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   245篇
  免费   16篇
  国内免费   1篇
  2024年   1篇
  2023年   2篇
  2022年   3篇
  2021年   11篇
  2020年   6篇
  2019年   3篇
  2018年   7篇
  2017年   8篇
  2016年   11篇
  2015年   14篇
  2014年   14篇
  2013年   17篇
  2012年   19篇
  2011年   17篇
  2010年   15篇
  2009年   11篇
  2008年   10篇
  2007年   16篇
  2006年   8篇
  2005年   9篇
  2004年   8篇
  2003年   19篇
  2002年   8篇
  2001年   3篇
  2000年   9篇
  1999年   5篇
  1998年   1篇
  1996年   1篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1985年   1篇
  1982年   1篇
  1969年   1篇
排序方式: 共有262条查询结果,搜索用时 31 毫秒
31.
P-glycoprotein (Pgp) is encoded by the multidrug resistance gene (MDR1) in humans and is the product of MDR1. It is expressed in various tissues and is related to drug distribution in intestinal erythrocytes, capillary endotel of brain, proximal tubules cells of kidneys and liver canalicular cells. Expression of Pgp is affected by Pgp polymorphism, and exon 26 C3435T polymorphism is the most common one. It has been thought that expression of Pgp is high in C-allele subjects and this situation is responsible for the resistance against some drugs and substances. Pgp may have a role in the distribution of thyroid hormones, drugs used for hypo- and hyperthyroidism and the resistance occurred. For this purpose possible relationship between T and C alleles and frequency of Pgp polymorphism as well as thyroid hormone distribution in patients with hypo- and hyperthyroidism was investigated. Thirty five hyperthyroidism patients diagnosed as Graves’ disease, 78 hypothyroidism patients diagnosed as Hashimoto’s thyroiditis and 100 healthy volunteers were included in the study. According to the results obtained no statistically significant difference was found in Pgp C3435T polymorphism between hypo- and hyperthyroidism patients. In addition, the serum free T3 levels of hyperthyroidism patients with C alleles was higher than those of subjects with T alleles. No statistically significant difference was seen in the CC, CT and TT genotype frequencies between the patients and control groups. In conclusion, it seems that Pgp polymorphism is not a predictor factor for the occurrence of hypo- and hyperthyroidism. There is a significant relationship between Pgp and the elevated serum free T3 levels of hyperthyroidism patients, and further research will help understand this situation.  相似文献   
32.
Antibody microarray analysis of directly labelled complex proteomes   总被引:4,自引:0,他引:4  
In recent years, the antibody microarray technology has made significant progress, going from proof-of-concept designs to established high-performing technology platforms capable of targeting non-fractionated complex proteomes. In these cross-disciplinary efforts, a particular focus has lately been placed on two key technological issues: the sample and data handling. To this end, robust protocols have been designed for direct labelling of whole proteomes compatible with a sensitive fluorescent-based sensing. Tagging of the proteins with biotin in a single-colour approach has, in many cases, proven to be the preferred approach. Furthermore, based on modified approaches, adopted from the DNA microarray field, the first bioinformatic standards for performing the antibody microarray data analysis have emerged, though general standard operating procedure(s) remains to be implemented.  相似文献   
33.
Species of Chaetoceros with less than four setae per cell are not common. In this study, five different taxa presenting this characteristic were found in the Sontecomapan lagoon, Mexico, a small tropical coastal lagoon on the Gulf of Mexico:Chaetoceros minimus, C. subtilis var. abnormis f. abnormis, C. subtilis var. abnormis f. simplex, C. throndsenii var. throndsenia, and C. thondsenii var. trisetosa. Using an electron microscope to make observations of C. subtilis var. abnormis f. simplex made evident the absence of rimoportulae suggesting a close relationship to C. minimus. According to our observations, we believe that the reduction in the number of setae in Chaetoceros is related to solitary forms. The five species studied here are associated with quiet brackish-water enclosed environments and can be considered worldwide-distributed organisms.  相似文献   
34.
Specimens of Raja clavata were monthly collected at the coast of Havaalan? (Trabzon/Turkey) from January 2009 to December 2009 at depths between 20 and 40?m. A total of 230 individuals of thornback ray (131 females and 99 males) were collected by bottom trawls during research cruises. Using logistic regression, it was determined that TL at 50% maturity of males was 718?mm TL and of females 746?mm TL. The ovarian fecundity ranged from 27 to 60 yellow follicles in both ovaries. Females carrying egg cases were found in July and October. Variations in the gonadosomatic and hepatosomatic indices indicated a continuous reproductive cycle during the year.  相似文献   
35.
