全文获取类型
收费全文 | 1084篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
化学 | 881篇 |
晶体学 | 4篇 |
力学 | 21篇 |
数学 | 49篇 |
物理学 | 190篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 25篇 |
2014年 | 37篇 |
2013年 | 56篇 |
2012年 | 78篇 |
2011年 | 80篇 |
2010年 | 42篇 |
2009年 | 36篇 |
2008年 | 72篇 |
2007年 | 75篇 |
2006年 | 53篇 |
2005年 | 51篇 |
2004年 | 35篇 |
2003年 | 39篇 |
2002年 | 33篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有1145条查询结果,搜索用时 31 毫秒
31.
32.
Y. Kameo A. Katayama A. Fujiwara T. Haraga M. Nakashima 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):71-78
A rapid determination method in which beta-ray spectrometry was combined with solid phase extraction using Sr Rad Disk was
developed for the determination of 89Sr and 90Sr in low-level radioactive waste. Various amounts of 89Sr, 90Sr, and 90Y retained by the Sr Rad Disk was measured by a beta-ray spectrometer, and it was found that both 89Sr and 90Sr were simultaneously determined with <30% error (2σ) at 89Sr/90Sr radioactivity ratio of 0.3 to 45. The present method was successfully applied to actual radioactive liquid waste samples
arising from nuclear facilities in Japan Atomic Energy Agency. Strontium was simply separated from interfering nuclides such
as 137Cs and 154Eu, and matrix components by the Sr Rad Disk, and the results obtained by beta-ray spectrometry was in good agreement with
that of the conventional analysis. 相似文献
33.
A novel capillary electrophoretic (CE) method was developed for the determination of Ga(III). The so-called Anderson-type [GaMo6O24H6]3- complex was readily formed by the reaction of Mo(VI) with Ga(III) in 0.050 M monochloroacetate buffer (pH 2.0) and the precolumn complex-formation reaction was applied to the CE determination of Ga(III) with direct UV detection at 240 nm. The peak area was linearly dependent on the concentration of Ga(III) in the range of 5.0 x 10(-7)-5.0 x 10(-5) M. Owing to the high molar absorptivity of the Anderson anion, a detection limit of 2.0 x 10(-7) M (signal-to-noise ratio=3) was achieved. The advantage of the present method is that the presence of large excesses of Al(III) and In(III) does not cause interference. 相似文献
34.
Sun Y Irie M Kishikawa N Wada M Kuroda N Nakashima K 《Biomedical chromatography : BMC》2004,18(8):501-507
A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two-step liquid-liquid extraction, BPA was derivatized with fluorescent labeling reagent, 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl). The excess fluorescent reagent could be removed effectively using a column-switching system. The separation of DIB-BPA from endogenous materials in milk was carried out on two C(18) columns and fluorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2-5.0 ng mL(-1) in breast milk, and the detection limit was 0.11 ng mL(-1) at a signal-to-noise ratio of 3. Intra- and inter-day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty-three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 +/- 0.20 ng mL(-1), with no correlation to the lipid content of milk samples. 相似文献
35.
Poly(ethylene oxide)-b-polymethacrylate (PEO-b-PMA), one of the double-hydrophilic block copolymers, has proved to the form nanoaggregates with poly-L-lysine (PLS). This was confirmed by turbidimetry, zeta-potential measurements, and dynamic light scattering. The nanoaggregate formation is induced by electrostatic charge neutralization of the PMA block with PLS. The properties of the aggregates are affected by PLS concentration as well PEO-b-PMA concentration. The aggregates have potential applications in biomedical science. 相似文献
36.
The butyl urea of guanosine (UG) presents an ADDA hydrogen-bonding array that is complementary to the DAAD array of 2,7-diamido-1,8-naphthyridine (DAN). The stability of the DAN.UG complex was measured by fluorimetry using the fluorescence resonance energy transfer (FRET) from the naphthyridine ring to a coumarin 343 moiety linked covalently to the UG unit. The quadruply hydrogen-bonded complex is extremely stable with a measured association constant, Kassoc, of 3 x 108 M-1. Unlike related hydrogen-bonding modules, the guanosine urea, UG, contains a relatively fixed tautomeric form and only weakly self-associates (Kdimer = ca. 200 M-1). The DAN unit was linked to a styrene-based monomer and copolymerized with styrene to form a polymer (PS-DAN) containing a controlled number of the DAAD recognition units. Likewise, a methacrylate monomer containing the UG unit was copolymerized with butyl methacrylate to form a polymer (PBMA-UG). Blends formed from PS-DAN and PBMA-UG were characterized by DSC, SEC, and viscometry. The importance of selective heterocomplexation and weak self-association in forming the blended networks was demonstrated by using a ureidopyrimidinone (UPy) unit, which also forms strong heterocomplexes with DAN but is able to strongly self-associate. 相似文献
37.
Y. Goto K. Nakashima K. Mitsuishi M. Takafuji S. Sakaki H. Ihara 《Chromatographia》2002,56(1-2):19-23
Summary Poly(octadecyl acrylate) exists in a crystalline state at room temperature. This crystalline state was formed even after being
grafted onto silica through the terminal group of the polymer. When this polymer-grafted silica (Sil-ODAn) was used as a reversed phase liquid chromatography packing material, better selectivity for diastereomerized phenylethylamines
derivatized by (S)-(−)-(2,3-naphthalenedicarboximidyl)propionyl fluoride was observed at room temperature than was observed
for simple octadecylated silica (ODS). On the other hand, increasing temperature reduced the selectivity to be close to that
of ODS. Additional experiments showed the better selectivity derived from Sil-ODAn was due to both the highly-oriented structure of the polymer and the carbonyl-π interaction with the diastereomer. A theoretical
investigation of this carbonyl-π interaction is also described briefly. 相似文献
38.
Shinya Nakashima Dr. Hiromune Ando Risa Saito Hideki Tamai Dr. Hideharu Ishida Dr. Makoto Kiso 《化学:亚洲杂志》2012,7(5):1041-1051
The first total synthesis of the hybrid ganglioside X2, which consisted of a highly branched octasaccharide and ceramide moieties, was accomplished by using a glucosyl ceramide cassette approach. With a disaccharyl donor, the heptasaccharide could not be constructed by glycosylation of the C4 hydroxy group of galactose at the reducing end of the pentasaccharide. In contrast, through an alternative approach with two branched glycan units, a GM2-core trisaccharide, and a lacto-ganglio tetrasaccharide, the heptasaccharyl donor could be prepared and subsequently joined with a glucosyl ceramide cassette to afford the protected ganglioside, X2. Finally, global deprotection completed the synthesis, thus affording the pure ganglioside X2. 相似文献
39.
Dr. Tsubasa Nakashima Haruka Fujimori Dr. Kohsuke Ohmatsu Prof. Takashi Ooi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9253-9256
Intermediary radical cations, generated through single-electron oxidation of enol silyl ethers by excited Ir-based photocatalysts, can be exploited as Brønsted acids for the activation of heteroarylcyanides. This strategy enables the direct allylic C−H heteroarylation of enol silyl ethers under visible-light irradiation. 相似文献
40.
Hideki Misaka Eisuke Tamura Kosuke Makiguchi Kensuke Kamoshida Ryosuke Sakai Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(10):1941-1952
For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ5,4Λ5‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4), was confirmed. Among these superbases, only t‐Bu‐P4 showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P4‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P4 system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P4‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献