全文获取类型
收费全文 | 762篇 |
免费 | 10篇 |
专业分类
化学 | 482篇 |
晶体学 | 7篇 |
力学 | 48篇 |
数学 | 34篇 |
物理学 | 201篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 35篇 |
2012年 | 36篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 26篇 |
2008年 | 39篇 |
2007年 | 44篇 |
2006年 | 53篇 |
2005年 | 37篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 27篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1972年 | 4篇 |
1969年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有772条查询结果,搜索用时 15 毫秒
91.
Fukuma H Nakashima K Ozaki Y Noda I 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(3-4):517-522
Generalized two-dimensional (2D) fluorescence correlation spectroscopy has been used to resolve the fluorescence spectra of two tryptophan (Trp) residues in alcohol dehydrogenase and lysozyme. In each protein, one Trp residue is buried in a hydrophobic domain of the protein matrix and the other Trp residue is located at a hydrophilic domain close to the protein-water interface. Fluorescence quenching by iodide ion, a hydrophilic quencher, was employed as a perturbation to induce the intensity change in the spectra. The Trp residue which is located at the hydrophilic domain is effectively quenched by the quencher, while the Trp residue located at the hydrophobic domain is protected from the quenching. Therefore, the fluorescence of these two Trp residues have a different sensitivity to the quenching, showing a different response to the concentration of the quencher. Fluorescence spectra of the two Trp residues in alcohol dehydrogenase, which are heavily overlapped in conventional one-dimensional spectra, have been successfully resolved by the 2D correlation technique. From the asynchronous correlation map, it was revealed that the quenching of Trp located at the hydrophobic part was brought about after that of Trp located at the hydrophilic part. In contrast, the fluorescence spectra of the two Trp residues could not be resolved after the alcohol dehydrogenase was denatured with guanidine hydrochloride. These results are consistent with the well-known structure of alcohol dehydrogenase. Furthermore, it was elucidated that the present 2D analysis is not interfered by Raman bands of the solvent, which sometimes bring difficulty into the conventional fluorescence analysis. Fluorescence spectra of the Trp residues in lysozyme could not be resolved by the 2D correlation technique. The differences between the two proteins are attributed to the fact that the Trp residue in the hydrophobic site of lysozyme is not sufficiently protected from the quenching. 相似文献
92.
Li YM Sun SQ Zhou Q Tao JX Noda I 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(3):565-573
Using FT-IR and 2D-IR correlation spectroscopy, the intensity changes and their sequence of amide I and II bands of four traditional Chinese animal drugs (Cornu Cervi Pantotrichum, Cornu Saigae Tataricae, Scorpio and Hirud) under thermal perturbation are studied, and component of Ca(3)(PO(4))(2) in the drug of Cornu Cervi Pantotrichum and sulfates components in the drug of scorpion are identified. The drug of Cornu Cervi Pantotrichum contains inorganic salt Ca(3)(PO(4))(2) and the drug of Scorpio contains sulfates. It is assigned that the bands of 604 and 561 cm(-1) belong to the component of Ca(3)(PO(4))(2), and the bands of 637 and 615 cm(-1) belong to sulfates. Organic components of these drugs respond to the thermal perturbation far stronger than that of the inorganic components. The intensities of amide I and II bands in the drugs, except for amide II band in drug Scorpio, change strongly. For the drugs of Cornu Cervi Pantotrichum, Cornu Saigae Tataricae and Hirudo, the intensity changes of amide II band occurs prior to that of amide I band. The C-N bond in the product operator(3)(4) conjugative system converts from double bond to single bond, but the C=O bond remains double bond during the heating process. On the other hand, amide II vibrations, which may involve much more of the hydrogen bonded local structures of amide groups in the system compared to the C=O dominated amide I vibration, may undergo thermally induced changes at a temperature much lower than the other mode. The traditional Chinese animal drugs can be identified rapidly and non-separately by using FT-IR and 2D-IR correlation spectroscopy. 相似文献
93.
