全文获取类型
收费全文 | 179篇 |
免费 | 8篇 |
专业分类
化学 | 128篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 24篇 |
物理学 | 31篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 15篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 31 毫秒
91.
Faiza Saleem Uzma Nisar Aisha Younas Faiza Jabeen Javed Iqbal Qazi Nazia Khursheed 《Natural product research》2016,30(6):720-723
In this work chitin was extracted chemically from shrimp shells. Seventeen Bacillus isolates were screened for chitinolytic activity. The chitinolytic strains of Bt. were screened at different temperatures and pHs for their hydrolytic potentials. By using a pair of specific primers, endochitinase gene was amplified from SBS Bt-5 strain through PCR, and then cloned into pTZ57 TA cloning vector and transferred in Escherichia coli DH5α strain. The sequenced gene (GenBank Accession No: HE995800) consists of 2031 nucleotides capable of encoding 676 residues. The protein consisted of three functional domains with a calculated molecular mass of 74.53 kDa and a pI value of 5.83. The amino acid sequence of chi gene showed 99% similarity to the genes of Bt MR11 endochitinase, Bt serovar kurstaki chitinase (kchi), Bt strain MR21 endochitinase and Bacillus cereus B4264. 相似文献
92.
Let R be a ring and \({\mathbb{N}}\) be the set of all non-negative integers. A family of maps \({D=\{d_n\}_{n \in\mathbb{N}}}\) is said to be Jordan triple higher derivable if \({d_n(aba)=\sum \nolimits_{p+q+r=n} d_p(a)d_q(b)d_r(a)}\) holds for all \({a,b \in R}\), where d 0 = I R , (the identity map on R). In this paper, we determine Jordan triple higher derivable map on a ring R, which contains a nontrivial idempotent which is automatically additive. An immediate application of our main result shows that every Jordan triple higher derivable map becomes higher derivation on R. 相似文献
93.
Brittany P. Rickard Marta Overchuk Girgis Obaid Mustafa Kemal Ruhi Utkan Demirci Suzanne E. Fenton Janine H. Santos David Kessel Imran Rizvi 《Photochemistry and photobiology》2023,99(2):448-468
Ovarian cancer is the most lethal gynecologic malignancy with a stubborn mortality rate of ~65%. The persistent failure of multiline chemotherapy, and significant tumor heterogeneity, has made it challenging to improve outcomes. A target of increasing interest is the mitochondrion because of its essential role in critical cellular functions, and the significance of metabolic adaptation in chemoresistance. This review describes mitochondrial processes, including metabolic reprogramming, mitochondrial transfer and mitochondrial dynamics in ovarian cancer progression and chemoresistance. The effect of malignant ascites, or excess peritoneal fluid, on mitochondrial function is discussed. The role of photodynamic therapy (PDT) in overcoming mitochondria-mediated resistance is presented. PDT, a photochemistry-based modality, involves the light-based activation of a photosensitizer leading to the production of short-lived reactive molecular species and spatiotemporally confined photodamage to nearby organelles and biological targets. The consequential effects range from subcytotoxic priming of target cells for increased sensitivity to subsequent treatments, such as chemotherapy, to direct cell killing. This review discusses how PDT-based approaches can address key limitations of current treatments. Specifically, an overview of the mechanisms by which PDT alters mitochondrial function, and a summary of preclinical advancements and clinical PDT experience in ovarian cancer are provided. 相似文献
94.
The monomers and polymers of four anionic amide type sodium undecenoxy carbonyl glycinate (SUCG) surfactants and four anionic carbamate type sodium undecenoyl glycinate (SUG) surfactants with 1-, 2-, 3-, and 4-glycine unit as head group were synthesized and characterized. The CMC and aggregation number (A) for all eight surfactants were determined using fluorescence spectroscopy. In addition, the CMC values of these surfactants were also projected by surface tension and CE. The CMC of the monomers decreases with increases in the size of glycine head groups and correlates well when the fluorescence method was compared to CE. The A number increases and partial specific volume (V) decreases with increase in size of the head group of both monomers and polymers. However, A and V are always lower for the polymers than the corresponding monomers. The electrophoretic and chromatographic parameters of micelle polymers of SUG and SUCG were also examined. The coefficient of EOF increases with the increase in size of the head group but the electrophoretic mobility decreases which results in a decrease in the elution range. The retention data suggest that the selectivity differences among the mono-, di-, and tripeptide derivatives of poly-SUCG surfactants are relatively higher compared to the derivatives of poly-SUG series. 相似文献
95.
