全文获取类型
收费全文 | 261篇 |
免费 | 18篇 |
专业分类
279篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 16篇 |
2019年 | 20篇 |
2018年 | 16篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 27篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 6篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有279条查询结果,搜索用时 15 毫秒
101.
The ability of a genus of cephalosporium-like fungus isolated from soil, Acremonium strictum PTCC 5282, for hydrocortisone biotransformation has been investigated. This potential had not been previously examined. The fermentation yielded 11beta,17beta-dihydroxyandrost-4-en-3-one, 11beta,17alpha,20beta,21-tetrahydroxypregn-4-en-3-one and 21-acetoxy-11beta,17alpha,20-trihydroxypregn-4-en-3-one. Each microbial metabolite was purified and characterized using spectroscopic methods. 相似文献
102.
103.
104.
Particulate matter and bacteria characteristics of the Middle East Dust (MED) storms over Ahvaz,Iran
Gholamreza Goudarzi Mohammad Shirmardi Fatemeh Khodarahmi Abdolrazagh Hashemi-Shahraki Nadali Alavi Kambiz Ahmadi Ankali Ali Akbar Babaei Zahra Soleimani Mohammad Bagherian Marzouni 《Aerobiologia》2014,30(4):345-356
The Middle East Dust storms have greatly affected the south and west parts of Iran during the last decade. The main purpose of this study was to examine and compare culturable airborne bacteria concentration in particulate matter (PM) during normal, semi-dust, and dust event days in different places and seasons in Ahvaz from November 2011 to May 2012. Sampling was performed every 6 days and on dust event days at different sampling stations. The overall mean concentrations of PM10, PM2.5, and PM1 for the entire study period were 598.92, 114.8, and 34.5 μg/m3, respectively. The PM concentrations during the dust event days were much higher than normal and semi-dust event days. The highest mean PM concentrations were observed in March 2011. The low PM2.5/PM10 ratios indicate that these PM are mostly originating from natural sources such as dust storms. The overall mean concentration of total bacteria during the study period was 620.6 CFU/m3. The greatest bacterial concentrations were observed during dust event days and at areas with high traffic and more human activities compared with normal days and greener areas. The percentage of gram-positive bacteria was significantly higher than that during the study period (89 vs 11 %). During this study, 26 genera of culturable bacteria were identified from all the sampling stations. The most dominant genera in all sampling stations were Streptomyces, Bacillus, Kocuria, Corynebacterium, and Paenibacillus. The results also showed that there were positive correlations between PM and bacterial concentrations during the study period (p < 0.05). 相似文献
105.
106.
107.
Jennifer M. Fitchett Stefan W. Grab Dave I. Thompson Gholamreza Roshan 《International journal of biometeorology》2014,58(8):1811-1815
Flowering dates and the timing of late season frost are both driven by local ambient temperatures. However, under climatic warming observed over the past century, it remains uncertain how such impacts affect frost risk associated with plant phenophase shifts. Any increase in frost frequency or severity has the potential to damage flowers and their resultant yields and, in more extreme cases, the survival of the plant. An accurate assessment of the relationship between the timing of last frost events and phenological shifts associated with warmer climate is thus imperative. We investigate spring advances in citrus flowering dates (orange, tangerine, sweet lemon, sour lemon and sour orange) for Kerman and Shiraz, Iran from 1960 to 2010. These cities have experienced increases in both T max and T min, advances in peak flowering dates and changes in last frost dates over the study period. Based on daily instrumental climate records, the last frost dates for each year are compared with the peak flowering dates. For both cities, the rate of last frost advance lags behind the phenological advance, thus increasing frost risk. Increased frost risk will likely have considerable direct impacts on crop yields and on the associated capacity to adapt, given future climatic uncertainty. 相似文献
108.
109.
Gholamreza Goudarzi Morteza Sattari Mehryar Habibi Roudkenar Mehran Montajabi-Niyat Ahmad Zavaran-Hosseini Kamran Mosavi-Hosseini 《Biotechnology letters》2009,31(9):1353-1360
Pseudomonas aeruginosa as an opportunistic pathogen causes lethal infections in immunocompromised individuals. This bacterium possesses a polar
flagellum made up of flagellin subunits. Flagella have important roles in motility, chemotaxis, and establishment of P. aeruginosa in acute phase of infections. Isolation, cloning, and expression of flagellin were aimed at in this study. Flagellin gene
(fliC) of P. aeruginosa strain 8821M was isolated by PCR and cloned into a pET expression vector. The recombinant flagellin (46 kDa) was overexpressed
as inclusion bodies (IBs). IBs were solubilized in guanidine hydrochloride (GuHCl) followed by affinity-purification and renatured
using Ni2+-Sepharose resin. Recombinant flagellins reacted with the serum from a rabbit previously immunized with native flagellin.
In addition, polyclonal antiserum raised against the recombinant flagellin was shown to significantly inhibit the cell motility
of P. aeruginosa strain 8821M in vitro. 相似文献
110.