全文获取类型
收费全文 | 24022篇 |
免费 | 2101篇 |
国内免费 | 5380篇 |
专业分类
化学 | 25182篇 |
晶体学 | 648篇 |
力学 | 592篇 |
综合类 | 192篇 |
数学 | 1821篇 |
物理学 | 3068篇 |
出版年
2024年 | 34篇 |
2023年 | 234篇 |
2022年 | 542篇 |
2021年 | 592篇 |
2020年 | 820篇 |
2019年 | 686篇 |
2018年 | 654篇 |
2017年 | 755篇 |
2016年 | 954篇 |
2015年 | 805篇 |
2014年 | 1106篇 |
2013年 | 1900篇 |
2012年 | 2813篇 |
2011年 | 1314篇 |
2010年 | 1073篇 |
2009年 | 1363篇 |
2008年 | 1531篇 |
2007年 | 1696篇 |
2006年 | 1473篇 |
2005年 | 1475篇 |
2004年 | 1294篇 |
2003年 | 1084篇 |
2002年 | 888篇 |
2001年 | 697篇 |
2000年 | 712篇 |
1999年 | 644篇 |
1998年 | 550篇 |
1997年 | 513篇 |
1996年 | 485篇 |
1995年 | 477篇 |
1994年 | 410篇 |
1993年 | 304篇 |
1992年 | 363篇 |
1991年 | 271篇 |
1990年 | 212篇 |
1989年 | 162篇 |
1988年 | 108篇 |
1987年 | 88篇 |
1986年 | 89篇 |
1985年 | 63篇 |
1984年 | 45篇 |
1983年 | 23篇 |
1982年 | 32篇 |
1981年 | 24篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 24篇 |
1976年 | 16篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Qi Nie Hao Jiang Si-Dong Zhong Qiang Wang Juan-Juan Wang Hao Wang Li-Hua Wu 《Entropy (Basel, Switzerland)》2022,24(7)
Community detection and structural hole spanner (the node bridging different communities) identification, revealing the mesoscopic and microscopic structural properties of complex networks, have drawn much attention in recent years. As the determinant of mesoscopic structure, communities and structural hole spanners discover the clustering and hierarchy of networks, which has a key impact on transmission phenomena such as epidemic transmission, information diffusion, etc. However, most existing studies address the two tasks independently, which ignores the structural correlation between mesoscale and microscale and suffers from high computational costs. In this article, we propose an algorithm for simultaneously detecting communities and structural hole spanners via hyperbolic embedding (SDHE). Specifically, we first embed networks into a hyperbolic plane, in which, the angular distribution of the nodes reveals community structures of the embedded network. Then, we analyze the critical gap to detect communities and the angular region where structural hole spanners may exist. Finally, we identify structural hole spanners via two-step connectivity. Experimental results on synthetic networks and real networks demonstrate the effectiveness of our proposed algorithm compared with several state-of-the-art methods. 相似文献
92.
S. V. Bel'tyukova E. I. Tselik A. V. Egorova O. I. Teslyuk 《Journal of Applied Spectroscopy》2003,70(2):307-310
The luminescence of the sorbates of the Eu(III) and Tb(III) complexes on the CaA-type zeolite with derivatives of aliphatic and aromatic carbonic acids has been studied. It is shown that the luminescent materials obtained can be used as light regulators and transformers which absorb energy in the UV spectral region and transform it into visible radiation. 相似文献
93.
Shaymaa Khazaal Julien Harb Mohamad Rima Cdric Annweiler Yingliang Wu Zhijian Cao Ziad Abi Khattar Christian Legros Herv Kovacic Ziad Fajloun Jean-Marc Sabatier 《Molecules (Basel, Switzerland)》2022,27(9)
COVID-19 has expanded across the world since its discovery in Wuhan (China) and has had a significant impact on people’s lives and health. Long COVID is a term coined by the World Health Organization (WHO) to describe a variety of persistent symptoms after acute SARS-CoV-2 infection. Long COVID has been demonstrated to affect various SARS-CoV-2-infected persons, independently of the acute disease severity. The symptoms of long COVID, like acute COVID-19, consist in the set of damage to various organs and systems such as the respiratory, cardiovascular, neurological, endocrine, urinary, and immune systems. Fatigue, dyspnea, cardiac abnormalities, cognitive and attention impairments, sleep disturbances, post-traumatic stress disorder, muscle pain, concentration problems, and headache were all reported as symptoms of long COVID. At the molecular level, the renin-angiotensin system (RAS) is heavily involved in the pathogenesis of this illness, much as it is in the acute phase of the viral infection. In this review, we summarize the impact of long COVID on several organs and tissues, with a special focus on the significance of the RAS in the disease pathogenesis. Long COVID risk factors and potential therapy approaches are also explored. 相似文献
94.
研究了(Ti,Al)薄膜的光学特性,对其反射和透射光谱作了仔细分析。运用Hadley方程,算出一定成分(Ti,Al)N膜的折射率n,消光系数k随波长的变化关系。又根据透射曲线,计算出了(Ti,Al)N膜的光隙能。 相似文献
95.
96.
97.
Hydroaminomethylation of various olefins with primary and secondary amines was carried out using a simple and efficient rhodium–phosphinite complex catalyst. The influence of various reaction parameters including the effects of temperature, pressure, catalyst loading, time and solvents has been investigated. The present protocol is general with wider substrate applicability for the synthesis of an important class of aliphatic amines and arylethylamines. High activity and selectivity for amines was achieved with a very good substrate/catalyst molar ratio (turnover number 2500) under mild reaction conditions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
98.
S. M. Jones A. Amran S. E. Friberg B. Katz G. C. Farrington 《Journal of Dispersion Science and Technology》2013,34(1):97-117
ABSTRACT Materials which display ionic conductivity were produced by the sol-gel and microemulsion-gel methods. The charging and discharging characteristics were investigated and it was found that a single ionic species was responsible for the conduction, the ionic species being residual protons from the initial component mixture. The complex impedence of various samples was measured and the ionic conductivities ranged in value from 9 × 10?8 to 1 × 10?5 ohm?1 cm?1. An Arrhemius plot for a microemulsion-gel revealed that the energy of activation was 0.15 eV. 相似文献
99.
Die Autoren machen mit aktivierungsanalytischen Untersuchungen am Reaktor der Technischen Universität Budapest bekannt. Der thermische Neutronenfluβ war 2·1011 ncm?28?1, und es wurde ein Ge(Li)-Detektor mit 25 cm3 Volumen und einer Energieauflösung von 2 keV angewendet. Die untersuchten Tomatenproben enthielten durchschnittlich 85% Trockensubstanz. Es wurden folgende Konzentrationen an Spurenelementen ermittelt (in mg/kg): Br: 50,1; Mn: 10,2; Zn: 9,3; Cu: 6,6; As: 0,051; Sb:0,030; Au: 0,005. 相似文献
100.
M. Geisler 《Isotopes in environmental and health studies》2013,49(8):321-325
Es wird eine Anordnung beschrieben, die es gestattet, bis zu 7 Proben unter identischen Bedingungen rotationssymmetrisch zu aktivieren. Die Proben rotieren um zwei parallele Achsen. Es wird über Erprobungsmessungen durch Aktivierung von Cu-und N-haltigen Proben berichtet. 相似文献