全文获取类型
收费全文 | 1335篇 |
免费 | 42篇 |
国内免费 | 10篇 |
专业分类
化学 | 896篇 |
晶体学 | 28篇 |
力学 | 35篇 |
综合类 | 1篇 |
数学 | 57篇 |
物理学 | 370篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 91篇 |
2021年 | 74篇 |
2020年 | 46篇 |
2019年 | 49篇 |
2018年 | 34篇 |
2017年 | 38篇 |
2016年 | 57篇 |
2015年 | 38篇 |
2014年 | 50篇 |
2013年 | 82篇 |
2012年 | 95篇 |
2011年 | 94篇 |
2010年 | 56篇 |
2009年 | 52篇 |
2008年 | 54篇 |
2007年 | 65篇 |
2006年 | 48篇 |
2005年 | 39篇 |
2004年 | 41篇 |
2003年 | 31篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1962年 | 3篇 |
排序方式: 共有1387条查询结果,搜索用时 15 毫秒
61.
Tauqeer Ahmad Yasir Ayesha Khan Milan Skalicky Allah Wasaya Muhammad Ishaq Asif Rehmani Naeem Sarwar Khuram Mubeen Mudassir Aziz Mohamed M. Hassan Fahmy A. S. Hassan Muhammad Aamir Iqbal Marian Brestic Mohammad Sohidul Islam Subhan Danish Ayman EL Sabagh 《Molecules (Basel, Switzerland)》2021,26(9)
Soil salinity disrupts the physiological and biochemical processes of crop plants and ultimately leads to compromising future food security. Sodium nitroprusside (SNP), a contributor to nitric oxide (NO), holds the potential to alleviate abiotic stress effects and boost tolerance in plants, whereas less information is available on its role in salt-stressed lentils. We examined the effect of exogenously applied SNP on salt-stressed lentil plants by monitoring plant growth and yield-related attributes, biochemistry of enzymes (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) amassing of leaf malondialdehyde (MDA) and hydrogen peroxide (H2O2). Salinity stress was induced by NaCl application at concentrations of 50 mM (moderate salinity) and 100 mM (severe salinity), while it was alleviated by SNP application at concentrations of 50 µM and 100 µM. Salinity stress severely inhibited the length of roots and shoots, the relative water content, and the chlorophyll content of the leaves, the number of branches, pods, seeds, seed yield, and biomass per plant. In addition, MDA, H2O2 as well as SOD, CAT, and POD activities were increased with increasing salinity levels. Plants supplemented with SNP (100 µM) showed a significant improvement in the growth- and yield-contributing parameters, especially in plants grown under moderate salinity (50 mM NaCl). Essentially, the application of 100 µM SNP remained effective to rescue lentil plants under moderate salinity by regulating plant growth and biochemical pathways. Thus, the exogenous application of SNP could be developed as a useful strategy for improving the performance of lentil plants in salinity-prone environments. 相似文献
62.
Adesola A. Adeleke Sizwe J. Zamisa Md. Shahidul Islam Kolawole Olofinsan Veronica F. Salau Chunderika Mocktar Bernard Omondi 《Molecules (Basel, Switzerland)》2021,26(5)
A series of fifteen silver (I) quinoline complexes Q1–Q15 have been synthesized and studied for their biological activities. Q1–Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1–L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO3, AgClO4 and AgCF3SO3. Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)2]NO3 Q1, [Ag(L1)2]ClO4 Q6, [Ag(L2)2]ClO4 Q7, [Ag(L2)2]CF3SO3 Q12 and [Ag(L4)2]CF3SO3 Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes′ moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC50 between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)2]ClO4 Q7 with a benzothiazole moiety and [Ag(L4)2]ClO4 Q9 with a methyl substituent had excellent cytotoxicity against HELA cells. 相似文献
63.
