced in non-severe and severe asthmatic groups. Proteobacteria were more common in non-severe asthmatics compared to controls (OR = 2.26; 95% CI = 1.94–2.64) and Firmicutes were increased in severe asthmatics compared to controls (OR = 2.15; 95%CI = 1.89–2.45). Streptococcal OTUs amongst the Firmicutes were associated with recent onset asthma, rhinosinusitis and sputum eosinophilia.ConclusionsSputum microbiota in severe asthma differs from healthy controls and non-severe asthmatics, and is characterized by the presence of Streptococcus spp with eosinophilia. Whether these organisms are causative for the pathophysiology of asthma remains to be determined. 相似文献
78.
79.
Neha Bhardwaj Sanjeev K. Bhardwaj Jyotsana Mehta Girish C. Mohanta Akash Deep 《Analytical biochemistry》2016
Bacteriophages are a class of viruses that specifically infect and replicate within a bacterium. They possess inherent affinity and specificity to the particular bacterial cells. This property of bacteriophages makes them an attractive biorecognition element in the field of biosensor development. In this work, we report the use of an immobilized bacteriophage for the development of a highly sensitive electrochemical sensor for Staphylococcus arlettae, bacteria from the pathogenic family of coagulase-negative staphylococci (CNS). The specific bacteriophages were covalently immobilized on the screen-printed graphene electrodes. Thus, the fabricated bacteriophage biosensor displayed quantitative response for the target bacteria (S. arlettae) for a broad detection range (2.0–2.0 × 106 cfu). A fast response time (2 min), low limit of detection (2 cfu), specificity, and stability over a prolonged period (3 months) are some of the important highlights of the proposed sensor. The practical utility of the developed sensor has been demonstrated by the analysis of S. arlettae in spiked water and apple juice samples. 相似文献
80.
B?Raghunath?Reddy Swati?Maitra Priya?Jhelum K?Praveen?Kumar Pankaj?K?Bagul Gagandeep?Kaur Sanjay?K?Banerjee Arvind?Kumar Sumana?ChakravartyEmail author 《Journal of biosciences》2016,41(3):407-417
Hyperglycaemia in diabetes is either caused by reduced availability of insulin (type 1 diabetes, T1D) or insulin resistance to the cells (type 2 diabetes, T2D). In recent years, the prevalence of T2D has increased to an alarming proportion, encompassing 95% of the total diabetic burden, probably due to economy-driven changes in lifestyle. Recent epidemiological studies show comorbid depression, anxiety and related mental illness. To explore the molecular mechanisms underlying this comorbid conditions, we used Sprague–Dawley rats on high-fructose diet for 8 weeks to induce prediabetic condition. Rats with this metabolic syndrome also showed hyper-anxiety when they were subjected to anxiety-related behavioural assays. Rats were administered with resveratrol, an activator of sirtuins, and metformin, a standard antidiabetic drug, simultaneously with fructose. We observed that resveratrol was more effective in protecting from both the metabolic (prediabetic) and affective (anxiety) disorders than metformin. Molecular studies showed that recovery was associated with the upregulation of few nuclear sirtuins that act epigenetically – Sirt 1 and 7, which were significantly attenuated in the striatum of prediabetic rats. In conclusion, our study showed that hyper-anxiety associated with prediabetic condition is ameliorated by resveratrol through modulation of sirtuins, which is more or less similar to metformin. 相似文献