全文获取类型
收费全文 | 211篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 164篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 4篇 |
物理学 | 47篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 11篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有217条查询结果,搜索用时 46 毫秒
71.
Bis(triphenylphosphine)palladium(II) dichloride (PdCl2(PPh3)2) catalyzes regioselective addition of benzeneselenol to terminal alkynes and the subsequent double-bond isomerization to afford the corresponding internal alkenyl selenides in good yields. 相似文献
72.
Shibata M Hashi S Nakanishi H Masuda S Katsura T Yano I 《Biomedical chromatography : BMC》2012,26(12):1519-1528
The purpose of this study was to develop an ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method of 22 antiepileptics for routine therapeutic monitoring. The antiepileptics used in the analyses were carbamazepine, carbamazepine‐10,11‐epoxide, clobazam, N‐desmethylclobazam, clonazepam, diazepam, N‐desmethyldiazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, N‐desmethylmesuximide, nitrazepam, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide. After protein precipitation of 50 μL plasma with methanol, the supernatant was diluted with water or was evaporated to dryness and reconstituted with mobile phase in the case of benzodiazepines. Separation was achieved on an Acquity UPLC BEH C18 column with a gradient mobile phase of 10 mm ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.4 mL/min. An Acquity TQD instrument in multiple reaction monitoring mode with ion mode switching was used for detection. All antiepileptics were detected and quantified within 10 min, with no endogenous interference. All the calibration curves showed good linearity in the therapeutic range (r2 < 0.99). The precision and accuracy values for intra‐ and inter‐assays were within ±15% except for phenobarbital and tiagabine. A good correlation was observed between the concentration of clinical samples measured by the new method described here and the conventional methods. The values of carbamazepine and phenytoin by UPLC‐MS/MS were lower than those detected by the immunoassays, which might be caused by the cross‐reaction of antibodies with their metabolites. In conclusion, we developed a simple and selective UPLC‐MS/MS method suitable for routine therapeutic monitoring of antiepileptics. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
73.
Epitaxial La1−xSrxMnO3 (LSMO) films were prepared by excimer laser-assisted metal organic deposition (ELAMOD) at a low temperature using ArF, KrF, and XeCl excimer lasers. Cross-section transmission electron microscopy (XTEM) observations confirmed the epitaxial growth and homogeneity of the LSMO film on a SrTiO3 (STO) substrate, which was prepared using ArF, KrF, and XeCl excimer lasers. It was found that uniform epitaxial films could be grown at 500 °C by laser irradiation. When an XeCl laser was used, an epitaxial film was formed on the STO substrate at a fluence range from 80 to 140 mJ/cm2 of the laser fluence for the epitaxial growth of LSMO film on STO substrate was changed. When the LaAlO3 (LAO) substrate was used, an epitaxial film was only obtained by ArF laser irradiation, and no epitaxial film was obtained using the KrF and XeCl lasers. When the back of the amorphous LSMO film on an LAO substrate was irradiated using a KrF laser, no epitaxial film formed. Based on the effect of the wavelength and substrate material on the epitaxial growth, formation of the epitaxial film would be found to be photo thermal reaction and photochemical reaction. The maximum temperature coefficient of resistance (TCR) of the epitaxial La0.8Sr0.2MnO3 film on an STO substrate grown using an XeCl laser is 4.0%/K at 275 K. XeCl lasers that deliver stabilized pulse energies can be used to prepare LSMO films with good a TCR. 相似文献
74.
Koichi Narita Takuya Kikuchi Kazuhiro Watanabe Dr. Toshiya Takizawa Dr. Takamasa Oguchi Dr. Kyosuke Kudo Keisuke Matsuhara Hideki Abe Dr. Takao Yamori Prof. Dr. Minoru Yoshida Prof. Dr. Tadashi Katoh Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(42):11174-11186
The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins A and B, 5′′‐epi‐spiruchostatin B and FK228 were efficiently synthesized in a convergent and unified manner. The synthetic method involved the following crucial steps: i) a Julia–Kocienski olefination of a 1,3‐propanediol‐derived sulfone and a L ‐ or D ‐malic acid‐derived aldehyde to access the most synthetically challenging unit, (3S or 3R,4E)‐3‐hydroxy‐7‐mercaptohept‐4‐enoic acid, present in a D ‐alanine‐ or D ‐valine‐containing segment; ii) a condensation of a D ‐valine‐D ‐cysteine‐ or D ‐allo‐isoleucine‐D ‐cysteine‐containing segment with a D ‐alanine‐ or D ‐valine‐containing segment to directly assemble the corresponding seco‐acids; and iii) a macrocyclization of a seco‐acid using the Shiina method or the Mitsunobu method to construct the requisite 15‐ or 16‐membered macrolactone. The present synthesis has established the C5′′ stereochemistry of spiruchostatin B. In addition, HDAC inhibitory assay and the cell‐growth inhibition analysis of the synthesized depsipeptides determined the order of their potency and revealed some novel aspects of structure–activity relationships. It was also found that unnatural 5′′‐epi‐spiruchostatin B shows extremely high selectivity (ca. 1600‐fold) for class I HDAC1 (IC50=2.4 nM ) over class II HDAC6 (IC50=3900 nM ) with potent cell‐growth‐inhibitory activity at nanomolar levels of IC50 values. 相似文献
75.
