全文获取类型
收费全文 | 25525篇 |
免费 | 4054篇 |
国内免费 | 2446篇 |
专业分类
化学 | 17927篇 |
晶体学 | 310篇 |
力学 | 1538篇 |
综合类 | 115篇 |
数学 | 2995篇 |
物理学 | 9140篇 |
出版年
2024年 | 39篇 |
2023年 | 500篇 |
2022年 | 793篇 |
2021年 | 857篇 |
2020年 | 1013篇 |
2019年 | 999篇 |
2018年 | 813篇 |
2017年 | 716篇 |
2016年 | 1175篇 |
2015年 | 1119篇 |
2014年 | 1319篇 |
2013年 | 1776篇 |
2012年 | 2389篇 |
2011年 | 2443篇 |
2010年 | 1614篇 |
2009年 | 1530篇 |
2008年 | 1666篇 |
2007年 | 1531篇 |
2006年 | 1377篇 |
2005年 | 1170篇 |
2004年 | 850篇 |
2003年 | 656篇 |
2002年 | 619篇 |
2001年 | 453篇 |
2000年 | 441篇 |
1999年 | 528篇 |
1998年 | 439篇 |
1997年 | 445篇 |
1996年 | 474篇 |
1995年 | 366篇 |
1994年 | 327篇 |
1993年 | 240篇 |
1992年 | 241篇 |
1991年 | 199篇 |
1990年 | 171篇 |
1989年 | 145篇 |
1988年 | 98篇 |
1987年 | 109篇 |
1986年 | 89篇 |
1985年 | 82篇 |
1984年 | 47篇 |
1983年 | 43篇 |
1982年 | 36篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
In this work, a projection algorithm is considered for treating strongly continuous semigroups of demicontinuous pseudocontractions. Theorems of strong convergence of fixed points are established in the framework of real Hilbert spaces. 相似文献
983.
In this paper, the Taguchi method combined with fuzzy approach was applied to find the extended optimization for a multi-objective design of a miniature 2.5× zoom fold optics with liquid elements. Relative illuminance (RI) and modulation transfer function (MTF) were considered to be optimized. The experiments were simulated and the results were evaluated by the optical software tool CODE V. It was concluded that the method used in this research was successful in optimizing the values. In our proposed method, the appropriate weight of MTF and RI for the inputs of fuzzy controllers increased the MTF by 9.92%, but the RI only reduced by 0.19% in systematic wide-angle end, respectively. 相似文献
984.
985.
Two-dimensional covalent organic framework(COF) has distinctive properties that offer potential opportunities for developing advanced electrode materials.In this work,a core-shell material composed of TAPB-DMTP-COF(TAPB,1,3,5-tris(4-aminophenyl)benzene;DMTP,2,5-dimethoxyterephaldehyde)core and conducting polymer shell,TAPB-DMTP-COF@PANI,was synthesized solvothermally using a polymerization method.The structural cha racteristics of the prepared composite were revealed by X-ray diffraction patterns(XRD),fourier transform infrared spectra(FTIR),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM).The electrochemical analyses were verified by subsequent monitoring of trace levels of acetaminophen.This resultant composite not only facilitated acetaminophen to interact with absorption sites by π-π stacking effect and hydrogen bonding but also overcame the poor conductivity of COF.Under the optimal conditions,a low limit of detection of0.032 μmol/L and wide linear range of 0.10-500 μmol/L were obtained.The electrochemical platform was almost unaffected by other interfering substances,and successfully applied for the practical detection of acetaminophen in commercial tablet,human blood serum and urine.The enhanced performance makes this COF based core-shell composite a promising material in electrochemical senso r. 相似文献
986.
987.
Lingjie Sun Dr. Weigang Zhu Wei Wang Dr. Fangxu Yang Congcong Zhang Prof. Shufeng Wang Dr. Xiaotao Zhang Prof. Rongjin Li Prof. Huanli Dong Prof. Wenping Hu 《Angewandte Chemie (International ed. in English)》2017,56(27):7831-7835
Cocrystals of 4-styrylpyridine and 1,2,4,5-tetracyanobenzene were successfully prepared by supramolecular self-assembly. Donor–acceptor interactions between the molecular components are the main driving force for self-assembly and contribute to intermolecular charge transfer. The cocrystals possess two-photon absorption properties that are not observed in the individual components; suggesting that two-photon absorption originates from intermolecular charge-transfer interactions in the donor–acceptor system. The origin of two-photon absorption in multichromophore systems remains under-researched; thus, the system offers a rare demonstration of two-photon absorption by cocrystallization. Cocrystal engineering may facilitate further design and development of novel materials for nonlinear optical and optoelectronic applications. 相似文献
988.
Xiao-Ling Zhang Li Zhang Ya-Ling Ye Xiang-Hui Li Dr. Bi-Lian Ni Prof. Ying Li Dr. Wei-Ming Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1039-1045
Developing efficient catalysts for the conversion of CO2 into fuels and value-added chemicals is of great significance to relieve the growing energy crisis and global warming. With the assistance of DFT calculations, it was found that, different from Al12X (X=Be, Al, and C), the alkali-metal-like superatom Al12P prefers to combine with CO2 via a bidentate double oxygen coordination, yielding a stable Al12P(η2-O2C) complex containing an activated radical anion of CO2 (i.e., CO2.−). Thereby, this compound could not only participate in the subsequent cycloaddition reaction with propylene oxide but also initiate the radical reaction with hydrogen gas to form high-value chemicals, revealing that Al12P can play an important role in catalyzing these conversion reactions. Considering that Al12P has been produced in laboratory and is capable of absorbing visible light to drive the activation and transformation of CO2, it is anticipated that this work could guide the discovery of additional superatom catalysts for CO2 transformation and open up a new research field of superatom catalysis. 相似文献
989.
We observed a novel voltage peak in the proximity-induced superconducting gold (Au) nanowire while cooling the sample through the superconducting transition temperature. The voltage peak turned dip during warming. The voltage peak or dip was found to originate respectively from the emergence or vanishing of the proximity-induced superconductivity in the Au nanowire. The amplitude of the voltage signal depends on the temperature scanning rate, and it cannot be detected when the temperature is changed slower than 0.03 K/min. This transient feature suggests the non-equilibrium property of the effect. Ginzburg-Landau model clarified the voltage peak by considering the emergence of Cooper pairs of relatively lower free energy in superconducting W contact and the non-equilibrium diffusion of Cooper pairs and quasiparticles. 相似文献
990.
Journal of Radioanalytical and Nuclear Chemistry - As a result of nuclear power plant accidents such as Chernobyl and Fukushima, and even their maintenance, the soil is contaminated due to the... 相似文献