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   5556篇
  免费   379篇
  国内免费   19篇
耳鼻咽喉   49篇
儿科学   92篇
妇产科学   76篇
基础医学   802篇
口腔科学   80篇
临床医学   539篇
内科学   1196篇
皮肤病学   89篇
神经病学   789篇
特种医学   470篇
外科学   693篇
综合类   60篇
一般理论   1篇
预防医学   282篇
眼科学   113篇
药学   326篇
中国医学   3篇
肿瘤学   294篇
  2024年   7篇
  2023年   60篇
  2022年   74篇
  2021年   163篇
  2020年   91篇
  2019年   123篇
  2018年   134篇
  2017年   127篇
  2016年   149篇
  2015年   157篇
  2014年   206篇
  2013年   262篇
  2012年   417篇
  2011年   432篇
  2010年   252篇
  2009年   203篇
  2008年   370篇
  2007年   374篇
  2006年   352篇
  2005年   316篇
  2004年   310篇
  2003年   248篇
  2002年   248篇
  2001年   87篇
  2000年   67篇
  1999年   81篇
  1998年   67篇
  1997年   61篇
  1996年   32篇
  1995年   27篇
  1994年   28篇
  1993年   22篇
  1992年   34篇
  1991年   41篇
  1990年   30篇
  1989年   34篇
  1988年   29篇
  1987年   26篇
  1986年   24篇
  1985年   32篇
  1984年   21篇
  1983年   19篇
  1982年   17篇
  1981年   5篇
  1979年   19篇
  1978年   12篇
  1977年   7篇
  1976年   11篇
  1974年   5篇
  1967年   4篇
排序方式: 共有5954条查询结果,搜索用时 62 毫秒
81.
82.

Background and purpose

To evaluate whether brain CT perfusion (CTP) aids in the detection of intracranial vessel occlusion on CT angiography (CTA) in acute ischemic stroke.

Materials and methods

Medical-ethical committee approval of our hospital was obtained and informed consent was waived. Patients suspected of acute ischemic stroke who underwent non-contrast CT(NCCT), CTA and whole-brain CTP in our center in the year 2015 were included. Three observers with different levels of experience evaluated the imaging data of 110 patients for the presence or absence of intracranial arterial vessel occlusion with two strategies. In the first strategy, only NCCT and CTA were available. In the second strategy, CTP maps were provided in addition to NCCT and CTA. Receiver-operating-characteristic (ROC) analysis was used for the evaluation of diagnostic accuracy.

Results

Overall, a brain perfusion deficit was scored present in 87–89% of the patients with an intracranial vessel occlusion, more frequently observed in the anterior than in the posterior circulation. Performance of intracranial vessel occlusion detection on CTA was significantly improved with the availability of CTP maps as compared to the first strategy (P = 0.023), due to improved detection of distal and posterior circulation vessel occlusions (P-values of 0.032 and 0.003 respectively). No added value of CTP was found for intracranial proximal vessel occlusion detection, with already high accuracy based on NCCT and CTA alone.

Conclusion

The performance of intracranial vessel occlusion detection on CTA was improved with the availability of brain CT perfusion maps due to the improved detection of distal and posterior circulation vessel occlusions.  相似文献   
83.
In primary cultures of rat pituitary cells and in a pituitary sommatolactotroph cell line (GH4C1), endogenous core-clock- as well as hormone-genes such as prolactin displayed a rhythmic expression pattern, fitted by a sinusoidal equation in which the period value was close to the circadian one. This is consistent with the presence of a functional circadian oscillator in pituitary cells whose importance was ascertained in GH4C1 cell lines stably expressing a dominant negative mutant of BMAL1. In these cells, both endogenous core-clock- and prolactin-genes no more displayed a circadian pattern. Some genes we recently identified as mouse pituitary BMAL1-regulated genes in a DNA-microarray study, lost their circadian pattern in these cells, suggesting that BMAL1 controlled these genes locally in the pituitary. The intra-pituitary circadian oscillator could then play a role in the physiology of the gland that would not be seen anymore as a structure only driven by hypothalamic rhythmic control.  相似文献   
84.
The CNAP technology (CNSystems Medizintechnik AG, Graz, Austria) allows continuous noninvasive arterial pressure waveform recording based on the volume clamp method and estimation of cardiac output (CO) by pulse contour analysis. We compared CNAP-derived CO measurements (CNCO) with intermittent invasive CO measurements (pulmonary artery catheter; PAC-CO) in postoperative cardiothoracic surgery patients. In 51 intensive care unit patients after cardiothoracic surgery, we measured PAC-CO (criterion standard) and CNCO at three different time points. We conducted two separate comparative analyses: (1) CNCO auto-calibrated to biometric patient data (CNCObio) versus PAC-CO and (2) CNCO calibrated to the first simultaneously measured PAC-CO value (CNCOcal) versus PAC-CO. The agreement between the two methods was statistically assessed by Bland–Altman analysis and the percentage error. In a subgroup of patients, a passive leg raising maneuver was performed for clinical indications and we present the changes in PAC-CO and CNCO in four-quadrant plots (exclusion zone 0.5 L/min) in order to evaluate the trending ability of CNCO. The mean difference between CNCObio and PAC-CO was +0.5 L/min (standard deviation?±?1.3 L/min; 95% limits of agreement ?1.9 to +3.0 L/min). The percentage error was 49%. The concordance rate was 100%. For CNCOcal, the mean difference was ?0.3 L/min (±0.5 L/min; ?1.2 to +0.7 L/min) with a percentage error of 19%. In this clinical study in cardiothoracic surgery patients, CNCOcal showed good agreement when compared with PAC-CO. For CNCObio, we observed a higher percentage error and good trending ability (concordance rate 100%).  相似文献   
85.
86.
87.
Colorectal cancer is a common malignancy and often presents with synchronous or metachronous distant spread. For patients with hepatic metastases, resection is the principal curative option. Liberalization of the indications for hepatic resection has introduced a number of challenges related to the size, distribution, and number of metastases as well as the condition of the future liver remnant. Advances in systemic therapy have solidified its role as both an important adjunct to surgery and also for many patients as a mechanism to facilitate resection. In patients whose disease is marginally resectable as a consequence of the distribution of hepatic lesions that precludes complete resection or out of concern for the future liver remnant, a number of strategies have been advocated, including prehepatectomy systemic therapy, staged surgical approaches, ablative technologies, and preoperative portal vein embolization. It is the purpose of this review to discuss ways in which to optimize the treatment of patients with potentially resectable disease, specifically those who are judged to have “borderline” resectable situations.  相似文献   
88.
89.
90.
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