全文获取类型
收费全文 | 62846篇 |
免费 | 6909篇 |
国内免费 | 10507篇 |
专业分类
化学 | 18398篇 |
晶体学 | 1065篇 |
力学 | 1809篇 |
综合类 | 924篇 |
数学 | 3708篇 |
物理学 | 12608篇 |
综合类 | 41750篇 |
出版年
2024年 | 198篇 |
2023年 | 555篇 |
2022年 | 1429篇 |
2021年 | 1515篇 |
2020年 | 1485篇 |
2019年 | 1238篇 |
2018年 | 1195篇 |
2017年 | 1583篇 |
2016年 | 1595篇 |
2015年 | 2413篇 |
2014年 | 3118篇 |
2013年 | 3940篇 |
2012年 | 4126篇 |
2011年 | 4526篇 |
2010年 | 4379篇 |
2009年 | 4755篇 |
2008年 | 5298篇 |
2007年 | 5351篇 |
2006年 | 4925篇 |
2005年 | 4437篇 |
2004年 | 3568篇 |
2003年 | 2757篇 |
2002年 | 2747篇 |
2001年 | 2587篇 |
2000年 | 2536篇 |
1999年 | 1654篇 |
1998年 | 752篇 |
1997年 | 625篇 |
1996年 | 664篇 |
1995年 | 545篇 |
1994年 | 509篇 |
1993年 | 488篇 |
1992年 | 419篇 |
1991年 | 349篇 |
1990年 | 313篇 |
1989年 | 328篇 |
1988年 | 265篇 |
1987年 | 222篇 |
1986年 | 158篇 |
1985年 | 99篇 |
1984年 | 101篇 |
1983年 | 100篇 |
1982年 | 81篇 |
1981年 | 67篇 |
1980年 | 52篇 |
1979年 | 36篇 |
1978年 | 22篇 |
1976年 | 19篇 |
1957年 | 20篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
CHEN Zhi-hong XU Li BA Xue-qing ZENG Xian-lu 《高等学校化学研究》2006,22(3):302-307
Introduction Migrationandrecruitmentofleukocytesfromblood toinflammatorylesionsitesaresequentiallyregulated byadhesionmoleculesandtheirreceptors[1].These lectinfamilyplaysamajorroleininitiatingattachement ofneutrophilstotheactivatedendothelium.P selectin,… 相似文献
73.
74.
Morphological and chemical properties of both the surface and interface of poly(vinylidene fluoride)/poly(methyl methacrylate)-co-poly(ethyl acrylate) (PVDF/PMMA-co-PEA) blend films have been investigated before and after the samples were exposed to ultraviolet (UV) irradiation using a xenon arc lamp at 50 °C and 9% relative humidity (RH) for 7 months. Surface and interfacial morphologies were studied by atomic force microscopy (AFM). Chemical composition information was obtained by confocal Raman microscopy, attenuated total reflection-FTIR spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Results show an enrichment of the PVDF material at the air surface, while the acrylic copolymer enriches the interface. Blends having greater than 50% mass fraction of PVDF show little change in the surface morphology after UV exposure for 7 months. However, for a lower PVDF content, blends exhibit significant degradation of PMMA-co-PEA copolymer and a much rougher surface after UV exposure. Microstructural changes in the PVDF spherulites are also observed after UV degradation. It is found that the surface and interfacial morphologies are correlated with the chemical properties. 相似文献
75.
76.
Ben-Yuan Gu Yao Lu Tzong-Jer Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):493-502
We present numerical investigations of the transmission properties of electrons in a normal quantum wire tangentially attached
to a superconductor ring threaded by magnetic flux. A point scatterer with a δ -function potential is placed at node to model
scattering effect. We find that the transmission characteristics of electrons in this structure strongly depend on the normal
or superconducting state of the ring. The transmission probability as a function of the energy of incident electrons, in the
case of a superconductor ring threaded by one quantum magnetic flux, emerges one deep dip, imposed upon the first broad bump
in spectrum. This intrinsic conductance dip originates from the superconductor state of the ring. When increasing the magnetic
flux from one quantum magnetic flux to two, the spectrum shifts toward higher energy region in the whole. This conductance
dip accordingly shifts and appears in the second bump. In the presence of a point-scatterer at the node, the spectrum is substantially
modified. Based on the condition of the formation of the standing wave functions in the ring and the broken of the time-reserve
symmetry of Schr?dinger equation after switching magnetic flux, the characteristics of transmission of electrons in this structure
can be well understood.
Received 6 November 2001 相似文献
77.
78.
对于任意秩有限总体,在二次损失下,有关文献已给出了线性可预测变量在齐次线性预测类中的唯一线性Minimax预测.本文在正态假设下,证明了这个线性Minimax预测也是线性可预测变量在一切预测类中的唯一Minimax预测. 相似文献
79.
80.
The photoionization of H atoms irradiated by few-cycle laser pulses is studied numerically. The variations of the total ionization, the partial ionizations in opposite directions, and the corresponding asymmetry with the carrier-envelope phase in several pulse durations are obtained. We find that besides a stronger modulation on the partial ionizations, the change of pulse duration leads to a shift along carrier-envelope (CE) phase in the calculated signals. The phase shift arises from the nonlinear property of ionization and relates closely to the Coulomb attraction of the parent ion to the ionized electron. Our calculations show good agreement with the experimental observation under similar conditions. 相似文献