全文获取类型
收费全文 | 41959篇 |
免费 | 1142篇 |
国内免费 | 167篇 |
专业分类
化学 | 26979篇 |
晶体学 | 331篇 |
力学 | 721篇 |
综合类 | 4篇 |
数学 | 7344篇 |
物理学 | 7889篇 |
出版年
2023年 | 266篇 |
2022年 | 496篇 |
2021年 | 646篇 |
2020年 | 625篇 |
2019年 | 691篇 |
2018年 | 776篇 |
2017年 | 722篇 |
2016年 | 1421篇 |
2015年 | 1144篇 |
2014年 | 1232篇 |
2013年 | 2564篇 |
2012年 | 2529篇 |
2011年 | 2716篇 |
2010年 | 1722篇 |
2009年 | 1644篇 |
2008年 | 2389篇 |
2007年 | 2322篇 |
2006年 | 2111篇 |
2005年 | 1975篇 |
2004年 | 1669篇 |
2003年 | 1370篇 |
2002年 | 1171篇 |
2001年 | 880篇 |
2000年 | 788篇 |
1999年 | 619篇 |
1998年 | 472篇 |
1997年 | 460篇 |
1996年 | 561篇 |
1995年 | 415篇 |
1994年 | 444篇 |
1993年 | 405篇 |
1992年 | 383篇 |
1991年 | 350篇 |
1990年 | 326篇 |
1989年 | 278篇 |
1988年 | 268篇 |
1987年 | 257篇 |
1986年 | 260篇 |
1985年 | 333篇 |
1984年 | 350篇 |
1983年 | 231篇 |
1982年 | 254篇 |
1981年 | 250篇 |
1980年 | 249篇 |
1979年 | 178篇 |
1978年 | 179篇 |
1977年 | 187篇 |
1976年 | 154篇 |
1975年 | 144篇 |
1973年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
12.
Design and development of a two‐dimensional system based on hydrophilic and reversed‐phase liquid chromatography with on‐line sample treatment for the simultaneous separation of excreted xenobiotics and endogenous metabolites in urine 下载免费PDF全文
Diego García‐Gómez Encarnación Rodríguez‐Gonzalo Rita Carabias‐Martínez 《Biomedical chromatography : BMC》2015,29(8):1190-1196
In the present work we describe a two‐dimensional liquid chromatographic system (2D‐LC) with detection by mass spectrometry (MS) for the simultaneous separation of endogenous metabolites of clinical interest and excreted xenobiotics deriving from exposure to toxic compounds. The 2D‐LC system involves two orthogonal chromatographic modes, hydrophilic interaction liquid chromatography (HILIC) to separate polar endogenous metabolites and reversed‐phase (RP) chromatography to separate excreted xenobiotics of low and intermediate polarity. Additionally, the present proposal has the novelty of incorporating an on‐line sample treatment based on the use of restricted access materials (RAMs), which permits the direct injection of urine samples into the system. The work is focused on the instrumental coupling, studying all possible options and attempting to circumvent the problems of solvent incompatibility between the RAM device and the two chromatographic columns, HILIC and RP. The instrumental configuration developed, RAM‐HILIC‐RPLC‐MS/MS, allows the simultaneous assessment of urinary metabolites of clinical interest and excreted compounds derived from exposure to toxic agents with minimal sample manipulation. Thus, it may be of interest in areas such as occupational and environmental toxicology in order to explore the possible relationship between the two types of compounds. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
14.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons 下载免费PDF全文
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
15.
16.
17.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
18.
19.
Eduard Feireisl Antonín Novotný Hana Petzeltov 《Mathematical Methods in the Applied Sciences》2002,25(12):1045-1073
We prove a general compactness result for the solution set of the compressible Navier–Stokes equations with respect to the variation of the underlying spatial domain. Among various corollaries, we then prove a general existence theorem for the system in question with no restrictions on smoothness of the spatial domain. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
20.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献