全文获取类型
收费全文 | 1521篇 |
免费 | 168篇 |
国内免费 | 90篇 |
专业分类
化学 | 816篇 |
晶体学 | 12篇 |
力学 | 128篇 |
综合类 | 131篇 |
数学 | 431篇 |
物理学 | 261篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 100篇 |
2021年 | 82篇 |
2020年 | 82篇 |
2019年 | 95篇 |
2018年 | 64篇 |
2017年 | 77篇 |
2016年 | 64篇 |
2015年 | 35篇 |
2014年 | 56篇 |
2013年 | 80篇 |
2012年 | 64篇 |
2011年 | 83篇 |
2010年 | 64篇 |
2009年 | 80篇 |
2008年 | 67篇 |
2007年 | 55篇 |
2006年 | 74篇 |
2005年 | 60篇 |
2004年 | 64篇 |
2003年 | 59篇 |
2002年 | 38篇 |
2001年 | 46篇 |
2000年 | 37篇 |
1999年 | 36篇 |
1998年 | 28篇 |
1997年 | 24篇 |
1996年 | 19篇 |
1995年 | 24篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有1779条查询结果,搜索用时 15 毫秒
101.
102.
103.
Shin Kikuchi Naoki Kozuka Eiji Uchida Takafumi Ninomiya Haruyuki Tatsumi Hidekatsu Takeda Nobutada Tachi 《Physical Therapy Research》2008,11(1):23-27
Myotonic dystrophy (MyD) is a neuromuscular disease that is autosomal dominant and the most common form of muscular dystrophy affecting adults. The clinical features of MyD include a multisystemic disorder characterized by myotonia, progressive muscle weakness and wasting, cataracts, premature balding and mental retardation. The most severe type of MyD is classified as congenital MyD (CMyD). The muscle weakness in CMyD is very severe, but muscle development can be observed in the period of growth. However, no clinical case of this type has been reported yet. Therefore, we report on a girl with CMyD who had an increase in muscle strength over a four-year period. The girl with CMyD participated in this study from the age of 9 to the age of 12. The measurement of muscle strength was recorded as the maximum score of grip strength with the use of dynamometers. Grip strength was assessed once a year by the same two physical therapists. Grip strength of CMyD for each year was markedly weak when compared with the normal controls, but muscle strength changed within some specific growth areas. The muscle weakness in CMyD was remarkable, but the result showed that specific muscle strength of CMyD in childhood was actually increased. 相似文献
104.
W. Kleiböhmer 《Accreditation and quality assurance》1999,4(12):517-520
Maintaining a high quality of research and development (R&D) is fundamental for the competitiveness of European industry.
The development of new technologies and the improvement of existing technologies, products, production processes, measurement
instrumentation and methods as well as basic research is essential. The objective of the workshop on "Quality Management in
Analytical Chemical Research and Development" was to bring together experts from the academic world, industrial and institutional
laboratories and also accreditation bodies to discuss the actual state of the art in the field of quality management in R&D,
and to set up milestones for further activities. Furthermore, an important objective was to present the EURACHEM/CITAC Guide
2. The paper outlines the programme of the workshop and summarises the round-table discussions and expert recommendations.
Most of the contributions to the round-table discussions will be published as full papers in a forthcoming issue of Accreditation
and Quality Assurance. The workshop was organised by the Institut für Chemo- und Biosensorik (ICB), Münster, with the financial
support of the SMT-Programme of the European Commission (Contract No.: SMT4-CT98-6534). 相似文献
105.
