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961.
962.
Liangce Rong Shan Yin Sheng Xia Shimin Tao Yanhui Shi Shujiang Tu 《Research on Chemical Intermediates》2012,38(3-5):983-994
One-pot, multicomponent reaction for the synthesis of 4-aryl-5-cyano-1,6-dihydro-2-thiouracils via three-component from aromatic aldehydes, ethyl 2-cyanoacetate and S-benzylisothiourea hydrochloride (methyl carbamimidothioate sulfate) under methanol is described. These compounds have many drug activities, such as anti-hepatitis C viral, anti-Severe acute respiratory syndrome and anti-HIV-1 integrese activity. The advantages of this procedure include the short reaction time, mild reaction conditions and excellent yields. 相似文献
963.
Xubiao Luo Yining Huang Fang Deng Shenglian Luo Youcai Zhan Hongying Shu Xinman Tu 《Mikrochimica acta》2012,179(3-4):283-289
We have developed a convenient, selective and reliable method for the rapid enrichment of trace quantities of Cu(II) by using a magnetic Cu(II) ion-imprinted polymer. This is followed by their determination by FAAS. The imprints were prepared by using (a) Cu(II) ions as the template, (b) 3-aminopropyltriethoxysilane as both the functional monomer and the crosslinking agent, and (c) Fe3O4 as the magnetic component. Enrichment is carried out in a single step, and adsorbed copper ions can be separated from the sample solution by applying a strong magnet. The effects of pH, elution condition, amount of imprint, and of potentially interfering ions were evaluated. Under the optimal conditions, the detection limit and enrichment factor are 0.3?μg L?1 and 100, respectively, and the recovery is >95?%. The procedure was successfully applied in the enrichment and detection of trace copper ions in environmental water. Figure
General procedure for preconcentration/recovery of Cu (II) ions 相似文献
964.
In-situ transmission electron microscopy in combination with a heating stage has been employed to real-time monitor variations of -phase MnO2 nanoflowers in terms of their morphology and crystalline structures upon thermal annealing at elevated temperatures up to ~665℃. High-temperature annealing drives the diffusion of the small δ-MnO2 nanocrystallites within short distances less than 15 nm and the fusion of the adjacent δ-MnO2 nanocrystallites, leading to the formation of larger crystalline domains including highly crystalline nanorods. The annealed nanoflowers remain their overall flower-like morphology while they are converted to δ-MnO2 . The preferred transformation of the δ-MnO2 to the δ-MnO2 can be ascribed to the close lattice spacing of most crystalline lattices between δ-MnO2 and δ-MnO2 , that might lead to a possible epitaxial growth of δ-MnO2 lattices on the δ-MnO2 lattices during the thermal annealing process. 相似文献
965.
966.
Hongying Zhu Yonggang Feng Jun Yang Wenjie Pan Zhanghai Li Yonggao Tu Xiaolan Zhu Guangming Huang 《Journal of separation science》2013,36(15):2486-2495
Sucrose esters (SEs) were successfully extracted from Oriental tobacco leaves using a new methodology based on accelerated solvent extraction followed by hydrophilic–lipophilic balanced cartridge cleanup step. The SEs were detected by HPLC with ion‐trap MS detection using an electrospray interface operated in the positive ion mode. This methodology combines the high efficiency of extraction provided by a pressurized fluid and the highly sensitive characterization offered by ion‐trap MS. Under the optimized conditions, 14 SEs were first identified among a total of 23 SEs found in Oriental tobacco leaves. Under the same conditions, only four new SEs were extracted by using traditional ultrasound‐assisted extraction and liquid–solid extraction methods. The present method might be potentially useful in high‐efficiency extraction and sensitive characterization of SEs from complex matrices such as tobacco leaves. 相似文献
967.
Yu-Ying Chao Yi-Ming Tu Zhi-Xuan Jian Hsaio-Wen Wang Yeou-Lih Huang 《Journal of chromatography. A》2013,1271(1):41-49
In this study we on-line coupled hollow fiber liquid–liquid–liquid microextraction (HF-LLLME), assisted by an ultrasonic probe, with high-performance liquid chromatography (HPLC). In this approach, the target analytes – 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 2,6-dichlorophenol (2,6-DCP), and 3,4-dichlorophenol (3,4-DCP) – were extracted into a hollow fiber (HF) supported liquid membrane (SLM) and then back-extracted into the acceptor solution in the lumen of the HF. Next, the acceptor solution was withdrawn on-line into the HPLC sample loop connected to the HF and then injected directly into the HPLC system for analysis. We found that the chlorophenols (CPs) could diffuse quickly through two sequential extraction interfaces – the donor phase – SLM and the SLM – acceptor phase – under the assistance of an ultrasonic probe. Ultrasonication provided effective mixing of the extracted boundary layers with the bulk of the sample and it increased the driving forces for mass transfer, thereby enhancing the extraction kinetics and leading to rapid enrichment of the target analytes. We studied the effects of various parameters on the extraction efficiency, viz. the nature of the SLM and acceptor phase, the compositions of the donor and acceptor phases, the fiber length, the stirring rate, the ion strength, the sample temperature, the sonication conditions, and the perfusion flow rate. This on-line extraction method exhibited linearity (r2 ≥ 0.998), sensitivity (limits of detection: 0.03–0.05 μg L−1), and precision (RSD% ≤ 4.8), allowing the sensitive, simple, and rapid determination of CPs in aqueous solutions and water samples with a sampling time of just 2 min. 相似文献
968.
A series of 2-amino-6-(2-oxo-2H-chromen-3-yl)-4-pyridine-3-carbo-nitriles were synthesized by the one-pot, multicomponent reaction of 3-acetyl-coumarin, aromatic aldehydes, malononitrile, and ammonium acetate in acetic acid under microwave irradiation. The reactions were completed in 10–13 min with 61–86% yields, were environmental benign, and had easy workup. Their structures were confirmed by 1H NMR, IR, and MS spectra and elemental analysis. 相似文献
969.
970.
亚甲蓝作为酶电极电子传递介体的性能研究 总被引:1,自引:0,他引:1
研究了亚甲蓝修饰的玻碳电极的催化性能,并以此电极为基础电极研制了介体修饰型多酚氧化酶电极,对多巴胺测定的检出限为5×10-6mol/L,较空白电极降低了400倍,而对维生素C的响应则显著减小,其电流值降低至空白电极的十分之一.因此不仅显著提高了灵敏度,选择性也得到很大的改善. 相似文献