A Si-based light emitter has long been the final key component for electronic and photonic integrated circuits on Si, because Si has an indirect band gap. Atomistic and electronic structures and energy gains of formation of possible nitrogen (N) and fluorine (F) complexes in Si have been researched from first-principles, in order to engineer the band structure of Si for light emission. The calculated results show that the substitutional nitrogen NS and bond center fluorine FBC pair complex has large stabilization energy, and that the pair-complex-doped Si has direct band gap, which is reduced with respect to that of Si. These results lead to the possibilities of doping-based engineering of Si optical properties with introduction of deep-level impurity and charge compensation. 相似文献
94.
Fumihiko Maekawa Okiru Komine Katsushige Sato Tomoyuki Kanamatsu Motoaki Uchimura Kohichi Tanaka Hiroko Ohki-Hamazaki 《BMC neuroscience》2006,7(1):1-13
Background
Results of the Women's Health Initiative Memory Study (WHIMS) raised concerns regarding the timing and formulation of hormone interventions. Conjugated equine estrogens (CEE), used as the estrogen therapy in the WHIMS trial, is a complex formulation containing multiple estrogens, including several not secreted by human ovaries, as well as other biologically active steroids. Although the full spectrum of estrogenic components present in CEE has not yet been resolved, 10 estrogens have been identified. In the present study, we sought to determine which estrogenic components, at concentrations commensurate with their plasma levels achieved following a single oral dose of 0.625 mg CEE (the dose used in the WHIMS trial) in women, are neuroprotective and whether combinations of those neuroprotective estrogens provide added benefit. Further, we sought, through computer-aided modeling analyses, to investigate the potential correlation of the molecular mechanisms that conferred estrogen neuroprotection with estrogen interactions with the estrogen receptor (ER).Results
Cultured basal forebrain neurons were exposed to either β-amyloid25–35 or excitotoxic glutamate with or without pretreatment with estrogens followed by neuroprotection analyses. Three indicators of neuroprotection that rely on different aspects of neuronal damage and viability, LDH release, intracellular ATP level and MTT formazan formation, were used to assess neuroprotective efficacy. Results of these analyses indicate that the estrogens, 17α-estradiol, 17β-estradiol, equilin, 17α-dihydroequilin, equilinen, 17α-dihydroequilenin, 17β-dihydroequilenin, and Δ8,9-dehydroestrone were each significantly neuroprotective in reducing neuronal plasma membrane damage induced by glutamate excitotoxicity. Of these estrogens, 17β-estradiol and Δ8,9-dehydroestrone were effective in protecting neurons against β-amyloid25–35-induced intracellular ATP decline. Coadministration of two out of three neuroprotective estrogens, 17β-estradiol, equilin and Δ8,9-dehydroestrone, exerted greater neuroprotective efficacy than individual estrogens. Computer-aided analyses to determine structure/function relationships between the estrogenic structures and their neuroprotective activity revealed that the predicted intermolecular interactions of estrogen analogues with ER correlate to their overall neuroprotective efficacy.Conclusion
The present study provides the first documentation of the neuroprotective profile of individual estrogens contained within the complex formulation of CEE at concentrations commensurate with their plasma levels achieved after an oral administration of 0.625 mg CEE in women. Our analyses demonstrate that select estrogens within the complex formulation of CEE contribute to its neuroprotective efficacy. Moreover, our data predict that the magnitude of neuroprotection induced by individual estrogens at relatively low concentrations may be clinically undetectable and ineffective, whereas, a combination of select neuroprotective estrogens could provide an increased and clinically meaningful efficacy. More importantly, these data suggest a strategy for determining neurological efficacy and rational design and development of a composition of estrogen therapy to alleviate climacteric symptoms, promote neurological health, and prevent age-related neurodegeneration, such as AD, in postmenopausal women. 相似文献95.
