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   2550066篇
  免费   197675篇
  国内免费   3870篇
耳鼻咽喉   34592篇
儿科学   84211篇
妇产科学   72220篇
基础医学   370118篇
口腔科学   74539篇
临床医学   232306篇
内科学   492711篇
皮肤病学   55180篇
神经病学   206160篇
特种医学   98644篇
外国民族医学   713篇
外科学   374807篇
综合类   59468篇
现状与发展   5篇
一般理论   1060篇
预防医学   205346篇
眼科学   58357篇
药学   190781篇
  10篇
中国医学   4481篇
肿瘤学   135902篇
  2018年   25217篇
  2016年   21623篇
  2015年   25055篇
  2014年   34551篇
  2013年   53069篇
  2012年   71741篇
  2011年   76223篇
  2010年   44685篇
  2009年   42883篇
  2008年   72396篇
  2007年   76911篇
  2006年   77243篇
  2005年   75299篇
  2004年   73488篇
  2003年   70427篇
  2002年   68587篇
  2001年   113897篇
  2000年   117237篇
  1999年   99579篇
  1998年   27904篇
  1997年   25386篇
  1996年   25664篇
  1995年   24725篇
  1994年   23119篇
  1993年   21777篇
  1992年   81538篇
  1991年   79634篇
  1990年   77688篇
  1989年   75246篇
  1988年   69828篇
  1987年   68721篇
  1986年   65603篇
  1985年   62982篇
  1984年   47510篇
  1983年   41401篇
  1982年   24470篇
  1981年   22059篇
  1980年   20784篇
  1979年   45467篇
  1978年   32304篇
  1977年   27220篇
  1976年   25555篇
  1975年   27175篇
  1974年   33138篇
  1973年   32204篇
  1972年   29949篇
  1971年   28101篇
  1970年   26122篇
  1969年   24743篇
  1968年   22722篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Over 100 mutations in the presenilin‐1 gene (PSEN1) have been shown to result in familial early onset Alzheimer disease (EOAD), but only a relatively few give rise to plaques with an appearance like cotton wool (CWP) and/or spastic paraparesis (SP). A family with EOAD, seizures and CWP was investigated by neuropathological study and DNA sequencing of the PSEN1 gene. Aβ was identified in leptomeningeal vessels and in cerebral plaques. A single point mutation, p.L420R (g.1508T > G) that gives rise to a missense mutation in the eighth transmembrane (TM8) domain of PS1 was identified in two affected members of the family. p.L420R (g.1508T > G) is the mutation responsible for EOAD, seizures and CWP without SP in this family.  相似文献   
82.
OBJECTIVE: To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life. METHODS: This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers. RESULTS: In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted. CONCLUSIONS: RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.  相似文献   
83.
84.
BACKGROUND CONTEXT: Substantial variation exists regarding the use of sedation before interventional spine techniques. Patient preference should play an important role in decision making regarding the need for sedation. However, little is known about patients' anxiety levels before spinal injections and their perceptions about the necessity of sedation. PURPOSE: To determine patient perception for need for sedation before epidural steroid injections and zygapophyseal joint injections. STUDY DESIGN/SETTING: Survey of consecutive spinal injection patients in an outpatient spine center. PATIENT SAMPLE: 500 consecutive lumbar, thoracic, and cervical patients receiving spinal injections. OUTCOME MEASURES: A 12-item questionnaire assessing patients' perceived anxiety before to a spinal injection. METHODS: Subjects were given the questionnaire after their spinal injection. Percentages requesting sedation for a first and potential second procedure were assessed. Additionally, anxiety level and pain rating, location of injection, age, sex, and other medication use were analyzed to determine the effect on the request for sedation. RESULTS: 17% of patients questioned requested sedation before an injection, and 28% would request sedation if they were to have a second injection. CONCLUSIONS: Routine sedation before diagnostic and therapeutic injections is not necessary as the majority of patients would not request sedation before the procedure when given the option. However, in some patients sedation is indicated, and all patients would benefit from educational material on sedation before the injection.  相似文献   
85.
86.
INTRODUCTION: Autoimmune hepatitis (AIH) is a well-defined entity in the West but there are sparse Indian data on this disease. AIM: To study the clinical profile and response to treatment of Indian patients with AIH. METHODS: This is a part retrospective and part prospective study of 50 patients (median age 48 years, range 11-82; 43 women) seen between 1995 to 2001, diagnosed to have AIH as per the revised scoring system. Clinical and laboratory profile, response to treatment, and complications of treatment were analyzed. RESULTS: AIH accounted for 6% of all patients with liver disease seen during the period. The presenting symptoms were gastrointestinal in 43 and non-gastrointestinal in 7, with median symptom duration of 6 months (range 2 weeks to 40 years). Forty patients (80%) had chronic liver disease. Associated illnesses were present in 28 patients. Twenty-six patients were classified as definite and the rest as probable AIH. Forty-nine patients had Type 1 AIH. Five patients had overlap syndrome. Forty-five patients (90%) received immunosuppressive therapy. Twelve of 18 patients receiving only prednisolone and 21 of 27 patients receiving prednisolone and azathioprine combination responded. Thirteen (26%) patients had therapy-related complications (infectious 5, non infectious 8) with two treatment-related deaths. CONCLUSION: Type 1 AIH was the predominant type of AIH. The majority of patients with AIH presented with chronic liver disease. There was good response to immunosuppressive therapy. Therapy-related complications occurred in one-fourth of patients.  相似文献   
87.
灾难的时代错误:灾害医学的过去、现在和将来(一)   总被引:1,自引:0,他引:1  
灾难,特别是地震、火山、洪水以及与战争有关的事件如饥饿和流行性传染病,是人类有记录的经历的一部分。从意大利庞贝的火山爆发,到约翰斯顿的洪水、第二次世界大战和黑色瘟疫,到西班牙流感,都发生了灾难,这不会被传说和历史书籍长期忘却。不过,在20世纪中叶以前,那些灾难的发生相对较少,且相距时间较长。从20世纪中叶以来,灾难的本质发生了变化。从恐怖分子使用“新技术”,到与气候有关的导致亿万美元经济损失的事件,表明这个世界正在发生变化。仅仅在最近的50~60年间,造成多种多样的伤亡事件,其危险性和频率的增加引人注目,并且注定要在接…  相似文献   
88.
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   
89.
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   
90.
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