全文获取类型
收费全文 | 2565篇 |
免费 | 432篇 |
国内免费 | 215篇 |
专业分类
化学 | 1146篇 |
晶体学 | 35篇 |
力学 | 216篇 |
综合类 | 53篇 |
数学 | 693篇 |
物理学 | 1069篇 |
出版年
2024年 | 3篇 |
2023年 | 32篇 |
2022年 | 98篇 |
2021年 | 80篇 |
2020年 | 91篇 |
2019年 | 94篇 |
2018年 | 91篇 |
2017年 | 127篇 |
2016年 | 133篇 |
2015年 | 103篇 |
2014年 | 141篇 |
2013年 | 220篇 |
2012年 | 149篇 |
2011年 | 166篇 |
2010年 | 162篇 |
2009年 | 180篇 |
2008年 | 177篇 |
2007年 | 159篇 |
2006年 | 133篇 |
2005年 | 129篇 |
2004年 | 122篇 |
2003年 | 87篇 |
2002年 | 90篇 |
2001年 | 69篇 |
2000年 | 53篇 |
1999年 | 55篇 |
1998年 | 48篇 |
1997年 | 41篇 |
1996年 | 28篇 |
1995年 | 28篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有3212条查询结果,搜索用时 15 毫秒
71.
Gang Wu Jiao-Dong Jiang Paul A. Tucker John A. Cuculo 《Journal of Polymer Science.Polymer Physics》1996,34(12):2035-2047
The development of an oriented noncrystalline phase in a semicrystalline polymer filament has been studied via X-ray scattering. These unique PET fibers contain a relatively high noncrystalline content and also have high tenacity, high modulus, and low breaking elongation. Fiber properties were found to be very responsive to the oriented amorphous phase content. This phase was utilized for interpreting noncrystalline orientation in PET fibers produced by a new extrusion technique. Here, the oriented noncrystalline regions in a series of PET fibers varies from 6% to 63%, depending strongly on the production conditions. In particular, samples produced with a newly developed threadline modification process possess a high content of oriented noncrystalline polymer. Measurements such as dynamic and static mechanical properties have been performed on various samples, and these properties are related to the oriented noncrystalline phase. The results provide direct evidence for the existence of highly oriented noncrystalline material in these unique PET fibers spun with a threadline modification process. © 1996 John Wiley & Sons, Inc. 相似文献
72.
73.
Greggory S. Bennett Richard J. Farris 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):73-87
It is shown that amine-terminated poly(aryl ether ketone)s based on the reaction of 4,4'-difluorobenzophenone, and a substituted hydroquinone [either methylhydroquinone (MePK), t-butylhydroquinone (tBPK), or phenylhydroquinone (PhPK)] of controlled molecular weight and high amine-termination efficiency can be synthesized by a two-step reaction technique. Attempts to synthesize analogous materials by a one-step method were shown to be unsuccessful. The side groups are shown to have a large influence on the aromatic proton chemical shifts and this effect is characterized. The side groups and molecular weight are also shown to influence the thermal transitions of the respective polymers. The tBPK polymer possessed the highest glass transition temperature, while the MePK polymer was found to be the only semi-crystalline polymer; a unit cell is proposed. The side groups and molecular weight effects are also characterized as a function of thermal stability and mechanical properties. © 1994 John Wiley & Sons, Inc. 相似文献
74.
以聚丙烯微孔膜为基材,通过扩散控制原位共聚合的方法在人填充了组成沿膜的厚度方向逐渐改变的无规共聚物,X-光电子能谱(XPS)、全反射红外光谱(ATR)以及动态粘弹谱的分析结果。说明所制备得到的合膜具有明显的渐变聚合物性质。 相似文献
75.
在生物工程中所用的高分子材料一般统称为高分子生物材料,其涉及的范围很广。医用高分子是其中很重要的一类,另一类就是在生物技术中所用的高分子材料。对于高分子生物材料可根据其材料性质进行分类,也可按使用范围进行分类。如体内应用的材料,半体内应用的材料和体外应用的材料。本文着重介绍了抗凝血材料、药用高分子材料及应用于生物技术中高分子材料的研究进展,并总结分析了这几个研究领域中的发展趋势。 相似文献
76.
77.
Dr. Damien Hudry Dr. Christos Apostolidis Dr. Olaf Walter Dr. Arne Janßen Dr. Dario Manara Dr. Jean‐Christophe Griveau Dr. Eric Colineau Dr. Tonya Vitova Tim Prüßmann Dr. Di Wang Dr. Christian Kübel Dr. Daniel Meyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10431-10438
Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non‐conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium‐based nanomaterials. Here we show that ultra‐small (3.2±0.9 nm) and highly crystalline plutonium oxide (PuO2) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO2(NO3)2] ? 3 H2O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO2 NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO2 NCs have been characterized by a wide variety of techniques (powder X‐ray diffraction (PXRD), X‐ray absorption fine structure (XAFS), X‐ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO2 NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements. 相似文献
78.
Precision PEGylated Polymers Obtained by Sequence‐Controlled Copolymerization and Postpolymerization Modification 下载免费PDF全文
Sansanee Srichan Dr. Hatice Mutlu Dr. Nezha Badi Dr. Jean‐François Lutz 《Angewandte Chemie (International ed. in English)》2014,53(35):9231-9235
Copolymers containing water‐soluble poly(ethylene glycol) (PEG) side chains and precisely controlled functional microstructures were synthesized by sequence‐controlled copolymerization of donor and acceptor comonomers, that is, styrene derivatives and N‐substituted maleimides. Two routes were compared for the preparation of these structures: a) the direct use of a PEG–styrene macromonomer as a donor comonomer, and b) the use of an alkyne‐functionalized styrenic comonomer, which was PEGylated by copper‐catalyzed alkyne–azide cycloaddition after polymerization. The latter method was found to be the most versatile and enabled the synthesis of high‐precision copolymers. For example, PEGylated copolymers containing precisely positioned fluorescent (e.g. pyrene), switchable (e.g. azobenzene), and reactive functionalities (e.g. an activated ester) were prepared. 相似文献
79.
80.