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   317篇
  免费   30篇
  国内免费   9篇
化学   163篇
力学   1篇
综合类   3篇
数学   78篇
物理学   26篇
无线电   85篇
  2023年   5篇
  2022年   18篇
  2021年   16篇
  2020年   19篇
  2019年   12篇
  2018年   16篇
  2017年   7篇
  2016年   19篇
  2015年   22篇
  2014年   24篇
  2013年   29篇
  2012年   19篇
  2011年   15篇
  2010年   11篇
  2009年   20篇
  2008年   11篇
  2007年   10篇
  2006年   12篇
  2005年   14篇
  2004年   10篇
  2003年   7篇
  2002年   10篇
  2001年   3篇
  2000年   6篇
  1999年   1篇
  1998年   4篇
  1997年   3篇
  1996年   4篇
  1994年   2篇
  1992年   2篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1984年   1篇
  1976年   1篇
排序方式: 共有356条查询结果,搜索用时 31 毫秒
1.
褪黑激素与HNO3在室温下发生硝基化反应生成褪黑激素的硝基化合物,加NH3·H2O终止反应并用甲酸 甲酸钠缓冲液控制反应液pH3,在原点电位-0.20V(vs.SCE),测量-0.50V处的二阶导数峰高。方法检出限为1μg/L,线性范围为1μg/L~200μg/L,相对标准偏差为2.6%~8.0%,加标回收率为92 0%~110 0%,测定结果与高效液相色谱法进行比较,无显著性差异。  相似文献   
2.
A study has been carried out aimed at reducing perinatal mortality in the municipality of Rio de Janeiro through a better distribution of health care facilities. The algorithmic aspects are detailed elsewhere and here the emphasis is on practical issues and difficulties encountered. A 3-level hierarchical model was developed. Both uncapacitated and capacitated versions are briefly described together with some results based on actual data. The project brought to light many contradictions between OR theory and practice in developing countries and, unfortunately, the models developed were not implemented by the municipality health authorities. Possible reasons for this outcome are analysed.  相似文献   
3.
本详细描述了移动IP的工作过程,并介绍了移动IP的隧道技术和IPSec,最后对移动IP技术中存在几个热点问题进行了讨论。  相似文献   
4.
远红外织物的保健性能   总被引:5,自引:2,他引:3  
远红外织物是80年代中期研究开发出的一种通过高效吸收和发射远红外线而具有改善微循环、促进血液循环等功能的新型纺织品。本文通过研究实例综述了国内外近年来对远红外织物保健性能的研究成果。  相似文献   
5.
基于磁性纳米材料的磁标记检测技术具有灵敏度高、线性范围广、信号检测便捷等优点。由于生物样品自身磁背景信号极低,相比于光学标记检测技术,磁标记检测技术在蛋白质、核酸、细胞、病原体及生物组织检测中均表现出更高的灵敏度,在生物医学即时检测领域展现了良好的应用前景。该文围绕磁性纳米粒在即时检测领域的最新研究进展,重点介绍了其在蛋白质、核酸以及几类病原体检测方面的应用,并对基于磁性纳米粒的即时检测技术发展方向及应用前景进行了展望。  相似文献   
6.
The results of low temperature heat capacity studies on Mn2(CO)10(s) and Re2(CO)10(s) are compared with literature reports. It is shown that the values of vaporization enthalpies and entropies correspond with those of the low temperature stable phase.  相似文献   
7.
崔晓  程敏  敦帅 《运筹与管理》2022,31(10):61-67
考虑政府补贴、市场化程度、养老机构服务成本、老年人偏好等因素,构建了完全国有化、公私并存的半市场化和完全市场化三种情形下公办和民办养老机构之间的两阶段博弈模型,比较分析了市场化程度对养老机构服务价格制定和服务水平选择的影响,实证讨论了各参数变化对养老机构收益及社会福利的影响。研究表明:完全市场化机制会降低养老机构服务质量,完全国有化机制会陷入社会福利陷阱,探索公私并存的最佳市场化水平才能更好地提高社会福利;适度推进市场化改革,提高养老机构服务水平,降低民办养老机构服务成本,适度提高对民办养老机构的补贴,将有效缓解公办和民办养老机构的不公平竞争;提高老年人支付能力,推进养老机构供给侧结构性改革,将保障机构养老服务的有效供给,促进养老服务业的健康有序发展。  相似文献   
8.
