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   16347篇
  免费   980篇
  国内免费   90篇
耳鼻咽喉   102篇
儿科学   393篇
妇产科学   393篇
基础医学   2042篇
口腔科学   343篇
临床医学   1561篇
内科学   3779篇
皮肤病学   225篇
神经病学   1820篇
特种医学   758篇
外科学   2361篇
综合类   67篇
一般理论   6篇
预防医学   1129篇
眼科学   321篇
药学   955篇
中国医学   35篇
肿瘤学   1127篇
  2024年   22篇
  2023年   196篇
  2022年   291篇
  2021年   509篇
  2020年   389篇
  2019年   456篇
  2018年   543篇
  2017年   420篇
  2016年   501篇
  2015年   500篇
  2014年   686篇
  2013年   873篇
  2012年   1433篇
  2011年   1404篇
  2010年   737篇
  2009年   622篇
  2008年   1110篇
  2007年   1090篇
  2006年   942篇
  2005年   948篇
  2004年   827篇
  2003年   702篇
  2002年   651篇
  2001年   119篇
  2000年   92篇
  1999年   127篇
  1998年   139篇
  1997年   85篇
  1996年   102篇
  1995年   68篇
  1994年   61篇
  1993年   59篇
  1992年   66篇
  1991年   49篇
  1990年   51篇
  1989年   47篇
  1988年   43篇
  1987年   38篇
  1986年   31篇
  1985年   41篇
  1984年   29篇
  1983年   35篇
  1982年   17篇
  1981年   26篇
  1979年   17篇
  1974年   17篇
  1973年   20篇
  1972年   19篇
  1971年   24篇
  1968年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The objective of this study was to explore the effect of COVID-19 and Ramadan on physical activity (PA) and burnout in teachers and the relationship between them. A total of 57 secondary school teachers from public education centers participated in the present study. They were aged between 29 and 52 years. To determine the effect of Ramadan and COVID-19 on PA and burnout, participants completed the online questionnaires before COVID-19, one week before Ramadan and during the second week of Ramadan. The International Physical Activity Questionnaire-BREF and the Maslach Burnout Inventory-Human Services Survey were used to assess PA intensities and burnout, respectively. The data revealed that total PA (p < 0.001, p < 0.05, respectively) vigorous metabolic equivalent of task (MET) (p < 0.001, p < 0.05, respectively), moderate MET (p < 0.001, p < 0.01, respectively) were higher before COVID-19 and before Ramadan than during Ramadan. Regarding burnout subscales, emotional exhaustion (p < 0.001, p < 0.01, respectively) was higher before Ramadan than before COVID-19 and during Ramadan. A lower personal accomplishment was reported before Ramadan than before COVID-19 and during Ramadan (both p < 0.05). In addition, low to high correlations were observed between PA intensities and burnout subscales, except for the correlation between depersonalization and all PA intensities. In conclusion, Ramadan intermittent fasting along with PA was highly recommended for teachers and the general population to improve positive emotions and general health.  相似文献   
62.
Clinical evidence of non-lymphatic distant metastasis has been reported in approximately 10% of cases of head and neck squamous cell carcinoma (HNSCC). The lungs are the commonest site of distant metastasis of HNSCC, followed by the bones, liver and skin. A 65-year-old male underwent supraglottic laryngectomy and left modified neck dissection for a carcinoma of the laryngeal surface of the epiglottis extending to both false cords. Eight months later the patient underwent right radical modified neck dissection for hypodermal metastatic disease involving the underlying (sternocleidomastoid) muscle. Thirty-two months later, surgical excision of a lesion in the right gluteus maximus muscle was performed. Histological study diagnosed a muscular metastasis with the same morphological aspect as the laryngeal carcinoma. The patient showed no evidence of cervical or distant recurrence at follow-up after 13 months. Although skeletal muscles represent approximately 50% of total body mass and receive a large proportion of total cardiac output, haematogenous metastases to skeletal muscle are extremely uncommon. Most skeletal muscle metastases are of pulmonary origin. Distant skeletal muscle metastasis from HNSCC is an extremely rare occurrence. Treatment options, depending upon the clinical setting, include observation, radiotherapy, chemotherapy and excision; these approaches rarely alter the patient outcome. The prognosis associated with skeletal muscle metastasis is thought to be poor, consistent with the fact that it generally occurs as a feature of systemic spread.  相似文献   
63.
