全文获取类型
收费全文 | 726篇 |
免费 | 32篇 |
国内免费 | 10篇 |
专业分类
化学 | 562篇 |
晶体学 | 3篇 |
力学 | 19篇 |
数学 | 70篇 |
物理学 | 114篇 |
出版年
2023年 | 8篇 |
2022年 | 55篇 |
2021年 | 60篇 |
2020年 | 31篇 |
2019年 | 37篇 |
2018年 | 34篇 |
2017年 | 16篇 |
2016年 | 46篇 |
2015年 | 28篇 |
2014年 | 43篇 |
2013年 | 61篇 |
2012年 | 60篇 |
2011年 | 53篇 |
2010年 | 29篇 |
2009年 | 27篇 |
2008年 | 36篇 |
2007年 | 25篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1940年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有768条查询结果,搜索用时 15 毫秒
101.
Seyyed Hossein Miraghaie Ashkan Zandi Zahra Davari Mohamad Sadegh Mousavi-kiasary Zohre Saghafi Ali Gilani Yasin Kordehlachin Fatemeh Shojaeian Amir Mamdouh Zahra Heydari Farid Abedin Dorkoosh Babak Kaffashi Mohammad Abdolahad 《Macromolecular bioscience》2023,23(9):2300181
Pure positive electrostatic charges (PPECs) show suppressive effect on the proliferation and metabolism of invasive cancer cells without affecting normal tissues. PPECs are used for the delivery of drug-loaded polymeric nanoparticles (DLNs) capped with negatively charged poly(lactide-co-glycolide) (PLGA) and Poly(vinyl-alcohol) PVA into the tumor site of mouse models. The charged patch is installed on top of the skin in the mouse models' tumor region, and the controlled selective release of the drug is assayed by biochemical, radiological, and histological experiments on both tumorized models and normal rats' livers. It is found that DLNs synthesized by PLGA show great attraction to PPECs due to their stable negative charges, which would not degrade immediately in blood. The burst and drug release after less than 48h of this synthesized DLNs are 10% and 50%, respectively. These compounds can deliver the loaded-drug into the tumor site with the assistance of PPECs, and the targeted-retarded release will take place. Hence, local therapy can be achieved with much lower drug concentration (conventional chemotherapy [2 mg kg−1] versus DLNs-based chemotherapy [0.75 mg kg−1]) with negligible side effects in non-targeted organs. PPECs have many potential clinical applications for advanced-targeted chemotherapy with the lowest discernible side effects. 相似文献
102.
103.
Unlike the common high temperature pyrolysis of carboxymethylcellulose (CMC) targeting activated carbon, this study investigates the pyrolytic behaviour of plain CMC at low temperatures ranging between 260 and 300 °C. Preliminary experiments were conducted using differential scanning calorimetry to define the temperature range necessary for the process. Low-temperature pyrolysis was then simulated using thermogravimetric analysis under inert atmosphere. Investigations reveal that a minimum holding temperature of 260 °C is required for an isothermal process, at which pyrolysis is terminated after around 26 min. Increasing exposure temperature reduces pyrolysis time. Within the range of the investigated sample and CMC particle size, no significant effects could be measured regarding the decomposition behaviour. The resulting char was further analysed using X-ray diffraction and Fourier transform infrared spectroscopy. Visual inspection was conducted using scanning electron microscopy. Upon pyrolysis, originally longitudinally shaped CMC was found to be converted into spherical particles of functionalised amorphous carbon with an average particle size of 41 µm. 相似文献
104.
Muhammad Umar Aslam Khan Iqra Iqbal Mohamed Nainar Mohamed Ansari Saiful Izwan Abd Razak Mohsin Ali Raza Amna Sajjad Faiza Jabeen Mohd Riduan Mohamad Norhana Jusoh 《Molecules (Basel, Switzerland)》2021,26(19)
The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications. 相似文献
105.
We have studied the effect of subsequent gamma (γ) irradiation on the absorption spectra and the optical energy gap of ZnO thin films doped with Li (ZnO:Li). The optical transmission (T) and optical reflection (R) in the wavelength range 190∼800 nm of films deposited at 300 °C on sapphire, MgO or quartz substrates were measured. The dependence of the absorption coefficient α on photon energy hν was determined as a function of γ‐doses. The films show direct allowed interband transition that influenced by the gamma doses. Both the optical energy gap Eoptg and the absorption coefficient (α) were found to be γ‐dose dependent. The results can be discussed on the basis of γ‐irradiation‐induced defects in the film and on the film structure. The absorption coefficient exhibits exponential dependence on photon energy obeying Urbach's rule in the absorption edge. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
106.
Rafat M. Mohareb Sherif M. Sherif Hatem M. Gaber Sami S. Ghabrial Susan I. Aziz 《Heteroatom Chemistry》2004,15(1):15-20
Benzo[b]thiophen-2-yl-hydrazonoesters 4 were synthesized by coupling of 2-diazo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide ( 1 ) with either ethyl cyanoacetate or ethyl acetoacetate. The reactivity of 4 toward a variety of nitrogen nucleophiles was investigated to yield pyrazole, isoxazole, pyrimidine, triazine, pyrazolopyridine, and pyrazolopyrimidine derivatives. © 2003 Wiley Periodicals, Inc. 15:15–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10205 相似文献
107.
