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   7949篇
  免费   661篇
  国内免费   120篇
耳鼻咽喉   36篇
儿科学   196篇
妇产科学   127篇
基础医学   877篇
口腔科学   218篇
临床医学   833篇
内科学   2117篇
皮肤病学   181篇
神经病学   794篇
特种医学   329篇
外科学   1058篇
综合类   169篇
一般理论   28篇
预防医学   658篇
眼科学   282篇
药学   478篇
中国医学   21篇
肿瘤学   328篇
  2023年   53篇
  2022年   61篇
  2021年   132篇
  2020年   93篇
  2019年   156篇
  2018年   177篇
  2017年   147篇
  2016年   124篇
  2015年   140篇
  2014年   170篇
  2013年   286篇
  2012年   363篇
  2011年   423篇
  2010年   257篇
  2009年   208篇
  2008年   365篇
  2007年   423篇
  2006年   402篇
  2005年   373篇
  2004年   302篇
  2003年   336篇
  2002年   258篇
  2001年   181篇
  2000年   192篇
  1999年   180篇
  1998年   115篇
  1997年   93篇
  1996年   93篇
  1995年   85篇
  1994年   85篇
  1993年   62篇
  1992年   170篇
  1991年   139篇
  1990年   136篇
  1989年   143篇
  1988年   143篇
  1987年   150篇
  1986年   140篇
  1985年   120篇
  1984年   106篇
  1983年   64篇
  1979年   91篇
  1978年   78篇
  1977年   62篇
  1976年   55篇
  1975年   52篇
  1974年   69篇
  1973年   61篇
  1972年   62篇
  1971年   60篇
排序方式: 共有8730条查询结果,搜索用时 15 毫秒
1.
Despite a population of nearly 60 million, there is currently not a single interventional radiologist in Tanzania. Based on an Interventional Radiology (IR) Readiness Assessment, the key obstacles to establishing IR in Tanzania are the lack of training opportunities and limited availability of disposable equipment. An IR training program was designed and initiated, which relies on US-based volunteer teams of IR physicians, nurses, and technologists to locally train radiology residents, nurses, and technologists. Preliminary results support this strategy for addressing the lack of training opportunities and provide a model for introducing IR to other resource-limited settings.  相似文献   
2.

Background

The purpose of this analysis is to describe the differences in cardiac magnetic resonance characteristics between benign and malignant tumors, which would be helpful for surgical planning.

Methods

This was a prospective cohort study of 130 patients who underwent cardiac magnetic resonance imaging for evaluation of a suspected cardiac mass. After excluding thrombi and tumors without definitive diagnosis, 66 tumors were evaluated for morphologic features and tissue composition.

Results

Of the 66 patients, 39 (59.0%) had malignant tumors and 27 (41.0%) had benign tumors. Patients with malignant tumors were younger when compared with those with benign tumors (age 51 years [42.8-60.0] vs 65 years [60.0-71.0] median). Malignant tumors more often demonstrated tumor invasion (69% vs 0% P < .001) and were more often associated with pericardial effusion (41% vs 7.4% P = .004). Presence of first-pass perfusion (100% vs 33% P < .001) and late gadolinium enhancement (100% vs 59.2%, P < .001) were significantly higher in malignant tumors. In logistic regression modeling, tumor invasion (P < .001) and first-pass perfusion (P < .001) were independently associated with malignancy. Furthermore, using classification and regression tree analysis, we developed a decision tree algorithm to help differentiate benign from malignant tumors (diagnostic accuracy ~90%). The algorithm-weighted cost of misclassifying a malignant tumor as benign was twice that of classifying a benign tumor as malignant.

