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951.
952.
953.
利用柠檬酸三钠还原硝酸银制备了银纳米颗粒(AgNPs),然后通过氨水水解正硅酸乙酯(TEOS)的方法,在AgNPs上沉积SiO2,制备出以Ag为核,SiO2为壳的复合纳米颗粒(Ag@SiO2).调节TEOS用量,可以控制SiO2层的厚度.根据AgNPs的局域表面等离激元共振(LSPR)效应,将制得的Ag@SiO2颗粒用于H2O2的检测,检测下限为1μmol/L,并可以通过控制SiO2层的厚度方便地调节Ag@SiO2颗粒与H2O2反应的速率.与传统方法相比,具有简单、快速、成本低的优点.分别运用TEM、紫外-可见分光光度计对反应前后Ag@SiO2颗粒形貌及反应过程中其LSPR吸收的变化进行了表征. 相似文献
954.
Mycophenolic acid (MPA) is an immunosuppressant drug which powerfully inhibits lymphocyte proliferation. Since the early 1990s it has been used to prevent rejection in organ transplantation. The requirement of therapeutic drug monitoring shown in previous studies raises the necessity of acquiring accurate and sensitive methods to measure MPA and its major metabolite mycophenolic acid glucuronide (MPAG).The authors developed a sample cleanup-free, rapid, and highly specific method for simultaneous measurement of MPA and MPAG in human plasma and serum using the novel technology of ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry. MPA- and MPAG-determinations were performed during a 2.0-min run time. Multiple calibration curves for the analysis of MPA and MPAG exhibited consistent linearity and reproducibility in the range of 0.05-100 (r > 0.999) mg L−1 and 4-4000 mg L−1 (r > 0.999), respectively. Limits of Detection were 0.014 mg L−1 for MPA and 1.85 mg L−1 for MPAG. Lower Limits of Quantification were 0.05 mg L−1 for MPA and 2.30 mg L−1 for MPAG. Interassay imprecision was <10% for both substances. Mean recovery was 103.6% (range 78.1-129.7%) for MPA and 111.1% (range 73.0-139.6%) for MPAG. Agreement was good for MPA and MPAG between the presented method and a validated HPLC-MS/MS method. The Passing-Bablok regression line for MPA and MPAG was HPLC-MS/MS = 1.14 UPLC-MS/MS—0.14 [mg L−1], r = 0.96, and HPLC-MS/MS = 0.77 UPLC-MS/MS + 0.50 [mg L−1], r = 0.97, respectively. This sample cleanup-free and robust LC-MS/MS assay facilitates the rapid, accurate and simultaneous determination of MPA and MPAG in human body fluids. 相似文献
955.
Natalia Campillo 《Talanta》2010,80(5):1856-1861
A method based on solid-phase microextraction (SPME) followed by gas chromatography with microwave-induced plasma atomic emission detection for determining dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) in milk and milk by-products is proposed. Parameters affecting the SPME, such as sample volume or mass, ionic strength, adsorption and desorption times and temperatures were optimized in the headspace mode. The matrix effect was evaluated for the different samples studied, concluding that standard additions calibration was required for quantification purposes. The detection limits ranged from 70 to 110 pg mL−1 for DMSe and from 80 to 400 pg mL−1 for DMDSe, depending on the sample under analysis. None of the twenty-three samples analyzed contained the studied compounds at concentrations above the corresponding detection limits. 相似文献
956.
Yuan-Na Li Xiang-Dong Qing Quan Li Shu-Fang Li Hai-Yan Fu Yong-Jie Yu Ru-Qin Yu 《Analytica chimica acta》2010,678(1):26-33
A novel application of second-order calibration method based on an alternating penalty trilinear decomposition (APTLD) algorithm is presented to treat the data from high performance liquid chromatography-diode array detection (HPLC-DAD). The method makes it possible to accurately and reliably analyze atrazine (ATR), ametryn (AME) and prometryne (PRO) contents in soil, river sediment and wastewater samples. Satisfactory results are obtained although the elution and spectral profiles of the analytes are heavily overlapped with the background in environmental samples. The obtained average recoveries for ATR, AME and PRO are 99.7 ± 1.5, 98.4 ± 4.7 and 97.0 ± 4.4% in soil samples, 100.1 ± 3.2, 100.7 ± 3.4 and 96.4 ± 3.8% in river sediment samples, and 100.1 ± 3.5, 101.8 ± 4.2 and 101.4 ± 3.6% in wastewater samples, respectively. Furthermore, the accuracy and precision of the proposed method are evaluated with the elliptical joint confidence region (EJCR) test. It lights a new avenue to determine quantitatively herbicides in environmental samples with a simple pretreatment procedure and provides the scientific basis for an improved environment management through a better understanding of the wastewater-soil-river sediment system as a whole. 相似文献
957.
