全文获取类型
收费全文 | 22606篇 |
免费 | 2968篇 |
国内免费 | 2175篇 |
专业分类
化学 | 11237篇 |
晶体学 | 163篇 |
力学 | 1137篇 |
综合类 | 64篇 |
数学 | 1660篇 |
物理学 | 6053篇 |
综合类 | 7435篇 |
出版年
2024年 | 91篇 |
2023年 | 432篇 |
2022年 | 612篇 |
2021年 | 717篇 |
2020年 | 707篇 |
2019年 | 615篇 |
2018年 | 601篇 |
2017年 | 555篇 |
2016年 | 926篇 |
2015年 | 861篇 |
2014年 | 1158篇 |
2013年 | 1339篇 |
2012年 | 1698篇 |
2011年 | 1679篇 |
2010年 | 1215篇 |
2009年 | 1200篇 |
2008年 | 1362篇 |
2007年 | 1209篇 |
2006年 | 1079篇 |
2005年 | 980篇 |
2004年 | 731篇 |
2003年 | 589篇 |
2002年 | 581篇 |
2001年 | 551篇 |
2000年 | 520篇 |
1999年 | 680篇 |
1998年 | 626篇 |
1997年 | 594篇 |
1996年 | 602篇 |
1995年 | 571篇 |
1994年 | 464篇 |
1993年 | 383篇 |
1992年 | 371篇 |
1991年 | 315篇 |
1990年 | 292篇 |
1989年 | 244篇 |
1988年 | 197篇 |
1987年 | 139篇 |
1986年 | 97篇 |
1985年 | 60篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 754 毫秒
991.
Zhang-Yu Nie Rong-Gen Cai Xin Gao Li Li Hui Zeng 《The European Physical Journal C - Particles and Fields》2015,75(11):559
In a previous paper (Nie et al. in JHEP 1311:087, arXiv:1309.2204 [hep-th], 2013), we presented a holographic s \(+\) p superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. We also study the competition and coexistence of the s-wave and p-wave orders in the probe limit. In this work we continue to study the model by considering the full back-reaction. The model shows a rich phase structure and various condensate behaviors such as the “n-type” and “u-type” ones, which are also known as reentrant phase transitions in condensed matter physics. The phase transitions to the p-wave phase or s \(+\) p coexisting phase become first order in strong back-reaction cases. In these first order phase transitions, the free energy curve always forms a swallow tail shape, in which the unstable s \(+\) p solution can also play an important role. The phase diagrams of this model are given in terms of the dimension of the scalar order and the temperature in the cases of eight different values of the back-reaction parameter, which show that the region for the s \(+\) p coexisting phase is enlarged with a small or medium back-reaction parameter but is reduced in the strong back-reaction cases. 相似文献
992.
993.
The nonlinear properties of lattice network-based(LNB) composite right-/left-handed transmission lines(CRLH TLs)with nonlinear capacitors are experimentally investigated.Harmonic generation,subharmonic generation,and parametric excitation are clearly observed in an unbalanced LNB CRLH TL separately.While the balanced design of the novel nonlinear TL shows that the subharmonic generation and parametric processes can be suppressed,and almost the same power level of the higher harmonics can be achieved over a wide bandwidth range,which are difficult to find in conventional CRLH TLs. 相似文献
994.
Ultrafast solvation dynamics at internal sites of staphylococcal nuclease investigated by site-directed mutagenesis
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Internal solvation of protein was studied by site-directed mutagenesis,with which an intrinsically fluorescent probe,tryptophan,is inserted into the desired position inside a protein molecule for ultrafast spectroscopic study.Here we review this unique method for protein dynamics research.We first introduce the frontiers of protein solvation,site-directed mutagenesis,protein stability and characteristics,and the spectroscopic methods.Then we present time-resolved spectroscopic dynamics of solvation dynamics inside cavities of active sites.The studies are carried out on a globular protein,staphylococcal nuclease.The solvation at sites inside the protein molecule’s cavities clearly reveals characteristics of the local environment.These solvation behaviors are directly correlated to enzyme activity. 相似文献
995.
In a laser butt joint welding process,it is required that the laser beam focus should be controlled to follow the weld joint path accurately.Small focus wandering off the weld joint may result in insufficient penetration or unacceptable welds.Recognition of joint position offset,which describes the deviation between the laser beam focus and the weld joint,is important for adjusting the laser beam focus and obtaining high quality welds.A new method based on the magneto-optical(MO)imaging is applied to measure the micro weld joint whose gap is less than 0.2 mm.The weldments are excited by an external magnetic field,and an MO sensor based on principle of Faraday magneto effect is used to capture the weld joint images.A sequence of MO images which are tested under different magnetic field intensities and different weld joint widths are acquired.By analyzing the MO image characteristics and extracting the weld joint features,the influence of magnetic field intensity and weld joint width on the MO images and detection of weld joint position is observed and summarized. 相似文献
996.
