全文获取类型
收费全文 | 1743篇 |
免费 | 46篇 |
国内免费 | 7篇 |
专业分类
化学 | 1354篇 |
晶体学 | 16篇 |
力学 | 19篇 |
数学 | 133篇 |
物理学 | 274篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 19篇 |
2017年 | 6篇 |
2016年 | 28篇 |
2015年 | 35篇 |
2014年 | 37篇 |
2013年 | 96篇 |
2012年 | 86篇 |
2011年 | 87篇 |
2010年 | 63篇 |
2009年 | 50篇 |
2008年 | 105篇 |
2007年 | 116篇 |
2006年 | 98篇 |
2005年 | 85篇 |
2004年 | 92篇 |
2003年 | 77篇 |
2002年 | 82篇 |
2001年 | 58篇 |
2000年 | 33篇 |
1999年 | 36篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 25篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 7篇 |
1969年 | 6篇 |
排序方式: 共有1796条查询结果,搜索用时 15 毫秒
101.
Yan Li Dr. Kazuki Fukushima Dr. Daniel J. Coady Dr. Amanda C. Engler Dr. Shaoqiong Liu Yuan Huang Dr. John S. Cho Dr. Yi Guo Dr. Lloyd S. Miller Dr. Jeremy P. K. Tan Dr. Pui Lai Rachel Ee Dr. Weimin Fan Prof. Yi Yan Yang Dr. James L. Hedrick 《Angewandte Chemie (International ed. in English)》2013,52(2):674-678
102.
103.
Dr. Kazuhiko Amakawa Dr. Lili Sun Dr. Chunsheng Guo Dr. Michael Hävecker Pierre Kube Prof. Dr. Israel E. Wachs Soe Lwin Prof. Dr. Anatoly I. Frenkel Dr. Anitha Patlolla Prof. Dr. Klaus Hermann Prof. Dr. Robert Schlögl Dr. Annette Trunschke 《Angewandte Chemie (International ed. in English)》2013,52(51):13553-13557
Highly dispersed molybdenum oxide supported on mesoporous silica SBA‐15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2–2.5 Mo atoms nm?2). X‐ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature‐programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O‐K‐edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity. 相似文献
104.
Hideaki Iizuka Shoko Watanabe Mayuko Koshikawa Yurie Matsumoto Yuki Aoyama Hideaki Ichiba Toshitaka Nabeshima Takeshi Fukushima 《Analytical and bioanalytical chemistry》2013,405(25):8137-8141
It has been reported that repeated phencyclidine (PCP) treatment induces schizophrenia-like behavior in mice. l-Tryptophan (Trp) concentrations in brain tissues of control (n?=?8) and PCP-treated mice (10 mg/kg/day, s.c., 14 days, n?=?10) were determined using high-performance liquid chromatography (HPLC) with fluorescence detection. The HPLC method involved pre-column fluorescence derivatization with (R)-(?)-4-(N,N-dimethylaminosulfonyl)-7-(3-isothiocyanatopyrrolidin-1-yl)-2,1,3-benzoxadiazole (DBD-PyNCS). Eight different parts of the brain, namely, the frontal cortex, nucleus accumbens, striatum, hippocampus, amygdala, thalamus, hypothalamus, and cerebellum, of both groups were investigated. A significant decrease in the l-Trp concentration in the nucleus accumbens (p?=?0.024) and hippocampus (p?=?0.027) was observed in PCP-treated mice, suggesting that alteration of the l-Trp metabolism might occur in these brain parts. 相似文献
105.
The effects of polyvinyl alcohol (PVA) molecules on the porosity of disk-like hematite particles produced from the forced hydrolysis reaction using two kinds of PVA molecules with a well-defined molecular weight and a high degree of saponification (PVA-105 and PVA-124) were investigated. It is evident from TEM and field-emission scanning electron microscope (FE-SEM) measurements that a fraction of particles lost their spherical habit and acquired a disk-like shape by the addition of small amounts of both PVA molecules, though no difference in the particle size between the two PVA systems was observed. FE-SEM images of the particles revealed that the disk-like hematite particles are made up of small cluster particles with a diameter of approx. 5–10 nm. The disk-like particles produced a rather lower concentration for PVA-124 with a higher molecular weight than that for PVA-105 with a lower molecular weight. This fact was due to the large number of hydroxy groups in PVA-124 molecules than in PVA-105; hydroxy groups act as adsorption sites onto polynuclear (PN) primary particles and cause pronounced effects on the formation and structure of particles during the aggregation of PN particles. It was clarified from N2 adsorption measurements at 77 K that the porosity of the hematite particles can be controlled from microporous to mesoporous by changing the concentrations of PVA-105 and PVA-124, as was classified into three groups, i.e., groups 1, 2, and 3. The control particles produced without PVA molecules, classified into group 1, showed type IV adsorption isotherms, and only the voids produced between spherical particles were detected as mesopores. On the other hand, the particles produced with small amounts of PVA produced micropores as classified in group 2. In this group, the particles produced uniform micropores after being outgassed at 100–200 °C. The hematite particles produced with high concentrations of PVAs were classified into group 3. In this group, the particles after being outgassed at lower temperature produced micropores with diameters between 0.6 and 2.0 nm, though the micropores in the particles changed to mesopores after outgassing at 300 °C. This mesopore formation was attributed to the elimination of the PVA-adsorbed layer by evacuation at 300 °C, i.e., the large voids residing in the disk-like hematite particles make the particles mesoporous. This mesopore formation was further confirmed by adsorption experiments of C6H6(benzene) and CCl4 molecules at 298 K. 相似文献
106.
