全文获取类型
收费全文 | 5261篇 |
免费 | 137篇 |
国内免费 | 20篇 |
专业分类
化学 | 3634篇 |
晶体学 | 68篇 |
力学 | 73篇 |
数学 | 228篇 |
物理学 | 1415篇 |
出版年
2021年 | 30篇 |
2020年 | 54篇 |
2019年 | 61篇 |
2018年 | 50篇 |
2017年 | 34篇 |
2016年 | 82篇 |
2015年 | 86篇 |
2014年 | 113篇 |
2013年 | 251篇 |
2012年 | 244篇 |
2011年 | 260篇 |
2010年 | 150篇 |
2009年 | 156篇 |
2008年 | 279篇 |
2007年 | 234篇 |
2006年 | 256篇 |
2005年 | 244篇 |
2004年 | 241篇 |
2003年 | 188篇 |
2002年 | 196篇 |
2001年 | 148篇 |
2000年 | 159篇 |
1999年 | 85篇 |
1998年 | 61篇 |
1997年 | 63篇 |
1996年 | 54篇 |
1995年 | 42篇 |
1994年 | 64篇 |
1993年 | 89篇 |
1992年 | 92篇 |
1991年 | 70篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 70篇 |
1987年 | 68篇 |
1986年 | 74篇 |
1985年 | 101篇 |
1984年 | 91篇 |
1983年 | 38篇 |
1982年 | 66篇 |
1981年 | 73篇 |
1980年 | 67篇 |
1979年 | 60篇 |
1978年 | 52篇 |
1977年 | 64篇 |
1976年 | 52篇 |
1975年 | 39篇 |
1974年 | 49篇 |
1973年 | 30篇 |
1967年 | 23篇 |
排序方式: 共有5418条查询结果,搜索用时 859 毫秒
991.
The primary goal of KamLAND is a search for the oscillation of \({\bar{\nu }}_\mathrm{e}\) ’s emitted from distant power reactors. The long baseline, typically 180 km, enables KamLAND to address the oscillation solution of the “solar neutrino problem” with \({\bar{\nu }}_{e} \) ’s under laboratory conditions. KamLAND found fewer reactor \({\bar{\nu }}_{e} \) events than expected from standard assumptions about \(\overline{\nu }_e\) propagation at more than 9 \(\sigma \) confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at more than 5 \(\sigma \) C.L., and prefers the distortion from neutrino oscillation effects. A three-flavor oscillation analysis of the data from KamLAND and KamLAND + solar neutrino experiments with CPT invariance, yields \(\Delta m_{21}^2 \) = [ \(7.54_{-0.18}^{+0.19} \times \) 10 \(^{-5}\) eV \(^{2}\) , \(7.53_{-0.18}^{+0.19} \times \) 10 \(^{-5}\) eV \(^{2}\) ], tan \(^{2}\theta _{12}\) = [ \(0.481_{-0.080}^{+0.092} \) , \(0.437_{-0.026}^{+0.029} \) ], and sin \(^{2}\theta _{13}\) = [ \(0.010_{-0.034}^{+0.033} \) , \(0.023_{-0.015}^{+0.015} \) ]. All solutions to the solar neutrino problem except for the large mixing angle region are excluded. KamLAND also demonstrated almost two cycles of the periodic feature expected from neutrino oscillation effects. KamLAND performed the first experimental study of antineutrinos from the Earth’s interior so-called geoneutrinos (geo \({\bar{\nu }}_{e} \) ’s), and succeeded in detecting geo \({\bar{\nu }}_{e} \) ’s produced by the decays of \(^{238}\) U and \(^{232}\) Th within the Earth. Assuming a chondritic Th/U mass ratio, we obtain \(116_{-27}^{+28} {\bar{\nu }}_{e}\) events from \(^{238}\) U and \(^{232}\) Th, corresponding a geo \({\bar{\nu }}_{e}\) flux of \(3.4_{-0.8}^{+0.8}\times \) 10 \(^{6}\) cm \(^{-2}\) s \(^{-1}\) at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo \({\bar{\nu }}_{e} \) rate. 相似文献
992.
