全文获取类型
收费全文 | 1475篇 |
免费 | 42篇 |
国内免费 | 7篇 |
专业分类
化学 | 1070篇 |
晶体学 | 16篇 |
力学 | 19篇 |
数学 | 165篇 |
物理学 | 254篇 |
出版年
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 69篇 |
2012年 | 54篇 |
2011年 | 82篇 |
2010年 | 43篇 |
2009年 | 51篇 |
2008年 | 80篇 |
2007年 | 98篇 |
2006年 | 93篇 |
2005年 | 100篇 |
2004年 | 85篇 |
2003年 | 67篇 |
2002年 | 73篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 15篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 21篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1968年 | 5篇 |
排序方式: 共有1524条查询结果,搜索用时 31 毫秒
991.
Dr. Takao Noguchi Dr. Bappaditya Roy Dr. Daisuke Yoshihara Dr. Youichi Tsuchiya Dr. Tatsuhiro Yamamoto Prof. Seiji Shinkai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):381-384
A novel tetraphenylethene‐based fluorescence (FL) chemosensor exhibits nonlinear turn‐on FL switching though cooperative binding of L ‐tartarate, where its convergent binding to form cyclic substructures is responsible for the FL increase. This binding scheme achieves selective detection of dicarboxylates over monocarboxylates, thus is potentially applicable to the preliminary screening for metabolic disorders. 相似文献
992.
Based on the Rollins-Hunt's model, chaotic phenomena in a driven coupled R-L-diode oscillator are examined numerically. It is found that a straightforward extension of this model to a system with two degrees of freedom is valid as far as the quasiperiodic route to chaos is concerned. However, this model is not sufficient to explain the intermittency and the quasiperiodic routes including the discontinuous (jump) bifurcations with hysteresis. Then it is shown that the additional nonlinearity due to variable capacitance of the diode is effective to explain the above phenomena. It is also shown that a two-dimensional discrete return map in which nonlinear terms are introduced in a characteristic form simulates systematically the numerical results. In particular, this map model can explain effectively the mechanisms which cause the intermittency and the cliscontinuous bifurcation. 相似文献
993.
994.
Takao Akahori 《Journal of Mathematical Analysis and Applications》2006,322(1):207-213
Let X be a Kaehler manifold with complex dimension n. Let ωX be its Kaehler form. Let M be a strongly pseudo convex real hypersurface in X. For this hypersurface, the deformation theory of CR structures is successfully developed. And we find that H1(M,T′) (the T′-valued Kohn-Rossi cohomology) is the Zariski tangent space of the versal family. In this paper, the geometrical meaning of H1(M,O) is studied, and we propose to study displacements of the real hypersurface, which preserves the type of the differential form, ωX, over CR structures, on M, infinitesimally. 相似文献
995.
Masanobu Haraguchi Teruyuki Nakai Akihiko Shinya Toshihiro Okamoto Masuo Fukui Takao Koda Ryoko Shimada Kenji Takeda 《Optical Review》1999,6(3):261-267
We have experimentally observed the interaction of near-field light excited in a total internal reflection geometry with a periodic two-dimensional array of polystyrene spheres. The angular- and frequencyscanned attenuated-total-reflection (ATR) method was employed to observe the interaction. ATR spectra indicate that there is an easy axis and a difficult axis for the light propagation. When light is incident toward the easy axis, resonant dips appear in the ATR spectra. The experimental results were compared with those obtained by finite-difference time-domain analysis. The numerical results obtained by this method are able to explain a part of the experimental ones. Parts of the dips in the ATR spectra were considered to stem from propagating and whispering-gallery (WG) modes. That is, the propagation of the WG-modes over several spheres may enhance the coupling between the spheres and the incident light, and consequently may induce resonant structures in the ATR spectra.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Nearfield Nano-optics” Project, sponsored by Japan Society for the Promotion of Science. 相似文献
996.
Takao Tsuda Shinya Kitagawa Takayuki Umeyama Shuki Araki Tsunehisa Hirashita Mutumi Aoki Koichi Nakamura 《Analytical sciences》2006,22(3):479-481
A continuous flow-type hydrothermal reaction system, in which both temperature and pressure were rapidly and dynamically controlled, was constructed. It is called a real time high temperature and pressure reaction system (RT-HighTP). The RT-HighTP was hyphenated with liquid chromatograph (RT-HighTP-LC) to achieve prompt analysis of the reaction products. The RT-HighTP system produced stable pressure under the supercritical and subcritical phases (%RSD < 3%). The RT-HighTP-LC was able to change the hydrothermal condition rapidly. The hydrothermal products under four conditions were analyzed within 70 min. Further, the hydrothermal products of lignin was easily taken out using the sample collecting loop and analyzed by an external instrument of GC/MS. 相似文献
997.
Nanocrystalline silicon (nc-Si) films were prepared by a plasma-enhanced chemical vapor deposition method at a deposition temperature below 220 °C with different dynamic pressures (Pg), hydrogen flow rates ([H2]), and RF powers, using SiH4/H2/SiF4 mixtures. We examined the photo-luminescence (PL) spectra and the structural properties. We observed two stronger and weaker PL spectra with a peak energies around EPL = 1.8 and 2.2-2.3 eV, respectively, suggesting that the first band was related to nanostructure in the films, and another band was associated with SiO-related bonds. The nc-Si films with rather large PL intensity was obtained for high [H2] and/or low pressure values, However, effects of [H2] are likely to be different from those of Pg. The average grain size (δ) and the crystalline volume fraction (ρ) at first rapidly increase, and then slowly increase, with increasing Pg. Other parameters exhibited opposite behaviors from those of δ or ρ. These results were discussed in connection with the changes in the PL properties with varying the deposition conditions. 相似文献
998.
999.
The concept of pure gaps of a Weierstrass semigroup at several points of an algebraic curve has been used lately to obtain
codes that have a lower bound for the minimum distance which is greater than the Goppa bound. In this work, we show that the
existence of total inflection points on a smooth plane curve determines the existence of pure gaps in certain Weierstrass
semigroups. We then apply our results to the Hermitian curve and construct codes supported on several points that compare
better to one-point codes from that same curve.
相似文献
1000.
A systematic study of the magnetic properties by ion beam sputter-deposition system, was conducted in conjunction with the structure of FePt/FeMn multilayers fabricated onto MgO(0 0 1) substrates. Both parallel and perpendicular exchange biases were observed in the multilayers and were found to decrease drastically, as the deposition temperature is higher than 350 °C, which is evidently due to the interdiffusion at the interface. The thickness dependence study shows that the perpendicular magnetic anisotropy observed in the multilayers originates from surface anisotropy, being consistent with the decrease of perpendicular magnetic anisotropy as the deposition temperature is increased. The difference between parallel and perpendicular blocking temperatures that was clearly observed, is possibly due to the spin canting out of plane at the interface. 相似文献