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   394篇
  免费   21篇
  415篇
  2022年   11篇
  2021年   9篇
  2020年   9篇
  2019年   8篇
  2018年   4篇
  2017年   11篇
  2016年   13篇
  2015年   18篇
  2014年   18篇
  2013年   22篇
  2012年   25篇
  2011年   25篇
  2010年   21篇
  2009年   12篇
  2008年   24篇
  2007年   26篇
  2006年   18篇
  2005年   28篇
  2004年   23篇
  2003年   26篇
  2002年   12篇
  2001年   13篇
  2000年   9篇
  1999年   5篇
  1998年   6篇
  1997年   2篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1985年   1篇
  1980年   3篇
  1979年   1篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1967年   1篇
排序方式: 共有415条查询结果,搜索用时 15 毫秒
11.
12.
Biological Trace Element Research - This study was carried out to determine vit. E, Se, vit. A, malondialdehyde (MDA), 8-hydroxy-2-deoxyguanosine (8-OHdG), and ubiquinone-10 (CoQ10) levels and...  相似文献   
13.
This study was undertaken to test the effect of irradiation on the histopathology of the hypothalamus and cerebral cortex. In addition, the probable effects of radiotherapy on the activities of antioxidant enzymes and levels of nitric oxide (NO) in the plasma were investigated as well. The effects of melatonin treatment on radiotherapy-based central nervous system (CNS) damage were also studied. For this purpose, the rats were randomized into four groups. The first group was the control group (sham-exposed group), the second group received only melatonin, the third group was irradiated and the fourth group received both melatonin and irradiation. Plasma samples of rats were collected for measuring the activities of superoxide dismutase (SOD), catalase (CAT) and the levels of NO. 24 h after the interventions, tissue samples were obtained from the hypothalamus and the cerebral cortex for the light microscopic investigations. These tissues were mostly affected by radiation. The results indicated that the application of radiation significantly enhanced the levels of plasma SOD and NO. On the other hand, melatonin pretreatment prevented the decrease in plasma CAT activity induced by irradiation. It was found that the application of melatonin could significantly prevent the irradiation-induced damages. Light microscopic results revealed that the damage of the CNS by radiation was prevented by the application of melatonin.  相似文献   
14.
Gastric cancer is the fourth most prevalent malignancy worldwide and remains the second most common cause of cancer-related death globally. Understanding the molecular structure of gastric carcinogenesis might identify new diagnostic and therapeutic strategies for this disease. Thus, early detection of gastric cancer is a key measure to reduce the mortality and improve the prognosis of gastric cancer. There have recently been several reports that microRNAs (miRNAs) circulate in highly stable, cell-free forms in blood. Because serum and plasma miRNAs are relatively easy to access, circulating miRNAs also have great potential to serve as non-invasive biomarkers. Although a number of miRNAs associated with gastric cancer have been identified, the underlying mechanism of these miRNAs in tumorigenesis and tumor progression remains to be investigated. The purpose of this study is to identify the potential of serum miRNAs as biomarkers for early detection of gastric cancer patients. RNA was isolated using the High Pure miRNA Isolation Kit (Roche) following the manufacturer’s protocol. cDNA and preamplification protocols were obtained from the isolated plasma miRNAs. The BioMark? 96.96 Dynamic Array (Fluidigm Corporation) for real-time qPCR was used to simultaneously quantite the expression of 740 miRNAs. All statistical analyses were performed using the Biogazelle’s qbase PLUS 2.0 software. In this study, among 740 miRNAs that we analyzed only miR-195-5p was significantly (p < 0.05, fold changes = 13, 3) down-regulated in gastric cancer patients compared with control. We demonstrated that miR-195-5p is a novel tumor suppressor miRNA and may contribute to gastric carcinogenesis. The miRNA expression profile described in this study should contribute to future studies on the role of miRNAs in gastric cancer.  相似文献   
15.
In this speculative essay, I examine two evolutionary developments underlying the enormous success of the human brain: its capacity to acquire knowledge and its variability across individuals. A feature of an efficient knowledge-acquiring system is, I believe, its capacity to abstract and to formulate ideals. Both attributes carry with them a clash between experience of the particular and what the brain has developed from experience of the many. Both therefore can lead to much disappointment in our daily lives. This disappointment is heightened by the fact that both abstraction and ideals are subject to variability in time within an individual and between individuals. Variability, which is a cherished source for evolutionary selection, can also be an isolating and individualizing feature in society. Thus the very features of the human brain which underlie our enormous evolutionary success can also be a major source of our misery.  相似文献   
16.
