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排序方式: 共有392条查询结果,搜索用时 15 毫秒
21.
We report a novel post‐growth microwave treatment approach to selectively modify the surface morphologies of gold (Au) films coated on the polystyrene (PS) bead substrates for effectively improving the surface‐enhanced Raman scattering (SERS) effect on the analytes. The discrete dipole approximation (DDA) model was introduced to evaluate the enhancement effects by calculating the localized electromagnetic field distribution and extinction efficiency based on the sizes of the trenches and voids, and the surface roughness of the modified Au–PS bead substrates. The SERS performance of microwave‐modified Au–PS substrates on rhodamine 6G (Rh 6G) and saliva yields at least 10‐fold improvements in SERS intensities compared to the as‐grown substrates, which is also in agreement with theoretical predictions by DDA modeling. This work demonstrates both experimentally and theoretically the efficacy of the microwave heating treatment on modifying the Au–PS bead substrates for the realization of high SERS performance in biomedical applications. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
22.
A total of ten ancient colored glass beads were analyzed by confocal Raman microspectroscopy for the non‐destructive identification of microcrystals within them. These beads were excavated from different regions of China, including Xinjiang, Henan, Hubei and Guangxi Provinces, and were dated mainly from the 10th century BC to the 9th century AD. For the first time, either tin or antimony‐based opacifiers/colorants including calcium antimonate (CaSb2O6, Ca2Sb2O7), bindheimite (Pb2Sb2O7), lead tin yellow type II (PbSn1‐xSixO3) and cassiterite (SnO2) were identified in nine samples. In addition, other crystalline phases such as cuprite (Cu2O), α‐wollastonite (CaSiO3), diopside (CaMgSi2O6), feldspar (KAlSi3O8), calcite (CaCO3) and quartz (SiO2) were also detected. Another interesting phenomenon first observed in this study was the coexistence of Sn‐ and Sb‐based opacifiers/colorants in one mosaic bead from Guangxi. The possibility to use Sb‐ and Sn‐based opacifiers/colorants for dating and provenance study of ancient glass found in China is discussed briefly. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
23.
Wanchao Hou Senlin Li Sainan Li Dongfang Shi Chunming Liu 《Journal of separation science》2019,42(6):1133-1143
Nonsteroidal anti‐inflammatory drugs reportedly reduce the risk of developing cancer. One mechanism by which they reduce carcinogenesis involves the inhibition of the activity of cyclooxygenase‐2, an enzyme that is overexpressed in various cancer tissues. Its overexpression increases cell proliferation and inhibits apoptosis. However, selected cyclooxygenase‐2 inhibitors can also act through cyclooxygenase‐independent mechanisms. In this study, using ultrafiltration, enzyme‐immobilized magnetic beads, high‐performance liquid chromatography, and electrospray‐ionization mass spectrometry, several isoflavonoids in Trifolium pratense L. extracts were screened and identified. Semi‐preparative high‐performance liquid chromatography and high‐speed counter‐current chromatography were then applied to separate the active constituents. Using these methods, seven major compounds were identified in Trifolium pratense L. As cyclooxygenase‐2 inhibitors: rothindin, ononin, daidzein, trifoside, pseudobaptigenin, formononetin, and biochanin A, which were then isolated with >92% purity. This is the first report of the presence of potent cyclooxygenase‐2 inhibitors in Trifolium pratense L. extracts. The results of this study demonstrate that the systematic isolation of bioactive components from Trifolium pratense L., by using ultrafiltration, enzyme‐immobilized magnetic beads, semi‐preparative high‐performance liquid chromatography, and high‐speed counter‐current chromatography, represents a feasible and efficient technique that could be extended for the identification and isolation of other enzyme inhibitors. 相似文献
24.
Renxing Yi Renjie Fu Dapeng Li Jin Qi Haichun Liu 《Journal of separation science》2019,42(24):3611-3620
Multidrug resistance is recognized as one of the main reasons leading to the failure of chemotherapy. Studies have shown that glutathione S‐transferase inhibitors could be regarded as multidrug resistance reversal agents. Herein, a method of applying enzyme immobilization, molecular docking, and high‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry was employed to screen glutathione S‐transferase inhibitors from natural products. Magnetic mesoporous silica microspheres were synthesized and modified with a poly(dopamine) layer, which has a large quantity of amino, enabling further non‐covalent binding with glutathione S‐transferase. Moreover, the immobilization conditions, namely, potential of hydrogen, catalase concentration, reaction temperature and reaction time, were optimized. In total, six potential compounds were isolated and identified from Perilla frutescens (L.) Britt leaves and green tea and molecular docking was applied to identify the binding site. Rosmarinic acid, (?)‐epigallocatechin‐3‐O‐gallate and (?)‐epicatechin‐3‐gallate showed higher binding affinity than the compounds, and their half maximal inhibitory concentration values were further determined. The results suggested that this proposed method was effective and convenient for identifying glutathione S‐transferase inhibitors from natural products. 相似文献
25.