Kun Gao Chang-Song Dai Jing Lv Xiang-Ming Feng 《Russian Journal of Electrochemistry》2014,50(3):267-273
To improve the electrochemical performance of Li2MnSiO4 with low electric conductivity, the Li2MnSiO4/C composite are synthesized by a vacuum solid-state reaction of a mixture of SiO2, LiCH3COO, Mn(CH3COO)2 and designed mass of C6H12O6 · H2O as carbon sources. The crystalline structure and morphology of products are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering technology (LS) respectively. The tested results show that carbon doping decrease the crystallite sizes of products, but keep the aggregation of the particles and made the impurity increased instead. The results of constant current charge-discharge prove that the mixed carbon improve Li+ transmission performance and decrease inner polatization resistance of Li2MnSiO4 materials, but can not prevent the collapse of Li2MnSiO4 crystal structure. While the galvanostatic intermittent titration technique (GITT) results demonstrate that the primary reason for the improved electrochemical performance can be attributed to increased Li-ion diffusion coefficient $(D_{Li^ + } )$ as a result from carbon doping. 相似文献
997.
A new Anderson-based heteropolymolybdate {[Eu(H2O)6]2(TeMo6O24)}·6H2O (1) has been hydrothermally synthesized and characterized by elemental analyses, IR, thermal stability analysis, XRD and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system, space group P-1, a = 9.4023(6) Å, b = 10.2530(7) Å, c = 10.6525(10) Å, α = 101.583(7)º, β = 108.024(7)º, γ = 107.150(6)º, V = 883.60(12) Å3, Z = 1, R1 = 0.0338, wR2 = 0.0849. Compound 1 exhibits 1D chain-like structure formed by the alternative connection between Anderson type polyoxoanions [TeMo6O24]6? and Eu3+ along a-axis. Compound 1 displays good fluorescent emission of the Eu3+ ion at room temperature. 相似文献
998.
A High Sensitivity Electrochemical Sensor Based on Fe3+‐Ion Molecularly Imprinted Film for the Detection of T‐2 Toxin
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xing Gao Wenying Cao Miaomiao Chen Huayu Xiong Xiuhua Zhang Shengfu Wang 《Electroanalysis》2014,26(12):2739-2746
The excellent detection sensitivity in various matrices of T‐2 toxin (T‐2), which has cytotoxic and immunosuppressive effects in DNA and RNA synthesis, is a highly desirable characteristic. A sensitive molecularly imprinted electrochemical sensor was constructed for the selective detection of T‐2. In this study, iron ions (Fe3+) were introduced to increase the chelation of the metal ions and templates for preparing molecularly imprinted polymers (MIPs). With the increased chelation of the metal ions and templates, the selectivity and sensitivity of the MIPs were effectively improved. The imprinted sensor was successfully employed to detect T‐2 in cereals and human serum samples. 相似文献
999.
Li Yuan Sidi Huang Yinhui Hu Yuzheng Zhang Aijuan Gu Guozheng Liang Guoqiang Chen Yongming Gao Steven Nutt 《先进技术聚合物》2014,25(7):752-759
Self‐healing cyanate ester resins (CE) were developed by adding low molecular weight poly(phenylene oxide) (PPO) resin, yielding a high performance CE/PPO system via a low‐temperature process. The addition of PPO improved the flexural strength and fracture toughness of the CE matrix without sacrificing thermal properties. CE/PPO formulations with 5, 10, and 15 wt.% PPO showed 43%, 65%, and 105% increase in fracture toughness due to a combination of crack deflection, crack pinning, and matrix cavitation around second‐phase particles. When PPO was introduced into the CE, dielectric properties were either unchanged or declined. During thermal treatment to heal damaged CE, liquid PPO flowed into cracks, and during subsequent cooling, solidified to bond the crack surfaces. The self‐healing efficiency for CE with 15 wt.% PPO after heating to 220°C for 1 h exhibited a recovery of 73% in toughness and 81% in microtensile strength. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
This work demonstrates the successful incorporation of functionalized single‐walled carbon nanotubes (f‐SWCNTs) into the phenylboronate‐diol crosslinked polymer gel to create a hybrid system with reversible sol–gel transition. The phenylboronic acid‐containing and diol‐containing polymers were first separately prepared by the reversible addition–fragmentation chain transfer polymerization. Covalent functionalization of single‐walled carbon nanotubes (SWCNTs) with an azide‐derivatized, diol‐containing polymer was then accomplished by a nitrene addition reaction. Subsequently, the hybrid gels were prepared by crosslinking the mixture of f‐SWCNTs and diol‐containing polymer with the phenylboronic acid‐containing polymer. The hybrid gel has been characterized by scanning electron microscopy (SEM) and rheological analysis. The SEM measurement demonstrated a homogeneous dispersion of f‐SWCNTs within the gel matrices. Rheological experiments also demonstrated that the hybrid gel exhibited storage moduli significantly higher than those of the native gel obtained from the phenylboronic acid‐containing and diol‐containing polymers. The hybrid gel can be switched into their starting polymer (f‐SWCNTs) solutions by adjusting the pH of the system. Moreover, the hybrid gel revealed a self‐healing property that occurred autonomously without any outside intervention. By employing this dynamic character, it is possible to regenerate the used gel, and thus, it has the potential to perform in a range of dynamic or bioresponsive applications Copyright © 2013 John Wiley & Sons, Ltd. 相似文献