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   803篇
  免费   36篇
  2022年   1篇
  2021年   10篇
  2020年   4篇
  2019年   7篇
  2018年   10篇
  2017年   7篇
  2016年   10篇
  2015年   18篇
  2014年   23篇
  2013年   34篇
  2012年   41篇
  2011年   47篇
  2010年   30篇
  2009年   26篇
  2008年   69篇
  2007年   69篇
  2006年   87篇
  2005年   71篇
  2004年   59篇
  2003年   61篇
  2002年   58篇
  2001年   4篇
  2000年   4篇
  1999年   8篇
  1998年   6篇
  1997年   8篇
  1996年   5篇
  1995年   4篇
  1994年   7篇
  1993年   2篇
  1992年   1篇
  1991年   6篇
  1990年   4篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1985年   3篇
  1984年   1篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1979年   2篇
  1978年   3篇
  1975年   5篇
  1974年   4篇
  1973年   2篇
  1972年   2篇
排序方式: 共有839条查询结果,搜索用时 31 毫秒
781.

Objectives

Radiotherapy in patients with sinonasal mucosal melanoma (SNMM) was given as alternative treatment to surgery in cases with advanced, inoperable tumors or those not eligible for surgery. We presented the outcomes for patients with SNMM treated with radiotherapy alone.

Material and methods

The retrospective review of 6 consecutive SNMM (nasal cavity – 4 pts. and paranasal sinus – 2 pts.) patients (3 males and 3 females at mean age 64 years) treated between 2008 and 2016 was presented. The stage of disease was: T3 (1 pt.), T4a (3 pts.), T4b (2 pts.); with N0 and M0 in all patients. All patients underwent definitive primary photon radiotherapy (IMRT) alone; dose 66–72?Gy was delivered in 22–24 fractions given in 5 fractions (3?Gy) a week.

Results

The complete remission was observed in all our patients but only one patient survived 5 years without disease. Five patients died due to multiple distant metastases; two of those patients developed associated local recurrence 7–8 months after radiotherapy.

