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   12470篇
  免费   830篇
  国内免费   36篇
耳鼻咽喉   93篇
儿科学   371篇
妇产科学   274篇
基础医学   1419篇
口腔科学   196篇
临床医学   1100篇
内科学   2916篇
皮肤病学   200篇
神经病学   1206篇
特种医学   453篇
外科学   1559篇
综合类   222篇
一般理论   5篇
预防医学   1438篇
眼科学   217篇
药学   908篇
中国医学   57篇
肿瘤学   702篇
  2023年   69篇
  2022年   48篇
  2021年   250篇
  2020年   138篇
  2019年   249篇
  2018年   413篇
  2017年   295篇
  2016年   257篇
  2015年   295篇
  2014年   366篇
  2013年   537篇
  2012年   790篇
  2011年   910篇
  2010年   521篇
  2009年   420篇
  2008年   803篇
  2007年   894篇
  2006年   818篇
  2005年   834篇
  2004年   806篇
  2003年   797篇
  2002年   730篇
  2001年   283篇
  2000年   360篇
  1999年   259篇
  1998年   104篇
  1997年   63篇
  1996年   54篇
  1995年   55篇
  1994年   63篇
  1993年   45篇
  1992年   98篇
  1991年   80篇
  1990年   63篇
  1989年   69篇
  1988年   46篇
  1987年   41篇
  1986年   45篇
  1985年   35篇
  1984年   20篇
  1982年   22篇
  1981年   27篇
  1979年   26篇
  1978年   28篇
  1977年   24篇
  1976年   26篇
  1975年   14篇
  1974年   17篇
  1973年   13篇
  1972年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Primary linitis plastica of the rectum is an infrequent and unusual rectal carcinoma. We report a new case that presented clinically as a haemorrhoidal syndrome. We comment on the characteristics--clinical picture and histopathology--of this uncommon presentation of rectal tumour, as well as its clinical history and prognosis taking into account that the literature consulted indicated the unusualness of primary linitis plastica of the rectum.  相似文献   
52.
53.
OBJECTIVE: The purpose of this study was to examine the predictive relationship of categorization and deductive reasoning abilities to performance of instrumental activities of daily living (IADL) among adults with brain injury. METHOD: A correlational research design was used to examine the performance of 19 patients from a neurosurgery acute care unit on Toglia's Category Assessment (TCA), the Deductive Reasoning test (DR), and the Observed Tasks of Daily Living-Revised. RESULTS: Multiple regression analysis indicated that categorization and deductive reasoning accounted for a significant proportion of the variance in IADL performance scores, with deductive reasoning making the greater contribution. Demographic characteristics such as age and education reduced the power of the previous variables, especially of the categorization. CONCLUSION: The results of this study indicate that assessments of categorization and deductive reasoning abilities of persons with brain injury may be good predictors of IADL functional performance. Results support the use of the TCA and DR as quick measures of a person's cognitive and functional abilities. Furthermore, this study provides preliminary results to support that categorization and deductive reasoning abilities are fundamental for the performance of IADL skills.  相似文献   
54.
55.
56.
57.
58.
Melatonin is a pineal hormone that regulates the human cycle of sleep and wakefulness. Plasma melatonin levels were investigated in patients with obstructive sleep apnoea syndrome (OSAS). In total, 20 patients with OSAS and 11 healthy controls were studied. OSAS patients were tested twice: on the night of diagnostic polysomnography and the night of continuous positive airway pressure (CPAP) titration. Controls were tested on one occasion. Plasma melatonin levels were determined at 23:00 h (light period), at 02:00 h (dark period) and at 06:00 h (light period) in patients and control subjects using the radioimmunoassay method. The control subjects showed a nocturnal melatonin peak value at 02:00 h (70.6+/-14 pg.mL(-1)). However, this nocturnal melatonin peak was absent in the OSAS patients. The highest melatonin value was found in OSAS patients on the night of diagnosis, at 06:00 h (49.3+/-36.8 pg.mL(-1)). It was found that the melatonin level in OSAS patients at 06:00 h was significantly lower in the night of titration (35.6+/-37.9 pg.mL(-1)) than in the diagnosis night. However, the melatonin levels at either 23:00 h or 02:00 h in OSAS patients did not differ significantly when comparing levels in the night of diagnostic polysomnography (23:00 h: 31.6+/-29.8 pg.mL(-1); 02:00 h: 47.4+/-33.8 pg.mL(-1)) with levels in the night of CPAP titration (23:00 h: 20.2+/-10.3 pg.mL(-1); 02:00 h: 37.7+/-27.5 pg.mL(-1)). Patients with obstructive sleep apnoea syndrome have an abnormal melatonin secretion pattern. The absence of a nocturnal serum melatonin peak could be partially related to the difficulty that these patients have in achieving a normal sleep-wakefulness pattern.  相似文献   
59.
In the study of asthma, a vital role is played by mouse models, because knockout or transgenic methods can be used to alter disease pathways and identify therapeutic targets that affect lung function. Assessment of lung function in rodents by available methods is insensitive because these techniques lack regional specificity. A more sensitive method for evaluating lung function in human asthma patients uses hyperpolarized (HP) (3)He MRI before and after bronchoconstriction induced by methacholine (MCh). We now report the ability to perform such (3)He imaging of MCh response in mice, where voxels must be approximately 3000 times smaller than in humans and (3)He diffusion becomes an impediment to resolving the airways. We show three-dimensional (3D) images that reveal airway structure down to the fifth branching and visualize ventilation at a resolution of 125 x 125 x 1000 microm(3). Images of ovalbumin (OVA)-sensitized mice acquired after MCh show both airway closure and ventilation loss. To also observe the MCh response in naive mice, we developed a non-slice-selective 2D protocol with 187 x 187 microm(2) resolution that was fast enough to record the MCh response and recovery with 12-s temporal resolution. The extension of (3)He MRI to mouse models should make it a valuable translational tool in asthma research.  相似文献   
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