Fumihiko Maekawa Okiru Komine Katsushige Sato Tomoyuki Kanamatsu Motoaki Uchimura Kohichi Tanaka Hiroko Ohki-Hamazaki 《BMC neuroscience》2006,7(1):75
Background
Imprinting behavior is one form of learning and memory in precocial birds. With the aim of elucidating of the neural basis for visual imprinting, we focused on visual information processing. 相似文献96.
Debasish Ghosh Pradip Ghosh Golap Kalita Takuto Noda Chisato Takahashi Masaki Tanemura 《固体物理学:研究快报》2013,7(7):489-492
An efficient cathode material with high transparency (93%) based on conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and single wall carbon nanotubes (SWCNTs) has been developed for the fabrication of highly transparent and flexible field electron emitters (FEE). This kind of material showed superior field emission (FE) performance with very high current density (10–3A/cm2) at very low electric field. The FE performance of the hybrid materials was dramatically improved compared to either SWCNTs and PEDOT:PSS. Thus the hybrid structures of conducting polymer and SWCNTs might be a good choice for use as a cathode material to enhance the FE performance and for potential application in future portable displays. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
L. Shao D. Shao C. G. Shao H. Noda 《International Journal of Theoretical Physics》2008,47(6):1663-1691
Using the recoupling theorem and graph calculation in loop quantum gravity, it is demonstrated that the action of metric matrix
operator on Gaussian weave state is an eigenaction, the representation matrix elements of the metric operator and their expectation
values are calculated. The values of length of tangent vectors of edges adjacent to the vertex of Gaussian weave state, as
well as the angles between them are also obtained in the cases of k=0 and k=2. 相似文献
98.
Direct Estimation of the Surface Location of Immobilized Functional Groups for Concerted Catalysis Using a Probe Molecule
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hiroto Noda Dr. Ken Motokura Prof. Dr. Yusuke Wakabayashi Kaori Sasaki Dr. Hiroo Tajiri Dr. Akimitsu Miyaji Dr. Sho Yamaguchi Prof. Dr. Toshihide Baba 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5113-5117
The location of active sites during concerted catalysis by a metal complex and tertiary amine on a SiO2 surface is discussed based on the interaction between the functionalized SiO2 surface and a probe molecule, p‐formyl phenylboronic acid. The interactions of the probe molecule with the surface functionalities, diamine ligand, and tertiary amine, were analyzed by FT‐IR and solid‐state 13C and 11B MAS NMR. For the catalyst exhibiting high 1,4‐addition activity, the diamine ligand and tertiary amine base exist in closer proximity than in the catalyst with low activity. 相似文献
99.
Scott SL Peoples BC Yung C Rojas RS Khanna V Sano H Suzuki T Shimizu F 《Chemical communications (Cambridge, England)》2008,(35):4186-4188
In situ polymerization by certain transition metal catalysts supported on and activated by acid-treated montmorillonite produces well-dispersed clay-polyolefin nanocomposites, without requiring either organic surfactants to be present in the clay phase or modification of the polyolefin structure. 相似文献
100.
Choi HC Lee S Lee KK Noda I Park C Kwon CH Jung YM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(4):1110-1113
A promising possibility for the quantitative analysis of X-ray absorption near edge structure (XANES) spectra of nanosized electrode materials is demonstrated. We used a 2D map representation technique, which utilizes the values of the first derivatives of the absorbance with respect to the inserted Li(+) content plotted over the two-dimensional space defined by the inserted Li(+) content (mole) versus photon energy (eV) as a single map. The technique was applied to XANES spectra of the Li(y)CoO system in the first Li(+) insertion reaction for determining the structural and electronic variations associated with the change in Li(+) content. The obtained show that the intensities of two peaks at 7725 and 7711 eV increased with the Li(+) content and the difference of intensity change of these two peaks carried out for successive couples of spectra yielded the largest changes at 1.05 and 1.98 mol of Li content. This approach for quantitative analysis of XANES without using conventional simulation techniques enable us to interpret X-ray absorption spectroscopy (XAS) as a quantitative analytical technique with greater confidence. 相似文献