全文获取类型
收费全文 | 661篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
化学 | 547篇 |
晶体学 | 11篇 |
力学 | 11篇 |
数学 | 28篇 |
物理学 | 87篇 |
出版年
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 27篇 |
2012年 | 38篇 |
2011年 | 42篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 41篇 |
2007年 | 43篇 |
2006年 | 50篇 |
2005年 | 58篇 |
2004年 | 32篇 |
2003年 | 37篇 |
2002年 | 40篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 8篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有684条查询结果,搜索用时 15 毫秒
31.
Applications of microelectromechanical systems (MEMS) technology are widespread in both industrial and research fields providing
miniaturized smart tools. In this review, we focus on MEMS applications aiming at manipulations and characterization of biomaterials
at the single molecule level. Four topics are discussed in detail to show the advantages and impact of MEMS tools for biomolecular
manipulations. They include the microthermodevice for rapid temperature alternation in real-time microscopic observation,
a microchannel with microelectrodes for isolating and immobilizing a DNA molecule, and microtweezers to manipulate a bundle
of DNA molecules directly for analyzing its conductivity. The feasibilities of each device have been shown by conducting specific
biological experiments. Therefore, the development of MEMS devices for single molecule analysis holds promise to overcome
the disadvantages of the conventional technique for biological experiments and acts as a powerful strategy in molecular biology.
Figure Towards single bio molecular handling and characterization by MEMS 相似文献
32.
Wada M Yokota C Ogata Y Kuroda N Yamada H Nakashima K 《Analytical and bioanalytical chemistry》2008,391(3):1057-1062
A sensitive high-performance liquid chromatography (HPLC)–fluorescence method for determination of morphine (Mor) in rat brain
and blood microdialysates was developed using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. Mor was labeled with DIB-Cl under mild reaction conditions (at room temperature
for 10 min). The separation of DIB-Mor was carried out on an octadecylsilica (ODS) column with CH3CN/0.1 M acetate buffer (pH 5.4) within 14 min. The detection limits of Mor in brain and blood microdialysates at a signal-to-noise
ratio of 3 were 0.4 and 0.6 ng mL−1, respectively. The proposed method was successfully applied to the preliminarily study of potential pharmacokinetic interaction
between Mor and diclofenac. 相似文献
33.
Fe K‐Edge X‐ray Absorption Fine Structure Determination of γ‐Al2O3‐Supported Iron‐Oxide Species 下载免费PDF全文
Dr. Atsuko Tomita Dr. Takeshi Miki Takeru Tango Tatsuro Murakami Hideyuki Nakagawa Dr. Yutaka Tai 《Chemphyschem》2015,16(9):2015-2020
The structure of FeOx species supported on γ‐Al2O3 was investigated by using Fe K‐edge X‐ray absorption fine structure (XAFS) and X‐ray diffraction (XRD) measurements. The samples were prepared through the impregnation of iron nitrate on Al2O3 and co‐gelation of aluminum and iron sulfates. The dependence of the XRD patterns on Fe loading revealed the formation of α‐Fe2O3 particles at an Fe loading of above 10 wt %, whereas the formation of iron‐oxide crystals was not observed at Fe loadings of less than 9.0 wt %. The Fe K‐edge XAFS was characterized by a clear pre‐edge peak, which indicated that the Fe?O coordination structure deviates from central symmetry and that the degree of Fe?O?Fe bond formation is significantly lower than that in bulk samples at low Fe loading (<9.0 wt %). Fe K‐edge extended XAFS oscillations of the samples with low Fe loadings were explained by assuming an isolated iron‐oxide monomer on the γ‐Al2O3 surface. 相似文献
34.
Effects of polyethylene spacer length in polymeric electrolytes on gelation of ionic liquids and ionogel properties 下载免费PDF全文
Jun'ichi Nagasawa Sonoko Wakahara Hajime Matsumoto Hideyuki Kihara Masaru Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):249-255
Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH2)m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 249–255 相似文献
35.
Quinolone Analogs 14: Synthesis of Antimalarial 1‐Aryl‐3‐(4‐quinolon‐2‐yl)ureas and Related Compounds 下载免费PDF全文
Yoshihisa Kurasawa Kiminari Yoshida Naoki Yamazaki Kenji Sasaki Yoshito Zamami Zhao Min Atsumi Togi Hideyuki Ito Eisuke Kaji Haruhiko Fukaya 《Journal of heterocyclic chemistry》2014,51(Z1):E241-E248
The 4‐quinolone‐2‐carbohydrazide 6a was converted into 1‐aryl‐3‐(4‐quinolon‐2‐yl)ureas 5a , 5b , 5c , 5d , 5e , 1‐aryl‐3‐(4‐quinolon‐2‐yl)imidazolidine‐2,4‐diones 9a , 9b , and N‐(4‐quinolon‐2‐yl)carbamates 10a , 10b via 4‐quinolone‐2‐carbonylazide 7a . The 4‐methoxyquinoline‐2‐carbohydrazide 6b was also transformed into 1‐aryl‐3‐(4‐methoxyquinolin‐2‐yl)ureas 11a , 11b , 11c , 11d , 1‐aryl‐3‐(4‐methoxyquinolin‐2‐yl)imidazolidine‐2,4‐diones 12a , 12b , and N‐(4‐methoxyquinolin‐2‐yl)carbamates 13a , 13b via 4‐methoxyquinoline‐2‐carbonylazide 7b . Some of the 1‐aryl‐3‐(4‐quinolon‐2‐yl)ureas 5a , 5b , 5c , 5d , 5e showed the in vitro antimalarial activity to chloroquine‐resistant Plasmodium falciparum, wherein IC50 was 0.93 to 4.00 μM. 相似文献
36.