Kenji Yoshii Yasuhiro Yoneda Ignace Jarrige Tatsuo Fukuda Yasuo Nishihata Chikashi Suzuki Yoshiaki Ito Takahito Terashima Shinzo Yoshikado Sei Fukushima 《Journal of Physics and Chemistry of Solids》2014
We have studied the electronic properties of the ferroelectric barium titanate BaTiO3 using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L3 and Ti-K absorption edges. Contrary to a previous study, we found no fine structure in the pre-edge area of the PFY-XAS spectrum at the Ba-L3 edge, and no temperature-induced spectral change was observed between room temperature and 150 °C. This result is not supportive of the possible presence of the displacement around Ba2+ at the Curie temperature. RXES spectra were measured at the Ti-K edge for BaTiO3, along with SrTiO3 and La-doped metallic SrTiO3. The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3d states to have a delocalized character, in contrast with the Ba 5d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO3. 相似文献
993.
Y. Maeda T. Saito H. Miyasako T. Uesaka S. Ota S. Kawase T. Kikuchi H. Tokieda T. Kawabata K. Yako T. Wakasa S. Sakaguchi R. Chen H. Sakaguchi T. Shima T. Suzuki A. Tamii 《Few-Body Systems》2014,55(8-10):729-732
The effects of three nucleon force (3NF) have been actively studied via the nucleon–deuteron (Nd) scattering states. The differential cross sections and the vector analyzing powers A y of the 2H(p, n) inclusive breakup reaction at 170 MeV were measured for the study of 3NF effects in the intermediate energy region. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were measured by using TOF method. The data were compared with the Faddeev calculations based on modern nucleon–nucleon (NN) forces with and without the 3NF. Concerning the differential cross sections, we can see large discrepancies between the data and the calculations in the region of scattered neutron energies are low, which is similar to the results of the 2H(p, p) inclusive breakup reaction at 250 MeV. 相似文献
994.
Chueng-Ryong Ji Bernard L. G. Bakker Ziyue Li Alfredo T. Suzuki 《Few-Body Systems》2014,55(5-7):425-434
Among the three forms of relativistic Hamiltonian dynamics proposed by Dirac in 1949, the front form has the largest number of kinematic generators. This distinction provides useful consequences in the analysis of physical observables in hadron physics. Using the method of interpolation between the instant form and the front form, we introduce the interpolating scattering amplitude that links the corresponding time-ordered amplitudes between the two forms of dynamics and provide the physical meaning of the kinematic transformations as they allow the invariance of each individual time-ordered amplitude for an arbitrary interpolation angle. We discuss the rationale for using front form dynamics, nowadays known as light-front dynamics (LFD), and present a few explicit examples of hadron phenomenology that LFD uniquely can offer from first-principles quantum chromodynamics. In particular, model-independent constraints are provided for the analyses of deuteron form factors and the N Δ transition form factors at large momentum transfer squared Q 2. The swap of helicity amplitudes between the collinear and non-collinear kinematics is also discussed in deeply virtual Compton scattering. 相似文献
995.
Weiqing Gao Zhongchao Duan Koji Asano Tonglei Cheng Dinghuan Deng Morio Matsumoto Takashi Misumi Takenobu Suzuki Yasutake Ohishi 《Applied physics. B, Lasers and optics》2014,116(4):847-853
We demonstrate the supercontinuum (SC) generation in a four-hole As2S5 chalcogenide microstructured optical fiber (MOF) experimentally. The As2S5 glass has better property of transmission than As2S3 glass in the visible range. The four-hole As2S5 MOF is fabricated by a rod-in-tube method. The SCs generated by different pump wavelengths at 2,000, 2,300 and 2,500 nm in the MOF whose length is from 2.3 to 20 cm are demonstrated. Those pump wavelengths correspond to the chromatic dispersion wavelength in the normal chromatic dispersion region, the anomalous chromatic dispersion region close to zero-dispersion wavelength (ZDW) and the anomalous chromatic dispersion region far from ZDW, respectively. Wider SCs can be obtained when pumped at a wavelength in the anomalous dispersion region close to ZDW. The widest SC range of 4,280 nm (from 1,370 to 5,650 nm) covering two octaves was obtained in a 4.8-cm-long fiber pumped at 2,300 nm. 相似文献
996.
