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   1601814篇
  免费   131514篇
  国内免费   2581篇
耳鼻咽喉   21646篇
儿科学   52947篇
妇产科学   46235篇
基础医学   227768篇
口腔科学   47204篇
临床医学   140927篇
内科学   314793篇
皮肤病学   34090篇
神经病学   130127篇
特种医学   64735篇
外国民族医学   474篇
外科学   243800篇
综合类   39713篇
现状与发展   3篇
一般理论   544篇
预防医学   122893篇
眼科学   36470篇
药学   121276篇
  3篇
中国医学   2974篇
肿瘤学   87287篇
  2018年   14767篇
  2016年   12900篇
  2015年   15027篇
  2014年   20650篇
  2013年   31354篇
  2012年   42550篇
  2011年   44760篇
  2010年   26342篇
  2009年   25308篇
  2008年   43004篇
  2007年   45251篇
  2006年   46059篇
  2005年   44682篇
  2004年   44096篇
  2003年   42194篇
  2002年   41301篇
  2001年   75685篇
  2000年   78328篇
  1999年   66393篇
  1998年   17737篇
  1997年   16338篇
  1996年   16316篇
  1995年   16021篇
  1994年   15070篇
  1993年   14218篇
  1992年   55427篇
  1991年   53775篇
  1990年   52563篇
  1989年   50834篇
  1988年   47221篇
  1987年   46561篇
  1986年   44286篇
  1985年   42844篇
  1984年   32036篇
  1983年   27570篇
  1982年   16147篇
  1981年   14436篇
  1980年   13565篇
  1979年   30462篇
  1978年   21065篇
  1977年   17765篇
  1976年   16697篇
  1975年   17576篇
  1974年   21488篇
  1973年   20674篇
  1972年   18857篇
  1971年   17771篇
  1970年   16289篇
  1969年   15269篇
  1968年   13949篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
131.
The incidence of asthma has been reported to be associated with obesity. An alternative analysis, of net change in prevalence, does not require exclusion of those with asthma at baseline. Follow-up data were obtained from 9,552 participants in the European Community Respiratory Health Survey and the Swiss cohort Study on Air Pollution and Lung Disease in Adults. Incidence of asthma was analysed by proportional hazards regression, and net changes in symptoms and asthma status by generalised estimating equations, by obesity group. Incidence and net change in ever having had asthma were greater in females than in males, and in participants who remained obese compared with those who were never obese (hazard ratio 2.00, 95% confidence interval 1.25-3.20; excess net change 2.8%, 0.4-5.3% per 10 yrs). The effect of being obese on net change in diagnosed asthma was greater in females than in males, but for net change in wheeze without a cold it was greater in males. The present results are consistent with asthma being more frequently diagnosed in females, especially obese females. These findings may help to explain the reports of a stronger association between asthma and obesity in females than in males.  相似文献   
132.
133.
134.
OBJECTIVE: To prospectively determine the sonographic findings of nodular hyperplasia of the thyroid, to compare these with reported findings associated with malignancy, and to assess interobserver reliability. METHODS: Seventy thyroid nodules were scanned, and then biopsies of the nodules were performed under sonographic guidance with fine-needle cytologic analysis; in all cases images were reviewed by 2 experienced radiologists without knowledge of clinical outcome. Findings reported associated with malignancy were specifically assessed. Interobserver agreement between the expert and secondary readers for each finding was calculated by the kappa or weighted kappa statistic and the Fisher exact test of independence. RESULTS: There were 68 benign and 2 malignant nodules in a population of 63 female and 7 male patients. The mean benign nodule size was 2.9 cm; 60% were solid; 54% were hypoechoic; 59% were microlobulated or macrolobulated; 47% had central vascularity; 24% contained calcifications; and 82% were elliptical in shape. There was very good interobserver reliability for the presence of calcium (kappa = 0.91) and good agreement for the presence and location of vascularity (kappa = 0.75) and the amount of cystic components (kappa = 0.62; all P < .01). CONCLUSIONS: Sixty-nine percent of benign nodules had at least 1 finding reported previously as associated with malignancy. The interobserver reliability of the sonographic findings was good to very good for 3 of the 5 findings assessed.  相似文献   
135.
136.
One serious complication of neurofibromatosis type 1 (NF1) is the development of malignant peripheral nerve sheath tumours (MPNSTs). These malignancies often develop within pre-existing plexiform neurofibromas and their development is now thought to be associated with both tumour suppressor gene mutations and dysregulated growth factor signalling. Recent work demonstrates that the lifetime risk of malignant transformation is significantly greater than previously thought. Ionising radiation, a long-standing disease, particularly the presence of a large number of plexiform neurofibromas from an early age, are suggested risk factors. We present an NF1 patient who developed an MPNST of the cervical vagus nerve which was successfully treated with surgery. Close monitoring of patients with NF and a high level of suspicion towards rapidly enlarging and painful swellings is merited as these features may signify malignant transformation. Whether a positive history of MPNST in other affected family members predisposes the individual to a higher risk of malignant transformation is unclear.  相似文献   
137.
138.
139.
In the last 20 years, cases of human cryptococcosis, have increased in immunocompromised patients. In several instances, the cases have been associated with the exposure of the patients to bird droppings. In order to investigate birds of prey as potential carriers and spreaders of Cryptococcus neoformans and other yeasts of importance in human infections, 182 swab samples were collected from the cloacae of several species of birds of prey (Group I) and 32 faecal samples from aviaries in which the birds were housed (Group II). Samples were also taken from digestive tract of 60 dead birds (Group III). A total of 454 samples were cultured from which 215 colonies of yeastlike fungi were recovered and identified. Cryptococcusneoformans var. grubii was isolated from three cloacae samples (4.8%) collected from Falco tinnunculus and from one sample (3.1%) obtained from Buteo buteo, as well as from samples collected at the aviaries in which these birds were kept. Overall, 18 samples (9.9%) from Group I, 13 (40.6%) from Group II, 12 crops (20%), three proventriculi (5%) and 12 cloacae (20%) from Group III yielded positive cultures for yeasts. The results indicate that birds of prey and in particular, F. tinnunculus and B. buteo, may act as carriers and spreaders of C. neoformans and other zoonotic yeasts.  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