全文获取类型
收费全文 | 171篇 |
免费 | 16篇 |
国内免费 | 21篇 |
专业分类
化学 | 149篇 |
晶体学 | 1篇 |
力学 | 11篇 |
综合类 | 1篇 |
数学 | 12篇 |
物理学 | 34篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 6篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1991年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 140 毫秒
101.
Parisa Ghanbari Mahsa Mohseni Maryam Tabasinezhad Bahman Yousefi Amir Ata Saei Simin Sharifi Mohammad Reza Rashidi Nasser Samadi 《Applied biochemistry and biotechnology》2014,174(2):667-681
Combination therapy is considered a viable strategy to overcome the resistance to chemotherapeutics. Survivin as a member of the inhibitor of apoptosis protein (IAP) family, which is involved in resistance to various drugs. We investigated the role of combination therapy in downregulating survivin and increasing drug’s efficacy in MDA-MB-231 cells. MTT assay and DAPI staining were applied to study the anti-proliferative activity and apoptosis response of the agents. Real-time RT-PCR and Western blot analysis were applied to study survivin mRNA and protein. Our findings showed that combined treatment of cells with docetaxel and vinblastine reduces survivin expression and consequently decreases the IC50 value of docetaxel from 70 to 5 nM (p?0.05). Furthermore, combination therapy with deguelin, a survivin inhibitor, exerted a considerable enhancement in synergistic efficacy of docetaxel and vinblastine (p?0.05). Survivin downregulation may thus be considered a potential strategy in increasing the efficacy of chemotherapeutics in cancer patients. 相似文献
102.
由于8-氮杂鸟嘌呤(8-AG)的氧化还原电势比鸟嘌呤(G)更低,所以单电子氧化嵌有8-AG的DNA后,空穴最终会被8-AG捕获形成8-氮杂鸟嘌呤自由基阳离子(8-AG·+).因为酸性的急剧增强,8-AG·+一般会发生脱质子反应.在本工作中,在M06-2X/6-31+G(d)理论水平,使用显性水分子和连续溶剂化模型模拟8-AG·+的溶剂化效应,对其脱亚氨基质子(N(1)-H)反应进行了研究.发现位于8-AG·+中N(1)-H、O(6)、N(2)-H附近以及在O(6)水分子附近稍微远离8-AG·+的4个水分子会对8-AG·+脱质子反应产生重要影响,质子从8-AG·+传递到溶液中具有方向性;最后,通过进一步在N(2)-H、N(3)、O(6)、N(7)和N(8)等位点附近添加水分子(9H2O)得到了更加精确的8-AG·+脱质子反应能垒(19.5 kJ/mol). 相似文献
103.
基于CODCr的K2 Cr2O7滴定法和HACH(哈希公司)DR6000,结合design-expert拟合分析,得到CODCr精确测量的最佳方案:消解液加入量为3 mL,K2 Cr2O7与H2 SO4-Ag2 SO4的加入比为1:5(V/V),K2Cr2O7溶液0.046 g/mL、H2SO4-Ag2SO4溶液3 g/L、HgSO40.038 g/支,恒温120℃消解2 h。同时,基于拟定的最佳方案分析了营养盐类对CODCr测定结果的影响,发现氨氮和亚硝态氮对测定结果有明显影响,而磷酸盐和偏磷酸盐对测定结果的影响较小。 相似文献
104.
Hua Huang Jun Geng Simin He Bofu Li Canbin Ouyang Yuhai Yin Hui Cao Liping Wang Mingtan Hai Ge Wang Huai Yang 《Liquid crystals》2007,34(8):949-954
The properties of synthesized side-chain liquid crystalline polymer (SCLCP)/liquid crystal (LC)/chiral dopant composites having a chiral nematic (N*) phase at room temperature were investigated by polarized optical microscopy (POM) and a UV/VIS/NIR spectrophotometer. The composite exhibited a planar texture after it was filled into cells under homogeneous boundary conditions and it was transparent. When an electric field was applied to the composite, a focal conic texture was formed and the composite became light scattering. After the electric field was turned off, the light-scattering state remained stable for some time, i.e. the light-scattering state exhibited a memory effect. The focal conic texture changed into the planar texture when the composite was heated and the composite became transparent again. Therefore, the composite had electrically induced and thermally erased properties. The SCLCP had some influence on the memory effect and on the thermo-electro-optical properties of the composite. 相似文献
105.