Kanesaka I Hiura T Suzuki S Shimizu K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(8):1621-1626
The infrared spectra of 1-monopalmitin- or 1-monostearin-water systems in the gel phase were observed at room temperature. In both systems the infrared intensities of the bands parallel and perpendicular to the paraffin chain are relatively reduced and enhanced, respectively, on going from the crystalline phase to the gel phase. These spectral changes are explained in terms of the interaction among oscillating dipoles, which is sensitive to the morphology change from the three-dimensional crystalline phase to the two-dimensional lipid bilayers. The non-planar lipid bilayers are proposed for the gel phase in monopalmitin-water systems with x > or = 35 (x: wt.% water). 相似文献
997.
Keiko Nakanishi Munehiro Katagi Kei Zaitsu Noriaki Shima Hiroe Kamata Akihiro Miki Hajime Kato Ken-Ichi Harada Hitoshi Tsuchihashi Koichi Suzuki 《Analytical and bioanalytical chemistry》2012,404(8):2427-2435
A liquid chromatography–electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) procedure was developed for the simultaneous determination of enantiomers of the prevalent designer drug 3,4-methylenedioxymethamphetamine (MDMA) and its phase I and phase II metabolites in urine with chiral derivatization. The analytes in urine were directly derivatized with chiral Marfey’s reagent, N α- (5-fluoro-2,4-dinitrophenyl)-d-leucinamide, without extraction. The diastereomers of the N α-(2,4-dinitrophenyl)-d-leucinamide derivatives generated were determined by LC-MS/MS. Satisfactory chromatographic separation was achieved for the enantiomers of MDMA and its metabolites 3,4-methylenedioxyamphetamine, 4-hydroxy-3-methoxymethamphetamine (HMMA), HMMA glucuronide, and HMMA sulfate on a semimicro octadecylsilane column using linear gradient elution. With use of multiple reaction monitoring mode, the limits of detection of these analytes ranged from 0.01 to 0.03?μg/mL. Linear calibration curves were obtained for all enantiomers from 0.1 to 20?μg/mL in urine. The method showed sufficient reproducibility and quantitative ability. This is the first report of a simple LC-MS/MS-based analytical procedure with direct chiral derivatization in aqueous media that allows simultaneous enantiomeric determination of drugs and their metabolites, including glucuronide and sulfate derivatives. 相似文献
998.
Prof. Dr. Shin Aoki Satoshi Suzuki Dr. Masanori Kitamura Prof. Dr. Takeharu Haino Motoo Shiro Dr. Mohd Zulkefeli Prof. Dr. Eiichi Kimura 《化学:亚洲杂志》2012,7(5):944-956
We have previously reported that the trimeric Zn2+–cyclen complex (tris(Zn2+–cyclen), [Zn3L1]6+) and the trianion of trithiocyanuric acid (TCA3−) assembled in a 4:4 ratio to form a cuboctahedral supramolecular cage, [(Zn3L1)4(TCA3−)4]12+ (hereafter referred to as a Zn–cage), in neutral aqueous solution (cyclen=1,4,7,10-tetraazacyclododecane). Herein, we examined the molecular recognition of C1–C12 hydrocarbons (CnH(2n+2) (n≈1–12)), cyclopentane, cyclododecane, cis-decalin, and trans-decalin by the Zn–cage under normal atmospheric pressure. This cage complex was also able to encapsulate guest molecules that had larger volumes than that of the inner cavity of the Zn–cage, thereby suggesting that the inner shape of the Zn–cage was flexible. Computational simulations of Zn–cage–guest complexes provided support for this conclusion. Moreover, the solvent-accessible surface areas (SASA) of the Zn–cage host, guest molecules, and the Zn–cage-guest complexes were calculated and the data were used to explain the order of stability determined by the guest-replacement experiments. The storage of volatile molecules in aqueous solution by the Zn–cage is also discussed. 相似文献
999.