Kenichiro Todoroki Hidemichi Etoh Hideyuki Yoshida Hitoshi Nohta Masatoshi Yamaguchi 《Analytical and bioanalytical chemistry》2009,394(1):321-327
We have developed a novel pre-column fluorescence derivatization reagent for amines, F-trap pyrene. This reagent comprises
a fluorescent pyrene moiety, an amine-reactive Marshall linker, and a fluorophilic perfluoroalkyl group known as fluorous
tag. When the reagent reacts with aliphatic amines and amino acids to give fluorescent derivatives, the fluorous tag in the
reagent is eliminated simultaneously. Therefore, excess unreacted reagents in the derivatization reaction solution still have
the fluorous tag and could be removed by fluorous solid-phase extraction selectively before high-performance liquid chromatography
(HPLC) analysis. By using this reagent, 13 kinds of aliphatic amine (C2–C16) derivatives can be separated within 40 min by reversed-phase HPLC with gradient elution. In this chromatogram, unreacted
reagents peak at around 28 min, greatly decrease after fluorous solid-phase extraction, and do not interfere with the quantification
of each amine. The detection limits (S/N = 3) for examined aliphatic amines are 3.6–25 fmol per 20 μL injection. We have also applied this reagent successfully to
the amino acid analysis.
相似文献
Kenichiro TodorokiEmail: |
37.
Makoto Yoshimoto Hideyuki Sakamoto Hiroshi Shirakami 《Colloids and surfaces. B, Biointerfaces》2009,69(2):281-287
Tetrameric bovine liver catalase (BLC) is unstable because of its dissociation into subunits at low enzyme concentrations and the conformational change of the subunits at high temperatures. In this work, for stabilization of BLC, the enzyme was covalently conjugated with liposome membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-glutaryl (NGPE). The NGPE, which was responsible for the BLC/membrane coupling, was altered from 0.05 to 0.2 in its liposomal mole fraction fG. The catalase-conjugated liposome (CCL) with fG of 0.15 showed the maximum number of the conjugated BLC molecules of 28 per liposome. The reactivity of CCLs to H2O2 was as high as that of free BLC at 25 °C in Tris–HCl buffer of pH 7.4. Among the CCLs, the catalyst with fG of 0.15 was the most stable at 55 °C in its enzyme activity in the buffer because the appropriate number of BLC/liposome covalent bonding prevented the dissociation-induced enzyme deactivation. Furthermore, the CCL showed much higher stability at 55 °C than the free BLC/enzyme-free liposome mixture and free BLC at the low BLC concentration of 340 ng/mL. This was because BLC in the CCL was located in the vicinity of the host membrane regardless of the catalyst concentration, which could induce the effective stabilization effect of the membrane on the enzyme tertiary structure as indicated by the intrinsic tryptophan fluorescence analysis. The results obtained demonstrate the high structural stability of BLC in the CCL system, which was derived from the covalent bonding and interaction between BLC and liposomes. 相似文献
38.
39.
Stabilization of the spark-discharge point on a sample surface by laser irradiation for steel analysis. 总被引:1,自引:0,他引:1
A combined technique with laser irradiation is suggested to control spark discharge for analytical use, having a unique feature that firing points of the spark discharge can be fixed by laser irradiation. Because the spark discharge easily initiates at particular surface sites, such as non-metallic inclusions, called selective discharge, the concentration of some elements sometimes deviates from their average one in spark discharge optical emission spectrometry. Therefore, stabilization of firing points on a sample surface could improve the analytical precision. 相似文献
40.
Ohe K Fujita M Matsumoto H Tai Y Miki K 《Journal of the American Chemical Society》2006,128(29):9270-9271
The ruthenium-catalyzed isomerization of diynes and triynes involving propargyl carboxylate moieties affords dienynes and dienediynes, respectively. The [1,n]-metallotropic shift (n = 3, 5) (carbene walk) of in situ generated alkynyl carbene complexes has been proposed for the catalytic isomerization reaction. 相似文献