Ying-Yong Zhao Xian-Long Cheng Rui-Chao Lin Yongmin Zhang Xiao-Li Sun 《Analytica chimica acta》2010,675(2):199-1953
Ergosta-4,6,8(14),22-tetraen-3-one (ergone) from many medicinal plants has been demonstrated to possess a variety of pharmacological activities in vivo and in vitro, including cytotoxic, diuretic and immunosuppressive activity. Metabolism and pharmacokinetic studies on rat were conducted for ergone. Rapid resolution liquid chromatography with atmospheric pressure chemical ionization tandem multi-stage mass spectrometry (RRLC-APCI-MSn) and high-performance liquid chromatography with fluorescence detection (HPLC-FLD) methods were applied for the identification and quantification of ergone and its metabolite from rat plasma, faeces and urine. A metabolite was identified by RRLC-DAD-APCI-MSn: 22,23-epoxy-ergosta-4,6,8(14)-triaen-3-one (epoxyergone). The concentrations of the analyte with its metabolites were determined by HPLC-FLD at excitation wavelength of 370 nm and emission wavelength of 485 nm. The samples were deproteinized with methanol after addition of camptothecin as internal standard (IS). The analysis was performed on a Diamonsil C18 column (150 mm × 4.6 mm × 5 μm) with a mobile phase gradient consisting of methanol and water at a flow rate of 1 mL min−1. The assay was linear over the concentration range of 42-1500, 36-7500 and 42-1500 ng mL−1 for plasma, faecal homogenate and urine respectively. The absolute recoveries were found to be 97.0 ± 1.2%, 98.1 ± 0.7% and 96.6 ± 1.8% for plasma, faecal homogenate and urine respectively. The intra-day and inter-day relative standard deviations (RSD) were less than 10%. The previous HPLC-MS/MS method is not affordable for most laboratories because of the specialty requirement and high equipment cost. However, the HPLC-FLD method is economic and operating simply for quantitative determination of ergone and its metabolite in rat plasma, faeces and urine. In addition, liquid chromatography coupled with ion trap multi-stage mass spectrometry is becoming a useful technique for ergone metabolite identification. 相似文献
958.
The detection of H2S was studied using several mediators in room temperature ionic liquids (RTILs) at a microelectrode. Each mediator was characterised voltammetrically, and H2S was added to observe if any mediation took place. A successful mediator was 3,5‐tert‐butyl‐obenzoquinone. Cyclic voltammetry was carried out in [C2mim][NTf2]. A reductive wave was observed and attributed to the two‐electron reduction of the mediator. No oxidative signal was observed. H2S was flowed through the system. Cyclic voltammograms showed a decrease in the reductive wave of the mediator and the onset of an oxidative signal due to the reaction between the mediator and H2S to form an adduct. This reaction is reversible and on purging the system with N2, the original reductive signal of the mediator was recovered. 相似文献
959.
Motivated by the potential of electrochemical techniques to analyze hybridization events fast and in a simple and cost‐effective way we present here a detection system allowing a parallel electrochemical DNA analysis. For this purpose different probe DNA strands have been immobilized on one electrode. By the use of two different target DNA sequences, both marked with the redox active methylene blue, we can show that hybridization with the complementary probe sh“NA strands can occur without steric hindrance. Each target has been recognized down to 3nM with a very high specificity of the sensor. In addition, we can detect two different ssDNA targets labeled with different redox active molecules, methylene blue and ferrocene, on one sensor surface simultaneously. 相似文献
960.
A sonochemical method has been successfully used to synthesize MnO2/MWNTs nanocomposites. The structure and nature of the resulting MnO2/MWNTs composite were characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray diffraction (EDX), X‐ray photoelectron spectroscopy (XPS).The results show that the sonochemically synthesized MnO2 nanoparticles were homogeneously dispersed on the modified MWNT surfaces. The performance of the MnO2/MWNTs nanocomposites modified electrode was characterized using cyclic voltammetry (CV) and Nyquist plots. The electrode exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. This may be attributed to the small particle size, high dispersion of MnO2 particles. The fabricated hydrazine sensor showed a wide linear range of 5.0×10?7–1.0×10?3 M with a response time less than 5 s and a detection limit of 0.2 μM. Taking the advantage of the unique properties of both MWNTs and MnO2, it would greatly broaden the applications of MWNTs and MnO2. 相似文献