全文获取类型
收费全文 | 8175篇 |
免费 | 666篇 |
国内免费 | 966篇 |
专业分类
化学 | 5431篇 |
晶体学 | 230篇 |
力学 | 690篇 |
综合类 | 80篇 |
数学 | 921篇 |
物理学 | 2455篇 |
出版年
2024年 | 12篇 |
2023年 | 57篇 |
2022年 | 116篇 |
2021年 | 121篇 |
2020年 | 161篇 |
2019年 | 132篇 |
2018年 | 144篇 |
2017年 | 191篇 |
2016年 | 231篇 |
2015年 | 206篇 |
2014年 | 358篇 |
2013年 | 590篇 |
2012年 | 442篇 |
2011年 | 450篇 |
2010年 | 411篇 |
2009年 | 613篇 |
2008年 | 622篇 |
2007年 | 597篇 |
2006年 | 454篇 |
2005年 | 563篇 |
2004年 | 488篇 |
2003年 | 360篇 |
2002年 | 339篇 |
2001年 | 282篇 |
2000年 | 245篇 |
1999年 | 223篇 |
1998年 | 218篇 |
1997年 | 200篇 |
1996年 | 137篇 |
1995年 | 117篇 |
1994年 | 122篇 |
1993年 | 93篇 |
1992年 | 90篇 |
1991年 | 50篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 38篇 |
1987年 | 44篇 |
1986年 | 32篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 2篇 |
排序方式: 共有9807条查询结果,搜索用时 31 毫秒
21.
H.-J. Sue E. I. Garcia-Meitin N. A. Orchard 《Journal of Polymer Science.Polymer Physics》1993,31(5):595-608
The fracture behavior of a core-shell rubber (CSR) modified epoxy is investigated using both fracture mechanics and microscopy tools. The CSR-modified epoxy is found to be toughened via numerous line-array cavitations of the CSR particles, followed by plastic flow of the epoxy matrix. The toughening effect via the above craze-like damage process is found to be as effective as that of the well-known widespread rubber cavitation/matrix shear yielding mechanisms. The conditions for triggering the craze-like damage appear to be both stress state and rubber concentration dependent. The type of rubber tougheners utilized also plays a critical role in triggering this rather unusual craze-like damage in epoxy systems. © 1993 John Wiley & Sons, Inc. 相似文献
22.
23.
24.
Rodrigo París José Luis de la Fuente 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3538-3549
Different diblock copolymers constituted by one segment of a monomer supporting a reactive functional group, like allyl methacrylate (AMA), were synthesized by atom transfer radical polymerization (ATRP). Bromo‐terminated polymers, like polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were employed as macroinitiators to form the other blocks. Copolymerizations were carried out using copper chloride with N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as the catalyst system in benzonitrile solution at 70 °C. At the early stage, the ATRP copolymerizations yielded well‐defined linear block copolymers. However, with the polymerization progress a change in the macromolecular architecture takes place due to the secondary reactions caused by the allylic groups, passing to a branched and/or star‐shaped structure until finally yielding gel at monomer conversion around 40% or higher. The block copolymers were characterized by means of size exclusion chromatography (SEC), 1H NMR spectroscopy, and differential scanning calorimetry (DSC). In addition, one of these copolymers, specifically P(BA‐b‐AMA), was satisfactorily modified through osmylation reaction to obtain the subsequent amphiphilic diblock copolymer of P(BA‐b‐DHPMA), where DHPMA is 2,3‐dihydroxypropyl methacrylate; demonstrating the feasibility of side‐chain modification of the functional obtained copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3538–3549, 2007 相似文献
25.
从D触发器激励表入手,分别给出了采用单边沿D触发器和双边沿D触发器的2^n进制异步加法计数器、减法计数器的设计方法.在此基础上,采用逻辑函数修改技术,通过实例讨论了基于单边沿D触发器和双边沿D触发器的异步任意进制计数器的设计.该设计方法方便,快速,具有一定的实用意义. 相似文献
26.
Curved Ferroelectric Liquid Crystal Matrix Displays Driven by Field-Sequential-Color and Active-Matrix Techniques 总被引:1,自引:0,他引:1
Hideo Fujikake Hiroto Sato Takeshi Murashige Yoshihide Fujisaki Taiichiro Kurita Tadahiro Furukawa Fumio Sato 《Optical Review》2006,13(1):14-19
This paper describes a curved field-sequential-color matrix display using fast-response ferroelectric liquid crystal. Black
matrix and transparent electrode patterns were formed on a thin plastic substrate by a transfer method from a glass substrate.
While a composite film of liquid crystal and micro-polymers of walls and fibers was formed between the flexible substrates
by printing, laminating and curing processes of a solution of monomers and liquid crystal, the mechanical stability was enhanced
by use of multi-functional monomers to form large display panels. The image pixels of the matrix panel were driven by an active
matrix scheme using an external switch transistor array at a frequency of 180 Hz for intermittent three-primary-color backlight
illumination. The flexible A4-paper-sized color display with 24 × 16 pixels and 60 Hz field frequency was demonstrated by
illuminating it with sequential three-primary-color lights from light-emitting diodes of the backlight. Our display system
is useful in various information displays because of its freedom of setting and location. 相似文献
27.
Banach空间二阶周期边值问题解的存在性 总被引:2,自引:0,他引:2
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。 相似文献
28.
Wenbing Hu Alexander Buzin Jar‐Shyong Lin Bernhard Wunderlich 《Journal of Polymer Science.Polymer Physics》2003,41(4):403-417
The annealing at 373 K of ultrastrong, gel‐spun polyethylene (PE) has been studied. At this temperature, the fibers show no significant shrinkage. Still, a significant decrease in the mechanical properties is observed. The fibers have been analyzed with differential scanning calorimetry (DSC), temperature‐modulated differential scanning calorimetry (TMDSC), atomic force microscopy (AFM), and small‐angle X‐ray scattering (SAXS). During the annealing, the glass transition of the intermediate phase is exceeded, as shown by DSC. When split for structure analysis by AFM, the annealed fibers undergo plastic deformation around the base fibrils instead of brittle fracture. The quasi‐isothermal TMDSC experiments are compared to the minor structural changes seen with SAXS and AFM. The loss of performance of the PE fibers at 373 K is suggested to be caused by the oriented intermediate phase, and not by major changes in the structure or morphology. The overall metastable, semicrystalline structure is shown by TMDSC to posses local regions that can melt reversibly. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 403–417, 2003 相似文献
29.
In this paper, by means of the method of upper and lower solutions and monotone iterative technique, the existence of maximal and minimal solutions of the boundary value problems for first order impulsive delay differential equations is established. 相似文献
30.