全文获取类型
收费全文 | 89434篇 |
免费 | 17004篇 |
国内免费 | 9555篇 |
专业分类
化学 | 61846篇 |
晶体学 | 926篇 |
力学 | 5772篇 |
综合类 | 583篇 |
数学 | 10406篇 |
物理学 | 36460篇 |
出版年
2024年 | 102篇 |
2023年 | 2047篇 |
2022年 | 2093篇 |
2021年 | 2947篇 |
2020年 | 4033篇 |
2019年 | 3600篇 |
2018年 | 3233篇 |
2017年 | 2890篇 |
2016年 | 4590篇 |
2015年 | 4329篇 |
2014年 | 5328篇 |
2013年 | 6820篇 |
2012年 | 8330篇 |
2011年 | 8686篇 |
2010年 | 5813篇 |
2009年 | 5610篇 |
2008年 | 5999篇 |
2007年 | 5269篇 |
2006年 | 4923篇 |
2005年 | 3942篇 |
2004年 | 3026篇 |
2003年 | 2340篇 |
2002年 | 2035篇 |
2001年 | 1810篇 |
2000年 | 1581篇 |
1999年 | 1816篇 |
1998年 | 1558篇 |
1997年 | 1539篇 |
1996年 | 1525篇 |
1995年 | 1327篇 |
1994年 | 1152篇 |
1993年 | 1004篇 |
1992年 | 868篇 |
1991年 | 786篇 |
1990年 | 653篇 |
1989年 | 508篇 |
1988年 | 379篇 |
1987年 | 312篇 |
1986年 | 324篇 |
1985年 | 269篇 |
1984年 | 152篇 |
1983年 | 120篇 |
1982年 | 105篇 |
1981年 | 58篇 |
1980年 | 42篇 |
1979年 | 14篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 11篇 |
1957年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Aequationes mathematicae - In this paper we study estimation, continuous dependence and Hyers–Ulam stability for continuous solutions of a second order iterative equation. First we give an... 相似文献
102.
Yu Zhang Dr. Novruz G. Akhmedov Prof. Jeffrey L. Petersen Prof. Carsten Milsmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3042-3052
Luminescent seven-coordinated zirconium and hafnium complexes bearing three mono-anionic 2,2′-pyridylpyrrolide ligands and one chloride were synthesized. Solid-state structures and the dynamic behaviors in solution were probed by X-ray crystallography and variable temperature 1H NMR experiments, respectively. Absorption spectroscopy and time-dependent density functional theory (TD-DFT) calculations supported a hybrid of ligand-to-metal charge transfer (LMCT)/ligand-to-ligand charge transfer (LLCT) for the visible light absorption band. The complexes (MePMPMe)3MCl (M=Zr, Hf, MePMPMe=3,5-dimethyl-2-(2-pyridyl)pyrrolide) are emissive in solution at room temperature upon irradiation with visible light due to a combination of phosphorescence and fluorescence characterized by excited state lifetimes in the μs and low to sub-ns timescale, respectively. Electrochemical experiments revealed that the zirconium complex possesses a reversible redox event under highly reducing condition (−2.29 V vs. Fc+/0). 相似文献
103.
104.
105.
Dr. Xiang-Yang Liu Yi-Jie Zhang Xiyu Fei Prof. Man-Keung Fung Prof. Jian Fan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6788-6796
Spirocyclic compounds such as 9,9′-spirobifluorene (SBF) are becoming more and more attractive for use as host materials in organic optoelectronic devices. Herein, two dispirocycles, namely, dispiro[fluorene-9,9′-anthracene-10′,9′′-fluorene] and 10,10′′-diphenyl-10H,10′′H-dispiro[acridine-9,9′-anthracene-10′,9′′-acridine], were used for the construction of host materials 1 – 4 . The attached triphenylamino group determines the thermal, photophysical, electrochemical, and charge-transport properties, and therefore they have different electroluminescent performances. The device based on dispiro[fluorene-9,9′-anthracene-10′,9′′-fluorene] ( 2 ) and 10,10′′-diphenyl-10H,10′′H-dispiro[acridine-9,9′-anthracene-10′,9′′-acridine] ( 3 ) molecular platforms exhibited external quantum efficiencies of greater than 21 % with a very high power efficiency (≈100 lm W−1). These results demonstrate the potential of extending the application of dispirocyclic molecular platforms with inherent rigidity for developing highly efficient host materials for organic light-emitting diodes. 相似文献
106.