Biosynthesis of silver nanoparticles (AgNPs) using microorganisms is an important application of nanobiotechnology and green chemistry because of interest by pharmaceutical and food manufacturers. In this study, biosynthesis of AgNPs by a novel Bacillus strain isolated from a soil sample from Sakarya district in Turkey was investigated. Biosynthesis was performed using cell-free supernatant of the bacterium following 24?h growth. Effects of varying AgNO3 concentration (1–10?mM), pH (5–10), and temperature (30–40°C) on the synthesis of AgNPs were determined. Formation of AgNPs was monitored by UV–VIS spectroscopy. Field emission scanning electron microscopy was used to compare morphologies among the various culture conditions. The peaks created by surface plasmon resonance (SPR) of metals were obtained only at 4 and 6?mM AgNO3 concentrations and the maximum concentration for the biosynthesis was observed at 6?mM. The highest yield was achieved at pH 10 and larger nanoparticles were obtained at this pH. The optimum temperatures for biosynthesis were 33 and 37°C. Fourier transform infrared spectroscopy analysis and transmission electron microcopy images confirmed that the proteins served as capping. Energy-dispersive spectroscopy analysis validated the formation of AgNPs. AgNPs exhibited antibacterial activity toward Gram-positive and Gram-negative pathogens.  相似文献   
36.
A new species in the family Pyralidae is described: Megasis kocaki sp. n., of which the adult, head and the male genitalia are illustrated. The new species is compared with the closely allied Megasis hyrcanella Ragonot, 1893.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:0136DD7F-0E91-4114-9B3B-A42E6114A985  相似文献   

37.
We assessed the size of the population of the African Softshell Turtle, Trionyx triunguis, in Dalaman (Mu?la, Turkey), which is considered to be the largest population of the species in the Mediterranean, by using the Jolly-Seber mark-recapture method. A total of 415 individuals were caught during the summer months of 2009 to 2011, of which 148 were recaptures. From 267 marked individuals, 148 (55%) were male, 69 (26%) were female and 50 (19%) were juveniles and subadults of indeterminate sex. The male:female ratio was calculated to be 2.14:1. By using Model A' of the Jolly-Seber mark-recapture method, which includes deaths but no immigration, the mean population size in Kükürt and Küçükdalyan (Karg?n) lakes, together with Tersakan and Ta?l?çay creeks, were estimated to be 396±36. Based on this estimation, the population density was calculated to be 14 turtles/ha. Approximately 67.4% of the estimated population was marked. The mean capture probability (p) and mean survival ratio (Φ) were 0.094±0.009 and 0.957±0.076, respectively. Our results showed that the species’ population size is larger than previously estimated based on visual counts. The status “Vulnerable” C2a of the IUCN Red Data Book categories seems therefore more appropriate for the Mediterranean subpopulation of Trionyx triunguis than “Endangered” C2a.  相似文献   
38.
The aim of this study was to determine the relationship between serum and cerebrospinal fluid (CSF) magnesium (Mg+2) levels, Glasgow Coma Scores (GCS), and 7-day mortality in acute stroke patients. Patients with acute ischemic or hemorrhagic stroke arriving within the first 3 h of symptoms were included in the study. The control group consisted of healthy volunteers. GCS was determined, and blood and CSF samples were taken in order to establish serum and CSF glucose, Mg+2, sodium, potassium, calcium, and chlorine levels. Mortality was recorded at 7 days after admission. CSF Mg+2 in the ischemic infarct group was significantly lower than in the control group (p = 0.006). CSF Mg+2 in the ischemic infarct patients with a GCS ≤ 8 were significantly lower (p = 0.002) than controls and in ischemic infarct patients with a GCS ≥9. In the ischemic stroke patients, CSF Mg+2 and GCS were significantly correlated (r = 55, p = 0.031). CSF Mg+2 levels in ischemic stroke patients who died within 7 days were significantly lower than controls, ischemic stroke patients who survived, and hemorrhagic stroke patients who died (p = 0.002, p = 0.042, and p = 0.005, respectively). Low CSF Mg+2 levels in patients with acute ischemic stoke at admission predicted a higher 1-week mortality.  相似文献   
39.
Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45, and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer. Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded the loss of nisin in the late phase of the fermentation.  相似文献   
40.
Salmonella Typhimurium contains 13 operons coding for fimbriae with unique binding specificities to host epithelial surfaces. stj operon is only detected in S. Typhimurium genome suggesting that Stj fimbria may effect serovarspecific virulence characteristics. In this study, the role of stj fimbrial operon in the long-term persistence of S. Typhimurium was identified by competitive infection experiment in genetically resistant mouse (CBA) model system. Knock-out mutation of stjA (major subunit of the Stj fimbria) gene reduced recovery of S. Typhimurium from fecal samples and its colonization to spleen, cecum and mesenteric lymph nodes over a 34-day time period (p < 0.05). This data indicate that stj fimbrial operon has a role in long-term intestinal persistence of S. Typhimurium in CBA mice.  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