Nadia Al-Saedi Manjree Agarwal Shahidul Islam Yong-Lin Ren 《Molecules (Basel, Switzerland)》2021,26(8)
Australian sweet lupin, the largest legume crop grown in Western Australia, is receiving global attention from the producers of new foods. To understand the effect of protein on cheese yield, lupin milk proteins were separated from the first, second, and third filtrations by cheesecloths. However, proteins from the first and second were analyzed using two-dimensional polyacrylamide gel electrophoresis; then, the isolated proteins associated with cheese production were identified. The research also focused on identifying the optimal method of cheese production based on the coagulation process, temperature, yield, and sensory evaluation. Lupin curds from the two cultivars, Mandelup and PBA Jurien, were produced using vinegar, lemon juice, starter culture, vegetable rennet enzyme as coagulant, as well as curd generated using starter culture and vegetable rennet enzyme. Cow’s milk was used as a control. The results indicated that first-time filtration produced better extraction and higher yield of lupin proteins and cheese than the second filtration. A sensory analysis indicated that lupin cheese produced from PBA Jurien lupin milk using vinegar, 7.80% expressed as acetic acid, and ground in 45 °C water, was the most acceptable. The cheeses were examined for their protein, carbohydrates, fat, ash, and moisture contents. The concentration of protein was approximately 27.3% and 20.6%, respectively, in the cheese from PBA Jurien and Mandelup. These results suggest that lupin milk can adequately supply the proteins needed in human diets and, thus, could be used in the production of many existing products that require animal milk as an input. 相似文献
64.
A theoretical investigation at density-functional level of Li ion conduction at the interfaces in Li2O:B2O3 nanocomposites is presented. The structural disorder at the Li2O(111):B2O3(001) interface leads to reduced defect formation energies for Li vacancies and Frenkel defects compared to Li2O surfaces. The average activation energy for Li+ diffusion in the interface region is in the range of the values for Li2O. It is therefore concluded that the enhanced Li conductivity of Li2O:B2O3 nanocomposites is mainly due to the increased defect concentration. 相似文献
65.
Islam Md. Shahidul Alam Md Nur van de Ven Theo. G. M. 《Cellulose (London, England)》2021,28(14):9475-9488
Cellulose - Textile filaments were fabricated from a solution obtained from carboxymethylated cellulose dissolved in aqueous NaOH solution, by wet spinning in an acid coagulation bath. Spinning is... 相似文献
66.
Stephane Salmieri Farhana Islam Ruhul A. Khan Farah M. Hossain Haytham M. M. Ibrahim Chuanwei Miao Wadood Y. Hamad Monique Lacroix 《Cellulose (London, England)》2014,21(3):1837-1850
New bioactive nanocomposite films were prepared by compression molding method for food applications. Film matrix was composed of poly(lactic acid) containing cellulose nanocrystals (PLA-CNC). Nanocomposite films were converted to bioactive films using nisin as an antimicrobial agent by an adsorption coating method. Resulting antimicrobial films were then introduced in packages containing sliced cooked ham as a food model and stored for 14 days at 4 °C to determine their inhibiting capacity against Listeria monocytogenes and their physicochemical and structural properties. The study also focused on the nisin release from the films by using an agar diffusion bioassay. It was observed that mechanical properties such as tensile strength, tensile modulus, elongation at break and water vapor permeability values of the bioactive films were stable after 14 days of storage. Fourier transform infrared spectroscopy analysis allowed characterizing the adsorption of nisin onto PLA-CNC surface. Microbiological analysis of sliced cooked ham inoculated with L. monocytogenes (3 log CFU/g) allowed determining the potentiality of nisin as a strong antimicrobial agent in PLA-CNC-based films. Bioactive PLA-CNC-nisin films showed a significant reduction of L. monocytogenes in ham from day 1 and a total inhibition from day 3. The percentage of nisin release increased continuously from day 0 to day 14, up to 21 % at day 14. These results demonstrated the potential application of PLA-CNC-nisin films on controlling the growth of food pathogens in meat products. 相似文献
67.
