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   1471篇
  免费   91篇
  国内免费   2篇
耳鼻咽喉   3篇
儿科学   22篇
妇产科学   15篇
基础医学   213篇
口腔科学   35篇
临床医学   110篇
内科学   291篇
皮肤病学   33篇
神经病学   280篇
特种医学   67篇
外科学   114篇
综合类   3篇
预防医学   51篇
眼科学   5篇
药学   130篇
肿瘤学   192篇
  2022年   12篇
  2021年   33篇
  2020年   19篇
  2019年   25篇
  2018年   26篇
  2017年   20篇
  2016年   28篇
  2015年   19篇
  2014年   48篇
  2013年   50篇
  2012年   88篇
  2011年   83篇
  2010年   37篇
  2009年   40篇
  2008年   76篇
  2007年   88篇
  2006年   57篇
  2005年   78篇
  2004年   62篇
  2003年   67篇
  2002年   47篇
  2001年   57篇
  2000年   54篇
  1999年   45篇
  1998年   17篇
  1997年   20篇
  1996年   17篇
  1995年   14篇
  1994年   14篇
  1993年   6篇
  1992年   29篇
  1991年   23篇
  1990年   22篇
  1989年   23篇
  1988年   21篇
  1987年   34篇
  1986年   17篇
  1985年   30篇
  1984年   13篇
  1983年   9篇
  1982年   9篇
  1981年   4篇
  1980年   8篇
  1979年   17篇
  1978年   9篇
  1977年   7篇
  1976年   7篇
  1975年   7篇
  1974年   8篇
  1972年   4篇
排序方式: 共有1564条查询结果,搜索用时 31 毫秒
1.
Background:Cardiovascular diseases (CVD), particularly the ischemic heart disease, are a growing public health issue. In addition, the return to work after an acute cardiovascular attack represents a complex challenge.Objectives:To evaluate utility and safety of cardiopulmonary exercise testing (CPET), particularly performed “on site”, to promote a return to work in line with the residual working capacity.Methods:Fifty-nine workers affected by a major cardiovascular event, aged 18-63 years, have been enrolled between 2015 and 2018. All the patients underwent a CPET in outpatient clinic. Eleven workers also underwent the “on site” CPET, recorded during their working activities.Results:Outpatient clinic CPET outcomes (i.e. normal, mild impairment or moderate/severe impairment of cardiopulmonary function) were associated with the subjective perception of workers’ health status after returning to work. The “on site” CPET was found to be safe and reliable to promote a personalized return to work of patients. In 7 out of 11 patients, the values of O2 consumption (VO2) during the working activity were higher than 40% of VO2 max as obtained from laboratory CPET.Conclusions:This study provides evidence for safety and usefulness of “on site” CPET for a personalized statement of fitness for work. This may facilitate the job retention of patients characterized by a high risk of unnecessary job loss. The use of CPET represents a first step of energy expenditure evaluation associated with specific working tasks.Key words: Acute coronary syndrome, cardiopulmonary exercise testing, return to work  相似文献   
2.
Amidines (guanidine, formamidine, and acetamidine) were introduced as substitutes for the cationic heads present in atropine, scopolamine, and corresponding quaternary derivatives. Amidine systems are intermediate in structure between tertiary amines and quaternary compounds, at least as regards ionization and electronic properties, but differ from the latter in shape (planar not tetrahedral). They have additional binding opportunities on account of their hydrogen-bond-forming capacity. The effect of the introduction of these cationic heads on the affinity for different muscarinic acetyl choline receptor (m-AcChR) subtypes was investigated in vitro, in binding displacement studies, and in functional tests on isolated organs. All new compounds (3a,b-5a,b) showed high affinity for the m-AcChR considered, comparable or slightly inferior to that of the parent drugs (1a-e). The new amidine derivatives proved effective as spasmolytic agents, with little tendency to cause central effects. However, no separation was achieved of spasmolytic and other untoward effects, like inhibition of salivation. Thus, amidine moieties are effective bioisosteric substitutes for conventional cationic heads present in antimuscarinic agents. Their unusual physical-chemical properties make them useful tools when modulation of pharmacokinetic or pharmacodynamic effects is required.  相似文献   
3.
Abstract: Breast conservation surgery is an effective and safe treatment for many breast carcinomas. It may be possible to further limit the extent of resection (or expand the indication for breast conservation) by the application of preoperative chemotherapy and radiotherapy. We explored the feasibility of this in a pilot study.
Seventy-three patients (mean age 48, 63% premenopausal) with confirmed breast cancer, less than 2.5 cm, received chemotherapy (Group A) or chemotherapy plus radiotherapy (Group B) prior to limited resection (tumorectomy). Axillary dissection was always performed. Results: In 6/31 (19%) Group A and 17/42 (40%) Group B patients the tumor was not palpable after preoperative treatment, with complete pathological remission in 1 and 3 cases respectively. Histologic grading, mitosis, cellular alteration, and cellularity evaluations indicated a consistently greater therapeutic effect with chemoradiotherapy than with chemotherapy alone.
In conclusion, radiotherapy appears useful in the preoperative treatment of breast cancer and its use in association with various drug combinations should be further explored.  相似文献   
4.
