全文获取类型
收费全文 | 2544篇 |
免费 | 80篇 |
国内免费 | 8篇 |
专业分类
化学 | 1744篇 |
晶体学 | 25篇 |
力学 | 29篇 |
数学 | 114篇 |
物理学 | 720篇 |
出版年
2023年 | 14篇 |
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 32篇 |
2017年 | 24篇 |
2016年 | 41篇 |
2015年 | 57篇 |
2014年 | 49篇 |
2013年 | 118篇 |
2012年 | 148篇 |
2011年 | 164篇 |
2010年 | 81篇 |
2009年 | 74篇 |
2008年 | 153篇 |
2007年 | 160篇 |
2006年 | 137篇 |
2005年 | 154篇 |
2004年 | 136篇 |
2003年 | 108篇 |
2002年 | 120篇 |
2001年 | 58篇 |
2000年 | 42篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 25篇 |
1996年 | 40篇 |
1995年 | 22篇 |
1994年 | 32篇 |
1993年 | 22篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 19篇 |
1985年 | 40篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 29篇 |
1980年 | 20篇 |
1979年 | 30篇 |
1978年 | 28篇 |
1977年 | 30篇 |
1976年 | 17篇 |
1975年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有2632条查询结果,搜索用时 31 毫秒
971.
Matyja A Rozanska M Adachi I Aihara H Aulchenko V Aushev T Bahinipati S Bakich AM Balagura V Barberio E Bedny I Bhardwaj V Bitenc U Bondar A Bozek A Bracko M Brodzicka J Browder TE Chang MC Chang P Chen A Chen KF Cheon BG Chistov R Cho IS Choi Y Choi YK Dalseno J Dash M Eidelman S Fratina S Gabyshev N Golob B Ha H Haba J Hara T Hayasaka K Hazumi M Heffernan D Hokuue T Hoshi Y Hou WS Hyun HJ Iijima T Ikado K Inami K Ishikawa A Ishino H Itoh R Iwasaki Y Kaji H Kajiwara S Kang JH Katayama N 《Physical review letters》2007,99(19):191807
We report an observation of the decay B{0}-->D{*-}tau{+}nu{tau} in a data sample containing 535x10{6} BB pairs collected with the Belle detector at the KEKB asymmetric-energy e{+}e{-} collider. We find a signal with a significance of 5.2sigma and measure the branching fraction B(B{0}-->D{*-}tau{+}nu{tau})=(2.02{-0.37}{+0.40}(stat)+/-0.37(syst))%. This is the first observation of an exclusive B decay with a b-->ctaunu{tau} transition. 相似文献
972.
We investigate the dependence of the intensity of radiation due to high-harmonic generation as a function of the wavelength lambda of the fundamental driver field. Superimposed on a smooth power-law dependence observed previously, we find surprisingly strong and rapid fluctuations on a fine lambda scale. We identify the origin of these fluctuations in terms of quantum path interferences with up to five returning orbits significantly contributing. 相似文献
973.
We present a dramatic enhancement [Phys. Rev. Lett. 91, 043002 (2003)] of high-order harmonic generation by simultaneous irradiation of booster harmonics. A key feature of our experiment is the use of mixed gases (Xe and He) with different ionization energies. The harmonics from Xe atoms act as a booster to increase the harmonic yield from He by a factor of 4 x 10(3). The dominance of the dramatic enhancement effect is supported by simulation with the time-dependent Schr?dinger equation as well as the observed spatial characteristic of the generated harmonics and dependence on medium conditions. 相似文献
974.
