全文获取类型
收费全文 | 833篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
化学 | 588篇 |
晶体学 | 12篇 |
力学 | 5篇 |
数学 | 44篇 |
物理学 | 220篇 |
出版年
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 10篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 14篇 |
2013年 | 42篇 |
2012年 | 35篇 |
2011年 | 41篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 58篇 |
2007年 | 35篇 |
2006年 | 42篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 24篇 |
2002年 | 35篇 |
2001年 | 17篇 |
2000年 | 27篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 13篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有869条查询结果,搜索用时 15 毫秒
41.
42.
43.
Takanori Shibata Tsubasa Shizuno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(21):5514-5517
The first catalytic and enantioselective C H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C H bond activation. 相似文献
44.
Tomohito Morosaki Tsubasa Suzuki Wei‐Wei Wang Shigeru Nagase Takayoshi Fujii 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(36):9723-9725
Electronic effects on the central carbon atom of carbone, generated by the replacement of the SIV ligand of carbodisulfane (CDS) with other chalcogen ligands (Ph2E, E=S or Se), were investigated. The carbones Ph2E→C←SPh2(NMe) [E=S( 1 ) or Se( 2 )] were synthesized from the corresponding salts, and their molecular structures and electronic properties were characterized. The carbone 2 is the first carbone containing selenium as the coordinated atom. DFT calculations revealed the electronic structures of 1 and 2 , which have two lone pairs of electrons at the carbon center. The trend in HOMO energy levels, estimated by cyclic voltammetry measurements, for the carbones and CDS follows the order of 2 > 1 >CDS. Analysis of a doubly protonated dication and trication complex revealed that the central carbon atom of 2 behaves as a four‐electron donor. 相似文献
45.
Hajime Kawakami Makio C. Honda Shuichi Watanabe Toshiro Sino 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(2):461-468
We carried out time-series observations of 210Po and 210Pb radioactivity in the western North Pacific Ocean. The sinking fluxes of particulate organic carbon (POC) in the mesopelagic zone were estimated from 210Po radioactivity during several seasons in the subarctic and subtropical regions of the western North Pacific. The seasonal changes of POC fluxes at a depth of 400 m were larger in the subarctic region than in the subtropical region. The annual mean POC flux at a depth of 400 m was larger in the subarctic region (57 mgC m?2 day?1) than in the subtropical region (36 mgC m?2 day?1). The annual mean of the e-ratio (the ratio of POC flux to primary productivity) in the subarctic region (18 %) was about twice the e-ratio in the subtropical region (10 %). These results imply that the efficiency of the biological pump is larger in the subarctic region than in the subtropical region of the western North Pacific. 相似文献
46.
Katsumi Suzuki Asuki Toda Yingjie Liao Norihiko Kamata Zentaro Honda 《Molecular Crystals and Liquid Crystals》2015,621(1):124-128
We investigated crystallinity parameters and ordering domains of poly(3-hexylthiophene-2,5-diyl) blended in [6,6]-phenyl-C61-butyric acid methyl ester films, which were fabricated by pulsed electrospray deposition methods. The crystallinity parameter and the ordering domain were estimated from Raman and optical absorption spectra, respectively. As a result, they were improved with decreasing the off time of pulse voltage, corresponding to the slow evaporation speed of solvent. In addition, both the space-charge limited current mobility and the photoconversion efficiency showed same trend. A highest photoconversion efficiency of 1.11 % was achieved without the thermal annealing process after depositing the active layer. 相似文献
47.
Sodium cyclo-octaphosphate heptahydrate, (NaPO3)8 · 7H2O, has been made by heating lead cyclo-tetraphosphate at 340°C, dissolving the thermal product in a 3% aqueous solution of tetrasodium ethylene-diaminetetraacetate, and then crystallizing it by addition of sodium chloride and acetone to the solution. When the cyclo-octaphosphate was heated up to 400°C, it decomposed to produce phosphates with both shorter and longer chain lengths. A main product at 300° to 350°C was sodium cyclo-triphosphate, and the thermal product melted at about 630°C. 相似文献
48.
49.
Uchiyama N Matsunaga K Kiuchi F Honda G Tsubouchi A Nakajima-Shimada J Aoki T 《Chemical & pharmaceutical bulletin》2002,50(11):1514-1516
Trypanocidal constituents of dried leaves of Laurus nobilis L. (Lauraceae) were examined. Activity-guided fractionation of the methanol extract resulted in the isolation of two guaianolides, dehydrocostus lactone (1) and zaluzanin D (2), and a new p-menthane hydroperoxide, (1R,4S)-1-hydroperoxy-p-menth-2-en-8-ol acetate (3). The minimum lethal concentrations of these compounds against epimastigotes of Trypanosoma cruzi were 6.3, 2.5, and 1.4 microM, respectively. 相似文献
50.
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