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1.
Cr-SBA-16 mesoporous silica heterogeneous catalysts (Si/Cr = 7, 14, and 28) were successfully synthesized by one-pot hydrothermal method at low acidic medium. The catalysts were characterized by means of X-ray diffraction (XRD), N2 adsorption-desorption at 77 K, Fourier Transform Infrared (FTIR), X-ray photoelectron (XPS) and Diffuse Reflectance UV–Vis (DRS) Spectroscopies, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. Herein, Cr-SBA-16 catalysts are evaluated in the selective catalytic oxidation of benzyl alcohol derivatives using H2O2 as oxidant. From XPS and UV–Vis (DRS) spectroscopies the molar ratios between Cr6+/Cr3+ are found to increase versus chromium loading in the following order: Cr-SBA-16(28) < Cr-SBA-16(14) < Cr-SBA-16(7). Hence the highest Cr6+ in tetrahedrally environment is observed for Si/Cr = 7. We demonstrated for the first time that the selective catalytic oxidation of benzyl alcohol (BzOH) using H2O2 over Cr-SBA-16 occurs through noncompetitive adsorption mechanism and the reaction is pseudo-first order to BzOH. The activity of the reaction depends on the symmetry of chromium species, herein, high activity is observed for tetrahedral chromium species in Cr-SBA-16(7). The absence of any chromium ions in the filtrate shows no chromium leaching from the silica framework.  相似文献   
2.
Radiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X-ray-irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer-based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H3PW12O40 (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H3PW12O40 films were prepared by solution casting and their optical responses toward 60Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation-induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H3PW12O40 films have a long shelf life, are dose-rate independent within a wide range, and color-stable after irradiation. All these features make the nanocomposite PVA/H3PW12O40 films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes.  相似文献   
3.
Pt0被认为是NO氧化的活性物种,而催化剂的制备方法对活性物种的含量起着决定性作用。本文采用非惰性气氛保护的改性醇还原-浸渍法(MARI)合成了高分散高Pt0含量的1% (w, 质量分数) Pt/SiO2-Al2O3催化剂(MA-Pt/SA)。X射线粉末衍射(XRD)、CO-漫反射傅里叶变换红外吸收光谱(CO-DRIFTS)和透射电镜(TEM)表征证实在550 ℃焙烧3 h后催化剂的Pt颗粒仅有3.8 nm。同时,X射线光电子能谱(XPS)和H2-程序升温还原(H2-TPR)结果表明催化剂具有高Pt0含量(60.3%)。模拟柴油车尾气气氛进行活性测试,并与传统浸渍法制备的1% (w) Pt/SiO2-Al2O3催化剂(C-Pt/SA)对比,结果显示MA-Pt/SA具有优异的催化氧化性能,其NO最大转化率高达74%,比C-Pt/SA的NO转化率高了23%。经670 ℃高温老化15 h后,老化的MA-Pt/SA的NO转化率仍然高达69%。此外NO + O2共吸附原位漫反射傅里叶变换红外吸收光谱(in situ DRIFTS of NO + O2 co-adsorption)表明高的Pt分散度和高Pt0含量能够促进中间物种桥式硝酸盐的生成及分解,进而导致了优异的NO氧化活性。最后,利用同样方法将Pt的负载量降低至0.5% (w)制备催化剂,NO转化率仍达64%。这种制备方法能够获得低贵金属高性能的Pt基催化剂。  相似文献   
4.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.  相似文献   
5.
人教版初中化学首个探究性实验"蜡烛及其燃烧"明确指出火焰的划分方法,但在实际教学中肉眼观察法和火柴梗燃烧法对蜡烛火焰的划分存在一定的局限性。采用文献研究法和实验验证法分析其局限性的成因——燃料的析炭能力强弱、材料结构的不同等,并提出相应的改进建议。  相似文献   
6.
A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.  相似文献   
7.
The reaction of easily available Morita–Baylis–Hillman (MBH) alcohols with AgSCF3 in the presence of n-Bu4NI and KI affords primary allylic SCF3 products in high yields and excellent regioselectivities. This regioselective dehydroxytrifluoromethylthiolation protocol could also be extended to propargylic alcohols for the preparation of the primary propargylic SCF3 products.  相似文献   
8.
采用溶液浸渍法制备了聚乙烯醇(PVA)均匀包覆的石墨并研究了其微观形貌及电化学性能. 以LiNi0.8Co0.15Al0.05O2(NCA)为正极材料、 PVA包覆石墨为负极材料组装成软包电池和钢壳电池, 研究了PVA功能保护膜对全电池的电化学性能和存储寿命的影响. 结果表明, 存储过程中PVA功能保护膜可以有效抑制电解液和石墨内嵌锂反应的发生, 延长电池的存储寿命.  相似文献   
9.
In this study, we present a versatile and easy procedure for modifying a cobalt ferrite nanoparticle step by step. A new nanocatalyst was prepared via CuII immobilized onto CoFe2O4@HT@Imine. The catalyst was fully characterized by Fourier‐transform infrared (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), and vibrating sample magnetometer (VSM) analyses. The current procedure as a green protocol offers benefits including a simple operational method, an excellent yield of products, mild reaction conditions, minimum chemical wastes, and short reaction times. Without any significant reduction in the catalytic performance, up to five recyclability cycles of the catalyst were obtained. The optimization results suggest that the best condition in the oxidation of benzyl alcohol derivatives is 0.003 g of the CoFe2O4@HT@Imine‐CuII catalyst, TEMPO, at 70°C under solvent‐free condition and air.  相似文献   
10.
When irradiated with violet light, hexaazatrinaphthylene (HATN) extracts a hydrogen atom from an alcohol forming a long-living hydrogenated species. The apparent kinetic isotope effect for fluorescence decay time in deuterated methanol (1.56) indicates that the lowest singlet excited state of the molecule is a precursor for intermolecular hydrogen transfer. The photochemical hydrogenation occurs in several alcohols (methanol, ethanol, isopropanol) but not in water. Hydrogenated HATN can be detected optically by an absorption band at 1.78 eV as well as with EPR (electron paramagnetic resonance) and NMR techniques. Mass spectrometry of photoproducts reveal di-hydrogenated HATN structures along with methoxylated and methylated HATN molecules which are generated through the reaction with methoxy radicals (remnants from alcohol splitting). Experimental findings are consistent with the theoretical results which predicted that for the excited state of the HATN-solvent molecular complex, there exists a barrierless hydrogen transfer from methanol but a small barrier for the similar oxidation of water.  相似文献   
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