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   3053篇
  免费   107篇
  国内免费   11篇
耳鼻咽喉   81篇
儿科学   85篇
妇产科学   101篇
基础医学   379篇
口腔科学   54篇
临床医学   273篇
内科学   419篇
皮肤病学   94篇
神经病学   347篇
特种医学   194篇
外科学   492篇
综合类   27篇
预防医学   212篇
眼科学   109篇
药学   135篇
中国医学   3篇
肿瘤学   166篇
  2022年   11篇
  2021年   38篇
  2020年   17篇
  2019年   34篇
  2018年   48篇
  2017年   50篇
  2016年   45篇
  2015年   91篇
  2014年   122篇
  2013年   117篇
  2012年   135篇
  2011年   176篇
  2010年   126篇
  2009年   132篇
  2008年   193篇
  2007年   170篇
  2006年   151篇
  2005年   193篇
  2004年   160篇
  2003年   150篇
  2002年   93篇
  2001年   77篇
  2000年   92篇
  1999年   120篇
  1998年   22篇
  1997年   23篇
  1996年   19篇
  1995年   12篇
  1994年   18篇
  1992年   32篇
  1991年   35篇
  1990年   39篇
  1989年   20篇
  1988年   19篇
  1987年   18篇
  1986年   22篇
  1985年   15篇
  1984年   22篇
  1983年   14篇
  1979年   16篇
  1978年   10篇
  1977年   12篇
  1976年   10篇
  1975年   17篇
  1974年   16篇
  1972年   17篇
  1971年   10篇
  1970年   11篇
  1968年   16篇
  1967年   9篇
排序方式: 共有3171条查询结果,搜索用时 15 毫秒
91.
92.
The diet of school-aged children in north-west Namibia was investigated. Data on food consumption were collected using the 24-h recall interview method. The field study was conducted during the dry season. The subjects were schoolchildren aged between 8 and 15 years living in either a small town (n=43) or a rural area (n=10). In town, the main sources of energy were maize porridge and wheat bread, and for the rural children, sour milk and maize. The consumption of vegetables, fruit and legumes was very low in both groups. The mean intakes of energy were 6.7 MJ/day for children living in town and 4.7 MJ/day for rural subjects. The intakes of vitamin A, vitamin C and folate were inadequate in both groups. Our findings show that during the dry season, the diets of Namibian school-aged children are monotonous.  相似文献   
93.
94.
Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy, and therefore, mandibular setback surgery has the potential to diminish airway size. The purpose of this study was to evaluate the long-term effect of mandibular setback surgery on the airway size. The material consisted of pre- and postoperative (minimum 1 year) lateral radiograms of 22 individuals (18 females and 4 males) with a mean age of 30 years, who had undergone mandibular setback surgery to correct skeletal Class III discrepancies. Hard and soft tissue points were digitized with a Numonics Accugrid digitizer and analyzed with Xmetrix software. A paired t test was used to evaluate the difference between pre- and postoperative measurements. In addition, Pearson's coefficient correlation was calculated to reveal the possible association between the skeletal change in relation to the change in airway size. The mean value for the initial SNA was 81.3 degrees, 85.4 degrees for SNB, 36.9 degrees for S-Na/MP, and for the posterior airway, 10.5 mm and 12.0 mm retropalatinally and retrolingually, respectively. At the postoperative evaluation, SNB was 80.7 degrees, S-Na/MP 41.0 degrees, and the posterior airway retropalatinally 8.3 mm and retrolingually 9.8 mm. Statistical analysis revealed a highly significant correlation between the change in the ANB angle and in the S-Na/MP angle versus the change in the upper airway size, both retropalatinally and retrolingually. Mandibular setback surgery with posterior rotation may gradually result in increased upper airway resistance in cases where neuromuscular adaptation is insufficient to compensate for the reduction in the airway size. Therefore, large anteroposterior discrepancies should be corrected by combined maxillary and mandibular osteotomies.  相似文献   
95.
96.