Dragana Vasiljevic Jelena Djuris Sergej Jakimenko Svetlana Ibric 《Journal of Dispersion Science and Technology》2017,38(12):1732-1737
In presented research, multiple W/O/W emulsions were developed by using experimental design method. A 24-1 fractional factorial design was performed by varying the following input parameters: primary polymeric emulsifier (PEG 30-dipolyhydroxystearate) concentration (0.8% and 2.4%), secondary polymeric emulsifier (Poloxamer 407) concentration (0.8% and 1.2%), electrolyte magnesium sulfate heptahydrate (0.08% and 0.4%) and electrolyte sodium chloride (0.08% and 0.4%). Multiple emulsions were prepared by a two-step emulsification process. Obtained emulsions were characterized with rheological measurements, conductivity and centrifugation tests. Factorial analysis revealed that the concentration of the primary emulsifier was the predominant factor influencing the phase separation, conductivity and maximal apparent viscosity. Additionally, electrolyte magnesium sulfate heptahydrate was more efficient in stabilizing these systems, compared to sodium chloride. The applied fractional factorial design method enabled determination of the optimal concentrations of the primary and secondary emulsifier, as well as the concentration of electrolytes, in order to obtain W/O/W emulsions with desired maximal apparent viscosities, low values of conductivity and without phase separation after centrifugation. 相似文献
106.
新冠肺炎疫情对广州港的货运发展产生了一定程度的影响,但目前仍然缺少相关的定量研究.基于灰色预测模型,利用港口货物吞吐量、外贸货物吞吐量、集装箱吞吐量三个货运指标,在新冠肺炎疫情没发生的这一假设下,推测2020年1-8月广州港的各货运发展指标值.基于预测值与实际值的比较,定量研究广州港的货运发展受新冠肺炎的影响值,反映新... 相似文献
107.
区域低碳协同发展评价:京津冀、长三角和珠三角城市群的比较分析 总被引:1,自引:0,他引:1
京津冀、长三角和珠三角城市群是中国经济高度发达、最具发展潜力的区域,在低碳发展方面起到引领作用.从经济、资源、环境和绩效的角度构建区域低碳协同发展评价指标体系,采用结合逼近理想解的TOPSIS方法、灰色关联理论和距离协同模型,利用2005~2014年三大城市群50个城市数据实证分析了三大城市群的低碳协同发展程度.结果表明,三大城市群低碳协同发展度整体上呈现上升趋势,其低碳协同程度从高到底依次为长三角、珠三角和京津冀城市群. 相似文献
108.
探讨了经济增长及金融发展与城乡收入差距之间互动影响,刻画了三者间的逻辑关系,并基于广西1990-2017年的统计数据,运用状态空间模型及卡尔曼滤波算法对三者间动态关系进行了实证分析.结果显示:经济增长对城乡收入差距呈现倒U型曲线形态,而金融发展则显示出具有不断缩小城乡收入差距的趋势. 相似文献
109.
西部开发中能源配置模型的研究 总被引:3,自引:0,他引:3
开发西部丰富的能源资源,解决东部地区能源紧缺的矛盾,是东西部经济合作、优势互补、东西联动双赢战略研究的一项重要课题.在国家投资主体和市场经济条件下,以能源消费效益最大为目标,建立了基于边际效益均衡的能源空间配置优化模型;兼顾经济效益与环境效益的能源部门配置优化模型.结果显示,各地区、部门要获得更多的能源,就必须提高能源的使用效率,提高能源消费的边际效益,降低污染排放水平. 相似文献
110.
区域3E系统协调发展水平PLS-SEM测度模型及应用研究 总被引:1,自引:0,他引:1
在总结现有3E系统协调发展水平测度方法缺陷的基础上,提出了基于PLS-SEM方法的3E系统协调发展水平测度模型,并从总量、结构和质量三个维度构建了3E系统指标体系,最后测度了1978年到2008年中国3E整体系统及各子系统的协调发展水平。研究表明:(1)PLS-SEM模型能有效弥补现有测度方法的缺陷,适应于3E系统协调发展水平的测度;(2)考察期内中国3E整体系统及各子系统协调发展水平呈递增的态势,其中经济子系统增长较快,也是3E整体系统协调发展水平增长的重要保证;(3)系统的总量维度隐变量对3E系统协调发展水平变动的影响最大,质量维度和结构维度隐变量均较小,说明中国社会经济的发展仍未摆脱粗放式的增长模式。 相似文献