全文获取类型
收费全文 | 7660篇 |
免费 | 1157篇 |
国内免费 | 3202篇 |
专业分类
化学 | 6155篇 |
晶体学 | 389篇 |
力学 | 436篇 |
综合类 | 106篇 |
数学 | 2630篇 |
物理学 | 2303篇 |
出版年
2024年 | 30篇 |
2023年 | 79篇 |
2022年 | 211篇 |
2021年 | 240篇 |
2020年 | 275篇 |
2019年 | 264篇 |
2018年 | 254篇 |
2017年 | 407篇 |
2016年 | 532篇 |
2015年 | 357篇 |
2014年 | 516篇 |
2013年 | 964篇 |
2012年 | 817篇 |
2011年 | 778篇 |
2010年 | 650篇 |
2009年 | 657篇 |
2008年 | 652篇 |
2007年 | 628篇 |
2006年 | 508篇 |
2005年 | 444篇 |
2004年 | 373篇 |
2003年 | 309篇 |
2002年 | 310篇 |
2001年 | 267篇 |
2000年 | 219篇 |
1999年 | 215篇 |
1998年 | 173篇 |
1997年 | 151篇 |
1996年 | 136篇 |
1995年 | 128篇 |
1994年 | 109篇 |
1993年 | 75篇 |
1992年 | 60篇 |
1991年 | 39篇 |
1990年 | 44篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
本文介绍了尼龙1010的结晶过程与动力学、晶体的熔融与转化;并论述了其稀溶液、热降解与动态力学性质及共聚、共混、填充、增强、交联改性方面的研究进展。 相似文献
102.
HUA Rui-nian SUN Hong-jie JIANG Hui-ming SHI Chun-shan 《高等学校化学研究》2006,22(4):423-426
IntroductionPerovskite complex fluorides have attracted great ainterest due to their particular physical properties, suchas piezoelectric characteristics[1], ferromagnetic prop-erty[2], nonmagnetic insulator behavior[3], and photo-luminescence host functi… 相似文献
103.
Jiunn-Der?LiaoEmail author Chonyu?Chen Yi-Te?Wu Chih-Chiang?Weng 《Plasma Chemistry and Plasma Processing》2005,25(3):255-273
High density and well surface-distributed oxygen microwave plasma with an extensible antenna-coupling design was utilized to modify a densely weaved and large-surface-area Nylon-6 fabric within a short treatment time. Plasma pretreatment and subsequent acrylic acid (AAc) or 2-hydroxyethyl methacrylate (HEMA) grafting process were studied and optimized at the stage after dyed and finished procedure. The monomer-grafted dyed Nylon-6 fabrics evolved lasting hydrophilic properties and thereafter created or improved surface properties such as water diffusion, drainage, moisture regain and water absorbency, in different degrees. The pHEMA-grafted sample exhibited minor effect in color perception, which was also much hydrophilic than the pAAc-grafted one. Based upon surface analyses and wetting assessment, the penetration of HEMA monomer into the plasma-treated fabric matrix contributed to the facilitation of wetting properties. This work accordingly ensures such plasma-induced system to incorporate with the pattern of hydrophilic properties on the analogous textiles without interrupting their finishing process. 相似文献
104.
The mechanical properties of glass bead filled low density polyethylene (LDPE) composites in tension have been investigated by using an Instron material testing machine. It is found that with increase of the glass bead weight fraction (φ) the tensile modulus (Ec) and the tensile yield stress (σyc) increase as a form of nonlinear function but contrary to the elongation strain at break; the correlation between Ec and φ accords with the logarithmic mixing rule and the relationship between σy and the volume fraction (φf) can be described by means of a second order equation; the effects of the glass bead diameter on the mechanical properties are not large; when φ and the bead size are suitable, the enhanced toughness effect of the filled-systems is more significant; the tensile strength of the glass bead filled system pretreated with a coupling agent are somewhat greater than those of the untreated system. In addition, the morphology of the samples is studied to explain the relationship between the micro-structure and the mechanical properties of the composites. 相似文献
105.