Mizuk R Abe K Adachi I Aihara H Anipko D Aulchenko V Aushev T Bakich AM Balagura V Barberio E Bay A Bedny I Belous K Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Brodzicka J Browder TE Chang MC Chen A Chen KF Chen WT Cheon BG Chistov R Choi Y Choi YK Cole S Dalseno J Danilov M Drutskoy A Eidelman S Epifanov D Fratina S Gabyshev N Garmash A Gershon T Gokhroo G Golob B Ha H Haba J Hayasaka K Hayashii H Hazumi M Heffernan D Hokuue T Hoshi Y Hou S Hou WS Iijima T Ikado K Imoto A Inami K 《Physical review letters》2007,98(26):262001
We report the results of several studies of the Lambda(c)(+)pi(+)pi(-)X final state in continuum e(+)e(-) annihilation data collected by the Belle detector. An analysis of angular distributions in Lambda(c)(2880)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decays strongly favors a Lambda(c)(2880)(+) spin assignment of 5/2 over 3/2 or 1/2. We find evidence for Lambda(c)(2880)(+)-->Sigma(c)(2520)(0,++)pi(+,-) decay and measure the ratio of Lambda(c)(2880)(+) partial widths Gamma(Sigma(c)(2520)pi)/Gamma(Sigma(c)(2455)pi)=0.225+/-0.062+/-0.025. This value favors the Lambda(c)(2880)(+) spin-parity assignment of 5/2(+) over 5/2(-). We also report the first observation of Lambda(c)(2940)(+)-->Sigma(c)(2455)(0,++)pi(+,-) decay and measure Lambda(c)(2880)(+) and Lambda(c)(2940)(+) mass and width parameters. These studies are based on a 553 fb(-1) data sample collected at or near the Upsilon(4S) resonance at the KEKB collider. 相似文献
975.
Synthesis,Structures, and Properties of Crystalline Salts with Radical Anions of Metal‐Containing and Metal‐Free Phthalocyanines 下载免费PDF全文
Dr. Dmitri V. Konarev Dr. Alexey V. Kuzmin Dr. Maxim A. Faraonov Dr. Manabu Ishikawa Dr. Salavat S. Khasanov Dr. Yoshiaki Nakano Dr. Akihiro Otsuka Prof. Hideki Yamochi Prof. Dr. Gunzi Saito Prof. Rimma N. Lyubovskaya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1014-1028
Radical anion salts of metal‐containing and metal‐free phthalocyanines [MPc(3?)].?, where M=CuII, NiII, H2, SnII, PbII, TiIVO, and VIVO ( 1 – 10 ) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C?Nimine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1 – 10 show new bands at 833–1041 nm in the NIR range, whereas the Q‐ and Soret bands are blue‐shifted by 0.13–0.25 eV (38‐92 nm) and 0.04–0.07 eV (4–13 nm), respectively. Radical anions with NiII, SnII, PbII, and TiIVO have S=1/2 spin state, whereas [CuIIPc(3?)].? and [VIVOPc(3?)].? containing paramagnetic CuII and VIVO have two S=1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal‐free phthalocyanine radical anions [H2Pc(3?)].? (linewidth of 0.08–0.24 mT), broad EPR signals are manifested (linewidth of 2–70 mT) with g‐factors and linewidths that are strongly temperature‐dependent. Salt 11 containing the [NaIPc(2?)]? anions as well as previously studied [FeIPc(2?)]? and [CoIPc(2?)]? anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3?)].? in 1 – 10 . 相似文献
976.
Bond Formation and Coupling between Germyl and Bridging Germylene Ligands in Dinuclear Palladium(I) Complexes 下载免费PDF全文
Dr. Makoto Tanabe Shumpei Omine Naoko Ishikawa Prof. Dr. Kohtaro Osakada Yoshihiro Hayashi Prof. Dr. Susumu Kawauchi 《Angewandte Chemie (International ed. in English)》2015,54(9):2679-2683
The dinuclear palladium(I) complexes [L(Ar2HGe)Pd(μ‐GeAr2)2Pd(GeHAr2)L] (Ar=Ph, p‐Tol; L=PMe3, tBuNC) contain terminal germyl and bridging germylene ligands with the experimentally observed Ge???Ge bond lengths of 2.8263(4) Å (L=PMe3) and 2.928(1) Å (L=tBuNC), which are close to the longest Ge? Ge bond reported to date [2.714(1) Å]. Significant Ge???Ge interactions between the germylene and germyl ligands (PMe3 complexes > tBuNC complexes) are supported by DFT calculations, Wiberg bond indices (WBI), and natural bond orbital (NBO) analyses. Exchanging tBuNC for PMe3 ligands increases the Ge???Ge interaction, and simultaneously activates two Pd? Ge bonds. Adding the chelating diphosphine 1,2‐bis(diethylphosphino)ethane (depe) to the PMe3 complexes results in the intramolecular coupling of germyl and germylene ligands followed by extrusion of a digermane. 相似文献
977.
