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   238089篇
  免费   277002篇
  国内免费   36609篇
耳鼻咽喉   2358篇
儿科学   4021篇
妇产科学   2096篇
基础医学   87239篇
口腔科学   2206篇
临床医学   57715篇
内科学   92107篇
皮肤病学   4586篇
神经病学   21558篇
特种医学   8436篇
外科学   40211篇
综合类   51660篇
一般理论   2篇
预防医学   41063篇
眼科学   18262篇
药学   57624篇
  3篇
中国医学   46668篇
肿瘤学   13885篇
  2020年   5832篇
  2019年   13090篇
  2018年   13594篇
  2017年   14296篇
  2016年   12859篇
  2015年   12683篇
  2014年   12383篇
  2013年   12235篇
  2012年   12006篇
  2011年   13578篇
  2010年   16454篇
  2009年   24312篇
  2008年   11669篇
  2007年   8152篇
  2006年   7643篇
  2005年   7613篇
  2004年   9692篇
  2003年   8951篇
  2002年   9240篇
  2001年   11202篇
  2000年   6769篇
  1999年   12046篇
  1998年   13619篇
  1997年   13546篇
  1996年   14612篇
  1995年   14854篇
  1994年   14620篇
  1993年   13405篇
  1992年   12662篇
  1991年   12068篇
  1990年   11047篇
  1989年   10909篇
  1988年   10480篇
  1987年   9833篇
  1986年   9364篇
  1985年   8443篇
  1984年   6530篇
  1983年   6545篇
  1982年   7600篇
  1981年   7141篇
  1980年   6807篇
  1979年   6639篇
  1978年   5817篇
  1977年   6122篇
  1976年   5743篇
  1975年   5482篇
  1974年   5034篇
  1973年   4756篇
  1972年   4755篇
  1971年   4095篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The value of ultrasound in the diagnosis of a large rapidly growing thyroid mass was assessed in a study of 42 patients with a large (> 3 cm) rapidly growing (< two months) solitary mass. Haemorrhage into a thyroid nodule was present in 31 patients and thyroid malignancy in 11. Ultrasound of haemorrhage into a thyroid nodule revealed a large cystic mass in all 31 patients containing internal debris (22), septations (three), or a combination of both (six). The malignant causes of a large rapidly growing mass were lymphoma (two), anaplastic carcinoma (four) and metastasis (five). Ultrasound of these thyroid malignancies revealed a mass with a smooth, well-defined margin and strikingly low homogeneous echogenicity in all cases. Patients with thyroid metastases had evidence of widespread metastatic disease elsewhere. Lymphoma was differentiated from anaplastic carcinoma on fine-needle aspiration cytology or surgical biopsy. Ultrasound was of value in differentiating between a benign haemorrhagic nodule and a malignant tumour. The various malignant tumours had similar appearances, however, and could not be distinguished on ultrasound.  相似文献   
93.
94.
95.
OBJECTIVE: To describe Ontario emergency physicians' knowledge of colleagues' sexual involvement with patients and former patients, their own personal experience of such involvement, and their attitudes toward postvisit relationships. DESIGN: Mailed survey. SETTING: Ontario. PARTICIPANTS: Emergency physicians practising in Ontario. RESULTS: Of 974 eligible mailed surveys, 599 (61.5%) were returned. Of these respondents, 52 (8.7%) reported being aware of a colleague in emergency practice who had been sexually involved with a patient or former patient. When describing their own behaviour, 37 respondents (6.2%) reported sexual involvement with a former patient. However, of this group, only 9 (25.0%) had met the patient in an emergency department. Thus, of the total number of respondents, only 1.5% (9/599) reported sexual involvement arising out of an emergency department visit. Most respondents (82.4%) agreed that it is inappropriate behaviour to ask a patient for a date after an emergency assessment and before the patient's departure, and 66.4% felt that it is inappropriate to contact the patient after discharge. However, only 10.6% believed it to be unacceptable to request a social meeting after encountering a patient previously cared for in the emergency department in a nonprofessional setting. Most respondents (96.5%) did not believe that sexual involvement could ever be therapeutic for the patient. However, only 66% felt that it was always an abuse of power and 62.4% supported zero tolerance of all sexual involvement between physicians and patients. CONCLUSIONS: Vague regulatory guidelines currently in place have failed to dispel confusion regarding what is acceptable social behaviour for physicians providing emergency care. Our results support the need for clarification, and suggest a basis for guidelines that would be acceptable to the emergency medical community: that an emergency visit should not form the basis for the initiation of personal or sexual relationships, yet neither should it preclude their development in nonmedical settings.  相似文献   
96.