Mari Iizuka Shoju Fukushima Yuki Goto Masaaki Okazaki Hideo Sawada Masato Yoshida 《Colloid and polymer science》2013,291(3):595-601
Head-to-head-type styrene and substituted styrene dimers bearing two fluoroalkyl end-groups have been efficiently synthesized by a simple reaction of perfluoroalkyl iodide with styrene under radical conditions as a mixture of meso and racemic forms. The meso form obtained from the mixture by recrystallization gave a crystal suitable for X-ray diffraction study and the crystal structure was found to be based on π-stacking of benzene rings and aggregation of fluoroalkyl chains. Dynamic light scattering measurements showed that meso-styrene dimers bearing two fluoroalkyl end-groups can form the nanometer size-controlled self-assemblies through the intermolecular π-stacking of benzene rings and aggregation of end-capped fluoroalkyl groups in methanol. Figure
Self-assembled meso-perfluorohexylated styrene dimer [C6F13–CH2CHPh–CHPh–CH2–C6F13] based on π-stacking of benzene rings and aggregation of fluoroalkyl chains: Fluorous domains are constructed by self-assembly of fluoroalkyl chains. 相似文献
107.
108.
Kazuhiko Semba Masataka Shinomiya Prof. Dr. Tetsuaki Fujihara Prof. Dr. Jun Terao Prof. Dr. Yasushi Tsuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7125-7132
The highly selective copper‐catalyzed hydroboration of allenes has been developed. Allylboranes and alkenylboranes were selectively prepared by the judicious choice of catalytic species (copper hydride and boryl copper). Furthermore, two types of alkenylboranes could be selectively synthesized by the choice of an appropriate ligand. Mechanistic studies confirmed that the protonation of a (Z)‐σ‐allyl copper species, which was isolated and structurally characterized by single‐crystal X‐ray diffraction, was a key step in these reactions. Besides allenes, this method is also applicable to the selective hydroboration of 1,3‐diene derivatives to afford allylboranes and homoallylboranes. 相似文献
109.
Prof. Takanori Suzuki Yuto Sakano Dr. Tomohiro Iwai Dr. Shinichi Iwashita Dr. Youhei Miura Dr. Ryo Katoono Prof. Hidetoshi Kawai Prof. Kenshu Fujiwara Prof. Yasushi Tsuji Prof. Takanori Fukushima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):117-123
When two benzene rings are fused to a tetraaryl‐o‐quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron‐donating alkoxy groups, 1 undergo reversible two‐electron oxidation to 2 2+, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec‐butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b 2+ and 2 c 2+, which represents an efficient method for enhancing circular‐dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X‐ray analysis of dication 2 2+ revealed π–π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response. 相似文献
110.
Yue Lu Koichi Nishio Shoichi Matsuda Yuki Toshima Hiroshi Ito Tomohiro Konno Kazuhiko Ishihara Souichiro Kato Kazuhito Hashimoto Shuji Nakanishi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(8):2240-2243
There is growing awareness that circadian clocks are closely related to the intracellular redox state across a range of species. As the redox state is determined by the exchange of the redox species, electrochemically controlled extracellular electron transfer (EC‐EET), a process in which intracellular electrons are exchanged with extracellular electrodes, is a promising approach for the external regulation of circadian clocks. Herein, we discuss whether the circadian clock can be regulated by EC‐EET using the cyanobacterium Synechococcus elongatus PCC7942 as a model system. In vivo monitoring of chlorophyll fluorescence revealed that the redox state of the plastoquionone pool could be controlled with EC‐EET by simply changing the electrode potential. As a result, the endogenous circadian clock of S. elongatus cells was successfully entrained through periodically modulated EC‐EET by emulating the natural light/dark cycle, even under constant illumination conditions. This is the first example of regulating the biological clock by electrochemistry. 相似文献