全文获取类型
收费全文 | 1012篇 |
免费 | 69篇 |
国内免费 | 32篇 |
出版年
2023年 | 18篇 |
2022年 | 30篇 |
2021年 | 72篇 |
2020年 | 73篇 |
2019年 | 55篇 |
2018年 | 68篇 |
2017年 | 57篇 |
2016年 | 42篇 |
2015年 | 39篇 |
2014年 | 50篇 |
2013年 | 48篇 |
2012年 | 34篇 |
2011年 | 50篇 |
2010年 | 25篇 |
2009年 | 35篇 |
2008年 | 33篇 |
2007年 | 40篇 |
2006年 | 26篇 |
2005年 | 34篇 |
2004年 | 32篇 |
2003年 | 26篇 |
2002年 | 15篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 17篇 |
1995年 | 19篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 1篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有1113条查询结果,搜索用时 15 毫秒
931.
Beilharz MW Cummins JM Bennett AL 《Biochemical and biophysical research communications》2007,355(3):740-744
The persistence of highly pathogenic avian influenza within wild bird populations has forged interest in control measures to limit a possible human pandemic. We therefore investigated the efficacy of low dose oral administration of IFN-alpha as a potential therapy against influenza infection in a murine model. We have identified an optimal low oral dose of IFN-alpha that when delivered daily as prophylactic therapy protects C57BL/6J mice from a lethal challenge with mouse adapted human influenza virus A/PR/8/34 (H1N1). These results provide strong support for the application of low dose type 1 IFN pretreatment to human influenza control. 相似文献
932.
This article considers the problem of comparing several treatments (dose levels, interventions, etc.) with the best, where the best treatment is unknown and the treatments are ordered in some sense. Order relations among treatments often occur quite naturally in practice. They may be ordered according to increasing risks, such as tolerability or safety problems with increasing dose levels in a dose-response study, for example. We tackle the problem of constructing a lower confidence bound for the smallest index of all treatments being at most marginally less effective than the (best) treatment having the largest effect. Such a bound ensures at confidence level 1 -alpha that all treatments with lower indices are relevantly less effective than the best competitor. We derive a multiple testing strategy that results in sharp confidence bounds. The proposed lower confidence bound is compared with those derived from other testing strategies. We further derive closed-form expressions for power and sample size calculations. Finally, we investigate several real data sets to illustrate various applications of our methods. 相似文献
933.
The continual reassessment method for multiple toxicity grades: a Bayesian quasi-likelihood approach
We consider the case of phase I trials for treatment of cancer or other severe diseases in which grade information is available about the severity of toxicity. Most dose allocation procedures dichotomize toxicity grades based on being dose limiting, which may not work well for severe and possibly irreversible toxicities such as renal, liver, and neurological toxicities, or toxicities with long duration. We propose a simple extension to the continual reassessment method (CRM), called the Quasi-CRM, to incorporate grade information. Toxicity grades are first converted to numeric scores that reflect their impacts on the dose allocation procedure, and then incorporated into the CRM using the quasi-Bernoulli likelihood. A simulation study demonstrates that the Quasi-CRM is superior to the standard CRM and comparable to a univariate version of the Bekele and Thall method (2004, Journal of the American Statistical Association 99, 26-35). We also present sensitivity analysis of the new method with respect to toxicity scores, and discuss practical issues such as extending the simple algorithmic up-and-down designs. 相似文献
934.
Y?ld?ray ?zgüven Kadir Yaray Fadime Alkaya Birsen Yücel Serdar Soyuer 《Reports of Practical Oncology and Radiotherapy》2014,19(3):195-205
Aim
The purpose of the present study is to show the application of the IAEA TRS-430 QA procedures of Eclipse™v7.5 TPS for photon energies. In addition, the trends of the deviations found in the conducted tests were determined.Background
In the past, the lack of complete TPS QA procedures led to some serious accidents. So, QA in the radiotherapy treatment planning process is essential for determination of accuracy in the radiotherapy process and avoidance of treatment errors.Materials and methods
The calculations of TPS and measurements of irradiations of the treatment device were compared in the study. As a result, the local dose deviation values (δ1: central beam axis, δ2: penumbra and build up region, δ3: inside field, δ4: outside beam edges, δ50–90: beam fringe, RW50: radiological width) and their confidence limit values (including systematic and random errors) were obtained.Results
The confidence limit values of δ4 were detected to increase with expanding field size. The values of δ1 and δ3 of hard wedge were larger than open fields. The values of δ2 and δ50–90 of the inhomogeneity effect test were larger, especially than other tests of this study. The average deviation was showed to increase with the rise of the wedge angle. The values of δ3 and δ4 of lung irradiation were outside tolerance.Conclusions
The QA of TPS was done and it was found that there were no reservations in its use in patient treatment. The trend of the deviations is shown. 相似文献935.
936.
