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   8754篇
  免费   1483篇
  国内免费   1808篇
化学   7133篇
晶体学   240篇
力学   435篇
综合类   119篇
数学   999篇
物理学   3119篇
  2024年   19篇
  2023年   99篇
  2022年   231篇
  2021年   258篇
  2020年   291篇
  2019年   306篇
  2018年   258篇
  2017年   327篇
  2016年   399篇
  2015年   466篇
  2014年   524篇
  2013年   663篇
  2012年   754篇
  2011年   852篇
  2010年   694篇
  2009年   624篇
  2008年   726篇
  2007年   632篇
  2006年   589篇
  2005年   529篇
  2004年   405篇
  2003年   360篇
  2002年   391篇
  2001年   323篇
  2000年   266篇
  1999年   219篇
  1998年   141篇
  1997年   115篇
  1996年   70篇
  1995年   77篇
  1994年   50篇
  1993年   51篇
  1992年   47篇
  1991年   53篇
  1990年   32篇
  1989年   26篇
  1988年   30篇
  1987年   23篇
  1986年   22篇
  1985年   18篇
  1984年   12篇
  1983年   12篇
  1982年   15篇
  1981年   10篇
  1980年   9篇
  1979年   4篇
  1978年   6篇
  1975年   4篇
  1957年   2篇
  1936年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
物理实验教学与中学生辩证逻辑思维能力的培养   总被引:1,自引:1,他引:0  
阐述了如何在辩证逻辑基本规律——对立统一规律指导下,通过挖掘物理实验中蕴涵的辩证逻辑思维素材,在物理实验教学中有意识地培养学生的辩证逻辑思维能力。  相似文献   
72.
戴耀东  王林  杨亚新  何云  黄红波  夏元复 《中国物理》2004,13(10):1652-1656
The polycrystalline sample of layered compound FePS_3 has been investigated by using M?ssbauer spectroscopy (12K to 300K), magnetic susceptibility measurements, x-ray diffraction and FTIR spectroscopy. The antiferromagnetic order exists below T_N=120.5±1K. The M?ssbauer spectra below T_N indicate that the magnetization axis is perpendicular to the layer of FePS_3, and the divalent iron cations are in their high spin configurations. By fitting the hyperfine field parameters near the Néel temperature, we obtain information on the nature of magnetic interactions in the material. The results show that the magnetic coupling can be treated by the two-dimensional Ising model, and it can be interpreted on the basis of a crystal-field effect.  相似文献   
73.
Combining color imaging with phase shifting, a technique named five-step color phase shifting is presented to determine the whole-field isoclinic parameter. Relevant theory is derived and explicit conditions for directly determining the isoclinic parameter in the range of [0,π/2] are given. The unloaded light intensity of the model is systematically studied. A color camera recorded five isoclinic images coupled with isochromatics from a plane polariscope with five different settings, respectively. Experiments have been carried out with a circular disk under diametral compression and errors have been analyzed and estimated. This technique utilizes white light, which avoids undefined isoclinics near the locations where the isochromatics exist and will have active effect on experimental stress analysis and structural strength design.  相似文献   
74.
王伶俐  云大真 《应用光学》1991,12(1):47-50,27
对用Talbot效应及云纹干涉法测试镜面反射体曲率和斜率的灵敏度进行了分析,同时给出了由于光栅稀密对测试的影响和相应的解释。这对从事这项工作或工程上利用此技术测试物体曲率和斜率提供了一个可行的方案。  相似文献   
75.
Water-soluble fullerenes not only have a number of important applications in biological chemistry1, but also form ordered aggregate structures that can be utilized in materials science2. There are reports that some water-soluble fullerene derivatives can form ordered structures in water, such as vesicle, nanorod and nanoparticle2-5. However, relatively few reports on the aggregation process have been reported. Knowledge of factors that affect the cluster formation in solution is of consider…  相似文献   
76.
Frame Wavelets with Compact Supports for L^2(R^n)   总被引:1,自引:0,他引:1  
The construction of frame wavelets with compact supports is a meaningful problem in wavelet analysis. In particular, it is a hard work to construct the frame wavelets with explicit analytic forms. For a given n × n real expansive matrix A, the frame-sets with respect to A are a family of sets in R^n. Based on the frame-sets, a class of high-dimensional frame wavelets with analytic forms are constructed, which can be non-bandlimited, or even compactly supported. As an application, the construction is illustrated by several examples, in which some new frame wavelets with compact supports are constructed. Moreover, since the main result of this paper is about general dilation matrices, in the examples we present a family of frame wavelets associated with some non-integer dilation matrices that is meaningful in computational geometry.  相似文献   
77.
In this contribution, we demonstrate a new effective methodology for constructing highly efficient and durable poly(p‐phenyleneethynylene) (PPE) containing emissive material with nonaggregating and hole‐facilitating properties through the introduction of hole‐transporting blocks into the PPE system as the grafting coils as well as building the energy donor–acceptor architecture between the grafting coils and the PPE backbone. Poly(2‐(carbazol‐9‐yl)ethyl methacrylate) (PCzEMA), herein, is chosen as the hole‐transporting blocks, and incorporated into the PPE system as the grafting coils via atom transfer radical polymerization. The chemical structure of the resultant copolymer, PPE‐g‐PCzEMA, was characterized by NMR and gel permeation chromatography, showing that the desirable copolymer was obtained with the narrow polydispersity. The increased thermal stability of PPE‐g‐PCzEMA was confirmed by thermogravimetric analysis and differential scanning calorimetry along with its macroinitiator. The optoelectronic properties of this copolymer were studied in detail by ultraviolet‐visible absorption, photoluminescence emission and excitation spectra, and cyclic voltammogram (CV). The results indicate that PPE‐g‐PCzEMA exhibits the solid‐state luminescent property dominated by individual lumophores, and also the energy transfer process from the PCzEMA blocks to the PPE backbone with a relatively higher energy transfer efficiency in the solid‐state compared to that of the solution state. Additionally, the hole‐injection property is greatly facilitated due to the presence of PCzEMA, as confirmed by CV profiles. All these data indicate that PPE‐g‐PCzEMA is a good candidate for use in optoelectronic devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3776–3787, 2007  相似文献   
78.
一种新型有机电致微腔结构的双模发射   总被引:4,自引:4,他引:0  
采用结构Glass/DBR/ITO/NPB/NPB:Alq/Alq/Al制作了有机微腔电致发光器件。将空穴传输材料与发光材料以一定比例混合作为发光层,为了便于对比,在不改变有机层的膜厚的情况下同时制作了传统的异质结微腔器件,发现两种器件的发光光谱有很大不同,器件的复合效率与传统的异质结器件相比也得到了很大提高,这是因为将两种有机材料混合能消除界面势垒,提高器件的复合效率,从而提高了器件的发光性能,实现了微腔双模发射,且两个模式的半峰全宽分别为8nm和12nm。通过进一步优化器件结构可以实现微腔白光发射。  相似文献   
79.
在酸性条件下,采用乙酸乙酯萃取、Na2HPO4溶液反萃取分离酱汪、食醋中的山梨酸、苯甲酸,卡尔曼滤波法计算结果,并与比值导数波谱法进行比较。结果表明,卡尔曼滤波法较地数波谱法有较高准确度和精密度,并能监测干扰物质存在与否。用于实际样品分析有更高的可靠性。  相似文献   
80.
唐云 《应用数学》1991,4(1):70-74
本文利用角动量作为Liapunov函数建立二维的圆形涡块及涡环在有限或无限区域上的(Liapunov)非线性稳定性.  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