全文获取类型
收费全文 | 4620篇 |
免费 | 601篇 |
国内免费 | 334篇 |
专业分类
化学 | 458篇 |
晶体学 | 7篇 |
力学 | 160篇 |
综合类 | 188篇 |
数学 | 2418篇 |
物理学 | 2324篇 |
出版年
2024年 | 12篇 |
2023年 | 38篇 |
2022年 | 286篇 |
2021年 | 266篇 |
2020年 | 147篇 |
2019年 | 125篇 |
2018年 | 104篇 |
2017年 | 162篇 |
2016年 | 194篇 |
2015年 | 143篇 |
2014年 | 261篇 |
2013年 | 305篇 |
2012年 | 207篇 |
2011年 | 252篇 |
2010年 | 245篇 |
2009年 | 274篇 |
2008年 | 268篇 |
2007年 | 316篇 |
2006年 | 249篇 |
2005年 | 242篇 |
2004年 | 210篇 |
2003年 | 175篇 |
2002年 | 155篇 |
2001年 | 115篇 |
2000年 | 91篇 |
1999年 | 88篇 |
1998年 | 85篇 |
1997年 | 73篇 |
1996年 | 57篇 |
1995年 | 67篇 |
1994年 | 44篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有5555条查询结果,搜索用时 15 毫秒
81.
针对我国医患关系日趋紧张,医患矛盾逐渐凸显这一问题,在对中国近五年医患事件进行分析的基础上,分别从信任程度、信息不对称程度、诊疗代价等多个视角出发,利用演化博弈理论和复制动态方程,构建了医患双方合作策略选择演化博弈模型,探究了影响医患关系演化的相关因素。研究表明:从长期来看,医患关系博弈系统存在两种演化路径:主动合作和被动合作;增大医患双方的信任程度,减小医患双方的信息不对称程度,降低医患双方合作成本,增大以政府为主导的仲裁机构对医患双方的奖励和惩罚都将会促使医患双方由被动合作转向主动合作。 相似文献
82.
Kenneth W. Mihavics Aris M. Ouksel 《Computational & Mathematical Organization Theory》1996,1(2):143-155
The relationship between organizational learning and organizational design is explored. In particular, we examine the information processing aspects of organizational learning as they apply to a two-valued decision making task and the relation of such aspects to organizational structure. Our primary contribution is to extend Carley's (1992) model of this process. The original model assumes that all data input into the decision making processes are of equal importance or weight in determining the correct overall organizational decision. The extension described here allows for the more natural situation of non-uniform weights of evidence. Further extensions to the model are also discussed. Such organizational learning performance measures provide an interesting framework for analyzing the recent trend towards flatter organizational structures. This research suggests that flatter structures are not always better, but rather that data environment, ultimate performance goals, and relative need for speed in learning can be used to form a contingency model for choosing organizational structure. 相似文献
83.
In the presence of palladium complexes as catalysts, fluorinated disilanes add to 1,3-dienes, metehyl vinyl ketone and p-benzoquinone to give mainly 1,4-addition products. 相似文献
84.
A pyrryl substituted photocbromic fulgide, (1-p-methoxyphenyl-2-methyl-5-phenyl)-3-pyrryl-ethylidene (isopropylidene) succinic anhydride, was synthesized. Its chemical structure was identified by IR, 1H NMR MS and elemental analysis. The title compound was used to prepare the optical disks by the spin coating method and the vacuum evaporation method. The results of the static state examination show that the optical disks prepared with this kind of molecules possess excellent thermal stability and fatigue resistance, i.e. over 450 writing-erasing recycles, the relative contrast between writing state and erasing state remains at 40%. 相似文献
85.
基于支持向量机的羰基化合物红外光谱研究 总被引:1,自引:0,他引:1
设计了一个4层分等级分类系统,通过支持向量机技术对羰基化合物的红外光谱成功地进行了信息分类和提取,并与人工神经网络进行比较,结果表明:支持向量机对羰基类化合物红外光谱分类效果优于人工神经网络;另外详细探讨了表征酰胺类化合物的特征光谱峰片段对识圳伯仲叔酰胺的影响,证明了酰胺的N-H伸缩振动峰对识别伯仲叔酰胺贡献最大,为构建红外光谱智能解析系统提供了定量依据。 相似文献
86.
PiezoelectricFiber-opticSpectroelectrochemistry──ANewTechniqueofSpectroelectrochemistryinCombinationWithPiezoelectricQuartzCr... 相似文献
87.
Titrimetric determinations of arenediazonium salts can be based on ion-pair formation between the diazonium cation and tetraphenylborate. Titrations are done under cooling with ice and are followed potentiometrically with organic ion-selective electrodes comprising PVC membranes plasticized with polar solvents and coated on aluminium wires. The method was tested in determinations of arenediazonium salts derived from 20 aromatic amines, including aniline, toluidines, naphthylamines and their derivatives. Except for compounds containing hydrophylic groups such as —COOH and —OH, the potentiometric titration curves have well defined end-points. The results are reproducible, with relative standard deviations in the range 0.4–1.4% at the millimolar level. The method can be used for reliable determinations of arenediazonium salts in analytical control of azo dyestuff production. 相似文献
88.
A phase diagram of pinned soliton structures in two dimensions has been found for a repulsive interactionU(x) between solitons withU(x)>0. The critical fugacity of the commensurate soliton structure is shown to be proportional toU(l), wherel is the period of this structure. 相似文献
89.
从光干涉方式,瞳窗关系和光源带宽等基本关系出发,利用空间不变系统理论解析了相移显微干涉检测系统中衍射效应的影响。为了减小横向分辨率对纵向分辨率的影响,利用相关信息提取或数字滤波的方法,获得了纳米分辨率的三维形貌。 相似文献
90.
信息拓扑指数与烷烃分子热力学性质的关系 总被引:13,自引:0,他引:13
Two topological information indices were constructed based on Randic and Wiener indices, and the values of topological information indices for 85 alkanes were calculated. The thermodynamic properties such as the standard enthalpies of formation, the standard entropies and the standard free energies of formation for these alkanes were also correlated with these topological and information indices. It is found that the thermodynamic properties calculated for both gaseous and liquid states of the 85 alkanes are in excellent agreement with the experimental values through the regression analysis. 相似文献