全文获取类型
收费全文 | 2826篇 |
免费 | 65篇 |
国内免费 | 8篇 |
专业分类
化学 | 2037篇 |
晶体学 | 50篇 |
力学 | 33篇 |
数学 | 85篇 |
物理学 | 694篇 |
出版年
2022年 | 24篇 |
2021年 | 21篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 45篇 |
2015年 | 45篇 |
2014年 | 55篇 |
2013年 | 126篇 |
2012年 | 106篇 |
2011年 | 109篇 |
2010年 | 64篇 |
2009年 | 71篇 |
2008年 | 153篇 |
2007年 | 134篇 |
2006年 | 159篇 |
2005年 | 139篇 |
2004年 | 163篇 |
2003年 | 122篇 |
2002年 | 90篇 |
2001年 | 59篇 |
2000年 | 50篇 |
1999年 | 54篇 |
1998年 | 26篇 |
1997年 | 29篇 |
1996年 | 42篇 |
1995年 | 50篇 |
1994年 | 30篇 |
1993年 | 28篇 |
1992年 | 57篇 |
1991年 | 48篇 |
1990年 | 30篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 42篇 |
1984年 | 37篇 |
1983年 | 22篇 |
1982年 | 38篇 |
1981年 | 37篇 |
1980年 | 45篇 |
1979年 | 26篇 |
1978年 | 26篇 |
1977年 | 28篇 |
1976年 | 30篇 |
1975年 | 33篇 |
1974年 | 38篇 |
1973年 | 40篇 |
排序方式: 共有2899条查询结果,搜索用时 0 毫秒
991.
Charvet R Yamamoto Y Sasaki T Kim J Kato K Takata M Saeki A Seki S Aida T 《Journal of the American Chemical Society》2012,134(5):2524-2527
Amphiphilic zinc porphyrin (P(Zn); electron donor, D)-fullerene (C(60); electron acceptor, A) dyads 2 and 3, bearing an identical hydrophilic wedge with triethylene glycol chains but different linkers between the P(Zn) and C(60) units, self-assemble into nanotubes with essentially different dimensional and geometrical features from one another. The nanotube from dyad 2 with an ester linker consists of a bilayer wall formed with coaxially segregated D and A nanodomains along the tube axis (coaxial D-A heterojunction), thereby displaying explicit photoconductivity with ambipolar carrier transport properties. In contrast, the nanotube from dyad 3 with a rigid arylacetylene linker consists of a monolayer wall with an alternate geometry of D/A stacking, resulting in poor photoconducting outputs. Such a geometrical difference also significantly affects the photovoltaic properties. 相似文献
992.
We discuss a supersymmetric version of DBI (Dirac–Born–Infeld) inflation, which is a typical inflation model in string cosmology. The supersymmetric DBI action together with a superpotential always leads to correction terms associated with the potential into the kinetic term, which drastically change the dynamics of DBI inflation. We find two significant features of supersymmetric DBI inflation. The first one is that ultra-relativistic motion is prohibited to cause inflation, which leads to order of unity sound velocity squared and hence small non-Gaussianities of primordial curvature perturbations. The second one is that the relation between the tensor-to-scalar ratio and the field variation is modified. Then, significant tensor-to-scalar ratio r?0.01 is possible because the variation of the canonically normalized inflaton can be beyond the reduced Planck scale. These new features are in sharp contrast with those of the standard non-supersymmetric DBI inflation and hence have a lot of interest implications on upcoming observations of cosmic microwave background (CMB) anisotropies by the Planck satellite as well as direct detection experiments of gravitational waves like DECIGO and BBO. 相似文献
993.
In sinusoidal phase modulating laser diode (LD) interferometer, the injection current of the LD is sinusoidally modulated to realize the modulation of the wavelength. However, the light intensity of LD is also modulated, which affects the measurement accuracy. An all-fiber sinusoidal phase modulating LD interferometer for real-time displacement measurement is proposed where the influence of the intensity modulation is eliminated with a new algorithm. It is made clear that an optimal depth of the sinusoidal phase modulation (SPM) exists in the algorithm. Moreover, the SPM depth is locked at the optimal value by controlling the injection current with a feedback control system. The feasibility of the proposed interferometer for displacement measurement is verified by experiments. 相似文献
994.
Kazuharu Bamba Shin’ichi Nojiri Sergei D. Odintsov Misao Sasaki 《General Relativity and Gravitation》2012,44(5):1321-1356
We investigate de Sitter solutions in non-local gravity as well as in non-local gravity with Lagrange constraint multiplier.
We examine a condition to avoid a ghost and discuss a screening scenario for a cosmological constant in de Sitter solutions.
