全文获取类型
收费全文 | 4601篇 |
免费 | 269篇 |
国内免费 | 1111篇 |
专业分类
化学 | 5210篇 |
晶体学 | 16篇 |
力学 | 154篇 |
综合类 | 48篇 |
数学 | 65篇 |
物理学 | 488篇 |
出版年
2024年 | 21篇 |
2023年 | 55篇 |
2022年 | 166篇 |
2021年 | 188篇 |
2020年 | 202篇 |
2019年 | 141篇 |
2018年 | 118篇 |
2017年 | 143篇 |
2016年 | 188篇 |
2015年 | 159篇 |
2014年 | 177篇 |
2013年 | 300篇 |
2012年 | 330篇 |
2011年 | 221篇 |
2010年 | 238篇 |
2009年 | 314篇 |
2008年 | 439篇 |
2007年 | 277篇 |
2006年 | 309篇 |
2005年 | 277篇 |
2004年 | 234篇 |
2003年 | 198篇 |
2002年 | 144篇 |
2001年 | 132篇 |
2000年 | 143篇 |
1999年 | 109篇 |
1998年 | 106篇 |
1997年 | 107篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 84篇 |
1993年 | 85篇 |
1992年 | 51篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有5981条查询结果,搜索用时 10 毫秒
61.
甲基紫掺杂聚乙烯醇薄膜材料在两束相干光照射下生成相位光栅.当改变一束相干光光程,通过监测相位光栅的一级衍射信号强度的变化,可以检测相位光栅的生长和擦除过程.在此实验基础上,讨论了甲基紫掺杂聚乙烯醇薄膜材料多重全息存储的原理与结果. 相似文献
62.
First quantum correction to entropy of Vaidya-Bonner black holes due to arbitrary spin fields 下载免费PDF全文
Using the improved brick-wall model, we have calculated the first quantum correction to the entropy of non-static black holes, Vaidya-Bonner black holes, due to the gravitational, electro-magnetic and neutrino fields. The result shows that both bosonic entropy and fermionic entropy are exactly proportional to the area of the event horizon. Thus, the entropy-area law still holds in such a non-static case. 相似文献
63.
Han Mo Jeong Ah Young Jo Mi Yeon Choi Man Jae Han Jae Young Jho 《Journal of Macromolecular Science: Physics》2013,52(5):789-799
The characteristics and performance of an ionic polymer–metal composite (IPMC), prepared with an anion‐exchange acrylic copolymer, was examined. The acrylic copolymer was synthesized by the radical copolymerization of fluoroalkyl methacrylate and 2‐(dimethyl amino)ethyl methacrylate(AMA). Effects of the AMA repeating unit's content in the copolymer and effects of the anion type present on the actuation of the IPMC were observed. The optimal content of 19.4 wt% AMA in the IPMC copolymer yielded the best actuation. The actuation also improved according to the type of anion present in the composite, in the following order: Br???4 ?. 相似文献
64.
Early Membrane Responses to Magnetic Particles are Predictors of Particle Uptake in Neural Stem Cells 下载免费PDF全文
Alinda R. Fernandes Christopher F. Adams David N. Furness Divya M. Chari 《Particle & Particle Systems Characterization》2015,32(6):661-667
Magnetic particles (MPs) offer several advantages for neural cell therapy, but limited particle uptake by neural cells is a barrier to translation. It is recently proved that tailoring particle physicochemical properties (by enhancing their iron content) dramatically improves uptake in neural stem cells (NSCs)—a major transplant population. High‐throughput screening of particles with varying physicochemical properties can therefore aid in identifying particles with optimal uptake features, but research is hampered by the lack of simple methodologies for studying neural cell membrane responses to nanoparticle platforms. A high‐resolution–high throughput method has been used to study early membrane responses of primary rodent NSCs to particles of variant magnetite loading, to attempt to correlate these responses with known particle internalization profiles. Membrane imaging is enhanced through sequential staining with osmium (O) and thiocarbohydrazide (T), a method termed OTOTO, combined with field‐emission scanning electron microscopy (FESEM). A five‐point classification system was used to systematically evaluate early MP‐induced membrane responses to particles possessing distinct physicochemical properties. Significantly different profiles of membrane activation were noted that correlate with particle uptake profiles. It is suggested that our method can serve as a valuable predictor of particle internalization in neural cells for diverse particle platforms. 相似文献
65.
66.
67.
避开求解波动方程的困难,利用量子统计的方法,直接计算Kerr-Newman-de Sitter黑洞背景下玻色场和费米场的配分函数.然后利用砖墙膜模型计算和讨论黑洞背景下的玻色场和 费米场的熵.
关键词:
量子统计
砖墙膜模型
Kerr-Newman-de Sitter黑洞
统计熵 相似文献
68.
Synthesis of Nanoscale Bimetallic Particles in Polyelectrolyte Membrane Matrix for Reductive Transformation of Halogenated Organic Compounds 总被引:2,自引:0,他引:2
Nanosized Fe/Ni and Fe/Pd particles were synthesized in the polyacrylic acid (PAA)/polyether sulfone (PES) composite membrane matrix for reductive transformation of halogenated organic compounds (HOCs). The advantages of using membrane to immobilize nanoparticles are the reduction of particles loss, prevention of particles agglomeration, and potential application of convective flow. Cross-linked PAA/PES composite membranes containing metal ions as particles precursor were prepared by heat treatment with ethylene glycol (EG) as a cross-linking agent. Nanoscale metal particles were formed and immobilized inside the membrane matrix after reduction with sodium borohydride. Membrane morphology and structure were observed by scanning electron microscopy (SEM). Particle size and distribution were characterized by SEM and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) was used to obtain the qualitative and quantitative element information of particles. A specimen-drift-free EDS line profile and EDS mapping system was performed in a scanning transmission electron microscopy (STEM) to determine the two-dimensional element distribution of iron and nickel in the nano domain. In the dechlorination study with trichloroethylene (TCE) as a representative HOCs, rapid and complete destruction of TCE was achieved by using nanosized bimetallic Fe/Ni or Fe/Pd in PAA/PES composite membranes. Typically more than 95% of 10 mg/l TCE was reduced within 1 h. Ethane was found in the headspace as the main product. 相似文献
69.
Although there exist a number of methods, such as NMR, X-ray, e.g., which explore the hydration of phospholipid bilayers,
the solvent relaxation (SR) method has the advantage of simple instrumentation, easy data treatment and possibility of measuring
fully hydrated samples. The main information gained from SR by the analysis of recorded “time-resolved emission spectra” (TRES)
is micro-viscosity and micro-polarity of the dye microenvironment. Based on these parameters, one can draw conclusions about
water structure in the bilayer. In this review, we focus on physical background of this method, on all the procedures that
are needed in order to obtain relevant parameters, and on the requirements on the fluorescence dyes. Furthermore, a few recent
applications (the effect of curvature, binding of antibacterial peptides and phase transition) illustrating the versatility
of this method are mentioned. Moreover, limitations and potential problems are discussed. 相似文献
70.