The relationship between day-to-day changes in asthma severity and combined exposures to community air pollutants and aeroallergens remains to be clearly defined. We examined the effects of outdoor air pollutants, fungi, and pollen on asthma. Twenty-two asthmatics ages 9-46 years were followed for 8 weeks (9 May-3 July 1994) in a semirural Southern California community around the air inversion base elevation (1,200 ft). Daily diary responses included asthma symptom severity (6 levels), morning and evening peak expiratory flow rates (PEFR), and as-needed beta-agonist inhaler use. Exposures included 24-hr outdoor concentrations of fungi, pollen, and particulate matter with a diameter < 10 microns (PM10; maximum = 51 micrograms/m3) and 12-hour day-time personal ozone (O3) measurements (90th percentile = 38 ppb). Random effects longitudinal regression models controlled for autocorrelation and weather. Higher temperatures were strongly protective, probably due to air conditioning use and diminished indoor allergens during hot, dry periods. Controlling for weather, total fungal spore concentrations were associated with all outcomes: per minimum to 90th percentile increase of nearly 4,000 spores/m3, asthma symptom scores increased 0.36 (95% CI, 0.16-0.56), inhaler use increased 0.33 puffs (95% CI, -0.02-0.69), and evening PEFR decreased 12.1 l/min (95% CI, -1.8-22.3). These associations were greatly enhanced by examining certain fungal types (e.g., Alternaria, basidiospores, and hyphal fragments) and stratifying on 16 asthmatics allergic to tested deuteromycete fungi. There were no significant associations to low levels of pollen or O3, but inhaler use was associated with PM10 (0.15 inhaler puffs/10 micrograms/m3; p < 0.02). These findings suggest that exposure to fungal spores can adversely effect the daily respiratory status of some asthmatics.  相似文献   
97.
Yersinia enterocolitica is a rare cause of extra-intestinal disease. A case in a 60 year old butcher with hepatic cirrhosis who developed suppurative arthritis of the shoulder caused by Y enterocolitica is presented. There was no evidence of gastrointestinal infection or septicaemia. The severity of the illness was associated with various factors, including the underlying disease, the type of occupation, and the difficulties encountered in defining the optimal therapeutic regimen.  相似文献   
98.
99.
C P Choudari  C Rajgopal    K R Palmer 《Gut》1994,35(4):464-466
The underlying diagnosis and clinical course of 52 patients who presented with severe acute gastrointestinal haemorrhage while taking the anticoagulant warfarin is reviewed. A bleeding site was identified in 83% of cases, only slightly fewer than the 92% found in a control of group of 710 patients not taking warfarin who presented in the same four year period. The degree or duration of anticoagulation was unrelated to the frequency of establishing a diagnosis. The commonest diagnosis was peptic ulcer (25 cases) and endoscopic treatment by injection or heater probe was attempted in 23 of these. The outcome in this subgroup was compared with that in 50 closely matched control subjects who had similar risk factors for rebleeding from peptic ulcer. Permanent haemostasis was achieved in (91%) of the anticoagulated and in 92% of the control patients. There were no complications related to endoscopy. Patients who present with acute gastrointestinal haemorrhage while taking warfarin usually bleed from mucosal disease. They should be endoscoped after resuscitation and those with major bleeding from a peptic ulcer should be offered endoscopic treatment.  相似文献   
100.
Parathyroid hormone-related peptide (PTHrP) was initially discovered as the cause of the syndrome of humoral hypercalcemia of malignancy. Subsequently, the PTHrP gene has been shown to be expressed in a wide variety of normal tissues, including skin. Because the biological function of PTHrP in skin remains unknown, we used the human keratin 14 promoter to target overexpression of PTHrP to the skin of transgenic mice. We achieved a 10-fold level of overexpression in skin, and human keratin 14 promoter-PTHrP transgenic mice displayed a disturbance in normal hair follicle development. These mice either failed to initiate follicle development or showed a delay in the initiation of follicles. These findings suggest that PTHrP normally plays a role in the early stages of hair follicle development and support previous speculation that the peptide may function in regulating cellular differentiation.  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