The aim of this study was to determine the diagnostic accuracy of technetium-99m tetrofosmin myocardial imaging for the localization of coronary artery stenoses of different degrees of severity. Stress-rest single-photon emission tomography (SPET) was performed on separate days in 80 patients (64 males, 16 females; mean age 61 years; 43 patients with previous myocardial infarction; 18 patients with pharmacological stress), within 6 months of coronary angiography. Scintigraphic images were blindly and independently evaluated by three observers. Coronary stenosis was defined as a >50% narrowing in luminal diameter; severe stenosis was defined as a proximal stenosis of >75% or a peripheral stenosis of >90%. Coronary angiography revealed normal coronary arteries or insignificant coronary stenosis in 13 patients and significant coronary stenoses in 67 patients. The sensitivity and specificity of 99mTc-tetrofosmin SPET in respect of severely stenosed vessels were, respectively, 80% and 65% for the left anterior descending artery (LAD), 100% and 46% for the right coronary artery (RCA) and 58 and 78% for the left circumflex artery (LCx) territories. Considering all the significantly stenosed vessels, a significant decrease in sensitivity was observed for LAD territories (to 59%, P=0.05), and a nonsignificant decrease for RCA (88%) and LCx (47%) territories while specificity values remained essentially unchanged. No significant changes in sensitivity or specificity were observed when regions with previous myocardial infarction were excluded. In conclusion, the sensitivity of 99mTc-tetrofosmin SPET for the localization of individual stenosed vessels is only moderate when all significant stenoses are considered, but the ability of this technique to predict the location of severe coronary artery stenoses seems satisfactory, with the exception of the low specificity in respect of RCA territories. Received 26 April and in revised form 7 June 1997  相似文献   
5.
Eighty-seven consecutive patients with metastatic breast cancer were treated with aminoglutethimide plus hydrocortisone. All patients were postmenopausal and had progressive disease following prior chemotherapy and endocrine therapy. Eighty-five women were evaluable for drug response. One patient showed complete remission and 14 patients partial response, for an overall response rate of 17%. The median duration of response was 11+ months. The response rate was highest in the presence of soft tissue involvement (36%). The most common side effects were transient skin rash, lethargy, and dizziness. Two patients discontinued treatment because of cutaneous allergy. Aminoglutethimide can be considered a moderately active agent when utilized as second- or third-line hormonal therapy.  相似文献   
6.
A 23 year-old man with x-linked Becker type muscular distrophy underwent cardiac transplantation because of dilated cardiomyopathy complicated by terminal heart failure. The muscular functional impairment was mild and slowly progressive, whereas the cardiac disease was severe and rapidly progressive. The ventricular cavities of the explanted heart were hugely dilated and the left ventricular wall thickness was moderately increased. Microscopically, a diffuse hypertrophy of the myocardial fibers and a widespread interstitial collagenous fibrosis were present. At a follow-up, two years after treatment, the patient is alive and fairly well; the degree of his muscular disability is substantially unchanged.  相似文献   
7.
Immunohistochemical study of p53 in human lung carcinomas.   总被引:19,自引:2,他引:19       下载免费PDF全文
Immunohistochemical analysis of p53 protein was carried out on 95 lung carcinomas from all histological types, including 60 primary tumors, 35 lymph node metastases, and 36 corresponding nude mice xenografts, using four antibodies: PAb240 specific for some mutant conformations; PAb421, PAb1801, and CM1 reactive with most of the forms of p53. Nuclear staining with at least two of those four antibodies revealed the presence of an accumulated protein, considered as indicative of a missense mutation in the p53 gene, in 50% of primary tumors of all histological types, except carcinoids. Some defect of messenger RNA expression was detected by Northern blot analysis in an additional 26% of tumors. p53 immunophenotype of the original tumor was fairly maintained on nude mice. p53 accumulation was not correlated with survival, but with disease extension (P = 0.01). Finally, immunohistochemical analysis allowed the recognition of p53 mutant immunophenotype in 41% of tumors where p53 DNA and messenger RNA were apparently normal, using standard molecular biology. Thus, this method provides a rapid and efficient approach for studying p53 mutations leading to an accumulated protein in lung tumors cells.  相似文献   
8.
9.
We compared the performance of two UltraSensitive AMPLICOR HIV-1 MONITOR kits (version 1.5 [v1.5] versus v1.0) by retesting 404 plasma samples with low viral loads (<3,000 copies/ml) with both kits. With 292 samples that initially had <50 copies/ml by the v1.0 kit, the v1.5 assay was more sensitive than the v1.0 assay for samples with human immunodeficiency virus type 1 RNA near the 50-copy/ml cutoff (P = 0.0146). Median numbers of copies per milliliter were similar for 112 samples with 50 to 3,000 copies/ml with no difference in sensitivity with a 200-copy/ml cutoff.  相似文献   
10.
Use of sequencing-based genotyping as a diagnostic assay for human immunodeficiency virus (HIV) antiretroviral resistance is increasing. Periodic evaluation of the proficiency of laboratories performing this assay should be established. It is important to identify components of the assay that influence the generation of reliable sequencing data and that should and can be monitored. A model was developed to determine what parameters were reasonable and feasible for assessing the performance of genotyping assays. Ten laboratories using the genotyping platform, HIV-1 Genotyping System (HGS) v. 1 and software versions 1.1 or 2.0, participated in two rounds of testing. For each round, each group was sent a panel consisting of three clinical samples to sequence in real time. Six months later, seven laboratories using the TRUGENE HIV-1 Genotyping Kit participated in a separate round, working with both panels at the same time. Analysis of the data showed that one main indicator of genotyping proficiency was achievement of > or =98% sequence homology of a sample tested to a group consensus sequence for that sample. A second was concordant identification of codons at sites identified with resistance mutations in the sample, although scoring of these criteria is still undetermined from this study. These criteria are applicable to all sequence-based genotyping platforms and have been used as a baseline for assessing the performance of genotyping for the determination of antiretroviral resistance in our ongoing proficiency program.  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