全文获取类型
收费全文 | 1187篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
化学 | 868篇 |
晶体学 | 10篇 |
力学 | 9篇 |
数学 | 30篇 |
物理学 | 303篇 |
出版年
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 57篇 |
2012年 | 55篇 |
2011年 | 91篇 |
2010年 | 43篇 |
2009年 | 51篇 |
2008年 | 69篇 |
2007年 | 73篇 |
2006年 | 63篇 |
2005年 | 59篇 |
2004年 | 58篇 |
2003年 | 51篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 19篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 24篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1220条查询结果,搜索用时 15 毫秒
81.
Prof. Nobutaka Fujieda Kyohei Umakoshi Yuta Ochi Dr. Yosuke Nishikawa Prof. Sachiko Yanagisawa Prof. Minoru Kubo Prof. Genji Kurisu Prof. Shinobu Itoh 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13487-13492
The dinuclear copper enzyme, tyrosinase, activates O2 to form a (μ-η2:η2-peroxido)dicopper(II) species, which hydroxylates phenols to catechols. However, the exact mechanism of phenolase reaction in the catalytic site of tyrosinase is still under debate. We herein report the near atomic resolution X-ray crystal structures of the active tyrosinases with substrate l -tyrosine. At their catalytic sites, CuA moved toward l -tyrosine (CuA1 → CuA2), whose phenol oxygen directly coordinates to CuA2, involving the movement of CuB (CuB1 → CuB2). The crystal structures and spectroscopic analyses of the dioxygen-bound tyrosinases demonstrated that the peroxide ligand rotated, spontaneously weakening its O−O bond. Thus, the copper migration induced by the substrate-binding is accompanied by rearrangement of the bound peroxide species so as to provide one of the peroxide oxygen atoms with access to the phenol substrate's ϵ carbon atom. 相似文献
82.
Koji Yamamoto Kazuki Higuchi Masahiro Ogawa Hiromitsu Sogawa Shigeki Kuwata Yoshihiro Hayashi Susumu Kawauchi Toshikazu Takata 《化学:亚洲杂志》2020,15(3):356-359
We synthesised palladium and platinum complexes possessing cyclic and acyclic pincer‐type polyaromatic ligands and investigated their structural effect on the catalysis. The pincer‐type bis(6‐arylpyridin‐2‐yl)benzene skeleton was constructed via Kröhnke pyridine synthesis under transition metal‐free conditions on gram‐scale quantity. Ligand structure significantly influenced catalytic activity toward the platinum‐catalysed hydrosilylation of diphenyl acetylenes, despite the ligand‐independence of the conformations and electronic properties of these complexes. 相似文献
83.
Arunabhiram Chutia Riadh SahnounRamesh C. Deka Zhigang ZhuHideyuki Tsuboi Hiromitsu TakabaAkira Miyamoto 《Physica B: Condensed Matter》2011,406(9):1665-1672
Based on experimental findings models of amorphous graphene related carbon materials were generated using graphene nano flakes. On the optimized structures detailed local electronic properties were investigated using density functional theory. The electrical conductivities of all these models were also estimated using an in-house program based on tight-binding method. The calculated electrical conductivity values of all the models agreed well with the trend of calculated energy gap and graphitic character. 相似文献
84.
Md. Khorshed Alam Ryuji Miura Hideyuki Tsuboi Akira Endou Momoji Kubo 《Applied Surface Science》2010,257(5):1383-1389
Ceria plays an important role in catalysis, due to its ability to store and release oxygen depending on the condition present in the catalyst environment. To analyze the role of ceria in catalytic reactions, it is necessary to know the details of the interaction of ceria surface with environmentally sensitive molecules. This study was conducted using ultra accelerated quantum chemical molecular dynamics. Its purpose was to investigate the reduction process of the (1 1 1) and (1 1 0) surfaces of ceria with atomic hydrogen as well as water desorption mechanisms from the surfaces. This simulation demonstrated that when a high-energy colliding hydrogen atoms are adsorbed on the ceria, it pulls up an O atom from the ceria surfaces and results in the formation of a H2O molecule. This is the first dynamics simulation related to such reduction processes based on quantum chemistry. 相似文献
85.
The spin polarizations of hadrons inclusively produced by pp, γp and λp collisions are studied by the quark rearrangement model. The present model is a phenomenological one based on the relativistic spin equations of motion and using the quark distribution functions in hadrons and photon. A general success of the model is demonstrated. We find usefulness of the present formulation for studying the dynamics producing spin asymmetry distributions and the statics determining signs and magnitudes of the spin polarization by reflecting the characteristic quark structure in hadrons. 相似文献
86.
Quasi-solid-state dye-sensitized solar cells using room temperature molten salts and a low molecular weight gelator 总被引:1,自引:0,他引:1
Kubo W Kitamura T Hanabusa K Wada Y Yanagida S 《Chemical communications (Cambridge, England)》2002,(4):374-375
A dye-sensitized solar cell fabricated using the room temperature molten salt, 1-hexyl-3-methylimidazolium iodide, iodine and a low molecular weight gelator as a quasisolid-state electrolyte showed a 5.0% light-to-electricity conversion efficiency under AM 1.5 irradiation, and high-temperature stability. 相似文献
87.
88.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
89.
A practical synthesis of 1,2,3,4,5,6-hexahydro-1,5-imino-10-hydroxy-9-methoxy-3,8,11-trimethyl-3- benzazocin-4-one (3) as an ABC ring model compound of ecteinascidin 743 and safracins from 3-hydroxy-4-methoxy-5-methylbenzaldehyde (7) is described. The overall yield in 15 steps is 27%. 相似文献
90.
Armed crown ethers (1-4) bonding through an amine, amide, ether, or ester linkage to naphthyl group were found to display unique photophysical properties in the presence of guest salts. Complexation of PET fluoroionophores (1a and 1b) with Zn(2+) increased the fluorescence intensities of the host by a factor of 2.4 and 2.7, respectively. (1)H and (13)C NMR analyses of this complexation behavior of 1a revealed that Zn(2+) strongly coordinates with the armed crown nitrogen to cause a dramatic decrease in an intramolecular charge-transfer character. The armed crowns (2 and 3), bonding through an ether or ester linkage to a naphthalene, gave fluorescence quenching with guest thiocyanates. While the amide derivative (4) exhibited high Ba(2+) fluorescence selectivity and in the presence of this cation the host fluorescence intensity was by a factor of 3.69. 相似文献