全文获取类型
收费全文 | 824篇 |
免费 | 59篇 |
国内免费 | 9篇 |
专业分类
化学 | 607篇 |
晶体学 | 7篇 |
力学 | 8篇 |
数学 | 84篇 |
物理学 | 186篇 |
出版年
2023年 | 11篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 12篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 39篇 |
2015年 | 20篇 |
2014年 | 33篇 |
2013年 | 49篇 |
2012年 | 52篇 |
2011年 | 61篇 |
2010年 | 44篇 |
2009年 | 32篇 |
2008年 | 36篇 |
2007年 | 44篇 |
2006年 | 42篇 |
2005年 | 43篇 |
2004年 | 26篇 |
2003年 | 30篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1973年 | 4篇 |
1970年 | 5篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有892条查询结果,搜索用时 359 毫秒
81.
Ryota Seto Takashi Sato Takahiro Kojima Katsumoto Hosokawa Yasuhito Koyama Gen‐Ichi Konishi Toshikazu Takata 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3658-3667
Syntheses of 2,2′‐bisalcoholic group‐substituted 9,9′‐spirobifluorene monomers 2 were performed by the reaction of 2,2′‐dihydroxy‐9,9′‐spirobifluorene 2a with haloalcohols. Polycarbonates consisting of 9,9′‐spirobifluorene skeleton in the main chain (PC 4 ) were synthesized by the polycondensation of 2,2′‐bisalcoholic monomers 2 and triphosgene or diphenyl carbonate. PC 4 showed good thermal stability: the 5% weight loss temperature was over 330 °C under both nitrogen and air atmospheres. The glass transition temperature was in a range of 16–269 °C estimated by differential scanning calorimetry, depending on the flexibility of the alkylene or oxyethylene chains of 2 . PC 4 showed high solubility toward ordinary organic solvents such as CHCl3, benzene, and THF, making possible the preparation of the flexible thin films. Very high refractive index in a range of 1.62–1.66 at 589 nm was observed although PC 4 consists only of C, H, and O atoms, whereas very low degree of birefringence was confirmed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3658–3667, 2010 相似文献
82.
We prove the global existence of analytic solutions to the Cauchy problem for the cubic Schrödinger equation in space dimension n?3 for sufficiently small data with exponential decay at infinity. Minimal regularity assumption regarding scaling invariance is imposed on the Cauchy data. 相似文献
83.
用透射法测量了能量为79AMeV的17C在12C反应靶上的反应截面;利用有限力程Glauber模型对17C的密度分布进行了分析.由高能区(965AMeV)相互作用截面数据分析认为17C具有谐振子密度分布,但拟合本实验结果及高能区实验数据发现,17C的中子密度分布中存在一个尾巴;假设17C密度为芯核加单粒子密度分布形式,分析认为17C的价中子主要处于1d5/2?轨道. 相似文献
84.
Tungsten microcone arrays with a high aspect ratio are formed by the cumulative nanosecond pulsed-Nd:YAG laser irradiation
of single-crystal tungsten under low pressure in an inert atmosphere. The morphology of the microcones and their density were
strongly affected by the number of laser pulses. The microcones grew to a length of 20 μm with a diameter of about 1.5 μm
at the tip after irradiation with more than 1200 pulses under our experimental conditions. They may have potential applications
for emission cathodes in a field-emission display (FED) and in microelectronic devices.
Received: 8 January 2001 / Accepted: 13 June 2001 / Published online: 2 October 2001 相似文献
85.
T. Minamisono Y. Nojiri K. Matsuta K. Takeyama A. Kitagawa T. Ohtsubo A. Ozawa 《Hyperfine Interactions》1990,59(1-4):31-40
Electromagnetic moments of doubly closed shell ±1 nucleon nuclei were studied. Recent technical developments of the β-NMR
was shown that was applicable for the polarized β emitters. Also, the implication of those new moments were discussed especially
on the nuclear interactions and non nucleonic degrees of freedom. 相似文献
86.
Ryota Inoue Masashi Hasegawa Tohru Nishinaga Kenji Yoza Yasuhiro Mazaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(9):2772-2776
A series of thiacalix[n]dithiothiophenes (n=4–10) was prepared by a facile method and X‐ray analysis was used to determine the molecular structures of square‐ (4‐mer) and pentagonal‐shaped macrocycles (5‐mer). In the cyclic voltammograms, reversible multielectron redox processes, which are due to electronic delocalization, were observed at low oxidation potentials. The cyclic 4‐mer acted as a “Janus‐head” cavitand for two C60 molecules, whereas the 5‐ and 6‐mer formed stable 1:1 complexes with C60 . 相似文献
87.
Hideki Shimura Ryota Tanaka Yoshiaki Shimada Kazuo Yamashiro Nobutaka Hattori Takao Urabe 《BMC biochemistry》2017,18(1):14
Background
Peptides with cytoprotective functions, including antioxidants and anti-infectives, could be useful therapeutics. Carnosine, β-alanine-histidine, is a dipeptide with anti-oxidant properties. Tripeptides of Ala-His-Lys, Pro-His-His, or Tyr-His-Tyr are also of interest in this respect.Results
We synthesized several histidine-containing peptides including glycine or alanine, and tested their cytoprotective effects on hydrogen peroxide toxicity for PC12 cells. Of all these peptides (Gly-His-His, Ala-His-His, Ala-His-Ala, Ala-Ala-His, Ala-Gly-His, Gly-Ala-His (GAH), Ala-His-Gly, His-Ala-Gly, His-His-His, Gly-His-Ala, and Gly-Gly-His), GAH was found to have the strongest cytoprotective activity. GAH decreased lactate dehydrogenase (LDH) leakage, apoptosis, morphological changes, and nuclear membrane permeability changes against hydrogen peroxide toxicity in PC12 cells. The cytoprotective activity of GAH was superior to that of carnosine against hydrogen peroxide toxicity in PC12 cells. GAH also protected PC12 cells against damage caused by actinomycin D and staurosporine. Additionally, it was found that GAH also protected SH-SY5Y and Jurkat cells from damage caused by hydrogen peroxide, as assessed by LDH leakage.Conclusion
Thus, a novel tripeptide, GAH, has been identified as having broad cytoprotective effects against hydrogen peroxide-induced cell damage.88.
Kawamoto S Takasu M Miyakawa T Morikawa R Oda T Futaki S Nagao H 《The Journal of chemical physics》2011,134(9):095103
Arginine-rich peptide and Antennapedia are cell-penetrating peptides (CPPs) which have the ability to permeate plasma membrane. Deformation of the plasma membrane with CPPs is the key to understand permeation mechanism. We investigate the dynamics of CPP and the lipid bilayer membrane by coarse-grained simulation. We found that the peptide makes inverted micelle in the lipid bilayer membrane, when the attractive potential between the peptide and lipid heads is strong. The inverted micelle is formed to minimize potential energy of the peptide. For vesicle membrane, the peptide moves from the outer vesicle to the inner vesicle through the membrane. The translocation of the peptide suggests inverted micelle model as a possible mechanism of CPPs. 相似文献
89.
The dehydrogenative cycloaddition of dieneynes, which possess a diene in the form of a styrene moiety and a dienophile in the form of an alkyne moiety, produces naphthalene derivatives when heated. It was found that a key requirement of this process is the presence of a silyl group attached to the alkyne moiety, which forces a dehydrogenation reaction to occur. 相似文献
90.
We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H(2)ase) by CO. We present a model study, using a NiRu H(2)ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru(II) center rather than taking an axial position on the Ni(II) center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H(2)ase by complexing to the Fe(II) center. 相似文献