Conclusion

SNMM has a poor prognosis due to its high metastatic potential. Based on our numerically small report and data from literature we concluded that primary radiotherapy alone assured complete remission and even 5-year disease-free survival in only a few individual patients.  相似文献   
782.
Disperis tomaszii (Orchidaceae, Orchidoideae) from Cameroon is described and illustrated in this study. The new species is morphologically similar to Disperis nitida and Disperis thomensis. Phylogenetic analyses of selected DNA regions (ITS, matK) indicate a possible relationship between the new species and Disperis anthoceros and Disperis dicerochila. The taxonomic affinity between D. tomaszii and the aforementioned species is discussed.  相似文献   
783.
The aims of the study were to determine manganese (Mn), iron (Fe) and strontium (Sr) concentrations in fox bone samples from north-western Poland and to examine the relationships between the bone Mn, Fe and Sr concentrations and the sex and age of the foxes. In the studied samples of fox cartilage, cartilage with adjacent compact bone, compact bone and spongy bone, the concentrations of the analysed metals had the following descending order: Fe > Sr > Mn. The only exception was in compact bone, in which the concentrations were arranged in the order Sr > Fe > Mn. Manganese concentrations were significantly higher in cartilage, compact bone and cartilage with compact bone than in spongy bone. Iron concentrations were higher in cartilage and spongy bone compared with compact bone. Strontium concentrations were greater in compact bone than in cartilage and spongy bone. The manganese, iron and strontium concentrations in the same type of bone material in many cases correlated with each other, with the strongest correlation (r?>?0.70) between Mn and Fe in almost all types of samples. In addition, concentrations of the same metals in different bone materials were closely correlated for Mn and Fe in cartilage and cartilage with adjacent compact bone, and for Sr in compact bone and cartilage with compact bone. In the fox from NW Poland, there were no statistically significant differences in Mn, Fe and Sr in any of the types of bone material between the sexes and immature and adult foxes.  相似文献   
784.
Some sheep breeds are naturally prolific, and they are very informative for the studies of reproductive genetics and physiology. Major genes increasing litter size (LS) and ovulation rate (OR) were suspected in the French Grivette and the Polish Olkuska sheep populations, respectively. To identify genetic variants responsible for the highly prolific phenotype in these two breeds, genome-wide association studies (GWAS) followed by complementary genetic and functional analyses were performed. Highly prolific ewes (cases) and normal prolific ewes (controls) from each breed were genotyped using the Illumina OvineSNP50 Genotyping Beadchip. In both populations, an X chromosome region, close to the BMP15 gene, harbored clusters of markers with suggestive evidence of association at significance levels between 1E−05 and 1E−07. The BMP15 candidate gene was then sequenced, and two novel non-conservative mutations called FecXGr and FecXO were identified in the Grivette and Olkuska breeds, respectively. The two mutations were associated with the highly prolific phenotype (pFecXGr = 5.98E−06 and pFecXO = 2.55E−08). Homozygous ewes for the mutated allele showed a significantly increased prolificacy (FecXGr/FecXGr, LS = 2.50±0.65 versus FecX+/FecXGr, LS = 1.93±0.42, p<1E−03 and FecXO/FecXO, OR = 3.28±0.85 versus FecX+/FecXO, OR = 2.02±0.47, p<1E−03). Both mutations are located in very well conserved motifs of the protein and altered the BMP15 signaling activity in vitro using a BMP-responsive luciferase test in COV434 granulosa cells. Thus, we have identified two novel mutations in the BMP15 gene associated with increased LS and OR. Notably, homozygous FecXGr/FecXGr Grivette and homozygous FecXO/FecXO Olkuska ewes are hyperprolific in striking contrast with the sterility exhibited by all other known homozygous BMP15 mutations. Our results bring new insights into the key role played by the BMP15 protein in ovarian function and could contribute to a better understanding of the pathogenesis of women′s fertility disorders.  相似文献   
785.
IntroductionThe objective of this study was to analyze the motor unit potentials (MUPs) with satellite components i.e., delayed by at least 2 ms baseline from the main component, in the dystrophinopathies.MethodsThe parameters of the MUPs recorded from the biceps brachii muscle in the Duchenne and Becker Muscle Dystrophy (DMD, BMD) were analyzed. The origin of the MUP satellite components was studied using a computer simulation.ResultsAs compared with normal potentials, both the main and the satellite MUP components are smaller in size, while the main components are more irregular. The computer simulation allows the range of muscle fiber diameters to be determined, and suggests that the variability characterizing diameters within the motor unit is responsible for generating the delayed, satellite components, via the linear relationship between the fiber diameter and the conduction velocity of the action potential.DiscussionThe enhanced understanding of the origin of the MUP satellite components augments the knowledge about the relationship between muscle morphology and bioelectrical activity. The indirect evaluation of the range of muscle fiber diameters by means of a computer simulation may provide a new quantitative morphological data available from the EMG.  相似文献   
786.
787.