Ehsan Faghani Simin Dokht Saemi Reza Maddahian Bijan Farhanieh 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(10):1439-1453
This paper investigates the impact of the inflow conditions on simulations of a round jet discharging from a wall into a large
space. The fluid dynamic characteristics of a round jet are studied numerically. A numerical method based on the control volume
approach with collocated grid arrangement is employed. The k-e{k-\varepsilon} model is utilized to approximate turbulent stresses by considering six different inlet conditions. The velocity field is
presented, and the rate of decay at the jet centerline is determined. The results showed that inflow conditions had a strong
influence on the jet characteristics. This paper also investigates both sharp-edged and contoured nozzles. The effects of
velocity, turbulence intensity, turbulence kinetic energy, and turbulence dissipation rate on flow field characteristics are
examined. Results showed that the present simulations in both types of nozzles are in good agreement with experiments when
considering the appropriate inflow conditions. 相似文献
106.
Gholami-Borujeni F Mahvi AH Nasseri S Faramarzi MA Nabizadeh R Alimohammadi M 《Applied biochemistry and biotechnology》2011,165(5-6):1274-1284
A crude preparation of horseradish roots was used as a low-purity source of horseradish peroxidase (HRP) in dye decolorization experiments. The technical feasibility of the process was studied in bench scale for enzymatic removal of acid orange 7 (AO7), a synthetic dye. Further studies were carried out to understand the effects of process parameters such as pH value, H(2)O(2) level, concentrations of the synthetic dye, and HRP during enzyme-mediated dye degradation. Experimental data revealed that the concentration of AO7, pH of the aqueous phase, amount of the enzyme, and H(2)O(2) level played significant roles on the overall enzymatic reaction. Polyethylene glycol, as an anti-inactivation of HRP, in various concentrations showed no significant effect on the decolorization. The experimental data of initial reaction rates were fitted using an analytical equation proposed by Michaelis-Menten. The acute toxicity tests using Daphnia magna exhibited that the enzymatic treatment significantly decreased the toxicity of the dye solution. 相似文献
107.
Xingeng Ding Simin Zhou Lifang Jiang Hui Yang 《Journal of Sol-Gel Science and Technology》2011,58(1):345-354
Nano-Titania/Nafion (TiO2/Nafion) hybrid membranes were prepared by recasting, using Nafion solution and TiO2 anatase hydrosol as the raw materials. The microstructure of the hybrid membrane was characterized by X-ray diffraction,
high-resolution transmission electron microscopy (HR-TEM), X-ray Photoelectron Spectroscopy and Fourier Transform Infrared
Spectroscopy (FT-IR). The photocatalytic properties of TiO2/Nafion hybrid membranes were evaluated. Furthermore, endurance of photocatalytic activity of the hybrid membrane was investigated.
The results indicate that the TiO2 Nanoparticles are bounded to Nafion molecule via Ti-O-S bonds and the formed flocculates are distributed homogeneously throughout
the recasting Nafion membrane, while the initial pure anatase TiO2 nanoparticles remain intact in re-crystallized membrane. The hybrid membranes possessed excellent photocatalytic activities
with and without H2O2. Moreover, the degradation of photocatalytic activities has been better controlled with the presence of H2O2. 相似文献
108.
The Hopf bifurcation of a new modified hyperchaotic Lü system with only one equilibrium is investigated in this paper. A detailed set of conditions are derived, which guarantee the existence of the Hopf bifurcation. Furthermore, by applying the normal form theory, the direction and type of the Hopf bifurcation, and the approximate expressions of bifurcating periodic solutions and their periods are determined. In addition, numerical simulation results supporting the theoretical analysis are given. 相似文献
109.
This paper presents a new three-dimensional autonomous chaotic system with only one positive term. Basic dynamical properties of the new attractor are demonstrated in terms of phase portraits, equilibria, Lyapunov exponents, Poincare mapping, bifurcation diagram. Furthermore, we derive a three-dimensional spheriform ultimate bound and positively invariant set for all the positive values of its parameters a, b, c. At last, the horseshoe chaos in this system is investigated based on the topological theory. 相似文献
110.
Chinese culture is like a vast starry sky where poetry and idioms are the bright pearls. This article followed the steps of Dahua and Xiaoxue into a primitive tribe, where they explored the charm of chemistry in poetry and idioms and appreciated the profoundness of Chinese culture. 相似文献