全文获取类型
收费全文 | 504篇 |
免费 | 38篇 |
国内免费 | 12篇 |
专业分类
化学 | 380篇 |
晶体学 | 5篇 |
力学 | 10篇 |
数学 | 27篇 |
物理学 | 132篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 25篇 |
2021年 | 59篇 |
2020年 | 35篇 |
2019年 | 33篇 |
2018年 | 25篇 |
2017年 | 20篇 |
2016年 | 33篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 34篇 |
2012年 | 22篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有554条查询结果,搜索用时 151 毫秒
1.
Yousaf Raffia bintay Bakar Shahzad Abu Mazhar Muhammad Mansoor Muhammad Adil Iqbal Mudassir 《Russian Journal of Applied Chemistry》2022,95(1):37-45
Russian Journal of Applied Chemistry - Owing to high stability, metal oxide-based ceramic thin films are of great interest for photocatalytic oxidation of water. Therefore, the current research is... 相似文献
2.
Saddam Saqib Wajid Zaman Fazal Ullah Imran Majeed Asma Ayaz Muhammad Farooq Hussain Munis 《应用有机金属化学》2019,33(11)
The ever‐increasing resistance of plant microbes towards fungicides and bactericides has been causing serious threat to plant production in recent years. For the development of an effective antifungal agent, we introduce a novel hydrothermal protocol for synthesis of chitosan iron oxide nanoparticles (CH‐Fe2O3 NPs) using acetate buffer of low pH 5.0 for intermolecular interaction of Fe2O3 NPs and CH. The composite structure and elemental elucidation were carried out by using X‐ray power diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray (EDX), Transmission Electron Microscopy (TEM), Fourier Transformed Infrared Spectroscopy (FTIR) and Ultraviolet Visible Absorption Spectroscopy (UV–vis spectroscopy). Additionally, antifungal activity was evaluated both In vitro and In vivo against Rhizopus oryzae which is causing fruit rot disease of strawberry. We compared different concentrations (0.25%, 0.50%, 075% and 1%) of CH‐Fe2O3 NPs and 50% synthetic fungicide (Matalyxal Mancozab) to figure out suitable concentration for application in the field. XRD analysis showed a high crystalline nature of the NPs with average size of 52 nanometer (nm). SEM images revealed spherical shape with size range of 50–70 nm, whereas, TEM also revealed spherical shape, size ranging from 0 nm to 80 nm. EDX and FTIR results revealed presence of CH on surface of Fe2O3 NPs. The band gap measurement showed peak 317–318 nm for bare Fe2O3 NPs and CH‐Fe2O3 NPs respectively. Antifungal activity in both In vitro and In vivo significantly increased with increase in concentration. The overall results revealed high synergetic antifungal potential of organometallic CH‐Fe2O3 NPs against Rhizopus oryzae and suggest the use of CH‐Fe2O3 NPs against other Phyto‐pathological diseases due to biodegradable nature. 相似文献
3.
Enantioselective and Regiodivergent Functionalization of N‐Allylcarbamates by Mechanistically Divergent Multicatalysis 下载免费PDF全文
Dr. Edward Richmond Ismat Ullah Khan Dr. Joseph Moran 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12274-12277
A pair of mechanistically divergent multicatalytic reaction sequences has been developed consisting of nickel‐catalyzed isomerization of N‐allylcarbamates and subsequent phosphoric‐acid‐catalyzed enantioselective functionalization of the resulting intermediates. By appropriate selection of reaction partners, in situ generated imines and ene‐carbamates are mechanistically partitioned to yield opposing functionalized products. Formal α‐functionalization to give protected α‐arylamines is achieved upon enantioselective Friedel–Crafts reaction with arene nucleophiles, whereas formal β‐functionalization is achieved upon reaction with diarylimine electrophiles in an enantioselective Povarov‐[4+2] cycloaddition. 相似文献
4.
5.
Munir Ullah Khan Safir Ullah Khan Xiaohan Cao Muhammad Usman Xinchen Yue Abdul Ghaffar Muhammad Hassan Prof. Chengjian Zhang Prof. Xinghong Zhang 《化学:亚洲杂志》2023,18(1):e202201050
This study demonstrates the superiority of a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co3[Co(CN)6]2), a typical cobalt Prussian Blue Analogue (CoCo-PBA) that catalyzes the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO) to produce poly(propylene monothiocarbonate)s (PPMTC). The number-average molecular weights of the PPMTC were 66.4 to 139.4 kg/mol, with a polydispersity of 2.0–3.9. The catalyst productivity reached 1040 g polymer/g catalyst (12.0 h). The oxygen-sulfur exchange reaction (O/S ER), which would generate random thiocarbonate and carbonate units, was effectively suppressed, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to >99%. It was shown that no cyclic thiocarbonate byproduct was produced during the heterogeneous catalysis of COS/PO copolymerization using CoCo-PBA as the catalyst. The content of monothiocarbonate and ether units in the copolymer chain could be regulated by tuning the feeding amount of COS. 相似文献
6.
