全文获取类型
收费全文 | 2768篇 |
免费 | 164篇 |
国内免费 | 16篇 |
专业分类
2948篇 |
出版年
2023年 | 21篇 |
2022年 | 62篇 |
2021年 | 145篇 |
2020年 | 66篇 |
2019年 | 71篇 |
2018年 | 71篇 |
2017年 | 74篇 |
2016年 | 95篇 |
2015年 | 148篇 |
2014年 | 180篇 |
2013年 | 208篇 |
2012年 | 195篇 |
2011年 | 174篇 |
2010年 | 135篇 |
2009年 | 107篇 |
2008年 | 129篇 |
2007年 | 134篇 |
2006年 | 113篇 |
2005年 | 97篇 |
2004年 | 82篇 |
2003年 | 73篇 |
2002年 | 70篇 |
2001年 | 54篇 |
2000年 | 46篇 |
1999年 | 46篇 |
1998年 | 13篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 27篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1980年 | 9篇 |
1978年 | 13篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1971年 | 7篇 |
1967年 | 9篇 |
排序方式: 共有2948条查询结果,搜索用时 15 毫秒
141.
142.
Prabhat Kumar Talukdar Mizanur Rahman Mahdia Rahman Ashikun Nabi Zhahirul Islam M. Mahfuzul Hoque Hubert P. Endtz Mohammad Aminul Islam 《PloS one》2013,8(4)
Background
Unsafe water supplies continue to raise public health concerns, especially in urban areas in low resource countries. To understand the extent of public health risk attributed to supply water in Dhaka city, Bangladesh, Escherichia coli isolated from tap water samples collected from different locations of the city were characterized for their antibiotic resistance, pathogenic properties and genetic diversity.Methodology/Principal Findings
A total of 233 E. coli isolates obtained from 175 tap water samples were analysed for susceptibility to 16 different antibiotics and for the presence of genes associated with virulence and antibiotic resistance. Nearly 36% (n = 84) of the isolates were multi-drug(≥3 classes of antibiotics) resistant (MDR) and 26% (n = 22) of these were positive for extended spectrum β-lactamase (ESBL). Of the 22 ESBL-producers, 20 were positive for bla CTX-M-15, 7 for bla OXA-1-group (all had bla OXA-47) and 2 for bla CMY-2. Quinolone resistance genes, qnrS and qnrB were detected in 6 and 2 isolates, respectively. Around 7% (n = 16) of the isolates carried virulence gene(s) characteristic of pathogenic E. coli; 11 of these contained lt and/or st and thus belonged to enterotoxigenic E. coli and 5 contained bfp and eae and thus belonged to enteropathogenic E. coli. All MDR isolates carried multiple plasmids (2 to 8) of varying sizes ranging from 1.2 to >120 MDa. Ampicillin and ceftriaxone resistance were co-transferred in conjugative plasmids of 70 to 100 MDa in size, while ampicillin, trimethoprim-sulfamethoxazole and tetracycline resistance were co-transferred in conjugative plasmids of 50 to 90 MDa. Pulsed-field gel electrophoresis analysis revealed diverse genetic fingerprints of pathogenic isolates.Significance
Multi-drug resistant E. coli are wide spread in public water supply in Dhaka city, Bangladesh. Transmission of resistant bacteria and plasmids through supply water pose serious threats to public health in urban areas. 相似文献143.
Md. Atiqur Rahman Khokon Mohammad Abdus Salam Fabien Jammes Wenxiu Ye Mohammad Anowar Hossain Eiji Okuma 《Bioscience, biotechnology, and biochemistry》2017,81(7):1394-1400
Salicylic acid (SA) induces stomatal closure sharing several components with abscisic acid (ABA) and methyl jasmonate (MeJA) signaling. We have previously shown that two guard cell-preferential mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate ABA signaling and MeJA signaling in Arabidopsis thaliana. In this study, we examined whether these two MAPKs are involved in SA-induced stomatal closure using genetic mutants and a pharmacological, MAPKK inhibitor. Salicylic acid induced stomatal closure in mpk9 and mpk12 single mutants but not in mpk9 mpk12 double mutants. The MAPKK inhibitor PD98059 inhibited SA-induced stomatal closure in wild-type plants. Salicylic acid induced extracellular reactive oxygen species (ROS) production, intracellular ROS accumulation, and cytosolic alkalization in the mpk9, mpk12, and mpk9 mpk12 mutants. Moreover, SA-activated S-type anion channels in guard cells of wild-type plants but not in guard cells of mpk9 mpk12 double mutants. These results imply that MPK9 and MPK12 are positive regulators of SA signaling in Arabidopsis guard cells. 相似文献
144.
145.