Furthermore, we explicitly demonstrate that three types of the finite-time future singularities can occur in non-local gravity
and explore their properties. In addition, we evaluate the effective equation of state for the universe and show that the
late-time accelerating universe may be effectively the quintessence, cosmological constant or phantom-like phases. In particular,
it is found that there is a case in which a crossing of the phantom divide from the non-phantom (quintessence) phase to the
phantom one can be realized when a finite-time future singularity occurs. Moreover, it is demonstrated that the addition of
an R
2 term can cure the finite-time future singularities in non-local gravity. It is also suggested that in the framework of non-local
gravity, adding an R
2 term leads to possible unification of the early-time inflation with the late-time cosmic acceleration. 相似文献
995.
996.
Y. Nakajima H. Hidaka T. Tamegai T. Nishizaki T. Sasaki N. Kobayashi 《Physica C: Superconductivity and its Applications》2009,469(15-20):921-923
We report the upper critical field Hc2 in a ternary iron-silicide superconductor Lu2Fe3Si5 with Tc 6 K obtained by the resistivity measurements. We find that Hc2 increases linearly with decreasing temperature down to Tc/3, and Hc2(T = 0) exceeds the orbital depairing field described by the Werthamer–Helfand–Hohenberg theory. We also find that the anisotropy of Hc2 is nearly independent of temperature and the angular dependence of Hc2 is well-described by the anisotropic Ginzburg–Landau model. These results strongly indicate the presence of two distinct superconducting gaps in Lu2Fe3Si5 although the behavior is slightly different from that of the typical two-gap superconductor MgB2. 相似文献
997.
Surface-emitted terahertz- (THz-) wave generation by difference-frequency mixing with ridge-shaped periodically poled lithium niobate (PPLN) was demonstrated. The PPLN had a ridge height of 300 microm, a thickness of 20 microm, and an interaction length of 35 mm. The ridge behaves as a slab waveguide for optical pump beams. The PPLN gives rise to THz waves in opposite directions, perpendicular to the pump-beam direction. Reflecting the THz wave on one side and overlapping it with the THz wave on the other side increased the total THz-wave intensity approximately 2.7 times compared with that without reflection and mixing. 相似文献
998.
999.
Ryota Imura Hiroyuki Ida Ichiro Sasaki Noriko S. Ishioka Shigeki Watanabe 《Molecules (Basel, Switzerland)》2021,26(16)
(1) Background: Deferoxamine B (DFO) is the most widely used chelator for labeling of zirconium-89 (89Zr) to monoclonal antibody (mAb). Despite the remarkable developments of the clinical 89Zr-immuno-PET, chemical species and stability constants of the Zr-DFO complexes remain controversial. The aim of this study was to re-evaluate their stability constants by identifying species of Zr-DFO complexes and demonstrate that the stability constants can estimate radiochemical yield (RCY) and chelator-to-antibody ratio (CAR). (2) Methods: Zr-DFO species were determined by UV and ESI-MS spectroscopy. Stability constants and speciation of the Zr-DFO complex were redetermined by potentiometric titration. Complexation inhibition of Zr-DFO by residual impurities was investigated by competition titration. (3) Results: Unknown species, ZrHqDFO2, were successfully detected by nano-ESI-Q-MS analysis. We revealed that a dominant specie under radiolabeling condition (pH 7) was ZrHDFO, and its stability constant (logβ111) was 49.1 ± 0.3. Competition titration revealed that residual oxalate inhibits Zr-DFO complex formation. RCYs in different oxalate concentration (0.1 and 0.04 mol/L) were estimated to be 86% and >99%, which was in good agreement with reported results (87%, 97%). (4) Conclusion: This study succeeded in obtaining accurate stability constants of Zr-DFO complexes and estimating RCY and CAR from accurate stability constants established in this study. 相似文献
1000.
J.M. Soares J.H. de Araújo F.A.O. Cabral F.L.A. Machado T. Dumelow M.M. Xavier J.M. Sasaki 《Journal of Non》2008,354(42-44):4883-4886
A combination of Langevin and hyperbolic tangent functions weighted by a log-normal particle size distributions were used to fit the magnetization curves of Fe10Ag90 granular alloys, produced by a sol–gel process under different chemical conditions. The fitting technique allows one to get both the superparamagnetic and the blocked particle size distributions. The average size of the Fe particles obtained from the fit were in good agreement with those obtained by X-ray diffraction. The correlation between the coercive field and the particle distribution was also investigated. Zero-field cooling dc magnetic susceptibility measurements were fitted using a similar technique to that used for fitting the magnetization curves. The saturation magnetization and mean Fe particle size values obtained from the two fittings were in good agreement. 相似文献