The identification of virulence genes in plant pathogenic fungi is important for understanding the infection process, host range and for developing control strategies. The analysis of already verified virulence genes in phytopathogenic fungi in the context of integrated functional networks can give clues about the underlying mechanisms and pathways directly or indirectly linked to fungal pathogenicity and can suggest new candidates for further experimental investigation, using a ‘guilt by association’ approach. Here we study 133 genes in the globally important Ascomycete fungus Fusarium graminearum that have been experimentally tested for their involvement in virulence. An integrated network that combines information from gene co-expression, predicted protein-protein interactions and sequence similarity was employed and, using 100 genes known to be required for virulence, we found a total of 215 new proteins potentially associated with virulence of which 29 are annotated as hypothetical proteins. The majority of these potential virulence genes are located in chromosomal regions known to have a low recombination frequency. We have also explored the taxonomic diversity of these candidates and found 25 sequences, which are likely to be fungal specific. We discuss the biological relevance of a few of the potentially novel virulence associated genes in detail. The analysis of already verified virulence genes in phytopathogenic fungi in the context of integrated functional networks can give clues about the underlying mechanisms and pathways directly or indirectly linked to fungal pathogenicity and can suggest new candidates for further experimental investigation, using a ‘guilt by association’ approach.  相似文献   
788.
INTRODUCTION: The study was undertaken to determine blood serum concentrations of selected steroid hormones (estradiol--E(2), testosterone--T, dehydroepiandrosterone sulfate--DHEA-S) and luteinizing hormone (LH) in professional footballers subjected to whole body cryotherapy. MATERIAL AND METHODS: Twenty-two clinically healthy males, mean age 26.7 years, were studied. The subjects underwent ten sessions of whole body cryotherapy in Wroclaw-type chamber, with kinesitherapy following each session. Blood samples were collected before and two days after the treatment and the results were analyzed statistically. RESULTS: After the treatment there was a significant decrease in the concentrations of T (6.01 vs. 4.80 ng/mL, p < 0.01) and E(2) (102.3 vs. 47.5 pg/mL, p < 0.00001), but no DHEA-S and LH. The T/E(2) ratio showed a significant increase form 72.2 to 136.5 (p < 0.01). CONCLUSIONS: Whole body cryotherapy leads to a significant decrease in serum T and E(2), with no effect on LH and DHEAS levels. As a results of cryotherapy, the T/E(2) ratio was significant increased. The changes observed are probably due to cryotherapy-induced alternation in the blood supply to the skin and subcutaneous tissue, as well as to modulation of the activity of aromatase which is responsible for conversion of testosterone and androstenedione to estrogens.  相似文献   
789.
INTRODUCTION: The aim of the present study was to examine the response of plasma orexin and ghrelin to the oral glucose tolerance test (OGTT) in obese women without additional disease. MATERIAL AND METHODS: The study group comprised 15 obese women aged 30.4+/-9.7 years of mean BMI 34.7+/-3.8 kg/m(2). The measurements were performed after an overnight fast and 30, 60 and 120 minutes after the oral administration of 75 grams of glucose. Serum concentrations of ghrelin and orexin A were measured by an enzyme-linked immunosorbent assay (ELISA) kit. Serum concentrations of insulin were measured by radioimmunoassay (RIA). Plasma glucose was determined by an enzymatic procedure. Body composition was determined by impedance analysis using Bodystat. RESULTS: We observed no significant differences between serum concentrations of ghrelin and orexin during OGTT. No correlations were found between serum ghrelin and orexin concentrations and serum insulin and glucose concentrations in any of the measurements. CONCLUSION: Oral glucose administration did not change serum concentrations of ghrelin and orexin A in obese women without additional disease.  相似文献   
790.
During establishment of spermatogenesis at the prepubertal age, an early germ cells apoptotic wave occurs likely aimed to remove abnormal germ cells and to maintain a proper cell number ratio between maturating germ cells and Sertoli cells. Here we assessed Sertoli and germ cell apoptosis in relation to morphological parameters of Sertoli cell maturation in neonatal rats under the influence of testosterone, estradiol and FSH given alone or in combinations. From postnatal day (PND) 5th to 15th male rats were daily injected with: 1) 2.5 mg of testosterone propionate (TP), or 2) 12.5 microg of 17beta-estradiol benzoate (EB), or 3) TP+EB, or 4) 7.5 IU of human purified FSH (hFSH), or 5) hFSH+EB or solvents (control-C). Autopsy was performed on PND 16th. Sertoli cell nuclei area and incidence of seminiferous tubule lumen formation (LF) were taken as markers of Sertoli cell maturation. Sertoli and germ cell apoptosis was assessed using TUNEL method. In comparison with C, the area of Sertoli cell nuclei was significantly reduced after EB (25.7+/-2.0 vs. 30.9+/-1.6 microm2 for C, p<0.001) and increased after hFSH+EB (33.1+/-2.3 microm2, p<0.05). Incidence of LF was completely arrested by steroid hormone treatments given separately, significantly inhibited after TP+EB (median: 0.0%, vs. 2.0% for C p<0.05) and significantly enhanced after hFSH+EB (median: 51.0%, p<0.001). hFSH alone did not influence LF. Incidence of TUNEL positive Sertoli cells significantly increased after EB (median: 2.9% vs. 0.5% for C, p<0.05) or TP+EB (median: 2.2%, p<0.01) and was not affected by other treatments. Incidence of TUNEL positive germ cells increased significantly after EB alone (median: 4.4% vs. 2.5%, for C, p<0.01 ) and was significantly decreased by hFSH+EB (median: 0.5%, p<0.01). CONCLUSIONS: 1) Administration of testosterone or estradiol to immature rats inhibits Sertoli cell maturation. 2) Estradiol stimulates Sertoli and germ cell apoptosis while testosterone has no effect. 3) Testosterone eliminates estradiol--induced germ cell apoptosis when both hormones act in concert. 4) FSH in concert with estradiol, but neither one of the hormone alone, accelerate Sertoli cell differentiation and effectively inhibit germ cell apoptosis. 5) During seminiferous tubule maturation testosterone and the synergistic action of FSH with estradiol support germ cell survival while estradiol alone has an inhibitory, pro-apoptotic effect.  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