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91.
古地磁或稳定同位素方法为提高沉积物定年精度提供了可能,但若将两种方法在很多地点大范围应用是不可能的。本文采用了来自黄河中游河流阶地的黄土磁化率数据,建立一种与海洋氧同位素记录相互关联的年代一深度关系,并且为黄土堆积物提供了一种较高精度相对定年方法。 相似文献
92.
Complexation of π-conjugated ligands by metal or semimetal ions leads to the enhancement of the planarity and rigidity of π-conjugated systems. Boron, especially, has played a central role in the design of luminescent main-group complexes. However, these complexes still suffer the disadvantage of aggregation-caused quenching as well as typical organic fluorophores. It has recently been reported that some types of boron complexes exhibit the aggregation-induced emission (AIE) property. Moreover, AIE behavior from complexes and organometallic compounds composed of the other group 13 elements, such as aluminum and gallium, has emerged in this decade. These observations greatly encourage us to develop advanced functional materials based on the group 13 elements. Indeed, recent research has demonstrated that these classes of materials are potentially versatile scaffolds for constructing chromic luminophores, efficiently emissive π-conjugated polymers and so on. This review mainly describes AIE-active group 13 complexes with four-coordinate structures and their application as photo-functional materials. Proposed mechanisms of the origins of AIE behavior are briefly discussed. 相似文献
93.
Jeffery Funk 《Research Policy》2009,38(7):1192-1202
Using the history of magnetic recording and playback equipment, this paper explores the relationship between incremental improvements in components and technological discontinuities in systems. It finds that improvements in components have been the major source of all discontinuities in the industry. Focusing just on tape-based systems, all of the basic design approaches had been identified by the late 1950s and thus one of the largest technological challenges for firms has been to modify the design in response to improvements in the magnetic recording density of tape. This paper explores this phenomenon by analyzing data on equipment performance and price, and several design choices for the tape-based equipment. It shows how improvements in the magnetic recording density have changed the tradeoffs that exist between price and different dimensions of performance and between various design choices and thus led to about 10 technological discontinuities in magnetic tape system design. 相似文献
94.
以二甲基二烯丙基氯化铵(DMDAAC)和丙稀酰胺(AM)为原料,在 引发剂过硫酸铵(APS)的作用下,通过共聚合反应成了一种新的阳离子型聚合物。在n(DMDAA C):n(AM)=2:1、c(APS)=2.0×10-2mol/L、t=60°C、T=3h的条件下,所得共聚物的 阳离子度(CD)为45%,相对分子质量为9.4×106。应用实验结果证明该聚合物具有良好的 絮凝作用,同时对共聚物的结构进行了表征。 相似文献
95.
96.
采用分步聚合法合成了两网质量比不同,第二网交联度均为30%的聚二乙烯基苯/聚丙烯酸甲酯互穿聚合物网络(PDVB-PMA IPN),将它们分别用20%的NaOH/甲醇溶液碱解,合成了一网疏水、一网亲水的聚二乙烯基苯/聚丙烯酸互穿聚合物网络(PDVB-PAA IPN)。测定了两网质量比对树脂的比表面积、平均孔容、孔径以及弱酸交换量的影响。比较了不同树脂对水溶液中苯酚的吸附性能差别,测定了此类树脂的热力学数据,探讨了此类树脂的吸附机理,建立了一种通过溶胀致孔合成吸附树脂的方法。 相似文献
97.
MATLAB提供了一个图形用户界面的偏微分方程的数值求解工具。它包括了数值分析的前处理,计算和后处理等一套完整的程序。本文介绍了电磁场数值分析基本理论并通过实例介绍了使用MATLAB PDE工具箱实现电磁场偏微分方程的有限元解法。仿真结果表明这一方法具有操作简单、快速、准确等优点。 相似文献
98.
利用当前通用的多媒体技术、以多媒体制作工具Authorware为主,其它一些主流的媒体创作工具为辅,制作了高分子化学悬浮聚合实验教学系统。它由7个模块组成,即实验目的模块、实验原理模块、实验设备模块、实验步骤模块、实验问题模块、实验设计模块、退出系统模块。它不仅可以作为高分子化学实验教学使用,又便于学生有效地进行实验的预习和复习。该教学系统使用方便、操作简单、针对性强、是一种较实用的计算机辅助教学工具。 相似文献
99.
100.
Study of clinical features of amyloid angiopathy hemorrhage and hypertensive intracerebral hemorrhage 总被引:3,自引:0,他引:3
詹仁雅 童鹰 沈剑峰 LANG E. PREUL C. HEMPELMANN R.G. HUGO H.H. BUHL R. BARTH H. KLINGE H. MEHDORN H.M 《Journal of Zhejiang University. Science. B》2004,(10)
Objective: The purpose of this study was to differentiate between cerebral amyloid angiopathy (CAA) and hypertension (HTN) based on hemorrhage pattern interpretation. Methods: From June 1994 to Oct., 2000, 83 patients admitted to our service with acute intracerebral hemorrhage (ICH) were investigated retrospectively; 41 patients with his-tologically proven diagnosis of cerebral amyloid angiography and 42 patients with clear history of hypertension were investigated. Results: Patients with a CAA-related ICH were significantly older than patients with a HTN-related ICH (74.0 years vs 66.5 years, P<0.05). There was a significantly higher number of hematomas>30 ml in CAA (85.3%) when compared with HTN (59.5%). No basal ganglional hemorrhage was seen in CAA, but in 40.5% in HTN. In CAA-related ICH, su-barachnoid hemorrhage (SAH) was seen in 26 patients (63.4%) compared to only 11 patients (26.2%) in HTN-related ICH. Intraventricular hemorrhage was seen in 24.4% in CAA, and in 26.2% in HTN. Typical features o 相似文献