Hasegawa T Iijima K Hirota K Nakajima T Makino K Terada H 《Colloids and surfaces. B, Biointerfaces》2008,63(2):209-216
A method for exact determination of phagocytic activity of alveolar macrophage (M) cells toward synthetic microspheres (MS) by optical microscopy was developed. We examined the effectiveness of the treatment of M samples with trypsin, acid or xylene to remove the polystyrene latex microspheres (PSL MS) attached to M cell membranes during their phagocytosis by M cells. We found that centrifugation, which was employed to collect M samples after incubation with MS, affected significantly the efficiency of the various treatments. Of the three treatments, xylene treatment without centrifugation was the most effective to determine the phagocytic activity of M cells, as xylene dissolved the PSL MS on the cell surface almost completely. This treatment was also effective in the case of poly(lactic-co-glycolic acid) MS (PLGA MS), which have been commonly used as an efficient vehicle for drug delivery system. 相似文献
26.
Tohru Shibata 《Macromolecular Symposia》2004,208(1):353-370
Cellulose acetate has been utilized in a variety of separation and purification processes. In membrane separation, cellulosics, in particular cellulose acetate, have played important roles. Hemodialysis and desalination are the established fields where acetate membranes have been applied. Recently, a new application, that is the purification of drinking water, is growing. The history of cellulosic membranes, preparation of acetate membranes, and applications will be reviewed. Cellulose acetate is also useful in chromatography and related separation technologies. These application will also be reviewed and the relationship between the superstructure of cellulose triacetate and its adsorptive behavior is briefly mentioned. 相似文献
27.
Amit Bansiwal Dilip Thakre Nitin Labhshetwar Siddharth Meshram Sadhana Rayalu 《Colloids and surfaces. B, Biointerfaces》2009,74(1):216-224
Highly selective material based on naturally occurring biomaterial namely chitosan has been designed for the defluoridation of water. Lanthanum incorporated chitosan beads (LCB) were prepared using precipitation method. The synthesis was optimized by varying different synthesis parameters namely lanthanum loading, complexation and precipitation time, strength of ammonia solution used for precipitation, drying time, etc. Lanthanum incorporated chitosan beads were characterized using SEM, FTIR, XRD and EDX. Surface area of LCB was observed to be 2.76 m2 g−1. The equilibrium adsorption data fitted well to Langmuir adsorption isotherm and showing maximum fluoride adsorption capacity of 4.7 mg g−1 with negligible lanthanum release. Kinetic study reveals that adsorption of fluoride is fast and follows pseudo-first-order kinetics. The effect of pH was also studied and the best efficiency was observed at pH 5. Presence of sulphate, nitrate and chloride marginally affected the removal efficiency, however drastic reduction in fluoride uptake was observed in the presence of carbonate and bicarbonate. Negative value of change in free energy (ΔG°) and positive value of change in entropy (ΔS°) suggest the adsorption of fluoride by LCB is feasible and spontaneous process. Positive value of change in enthalpy (ΔH°) suggests the process of fluoride adsorption is endothermic in nature. Regeneration study reveals that 1 M ammonium chloride solution appears to be the promising regeneration media showing 81.22% regeneration. The adsorption capacity of LCB was similar in fluoride-contaminated ground water collected from Dhar district of Madhya Pradesh, India, as compared to simulated water. 相似文献
28.
Zhenyu Wang Xiaojuan Zhang Jun Yang Zhong Yang Xiaoping Wan Ning Hu Xiaolin Zheng 《Analytica chimica acta》2013
A large number of microscale structures have been used to elaborate flowing control or complex biological and chemical reaction on microfluidic chips. However, it is still inconvenient to fabricate microstructures with different heights (or depths) on the same substrate. These kinds of microstructures can be fabricated by using the photolithography and wet-etching method step by step, but involves time-consuming design and fabrication process, as well as complicated alignment of different masters. In addition, few existing methods can be used to perform fabrication within enclosed microfluidic networks. It is also difficult to change or remove existing microstructures within these networks. In this study, a magnetic-beads-based approach is presented to build microstructures in enclosed microfluidic networks. Electromagnetic field generated by microfabricated conducting wires (coils) is used to manipulate and trap magnetic beads on the bottom surface of a microchannel. These trapped beads are accumulated to form a microscale pile with desired shape, which can adjust liquid flow, dock cells, modify surface, and do some other things as those fabricated microstructures. Once the electromagnetic field is changed, trapped beads may form new shapes or be removed by a liquid flow. Besides being used in microfabrication, this magnetic-beads-based method can be used for novel microfluidic manipulation. It has been validated by forming microscale dam structure for cell docking and modified surface for cell patterning, as well as guiding the growth of neurons. 相似文献
29.
PENG Zi-cheng LI Ping ZHOU Tai-xi LI Xue-ming Wept. of Earth Space Science Univ. of Science Tech. of China Hefei )HU Zhi-sheng 《高等学校化学研究》1992,(3)
When was the earliest glass produced in China? This has still been a question so far. Some archaeologists have thought that Yu Guo beads are real glass, the earliest glass(1100-771 B. C. ) in China. However, more details of scientific investigations in this paper show that Yu Guo beads are mainly made of clastic quartz (>95%) with a small amount of clay and sintered under the low temperature(500-600℃). It is not a glassy body, but a kind of polycrystal ornaments. 相似文献
30.