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141.
Evaluation of the corrosion resistance of electroless Ni-P and Ni-P composite coatings by electrochemical impedance spectroscopy 总被引:4,自引:0,他引:4
J. Balaraju T. Sankara Narayanan S. Seshadri 《Journal of Solid State Electrochemistry》2001,5(5):334-338
Electroless Ni-P composite coatings have gained a good deal of popularity and acceptance in recent years as they provide
considerable improvement of desirable qualities such as hardness, wear, abrasion resistance, etc. The disagreement among researchers
on the corrosion behaviour of these coatings warrants a thorough investigation. Among the various techniques available for
the determination of corrosion resistance, electrochemical impedance spectroscopy (EIS) is considered to be superior as it
provides not only an assessment of the corrosion resistance of different deposits but also enables the mechanistic pathway
by which the deposits become corroded to be determined. The present investigation focuses on the evaluation of the corrosion
resistance of electroless Ni-P and Ni-P-Si3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings produced using an acidic hypophosphite-reduced electroless nickel bath, using EIS. The study makes evident
that the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area
in each case. The charge transfer resistance of electroless Ni-P and Ni-P composite deposits are in the range 32,253–90,700 Ω cm2, whereas the capacitances of these coatings are in the range 11–17 μF/cm2. The improved corrosion resistance obtained for electroless Ni-P and Ni-P composite coatings is due to the enrichment of
phosphorus on the electrode surface, which enables the preferential hydrolysis of phosphorus over that of nickel. The better
corrosion resistance obtained for electroless Ni-P composite coatings can be ascribed to the decrease in the effective metallic
area prone to corrosion. Among the three electroless Ni-P composite coatings, the corrosion resistance is in the following
order: Ni-P-CeO2=Ni-P-Si3N4>Ni-P-TiO2.
Electronic Publication 相似文献
142.
Intense exoemission near phase transitions of epitaxial films of the La0.16Sr0.84MnO3 and La0.35Pr0.35Sr0.3MnO3, manganites, which exhibit the colossal magnetic resistance (CMR), is detected in a wide temperature range from 278 to 623 K including the Curie temperature. The role of the absorbed and lattice oxygen in the exoemission and CMR phenomena is discussed. The aftereffect of the magnetic field directed along the film plane on the intensity of photostimulated exoemission is discussed. 相似文献
143.
Ni-P-Zn3(PO4)2(ZnSnO3、ZnSiO3)纳米复合化学镀层性质和组成的研究 总被引:10,自引:0,他引:10
研究了温度、时间、浓度等对A3钢片上Ni-P-Zn3(PO4)2、Ni-P-ZnSnO3和Ni-P-ZiSiO3纳米复合合化学镀层外貌的影响,用扫描电子显微镜(SEM)观察外貌、称重法测定厚度;通过10%NaCl溶液、1%H2S气体加速腐蚀试验,10%CuSO4溶液点滴试验等多种手段测定其耐腐蚀性能,用X-射线光电子谱(XPS)及俄歇电子能谱(SES)测定其价态组成,结果表明:在最佳施镀条件下,可得光亮、致密、耐腐蚀性强于A3钢、磷化膜及Ni-P镀层的纳米复合化学镀层,镀层的原子百分组成约为(%):Ni-P-Zn3(PO4)2:Ni70.00,P12.47,Zn3(PO4)213.93,C3.6;Ni-P-ZnSnO3;Ni77.56,P10.00,ZnSnO39.84,C2.6;Ni-P-NiSiO3,Ni83.00,P10.96,ZnSi5.15,C0.89. 相似文献
144.
Hybrid organic/inorganic nanocomposites based on manganese oxide nanoparticles enriched pyrogallol-formaldehyde matrix (PF/MnO) were synthesized by sol-gel technique. After a drying step, the samples were heated during 2 h at different pyrolysis temperatures between 600 and 1000 °C in tubular furnace under open nitrogen atmosphere. The obtained nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrical technics in the measurement temperature range between 80 and 300 K. The XRD spectra show that PF/MnO nanocomposites are crystallized with the appearance of different phases: the graphite (C), the manganese oxide (MnO), the metallic manganese (Mn) and the manganese dioxide (MnO2) with proportions depending on pyrolysis temperature. The measurement temperature dependence conductivity can be explained by Godet-Variable Range Hopping (3D-GVRH) conduction model in all samples with the presence of an exponential distribution of localized states. The voltage-current V(I) characteristics show the presence of negative differential resistance (NDR) in some samples. The ac conductance exhibits the dominance of hopping conduction mechanism and the Small Polaron Hopping (SPH) model. The Nyquist plots for the PF/MnO-650 °C nanocomposite obey at Cole-Cole model. The impedance spectra were fitted by an equivalent circuit involving two contributions attributed to grains and grain boundaries. 相似文献
145.
