全文获取类型
收费全文 | 1677篇 |
免费 | 477篇 |
国内免费 | 158篇 |
专业分类
化学 | 104篇 |
晶体学 | 29篇 |
力学 | 183篇 |
综合类 | 117篇 |
数学 | 710篇 |
物理学 | 1169篇 |
出版年
2024年 | 23篇 |
2023年 | 58篇 |
2022年 | 51篇 |
2021年 | 52篇 |
2020年 | 38篇 |
2019年 | 71篇 |
2018年 | 32篇 |
2017年 | 74篇 |
2016年 | 71篇 |
2015年 | 87篇 |
2014年 | 160篇 |
2013年 | 100篇 |
2012年 | 106篇 |
2011年 | 110篇 |
2010年 | 117篇 |
2009年 | 127篇 |
2008年 | 124篇 |
2007年 | 116篇 |
2006年 | 98篇 |
2005年 | 117篇 |
2004年 | 79篇 |
2003年 | 86篇 |
2002年 | 78篇 |
2001年 | 52篇 |
2000年 | 48篇 |
1999年 | 37篇 |
1998年 | 33篇 |
1997年 | 23篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有2312条查询结果,搜索用时 31 毫秒
71.
<正>An optical fiber evanescent wave methane gas sensor based on core diameter mismatch is reported.The sensor consists of a multimode fiber in which a short section of standard single-mode fiber,coated with the inclusion of cryptophane molecules E in a transparent polysiloxane film,is inserted.The sensing principle is analyzed by optical waveguide theory.For different sensing film thicknesses and interaction lengths,the sensor signal is investigated within the methane concentration range of 0-14.5%(v/v).It is shown that the sensor signal with the thickness of 5μm and the interaction length of 3 mm strengthens linearly with the increasing concentration of methane,with a slope of 0.0186.The best detection limit of the sensor for methane is 2.2%(v/v) with a response time of 90 s.This sensor is suitable for the detection of methane concentration below the critical value of 5%. 相似文献
72.
我们从减弱文Vestfrid[1]中定理3中空间一致凸条件和加强ε-等距算子条件着手去研究Banach空间中几乎满的ε-等距算子的等距逼近问题.另外,我们结合完备的β-范(0〈β〈1)空间的性质得到一些相关结论. 相似文献
73.
74.
LiuYan YuanJinjiang WangShiying 《高校应用数学学报(英文版)》2000,15(1):1-6
Abstract. A simple graph G is induced matching extendable,shortly IM-extendable,if every in-duced matching of G is included in a perfect matching of G. The degree conditions of IM-extend-able graphs are researched in this paper. The main results are as follows: 相似文献
75.
该文证明了随机元序列的一个一般的几乎处处中心极限定理, 并把这一结论应用于随机变量序列的函数. 相似文献
76.
77.
利用图论和代数的方法研究离散几何中的两个铺砌问题:1)给出1×2长方形铺砌多米诺骨牌的充分必要条件;2)对高维空间盒子的情形,给出m_1×m_2×…×m_n砖能够铺砌a_1×a_2×…×a_n盒子的一些必要条件和充要条件. 相似文献
78.
79.
80.
Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation 下载免费PDF全文
The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm (diameter) polystyrene. The liquid mixtures, in the proper proportions of water (H2O), deuterium oxide (D2O) and methanol (MeOH) as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes (reduction) in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable. 相似文献