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   6212篇
  免费   520篇
  国内免费   127篇
耳鼻咽喉   47篇
儿科学   209篇
妇产科学   147篇
基础医学   846篇
口腔科学   284篇
临床医学   559篇
内科学   1326篇
皮肤病学   143篇
神经病学   536篇
特种医学   483篇
外国民族医学   2篇
外科学   872篇
综合类   70篇
预防医学   374篇
眼科学   63篇
药学   365篇
中国医学   10篇
肿瘤学   523篇
  2023年   31篇
  2022年   47篇
  2021年   129篇
  2020年   101篇
  2019年   149篇
  2018年   180篇
  2017年   112篇
  2016年   144篇
  2015年   170篇
  2014年   200篇
  2013年   252篇
  2012年   299篇
  2011年   301篇
  2010年   221篇
  2009年   201篇
  2008年   228篇
  2007年   293篇
  2006年   229篇
  2005年   263篇
  2004年   204篇
  2003年   211篇
  2002年   213篇
  2001年   153篇
  2000年   164篇
  1999年   147篇
  1998年   147篇
  1997年   144篇
  1996年   140篇
  1995年   104篇
  1994年   107篇
  1993年   105篇
  1992年   106篇
  1991年   114篇
  1990年   117篇
  1989年   127篇
  1988年   95篇
  1987年   128篇
  1986年   83篇
  1985年   105篇
  1984年   60篇
  1983年   53篇
  1982年   42篇
  1981年   43篇
  1980年   43篇
  1979年   45篇
  1978年   35篇
  1977年   32篇
  1976年   40篇
  1973年   26篇
  1967年   26篇
排序方式: 共有6859条查询结果,搜索用时 15 毫秒
131.
The design of a novel band-pass filter with narrow-band features based on an electromagnetic resonator at 6.4 GHz is presented. A prototype is manufactured and characterized in terms of transmission and reflection coefficient. The selective passband and suppression of the second harmonic make the filter suitable to be used in a C band frequency range for radar systems and satellite/terrestrial applications. To avoid substantial interference for this kind of applications, passive components with narrow band features and small dimensions are required. Between 3.6 GHz and 4.2 GHz the band-pass filter with harmonic suppression should have an attenuation of at least 35 dB, whereas for a passband, less than 10% is sufficient.  相似文献   
132.
Head and neck soft tissue sarcomas are a group of rare heterogeneous tumours arising from embryonic mesoderm. They comprise <1% of all head and neck malignancies and 5–15% of all sarcomas with most head and neck sarcomas arising from soft tissues. Although rare, they are associated with both high recurrence and mortality rates. We review the current management of head and neck soft tissue sarcomas.  相似文献   
133.
ObjectivesTo determine the impact of energy density on diet quality and anthropometric proxy measures for central body fat in young Spaniards.MethodsData were obtained from a representative national sample of 2513 young Spaniards aged 10 to 24 y. Dietary assessment was performed with a 24-h recall. Adherence to the Mediterranean diet was measured by the KIDMED index. Reduced rank regression analysis was used to identify energy-density dietary patterns. Waist circumferences and height were measured.ResultsPastries and sausages showed the strongest loading for the dietary energy density factor score (DED-FS), with fruits and vegetables at the opposite end of the scale. Multiple linear regression analysis showed a positive association (P < 0.01) of dietary energy density (DED) and the DED-FS with waist circumferences regressed on height and age (WCheight+age) and waist-to-height ratio (WHtR). The adjusted odds ratio for elevated WCheight+age and WHtR increased across quartile distribution of DED (P < 0.001) and DED-FS (P < 0.05). Diet quality characterized by the KIDMED index was negatively associated (P < 0.001) with DED and the DED-FS.ConclusionsHigher DED is a risk for increased central fat distribution and is associated with low adherence to the Mediterranean diet.  相似文献   
134.
135.
Glioblastoma‐initiating cells (GICs) represent a stem cell‐like subpopulation within malignant glioblastomas responsible for tumor development, progression, therapeutic resistance, and tumor relapse. Thus, eradication of this subpopulation is essential to achieve stable, long‐lasting remission. We have previously reported that melatonin decreases cell proliferation of glioblastoma cells both in vitro and in vivo and synergistically increases effectiveness of drugs in glioblastoma cells and also in GICs. In this study, we evaluated the effect of the indolamine alone in GICs and found that melatonin treatment reduces GICs proliferation and induces a decrease in self‐renewal and clonogenic ability accompanied by a reduction in the expression of stem cell markers. Moreover, our results also indicate that melatonin treatment, by modulating stem cell properties, induces cell death with ultrastructural features of autophagy. Thus, data reported here reinforce the therapeutic potential of melatonin as a treatment of malignant glioblastoma both by inhibiting tumor bulk proliferation or killing GICs, and simultaneously enhancing the effect of chemotherapy.  相似文献   
136.

Summary  

In a cross-sectional study including 324 patients older than 65 years admitted to our hospital for osteoporotic hip fracture, we found that those patients with a more severe vitamin D deficiency had more severe osteoporotic hip fractures (Garden grades III–IV and Kyle III–IV).  相似文献   
137.
138.
139.
Coupled with the growth of the older population, an increase in the prevalence of overweight and obesity in this age group has occurred in the last decades. The main aims of the present study were (i) to provide an updated prevalence of overweight and obesity in a representative sample of the Spanish elderly population; (ii) to calculate the prevalence of sarcopenic obesity (SO) and (iii) to analyse the relationships between adiposity measurements and lifestyle. A cross‐sectional study was carried out in a sample of 3136 persons representative of the non‐institutionalized population ≥65 years of age. Anthropometric measurements were obtained using standardized techniques and equipment. Overall, 84% of the population can be categorized as overweight and/or obese. The present study indicates that 67% of the Spanish elderly population has an increased percentage of fat mass and more than 56% suffer from central obesity. Moreover, SO is present in 15% of the Spanish elderly population. Finally, a strong relationship between both physically active and sedentary lifestyles and the level of adiposity was found. Prevalence of overweight and obesity among elderly people in Spain is very high and is still increasing. Lifestyle seems to be a determinant factor in the development of obesity among elderly people.  相似文献   
140.
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