Jiajia Yang Yun Li Jincheng Wang Xiaoli Sun Syed Mazhar Shah Rong Cao Jiping Chen 《Analytica chimica acta》2015
Bisphenol A (BPA) imprinted sponge mesoporous silica was synthesized using a combination of semi-covalent molecular imprinting and simple self-assembly process. The molecularly imprinted sponge mesoporous silica (MISMS) material obtained was characterized by FT-IR, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption measurements. The results show that the MISMS possessed a large specific surface area (850.55 m2 g−1) and a highly interconnected 3-D porous network. As a result, the MISMS demonstrated a superior specific adsorption capacity of 169.22 μmol g−1 and fast adsorption kinetics (reaching equilibrium within 3 min) for BPA. Good class selectivity for BPA and its analogues (bisphenol F, bisphenol B, bisphenol E and bisphenol AF) was also demonstrated by the sorption experiment. The MISMS as solid-phase extraction (SPE) material was then evaluated for isolation and clean-up of these bisphenols (BPs) from sediment samples. An accurate and sensitive analytical method based on the MISMS–SPE coupled with HPLC–DAD has been successfully established for simultaneous determination of five BPs in river sediments with detection limits of 0.43–0.71 ng g−1 dry weight (dw). The recoveries of BPs for lyophilizated sediment samples at two spiking levels (50 and 500 ng g−1 dw for each BP) were in the range of 75.5–105.5% with RSD values below 7.5%. 相似文献
7.
Ullah Malik Zaka Muhammad Taseer Mallawi Fouad 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2411-2418
Journal of Thermal Analysis and Calorimetry - This paper provides a theoretical study of 3D nanofluid flow with zero nanoparticles mass and constant heat fluxes conditions. An incompressible... 相似文献
8.
Michael Coto Giorgio Divitini Avishek Dey Satheesh Krishnamurthy Najeeb Ullah Cate Ducati R. Vasant Kumar 《Materials Today Chemistry》2017
A highly efficient black TiO2-Ag photocatalytic nanocomposite, active under both UV and visible light illumination, was synthesized by decorating the surface of 25 nm TiO2 particles with Ag nanoparticles. The material was obtained via a rapid, one-pot, simple (surfactant and complexing agent free) chemical reduction method using silver nitrate and formaldehyde as a metal salt and reducing agent, respectively. The nanocomposite shows an increase of over 800% in the rate of photocatalytic methylene blue dye degradation, compared to commercial unmodified TiO2, under UV-VIS illumination. Unlike pure TiO2, the nanocomposite exhibits visible light activation, with a corresponding drop in optical reflectance from 100% to less than 10%. The photocatalytic properties were shown to be strongly enhanced by post-reduction annealing heat treatments in air, which were observed to decrease, rather than coarsen, silver particle size, and increase particle distribution. This, accompanied by a variation in the silver surface oxidation states, appear to dramatically affect the photocatalytic efficiency under both UV and visible light. This highly active photocatalyst could have wide ranging applications in water and air pollution remediation and solar fuel production. 相似文献
9.
Hammad Ullah Alessandro Di Minno Cristina Santarcangelo Haroon Khan Jianbo Xiao Carla Renata Arciola Maria Daglia 《Molecules (Basel, Switzerland)》2021,26(8)
Helicobacter pylori (H. pylori) infections affect almost half of the world’s population, with gradually increasing incidence in developed countries. Eradication of H. pylori may provide significant benefits to the affected individual by healing a number of gastrointestinal and extra-digestive disorders. But due to increased microbial resistance and lack of patient adherence to the therapy, the eradication rate of H. pylori is below 80% with current pharmacological therapies. The usage of botanicals for their therapeutic purposes and medicinal properties have been increased in last decades. They can be use as alternative H. pylori treatments, especially against drug-resistant strains. Epidemiological studies have revealed that people with lower vegetable and micronutrient intake may be at increased risk of H. pylori infection. We have undertaken a review of clinical trials to evaluate the efficacy of vegetable extracts and micronutrients in patients with H. pylori. Various databases, such as Google Scholar, PubMed, Scopus, Web of Science, and the Cochrane Library, were searched for the articles published in English. A total of 24 clinical studies (15 for vegetable extracts and 9 for micronutrients) were selected to be reviewed and summarized in this article. Vegetable extracts (Broccoli sprouts, curcumin, Burdock complex, and Nigella sativa) and micronutrients (vitamin C and E) were not found to be as effective as single agents in H. pylori eradication, rather their efficacy synergized with conventional pharmacological therapies. Conversely, GutGard was found to be significantly effective as a single agent when compared to placebo control. 相似文献