Bifidocin B produced by Bifidobacterium bifidum NCFB 1454 was purified to homogeneity by a rapid and simple three step purification procedure which included freeze drying, Micro-Cel adsorption/desorption and cation exchange chromatography. The purification resulted in 18% recovery and an approximately 1900-fold increase in the specific activity and purity of bifidocin B. Treatment with bifidocin B caused sensitive cells to lose high amounts of intracellular K+ ions and u.v.-absorbing materials, and to become more permeable to ONPG. Bifidocin B adsorbed to the Gram-positive bacteria but not the Gram-negative bacteria tested. Its adsorption was pH-dependent but not time-dependent. For sensitive cells, the adsorption and lethal action of bifidocin B was very rapid. In 5 min, 95% of bifidocin B adsorbed onto sensitive cells. Several salts inhibited the binding of bifidocin B, which could be overcome by increasing the amount of bifidocin B added. Pre-treatment of sensitive cells and cell walls with detergents, organic solvents or enzymes did not cause a reduction in subsequent cellular binding of bifidocin B, but cell wall preparations treated with methanol:chloroform and hot 20% (w/v) TCA lost the ability to adsorb bifidocin B. Also, the addition of purified heterologous lipoteichoic acid to sensitive cells completely blocked the adsorption of bifidocin B. The amino acid sequence indicated that the bacteriocin contained 36 residues. N-terminal amino acid sequence analysis yielded a sequence of KYYGNGVTCGLHDCRVDRGKATCGIINNGGMWGDIG. Curing experiments with 20 micrograms ml-1 acriflavine yielded cell derivatives that no longer produced bifidocin B but retained immunity to bifidocin B. Production of bifidocin B, but not immunity to bifidocin B, was associated with a plasmid of about 8 kb in this strain.  相似文献   
17.
18.
Surgical reconstruction of the penis is challenging because of the many cosmetic and functional (e.g., sexual intercourse and voiding) requirements that must be addressed. Since the free sensate osteocutaneous fibula flap was first described for total penile reconstruction in 1993 it has been widely accepted, with its advantages and minimal shortcomings. In this article, the authors present the longest follow-up of biologically male patients with free fibular phalloplasties. Since 1994, 18 biologically male patients with total penile losses for various reasons were treated with free sensate osteocutaneous fibula flaps. All patients were included in the study. The ages of the patients ranged between 20 and 26 years (mean, 22.2 years). The average follow-up period was 5.4 years (range, 1 to 9 years). Patient satisfaction was evaluated by a questionnaire regarding both quality of orgasm and daily activities. Conventional radiographic imaging, magnetic resonance imaging, and bone mineral densitometry were performed to evaluate the fate of the bony component of the flap. Also, sensibility was evaluated by bulbocavernous reflex and penile somatosensory evoked potentials testing in nine patients. Six patients married, and five of them had six children. Most patients and their partners reported pleasurable sexual intercourse and orgasm. Conventional radiographs of the fibular bone in neophalluses showed robust, calcified bone structure without any evidence of bone resorption or fracture. The magnetic resonance images showed the cortical substance and spongiosum of the bone marrow, which are characteristic signs of bone viability. After intravenous injection of gadolinium, the neophallus bone showed uptake of contrast medium. Viability of neophallus bone was shown even at 9-year follow-up (the longest follow-up in the literature). Dual energy x-ray absorptiometry measurements of the penile bone grafts showed that fibular components in the penis had bone mineral density values that were close to but lower than those of intact fibula in the same subjects. These results were considered as evidence of viability of bone grafts. Neural integrity was found between the nerves of the neophallus and the residual penile bodies by both bulbocavernous reflex and penile somatosensory evoked potentials tests. In conclusion, free sensate fibula flap phalloplasty provides the cosmetic and functional requirements that an ideal penis should have. All results put an end to the discussion that the fibular component of the neophallus could resorb. Constitution of neural integrity is important in terms of pleasurable sexual intercourse. The authors believe the free sensate osteocutaneous fibula flap should be considered as the standard in penile reconstruction.  相似文献   
19.
Listeria monocytogenes contamination of ready-to-eat foods has been implicated in numerous outbreaks of food-borne listeriosis. However, the health hazards posed by L. monocytogenes detected in foods may vary, and speculations exist that strains actually implicated in illness may constitute only a fraction of those that contaminate foods. In this study, examination of 34 serogroup 4 (putative or confirmed serotype 4b) isolates of L. monocytogenes obtained from various foods and food-processing environments, without known implication in illness, revealed that many of these strains had methylation of cytosines at GATC sites in the genome, rendering their DNA resistant to digestion by the restriction endonuclease Sau3AI. These strains also harbored a gene cassette with putative restriction-modification system genes as well as other, genomically unlinked genetic markers characteristic of the major epidemic-associated lineage of L. monocytogenes (epidemic clone I), implicated in numerous outbreaks in Europe and North America. This may reflect a relatively high fitness of strains with these genetic markers in foods and food-related environments relative to other serotype 4b strains and may partially account for the repeated involvement of such strains in human food-borne listeriosis.  相似文献   
20.
Combining law and the brain as a matter for study requires the integration not just of two apparently remote fields of study but also of two profoundly different orientations towards research and study. We believe that, in spite of the difficulties, such a combination, perhaps even emerging in a new specialized discipline in the future, will not only enrich both fields but is the ineluctable consequence of the current assault on the secrets of the brain. The effort to bring the fields together is therefore a worthy task, and this issue is the first systematic effort to test this expectation.  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