全文获取类型
收费全文 | 15753篇 |
免费 | 727篇 |
国内免费 | 178篇 |
专业分类
化学 | 11397篇 |
晶体学 | 134篇 |
力学 | 708篇 |
综合类 | 5篇 |
数学 | 2004篇 |
物理学 | 2410篇 |
出版年
2024年 | 35篇 |
2023年 | 146篇 |
2022年 | 746篇 |
2021年 | 706篇 |
2020年 | 552篇 |
2019年 | 654篇 |
2018年 | 651篇 |
2017年 | 528篇 |
2016年 | 882篇 |
2015年 | 604篇 |
2014年 | 761篇 |
2013年 | 1559篇 |
2012年 | 1147篇 |
2011年 | 1132篇 |
2010年 | 778篇 |
2009年 | 639篇 |
2008年 | 742篇 |
2007年 | 681篇 |
2006年 | 508篇 |
2005年 | 489篇 |
2004年 | 345篇 |
2003年 | 331篇 |
2002年 | 297篇 |
2001年 | 134篇 |
2000年 | 116篇 |
1999年 | 105篇 |
1998年 | 70篇 |
1997年 | 94篇 |
1996年 | 87篇 |
1995年 | 63篇 |
1994年 | 76篇 |
1993年 | 52篇 |
1992年 | 65篇 |
1991年 | 60篇 |
1990年 | 70篇 |
1989年 | 60篇 |
1988年 | 55篇 |
1987年 | 59篇 |
1986年 | 56篇 |
1985年 | 68篇 |
1984年 | 51篇 |
1983年 | 36篇 |
1982年 | 50篇 |
1981年 | 38篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1978年 | 29篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1975年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
11.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
12.
13.
Kai He Tsegaye TadesseTsega Xi Liu Jiantao Zai Xin‐Hao Li Xuejiao Liu Wenhao Li Nazakat Ali Xuefeng Qian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):12029-12035
The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p‐n junctions are constructed in 3D free‐standing FeNi‐LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi‐LDH in the space‐charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi‐LDH/CoP/CC achieves ca. 10‐fold and ca. 100‐fold increases compared to those of FeNi‐LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH? has a stronger trend to adsorb on the surface of FeNi‐LDH side in the p‐n junction compared to individual FeNi‐LDH further verifying the synergistic effect in the p‐n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities. 相似文献
14.
15.
16.
A zinc coordination polymer derived from pyridine-2,6-dicarboxylate (PDC), {[Zn2(PDC)2]}n, was successfully prepared via conventional, sonication and microwave-irradiation methods. The composition and characteristics of the obtained coordination polymers (CPs) were investigated by elemental analysis, TGA/DTA, X-ray diffraction and spectroscopic techniques. The so obtained CPs were heat-treated in the air at 600 °C for 2 h to produce ZnO of nanosized particles (NPs). It is of interest to note that the synthesis approach of the precursor greatly affects both the nanoparticle size and the structure of the resulting ZnO NPs. Moreover, the smallest particle size was associated with the sample derived from the ultrasonically prepared precursor. TEM analysis revealed that all samples have sphere-like morphologies. Structural analysis of the prepared ZnO samples was conducted and compared using Rietveld analysis of their PXRD patterns. Optical band gap calculations based on analysis of the UV–vis spectra of ZnO samples using Tauc's power law were achieved. The highest band gap of 3.63 eV was observed for ZnO sample obtained from the ultrasonically prepared precursor. Furthermore, the photocatalytic activity of ZnO NPs for the removal of Eosin Y color was monitored. The highest removal efficiency was recorded for ZnO originated from the ultrasonically synthesized precursor. Enhancement of removal efficiency that reached 98% was attained in only a period of 8 min. Its recycling test showed that it can be reused without structural changes over four cycling experiments. 相似文献
17.
18.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.
19.
Ahmed M. A. El-Sayed Mohamed A. E. Aly 《Journal of Applied Mathematics and Computing》2002,9(2):525-533
The fractional order evolutionary integral equations have been considered by the first author in [6], the existence, uniqueness and some other properties of the solution have been proved. Here we study the continuation of the solution and its fractional order derivative. Also we study the generality of this problem and prove that the fractional order diffusion problem, the fractional order wave problem and the initial value problem of the equation of evolution are special cases of it. The abstract diffusion-wave problem will be given also as an application. 相似文献
20.
M. R. Allazov Ali Riza Kul A. V. Einullaev M. B. Babanly 《Russian Journal of Inorganic Chemistry》2006,51(4):624-629
Some polythermal sections of the Ni-Bi-Se system have been investigated by DTA, X-ray powder diffraction, microstructural analysis, and microhardness measurements. The liquidus surface has been constructed for this system. The compounds NiBi2Se4 and Ni3Bi2Se2 are formed by dystectic reactions and melt at 1088 and 980 K, respectively. The regions of primary and joint phase crystallization have been determined. A commutation of Bi2Se3-based thermoelements with a metal nickel bus-bar has been proposed. 相似文献