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   30168篇
  免费   2417篇
  国内免费   61篇
耳鼻咽喉   199篇
儿科学   924篇
妇产科学   803篇
基础医学   3998篇
口腔科学   540篇
临床医学   3624篇
内科学   5347篇
皮肤病学   410篇
神经病学   3066篇
特种医学   705篇
外科学   3291篇
综合类   564篇
一般理论   89篇
预防医学   4157篇
眼科学   302篇
药学   1860篇
中国医学   20篇
肿瘤学   2747篇
  2023年   314篇
  2022年   422篇
  2021年   1057篇
  2020年   661篇
  2019年   1036篇
  2018年   1047篇
  2017年   797篇
  2016年   859篇
  2015年   879篇
  2014年   1184篇
  2013年   1612篇
  2012年   2461篇
  2011年   2412篇
  2010年   1271篇
  2009年   1032篇
  2008年   1863篇
  2007年   1762篇
  2006年   1736篇
  2005年   1604篇
  2004年   1470篇
  2003年   1223篇
  2002年   1090篇
  2001年   366篇
  2000年   375篇
  1999年   369篇
  1998年   264篇
  1997年   176篇
  1996年   142篇
  1995年   139篇
  1994年   123篇
  1993年   106篇
  1992年   249篇
  1991年   212篇
  1990年   187篇
  1989年   164篇
  1988年   143篇
  1987年   168篇
  1986年   149篇
  1985年   159篇
  1984年   108篇
  1983年   111篇
  1982年   76篇
  1981年   90篇
  1980年   55篇
  1979年   80篇
  1978年   82篇
  1977年   56篇
  1974年   69篇
  1972年   61篇
  1971年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
M Miros  P Kerlin  N Walker  J Harper  S Lynch    R Strong 《Gut》1991,32(11):1369-1373
Patients with primary sclerosing cholangitis are at an increased risk of developing cholangiocarcinoma, which is difficult to diagnose because the biliary tree is already distorted. Eleven patients with primary sclerosing cholangitis who underwent orthotopic liver transplantation at this hospital were evaluated. Four patients had coincidental histologically proved cholangiocarcinoma. Patients with cholangiocarcinoma in contrast to patients without tumour presented with rapid onset of persistent jaundice, pruritus, and weight loss associated with an appreciable rise in bilirubin (8x v 2x) and alkaline phosphatase (3.5x v 1.2x) over one year. Cholangiography and computed tomography showed appreciably dilated intrahepatic bile ducts (3/4 v 0/7). The diagnosis of cholangiocarcinoma could only be established before operation in one patient by fine needle aspiration cytology. Tumour was recognised at operation in one other. Histological examination of hepatectomy specimens showed that patients with cholangiocarcinoma had less advanced histological features of primary sclerosing cholangitis. Multiple areas of carcinoembryonic antigen positive epithelial atypia and carcinoma in situ were found in all patients with cholangiocarcinoma. Cholangiocarcinoma recurred in two patients at 14 and 39 months after transplantation. Superimposed cholangiocarcinoma can be predicted in most patients with cholangitis before transplantation, although a definitive diagnosis is difficult to make. Their prognosis after successful transplantation is guarded.  相似文献   
122.
Sir, The expansion of haemodialysis includes older patients withcomorbidities, poor quality vessels, unsuitable for transplantationor peritoneal dialysis. Vascular access complications accountfor 20% of hospital admissions [1]. With exhausted sites inupper extremities, unusual sites for arteriovenous grafts formationare used [2]. The  相似文献   
123.
124.
This article describes the development of the Ethical Principles and Guidelines for Family Scientists that the National Council on Family Relations Board of Directors unanimously approved. Furthermore, it discusses the importance of ethics education for family professionals and provides suggestions for educators. Finally, the ethical principles and guidelines are delineated. We argue that the development of a scholarship on ethics education is important for current and future family scientists.  相似文献   
125.
126.
Lynch  DA; Gamsu  G; Ray  CS; Aberle  DR 《Radiology》1988,169(3):603-607
In 260 asbestos-exposed individuals evaluated by means of computed tomography (CT), 43 unsuspected pulmonary masses were found in 27 individuals. The masses included fissural pleural plaques (n = 10), dense fibrotic bands (n = 3), round atelectasis (n = 11), carcinomas (n = 3), and other presumed benign masses (n = 16). The most helpful features in the diagnosis of rounded atelectasis with CT were (a) contiguity to areas of diffuse pleural thickening, (b) a lentiform or wedge-shaped outline, (c) evidence of volume loss in the adjacent lung, and (d) a characteristic "comet tail" of vessels and bronchi sweeping into the margins of the mass. Less advanced areas of focal atelectasis had fewer classic features. Intrafissural pleural plaques were readily identified with high-resolution CT. In asbestos-related masses, the demonstration of stability over time is necessary. Careful interpretation of CT and high-resolution CT features and close surveillance can obviate the need for biopsy in the majority of instances.  相似文献   
127.
