全文获取类型
收费全文 | 996篇 |
免费 | 25篇 |
国内免费 | 5篇 |
专业分类
化学 | 746篇 |
晶体学 | 10篇 |
力学 | 22篇 |
数学 | 52篇 |
物理学 | 196篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 3篇 |
2016年 | 23篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 48篇 |
2012年 | 47篇 |
2011年 | 72篇 |
2010年 | 27篇 |
2009年 | 33篇 |
2008年 | 55篇 |
2007年 | 71篇 |
2006年 | 76篇 |
2005年 | 75篇 |
2004年 | 64篇 |
2003年 | 49篇 |
2002年 | 62篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 18篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 2篇 |
排序方式: 共有1026条查询结果,搜索用时 0 毫秒
41.
Dr. Masanori Shigeno Takuya Okawa Masaya Imamatsu Kanako Nozawa-Kumada Yoshinori Kondo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10294-10297
We herein demonstrate that the amide base generated in situ from CsF and N(TMS)3 catalyzes the deprotonative coupling reactions of terminal alkynes with polyfluoroarenes, wherein mono- and dialkynylations occur efficiently for penta- and hexafluorobenzenes, respectively. Tetraalkynylated products could also be synthesized from dialkynylated compounds. 相似文献
42.
Dr. Takeshi Matsumoto Risa Yamamoto Dr. Masanori Wakizaka Dr. Akinobu Nakada Prof. Dr. Ho-Chol Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9609-9619
The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H2) important. A high-spin (hs) FeII complex with o-phenylenediamine (opda) ligands, [FeII(opda)3]2+ (hs- [6R] 2+), was reported showing photochemical H2 evolution. In addition, a low-spin (ls) [FeII(bqdi)3]2+ (bqdi: o-benzoquinodiimine) (ls- [0R] 2+) formation by O2 oxidation of hs- [6R] 2+, accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls- [0R] [PF6]2 can be reduced by hydrazine giving ls-[FeII(opda)(bqdi)2][PF6]2 (ls- [2R] [PF6]2) and ls-[FeII(opda)2(bqdi)][PF6]2 (ls- [4R] [PF6]2) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials. 相似文献
43.
Masanori Hara Naomi Hatakeyama Kuniaki Watanabe Katsunori Mori 《Journal of magnetism and magnetic materials》2009,321(5):423-428
The magnetization of GdCu induced by hydrogen uptake was measured within the temperature range of 4.2 to 300 K, occurring phase changes were followed by X-ray diffraction measurements at ambient temperature. The prepared GdCu powder of CsCl-type structure readily absorbed hydrogen at ambient temperature, where hydrogen pressure was below 100 kPa. Hydrogenation changed the magnetism of GdCu in a complex manner from an antiferromagnetic-like type to a paramagnetic-like one. The changes in magnetic properties of GdCu by hydrogenation are governed by hydrogen-induced disproportionation. Within the composition range 0<[H]/[GdCu]<1, GdCu disproportionated according to 2GdCu+H2→GdH2+GdCu2 . The magnetization was evaluated by the expression χtotal=(1-x)χGdCu+(x/2)(χGdH2+χGdCu2). GdCu hydride was not observed. Hydrogenation beyond [H]/[GdCu]>1 gave rise to the disproportionation of GdCu2 causing the change in magnetization. 相似文献
44.
45.
Zhaofei Li Jun Tang Masanori Watahiki 《Journal of Physics and Chemistry of Solids》2010,71(4):495-1635
We have successfully synthesized the α-FeSex binary tetragonal superconductors with nominal composition of FeSex (x=0.6-1.0) via conventional solid state reactions between Fe and Se sealed in quartz tubes. Fe and β-FeSe are the most commonly seen impurities in this binary system. A low-temperature annealing at 400 °C is found to be crucial to remove β-FeSe, which is the thermodynamic stable phase with hexagonal symmetry. For all the samples of FeSex, superconductivity is confirmed by magnetic measurements as well as resistivity measurements with their Tc at around 8 K. We noticed that their Tc does not vary with the different nominal Se amount. High-resolution synchrotron X-ray diffraction analysis revealed that the unit cell parameters of all these samples do not change within the error range, and their structure only tolerate the same very small amount of Se deficiency. Based on this study, we concluded that the α-FeSex superconductor only exist in a very narrow deficiency range. 相似文献
46.
47.
Toshiyuki Furutani Masanori Hatsuda Ritsuo Imashiro Masahiko Seki 《Tetrahedron: Asymmetry》1999,10(24):1317-4768
Enantiopure 1,1′-binaphthyl-2,2′-dicarboxylic acids (R)-1 and (S)-1 have been synthesized through the lipase-catalyzed kinetic resolution of the racemic 2,2-bis(hydroxymethyl)-1,1′-binaphthyl (±)-2 and subsequent oxidation of the hydroxymethyl groups. 相似文献
48.
Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferrimagnetic particle, barium ferrite. The complex modulus was measured before and after magnetization of the gel by dynamic viscoelastic measurements with a compressional strain. The gels showed a giant reduction in the storage modulus of approximately 10(7) Pa and also in the loss modulus of approximately 10(6) Pa due to magnetization. The reduction increased with increasing volume fraction of ferrite, and it was nearly independent of the frequency. It was also found that the change in the modulus was nearly independent of the magnetization direction and irradiation time of the magnetic fields to the gel. The magnetic gels demonstrating the giant reduction in the dynamic modulus showed a large nonlinear viscoelastic response. It was observed that the magnetic gel was deformed slightly due to magnetization. The observed giant complex modulus reduction could be attributed to the nonlinear viscoelasticity and deformation caused by magnetization. Magnetism, nonlinear viscoelasticity, and effects of magnetization on the morphological and shape changes were discussed. 相似文献
49.
Koumura N Wang ZS Mori S Miyashita M Suzuki E Hara K 《Journal of the American Chemical Society》2006,128(44):14256-14257
We designed and synthesized new alkyl-functionalized organic dyes, MK-1 and MK-2, for dye-sensitized solar cells (DSSCs). Based on the MK-2 dye, a high performance of efficiency (eta, 7.7%; short-circuit current density Jsc = 14.0 mA cm-2, open-circuit voltage Voc = 0.74 V, and fill factor FF = 0.74) was achieved under AM 1.5 G irradiation (100 mW cm-2). Remarkably, the relatively higher Voc for DSSCs based on MK-1 and MK-2 dyes, which have long alkyl chains, were observed among the organic dyes caused by the increasing of the electron lifetime in the conduction band of TiO2. Our molecular design of alkyl-functionalized dyes strongly suggests the promising performance of molecular photovoltaics based on organic dyes. 相似文献
50.
Kunishima M Tokaji M Matsuoka K Nishida J Kanamori M Hioki K Tani S 《Journal of the American Chemical Society》2006,128(45):14452-14453
Mere chemical generation of ceramide and related double-chain lipids in the membrane of small unilamellar vesicles (SUVs) induces fusion of the vesicles. The lipids can be successfully prepared by dehydrocondensation between single-chain lipids (fatty acids and sphingosine or its analogues) in a lipid bilayer of the SUV by using a combination of 2-chloro-4,6-dimethoxy-1,3,5-triazine and amphiphilic tertiary amine catalysts, a process that can be compared to a successive enzyme model system for a fatty acyl-CoA synthetase followed by acyltransferase. The SUV spontaneously undergoes membrane fusion upon this internal chemical stimulation by the artificial enzyme system. 相似文献