Many medical professionals are involved in patient care processes. For pharmaceutical care this results in many information transfer moments. To provide optimal care, communication and information the transfer should be conducted in a timely manner, fully transparent, complete and relevant. The TRANSFORM project is directed towards the development of a reference information model of the pharmaceutical care chain with the aim to improve the availability (time, place, completeness) and access of pharmaceutical information regarding patients, thereby resulting in continuity and quality of pharmaceutical care, reduction in medical errors and improvement in patient safety through the design of a safer healthcare system. TRANSFORM leads to improved insight into the processes and data transfer points in the pharmaceutical chain of care. Focussed on laboratory medicine and pharmacy, the implementation of the integration of laboratory test and pharmacy information may result in major improvements in drug therapy monitoring and guidance (i.e. drug impact monitoring). Because of the overwhelming amount of data generated by this integration of drugs, drug effects and laboratory test results, an online decision support system is warranted.Presented at the 9th Conference on Quality in the Spotlight, 18–19 March 2004, Antwerp, Belgium.The following paper may appear at first sight not to be specifically within the realm of ACQUAL. It has been accepted for publication anyway as it is about reliable handling of data, incl. measurement results, which lead to important decisions (in this case related to a patient). The reliability of handling (a large amount of) measurement results towards a basis for important decisions, is a very important feature of the use of such results.Paul De Bièvre, Editor in Chief  相似文献   
9.
We report a method to detect proteins via suppression of rolling circle amplification (RCA) by using an appropriate aptamer as the linear primer (denoted as an aptaprimer) to initiate RCA. In the absence of a protein target, the aptaprimer is free to initiate RCA, which can produce long DNA products that are detected via binding of a fluorescent intercalating dye. Introduction of a target causes the primer region within the aptamer to become unavailable for binding to the circular template, inhibiting RCA. Using SYBR Gold or QuantiFluor dyes as fluorescent probes to bind to the RCA reaction product, it is possible to produce a generic protein-modulated RCA assay system that does not require fluorophore- or biotin-modified DNA species, substantially reducing complexity and cost of reagents. Based on this modulation of RCA, we demonstrate the ability to produce both solution and paper-based assays for rapid and quantitative detection of proteins including platelet derived growth factor and thrombin.  相似文献   
10.
The time spent in dependence and the type of care an elderly receives are the two main cost drivers of long-term care (LTC). We aim to provide a better understanding of the duration of care by using a comprehensive social insurance dataset covering the LTC needs in Switzerland over a 20-years-period and including 230 000 observations on dependent elderly. First, using the framework of survival analysis, we calculate Kaplan–Meier estimates for the care duration and derive the main explaining factors through econometric models when care is received at home and in an institution. Retaining only significant covariates, the final accelerated failure time models allow us to predict the duration for different profiles of elderly along their age, gender, region of residence, type of household composition, acuity level and pre-retirement income. Second, we study the interaction of care durations when care is provided at home and in an institution. While our data supports that for short at-home care durations the time spent in institutional care is reduced, we find that both types of care are non-substitutes when the time spent at home has been longer. Under the latter regime, the time spent in institutional care remains at a constant level. Finally, given the longevity improvements over the period of observation, we analyze the impact of living longer on the time spent in dependence. Our results show that while the mean age at entry in dependence grows, the overall care duration does not significantly change. Given the expected increasing number of elderly in most developed countries, our study is relevant for government planning, budgeting social insurance schemes, estimating personal savings needs and calculating private insurance premiums.  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