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   1381826篇
  免费   103914篇
  国内免费   4375篇
耳鼻咽喉   17260篇
儿科学   45030篇
妇产科学   37434篇
基础医学   203859篇
口腔科学   36943篇
临床医学   134729篇
内科学   267112篇
皮肤病学   27259篇
神经病学   116594篇
特种医学   49922篇
外国民族医学   369篇
外科学   190079篇
综合类   29442篇
现状与发展   1篇
一般理论   508篇
预防医学   118732篇
眼科学   30169篇
药学   101908篇
  8篇
中国医学   3234篇
肿瘤学   79523篇
  2021年   11807篇
  2019年   12408篇
  2018年   17211篇
  2017年   13025篇
  2016年   13988篇
  2015年   16078篇
  2014年   21984篇
  2013年   33738篇
  2012年   46711篇
  2011年   49401篇
  2010年   28523篇
  2009年   26204篇
  2008年   44950篇
  2007年   47444篇
  2006年   47495篇
  2005年   45718篇
  2004年   43645篇
  2003年   41385篇
  2002年   40166篇
  2001年   61887篇
  2000年   63594篇
  1999年   53263篇
  1998年   15082篇
  1997年   13751篇
  1996年   13550篇
  1995年   12847篇
  1994年   11991篇
  1993年   11242篇
  1992年   42396篇
  1991年   41599篇
  1990年   40201篇
  1989年   38092篇
  1988年   35227篇
  1987年   34416篇
  1986年   32849篇
  1985年   31362篇
  1984年   23604篇
  1983年   20047篇
  1982年   12088篇
  1979年   21340篇
  1978年   15214篇
  1977年   12406篇
  1976年   12223篇
  1975年   12430篇
  1974年   15208篇
  1973年   14829篇
  1972年   13664篇
  1971年   12704篇
  1970年   11722篇
  1969年   10656篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The aim of the present study was to explore differences in the clinical expression, clinical diagnoses and management of airway diseases in a primary-care setting. Patients aged >or=35 yrs who had ever smoked were enrolled when they presented for any reason to one of eight rural primary-care practices. Respiratory symptom questionnaires and spirometry were administered. In total, 1,034 patients had acceptable and reproducible spirometry, of whom 550 (53%) were males and 484 (47%) were females. Males smoked more than females (41.2 versus 29.2 pack-yrs) respectively, and were more likely to have a pre-bronchodilator forced expiratory volume in one second/forced vital capacity <0.70 at 22.4 versus 11.8%, respectively. However, more females than males reported breathlessness (51.0 versus 42.8%, respectively), a prior diagnosis compatible with airflow obstruction and taking respiratory medications (23.4 versus 14.9%, respectively). In conclusion, the current results suggest that females are more likely than males to report breathlessness and be prescribed respiratory medications independent of differences in the severity of airflow obstruction.  相似文献   
92.
A very high ventilatory response to hypoxia is believed necessary to reach extreme altitude without oxygen. Alternatively, the excessive ventilation could be counterproductive by exhausting the ventilatory reserve early on. To test these alternatives, 11 elite climbers (2004 Everest-K2 Italian Expedition) were evaluated as follows: 1) at sea level, and 2) at 5,200 m, after 15 days of acclimatisation at altitude. Resting oxygen saturation, minute ventilation, breathing rate, hypoxic ventilatory response, maximal voluntary ventilation, ventilatory reserve (at oxygen saturation = 70%) and two indices of ventilatory efficiency were measured. Everest and K2 summits were reached 29 and 61 days, respectively, after the last measurement. Five climbers summited without oxygen, the other six did not, or succeeded with oxygen (two climbers). At sea level, all data were similar. At 5,200 m, the five summiters without oxygen showed lower resting minute ventilation, breathing rate and ventilatory response to hypoxia, and higher ventilatory reserve and ventilatory efficiency, compared to the other climbers. Thus, the more successful climbers had smaller responses to hypoxia during acclimatisation to 5,200 m, but, as a result, had greater available reserve for the summit. A less sensitive hypoxic response and a greater ventilatory efficiency might increase ventilatory reserve and allow sustainable ventilation in the extreme hypoxia at the summit.  相似文献   
93.
There are no data available combining transbronchial needle aspiration (TBNA) of mediastinal lymph nodes and positron emission tomography (PET) in the staging of nonsmall cell lung cancer (NSCLC). The aim of the current study was to determine if these two methods can enhance the negative predictive value of the individual modality alone, for a specific lymph node station, and if this integrated approach can reduce the number of mediastinoscopies. A total of 113 patients with enlarged mediastinal lymph nodes (> or = 1 cm), who underwent both TBNA and PET scanning, were included. In 51 patients, histopathology, confirmed by surgical lymph node dissection, was compared with PET results and TBNA. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy to detect malignant lymphadenopathy was 68 (13/19), 89 (119/134), 46 (13/28), 95 (119/125) and 86% (132/152) for PET, respectively; 54% (6/11), 100 (53/53), 100 (6/6), 91 (53/58) and 92% (59/64), respectively for TBNA; and 100 (11/11), 94 (50/53), 79 (11/14), 100 (50/50) and 95 (61/64) for combined TBNA and PET, respectively. Combination of transbronchial needle aspiration and positron emission tomography has the potential to allow adequate mediastinal staging of nonsmall cell lung cancer with enlarged lymph nodes in most patients without the need for mediastinoscopy.  相似文献   
94.
95.
96.
BACKGROUND: Impaired neuropsychological test performance, especially on tests of executive function and attention, is often seen in children diagnosed with autism spectrum disorders (ASD). Structures involved in fronto-striatal circuitry, such as the caudate nucleus, may support these cognitive abilities. However, few studies have examined caudate volumes specifically in children with ASD, or correlated caudate volumes to cognitive ability. METHODS: Neuropsychological test scores and caudate volumes of children with ASD were compared to those of children with bipolar disorder (BD) and of typically developing (TD) children. The relationship between test performance and caudate volumes was analyzed. RESULTS: The ASD group displayed larger right and left caudate volumes, and modest executive deficits, compared to TD controls. While caudate volume inversely predicted performance on the Wisconsin Card Sorting Test in all participants, it differentially predicted performance on measures of attention across the ASD, BD and TD groups. CONCLUSIONS: Larger caudate volumes were related to impaired problem solving. On a test of attention, larger left caudate volumes predicted increased impulsivity and more omission errors in the ASD group as compared to the TD group, however smaller volume predicted poorer discriminant responding as compared to the BD group.  相似文献   
97.
98.
99.
PURPOSE: Recommendations of the interdisciplinary Safe Medication Use Expert Committee of the United States Pharmacopeia (USP) to assist health care professionals, manufacturers, and organizations in handling neuromuscular blocking agents (NMBAs) safely and effectively are discussed. SUMMARY: Review and analysis of the USP Medication Errors Reporting Program and MEDMARX program databases showed a continuing risk of patient harm or death due to errors with NMBAs. Medication errors involving wrong concentrations, wrong doses, wrong drugs, look-alike packaging, and sound-alike names, combined with lack of monitoring and communication, have been associated with the use of NMBAs in health care institutions. Serious adverse events occur when NMBAs are used without adequate safeguards. Recommendations for improving safety were developed through review and discussion of root causes and areas of concern with these medications. CONCLUSION: Medical errors with NMBAs continue to result in patient morbidity and mortality. Increased awareness and action on the part of all parties involved are needed to improve the safety of this class of medications.  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