全文获取类型
收费全文 | 9298篇 |
免费 | 1534篇 |
国内免费 | 1253篇 |
专业分类
化学 | 6855篇 |
晶体学 | 146篇 |
力学 | 408篇 |
综合类 | 107篇 |
数学 | 1069篇 |
物理学 | 3500篇 |
出版年
2024年 | 37篇 |
2023年 | 153篇 |
2022年 | 322篇 |
2021年 | 332篇 |
2020年 | 356篇 |
2019年 | 428篇 |
2018年 | 305篇 |
2017年 | 302篇 |
2016年 | 420篇 |
2015年 | 494篇 |
2014年 | 594篇 |
2013年 | 717篇 |
2012年 | 881篇 |
2011年 | 860篇 |
2010年 | 671篇 |
2009年 | 663篇 |
2008年 | 718篇 |
2007年 | 633篇 |
2006年 | 549篇 |
2005年 | 422篇 |
2004年 | 374篇 |
2003年 | 274篇 |
2002年 | 252篇 |
2001年 | 200篇 |
2000年 | 141篇 |
1999年 | 147篇 |
1998年 | 109篇 |
1997年 | 91篇 |
1996年 | 107篇 |
1995年 | 97篇 |
1994年 | 76篇 |
1993年 | 67篇 |
1992年 | 59篇 |
1991年 | 43篇 |
1990年 | 39篇 |
1989年 | 25篇 |
1988年 | 32篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
We use previous high-quality experimental spectra to test the accuracy of atomic data and the validity of the collisional-radiative (CR) model used in this paper. The synthetic spectrum with electron temperature log T_e(K)=6.745 and electron density n_e=6.0×10^{13}cm^{-3}, which almost reproduces the experimental spectra, is presented. Nearly all the features of the experimental spectra were identified. The results of the CR modelling for the emission spectra of calcium plasmas all agree well with the measured spectral line intensities within the experimental error for most of the lines. Furthermore, we make the electron temperature diagnostic through the synthetic spectrum and population fractions of every ionization state as a function of charge state at different electron temperatures, as well as the electron density diagnostic through the intensity ratios of two lines of Be-like calcium and three lines of C-like calcium. A good agreement between the calculated values and the measured ones is found. 相似文献
132.
Single crystalline GaN nanoribbons were synthesized through nitriding Ga2O3 thin films deposited on sapphire (0001) substrates by radio frequency magnetron sputtering. The component and structure of nanoribbons were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The flat and smooth ribbon-like nanostructures are high quality single crystalline hexagonal wurtzite GaN. The thickness and width-to-thickness ratio of the grown GaN nanoribbons are in the range of 8-15 nm and ∼5-10, respectively. 相似文献
133.
本文在传统的力学量测定的实验基础上,利用电学量参数变化测定杨氏模量,达到研究应力与应变的规律。 相似文献
134.
135.
In this paper, we study the cascading failure in Watts-Strogatz small-world networks. We find that this network model has a heterogeneous betweenness distribution, although its degree distribution is homogeneous. Further study shows that this small-world network is robust to random attack but fragile to intentional attack, in the cascading failure scenario. With comparison to standard random graph and scale-free networks, our result indicates that the robust yet fragile property in the cascading failure scenario is mainly related to heterogeneous betweenness, rather than the network degree distribution. Thus, it suggests that we have to be very careful when we use terms such as homogeneous network and heterogeneous network, unless the distribution we refer to is specified. 相似文献
136.
We demonstrate low-loss chalcogenide (As(2)S(3)) waveguides on a LiNbO(3) substrate for the mid-IR wavelength (4.8 μm). Designed for single-mode propagation, they are fabricated through photolithography and dry-etching technology and characterized on a mid-IR measurement setup with a quantum cascade laser. For straight waveguides, propagation loss as low as 0.33 dB/cm is measured and low-loss bends on the order of 100 μm are simulated, with measurement results showing <3 dB for a 250 μm bend radius. The coupling efficiency is estimated to be 81%. In addition, the influences of variations in width and bend radius are also investigated. 相似文献
137.
X. B. Zeng A. W. N. Leung X. S. Xia H. P. Yu D. Q. Bai J. Y. Xiang Y. Jiang C. S. Xu 《Laser Physics》2010,20(6):1500-1503
In the present study, we have successfully set up a novel blue light source with the power density of 9 mW/cm2 and the wavelength of 435.8 nm and then the novel light source was used to investigate the effect of light radiation on curcumin-induced cell death. The cytotoxicity was investigated 24 h after the treatment of curcumin and blue light radiation together using MTT reduction assay. Nuclear chromatin was observed using a fluorescent microscopy with Hoechst33258 staining. The results showed blue light radiation could significantly enhance the cytotoxicity of curcumin on the MCF-7 cells and apoptosis induction. These findings demonstrated that blue light radiation could enhance curcumin-induced cell death of breast cancer cells, suggesting light radiation may be an efficient enhancer of curcumin in the management of breast cancer. 相似文献
138.
139.
Spectrophotometric studies on the interaction between pazufloxacin mesilate and human serum albumin or lysozyme 总被引:1,自引:0,他引:1
The binding of pazufloxacin mesilate (PZFX) to human serum albumin (HSA) or lysozyme (Lys) was investigated using spectrophotometric techniques. The intrinsic fluorescence of both HSA and Lys was strongly quenched by PZFX. This effect was rationalized in terms of a static quenching procedure. Negative values of ΔH0 and ΔS0 for the formation of PZFX-HSA or PZFX-Lys complex implied that both hydrogen bonds and hydrophobic interactions might play a significant role in PZFX binding to HSA or Lys. The binding distances deduced from the efficiency of energy transfer were 4.04 and 3.21 nm for PZFX-HSA and PZFX-Lys systems, respectively. Furthermore, association constants and binding mechanism were successfully derived from the synchronous fluorescence spectra. Circular dichroism (CD) spectra and UV/vis detections supported a change in the secondary structure of proteins caused by the interaction of PZFX with HSA or Lys. 相似文献
140.
Zhendong Hao Jiahua Zhang Xia Zhang Shaozhe Lu Yongshi Luo Xinguang Ren Xiaojun Wang 《Journal of luminescence》2008,128(5-6):941-944
α- and β-Ca2P2O7: Eu2+, Mn2+ phosphors were prepared by solid-state reaction. Phase transition from tetragonal (β-phase) to monoclinic (α-phase) is performed. A strong orange emission of Mn2+ is observed in both α-and β-Ca2P2O7: Eu2+, Mn2+ upon near ultraviolet (UV) excitation through energy transfer from Eu2+ to Mn2+. The transfer efficiencies for various Mn2+ concentrations are estimated based on lifetime measurements of the fluorescence of Eu2+ in the two phases. The photoluminescence excitation spectra of α-Ca2P2O7: Eu2+, Mn2+ can cover 400 nm of the near-UV range, denoting its potential use as a phosphor with intense orange component for white light emitting diodes (LEDs). 相似文献