全文获取类型
收费全文 | 2720850篇 |
免费 | 198266篇 |
国内免费 | 7951篇 |
专业分类
耳鼻咽喉 | 36237篇 |
儿科学 | 89182篇 |
妇产科学 | 74361篇 |
基础医学 | 381694篇 |
口腔科学 | 72729篇 |
临床医学 | 248259篇 |
内科学 | 543925篇 |
皮肤病学 | 64668篇 |
神经病学 | 227562篇 |
特种医学 | 104486篇 |
外国民族医学 | 754篇 |
外科学 | 406068篇 |
综合类 | 52244篇 |
现状与发展 | 8篇 |
一般理论 | 1118篇 |
预防医学 | 206804篇 |
眼科学 | 60533篇 |
药学 | 197245篇 |
8篇 | |
中国医学 | 5496篇 |
肿瘤学 | 153686篇 |
出版年
2021年 | 22139篇 |
2019年 | 22754篇 |
2018年 | 31794篇 |
2017年 | 24419篇 |
2016年 | 28258篇 |
2015年 | 32018篇 |
2014年 | 44193篇 |
2013年 | 66510篇 |
2012年 | 88597篇 |
2011年 | 93617篇 |
2010年 | 56184篇 |
2009年 | 53906篇 |
2008年 | 87734篇 |
2007年 | 93210篇 |
2006年 | 94576篇 |
2005年 | 91129篇 |
2004年 | 87740篇 |
2003年 | 84608篇 |
2002年 | 81511篇 |
2001年 | 129702篇 |
2000年 | 132291篇 |
1999年 | 111794篇 |
1998年 | 33048篇 |
1997年 | 29449篇 |
1996年 | 29515篇 |
1995年 | 28527篇 |
1994年 | 26156篇 |
1993年 | 24443篇 |
1992年 | 86017篇 |
1991年 | 82355篇 |
1990年 | 79492篇 |
1989年 | 76775篇 |
1988年 | 70140篇 |
1987年 | 68569篇 |
1986年 | 64224篇 |
1985年 | 61255篇 |
1984年 | 45919篇 |
1983年 | 38871篇 |
1982年 | 23704篇 |
1981年 | 21186篇 |
1979年 | 39681篇 |
1978年 | 28190篇 |
1977年 | 23917篇 |
1976年 | 22098篇 |
1975年 | 23354篇 |
1974年 | 27331篇 |
1973年 | 25829篇 |
1972年 | 24130篇 |
1971年 | 22236篇 |
1970年 | 20432篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jorge Guardado Carlos Cotrim Otília Sim?es Sofia Almeida Mário Ialá Luís Lopes Hélder Pereira Manuel Carrageta 《Revista portuguesa de cardiologia》2006,25(4):409-415
INTRODUCTION: Transesophageal echocardiography (TEE) has become increasingly useful in the study of patients with suspected pulmonary thromboembolism. OBJECTIVE: The aim of this study was to prospectively evaluate the usefulness of TEE in the study of the distal part of the left pulmonary artery (LPA) as well as the influence of this procedure on total echocardiographic exam duration. METHODOLOGY: A prospective study in two groups of consecutive patients referred for TEE with a one- year interval between evaluation of Group A: 33 patients, 17 male, mean age 54 +/- 24 years, and Group B: 42 patients, 20 male, mean age 48 +/- 27 years (p = NS). The procedure was considered long when it took more than 3 min to evaluate the distal part of the LPA. RESULTS: In group A we were able to visualize the distal part of the LPA in 24 patients (73%) without significant prolongation of total exam duration in 16 patients (48% of group A). In one of the patients with suspected pulmonary thromboembolism thrombi were only observed in the distal part of the LPA. In group B we were able to visualize the distal part of the LPA in 36 patients (86%) without significant prolongation of total exam duration in 26 patients (61% of group B). CONCLUSIONS: 1. Visualization of the distal part of the LPA was possible in more patients, and with TEE time prolongation in less patients, in group B. These differences can be accounted for by the training of the operator in this technique. 2. The importance of visualization of this part of the LPA in guiding treatment in the subset of patients with pulmonary thromboembolism confirms the usefulness of this specific procedure. 相似文献
992.
993.
994.
995.
996.
997.
