全文获取类型
收费全文 | 470篇 |
免费 | 32篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 17篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 8篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 30篇 |
2014年 | 25篇 |
2013年 | 35篇 |
2012年 | 46篇 |
2011年 | 32篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 26篇 |
2007年 | 15篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有502条查询结果,搜索用时 15 毫秒
111.
The present study was designed to develop and compare acyclovir containing nano-vesicular liposomes and niosomes based on cholesterol, soya L-alpha-lecithin and nonionic surfactant, span 20. The effort was made to study in vitro whether acyclovir-loaded nanovesicles could sustain the release of the drug by increasing residence time and thus, acyclovir could reduce its dose-related systemic toxicity. There were good vesicular distributions in both of the niosomes and the liposomes. The obtained vesicles were within 1 microm and about 35% of them were within a size of 100 nm. The percentage of drug loading varied and the niosomal vesicles contained more drug as compared with the liposomes. When the in vitro drug release was compared, it was found that the liposomes released about 90% drug in 150 min whereas the drug release was just 50% from the niosomal vesicles in 200 min. Again, the niosomes showed better stability compared with the liposomes. Thus, niosome could be a better choice for intravenous delivery of acyclovir. 相似文献
112.
Priyabrata Mukherjee Resham Bhattacharya Nancy Bone Yean K Lee Chitta Ranjan Patra Shanfeng Wang Lichun Lu Charla Secreto Pataki C Banerjee Michael J Yaszemski Neil E Kay Debabrata Mukhopadhyay 《Journal of nanobiotechnology》2007,5(1):1-13
Background
Neuroblastoma, a frequently occurring solid tumour in children, remains a therapeutic challenge as existing imaging tools are inadequate for proper and accurate diagnosis, resulting in treatment failures. Nanoparticles have recently been introduced to the field of cancer research and promise remarkable improvements in diagnostics, targeting and drug delivery. Among these nanoparticles, quantum dots (QDs) are highly appealing due to their manipulatable surfaces, yielding multifunctional QDs applicable in different biological models. The biocompatibility of these QDs, however, remains questionable. 相似文献113.
Jayadeep Patra Mehak Bhatia Wilson Suraweera Shaun K. Morris Cyril Patra Prakash C. Gupta Prabhat Jha 《PLoS medicine》2015,12(6)
Background
According to WHO Global Health Estimates, tuberculosis (TB) is among the top ten causes of global mortality and ranks second after cardiovascular disease in most high-burden regions. In this systematic review and meta-analysis, we investigated the role of second-hand smoke (SHS) exposure as a risk factor for TB among children and adults.Methods and Findings
We performed a systematic literature search of PubMed, Embase, Scopus, Web of Science, and Google Scholar up to August 31, 2014. Our a priori inclusion criteria encompassed only original studies where latent TB infection (LTBI) and active TB disease were diagnosed microbiologically, clinically, histologically, or radiologically. Effect estimates were pooled using fixed- and random-effects models. We identified 18 eligible studies, with 30,757 children and 44,432 adult non-smokers, containing SHS exposure and TB outcome data for inclusion in the meta-analysis. Twelve studies assessed children and eight studies assessed adult non-smokers; two studies assessed both populations. Summary relative risk (RR) of LTBI associated with SHS exposure in children was similar to the overall effect size, with high heterogeneity (pooled RR 1.64, 95% CI 1.00–2.83). Children showed a more than 3-fold increased risk of SHS-associated active TB (pooled RR 3.41, 95% CI 1.81–6.45), which was higher than the risk in adults exposed to SHS (summary RR 1.32, 95% CI 1.04–1.68). Positive and significant exposure–response relationships were observed among children under 5 y (RR 5.88, 95% CI 2.09–16.54), children exposed to SHS through any parent (RR 4.20, 95% CI 1.92–9.20), and children living under the most crowded household conditions (RR 5.53, 95% CI 2.36–12.98). Associations for LTBI and active TB disease remained significant after adjustment for age, biomass fuel (BMF) use, and presence of a TB patient in the household, although the meta-analysis was limited to a subset of studies that adjusted for these variables. There was a loss of association with increased risk of LTBI (but not active TB) after adjustment for socioeconomic status (SES) and study quality. The major limitation of this analysis is the high heterogeneity in outcomes among studies of pediatric cases of LTBI and TB disease.Conclusions
We found that SHS exposure is associated with an increase in the relative risk of LTBI and active TB after controlling for age, BMF use, and contact with a TB patient, and there was no significant association of SHS exposure with LTBI after adjustment for SES and study quality. Given the high heterogeneity among the primary studies, our analysis may not show sufficient evidence to confirm an association. In addition, considering that the TB burden is highest in countries with increasing SHS exposure, it is important to confirm these results with higher quality studies. Research in this area may have important implications for TB and tobacco control programs, especially for children in settings with high SHS exposure and TB burden. 相似文献114.
