全文获取类型
收费全文 | 3650篇 |
免费 | 504篇 |
国内免费 | 383篇 |
专业分类
化学 | 2686篇 |
晶体学 | 20篇 |
力学 | 185篇 |
综合类 | 41篇 |
数学 | 323篇 |
物理学 | 1282篇 |
出版年
2024年 | 14篇 |
2023年 | 86篇 |
2022年 | 122篇 |
2021年 | 101篇 |
2020年 | 137篇 |
2019年 | 140篇 |
2018年 | 109篇 |
2017年 | 108篇 |
2016年 | 154篇 |
2015年 | 154篇 |
2014年 | 196篇 |
2013年 | 270篇 |
2012年 | 342篇 |
2011年 | 358篇 |
2010年 | 237篇 |
2009年 | 204篇 |
2008年 | 254篇 |
2007年 | 216篇 |
2006年 | 187篇 |
2005年 | 149篇 |
2004年 | 113篇 |
2003年 | 88篇 |
2002年 | 86篇 |
2001年 | 82篇 |
2000年 | 57篇 |
1999年 | 65篇 |
1998年 | 65篇 |
1997年 | 62篇 |
1996年 | 67篇 |
1995年 | 76篇 |
1994年 | 41篇 |
1993年 | 25篇 |
1992年 | 35篇 |
1991年 | 31篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1974年 | 1篇 |
1940年 | 1篇 |
1902年 | 1篇 |
1898年 | 1篇 |
排序方式: 共有4537条查询结果,搜索用时 0 毫秒
991.
Catalytic asymmetric sulfur ylide [2,3]-sigmatropic rearrangement of carbenoids generated from aryldiazoacetates has been investigated with a number of chiral Rh(II) and Cu(I) catalysts, and moderately high enantioselectivity (52-78% ee) can be achieved with Cu(MeCN)(4)PF(6)/2,2'-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline]. 相似文献
992.
993.
994.
Juan Li Zhanjun Yang Yongcai Zhang Suhua Yu Qin Xu Qishu Qu Xiaoya Hu 《Mikrochimica acta》2012,179(3-4):265-272
Previously, we have prepared nanoflake-like tin disulfide (SnS2) and used for the immobilization of proteins and biosensing. We have now modified an electrode with a composite consisting of nanoflake-like SnS2 decorated with gold nanoparticles (Au-NPs) and have immobilized glucose oxidase (GOx) on its surface in order to study its direct electrochemistry. Scanning electron microscopy, electrochemical impedance spectroscopy, Fourier transform IR spectroscopy and cyclic voltammetry were used to examine the interaction between GOx and the AuNP-SnS2 film. It is shown that the composite film has a larger surface area and offers a microenvironment that facilitates the direct electron transfer between enzyme and electrode surface. The immobilized enzyme retains its bioactivity and undergoes a surface-controlled, reversible 2-proton and 2-electron transfer reaction, with an apparent electron transfer rate constant of 3.87 s -1. Compared to the nanoflake-like SnS2-based glucose sensor, the GOx-based biosensor exhibits a lower detection limit (1.0 :M), a better sensitivity (21.8 mA?M -1 ?cm -2), and a wider linear range (from 0.02 to 1.3 mM). The sensor displays excellent selectivity, good reproducibility, and acceptable stability. It was successfully applied to reagentless sensing of glucose at ?0.43 V. Figure
The AuNPs decorated nanoflake-like SnS2 (AuNPs–SnS2) composite is for the first time prepared and used to construct novel glucose biosensor nanoflake-like SnS2 was firstly synthesized and SEM image of the nanoflake-like SnS2 (a) and TEM images of the nanoflake-like SnS2 (b), AuNPs (c) and AuNPs–SnS2 (d) are shown in above figure. 相似文献
995.
996.
In contrast to the conventional wisdom that mechanics is a relatively mature subject, the new manifestation of mechanics in an extended or crossed form is unfolding. Mechanics is now powering all subjects, from physical sciences, life sciences to social sciences. We name this new phase for the development of mechanics X-Mechanics. The present article outlines the contents of X-Mechanics from four aspects: cross media, cross scales, cross compliances, and cross cyber/physical spaces. X-Mechanics constitutes an endless frontier of science and technology. 相似文献
997.
Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping (CPT) in Ca+ ions are investigated. If the propagation directions of the three lasers obey the phase matching condition, the dark linewidth resulting from the CPT can be very narrow, and it can be controlled by adjusting the parameters of the lasers. 相似文献
998.
Zhibo Qu Xiaolan Chen Jinwei Yuan Yunliang Bai Tong Chen Lingbo Qu Fujun Wang Xu Li Yufen Zhao 《Tetrahedron》2012,68(15):3156-3159
A convenient one-pot three-component approach leading to synthesis of a series of novel heterocyclic α-aminophosphonates starting either from 2-hydroxyacetophenones or 2-hydroxybenzaldehyes was developed. 相似文献
999.
1000.
Optical windows with external surfaces shaped to satisfy operational environment needs are known as special windows. A novel special window, a sphere-cone-polynomial (SCP) window, is proposed. The formulas of this window shape are given. An SCP MgF2 window with a fineness ratio of 1.33 is designed as an example. The field-of-regard (FOR) angle is ±75°. From the window system simulation results obtained with the calculated fluid dynamics (CFD) and optical design software, we find that compared to the conventional window forms, the SCP shape can not only introduce relatively less drag in the airflow, but also have the minimal effect on imaging. So the SCP window optical system can achieve a high image quality across a super wide FOR without adding extra aberration correctors. The tolerance analysis results show that the optical performance can be maintained with a reasonable fabricating tolerance to manufacturing errors. 相似文献