P V Fragola C Autore G Ruscitti A Picelli M Borzi D Cannata M Sangiorgi 《Giornale italiano di cardiologia》1988,18(1):52-54
Eighty-nine first-degree relatives of 22 patients with an established diagnosis of hypertrophic cardiomyopathy underwent electrocardiographic and echocardiographic screening. Scalar electrocardiogram was abnormal in 30/89 (33.7%) relatives. Of these thirty, eleven had definite evidence of hypertrophic cardiomyopathy at echo; one had borderline hypertrophy and was considered neither affected nor unaffected; four had questionable signs of hypertrophy. The remaining 14 relatives had normal echo-cardiograms. Fifty-nine relatives (66.3%) had normal electrocardiograms; at echo 3 were considered to have borderline hypertrophy, 16 had questionable signs of hypertrophy and 40 were normal. In relatives of patients with hypertrophic cardiomyopathy an abnormal electrocardiogram may reflect different morphologic conditions: a real hypertrophic cardiomyopathy or a myocardial hypertrophy of uncertain significance. Furthermore, in these categories of subjects, an abnormal electrocardiogram with normal echo must be considered with caution. 相似文献
998.
Biological activity of partially purified digitalis-like substance and Na-K-ATPase inhibitor in rats
T Morise S Okamoto H Takasaki M Ikeda R Takeda F Kiuti Y Tuda 《Japanese circulation journal》1988,52(11):1309-1316
In order to study the biological activity of endogenous digitalis-like substance (DLS) and Na-K-ATPase inhibitor (ATPI), human urine was partially purified and administered to rats, and its effects on the urinary volume, urinary Na excretion and blood pressure (BP) were determined. In addition, the effect on myocardial Na-K-ATPase activity was also measured. After the extraction of 40L of urine with a reversed phase cartridge column (S-fraction), 20 ml of chloroform was added and extraction was repeated. The chloroform layer was applied to an open silica gel column, and at a fraction with ethylacetate: methanol (60: 40, T-1 fraction), DLS and ATPI were eluted at the highest concentration. The water layer was treated with charcoal (D-1 fraction). The acute administration of K-1, T-1 fraction to rats in vivo caused significant rises in urinary volume, urinary Na excretion and BP. In chronic administration of K-1 fraction, urinary Na excretion was significantly elevated and myocardial Na-K-ATPase activity was also significantly suppressed. These results suggest that DLS and ATPI cause increase in the urinary volume and urinary Na excretion and also possess a hypertensive action; and moreover, these substance may affect the heart like cardiotonic steroids and regulate BP by increasing cardiac contractility. 相似文献
999.
Gil Bolotin Frederik H. van der Veen Roberto Lorusso Tamir Wolf Robert Sachner Rona Shofti Jan J. Shreuder Gideon Uretzky 《European journal of cardio-thoracic surgery》2002,21(6):975-980
Objective: Descending and ascending aortomyoplasty are two surgical procedures intended to induce hemodynamic benefits similar to those of the intra-aortic-balloon-pump (IABP). To date, there have been no studies comparing the two surgical techniques. The objective of this study was to compare coronary blood flow augmentation and afterload reduction as produced by descending and ascending aortomyoplasty counterpulsation Methods: Twenty-two mongrel dogs (18–35 kg) underwent IABP application (n=7), descending (n=8), or ascending (n=7) aortomyoplasty. Left anterior descending (LAD) coronary artery blood flow was measured using a Transonic Doppler flow probe. Left ventricular pressure as well as aortic pressures proximal and distal to either the aortomyoplasty site or the IABP position were monitored continuously. Results: Descending aortomyoplasty induced higher elevation in the LAD blood flow during assisted beats (27% from 10.8±4 to 13.8±6 ml/min, P<0.001) than that induced by either ascending aortomyoplasty (19% from 11.7±5 to 14±5 ml/min, P<0.001) or IABP counterpulsation (18% from 8.6±3 to 10.2±4 ml/min, P<0.001). Conversely, while ascending aortomyoplasty reduced the left ventricular end-diastolic pressure by 16% (from 60±18 to 50±22 mmHg, P<0.001), similar to the 16% after load reduction achieved by the IABP counterpulsation, descending aortomyoplasty failed to induce afterload reduction. Conclusions: Descending aortomyoplasty produces higher coronary blood flow augmentation than either ascending aortomyoplasty or IABP. However, afterload reduction comparable to that achieved by IABP was observed only with ascending aortomyoplasty and not with descending aortomyoplasty. 相似文献
1000.
We present evidence to show that monoclonal antibodies to estrogen receptors (ER) in solid phase recognize the secondary estrogen binding sites with moderate to low affinity for estradiol (E2). An excellent quantitative agreement was found in five cytosols between the ER values obtained by the enzyme immunoassay (ER-EIA) and the amount of secondary estrogen binding sites measured by the assay involving dextran-coated charcoal (Clin Chem 1986;32:1496). The immunoreactive protein recognized by the antibody-coated beads, when allowed to react with ER(+) cytosols, is shown to bind [3H]estradiol only when the ligand concentration exceeds 8 nmol/L. Further biochemical and functional characterization of the immunoreactive protein is required to establish similarities/dissimilarities between this protein, high-affinity Type I ER sites, and the secondary sites such as Type II sites. 相似文献