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   55篇
  免费   1篇
教育   37篇
科学研究   12篇
各国文化   2篇
文化理论   1篇
信息传播   4篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2020年   5篇
  2019年   5篇
  2018年   1篇
  2017年   3篇
  2016年   2篇
  2015年   1篇
  2014年   1篇
  2013年   8篇
  2012年   2篇
  2011年   3篇
  2010年   3篇
  2009年   1篇
  2008年   2篇
  2007年   2篇
  2006年   3篇
  2004年   1篇
  2002年   1篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1988年   1篇
  1983年   1篇
  1982年   1篇
  1965年   1篇
  1963年   1篇
排序方式: 共有56条查询结果,搜索用时 15 毫秒
21.
22.
Worldwide there has been a significant increase in the incidence of oropharyngeal squamous cell carcinoma (OPSCC) etiologically attributed to oncogenic human papillomavirus (HPV). Reliable and accurate identification and detection tools are important as the incidence of HPV-related cancer is on the rise. Several HPV detection methods for OPSCC have been developed and each has its own advantages and disadvantages in regard to sensitivity, specificity, and technical difficulty. This review summarizes our current knowledge of molecular methods for detecting HPV in OPSCC, including HPV DNA/RNA polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), p16 immunohistochemistry (IHC), and DNA/RNA in situ hybridization (ISH) assays. This summary may facilitate the selection of a suitable method for detecting HPV infection, and therefore may help in the early diagnosis of HPV-related carcinoma to reduce its mortality, incidence, and morbidity.  相似文献   
23.
The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.  相似文献   
24.
Two reef margin species of tropical sea urchins, Echinometra sp. C (Ec) and Echinometra oblonga (Eo), occur sympatrically on Okinawa intertidal reefs in southern Japan. Hybridization between these species was examined through a series of cross-fertilization experiments. At limited sperm concentrations, where conspecific crosses reached near 100% fertilization, both heterospecific crosses showed high fertilization rates (81%–85%). The compatibility of the gametes demonstrated that if gamete recognition molecules are involved in fertilization of these species, they are not strongly species-specific. We found that conspecific crosses reached peak fertilization levels much faster than did heterospecific crosses, indicating the presence of a prezygotic barrier to hybridization in the gametes. Larval survival, metamorphosis, and juvenile and adult survival of hybrid groups were nearly identical to those of their parent species. Hybrids from crosses in both directions developed normally through larval stages to sexually mature adults, indicating that neither gametic incompatibility nor hybrid inviability appeared to maintain reproductive isolation between these species. In adults, Ec×Ec crosses gave the highest live weight, followed by Eo (ova)×Ec (sperm), Ec (ova)×Eo (sperm), and Eo×Eo. Other growth performance measures (viz., test size, Aristotle’s lantern length, and gonad index) of hybrid groups and their parental siblings showed the same trends. The phenotypic color patterns of the hybrids were closer to the maternal coloration, whereas spine length, tube-foot and gonad spicule characteristics, pedicellaria valve length, and gamete sizes showed intermediate features. Adult F1 hybrids were completely fertile and displayed high fertilization success in F1 backcrosses, eliminating the likelihood that hybrid sterility is a postzygotic mechanism of reproductive isolation. Conversely, intensive surveys failed to find hybrid individuals in the field, suggesting the lack or rarity of natural hybridization. This strongly suggests that reproductive isolation is achieved by prezygotic isolating mechanism(s). Of these mechanisms, habitat segregation, gamete competition, differences in spawning times, gametic incompatibility or other genetic and non-genetic factors appear to be important in maintaining the integrity of these species.  相似文献   
25.
INTRODUCTION Blood-Pb levels are taken as representative of dose/exposure, as all clinical symptoms resulting from the toxic effects of Pb are manifested mainly in blood. Lead exposure of children correlates with de- creased IQ, symptoms of hyper kinesis or minima brain dysfunction, poor learning, or defects in specific neuromotor tasks (Landgrin et al., 1980). Large number of observations over the years has associated lead exposure with human diseases (McMichael and Johnson, 1982). Ca…  相似文献   
26.
The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.  相似文献   
27.
28.
We studied the membrane potentials of normal, essential hypertensive, diabetes mellitus and rheumatoid arthritic polymorphonuclear leukocytes (PMNL). It was found that diabetic PMNL were grossly hyperpolarized as compared to normal. On the other hand hypertensive and arthritic PMNL elicited a significant depolarization. The PMNL obtained from treated hypertensive patients showed considerable recovery where as partial recovery was evidenced in membrane potentials in diabetic and arthritic PMNL. The implications are discussed.  相似文献   
29.
Educational technology research and development - Social-Media-Based Learning (SMBL) is the use of social-media-based platforms, such as Twitter, Google Plus, Facebook, and YouTube, for learning...  相似文献   
30.
The characteristics of the online environment alter how students and instructors interact. Scientific discourse among students and instructors in an online text-only synchronous environment was analyzed. In converting dialogue to text, many of the nonverbal cues, such as facial expression and tone of voice, which instructors use to gauge student understanding are lost. The participants adapt their communication style to the medium, and we present a new interaction pattern for student–instructor communication found prevalent in the synchronous, text-only, online environment. This study has implications for instructors who use synchronous, text-based communication for their courses, namely the value of posing additional questions from the instructor to verify student understanding.  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