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   4487篇
  免费   302篇
  国内免费   19篇
耳鼻咽喉   123篇
儿科学   214篇
妇产科学   126篇
基础医学   610篇
口腔科学   95篇
临床医学   442篇
内科学   783篇
皮肤病学   324篇
神经病学   225篇
特种医学   278篇
外科学   824篇
综合类   107篇
现状与发展   30篇
一般理论   6篇
预防医学   148篇
眼科学   50篇
药学   232篇
中国医学   4篇
肿瘤学   187篇
  2023年   189篇
  2021年   53篇
  2020年   70篇
  2019年   50篇
  2018年   94篇
  2017年   70篇
  2016年   82篇
  2015年   107篇
  2014年   136篇
  2013年   167篇
  2012年   160篇
  2011年   174篇
  2010年   152篇
  2009年   169篇
  2008年   142篇
  2007年   177篇
  2006年   134篇
  2005年   169篇
  2004年   130篇
  2003年   119篇
  2002年   126篇
  2001年   79篇
  2000年   105篇
  1999年   88篇
  1998年   60篇
  1997年   69篇
  1996年   63篇
  1995年   51篇
  1994年   46篇
  1993年   42篇
  1992年   43篇
  1991年   50篇
  1990年   61篇
  1989年   59篇
  1988年   51篇
  1987年   51篇
  1986年   38篇
  1985年   41篇
  1984年   32篇
  1981年   22篇
  1971年   27篇
  1939年   23篇
  1933年   35篇
  1932年   30篇
  1930年   21篇
  1925年   20篇
  1922年   21篇
  1913年   39篇
  1912年   22篇
  1903年   23篇
排序方式: 共有4808条查询结果,搜索用时 31 毫秒
1.
2.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence.  相似文献   
3.
Zusammenfassung Die von uns angegebene Flockungsprobe im Serum mit Hayemscher Lösung zur Diagnose der atrophischen Lebercirrhose und zur einfachen Erkennung der meisten Takata-positiven und Takata-negativen Seren eignet sich auch zur Untersuchung von Ascites bezüglich seiner Genese. Auf Zusatz von Hayemscher Lösung zeigt der Ascites bei Lebercirrhose ein wesentlich anderes Verhalten als der Ascites bei Carcinom, Nephrose oder Herzinsuffizienz. Die einfache und rasch ausführbare Untersuchung des frischen Ascites mit Hayemscher Losung gestattet daher einen Ascites bei Lebercirrhose von solchen anderer Genese in kurzer Zeit zu differenzieren.  相似文献   
4.
5.
6.
A group of 159 patients previously reported as having margins positive for disease after radical prostatectomy with or without adjunctive postoperative radiation was reanalyzed to determine whether the reported benefit did indeed exist. Upon re-examination of the 159 patients 15 were identified who did not receive radical prostatectomy but who were analyzed as if they had received this therapy. An updated review of the total pool of 159 patients with analysis as to failure, death of any cause or death of prostatic cancer demonstrated no benefit of postoperative radiation therapy for margin positive disease. Exclusion of patients who did not receive radical prostatectomy and analysis as described also failed to identify any benefit of postoperative adjunctive radiation therapy.  相似文献   
7.
8.
PURPOSE: This paper briefly summarizes the research on increased radiosensitivity in breast cancer patients measured by the micronucleus test (MNT) and its association to genetic variants in DNA repair genes. More preliminary data are presented on the distribution of chromosomes and chromosome fragments in micronuclei (MN) in order to gain more information on clastogenic and aneugenic effects and better understand the phenotype of increased radiosensitivity. MATERIAL AND METHODS: Reports of relevant studies obtained from a search of PubMed and studies referenced in those reports were reviewed. In four patients with high MN frequency (three cancer patients, one control) and four probands with low MN frequency, the presence of chromosome fragments or whole chromosomes in MN was determined by fluorescence in situ hybridization analysis for chromosomes 1, 7, and 17. RESULTS: An increased MN frequency in breast cancer patients compared to controls has consistently been reported with high significance. Higher MN frequencies were observed in 20-50% of breast cancer patients. Chromosomal fragments of chromosome 17, but not of chromosomes 1 and 7 were more frequent in the probands with high MN frequency than in those with low frequency (p = 0.045). CONCLUSION: The MNT detects a cellular phenotype common to a portion of sporadic breast cancer patients. This phenotype is very likely to be genetically determined. For the genetic dissection of breast cancer susceptibility this phenotype may turn out to be more efficient than breast cancer itself. Additional parameters which can be measured simultaneously with the MN frequency may be able to further enhance its usefulness.  相似文献   
9.