《Biomedical chromatography : BMC》2018,32(6)
Extensive use and misuse of antibiotics over the past 50 years has contributed to the emergence and spread of antibiotic‐resistant bacterial strains, rendering them as a global health concern. To address this issue, a dynamic in vitro hollow‐fiber system, which mimics the in vivo environment more closely than the static model, was used to study the emergence of bacterial resistance of Escherichia coli against fosfomycin (FOS). To aid in this endeavor we developed and validated a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) assay for quantitative analysis of FOS in lysogeny broth. FOS was resolved on a Kinetex HILIC (2.1 × 50 mm, 2.6 μm) column with 2 mm ammonium acetate (pH 4.76) and acetonitrile as mobile phase within 3 min. Multiple reaction monitoring was used to acquire data on a triple quadrupole mass spectrometer. The assay was linear from 1 to 1000 μg/mL. Inter‐ and intra‐assay precision and accuracy were <15% and between ±85 and 115% respectively. No significant matrix effect was observed when corrected with the internal standard. FOS was stable for up to 24 h at room temperature, up to three freeze–thaw cycles and up to 24 h when stored at 4°C in the autosampler. In vitro experimental data were similar to the simulated plasma pharmacokinetic data, further confirming the appropriateness of the experimental design to quantitate antibiotics and study occurrence of antimicrobial resistance in real time. The validated LC‐MS/MS assays for quantitative determination of FOS in lysogeny broth will help antimicrobial drug resistance studies. 相似文献
146.
147.
钙钛矿材料在催化领域具有广泛的应用,其微观结构的调控对催化性能有显著的影响.我们采用柠檬酸配合法、溶胶凝胶法、燃烧法和浸渍法一系列不同的制备过程对镍基钙钛矿材料的结构进行调控,并将其应用于甲烷干重整反应,研究了制备方法对活性组分Ni的化学形态、Ni与基底的相互作用以及活性氧物种的调控,进而影响其催化活性和抗积碳能力.结果表明,燃烧法可以显著提高催化剂的结晶度,从而提高Ni与基底的相互作用以及表面氧物种的含量,使其具有较强的抗积碳能力.燃烧法合成的Ni基钙钛矿催化剂在CH4∶CO2=1.25∶1,800℃的条件下反应300 h后,积碳量仅为1.0%,而在同样条件下浸渍法合成的催化剂积碳量则高达14.6%. 相似文献
148.
Fei Ding Quanbing Mou Yuan Ma Gaifang Pan Yuanyuan Guo Prof. Gangsheng Tong Prof. Chung Hang Jonathan Choi Prof. Xinyuan Zhu Prof. Chuan Zhang 《Angewandte Chemie (International ed. in English)》2018,57(12):3064-3068
Functional siRNAs are employed as cross‐linkers to direct the self‐assembly of DNA‐grafted polycaprolactone (DNA‐g‐PCL) brushes to form spherical and nanosized hydrogels via nucleic acid hybridization in which small interfering RNAs (siRNAs) are fully embedded and protected for systemic delivery. Owing to the existence of multivalent mutual crosslinking events inside, the crosslinked nanogels with tunable size exhibit not only good thermostability, but also remarkable physiological stability that can resist the enzymatic degradation. As a novel siRNA delivery system with spherical nucleic acid (SNA) architecture, the crosslinked nanogels can assist the delivery of siRNAs into different cells without any transfection agents and achieve the gene silencing effectively both in vitro and in vivo, through which a significant inhibition of tumor growth is realized in the anticancer treatment. 相似文献
149.
Vinyl Sulfonate Esters: Efficient Chain Transfer Agents for the 3D Printing of Tough Photopolymers without Retardation 下载免费PDF全文
Dr. Konstanze Seidler Dr. Markus Griesser Markus Kury Dr. Reghunathan Harikrishna Dr. Peter Dorfinger Dr. Thomas Koch Anastasiya Svirkova Prof. Martina Marchetti‐Deschmann Prof. Juergen Stampfl Prof. Norbert Moszner Dr. Christian Gorsche Prof. Robert Liska 《Angewandte Chemie (International ed. in English)》2018,57(29):9165-9169
The formation of networks through light‐initiated radical polymerization allows little freedom for tailored network design. The resulting inhomogeneous network architectures and brittle material behavior of such glassy‐type networks limit the commercial application of photopolymers in 3D printing, biomedicine, and microelectronics. An ester‐activated vinyl sulfonate ester (EVS) is presented for the rapid formation of tailored methacrylate‐based networks. The chain transfer step induced by EVS reduces the kinetic chain length of the photopolymer, thus shifting the gel point to higher conversion, which results in reduced shrinkage stress and higher overall conversion. The resulting, more homogeneous network is responsible for the high toughness of the material. The unique property of EVS to promote nearly retardation‐free polymerization can be attributed to the fact that after the transfer step no polymerizable double bond is formed, as is usually seen in classical chain transfer agents. Laser flash photolysis, theoretical calculations, and photoreactor studies were used to elucidate the fast chain transfer reaction and exceptional regulating ability of EVS. Final photopolymer networks exhibit improved mechanical performance making EVS an outstanding candidate for the 3D printing of tough photopolymers. 相似文献
150.
添加Cl离子对VO-WO/TiO催化剂低温NO转化率的影响 《燃料化学学报》2018,46(11):1370-1376
考察添加不同含量Cl离子对浸渍法制备的Cl-V_2O_5-WO_3/TiO_2催化剂低温NO转化率的影响。随着Cl离子质量添加量从0增加到2.5%,Cl-V_2O_5-WO_3/TiO_2催化剂NO转化率先升高后降低,结合在含有SO_2和H2O的SCR实验结果,确定1.5%Cl-V_2O_5-WO_3/TiO_2为性能最优催化剂。在反应温度为149-362℃,NO转化率大于95%;在145-385℃,NO转化率大于90%。采用XRF、BET、XRD、TG、FT-IR和H2-TPR等方法表征了催化剂的物理化学性能和结构。结果表明,在反应气氛中加入SO_2和H2O后,催化剂比表面积和孔容均减小,副反应产物含有NH+4和SO_2-4。适量Cl离子可以抑制硫物种沉积,减少副反应产物生成,增强催化剂抗中毒能力。 相似文献