Band‐Gap Manipulations of Monolayer Graphene by Phenyl Radical Adsorptions: A Density Functional Theory Study
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Phenyl radical (Ph.) adsorption on monolayer graphene sheets is used to investigate the band‐gap manipulation of graphene through density functional theory. Adsorption of a single Ph. on graphene breaks the aromatic π‐bond and generates an unpaired electron, which is delocalized to the ortho or para position. Adsorption of a second radical at the ortho or para position saturates the radical by electron pairing and results in semiconducting graphene. Adsorption of a second radical at the ortho position (ortho–ortho pairing) is found to be more favorable than adsorption at the para position (ortho–para pairing), and the ortho–ortho pairing has stronger effects on band‐gap opening compared with ortho–para pairing. Adsorption of even numbers of Ph. on graphene by ortho–ortho and ortho–para pairings, in general, increases the band gap. Our study shows promise of band‐gap manipulation in monolayer graphene by Ph. adsorption, leading to potential wider applications of graphene. 相似文献
68.
M. Al-Amin A. A. Islam M. C. Sheikh M. S. Alam E. Zangrando M. A. Alam M. T. H. Tarafder R. Miyatake 《Transition Metal Chemistry》2014,39(2):141-149
Transition metal complexes ML2 (2–6) [where M = Ni(II), Cu(II), Zn(II), Cd(II), Pd(II) and HL = allyl-2-(4-benzyloxyphenylmethylene)hydrazine carbodithioate (1)] have been prepared by the reaction of the ligand with metal ions in 2:1 molar ratio and characterized by physicochemical techniques and spectroscopic methods. The crystal structures of the free ligand and its nickel(II) complex 2 have been determined by X-ray diffractometry. The ligand exists in its thione tautomeric form both in solution and in the solid state. In complex 2, square-planar coordination of nickel(II) was achieved by two chelating ligand moieties coordinating through the azomethine nitrogen and the deprotonated thione sulphur atom. Based on the crystal structures of analogous dithiocarbazate species, a square-planar geometry was assumed for the copper(II) and palladium(II) complexes, and a tetrahedral coordination sphere for the zinc(II) and cadmium(II) derivatives. The in vitro bactericidal activity suggests that the palladium(II) complex is strongly active against two bacteria. The cadmium(II) complex is moderately cytotoxic with an LC50 value of 409 μg/ml, but less active than gallic acid, LC50 = 78 μg/ml. 相似文献
69.
Yusof Enis Nadia Md. Ishak Nurul N. M. Latif Muhammad A. M. Tahir Mohamed I. M. Sakoff Jennette A. Page Alister J. Tiekink Edward R. T. Ravoof Thahira B. S. A. 《Research on Chemical Intermediates》2020,46(4):2351-2379
Research on Chemical Intermediates - A series of tridentate ONS Schiff bases were synthesised via condensation by reacting 2,3-dihydroxybenzaldehyde with S-2-methylbenzyldithiocarbazate (S2MBDTC)... 相似文献
70.
Islam Alshamleh Nina Krause Christian Richter Nina Kurrle Hubert Serve Ulrich L. Günther Harald Schwalbe 《Angewandte Chemie (International ed. in English)》2020,59(6):2304-2308
Current metabolomics approaches utilize cellular metabolite extracts, are destructive, and require high cell numbers. We introduce here an approach that enables the monitoring of cellular metabolism at lower cell numbers by observing the consumption/production of different metabolites over several kinetic data points of up to 48 hours. Our approach does not influence cellular viability, as we optimized the cellular matrix in comparison to other materials used in a variety of in‐cell NMR spectroscopy experiments. We are able to monitor real‐time metabolism of primary patient cells, which are extremely sensitive to external stress. Measurements are set up in an interleaved manner with short acquisition times (approximately 7 minutes per sample), which allows the monitoring of up to 15 patient samples simultaneously. Further, we implemented our approach for performing tracer‐based assays. Our approach will be important not only in the metabolomics fields, but also in individualized diagnostics. 相似文献