Chen Qinlei Xia Zhengbin Zhang Yanhong Wang Shumin 《Journal of Solid State Electrochemistry》2019,23(12):3399-3408
Journal of Solid State Electrochemistry - Polyaniline/diazonium salt/TiO2 nanotube arrays (PANI/DZ/TiO2 NAs), as a supercapacitor electrode material, are fabricated by two-step anodic oxidation of... 相似文献
107.
Dr. Longhai Zhang Prof. Tong Wei Dr. Zimu Jiang Prof. Zhuangjun Fan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):5022-5027
To optimize the cycle life and rate performance of lithium-ion batteries (LIBs), ultra-fine Fe2O3 nanowires with a diameter of approximately 2 nm uniformly anchored on a cross-linked graphene ribbon network are fabricated. The unique three-dimensional structure can effectively improve the electrical conductivity and facilitate ion diffusion, especially cross-plane diffusion. Moreover, Fe2O3 nanowires on graphene ribbons (Fe2O3/GR) are easily accessible for lithium ions compared with the traditional graphene sheets (Fe2O3/GS). In addition, the well-developed elastic network can not only undergo the drastic volume expansion during repetitive cycling, but also protect the bulk electrode from further pulverization. As a result, the Fe2O3/GR hybrid exhibits high rate and long cycle life Li storage performance (632 mAh g−1 at 5 A g−1, and 471 mAh g−1 capacity maintained even after 3000 cycles). Especially at high mass loading (≈4 mg cm−2), the Fe2O3/GR can still deliver higher reversible capacity (223 mAh g−1 even at 2 A g−1) compared with the Fe2O3/GS (37 mAh g−1) for LIBs. 相似文献
108.
Nonlinear Dynamics - In this paper, the current-controlled DC–DC buck converter from a new perspective are studied through the switching theory of flow, and the analytical conditions of the... 相似文献
109.
Two new Zn2Dy2 complexes were constructed from Zn (II) salen‐type Schiff base complex fragment and 2,6‐pyridinedimethanol (H2pdm) or its Br‐substituted analogue (4‐bromopyridine‐2,6‐diyl)dimethanol (H2Brpdm); their molecular formulas are [Zn2Dy2(L)2(pdm)2(MeOH)2](ClO4)2 [ 1 , H2L = N, N′‐ bis(3‐methoxysalicylidene)‐1,3‐diaminopropane] and [Zn2Dy2(L)2(Brpdm)2(MeOH)2](ClO4)2 [ 2 ], the Dy (III) ions of which have a NO7 triangular dodecahedral coordination sphere. The two complexes show not only ferromagnetic interaction but also field‐induced single‐molecule magnet (SMM) behavior, which are rare Dy (III)‐containing cluster complexes with the NO7 triangular dodecahedral coordination sphere that can show good magnetic relaxation. The energy barrier value of complex 2 is higher than those of complex 1 and the Dy (III) complexes with the DyNO7 triangular dodecahedral coordination configuration reported in the literature. 相似文献
110.
Zhang Tinggui Xi Ya Fei Shao-Ming 《International Journal of Theoretical Physics》2021,60(8):2909-2915
We study the Bell nonlocality of high dimensional quantum systems based on quantum entanglement. A quantitative relationship between the maximal expectation value B of Bell operators and the quantum entanglement concurrence C is obtained for even dimension pure states, with the upper and lower bounds of B governed by C.
相似文献