In the last 20 years, gut microbiota in patients with cystic fibrosis (CF) has become an object of interest. It was shown that these patients had gut dysbiosis and this could explain not only the intestinal manifestations of the disease but also part of those involving the respiratory tract. The acquisition of previously unknown information about the importance of some bacteria, i.e., those partially or totally disappeared in the gut of CF patients, in the regulation of the activity and function of the gut and the lung was the base to suggest the use of probiotics in CF patients. The main aim of this paper is to discuss the biological basis for probiotic administration to CF patients and which results could be expected. Literature analysis showed that CF intestinal dysbiosis depends on the same genetic mutations that condition the clinical picture of the diseases and is aggravated by a series of therapeutic interventions, such as dietary modifications, the use of antibiotics, and the administration of antacids. All this translates into a significant worsening of the structure and function of organs, including the lung and intestine, already deeply penalized by the genetic alterations of CF. Probiotics can intervene on dysbiosis, reducing the negative effects derived from it. However, the available data cannot be considered sufficient to indicate that these bacteria are essential elements of CF therapy. Further studies that take into account the still unsolved aspects on how to use probiotics are absolutely necessary.  相似文献   
64.
OBJECTIVEIn a large, multiethnic cohort of youths with obesity, we analyzed pathophysiological and genetic mechanisms underlying variations in plasma glucose responses to a 180 min oral glucose tolerance test (OGTT).RESEARCH DESIGN AND METHODSLatent class trajectory analysis was used to identify various glucose response profiles to a nine-point OGTT in 2,378 participants in the Yale Pathogenesis of Youth-Onset T2D study, of whom 1,190 had available TCF7L2 genotyping and 358 had multiple OGTTs over a 5 year follow-up. Insulin sensitivity, clearance, and β-cell function were estimated by glucose, insulin, and C-peptide modeling.RESULTSFour latent classes (1 to 4) were identified based on increasing areas under the curve for glucose. Participants in class 3 and 4 had the worst metabolic and genetic risk profiles, featuring impaired insulin sensitivity, clearance, and β-cell function. Model-predicted probability to be classified as class 1 and 4 increased across ages, while insulin sensitivity and clearance showed transient reductions and β-cell function progressively declined. Insulin sensitivity was the strongest determinant of class assignment at enrollment and of the longitudinal change from class 1 and 2 to higher classes. Transitions between classes 3 and 4 were explained only by changes in β-cell glucose sensitivity.CONCLUSIONSWe identified four glucose response classes in youths with obesity with different genetic risk profiles and progressive impairment in insulin kinetics and action. Insulin sensitivity was the main determinant in the transition between lower and higher glucose classes across ages. In contrast, transitions between the two worst glucose classes were driven only by β-cell glucose sensitivity.  相似文献   
65.
66.
67.
68.
This prospective study evaluated the efficacy of transvaginal ultrasonography combined with water-contrast in the rectum (RWC-TVS) in the diagnosis of rectal infiltration in 35 women with rectovaginal endometriosis; ultrasonographic findings were compared with surgery and histology. The sensitivity of RWC-TVS in identifying rectal infiltration reaching at least the muscular layer was 100%, the specificity was 85.7%, the positive predictive value was 91.3%, and the negative predictive value was 100%. In 4 of 5 (80.0%) nodules reaching the submucosa, the depth of infiltration was underestimated by RWC-TVS. The RWC-TVS reliably determined the largest diameter of the endometriotic nodules and was well tolerated by the patients.  相似文献   
69.
70.
Sodium pancratistatin 3,4- O-cyclic phosphate ( 2) is a novel water-soluble synthetic derivative of pancratistatin ( 1), a natural alkaloid constituent of Amaryllidaceae plants, that exhibits good cytostatic and antineoplastic activity but is highly insoluble. Unlike most other natural alkaloids it does not act by binding to tubulin, and its mechanism of action has yet to be fully elucidated. Here the efficacy of 2 in a human colon adenocarcinoma model, DLD-1, and some understanding of its mode of action are investigated. Agreeing with previous studies, low cytotoxicity in vitro was seen for 2 with IC 50's of 253 and 19.7 microM for 1 and 96 h exposures, respectively. However in vivo the compound caused statistically significant tumor growth delays ( p < 0.01) at its maximum tolerated dose, and significant vascular shutdown and tumor necrosis were observed. Like 1, the compound appeared to have an unconventional mechanism of action with no effect on microtubule structure, yet causing a G 2/M block, while it was seen to disrupt mitochondrial function. The mechanism of action of 1 and 2 appears to be similar. Thus compound 2, being considerably more soluble than 1, has good potential as an anticancer agent, and further investigation is warranted.  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