全文获取类型
收费全文 | 1078篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
化学 | 480篇 |
晶体学 | 12篇 |
力学 | 14篇 |
数学 | 141篇 |
物理学 | 449篇 |
出版年
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 42篇 |
2012年 | 36篇 |
2011年 | 43篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 45篇 |
2007年 | 47篇 |
2006年 | 45篇 |
2005年 | 40篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 37篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 27篇 |
1993年 | 28篇 |
1992年 | 37篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 20篇 |
1972年 | 13篇 |
1967年 | 8篇 |
排序方式: 共有1096条查询结果,搜索用时 15 毫秒
1.
O. Maksimov P. Fisher M. Skowronski P.A. Salvador M. Snyder J. Xu X. Weng 《Journal of Crystal Growth》2008,310(11):2760-2766
MgO films were grown on (0 0 1) yttria-stabilized zirconia (YSZ) substrates by molecular beam epitaxy (MBE). The crystalline structures of these films were investigated using X-ray diffraction and transmission electron microscopy. Growth temperature was varied from 350 to 550 °C, with crystalline quality being improved at higher temperatures. The MgO films had a domain structure: (1 1 1)[1 1 2¯]MgO(0 0 1)[1 0 0]YSZ with four twin variants related by a 90° in-plane rotation about the [1 1 1]MgO axis. The observed epitaxial orientation was compared to previous reports of films grown by pulsed laser deposition and sputtering and explained as resulting in the lowest interface energy. 相似文献
2.
Anita M. R. Fisher Kathleen Danenberg Debabrata Banerjee Joseph R. Bertino Peter Danenberg Charles J. Gomer 《Photochemistry and photobiology》1997,66(2):265-270
Loss of p53 function has been correlated with decreased sensitivity to chemotherapy and radiation therapy in a variety of human tumors. Comparable analysis of p53 status with sensitivity to oxidative stress induced by pho-todynamic therapy has not been reported. In the current study we examined photosensitivity in human promye-locytic leukemia HL60 cells exhibiting either wild-type p53, mutated p53 or deleted p53 expression. Experiments were performed using a purpurin, tin ethyl etiopurpurin (SnET2)-, or a porphyrin, Photofrin (PH)-based photo-sensitizer. Total SnET2 accumulation was comparable in all three cell lines. Uptake of PH was highest in cells expressing wild-type p53 but incubation conditions could be adjusted to achieve equivalent cellular PH levels during experiments that analyzed photosensitivity. Survival measurements demonstrated that HL60 cells expressing wild-type p53 were more sensitive to PH- and SnET2-mediated photosensitization, as well as to UVC irradiation, when compared to HL60 cells exhibiting deleted or mutated p53 phenotypes. A rapid apoptotic response was observed following purpurin- and porphyrin-induced photosensitization in all cell lines. Results of this study indicate that photosensitivity is increased in HL60 cells expressing wild-type p53 and that photosensitizer-medi-ated oxidative stress can induce apoptosis through a p53-independent mechanism in HL60 cells . 相似文献
3.
4.
5.
J. T. Chayes L. Chayes Daniel S. Fisher T. Spencer 《Communications in Mathematical Physics》1989,120(3):501-523
Thed-dimensional, nearest-neighbor disordered Ising ferromagnet: $$H = - \sum {J_{ij} \sigma _i \sigma _j }$$ is studied as a function of both temperature,T, and a disorder parameter,λ, which measures the size of fluctuations of couplingsJ ij ≧0. A finite-size scaling correlation length,ζ f (T, λ), is defined in terms of the magnetic response of finite samples. This correlation length is shown to be equivalent, in the scaling sense, to the quenched average correlation lengthζ(T, λ), defined as the asymptotic decay rate of the quenched average two-point function. Furthermore, the magnetic response criterion which definesζ f is shown to have a scale-invariant property at the critical point. The above results enable us to prove that the quenched correlation length satisfies: $$C\left| {\log \xi (T)} \right|\xi (T) \geqq \left| {T - T_c } \right|^{ - {2 \mathord{\left/ {\vphantom {2 d}} \right. \kern-\nulldelimiterspace} d}}$$ which implies the boundv≧2/d for the quenched correlation length exponent. 相似文献
6.
7.
8.
9.
10.
W. G. Fisher W. P. Partridge Jr. C. Dees E. A. Wachter 《Photochemistry and photobiology》1997,66(2):141-155
The excitation and emission properties of several psoralen derivatives are compared using conventional single-photon excitation and simultaneous two-photon excitation (TPE). Two-photon excitation is effected using the output of a mode-locked titanium: sapphire laser, the near infrared output of which is used to promote non-resonant TPE directly. Specifically, the excitation spectra and excited-state properties of 8-methoxypsoralen and 4′-aminomethyl-4,5,8-trimethylpsoralen are shown to be equivalent using both modes of excitation. Further, in vitro feasibility of two-photon photodynamic therapy (PDT) is demonstrated using Salmonella typhimurium. Two-photon excitation may be beneficial in the practice of PDT because it would allow replacement of visible or UV excitation light with highly penetrating, nondamag-ing near infrared light and could provide a means for improving localization of therapy. Comparison of possible laser excitation sources for PDT reveals the titanium: sapphire laser to be exceptionally well suited for nonlinear excitation of PDT agents in biological systems due to its extremely short pulse width and high repetition rate that together provide efficient PDT activation and greatly reduced potential for biological damage 相似文献