全文获取类型
收费全文 | 112258篇 |
免费 | 18997篇 |
国内免费 | 15719篇 |
专业分类
化学 | 80635篇 |
晶体学 | 1475篇 |
力学 | 7187篇 |
综合类 | 1270篇 |
数学 | 14205篇 |
物理学 | 42202篇 |
出版年
2024年 | 263篇 |
2023年 | 2004篇 |
2022年 | 3148篇 |
2021年 | 3678篇 |
2020年 | 4352篇 |
2019年 | 4321篇 |
2018年 | 3791篇 |
2017年 | 3724篇 |
2016年 | 5210篇 |
2015年 | 5295篇 |
2014年 | 6338篇 |
2013年 | 8208篇 |
2012年 | 9893篇 |
2011年 | 10354篇 |
2010年 | 7356篇 |
2009年 | 7145篇 |
2008年 | 7932篇 |
2007年 | 6915篇 |
2006年 | 6583篇 |
2005年 | 5564篇 |
2004年 | 4466篇 |
2003年 | 3654篇 |
2002年 | 3917篇 |
2001年 | 3285篇 |
2000年 | 2645篇 |
1999年 | 2501篇 |
1998年 | 1906篇 |
1997年 | 1760篇 |
1996年 | 1667篇 |
1995年 | 1462篇 |
1994年 | 1222篇 |
1993年 | 1045篇 |
1992年 | 841篇 |
1991年 | 845篇 |
1990年 | 709篇 |
1989年 | 544篇 |
1988年 | 396篇 |
1987年 | 343篇 |
1986年 | 333篇 |
1985年 | 289篇 |
1984年 | 190篇 |
1983年 | 178篇 |
1982年 | 131篇 |
1981年 | 104篇 |
1980年 | 72篇 |
1979年 | 41篇 |
1977年 | 35篇 |
1976年 | 32篇 |
1975年 | 35篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Yuanbo Gao Tingting Yang Xueli Wang Jizong Chen Yong He 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1610-1623
Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with 1H NMR and 13C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (Tm > 270 °C), high crystallinity (Xc > 32%) and high decomposition temperature (T5 > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant. 相似文献
2.
3.
4.
Qianqian Fan Zirui Liu Feng Qiu Prof. Yong Mao Prof. Qingju Liu Prof. Longzhou Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202700
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom. 相似文献
5.
Guo-Xing Li Xiao-Wei Qu Lu-Wei Hao Qing Li Su Chen 《Journal of polymer science. Part A, Polymer chemistry》2022,60(11):1710-1717
From the implementation point of view, the printable magnetic Janus colloidal photonic crystals (CPCs) microspheres are highly desirable. Herein, we developed a dispensing-printing strategy for magnetic Janus CPCs display via a microfluidics-automatic printing system. Monodisperse core/shell colloidal particles and magnetic Fe3O4 nanoparticles precursor serve as inks. Based on the equilibrium of three-phase interfacial tensions, Janus structure is successfully formed, followed by UV irradiation and self-assembly of colloid particle to generate magnetic Janus CPCs microspheres. Notably, this method shows distinct superiority with highly uniform Janus CPCs structure, where the TMPTA/Fe3O4 hemisphere is in the bottom side while CPCs hemisphere is in the top side. Thus, by using Janus CPCs microspheres with two different structural colors as pixel points, a pattern with red flower and green leaf is achieved. Moreover, 1D linear Janus CPCs pattern encapsulated by hydrogel is also fabricated. Both the color and the shape can be changed under the traction of magnets, showing great potentials in flexible smart displays. We believe this work not only offers a new feasible pathway to construct magnetic Janus CPCs patterns by a dispensing-printable fashion, but also provides new opportunities for flexible and smart displays. 相似文献
6.
Acta Mechanica Sinica - 相似文献
7.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform. 相似文献
8.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
9.
Dr. Ruijuan Yao Prof. Di Liu Dr. Huihui Wan Dr. Yongqiang Mei Jiahui Wang Dr. Rui Cai Dr. Huimin Zhang Dr. Yuzhen Zhao Dr. Zemin He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202269
By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (ηext) of 89.8 lm W−1 and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m−2 and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m−2. This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off. 相似文献
10.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献