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991.
992.
针对目前PM2.5检测器检测过于复杂、成本高、精度难以保证的缺点,提出一种基于无线通信模块的户用PM2.5检测器。该检测器由室内机与室外机2部分构成,通过RF1100SE模块实现室内外的通信。室内机与室外机均采用成本极低的STC单片机作为主控芯片,工作时室外机通过光敏粉尘传感器实现对户外PM2.5的检测,并将检测数据由无线模块发送到室内的接收模块,经单片机处理后由LED液晶显示屏显示实时数据和24小时的数据变化曲线,保证人们在室内能够准确获知室外的PM2.5数值,从而为人们对户外空气质量作短时预测,进而为指导人们的出行提供了方便。 相似文献
993.
Farahiyah Mustafa Norfarariyanti Parimon Abdul Manaf Hashim Shaharin Fadzli Abd Rahman Abdul Rahim Abdul Rahman Mohd Nizam Osman 《Superlattices and Microstructures》2010
A Schottky diode was designed and fabricated on an n-AlGaAs/GaAs high electron mobility transistor (HEMT) structure for RF power detection. The processing steps used in the fabrication were the conventional steps used in standard GaAs processing. Current–voltage measurements showed that the devices had rectifying properties with a barrier height of 0.5289–0.5468 eV. The fabricated Schottky diodes detected RF signals well and their cut-off frequencies up to 20 GHz were estimated in direct injection experiments. To achieve a high cut-off frequency, a smaller Schottky contact area is required. The feasibility of direct integration with the planar dipole antenna via a coplanar waveguide transmission line without insertion of matching circuits was discussed. A higher cut-off frequency can also be achieved by reducing the length of the coplanar waveguide transmission line. These preliminary results represent a breakthrough as regards direct on-chip integration technology, towards the realization of a ubiquitous network society. 相似文献
994.
Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long‐term stability and the possibility of powering them from a battery make them suitable for hand‐held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol. 相似文献
995.
Remote control of the vent/detector split flow ratio in packed column supercritical fluid chromatography (pSFC) with flame ionization detector (FID) is demonstrated using a dual heated restrictor method. Restrictors stemming from a Tee at the separation column outlet were, respectively, fixed into an FID and a vent port, and their individual temperatures were controlled using resistively heated wires. Subsequently, both system pressure and split flow could be manipulated. For example, for applied restrictor temperatures examined up to 600°C, corresponding vent/FID split flow ratios between 2 and 7 were observed depending on the port heated. As well, column pressures around 16–23 MPa were also achievable over the same range. Conversely, isobaric altering of the split flow ratio was possible when opposing positive and negative temperature gradients were applied at the two restrictors. Under these conditions, the system pressure varied less than 1% RSD over a 10 min period. As an application, the method was used to establish stable detector operation in the analysis of n‐alkanes under pSFC‐FID conditions that initiated flame instability. Results indicate that this technique could be a relatively simple and inexpensive means of controlling system pressure and detector split flow ratios in pSFC‐FID. 相似文献
996.
Florentina Cañada-Cañada Anunciación Espinosa-Mansilla Arsenio Muñoz de la Peña Alicia Mancha de Llanos 《Analytica chimica acta》2009,648(1):113-2374
A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode. A post-column photoderivatization was carried out with an on-line photoreactor, located between a diode array detector (DAD) and a fast scanning fluorescence detector (FSFD). Neopterin (NEO), biopterin (BIO), pterin (PT) and dihydrobiopterin (BH2) were determined by measuring native fluorescence, using the photoreactor in OFF-mode, and tetrahydrobiopterin (BH4) was determined by measuring of the induced fluorescence of the generated photoproducts, using the photoreactor in ON-mode. In addition, Creatinine (CREA), as a reference of metabolites excrection in urine, was simultaneously determined using the DAD detector. Detection limits were 0.2, 13.0, 0.3, 0.3 and 3.5 ng mL−1, for NEO, BH2, BIO, PT and BH4, respectively, and 0.4 μg mL−1 for CREA. Ratio values for NEO/CREA, PT/CREA, BH4/CREA, BH2/CREA, NEO/BIO and BIOtotal/CREA, in urine samples, of healthy children and adults, phenylketonuric children and infected mononucleosis children, are reported. A comparative study, about the mean values obtained for each of the compounds, by the present procedure and by the classical iodine oxidation method (Fukushimás method), has been performed, in urine samples belonging to healthy volunteers. The values obtained were BH4/CREA: 0.41, BH2/CREA: 0.31 and BIOtotal/CREA: 0.73, by the proposed method, and BH4/CREA: 0.35, BH2/CREA: 0.20 and BIOtotal/CREA: 0.48, by iodine oxidation method. 相似文献
997.
The clinical diagnosis of skin lesions is not an easy task for dermatologists. A segmentation method that makes the extraction of important characteristics of the skin lesion image can aid dermatologists in the clinical diagnosis of skin cancer. In this paper a segmentation method that combines the use of nonlinear diffusion equations and the Canny edge detector for the automatic detection of the skin edge lesions is presented. Experimental results show the efficacy of the proposed method even when the lesion is noisy or when the lesion is covered by hairs. 相似文献
998.
“3S”技术及其在土地资源管理中的应用 总被引:10,自引:0,他引:10
“3S”技术作为当前信息管理的高新技术,在土地资源管理中具有广阔的应用前景.在介绍RS,GIS,GPS及“3S”集成的基础上,简要分析了“3S”技术在土地资源调查、土地利用规划、土地利用动态监测等方面的应用,并结合当前的热点作出了展望. 相似文献
999.
章礼华 《安庆师范学院学报(自然科学版)》2006,12(1):1-3
本文提出了利用衰减腔进行两原子纠缠态的制备方案。当两单光子探测器在探测期限内只探测到一个溢出的光子时,两个在不同腔中的原子以一定的概率处于最大纠缠态。 相似文献
1000.
In this work, portable gas chromatography-microflame ionization detection (portable GC-μFID) coupled to headspace solid-phase microextraction (HS-SPME) was developed for the field analysis of benzene, toluene, ethylbenzene and xylene (BTEX) in water samples. The HS-SPME parameters such as fiber coating, extraction times, stirring rate, the ratio of headspace volume to sample volume, and sodium chloride concentration were studied. A 65 μm poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) SPME fiber, 900 rpm, 3.0 ml of headspace (1.0 ml water sample in 4.0 ml vial), and 35% sodium chloride concentration (w/v) were respectively chosen for the best extraction response. An extraction time of 1.0 min was enough to extract BTEX in water samples. The relative standard deviation (R.S.D.) for the procedure varied from 5.4% to 8.3%. The method detection limits (MDLs) found were lower than 1.5 μg/l, which was enough sensitive to detect the BTEX in water samples. The optimized method was applied to the field analysis of BTEX in wastewater samples. These experiment results show that portable GC-μFID combined with HS-SPME is a rapid, simple and effective tool for field analysis of BTEX in water samples. 相似文献