There are an increasing number of possible applications for the use of Erbium:YAG and Neodymium:YAG lasers in opthalmology. Laser-phacoemulsification as well as Erbium-laser vitrectomy is of major interest. We report on the underlying technology and more than 1-year-experience using the PHACOLASE (Asclepion-Meditec, Jena, Germany, 10–100 Hz frequency, 5–50 mJ single pulse energy) for phacoemulsification and pars plana vitrectomy and the Lyla-Dodick laser photolysis (A.R.C. Laser, Eckental-Forth, Germany, 1–20 Hz, up to 8 mJ single pulse energy). The Erbium:YAG-laser as well as the Neodymium:YAG-laser enabled us to extract lenses with up to medium hard nuclei. Moreover, the Erbium laser enabled fast vitrectomy with little mechanical traction. In many of our initial surgical operations we had to change to mechanical vitrectomy due to initial technical problems. No new complications occurred intra- or postoperatively. The handpiece worked well in removing vitreous bodies, but was not feasable for cutting membranes. Modified handpieces for this purpose are under development.  相似文献   
97.
A role for decorin in the structural organization of periodontal ligament   总被引:5,自引:0,他引:5  
Decorin is a small leucine-rich proteoglycan that interacts with several matrix molecules, including various types of collagen and growth factors, and suppresses the growth of neoplastic cells by an epidermal growth factor (EGF) receptor-mediated pathway. Decorin is abundantly expressed in the periodontal connective tissues during development and tissue maintenance. In periodontal disease, which is one of the most common diseases in the human kind, the level of decorin is decreased in the periodontal connective tissue. Abnormal expression of decorin may also associate with certain inherited disorders that involve increased susceptibility to severe periodontal disease in the early childhood. Therefore, we investigated the periodontal tissues of mice with targeted disruption of the decorin gene. Gross and microscopic analyses showed that decorin-deficient mice appeared to have normal tooth development and eruption, and there were no signs of periodontal disease. However, electron microscopic analysis revealed abnormal morphology and organization of the collagen fibrils in the periodontal ligament. The number of periodontal ligament fibroblasts in the decorin-deficient mice was also increased about two-fold as compared with the wild-type mice. In cell culture, ectopic overexpression of decorin in NIH 3T3 fibroblasts or decorin added exogenously to periodontal fibroblasts suppressed cell growth. However, blocking the EGF receptor tyrosine kinase activity did not prevent the decorin-elicited growth suppression in periodontal fibroblasts. Additionally, decorin did not induce a marked increase in the relative expression of p21 mRNA in periodontal fibroblasts. Therefore, decorin appeared to regulate growth of normal periodontal fibroblasts by a mechanism distinct from that reported for neoplastic cells. The findings demonstrate that decorin plays a role in the organization of collagen fibrils and regulates cell proliferation in the periodontal ligament.  相似文献   
98.
The p53 gene located at chromosome 17pl3 is found to be altered (allelic loss or other mutation) in multiple human cancers, including osteosarcomas. The mutated gene produces a protein with a prolonged half-life thus rendering it detectable by conventional immunohistochemistry. We examined the correlation between p53 expression and clinical prognosis as well as response to therapy. Twentyone patients with previously untreated and histologically verified highly malignant osteosarcoma were used for this study. Biopsy material taken both prior to the start of COSS 91 protocol and at the time of surgery (ten weeks later) was examined for alterations in p53 protein expression and drug resistance. Two patients who had strong (+++) p53 protein expression and three others who became positive during the chemotherapy had significantly worse prognosis (all of them died within one year) than those who showed no p53 expression both at biopsy and after chemotherapy (all 11 patients are alive, average follow-up time: 3.5 years). All patients who showed any kind of positive p53 protein expression on initial biopsy were non-respon-ders to chemotherapy. In contrast, 69% (9 out of 13) of those who exhibited no p53 expression on initial biopsy were responders or intermediate responders to chemotherapy. We concluded that p53 expression may be a useful prognostic factor in osteosarcomas. The direct correlation between p53 positive expression and resistance to therapy can help in identifying patients who are in need of a more vigorous or different chemotherapeutical protocol.  相似文献   
99.
While caring for patients with chronic low back pain, a standardized measurement of pain and pain-related reduction of the quality of life is needed. Easy application and data collection are decisive for routine use. The Oswestry Low Back Pain Disability Questionnaire is an internationally widely used instrument, which was now scrutinized in 148 patients in two orthopedic hospitals. A higher pain disability was related to age, female gender, limitations experienced in social life, impact of pain, use of analgetics, low net income, and patients in Eastern Germany. The available German version of the questionnaire is suitable for daily use to measure the intensity of pain and pain-related disability in everyday life, including social impairment due to low back pain.  相似文献   
100.
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