全文获取类型
收费全文 | 17343篇 |
免费 | 1616篇 |
国内免费 | 720篇 |
专业分类
化学 | 10216篇 |
晶体学 | 137篇 |
力学 | 753篇 |
综合类 | 52篇 |
数学 | 2864篇 |
物理学 | 5657篇 |
出版年
2023年 | 225篇 |
2022年 | 358篇 |
2021年 | 409篇 |
2020年 | 517篇 |
2019年 | 439篇 |
2018年 | 462篇 |
2017年 | 455篇 |
2016年 | 865篇 |
2015年 | 725篇 |
2014年 | 815篇 |
2013年 | 1364篇 |
2012年 | 1215篇 |
2011年 | 1279篇 |
2010年 | 881篇 |
2009年 | 784篇 |
2008年 | 848篇 |
2007年 | 672篇 |
2006年 | 652篇 |
2005年 | 472篇 |
2004年 | 401篇 |
2003年 | 354篇 |
2002年 | 355篇 |
2001年 | 299篇 |
2000年 | 261篇 |
1999年 | 287篇 |
1998年 | 272篇 |
1997年 | 251篇 |
1996年 | 244篇 |
1995年 | 202篇 |
1994年 | 180篇 |
1993年 | 158篇 |
1992年 | 157篇 |
1991年 | 148篇 |
1990年 | 106篇 |
1989年 | 106篇 |
1988年 | 109篇 |
1987年 | 109篇 |
1986年 | 103篇 |
1985年 | 119篇 |
1984年 | 104篇 |
1983年 | 99篇 |
1982年 | 80篇 |
1981年 | 91篇 |
1980年 | 96篇 |
1979年 | 83篇 |
1978年 | 89篇 |
1977年 | 97篇 |
1976年 | 78篇 |
1974年 | 78篇 |
1973年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF. 相似文献
4.
Terahertz(THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional(1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime. 相似文献
5.
A protocol to correct for intra‐ and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line 下载免费PDF全文
6.
Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization 下载免费PDF全文
Libuše Hanková Ladislav Holub Karel Jeřábek 《Journal of Polymer Science.Polymer Physics》2015,53(11):774-781
This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781 相似文献
7.
8.
The γcmc values of CTAB-SDS decrease from 63.67 mN/m at 10‡C to 36.38 mN/m at 90‡C, slightly lower than those of either CTAB or SDS.
Correspondingly, the CMC of CTAB-SDS decreases almost by half. The increase of surface activity of CTAB-SDS can be attributed
to the relatively weak electrostatic interaction at high temperature, which is supported by the increase of solubility of
CTAB-SDS with rise in temperature. Catalytic effect on oxidation of toluene derivatives with potassium permanganate follows
the order CTAB-SDS > SDS > CTAB. This is not caused by the dissociative effect of CTAB-SDS with low surface activity at low
temperature, as seen from the fact that almost all oxidative products can be retrieved for different toluene derivatives and
surfactants by mimicking the conditions of reaction. In the emulsifications of toluene derivatives at 90‡C, the time that
turbid water layers of surfactant solutions take to become clear is the same as that of the catalytic effect on oxidation
of toluene derivatives. Thus, it can be inferred that surfactants can improve the oxidation yields of toluene derivatives
by increasing the contact between two reacting phases. 相似文献
9.
10.
Chromatographia - A theoretical model is used to predict retention times of divalent metal cations in single-column ion chromatography using one or more ligands in the eluent. Stability constants... 相似文献