OBJECTIVE: Recent studies have demonstrated that transplanted bone marrow-derived stem cells (BMCs) possess a broad differentiation potential and are able to form new cardiomyocytes. However, the identity of BMCs as true cardiomyocytes is still ambiguous. Therefore, we investigated the fate of transplanted fluorescence labeled BMCs and cardiomyocytes in co-culture. METHODS: For cell tracking we used two different fluorescent probes, Vybrant/DiO and Vybrant/DiI. BMCs were taken from human sternal marrow, purified using a Ficoll-gradient-centrifugation, treated with 5-azacytidine and stained with Vybrant/DiO. Furthermore, isolated spontaneous beating cardiomyocytes of neonatal rats (CM) were labeled with Vybrant/DiI. Thereafter, the BMCs were transplanted into CM-cultures and investigated on day 1, 4, 7, 14 and 28 using two-color fluorescence phenotyping by laser-scanning-cytometry (LSC). Two-color positive cells were harvested by patch-clamp technique and beta-MHC mRNA expression was analyzed by single-cell PCR. RESULTS: Two different morphological phenotypes were observed by LSC. First, isolated DiO labeled BMCs without contact or with direct cell contact to DiI labeled CMs. Second, some BMCs and CMs were double positive for DiO/DiI spontaneously forming hybrids. This population increased by 18% from day 1 to 4 and decreased only slightly until day 28. Additionally, few two-color positive cell formations expressed both human and rat specific beta-MHC mRNA as well as only human beta-MHC mRNA indicating that cell-fusion and transdifferentiation has occurred. CONCLUSION: These observations provide in vitro evidence for spontaneous cell fusion and transdifferentiation of BMCs in co-culture, raising the possibility that the observed phenomenons may contribute to development or maintenance of these cell types.  相似文献   
10.
Objectives. Epididymal cystadenomas (ECs) are frequently found in association with von Hippel-Lindau disease (VHL), but little has been reported about their sonographic appearance. We review the sonographic appearance of ECs, the relationship of ECs to other manifestations of VHL, and the specific genetic mutations associated with ECs.Methods. Fifty-six male patients with VHL were examined with scrotal sonography and physical examination as part of a larger screening program for VHL. The head of the epididymis was measured in two planes on sonography and compared with age-matched normal controls. All VHL patients with palpable epididymal abnormalities or enlargement (more than two standard deviations) of the head of the epididymis on ultrasound were considered positive for EC.Results. Thirty of 56 (54%) male patients with VHL demonstrated a unilateral (n = 10; 33%) or bilateral (n = 20; 67%) solid abnormality in the head of the epididymis suggestive of EC. Sonographic appearances ranged from a solid mass with multiple tiny cysts to an almost completely solid mass. The most common appearance was a 15- to 20-mm solid mass with small cystic components. Dilated efferent ductules were seen within the testicle in 7 men, evidently a result of chronic obstruction. There was no association between the clinical subtype of VHL and the presence of ECs (P >0.10, chi square). Mutations resulting in a truncated gene product were associated with the development of ECs but the association did not reach statistical significance (P = 0.06).Conclusions. ECs are a common manifestation of VHL in men and exhibit a range of appearances on ultrasound. Sonography can be used to identify ECs and determine the extent of cystic dilation of the rete testes. The benign course of ECs and the usual absence of clinical symptoms favor a conservative approach to their management.  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