全文获取类型
收费全文 | 9342篇 |
免费 | 367篇 |
国内免费 | 61篇 |
专业分类
化学 | 6401篇 |
晶体学 | 93篇 |
力学 | 280篇 |
数学 | 808篇 |
物理学 | 2188篇 |
出版年
2023年 | 54篇 |
2022年 | 190篇 |
2021年 | 227篇 |
2020年 | 178篇 |
2019年 | 172篇 |
2018年 | 172篇 |
2017年 | 144篇 |
2016年 | 296篇 |
2015年 | 269篇 |
2014年 | 353篇 |
2013年 | 597篇 |
2012年 | 742篇 |
2011年 | 823篇 |
2010年 | 469篇 |
2009年 | 385篇 |
2008年 | 616篇 |
2007年 | 580篇 |
2006年 | 513篇 |
2005年 | 473篇 |
2004年 | 414篇 |
2003年 | 326篇 |
2002年 | 327篇 |
2001年 | 217篇 |
2000年 | 177篇 |
1999年 | 129篇 |
1998年 | 69篇 |
1997年 | 79篇 |
1996年 | 95篇 |
1995年 | 80篇 |
1994年 | 75篇 |
1993年 | 57篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 51篇 |
1989年 | 34篇 |
1988年 | 26篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 10篇 |
1972年 | 9篇 |
排序方式: 共有9770条查询结果,搜索用时 10 毫秒
91.
Sunyoung Kim Dan-Bi Kim Wenjie Jin Junghyuck Park Wonjin Yoon Yunyeol Lee 《Natural product research》2018,32(10):1193-1197
We evaluated organosulphur compounds in Allium vegetables, including garlic, elephant garlic and onion, using high-performance liquid chromatography. Among organosulphur compounds, elephant garlic had considerable γ-glutamyl peptides, and garlic had the highest alliin content. Onion had low level of organosulphur compounds than did elephant garlic and garlic. In addition, antioxidant capacities were evaluated by oxygen radical absorbance capacity (ORAC) values and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assay. The results showed that garlic had the highest antioxidant capacity, followed by elephant garlic and onion. Furthermore, a positive correlation was observed between antioxidant activities and organosulphur compounds (R > 0.77). Therefore, our results indicate that there was a close relationship between antioxidant capacity and organosulphur compounds in Allium vegetables. 相似文献
92.
Park Chang Min Wang Dengjun Heo Jiyong Her Namguk Su Chunming 《Journal of nanoparticle research》2018,20(4):1-10
Journal of Nanoparticle Research - Utilizing solar energy for hydrogen evolution is a great challenge for its insufficient visible-light power conversion. In this paper, we report a facile... 相似文献
93.
94.
Young Eun Jeun Joon Ho Park Joo Yeon Kim Prof. Hyun S. Ahn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(18):4039-4043
Mixed-metal oxyhydroxides—especially those of Ni and Fe—are one of the most active classes of materials known for catalyzing the oxygen evolution reaction (OER). Here, nanoparticulate mixed metal oxyhydroxides (of Ni, Fe, and Co) were prepared on an electrode surface by electrochemical reaction of a precursor solution encapsulated in aqueous nanodroplets (AnDs), with each of the droplets containing 10 s of attoliters of fluid. Electrode reactions and synthesis can be monitored in situ by electrochemistry as single AnD stochastically lands and interacts with the working electrode. Resultant metal oxyhydroxide nanoparticles can be size and composition controlled precisely by modulating the precursor solution stored in the AnD. Nanoparticulate metal oxyhydroxides were implemented as catalysts for the OER and exhibited superior catalysis compared to their thin-film counterparts, demonstrating a hundred-thousand-fold enhancement in atom efficiency at comparable turnover rates. 相似文献
95.
Minlang Yang Dr. In Seob Park Yasuhiro Miyashita Katsunori Tanaka Prof. Dr. Takuma Yasuda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(33):14059-14065
Herein, the universal design of high-efficiency stimuli-responsive luminous materials endowed with mechanochromic luminescence (MCL) and thermally activated delayed fluorescence (TADF) functions is reported. The origin of the unique stimuli-triggered TADF switching for a series of carbazole–isophthalonitrile-based donor–acceptor (D–A) luminogens is demonstrated based on systematic photophysical and X-ray analysis, coupled with theoretical calculations. It was revealed that a tiny alteration of the intramolecular D–A twisting in the excited-state structures governed by the solid morphologies is responsible for this dynamic TADF switching behavior. This concept is applicable to the fabrication of bicolor emissive organic light-emitting diodes using a single TADF emitter. 相似文献
96.
97.
Noting that a classical phase-space probability distribution w(q, p) may be calculated from moment expectation values {qmpn}, we inquire as to whether similar data in quantum mechanics would be adequate to determine the statistical operator ?. For the family of simultaneous (q, p) measurement schemes investigated, it turns out that such moments do not suffice to fix ?. Comparison of the empirical information that is adequate to determine ? with that required to find w(q, p) reveals that in a sense more data are needed for state determination in quantum statistics than are needed in the classical case. 相似文献
98.
ZnO nano-network structures with high porosity were prepared for use in the photoelectrodes of binder-free dye-sensitized solar cells (DSSCs) by DC sputtering and subsequent thermal oxidation. Zn thin films prepared at 100 °C showed nano-network structures with high porosity, while those prepared at 25 °C did not. This was partially attributed to the high mobility of sputter-deposited particles that arrived at the surface of the substrate and partially to a supersaturation mechanism. The prepared nano-network Zn was successfully transformed to ZnO without a morphological change via subsequent annealing in air. The power conversion efficiency of DSSCs based on the ZnO nano-network structures exhibited 10 times higher efficiency than those based on ZnO film prepared at 25 °C because of its large surface area for adsorption of dye molecules. The thickness of the ZnO nano-network structures increased linearly at 10 μm h?1 as a function of sputter time. As the film thickness increased, the power conversion efficiency of DSSCs increased from 1.09% to 1.82%. 相似文献
99.
K.H. Kwon D.W. Lee F. Marcellán S.B. Park 《Annali di Matematica Pura ed Applicata》2001,180(2):127-146
Given an orthogonal polynomial system {Q
n
(x)}
n=0
∞, define another polynomial system by where α
n
are complex numbers and t is a positive integer. We find conditions for {P
n
(x)}
n=0
∞ to be an orthogonal polynomial system. When t=1 and α1≠0, it turns out that {Q
n
(x)}
n=0
∞ must be kernel polynomials for {P
n
(x)}
n=0
∞ for which we study, in detail, the location of zeros and semi-classical character.
Received: November 25, 1999; in final form: April 6, 2000?Published online: June 22, 2001 相似文献
100.
Inorganic species formation in a discharged water generating (DWG) system consisting of a plane-to-plane electrode arrangement with a 20 kV, 20 mA and 1 kHz power source has been investigated. The DWG system is able to produce the various oxidants HNO2, HNO3 and O3, as well as OH radicals and many other unconfirmed radicals. These products can play an important role in the advanced oxidation of organic compounds and in rot protection. The pH of water discharged from the system for 20 min during inflow of natural air was about 3, nitrogen concentrations of nitrite and nitrate were 4.6 mg/L and 7.9 mg/L, respectively, residual dissolved ozone concentration was 0.7 mg/L and the oxidation power as measured by KI titration methods was approximately equivalent to 46 mg-O3/L. 相似文献