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   1883篇
  免费   85篇
  国内免费   7篇
耳鼻咽喉   16篇
儿科学   90篇
妇产科学   37篇
基础医学   224篇
口腔科学   103篇
临床医学   148篇
内科学   380篇
皮肤病学   39篇
神经病学   108篇
特种医学   170篇
外科学   144篇
综合类   72篇
预防医学   175篇
眼科学   25篇
药学   117篇
  1篇
中国医学   28篇
肿瘤学   98篇
  2024年   7篇
  2023年   9篇
  2022年   29篇
  2021年   46篇
  2020年   23篇
  2019年   43篇
  2018年   40篇
  2017年   40篇
  2016年   49篇
  2015年   39篇
  2014年   77篇
  2013年   89篇
  2012年   118篇
  2011年   149篇
  2010年   86篇
  2009年   66篇
  2008年   78篇
  2007年   118篇
  2006年   68篇
  2005年   69篇
  2004年   46篇
  2003年   39篇
  2002年   43篇
  2001年   30篇
  2000年   41篇
  1999年   34篇
  1998年   54篇
  1997年   47篇
  1996年   34篇
  1995年   22篇
  1994年   27篇
  1993年   23篇
  1992年   20篇
  1991年   15篇
  1990年   21篇
  1989年   22篇
  1988年   26篇
  1987年   26篇
  1986年   20篇
  1985年   21篇
  1984年   8篇
  1983年   17篇
  1982年   13篇
  1981年   12篇
  1980年   10篇
  1978年   12篇
  1977年   10篇
  1976年   13篇
  1975年   7篇
  1971年   4篇
排序方式: 共有1975条查询结果,搜索用时 15 毫秒
51.
Birthweight is recognized to be a determinant of a full term infant's early growth pattern; however, few studies have explored whether this effect is sustained into school age, especially in developing countries. We have used a cohort study from North East Brazil to investigate factors determining the anthropometric status of eight-year-old children born at full-term with low or appropriate weight. A cohort of 375 full-term infants was recruited at birth in six maternity hospitals between 1993 and 1994, in a poor region of the interior of the State of Pernambuco. At the age of 8 years, 86 born with low birthweight and 127 with appropriate birthweight were traced. Multivariable linear regression analyses were used to identify the net effect of socioeconomic conditions, maternal nutritional status and child factors on weight-for-age and height-for-age. An enter approach was used to estimate the contribution of different factors on child anthropometry. Birthweight had little influence on child nutritional status at school age. Maternal BMI and height together were the biggest contributors to variation in child weight-for-age (12.3%) and height-for-age (13.2%), followed by family socioeconomic conditions. Maternal height as a proxy of maternal constraint was the single factor that best explained the variation in both indices (6.2% for weight-for-age and 11.1% for height-for-age). Haemoglobin level measured at eight years made a small but significant contribution to variation in height-for-age (5.6%) and weight for age (1.4%). Maternal nutritional status, reflecting genetic inheritance and the poor socioeconomic conditions of this population, was the most important determinant of the nutritional status of children at school age, rather than birthweight.  相似文献   
52.
Nitric oxide (NO) participates in the regulation of many cell functions in the CNS, including modulation of ion channel function by direct changes in the channel protein structure, modulating permeability or gating kinetics. The mechanisms by which NO donors modulate sodium currents are protein and tissue specific. The present paper concerns sodium currents in the neuroblastoma N1E-115 cell line, applying whole-cell voltage clamp methods. Sodium currents were characterized in terms of the sensitivity to NO donors and the hydrophilic thiol oxidizer thimerosal. Parameters defining steady-state inactivation and activation, removal of inactivation and the voltage dependence of inactivation, were determined before and after thimerosal application. The results concerning the application of thimerosal showed blockade of the resting state, hyperpolarizing shifts of m(infinity) and h(infinity) curves, change in the voltage sensitivity and slower inactivating kinetics, tau(hf) and tau(hs) being affected in the same manner. The present results provide clear evidence for redox modulation of the sodium channel population in N1E-115 cells. Our results showed that the membrane-permeable alkylating agent (NEM) does not inhibit current reduction determined by thimerosal. We have reasons to suspect that the sodium channel population in N1E-115 cells differs in the proposed consensus sequence for nitrosylation or thimerosal cysteine oxidation.  相似文献   
53.
54.
The aim of this study was to report an unusual case of mucoepidermoid carcinoma (MEC) in a 39-year-old woman. The tumor showed a prominent population of clear and intermediate basal cells. Clear cells rarely predominate over other cell types. Such cases are called clear cell variant of MEC. The case also revealed a variable amount of calcified material in the tumor mass. Calcifications are rare in clear cell MEC. These structures were periodic acid-Schiff positive and diastase resistant, excluding glycogen origin. Immunohistochemistry was performed, and the epidermoid component was positive for cytokeratin (CK)7, CK13, CK14, and CK19. The mucous and clear cells presented mild staining for CK7. Cytokeratins 7, 13, and 19 stained luminal cells, and intermediate cells exhibited positivity for CK7, CK14, and vimentin. The origin of the calcifications is speculated to be the result of dystrophic calcification of the amorphous eosinophilic material secreted by intermediate basal cells.  相似文献   
55.
56.
OBJECTIVE: To determine if there is a relationship between parental perception of neighborhood safety and overweight at the age of 7 years. DESIGN: Cross-sectional analysis of the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. SETTING: Ten urban and rural US sites. PARTICIPANTS: A total of 768 children selected via conditional random sampling with complete data at follow-up. MAIN OUTCOME MEASURES: Parents reported demographics and perception of neighborhood safety by standardized questionnaire. Child overweight status was defined as a body mass index greater than or equal to the 95th percentile for age and sex from measured anthropometrics at the age of 7 years. The base model included relationship of the safety reporter to the child, sex, and baseline body mass index z score at the age of 4.5 years. Covariates tested included maternal marital status, education, and depressive symptoms; child race/ethnicity; participation in structured after-school activities; Home Observation for Measurement of the Environment total score; and neighborhood social cohesiveness. RESULTS: The sample was 85% white, and 10% of the children were overweight. Neighborhood safety ratings in the lowest quartile were independently associated with a higher risk of overweight at the age of 7 years compared with safety ratings in the highest quartile (adjusted odds ratio, 4.43; 95% confidence interval, 2.03-9.65). None of the candidate covariates altered the relationship between perception of neighborhood safety and child overweight status. CONCLUSIONS: Perception of the neighborhood as less safe was independently associated with an increased risk of overweight at the age of 7 years. Public health efforts may benefit from policies directed toward improving both actual and perceived neighborhood safety.  相似文献   
57.
Migration of intradural epidermoid matrix: embryologic implications.   总被引:4,自引:0,他引:4  
The migratory behavior of acquired cholesteatoma matrices (those arising from the tympanic membrane) has been described previously. This tissue is derived embryologically from the first branchial groove and represents the only migratory epithelium arising from the branchial groove system. If the matrix from a cerebellopontine angle (CPA) epidermoid tumor exhibits migratory behavior similar to that of acquired cholesteatomas, a first branchial groove site of origin for CPA epidermoids would be supported. Intradural CPA epidermoid cells were grown in alpha-minimum essential medium. The cultures were examined daily, and cell mass migration rates were measured. It was observed that intradural epidermoid tumor matrix harvested from the CPA exhibited migration in vitro. Its migratory properties were indistinguishable from those of acquired cholesteatomas, which are embryologically derived from the first branchial groove. These data support the theory that purely intradural epidermoids are derived from cells of the first branchial groove.  相似文献   
58.
59.
60.
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