目的:分析长期使用小剂量激素治疗类风湿关节(RA)炎的临床效果及安全性,并探讨小剂量激素的使用方法。方法:将49例RA患者随机分为两组,治疗组使用改变病情抗风湿药物(DMARD)及激素泼尼松7.5 mg/d,对照组给予DMARDs。观察和比较两组患者在不同治疗时间的临床缓解情况及不良反应的发生率。结果:最终49例患者完成实验(治疗组22例,对照组27例)。治疗第12周时,治疗组的DAS28评分显著低于对照组,差异有统计学意义(P0.05);治疗24、48周时,两组的DAS28评分比较均无统计学差异(P0.05)。在治疗第12周时,治疗组的ACR20达标率显著高于对照组(P0.05);在治疗第24、48周时,两组的的ACR20达标率相比无统计学差异(P0.05)。治疗12、24周时,两组体重增加的发生率比较无统计学差异(P0.05)。但在治疗48周时,治疗组体重增加的发生率显著高于对照组(P0.05);两组胃肠不适及血压升高的发生率相近,且均未发现血糖升高的患者。结论:与单纯使用DMARDs相比,长期(大于24周)应用小剂量激素对RA患者临床症状的缓解作用不明显,但安全性尚可。 相似文献
937.
Xia Xin Qian Tian Guangkun Yin Xiaoling Chen Jinmei Zhang Sophia Ng Xinxiong Lu 《Journal of plant physiology》2014
The effect of artificial ageing on the relationship between mitochondrial activities and the antioxidant system was studied in soybean seeds (Glycine max L. cv. Zhongdou No. 27). Ageing seeds for 18 d and 41 d at 40 °C reduced germination from 99% to 52% and 0%, respectively. In comparison to the control, malondialdehyde content and leachate conductivity in aged seeds increased and were associated with membrane damage. Transmission electron microscopy and Percoll density gradient centrifugation showed that aged seeds mainly contained poorly developed mitochondria in which respiration and marker enzymes activities were significantly reduced. Heavy mitochondria isolated from the interface of the 21% and 40% Percoll were analyzed. Mitochondrial antioxidant enzymes activities including superoxide dismutase, ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehydroascorbate reductase were significantly reduced in aged seeds. A decrease in total ascorbic acid (ASC) and glutathione (GSH) content as well as the reduced/oxidized ratio of ASC and GSH in mitochondria with prolonged ageing showed that artificial ageing reduced ASC–GSH cycle activity. These results suggested an elevated reactive oxygen species (ROS) level in the aged seeds, which was confirmed by measurements of superoxide radical and hydrogen peroxide levels. We conclude that mitochondrial dysfunction in artificially aged seeds is due to retarded mitochondrial and ASC-GSH cycle activity and elevated ROS accumulation. 相似文献
938.
目的:通过注射低剂量四氯化碳( carbon tetrachloride ,CC14)建立B/C小鼠肝损伤模型。方法正常B/C小鼠随机分为正常对照组、油对照组、CCl4模型组。正常对照组常规饲养;油对照组腹腔注射鲁花花生油(10μL/g,1次/3天,连续6周);CC14模型组腹腔注射0.5%CC14(10μL/g,1次/3天,连续6周)。第6周,各组小鼠检测血清AST、ALT浓度,HE及Masson染色后观察小鼠肝脏结构、细胞形态及纤维化程度。结果第6周CCl4模型组小鼠血清ALT(P=0.00)、AST(P=0.00)浓度极显著性增高,HE及Masson染色显示CCl4模型组小鼠肝上皮细胞呈广泛性空泡样变及大量坏死,肝小叶内出现明显的条索样纤维增生,其纤维化程度评分显著性升高(P =0.00),纤维显色积分光密度值极显著性增高(P =0.00)。结论注射低剂量CCl4可以诱导B/C小鼠肝损伤模型,实验模型具备肝损伤和肝纤维化病理特征。 相似文献
939.
ExAblate 2000 MRgFUS system (InSightec) installed in Ospedale Maggiore Niguarda Ca' Granda (Milano, Italy) is currently used to treat uterine fibroids. Through the magnetic resonance thermometry (PRF method), it is possible to monitor the temperature in the target in real-time and compute the treated region calculating the thermal dose. The purpose of this work is to investigate the errors in the temperature measurements and their effect on thermal dose. A low pass filtering of temperature maps is proposed to reduce the errors and therefore to improve the reliability of the treated regions calculated.The PRF method was studied through a calibration experiment on ex vivo pig muscle. The outcome resulted to be a very good linearity (p value 0.03) between phase and temperature in the range of interest, and an α value of −0.0109 ± 0.0002 ppm/°C. Temperature statistical uncertainty was evaluated by analyzing the temperature readout variability in specific gel provided by InSightec for daily quality assurance control. It resulted to be 1.89 ± 0.32 °C.A Monte Carlo simulation of the MRI temperature measurement and thermal dose calculations in our specific conditions of geometry and statistical uncertainty revealed that a low-pass filtering process on each temperature map can strongly reduce systematic errors in thermal dose evaluations (1.11 overestimation factor instead of 2.62 without filter); consequently the systematic errors on the size of the predicted ablated area are reduced as well. 相似文献
940.