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   5078篇
  免费   225篇
  国内免费   40篇
耳鼻咽喉   79篇
儿科学   151篇
妇产科学   94篇
基础医学   618篇
口腔科学   78篇
临床医学   442篇
内科学   1171篇
皮肤病学   95篇
神经病学   714篇
特种医学   204篇
外科学   704篇
综合类   14篇
一般理论   2篇
预防医学   208篇
眼科学   39篇
药学   264篇
中国医学   18篇
肿瘤学   448篇
  2023年   32篇
  2022年   66篇
  2021年   121篇
  2020年   68篇
  2019年   114篇
  2018年   139篇
  2017年   98篇
  2016年   128篇
  2015年   124篇
  2014年   187篇
  2013年   241篇
  2012年   354篇
  2011年   302篇
  2010年   199篇
  2009年   199篇
  2008年   332篇
  2007年   321篇
  2006年   306篇
  2005年   325篇
  2004年   293篇
  2003年   266篇
  2002年   251篇
  2001年   103篇
  2000年   75篇
  1999年   65篇
  1998年   79篇
  1997年   44篇
  1996年   23篇
  1995年   40篇
  1994年   30篇
  1993年   24篇
  1992年   48篇
  1991年   27篇
  1990年   37篇
  1989年   28篇
  1988年   25篇
  1987年   26篇
  1986年   24篇
  1985年   18篇
  1984年   20篇
  1983年   18篇
  1982年   17篇
  1981年   8篇
  1980年   7篇
  1979年   13篇
  1974年   14篇
  1973年   7篇
  1972年   6篇
  1970年   8篇
  1967年   10篇
排序方式: 共有5343条查询结果,搜索用时 15 毫秒
1.
2.
This meta-analysis focuses on the accuracy of upgrading to clinically significant prostate cancer (PCa) by multiparametric magnetic resonance imaging-targeted biopsy (MRI-TB) versus systematic biopsy (SB). We searched the Medline, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Scopus, and Literatura Latino Americana em Ciências da Saúde databases through January 2020 for comparative, retrospective/prospective, paired-cohort, and randomized clinical trials with paired comparisons. The population consisted of patients with low-risk PCa in active surveillance with at least 1 index lesion on imaging. We evaluated the quality of evidence by using the Quality Assessment of Diagnostic Accuracy Studies-2 score. Group comparisons considered the differences between the area under the curve summary receiver operating characteristic curve in a 2-tailed method. We also compared the positive predictive value of the best single method (MRI-TB or SB) and the referral study test (combined biopsy, a combination of MRI-TB and SB). The meta-analysis included 6 studies enrolling 741 patients. The pooled sensitivity for the 2 groups was 0.79 (95% confidence interval, 0.74-0.83; I2 = 75%) and 0.67 (95% confidence interval, 0.63-0.74; I2 = 55.4%), respectively. The area under the curve for the MRI-TB and SB groups were 0.99 and 0.92 (P < .001), respectively. The positive predictive value for the MRI-TB and combined biopsy groups were similar. The accumulated evidence suggests better results for MRI-TB compared with SB. Therefore, use of MRI-TB alone may be preferable in patients in active surveillance harboring low-risk PCa.  相似文献   
3.
4.
5.
Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.  相似文献   
6.
7.
The International Society of Pediatric Oncology (SIOP) recommends preoperative treatment in the management of eligible patients with Wilms' tumor. Until 1980, children younger than 12 months of age (infants) at diagnosis had been excluded from the SIOP trials. SIOP 6, conducted from 1980 to 1987, was the first SIOP study to include infants older than 6 months of age. This retrospective analysis of 145 infants registered to SIOP 6 demonstrates that in infants older than 6 months and having favorable histology (FH), a two-drug preoperative chemotherapy (CT) regimen of 4 weeks significantly ameliorated stage distribution as determined at delayed surgery but did not affect a good outcome. However, the CT dose utilized in SIOP 6 resulted in an unacceptable toxicity in this age group, and SIOP 9, the new SIOP study of Wilms' tumor, recommends a reduced dose of CT in infants. Preoperative CT is not recommended in infants younger than 6 months of age. Specifically, the high incidence (29%) of mesoblastic nephroma in this age group does not justify such an approach. Histopathologic diagnosis should be obtained in these patients before any treatment.  相似文献   
8.
Insulin-like growth factor II (IGF-II) is a mitogen for manycell types and an important modulator of muscle growth and differentiation.IGF-II gene is prevalently expressed during prenatal developmentand its gene activity is regulated by genomic imprinting, inthat the allele inherited from the father is active and theallele inherited from the mother is inactive in most normaltissues. IGF-II expression is activated in several types ofhuman neoplasms and an alteration of IGF-II imprinting has beendescribed in Beckwith–Wiedemann syndrome and Wilms' tumour.Here we show that monoallelic expression of IGF-II gene is conservedin normal adult muscle tissue whereas two or more copies ofactive IGF-II alleles, arising by either relaxation of imprintingor duplication of the active allele, are found in 9 out of 11(82%) rhabdomyo-sarcomas retaining heterozygosity at 11p15,regardless of the histological subtype. Since IGF-II has beenindicated as an autocrine growth factor for rhabdomyosarcomacells, these findings strongly suggest that acquisition of adouble dosage of active IGF-II gene is an important step forthe initiation or progression of rhabdomyosarcoma tumorigenesis.Among different types of muscle tumors, relaxation of imprintingseems to arise prevalently in rhabdomyosarcomas, since we havedetected only one case of partial reactivation of the maternalIGF-II allele out of 7 lelomyosarcomas tested.  相似文献   
9.
BACKGROUND: Wounds too extensive to permit primary repair by suturing can be closed using a skin graft or skin flap and the choice of method depends on a series of factors. Practice and personal experience play a role, as well as the characteristics of the lesion and its site. Each case poses special problems, so it is not possible to establish firm rules. OBJECTIVE: To present a surgical technique for the closure of a circular defect located on the dorsum of the foot, which resulted from the extirpation of a melanoma by surgery. METHODS: In this case we used a mixed procedure consisting of skin flaps and a double full-thickness skin graft. For this operation we used dog-ears resulting from the circular exeresis performed for the extirpation of the tumour. RESULTS: The reconstructive results were good and there were no postoperative complications. CONCLUSIONS: We consider this procedure particularly suitable for certain anatomical sites, such as the dorsum of the foot, where the skin is less elastic and thinner; and for patients who are not willing to accept skin removal from other sites or for flaps to be made with more invasive operations and more constructed scars.  相似文献   
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