Hemalatha Murugaiah Chow Lun Teh Kai Chew Loh Ahmad Ramli Mohamad Yahya Nur Asshifa Md Noh Noor Hana Hanif Abu Bakar Daruliza Kernain Rokiah Hashim Yazmin Bustami 《Molecules (Basel, Switzerland)》2021,26(21)
Here, we report the extracellular biosynthesis of silver nanoparticles (AgNPs) and determination of their antibacterial and anticancer properties. We also explore the efficacy of bioAgNPs incorporated in cellulose nanocrystals (CNCs) and alginate (Alg) for the formation of an antibacterial hydrogel film. Streptomyces sp. PBD-311B was used for the biosynthesis of AgNPs. The synthesized bioAgNPs were characterized using UV-Vis spectroscopy, TEM, XRD, and FTIR analysis. Then, the bioAgNPs’ antibacterial and anticancer properties were determined using TEMA and cytotoxicity analysis. To form the antibacterial hydrogel film, bioAgNPs were mixed with a CNC and Alg solution and further characterized using FTIR analysis and a disc diffusion test. The average size of the synthesized bioAgNPs is around 69 ± 2 nm with a spherical shape. XRD analysis confirmed the formation of silver nanocrystals. FTIR analysis showed the presence of protein capping at the bioAgNP surface and could be attributed to the extracellular protein binding to bioAgNPs. The MIC value of bioAgNPs against P. aeruginosa USM-AR2 and MRSA was 6.25 mg/mL and 3.13 mg/mL, respectively. In addition, the bioAgNPs displayed cytotoxicity effects against cancer cells (DBTRG-0.5MG and MCF-7) and showed minimal effects against normal cells (SVG-p12 and MCF-10A), conferring selective toxicity. Interestingly, the bioAgNPs still exhibited inhibition activity when incorporated into CNC/Alg, which implies that the hydrogel film has antibacterial properties. It was also found that bioAgNP-CNC/Alg displayed a minimal or slow release of bioAgNPs owing to the intermolecular interaction and the hydrogel’s properties. Overall, bioAgNP-CNC/Alg is a promising antibacterial hydrogel film that showed inhibition against the pathogenic bacteria P. aeruginosa and MRSA and its application can be further evaluated for the inhibition of cancer cells. It showed benefits for surgical resection of a tumor to avoid post-operative wound infection and tumor recurrence at the surgical site. 相似文献
108.
The reaction of 2‐amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]thiophene ( 1 ) with diethyl malonate ( 2 ) gave two products: 3 and 4 . The reactivity of 3 toward a variety of chemical reagents was studied to give azoles, azines, and their fused derivatives. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:168–175, 2001 相似文献
109.
This study is to investigate the magnetohydrodynamic (MHD) stagnation point flow and heat transfer characteristic nanofluid of carbon nanotube (CNTs) over the shrinking surface with heat sink effects. Similarity equations deduced from momentum and energy equation of partial differential equations are solved numerically. This study looks at the different parameters of the flow and heat transfer using first phase model which is Tiwari-Das. The parameter discussed were volume fraction nanoparticle, magnetic parameter, heat sink/source parameters, and a different type of nanofluid and based fluids. Present results revealed that the rate of nanofluid (SWCNT/kerosene) in terms of flow and heat transfer is better than (MWCNT/kerosene) and (CNT/water) and regular fluid (water). Graphically, the variation results of dual solution exist for shrinking parameter in range for different values of volume fraction nanoparticle, magnetic, heat sink parameters, and a different type of nanofluid. However, a unique solution exists at , and no solutions exist at which is a critical value. In addition, the local Nusselt number decreases with increasing volume fraction nanoparticle when there exists a heat sink effect. The values of the skin friction coefficient and local Nusselt number increase for both solutions with the increase in magnetic parameter. In this study, the investigation on the flow and heat transfer of MHD stagnation point nanofluid through a shrinking surface with heat sink effect shows how important the application to industrial applications. 相似文献
110.
Alex Durkin Ivan Taptygin Dr. Qingyuan Kong Mohamad F. M. Gunam Resul Abdul Rehman Dr. Ana M. L. Fernández Prof. Adam P. Harvey Prof. Nilay Shah Dr. Miao Guo 《ChemistryOpen》2019,8(6):668-688
Poly(limonene carbonate) (PLC) has been highlighted as an attractive substitute to petroleum derived plastics, due to its utilisation of CO2 and bio-based limonene as feedstocks, offering an effective carbon capture and utilisation pathway. Our study investigates the techno-economic viability and environmental sustainability of a novel process to produce PLC from citrus waste derived limonene, coupled with an anaerobic digestion process to enable energy cogeneration and waste recovery maximisation. Computational process design was integrated with a life cycle assessment to identify the sustainability improvement opportunities. PLC production was found to be economically viable, assuming sufficient citrus waste is supplied to the process, and environmentally preferable to polystyrene (PS) in various impact categories including climate change. However, it exhibited greater environmental burdens than PS across other impact categories, although the environmental performance could be improved with a waste recovery system, at the cost of a process design shift towards energy generation. Finally, our study quantified the potential contribution of PLC to mitigating the escape of atmospheric CO2 concentration from the planetary boundary. We emphasise the importance of a holistic approach to process design and highlight the potential impacts of biopolymers, which is instrumental in solving environmental problems facing the plastic industry and building a sustainable circular economy. 相似文献