Amphiphilic Organic–Inorganic Hybrid Zeotype Aluminosilicate like a Nanoporous Crystallized Langmuir–Blodgett Film 下载免费PDF全文
Dr. Takuji Ikeda Dr. Norihito Hiyoshi Dr. Shun‐ichi Matsuura Dr. Tetsuya Kodaira Takuma Nakaoka Ami Irisa Miki Kawano Dr. Katsutoshi Yamamoto 《Angewandte Chemie (International ed. in English)》2015,54(27):7994-7998
A new organic–inorganic hybrid zeotype compound with amphiphilic one‐dimensional nanopore and aluminosilicate composition was developed. The framework structure is composed of double aluminosilicate layers and 12‐ring nanopores; a hydrophilic layer pillared by Q2 silicon atom species and a lipophilic layer pillared by phenylene groups are alternately stacked, and 12‐ring nanopores perpendicularly penetrate the layers. The framework topology looks similar to that of an AFI‐type zeolite but possesses a quasi‐multidimensional pore structure consisting of a 12‐ring channel and intersecting small pores equivalent to 8‐rings. The hybrid material with alternately laminated lipophilic and hydrophilic nanospaces can be assumed as a crystallized Langmuir–Blodgett film. It demonstrates microporous adsorption for both hydrophilic and lipophilic adsorptives, and its outer surface tightly adsorbs lysozyme whose molecular size is much larger than its micropore opening. Our results suggest the possibility of designing porous adsorbent with high amphipathicity. 相似文献
978.
Takatoshi Ito Toshiyuki Iwai Takeo Nakai Masatoshi Mihara Takumi Mizuno Toshinobu Ohno Akira Ishikawa Jun‐ichi Kobayashi 《Heteroatom Chemistry》2016,27(5):336-342
Cyclic phosphorus compounds, 6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐oxide derivatives, were efficiently synthesized by the Friedel–Crafts reaction of 2‐hydroxybiphenyls with phosphorus trichloride in the presence of superacids, especially trifluoromethanesulfonic acid (TfOH) as a catalyst. TfOH was investigated for the first time as an effective catalyst for the aromatic phosphination of 2‐hydroxybiphenyls. 相似文献
979.
Yusuke Ootani Aya Satoh Yu Harabuchi Tetsuya Taketsugu 《Journal of computational chemistry》2020,41(16):1549-1556
The semiclassical tunneling method is applied to evaluate the tunneling splitting of tropolone due to the intramolecular proton transfer in the electronic excited state, first time, in a framework of the trajectory on-the-fly molecular dynamics (TOF-MD) approach. To prevent unphysical zero-point vibrational energy transfer among the normal modes of vibration, quantum zero-point vibrational energies are assigned only to the vibrational modes related to intramolecular proton transfer, whereas the remaining modes are treated as bath modes. Practical ways to determine the tunnel-initiating points and tunneling path are introduced. It is shown that the tunneling splitting decreases as the bath-mode energy increases. The experimental tunneling splitting value is well reproduced by the present TOF-MD approach based on the Wentzel-Kramers-Brillouin (WKB) approximation. 相似文献
980.
Daisuke Iida Yasunari Kondo Mihoko Sowa Toru Sugiyama Motoaki Iwaya Tetsuya Takeuchi Satoshi Kamiyama Isamu Akasaki 《固体物理学:研究快报》2013,7(3):211-214
Strain relaxation in a GaInN/GaN heterostructure is analyzed by combining in situ X‐ray diffraction (XRD) monitoring and ex situ observations. Two different characteristic thicknesses of GaInN films are defined by the evolution of in situ XRD from the full width at half‐maximum of symmetric (0002) diffraction as a function of GaInN thickness. This in situ XRD measurement enables to clearly observe the critical thicknesses corresponding to strain relaxation in the GaInN/GaN heterostructure caused by the formation of surface pits with bent threading dislocations and the generation of misfit dislocations on GaInN during growth. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献