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   1393386篇
  免费   99295篇
  国内免费   6873篇
耳鼻咽喉   20222篇
儿科学   40989篇
妇产科学   39597篇
基础医学   194455篇
口腔科学   40720篇
临床医学   120163篇
内科学   271216篇
皮肤病学   30847篇
神经病学   109793篇
特种医学   55855篇
外国民族医学   487篇
外科学   213953篇
综合类   38963篇
现状与发展   25篇
一般理论   439篇
预防医学   95911篇
眼科学   32952篇
药学   106127篇
  66篇
中国医学   5942篇
肿瘤学   80832篇
  2018年   13875篇
  2017年   11396篇
  2016年   12373篇
  2015年   14477篇
  2014年   19916篇
  2013年   27919篇
  2012年   37240篇
  2011年   39583篇
  2010年   23585篇
  2009年   22395篇
  2008年   36566篇
  2007年   39688篇
  2006年   40270篇
  2005年   39013篇
  2004年   37096篇
  2003年   36028篇
  2002年   35259篇
  2001年   64666篇
  2000年   66479篇
  1999年   56666篇
  1998年   15529篇
  1997年   14313篇
  1996年   13583篇
  1995年   12820篇
  1994年   11956篇
  1992年   43139篇
  1991年   41591篇
  1990年   40837篇
  1989年   39784篇
  1988年   37196篇
  1987年   36595篇
  1986年   35088篇
  1985年   33246篇
  1984年   24921篇
  1983年   21123篇
  1982年   12706篇
  1981年   11613篇
  1979年   24002篇
  1978年   17101篇
  1977年   14855篇
  1976年   13402篇
  1975年   15303篇
  1974年   18120篇
  1973年   17581篇
  1972年   16830篇
  1971年   15732篇
  1970年   14921篇
  1969年   14357篇
  1968年   13475篇
  1967年   12023篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
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   
112.
113.
114.
The finer branches of the biliary tree (FBBT) contain a regenerative compartment. We hypothesized that preservation of the FBBT together with its microvasculature will lead to recovery of biliary damage and prolonged preservation of bile ductules during the development of chronic liver allograft rejection. The interlobular bile ducts, portal bile ductules and extraportal biliary cells with and without microvessels were studied in sequential biopsies in five patients who fulfilled the Banff criteria of early chronic rejection (CR) (imminence group). Biopsies of CR patients (n = 12) served as controls. Biopsies were double immunostained with CD34 (microvessels) and cytokeratin 7 (biliary structures). Proliferation and proangiogenic activity were assessed with Ki67 and VEGF-A immunostaining. Severe damage of bile ducts in the imminence group did not progress to significant bile duct loss. This was associated with a high proliferative activity in all biliary structures and preservation of the microvascular compartment. VEGF-A expression was increased in all but the reperfusion biopsies. In conclusion, both regenerative activity of the FBBT and an intact microvascular compartment are associated with less damage of the biliary tree and could therefore be prerequisites for biliary regeneration.  相似文献   
115.
116.
Atherosclerotic renal artery stenosis (ARAS) may cause hypertension, progressive renal failure, and recurrent pulmonary edema. It typically occurs in high risk patients with coexistent vascular disease elsewhere. Most patients with ARAS are likely to die from coronary heart disease or stroke before end-stage renal failure occurs. Recent controlled trials have shown that most patients undergoing angioplasty to treat renovascular hypertension still need antihypertensive agents 6 or 12 months after the procedure. Nevertheless, the number of antihypertensive agents required to control blood pressure adequately is lower following angioplasty than for medication alone. Trials assessing the value of revascularization for preserving renal function or preventing clinical events are only in the early recruitment phase. Revascularization should be undertaken in patients with ARAS and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or with an increase in plasma creatinine levels during angiotensin-converting enzyme inhibition. With or without revascularization, medical therapy using antihypertensive, hypolipidemic and antiplatelet agents is necessary in almost all cases.  相似文献   
117.
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   
118.
119.
120.
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   
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