Conclusions

Our study demonstrates that cardiac magnetic resonance imaging is a useful noninvasive method for differentiating malignant from benign cardiac tumors. Tumor size, invasion, and first-pass perfusion were useful imaging characteristics in differentiating benign from malignant tumors.  相似文献   
3.
4.
Various cases are presented demonstrating the role of computed tomography (CT) in the assessment of serosal and bowel wall pathology. Reference is made to the morphology of the lesions. Illustrative examples of tumors, secondary malignant dissemination, irradiation injury to the gut, and intramural gas associated with ulcerative colitis, are all illustrated.  相似文献   
5.
It was hypothesized that members of an older cohort of seriously mentally ill community mental health clients would develop stronger alliances with intensive case managers. Eighty-six clients participating in a study of case management services completed a measure of working alliance and structured interviews. It was found that older cohort clients, those age 45 or older, showed much stronger alliances with their case managers than younger clients.This research is funded by NIMH/SAMHSA grant R18MH46082.  相似文献   
6.
The optimum therapy for cryptococcal meningitis in patients with the acquired immunodeficiency syndrome (AIDS) remains unresolved. Traditional therapy consists of amphotericin B with or without flucytosine. Obstacles exist in administering these agents to patients with AIDS. Mortality rates during initial therapy are relatively high. Given the lack of proved benefit, we do not recommend adding flucytosine to amphotericin B routinely. The search for more efficacious and less toxic agents continues. The oral triazoles, especially fluconazole, have increased the options for treatment of this disease. New strategies and novel approaches in managing cryptococcal meningitis in patients with AIDS continue to be developed.  相似文献   
7.
1. The present study aimed to determine the feasibility of conducting a 5 year cardiovascular outcome trial of the treatment of 6000 elderly hypertensive patients in Australian general practices. 2. General practitioners (GPs) were invited to participate by mail and personal follow-up. Patient records were reviewed to identify subjects for a blood pressure (BP) screening programme. Blood pressure was measured on three occasions and eligible subjects were included if the average BP was 160 mmHg systolic or 90 mmHg diastolic if systolic BP was 140 mmHg. 3. Seven hundred and forty-one GPs were approached and 89 were enrolled in the study (12% of mail invites and 75% of those receiving a personal contact). In 16 practices where screening was completed, 82 000 records were reviewed to identify 4% patients eligible for screening. Twenty-two per cent of eligible subjects attended screening. Of 1938 subjects screened, 180 (9%) had BP 5=160/90 mmHg. Forty-seven percent of subjects (n = 916) were receiving antihypertensive therapy and 184 (20%) were withdrawn from therapy. One hundred and sixteen (63%) of these subjects had BP return to study entry levels within 6 weeks. Fifty-seven newly diagnosed and 81 previously treated subjects were randomized (7% of the screened population). 4. Based on the high participation rate of GPs, the response rate of patients to attend a BP screening programme and the 7% randomization to screening ratio for entry into the study, the ANBP2 pilot study has demonstrated that it is feasible to recruit subjects from Australian general practices to a cardiovascular outcome trial.  相似文献   
8.
W L Young  I Prohovnik  E Ornstein  N Ostapkovich  M B Sisti  R A Solomon  B M Stein 《Neurosurgery》1990,27(2):257-66; discussion 266-7
To investigate the cerebral hemodynamic changes associated with obliteration of arteriovenous malformations (AVMs), we studied 26 patients undergoing total microsurgical AVM resection during isoflurane and N2/O2 anesthesia. Detectors were placed 5 to 6 cm from the margin of the lesion and in a homologous contralateral position. Cerebral blood flow (CBF) was measured using the intravenous xenon-133 technique before and after AVM resection, during both hypocapnia and normocapnia at each stage. Intraoperative changes in CBF were related to a risk score system based on the patient's history and preoperative angiograms. Seven otherwise healthy patients undergoing spinal surgery were studied to control for anesthetic effects. Patient demographic and clinical data for the AVM group conformed to the expected strata of a large AVM population. The CBF increased after excision (22 +/- 1 ml/100 g/min before excision to 30 +/- 2 ml/100 g/min after excision; mean +/- SE, n = 25, P less than 0.002) without a hemispheric difference. CO2 reactivity increased slightly after excision (4.2 +/- 0.3% change/mm Hg before excision to 4.7 +/- 0.3% change/mm Hg after excision; n = 14, P less than 0.02). The baseline CBF and CO2 reactivity were not different from the control group. There was a weak correlation between the risk score and the percentage of change in the ipsilateral CBF, with a trend for the patients with the lowest risk to have the lowest CBF changes after resection. There was no relationship between CO2 reactivity and risk grade. None of the patients awoke from anesthesia with unexpected neurological deficits. The highest CBF increases were associated with postoperative brain swelling in one patient and fatal intracerebral hemorrhage in another. Both patients had normal CO2 reactivity before excision. One patient suffered postoperative intracerebral hemorrhage, attributable to technical problems, and had no increase in CBF. We conclude that, with an acute increase in the arteriovenous pressure gradient (and cerebral perfusion pressure) that results from shunt obliteration, there is an immediate global effect of AVM resection to increase CBF. Cerebrovascular reactivity to CO2 remains intact both before and after excision.  相似文献   
9.
10.
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