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   207623篇
  免费   27664篇
  国内免费   1661篇
耳鼻咽喉   1682篇
儿科学   1735篇
妇产科学   5212篇
基础医学   15454篇
口腔科学   2141篇
临床医学   16668篇
内科学   18132篇
皮肤病学   1393篇
神经病学   706篇
特种医学   6551篇
外国民族医学   272篇
外科学   29380篇
综合类   27459篇
一般理论   3篇
预防医学   9676篇
眼科学   125篇
药学   14339篇
  141篇
中国医学   4940篇
肿瘤学   80939篇
  2024年   39篇
  2023年   4286篇
  2022年   6051篇
  2021年   9820篇
  2020年   10817篇
  2019年   9021篇
  2018年   8465篇
  2017年   9444篇
  2016年   9776篇
  2015年   10619篇
  2014年   16374篇
  2013年   16513篇
  2012年   13416篇
  2011年   14004篇
  2010年   10175篇
  2009年   10399篇
  2008年   10758篇
  2007年   10055篇
  2006年   9024篇
  2005年   7173篇
  2004年   6115篇
  2003年   5156篇
  2002年   4343篇
  2001年   3970篇
  2000年   3260篇
  1999年   2662篇
  1998年   2090篇
  1997年   1819篇
  1996年   1501篇
  1995年   1573篇
  1994年   1278篇
  1993年   993篇
  1992年   862篇
  1991年   800篇
  1990年   589篇
  1989年   546篇
  1988年   462篇
  1987年   406篇
  1986年   318篇
  1985年   401篇
  1984年   330篇
  1983年   221篇
  1982年   233篇
  1981年   217篇
  1980年   176篇
  1979年   129篇
  1978年   89篇
  1977年   62篇
  1976年   58篇
  1975年   33篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The association of overweight and obesity with premenopausal breast cancer remained unclear, ethnicity could play a role. A MEDLINE and PUBMED search of all studies on obesity and premenopausal breast cancer published from 2000 to 2010 was conducted. Dose‐response meta‐analysis was used to determine the risk of premenopausal breast cancer associated with different anthropometric measurements in different ethnic groups. For body mass index (BMI), each 5 kg m?2 increase was inversely associated with the risk of premenopausal breast cancer (RR = 0.95, 95% confidence interval [CI]: 0.94, 0.97). After stratification by ethnicity, the inverse association remained significant only among Africans (RR = 0.95, 95% CI: 0.91, 0.98) and Caucasians (RR = 0.93, 95% CI: 0.91, 0.95). In contrast, among Asian women, a significant positive association was observed. For waist‐to‐hip ratio (WHR), each 0.1 unit increase was positively associated with premenopausal breast cancer (RR = 1.08, 95% CI: 1.01, 1.16); the largest effect was detected in Asian women (RR = 1.19, 95% CI: 1.15, 1.24), while small effects of 5% and 6% were observed in African and Caucasian women, respectively. Our results suggest the importance of considering both fat distribution and ethnicity when studying premenopausal breast cancer.  相似文献   
4.
5.
6.
AimTo retrospectively study the frequency and magnitude of complications associated with computed tomography (CT) colonography in clinical practice.MethodsA questionnaire on complications of CT colonography was sent to Italian public radiology departments identified as practicing CT colonography with a reasonable level of training. The frequency of complications and possible risk factors were retrospectively determined. Responses were collated and row frequencies determined. A multivariate analysis of the factors causing adverse events was also performed.Results40,121 examinations were performed in13 centers during the study period. No deaths were reported. Bowel perforations occurred in 0.02% (7 exams). All perforations were asymptomatic and occurred in patients undergoing manual insufflation. Five perforations (71%) occurred in procedures performed following a recent colonoscopy. There was no significant difference between perforations associated with rectal balloon (0.017%) and those that were not (0.02%). Complications related to vasovagal reaction (either with or without spasmolytic) occurred in 0.16% (63 exams). All vasovagal reactions resolved in less than 3 h, without any sequelae.ConclusionsPerforation rate at CT colonography in Italy is comparable with elsewhere in the world, occurring regardless of the experience of radiology centers. Although the risk is very small, it may not be negligible when compared with the risk of diagnostic colonoscopy.  相似文献   
7.
Kidney transplant recipients have a heightened risk of developing neoplasms. Immunosuppressive treatments decrease the incidence of transplant rejection but increase the risk of infections, including BK virus (BKV). This infection is acquired in childhood and remains latent in the renal and urinary epithelium. In cases of immunodeficiency, BKV has been implicated as a tumor virus, but the role of BKV in cancer is a controversial topic and is difficult to determine. In the tumor cells, it is possible to detect fragments of the viral genome that could alter the control mechanisms of the cell cycle and DNA repair. We report the case of a kidney transplant recipient who developed BKV nephropathy and carcinoma of the bladder, supporting a possible role for BKV in the oncogenic pathway in this clinical setting, but the role of BKV in cancer remains a controversial topic and difficult to determine.  相似文献   
8.
9.

After the Three Mile Island nuclear plant accident in 1979, a local Pennsylvania resident told The New York Times ’You live with that plant over there for years and years and don't think much about it. But it's like living with a rattlesnake. Sooner or later it's going to bite you. You just don't know when.’ As we enter the twenty‐first century, many communities find themselves living with rattlesnakes ‐ one at least of which has already bitten. This article considers the official responses to Chernobyl in the first decade after the accident and compares them to the statements surrounding the sudden 1998 decision to decommission the nuclear reprocessing plant at Dounreay in Scotland.  相似文献   
10.
PurposeWe sought to commission a gynecologic shielded colpostat analytic model provided from a treatment planning system (TPS) library. We have reported retrospectively the dosimetric impact of this applicator model in a cohort of patients.Methods and MaterialsA commercial TPS with a grid-based Boltzmann solver (GBBS) was commissioned for 192Ir high-dose-rate (HDR) brachytherapy for cervical cancer with stainless steel–shielded colpostats. Verification of the colpostat analytic model was verified using a radiograph and vendor schematics. MCNPX v2.6 Monte Carlo simulations were performed to compare dose distributions around the applicator in water with the TPS GBBS dose predictions. Retrospectively, the dosimetric impact was assessed over 24 cervical cancer patients’ HDR plans.ResultsApplicator (TPS ID #AL13122005) shield dimensions were within 0.4 mm of the independent shield dimensions verification. GBBS profiles in planes bisecting the cap around the applicator agreed with Monte Carlo simulations within 2% at most locations; differing screw representations resulted in differences of up to 9%. For the retrospective study, the GBBS doses differed from TG-43 as follows (mean value ± standard deviation [min, max]): International Commission on Radiation units [ICRU]rectum (?8.4 ± 2.5% [?14.1, ?4.1%]), ICRUbladder (?7.2 ± 3.6% [?15.7, ?2.1%]), D2cc-rectum (?6.2 ± 2.6% [?11.9, ?0.8%]), D2cc-sigmoid (?5.6 ± 2.6% [?9.3, ?2.0%]), and D2cc-bladder (?3.4 ± 1.9% [?7.2, ?1.1%]).ConclusionsAs brachytherapy TPSs implement advanced model-based dose calculations, the analytic applicator models stored in TPSs should be independently validated before clinical use. For this cohort, clinically meaningful differences (>5%) from TG-43 were observed. Accurate dosimetric modeling of shielded applicators may help to refine organ toxicity studies.  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