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   32573篇
  免费   2248篇
  国内免费   117篇
耳鼻咽喉   244篇
儿科学   1078篇
妇产科学   638篇
基础医学   4390篇
口腔科学   905篇
临床医学   3312篇
内科学   6377篇
皮肤病学   412篇
神经病学   3502篇
特种医学   1163篇
外国民族医学   6篇
外科学   4583篇
综合类   394篇
一般理论   52篇
预防医学   2390篇
眼科学   1206篇
药学   2307篇
中国医学   51篇
肿瘤学   1928篇
  2022年   202篇
  2021年   428篇
  2020年   274篇
  2019年   444篇
  2018年   541篇
  2017年   450篇
  2016年   489篇
  2015年   548篇
  2014年   765篇
  2013年   1280篇
  2012年   1952篇
  2011年   2137篇
  2010年   1158篇
  2009年   1120篇
  2008年   2047篇
  2007年   2325篇
  2006年   2214篇
  2005年   2244篇
  2004年   2152篇
  2003年   2134篇
  2002年   2030篇
  2001年   299篇
  2000年   241篇
  1999年   309篇
  1998年   460篇
  1997年   411篇
  1996年   317篇
  1995年   336篇
  1994年   323篇
  1993年   314篇
  1992年   237篇
  1991年   222篇
  1990年   191篇
  1989年   165篇
  1988年   172篇
  1987年   173篇
  1986年   205篇
  1985年   196篇
  1984年   311篇
  1983年   288篇
  1982年   357篇
  1981年   320篇
  1980年   330篇
  1979年   173篇
  1978年   202篇
  1977年   207篇
  1976年   131篇
  1975年   141篇
  1974年   125篇
  1973年   104篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
A limited flip angle gradient-echo 3D volume acquisition imaging protocol for mapping partial pressure of oxygen (pO2) in perfluorocarbon compounds (PFCs) at low field (0.14 T) is presented. The pO2 measurement method is based on the paramagnetic effect of dissolved molecular oxygen (O2) which reduces the PFC 19F T1? Specific objectives related to imaging of PFCs through use of the protocol include improved image signal-to-noise characteristics and elimination of 19F chemical shift artifacts. A parametric Wiener deconvolution filtering algorithm is used for suppression of 19F chemical shift artifacts. Application of the protocol is illustrated in a series of calculated pO2 maps of a gas equilibrated, multi-chamber phantom containing perfluorotributylamine (FC-43). The utility of the protocol is demonstrated in vivo through images of a commercially available perfluorocarbon based blood substitute emulsion containing FC-43 sequestered in the liver and spleen of a rat.  相似文献   
34.
A bstract Background : Ventricular-to-pulmonary artery conduits in growing patients with congenital heart disease will require replacement from time to time due to somatic growth, neointimal hyperplasia, and pulmonary artery stenosis. The purpose of this article is to review our experience with ascending aortic extension for significant long-segment pulmonary artery stenosis in patients undergoing reoperation for right ventricular-to-pulmonary artery conduit replacement. Methods : From 1989 to 1997, 8 patients had aortic transection, right pulmonary artery augmentation arterioplasty, and aortic interposition graft (Hemashield in 7 and Gore-tex in 1) in association with right ventricular-to-pulmonary artery conduit replacement in 7 patients and completion Fontan operation in 1 patient. Aortic cross-clamp time was 90 ± 34 minutes, and the cardiopulmonary bypass time was 205 ± 37 minutes. Results : All patients survived. In those 7 patients who had conduit replacement, the RV/LV ratio declined from 0.78 ± 0.15 to 0.45 ±; 0.05 postoperatively (P < 0.05). Average length of stay was 8.9 ± 7.2 days. Follow-up range is 18 months to 8 years (mean 4 years). Two complications included cardiac transplantation for pre-existing poor left ventricular function and accelerated conduit stenosis leading to conduit re-replacement. Conclusion : Ascending aortic extension facilitates long-segment pulmonary artery augmentation arterioplasty and enlarges the retroaortic space, preventing future compression restenosis.  相似文献   
35.
Abstract Several statistical models that have been suggested in the periodontal literature for describing longitudinal attachment level changes, such as the gradual loss, single-burst, multiple-burst, and random walk models as well as other models introduced in this paper are compared by their power to predict future attachment loss. The data used in this analysis is from 1061 sites of 8 subjects, with moderate to severe periodontal disease, monitored monthly for about a year. This study found that none of the suggested models could significantly outperform the naive mean predictor, which predicts the future attachment level from the past mean. It was also found that no single model, such as the burst, gradual, or random walk, together with measurement error can fully explain the variation in the data. These results indicate that in the course of one year, the attachment level change may not follow the same model. Consequently, a model that fits well to past data cannot be accurately extended to the future.  相似文献   
36.
37.
Editorial comment   总被引:2,自引:0,他引:2  
  相似文献   
38.
Identification of Alcohol Abuse and Alcoholism with Biological Parameters   总被引:3,自引:0,他引:3  
The prevalence and incidence of heavy alcohol consumption are major problems which have been increasing in many countries in recent years. It is crucial for physicians to consistently identify early drinking problems as well as the various end disease states in order to minimize suffering and maximize recovery. This paper reviews the evolutionary development of clinical tools for detection of alcohol abuse. The focus is primarily on clinical/biochemical indicators of alcohol abuse, emphasizing but not limited to changes in hematological characteristics, liver enzyme activity, lipids, immune function factors, hormones, neurological factors, and some physically based tests. Use of test combinations and sophisticated statistical analysis of pattern changes in test batteries evidence increased diagnostic efficiency.  相似文献   
39.
CCAAT displacement protein (CDP), a nuclear protein of 180-190 kDa, contains a triplicated motif, the cut domain, similar (80-90% conserved) to three repeats of 60-65 amino acids first identified in Drosophila cut, a homeo-domain protein involved in cell-fate decisions in development. Cut repeats bind DNA and exhibit subtle differences in target-site recognition. DNA sequences specifically bound by cut repeats were isolated by PCR-mediated DNA target-site selection. Sequences selected for cut repeat 2 and 3 (CR2 and CR3) binding are A+T-rich and favor an ATA motif with similar, but not identical, flanking base preferences. CR2 and CR3 discriminate among similar target sequences. CR1, which is more divergent from CR2 and CR3, displays the most restricted pattern of DNA sequence recognition. Methylation interference analysis demonstrates different protein-DNA contacts for CR1 and CR3 binding to a target sequence. Thus, CDP/cut is a complex protein whose DNA-binding properties reflect the combinatorial interaction of four domains (three cut repeats and one homeodomain) with target DNA sequences.  相似文献   
40.
In summary, we have described two patients with CRMO and psoriasis, and have reviewed the musculoskeletal manifestations associated with pustular eruptions of the palms and soles. In view of the frequent occurrence of PPP in patients with CRMO, we suggest that the occurrence of psoriasis in our two patients is more than coincidence, and that noninfectious, inflammatory lesions of bone may be another musculoskeletal manifestation of psoriasis. This rare association, as well as the association of PPP with disorders associated with new bone formation, may shed new insights on the relatively common finding of periosteal elevation associated with psoriatic arthritis and the occasional severe juxta-articular osteolytic destructive bone lesions seen in psoriatic arthritis.  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