We provide a quick elementary solution of the mean spherical model in a random external field. This also allows an immediate proof of the self-averaging property of the free energy. We calculate the free energy by means of the replica method, i.e., for any (not necessarily integer) replica numbern, and show that when a phase transition occurs the limits
andn 0 are not interchangeable. 相似文献
106.
η6-苊烯三羰基铬配合物的合成、结构及光谱性质研究 总被引:2,自引:0,他引:2
采用苊烯配体与三胺基三羰基铬在四氢呋喃中回流反应,合成了η6-苊烯三羰基铬配合物.通过元素分析、IR、1HNMR、13CNMR、MS和X射线单晶衍射对其结构进行了表征,比较了标题配合物与其自由配体的光物理行为.晶体结构分析表明,标题配合物属单斜晶系,空间群P21/c,Z=4,a=0.8719(7)nm,b=1.2436(10)nm,c=1.1504(9)nm,β=111.835(13)°,Cr(CO)3基团可与苊烯配体中的2个苯环中的任意一个配位,形成2个异构体(R,S),并以1:1的比例在其晶胞单元中反向面对面堆积,这种异构体共存于晶体中归属于Cr(CO)3基团在配体芳环之间的配位移动重排(IRHRs). 相似文献
107.
108.
The rheological properties of the aqueous mixtures of cationic-anionic surfactants, both in single-phase systems and in aqueous two-phase systems, have been studied. Bizarre rheological properties —negative thixotropy, viscoelasticity and hihg viscosity of shear rate dependent at relatively low concentration — have been observed. An unusual viscosity change, that is, viscosity lowering with increasing concentration, was obtained. The negative thixotropy might be due to the existence of lamellar or sheet-like micelles, viscoelasticity might be induced by rodlike and lamellar or sheet-like micelles, the high viscosity might be a consequence of the formation of network by long rodlike micelles and the concentration-induced viscosity lowering could be interpreted in terms of the decrease of micellar dimensions with concentration. 相似文献
109.
阳离子无皂含氟丙烯酸酯的合成与表面性能 总被引:1,自引:0,他引:1
在合成甲基丙烯酸全氟辛酰氧基乙酯(FA)基础上,用半连续法制备了无皂阳离子含氟丙烯酸酯乳液。当乳液的粒径在100~200 nm、ζ电位大于40 mV时,乳液较稳定。阳离子亲水单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)在含氟丙烯酸酯中质量分数为0.10~0.18、固含量小于20%时乳液的稳定性好,且随DMC含量的增加稳定性提高;含氟丙烯酸酯乳胶膜的附着力与耐磨性好,乳胶膜的透湿率随DMC的增加而增加。随热处理温度的提高,膜表面自由能下降;经160℃热处理后膜发生了交联,表面自由能为18 mN/m,与聚四氟乙烯(PTFE)的表面能相近,DMC含量对膜表面自由能影响不大。XPS分析也表明膜表面氟含量随热处理温度的提高而增加。 相似文献
110.
Hydrothermal reaction of Cd(NO3)2·4H2O with bbp and p-PDOAH2 at 140 ℃ yielded a novel 1D cadmium(Ⅱ) coordination polymer, [Cd(bbp)(p-PDOA)]n (bbp=2,6-bis(benzimidazol-2-yl)pyridine, p-PDOA=p-phenylenedioxydiacetate dianion), in which CdN3O4 pentagonal bipyramids were linked by p-PDOA ligands in a bis-bidentate mode to construct a zigzag chain with the adjacent Cd…Cd distance of 1.14(1) nm, There exists a 2D supramolecular network linked by π-π stacking with a face-to-face distance of 0.35(1) nm between the 2,6-bis(benzimidazol-2-yl) pyridine ligands and hydrogen-bonding interactions (0.27(4) nm). A 3D supramolecular network was further constructed by these non-covalent interactions between the zippers. The TG/DTG showed that its chain skeleton was thermally stable up to 389 ℃ and the blue fluorescent emission of the complex was determined at 428 nm in a solid state with its long decay lifetime of 7.24 ns. 相似文献