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81.
Two flow injection analyses (FIA) methods for the determination of diffusion coefficients in a straight single tube FIA system were developed. Based on the analytical solution of the convection-diffusion equation, linear relationships of the logarithmic values of the dispersion coefficient (D) and the half-peak width (W1/2) with the diffusion coefficient (Dm) were obtained. Experiments were designed to verify these methods. For example, for potassium hexacyanoferrate (III) a Dm value of 0.72 × 105 cm2 s−1 was found versus a literature value of 0.76 × 105 cm2 s−1 (error, 5%). For potassium hexacyanoferrate (II) a Dm value of 0.67 × 105 cm2 s−1 was obtained versus a literature value of 0.63 × 105 cm2 s−1 (error, 6%). The diffusion coefficients of some important biomedical compounds, such as dopamine, epinephrine, norepinephrine and ascorbic acid, were then determined. The values of 105 Dm/cm2 s−1 are 0.60 ± 0.03, 0.44 ± 0.02, 0.60 ± 0.01 and 0.68 ± 0.06, respectively. 相似文献
82.
A spot test was implemented in a flow-injection system for the spectrophotometric determination of zinc in digests of plant materials. It is based on the influence of Zn2+ on the oxidation rate of 1-naphthylethylenediamine (NED) by hexacyanoferrate(III) under acidic conditions. In order to control the precipitate formation and to maintain the resulting suspension, a micellar medium was established by adding Triton X-100. The proposed system handles about 65 samples per hour, meaning 72 μg NED and 9.0 mg K3[Fe(CN)6] per determination. Baseline drift is usually <0.01 absorbance per hour and the analytical signals for 0.5-2.5 mg l−1 Zn range within ca. 0.07-0.45 absorbance. Linearity of the analytical curve is fair (r>0.999, n=6) and detection limit was estimated as 0.2 mg l−1 Zn. Results are precise (R.S.D.<1%, n=10) and in agreement with flame atomic absorption spectrometry and with certified values of standard reference materials. 相似文献
83.
Surowiec I Baena JR Frank J Laurell T Nilsson J Trojanowicz M Lendl B 《Journal of chromatography. A》2005,1080(2):132-139
A flow-through microdispenser has been coupled to a micro HPLC separation system and used as a solvent elimination interface for Fourier transform infrared (FTIR) and Raman spectroscopic detection of the separated compounds. Using the microdispenser picoliter sized droplets can be generated and deposited on an appropriate target placed on a computerized x, y-stage. Evaporation of volatile solvent and buffer is rapid and allows analysis of the obtained dry deposits by various techniques. Due to the destruction free character of Raman and FTIR spectroscopy they can be applied sequentially to interrogate the same deposit. In the reported application five phenolic acids typically present in wine have been separated on a C-18 column technique using a mixture of water, methanol and acetic acid as mobile phase. For spectrum acquisition infrared and Raman microscopes have been used. The spectra recorded from the dried deposits of the separated compounds agreed well with the reference spectra of corresponding components. 相似文献
84.
85.
A flow-injection system is described for the determination of d-mannitol. Mannitol dehydrogenase is immobilized on poly(vinyl alcohol) beads and packed in a column (5 cm × 4 mm i.d.). The NADH formed is detected fluorimetrically. The response is linear between 5 × 10?7 and 1 × 10?4 M mannitol and the detection limit is 1 × 10?7 M. The throughput is 30 samples per hour. The reactor is stable for at least 8 weeks. 相似文献
86.
流动注射分光光度法测定微量硫氰酸根 总被引:2,自引:0,他引:2
基于3,5-Br2-PADAP硫氰酸根分别与重铬酸根,铈(IV)在硫酸介质中反应成不稳定的蓝色产物,建立了两种测定微量硫氰酸根的流动注射分光光度新方法,在前一方法中,硫氰酸根含量在0.80~7.20mg/L范围内可定量测定,检出限为0.27mg/L在后一方法中,硫氰酸根含量在0.80~6.40mg/L范围内呈线性,检出限为0.30mg/L。当进样体积为100μL时,进样频率为60次/h,所建立的两 相似文献
87.
流动注射-结晶紫-磷钼杂多酸离子缔合体系光度法测定水中痕量正磷酸盐 总被引:2,自引:0,他引:2
在一定的酸度条件下,结晶紫与磷钼杂多酸离子缔合物的流动注射分光光度法可直接测定痕量磷.灵敏度高,重现性和选择性好.水中常见离子不干扰痕量磷的测定,工作曲线的线性范围为0~500μg·L~(-1)的磷,检出下限达1.0μg·L~(-1),以120h~(-1)采样频率,对各种天然水样进行测定,回收率为92.5%~105.0%,相对标准偏差为0.1%~6.7%. 相似文献
88.
The epoxy-impregnated graphite tube electrode bulk modified with 2-mercaptobenzoxazole, employed in a wall-jet configuration, was found to be useful for the continuous flow and flow injection stripping voltammetric determinations of AgI, HgII and BiIII. For continuous flow, detection limits for AgI, HgII and BiIII were 1.8 × 10−10 M, 1.9 × 10−9 M and 9.5 × 10−9 M, respectively (10 min accumulation, S/N = 3). Precisions for 5.00 × 10−9 M AgI, 1.00 × 10−8 M HgII and 1.00 × 10−7 M BiIII were 10.5%, 5.77 % and 7.90% (relative standard deviations, n = 6), respectively. In the case of flow injection stripping, with a 500 μL injection loop, detection limits of 0.59 ng, 2.0 ng and 120 ng were obtained for AgI, HgII and BiIII, respectively (S/N = 3). Selected metal ions, inorganic and organic substances were investigated for interferences. The electrode was tested with a certified sample and then applied to the determinations of the metal ions in a urine and a sea-water sample. 相似文献
89.
Selective flow-injection determination of methanol in the presence of ethanol based on a multi-enzyme system with chemiluminescence detection 总被引:2,自引:0,他引:2
Yoshiie Sekine
Masayasu Suzuki
Toshifumi Takeuchi Eiichi Tamiya Isao Karube 《Analytica chimica acta》1993,280(2):179-184A highly selective flow-injection system was developed for the determination of methanol. The system consisted of three immobilized enzymes with luminol chemiluminescence detection. First, methanol was oxidized in the presence of alcohol oxidase to yield formaldehyde and hydrogen peroxide. The hydrogen peroxide produced was then destroyed by catalase. The formaldehyde formed in the first stage was further oxidized by NAD+-formaldehyde dehydrogenase. The NADH formed was oxidized by 1-methoxy-5-methylphenazinium methylsulphate (1-MPMS), and finally the reduced 1-MPMS was spontaneously oxidized and hydrogen peroxide was produced. The concentration of the hydrogen peroxide produced, which was proportional to the initial concentration of methanol, was determined by luminol chemiluminescence. The determination range was from 0.1 to 100 mg l−1 and the response time was less than 2 min per sample with a relative standard deviation of less than 3%. The system showed good selectivity for methanol; the response was ca. 50 times higher than for ethanol. 相似文献
90.