Dorcas Ibukun Akinloye Regina Ngozi Ugbaja Oluwatosin Adebisi Dosumu Samson Adisa Rahman Emmanuel Ifeanyichukwu Ugwor Adewale Segun James Olushola Oladapo Oyesile Mary Bunmi Bada 《Biochemistry and Biophysics Reports》2021
This present research investigated variations in lipid profiles and important biomarkers of tissue damage in response to graded concentrations of alcohol administration in male Wistar rats. Group A (control) received distilled water while group B, C and D received 30%, 40% and 50% (v/v) alcohol respectively. Five rats each from groups A-D were sacrificed after day(s) 1, 7, 14, 21 and 28 of administration. A significant increase was observed at day 28 for serum cholesterol by 79% (group B), 78% (group C) and 47% (group D) together with serum phospholipid 58% (group B), 50% (group C) and 92% (group D). Serum triacylglycerol increased by 71% (group B), 43% (group C) and 16% (group D) at day 21, while concentration of serum albumin decreased at day 28 by 40.9% (group B), 50.2% (group C), 53.3% (group D) respectively when compared with control (group A). Serum aminotransferases and alkaline phosphatase specific activities, as well as creatinine and uric acid concentration increased in a concentration-dependent manner, following alcohol administration. Though most of these effects induced by alcohol were time- and concentration-dependent, 40% alcohol appear to be more stable, giving results consistent with alcohol-induced damages, with minimal mortality. This study therefore further validated dyslipidemia and imbalance in clinical biomarkers as hallmarks of tissue damage induced by excessive alcohol consumption with an insight on the time- and concentration-response relationship between alcohol consumption and its toxicity. 相似文献
146.
Guillaume Ghisbain Jeffrey D. Lozier Sarthok Rasique Rahman Briana D. Ezray Li Tian Jonah M. Ulmer Sam D. Heraghty James P. Strange Pierre Rasmont Heather M. Hines 《Systematic Entomology》2020,45(3):635-652
Phenotypic polymorphism can constitute an inherent challenge for species delimitation. This issue is exemplified in bumble bees (Bombus), where species can exhibit high colour variation across their range, but otherwise exhibit little morphological variation to distinguish them from close relatives. We examine the species status of one of the most abundant North American bumble bees, Bombus bifarius Cresson, which historically comprised two major taxa, bifarius s.s. and nearcticus. These lineages are recognized primarily by red and black variation in their mid-abdominal coloration; however, a continuum from black (nearcticus) to red (bifarius s.s.) variation has led to their historic synonymization. Integrating mitochondrial and nuclear data and whole-genome sequencing, we reveal a high level of both mitochondrial and nuclear divergence delimiting two morphologically cryptic species – the red bifarius s.s. and the colour-variable (black to red) nearcticus. Population genomic analysis supports an absence of recent genomic admixture and a strong population structure between the two clades, even in sympatry. Species distribution models predict partially differentiated niches between the genetically inferred clades with annual precipitation being a leading differentiating variable. The bifarius s.s. lineage also occupies significantly higher elevations, with regions of sympatry being among the highest elevations in nearcticus. Our data also support a subspecies-level divergence between the broadly distributed nearcticus and the island population vancouverensis. In this paper, we formally recognize the two species, Bombus bifarius Cresson and Bombus vancouverensis Cresson, the latter including the subspecies B. vancouverensis vancouverensis comb.n. and B. vancouverensis nearcticus comb.n ., with vancouverensis the name bearer due to year priority. 相似文献
147.
148.
Farhan Haq Salmaan Sharif Adnan Khurshid Aamer Ikram Imran Shabbir Muhammad Salman Abdul Ahad Muhammad Suleman Rana Aroosha Raja Nazish Badar Hanaa Tashkandi Turki Al Amri Esam I. Azhar Mohammed S. Almuhayawi Steve Harakeh Muhammad Faraz Arshad Malik 《Saudi Journal of Biological Sciences》2021,28(1):942
149.
Purpose
Evidence is inconsistent regarding alcohol and pancreatic cancer risk, although heavy drinking may increase risk.Methods
A population-based case-control study was conducted using 345 pancreas cancer cases diagnosed 2011–2012 and 1,285 frequency-matched controls from Ontario, Canada. Logistic regression was used to evaluate alcohol consumption and pancreatic cancer risk; data was also stratified by sex and smoking status to assess interaction.Results
Alcohol consumption was not associated with pancreatic cancer risk (age-adjusted odds ratio=0.78, 95% CI: 0.58, 1.05 for 1 - 3 drinks/week; age-adjusted odds ratio=0.86, 95% CI: 0.63, 1.17 for 4 - 20 drinks/week), however there was a non-significant increased risk for heavy drinkers consuming ≥21 drinks/week (age-adjusted odds ratio=1.35, 95% CI: 0.81, 2.27). Cigarette smoking modified the alcohol-cancer relationship; among current smokers, heavy alcohol consumption was associated with a significantly increased pancreatic cancer risk (age-adjusted odds ratio=4.04, 95% CI: 1.58, 10.37), whereas this significant association with heavy drinking was not observed among non-smokers (age-adjusted odds ratio=2.01, 95% CI: 0.50, 8.18). Furthermore, light – moderate alcohol intake was associated with increased pancreas cancer risk among current smokers.Conclusions
While alcohol was not significantly associated with pancreatic cancer risk, smoking status modified this relationship such that among current smokers, alcohol intake was associated with a greater than two-fold increased risk of pancreatic cancer. The results should be interpreted with caution due to small sample sizes within subgroups and correction for multiple comparisons should be considered. These findings should be replicated in larger studies where more precise estimates of risk can be obtained. 相似文献150.
Eleanor K. Mishra John P. Corcoran Robert J. Hallifax John Stradling Nicholas A. Maskell Najib M. Rahman 《PloS one》2015,10(4)