Flat adenomas in a colon cancer-prone kindred   总被引:9,自引:0,他引:9  
We describe new pathologic findings in a hereditary nonpolyposis colorectal cancer family. Affected family members developed multiple small adenomas with right-sided predominance; many adenomas had an unusual appearance featuring slightly elevated lesions with adenomatous changes confined to the upper regions of the colonic crypts. We have adopted the previously established term "flat adenoma" for these lesions. This phenotype may be a morphologic marker for at least one subset of hereditary nonpolyposis colorectal cancer.  相似文献   
128.
Environmental education   总被引:2,自引:2,他引:0       下载免费PDF全文
The need for a new profession devoted to environmental matters is asserted. The qualities of such a profession are sketched, and it is argued that new initiatives in environmental education are needed in the form of graduate, professional programs with primary emphasis on practice. An example 2-year program is presented. A fundamental requirement is scientific competence; undergraduate preparation in the sciences or engineering is mandatory. The graduate curriculum itself is built on three primary cores: environmental science and engineering, business and management, and public policy. Additionally, an environmental round table is proposed as a focal point for academic, industrial, governmental, and public discussion on environmental matters. The round table would provide oversight for the professional educational program and an affiliated research institute.  相似文献   
129.
Many youth, their parents, and social services regard the unification of the family as the most desirable outcome for youth in out-of-home placements. This goal is often difficult to achieve because the families of these troubled/troubling youths are often severely dysfunctional, with multiple problems. A group process model for serving natural parents of youth in placement is described which, in conjunction with one-on-one interactions with professionals, appears to have a positive impact on these families and on youths' return home. Group components that seem particularly important are described, including attendance by invitation only, public commitment to attend and participate, reminder prompts, transportation support, babysitting support, refreshments, opportunity to visit with their child, defined staff roles, an empowering approach, and starting where the parent is. The group process maintained a relatively high level of both attendance and participation by the targeted parents. Participants tended to achieve most goals that they set in the group. Our experience indicates that interventions with natural parents of troubled youth can enable even a very dysfunctional family to improve enough to receive youth back into their home.The authors are grateful for the assistance of Sharon Estill, Jim Bernardo, Anita Mentzer, Dave Walker, and Suni Dague-Lyman for assistance in collecting the data reported here. Debbie Buchanan and others have been a great assistance in transporting families.  相似文献   
130.
The effects of milrinone and pimobendan upon the initiation of programmed ventricular stimulation-induced ventricular tachycardia (VT) and the incidence of lethal ischemic ventricular arrhythmias were assessed in conscious dogs with recent anterior myocardial infarctions. Based upon the results of previous studies, the animals which were entered into this investigation were nonresponsive to baseline programmed stimulation and, therefore, considered to be at "low risk" toward the development of subsequent lethal ischemic arrhythmias. Milrinone (200 micrograms/kg/h continuous i.v. infusion) and pimobendan (300 micrograms/kg i.v.) were administered in dosing regimens shown to produce equivalent and sustained increases in left ventricular (LV) + dP/dt. At the time of repeat electrophysiologic testing, 9 of 9 pimobendan-, 9 of 10 milrinone-, and 12 of 12 concurrent vehicle-treated animals remained nonresponsive to programmed ventricular stimulation. Compared to a total control population of 39 "low risk" postinfarction dogs; however, both milrinone and pimobendan administration increased the incidence of sudden ventricular fibrillation occurring in response to the development of acute posterolateral ischemia (milrinone 4 of 10 [40%] and pimobendan 4 of 10 [40%] versus "low risk" control population 4 of 39 [10.3%]; p = 0.038). The incidence of ischemic mortality at 24 h after the development of posterolateral myocardial ischemia was increased in the milrinone-treated group (6 of 10 [60%]) compared to the "low risk" control population (6 of 39 [15.2%]; p = 0.007), whereas the incidence of 24-h ischemic mortality in the pimobendan-treated group (4 of 10 [40%]) was only of borderline statistical significance when compared to that of the "low risk" control population (p = 0.083). Milrinone, but not pimobendan, delayed the onset of acute posterolateral myocardial ischemia in the postinfarction dogs. The predominant electrophysiologic effects of both milrinone and pimobendan were decreases in ventricular refractoriness in both non-infarct (NZ) and in infarct zones (IZ), as well as reductions in electrocardiographic QTc or QT intervals. These findings suggest that with both positive inotropic agents, including milrinone which may possess protective antithrombotic action, sudden death may be increased via a reduction in ventricular refractoriness in the ischemically injured heart. The enhanced susceptibility toward the development of ischemic ventricular arrhythmias in the presence of the inotropic interventions is not predicted by programmed ventricular stimulation testing prior to the ischemic event.  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