115.
This paper presents the results of a longitudinal intervention study carried out in the Davao del Norte province of the Philippines. The intervention, tested through a quasi-experimental design, consisted of training of family planning service providers in information exchange and training of their supervisors in facilitative supervision. The training intervention significantly improved providers' knowledge and quality of care received by clients. Moreover, good quality care received by clients at the time of initiating contraception use increased the likelihood of contraceptive continuation and decreased the likelihood of both having an unintended pregnancy and an unwanted birth. However, comparison of women in the experimental group with those in the control group did not show any significant effect of provider-level training intervention on these client-level outcomes. The reasons for this conundrum and the implications for quality of care are discussed. 相似文献
116.
117.
118.
Eugene Valkov Saumya Shree Gupta Stephen Hare Anna Helander Pietro Roversi Myra McClure Peter Cherepanov 《Nucleic acids research》2009,37(1):243-255
Establishment of the stable provirus is an essential step in retroviral replication, orchestrated by integrase (IN), a virus-derived enzyme. Until now, available structural information was limited to the INs of human immunodeficiency virus type 1 (HIV-1), avian sarcoma virus (ASV) and their close orthologs from the Lentivirus and Alpharetrovirus genera. Here, we characterized the in vitro activity of the prototype foamy virus (PFV) IN from the Spumavirus genus and determined the three-dimensional structure of its catalytic core domain (CCD). Recombinant PFV IN displayed robust and almost exclusively concerted integration activity in vitro utilizing donor DNA substrates as short as 16 bp, underscoring its significance as a model for detailed structural studies. Comparison of the HIV-1, ASV and PFV CCD structures highlighted both conserved as well as unique structural features such as organization of the active site and the putative host factor binding face. Despite possessing very limited sequence identity to its HIV counterpart, PFV IN was sensitive to HIV IN strand transfer inhibitors, suggesting that this class of inhibitors target the most conserved features of retroviral IN-DNA complexes. 相似文献
119.
Shachindra K. Pandey Kunwar Digvijay Narayan Saumya Bandyopadhyay Kinshuk C. Nayak Subrata K. Das 《Current microbiology》2009,58(5):516-521
A bacterial isolate S23 capable of oxidizing thiosulfate was isolated from a sulfur spring. Strain S23 is gram-negative, aerobic,
and motile. The G + C content of DNA is 61.4 mol%. The fatty acid composition and phylogenetic analysis of the 16S rRNA gene
sequence of strain S23 showed that it is related to the members of the genus Comamonas, and most closely related to Comamonas testosteroni (99.9% sequence similarity). The isolate S23 exhibited thiosulfate oxidation under a mixotrophic growth condition. Polymerase
chain reaction (PCR) using soxB-specific primers and DNA sequencing showed the presence of the soxB gene. This is the first report in Comamonas sp. showing thiosulfate oxidation under a mixotrophic growth condition. 相似文献
120.