Tomohiko Nakajima Tetsuo Tsuchiya Toshiya Kumagai 《Applied Physics A: Materials Science & Processing》2008,93(1):51-55
Ca0.997Pr0.002TiO3 (CPTO) thin films that show strong red luminescence were successfully prepared by means of an excimer laser assisted metal
organic deposition (ELAMOD) process with a KrF laser at a fluence of 100 mJ/cm2, a pulse duration of 26 ns, and a repetition rate of 20 Hz at 100°C in air. The CPTO films grew on the silica, borosilicate,
and indium-tin-oxide (ITO) glasses. The crystallinity of the CPTO films depended on the substrates; the films were well grown
on the borosilicate and ITO glasses compared to the silica glass. To elucidate the key factors for the crystallization of
the CPTO films in this process, we carried out numerical simulations for the temperature variation at the laser irradiation,
using a heat diffusion equation, and compared the experimental data with thermal simulations. According to the results, we
have shown that a large optical absorbance of the film and a small thermal conductivity of the substrate provide effective
annealing time and temperature for the crystallization of the CPTO films, and polycrystalline intermediate layer which has
a large optical absorption such as the ITO also plays a key role for the nucleation of the CPTO crystals in the ELAMOD process. 相似文献
76.
Toshiya Morisue 《国际流体数值方法杂志》1990,11(6):881-891
There are two methods of using the magnetic vector potential for three-dimensional eddy current calculations. The first method uses the continuous magnetic vector potential which accompanies a scalar potential and has the advantage that no cutting is necessary for the multiply connected region problem. The second method uses the discontinuous magnetic vector potential which accompanies no scalar potential and has the disadvantage that cutting is necessary for the multiply connected region problem. In this paper a formulation using the continuous magnetic vector potential and accompanying scalar potential is given, together with computed results for three three-dimensional multiply connected eddy current problems. 相似文献
77.
Catenate network formation by end-linking reactions of linear chains with bifunctional regents is studied theoretically and by computer simulations. It is found that the reaction cannot reach its stationary limit, and catenate networks are never formed by this method. An alternative method that will lead to catenate networks nearly in the topological equilibrium state is proposed. It is pointed out that catenate networks are an ideal system for studying the role of entanglement in rubber elasticity. © 1993 John Wiley & Sons, Inc. 相似文献
78.
79.
Mitsuaki Kodama Toshiya Takahashi Toshio Kurihara Shô Itô 《Tetrahedron letters》1980,21(29):2811-2812
3azzanene, the stereoisomer of trichodiene, isolated from a liverwort was synthesized with complete stereoselectivity in 8 steps (12% yield) starting from a known bicyclo[2.2.2]octane derivative. 相似文献
80.
Takamuku T Kumai T Yoshida K Otomo T Yamaguchi T 《The journal of physical chemistry. A》2005,109(34):7667-7676
To clarify the structure of solvent clusters formed in halogenoethanol-water mixtures at the molecular level, large-angle X-ray scattering (LAXS) measurements have been made at 298 K on 2,2,2-trifluoroethanol (TFE), 2,2,2-trichloroethanol (TCE), and their aqueous mixtures in the TFE and TCE mole fraction ranges of 0.002 < or = x(TFE) < or = 0.9 and 0.5 < or = x(TCE) < or = 0.9, respectively. The radial distribution functions (RDFs) for TFE-water mixtures have shown that the structural transition from inherent TFE structure to the tetrahedral-like structure of water takes place at x(TFE) approximately 0.2. In the TCE-water mixtures inherent TCE structure remains in the range of 0.5 < or = x(TCE) < or = 1. Small-angle neutron scattering (SANS) experiments have been performed on CF(3)CH(2)OD- (TFE-d(1)-) D(2)O and CF(3)CD(2)OH- (TFE-d(2)-) H(2)O mixtures in the TFE mole fraction range of 0.05 < or = x(TFE) < or = 0.8. The SANS results in terms of the Ornstein-Zernike correlation length have revealed that TFE and water molecules are most heterogeneously mixed with each other in the TFE-water mixture at x(TFE) approximately 0.15, i.e., both TFE clusters and water clusters are most enhanced in the mixture. To evaluate the dynamics of TFE and ethanol (EtOH) molecules in TFE-water and ethanol-water mixtures, respectively, (1)H NMR relaxation rates for the methylene group within alcohol molecules have been measured by using an inversion-recovery method. The alcohol concentration dependence of the relaxation rates for the TFE-water and ethanol-water mixtures has shown a break point at x(TFE) approximately 0.15 and x(EtOH) approximately 0.2, respectively, where the structural transition from alcohol clusters to the tetrahedral-like structure of water takes place. On the basis of the present results, the most likely structure models of solvent clusters predominantly formed in TFE-water and TCE-water mixtures are proposed. In addition, effects of halogenation of the hydrophobic groups on clustering of alcohol molecules are discussed from the present results, together with the previous ones for ethanol-water and 1,1,1,3,3,3-hexafluoro-2-propanol- (HFIP-) water mixtures. 相似文献