G. H. Rizvi 《Journal of Radioanalytical and Nuclear Chemistry》1986,106(5):309-317
Tropolone reacts with uranium/VI/ and forms orange yellow precipitate extractable in chloroform. The maximum absorption occurs at 405 nm and the absorbance is found to remain constant in the pH range of 5.5 to 7.0. Beer's law is obeyed upto 37.6 ppm of U/VI/. The sensitivity of the colour reaction is 0.034 g cm–2. Most of the common ions do not interfere. The method becomes more selective by masking some of the interfering cations with EDTA. The method was applied to determine uranium in monazite sand.This work is a part of the Ph.D. Thesis. 相似文献
96.
97.
Md Murshed Bhuyan Hirotaka Okabe Yoshiki Hidaka Nirmal Chandra Dafader Nazia Rahman Kazuhiro Hara 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(4):369-376
The objective of the work is to synthesize pectin-N, N-Dimethylacrylamide (DMAA) hydrogel by gamma radiation without using any initiators and cross-linking agents. Effect of radiation doses on gel fraction and equilibrium swelling as a function of pH were studied, and 5 kGy radiation dose was found to be the optimum dose for hydrogel synthesis. The grafting /crosslinking was investigated by Fourier transform infrared spectroscopy. Thermal properties and surface morphology were studied by differential scanning calorimetry and scanning electron microscopy. To study the drug release kinetics, 5-fluorouracil was loaded into the hydrogel and in vitro release was carried out in simulated gastric and intestinal fluid. The release profile of drug showed that more than 90% of the loaded drugs were released after 4 hours at both gastric fluid and intestinal fluid pH. Drug release data was fitted into zero order, Higuchi and Korsmeyer-Peppas kinetic models. Higuchi model was found to be the best fitted and release exponent ‘n’ value of Korsmeyer-Peppas model indicated the non-Fickian transport. 相似文献
98.
The ultraviolet photochemistry of phenylacetylene and the enthalpy of formation of 1,3,5-hexatriyne. 总被引:1,自引:0,他引:1
The ultraviolet photochemistry of phenylacetylene was studied in a molecular beam at 193 nm. The only primary photofragments observed were HCCH (acetylene) and C(6)H(4). Some of the C(6)H(4) molecules were found to decompose to 1,3,5-hexatriyne and molecular hydrogen. An enthalpy of formation of DeltaH(f) < or = 160 +/- 4 kcal mol(-1) was determined for 1,3,5-hexatriyne from the energetic threshold for this process. This experimentally determined value agrees well with our ab initio calculations performed at the G2 level of theory. Angular distribution measurements for the HCCH + C(6)H(4) channel yielded an isotropic distribution and were attributed to a long-lived intermediate and ground-state dissociation. An exhaustive search yielded no evidence for the phenyl + ethynyl or the atomic hydrogen elimination channels even though these were observed in the pyrolytic studies of phenylacetylene [Hofmann, J.; Zimmermann, G.; Guthier, K.; Hebgen, P.; Homann, K. H. Liebigs Ann. 1995, 631, 1995. Guthier, K.; Hebgen, P.; Hofmann, K. H.; Zimmermann, G. Liebigs Ann. 1995, 637, 1995]. 相似文献
99.
Abdul Shakoor Tasneem Zahra Rizvi Hafiz Umer Farooq Najmul Hassan Abdul Majid Muhammad Saeed Muhammad Farooq 《Polymer Science Series A》2013,55(4):279-284
Polypyrrole is synthesized and doped with Dodecylbenzenesulphonic acid. The doped Polypyrrole with Dodecylbenzenesulphonic acid is intercalated into the layers of Montmorillonite clay successfully by in situ polymerization. The structural properties of synthesized doped Polypyrrole and intercalated doped Polypyrrole were studied by XRD analysis. The crystallinity of intercalated doped Polypyrrole into the layers of Montmorillonite clay is confirmed by means of X-rays diffraction studies, which is more than the doped Polypyrrole. Enhanced d-spacing of Montmorillonite confirmed that doped Polypyrrole is interclated into the layers of Montmorillonite clay at nanoscale. The scanning electron micrographs also confirm the formation of dual phase of platelet as well as of flaky structure of intercalated doped Polypyrrole. Temperature dependant conductivity showed three dimensional variable ranges hopping model. Activation energy, density of states and hopping length are calculated and found to be influenced by intercalating Doped Polypyrole into the layers of Montmorillonite clay. 相似文献
100.
Determination of elemental fingerprint profile of 40 commercial beer samples was performed using inductively coupled plasma–mass
spectrometry combined with principal component analysis and receiver operating characteristic (ROC) analysis. Fourteen trace
elements, 51V, 52Cr, 59Co, 60Ni, 75As, 82Se, 95Mo, 111Cd, 115In, 121Sb, 133Cs, 208Pb, 209Bi, and 238U, were monitored. All 40 beer samples are distinguishable by using the proposed method. ROC analysis showed that individual
beer samples can be correctly identified via the magnitude of its correlation coefficient with respect to the other beers
with low false positive rate. The obtained results suggested that the elemental fingerprint technique is feasible for sample
differentiation and comparison. 相似文献