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21.
A method for calibration and validation subset partitioning 总被引:13,自引:0,他引:13
This paper proposes a new method to divide a pool of samples into calibration and validation subsets for multivariate modelling. The proposed method is of value for analytical applications involving complex matrices, in which the composition variability of real samples cannot be easily reproduced by optimized experimental designs. A stepwise procedure is employed to select samples according to their differences in both x (instrumental responses) and y (predicted parameter) spaces. The proposed technique is illustrated in a case study involving the prediction of three quality parameters (specific mass and distillation temperatures at which 10 and 90% of the sample has evaporated) of diesel by NIR spectrometry and PLS modelling. For comparison, PLS models are also constructed by full cross-validation, as well as by using the Kennard-Stone and random sampling methods for calibration and validation subset partitioning. The obtained models are compared in terms of prediction performance by employing an independent set of samples not used for calibration or validation. The results of F-tests at 95% confidence level reveal that the proposed technique may be an advantageous alternative to the other three strategies. 相似文献
22.
Shi-Rong Hu Jia-Ming Liu Tian-Long Yang Hai-Zhu Liu Jun-Li Huang Qing-Wei Lin Guo-Hui Zhu Xiao-Mei Huang 《Mikrochimica acta》2005,152(1-2):53-59
Luminescent nanoparticles of silicon dioxide (SiO2) containing fluorescein isothiocyanate (FITC) with a particle size of 20 nm were synthesized using the Sol–Gel method (abbreviated
FITC–SiO2). FITC–SiO2 nanoparticles whose surfaces are modified (FITC–SiO2–S–CH2COOH) can emit strong and stable solid substrate room temperature phosphorescence (SS-RTP) on acetyl cellulose membranes.
When the original color-producing agent (R) in the enzyme-linked immunosorbent assay (ELISA) kits for determination of alpha-fetoprotein
(AFP) was substituted with (FITC–SiO2–S–CH2COOH), the system maintained good FITC–SiO2 phosphorescence properties. Furthermore, the phosphorescence intensity enhanced markedly after the ELISA reaction. The relationship
between the phosphorescence intensity and the content of AFP obeyed Beer’s law. Based on the facts stated above, a new method
for the determination of human AFP by SS-RTP-ELISA (using the luminescent nanoparticle as marker) was established. The linear
range of this method is 0.040–16.0 pg of human AFP per spot (sample volume: 0.40 μL spot−1, corresponding concentration: 0.10–40.0 ng mL−1). The regression equation of the working curve is ΔIp = −6.289+18.075 mAFP (pg spot−1) (r = 0.9960, n = 6). The detection limit (LD) of this method calculated by 3 Sb/k is 6.7 fg spot−1 (corresponding concentration: 17 ng L−1). Compared to the ELISA method using a traditional color-producing agent, the new method exhibited a 34.8 times higher sensitivity
and a wider linear range. The method has been successfully applied to the determination of human AFP in serum. 相似文献
23.
24.
Bernaus A Gaona X Ivask A Kahru A Valiente M 《Analytical and bioanalytical chemistry》2005,382(7):1541-1548
The present work studies the adsorption behaviour of mercury species on different soil components (montmorillonite, kaolinite and humic acid) spiked with CH3HgCl and CH3HgOH at different pH values, by using XAS techniques and bacterial mercury sensors in order to evaluate the availability of methyl mercury on soil components. The study details and discusses different aspects of the adsorption process, including sample preparation (with analysis of adsorbed methyl mercury by ICP-OES), the various adsorption conditions, and the characterization of spiked samples by XAS techniques performed at two synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany), as well as bioavailability studies using mercury-specific sensor bacteria. Results show that XAS is a valuable qualitative technique that can be used to identify the bonding character of the Hg in mercury environment. The amount of methyl in mercury adsorbed to montmorillonite was pH-dependent while for all soil components studied, the bond character was not affected by pH. On the other hand, clays exhibited more ionic bonding character than humic acids did with methyl mercury. This interaction has a higher covalent character and so it is more stable for CH3HgOH than for CH3HgCl, due to the higher reactivity of the hydroxyl group arising from the possible formation of hydrogen bonds.The bioavailability of methyl mercury adsorbed to montmorillonite, kaolinite and humic acids was measured using recombinant luminescent sensor bacterium Escherichia coli MC1061 (pmerBRBSluc). In case of contact exposure (suspension assays), the results showed that the bioavailability was higher than it was for exposure to particle-free extracts prepared from these suspensions. The highest bioavailability of methyl mercury was found in suspensions of montmorillonite (about 50% of the total amount), while the bioavailabilities of kaolinite and humic acids were five times lower (about 10%). The behaviour of methyl mercury in the presence of montmorillonite could be explained by the more ionic bonding character of this system, in contrast to the more covalent bonding character observed for humic acids. Thus, XAS techniques seem to provide promising tools for investigating the mechanisms behind the observed bioavailabilities of metals in various environmental matrices, an important topic in environmental toxicology. 相似文献
25.
在溶剂热条件下,基于芳香四羧酸合成了2种新颖的配位聚合物:{[Zn2(tptc)(1,4-bimb)2]·H2O}n(1)和{[Ni(tptc)0.5(1,2-bimb)(H2O)]·H2O}n(2),其中,tptc为对-三联苯-3,3″,5,5″-四羧酸,1,4-bimb为1,4-二(咪唑-1-亚甲基)苯,1,2-bimb为1,2-二(咪唑-1-亚甲基)苯。结构分析表明,1为三维结构,拓扑符号为(86);2为二维层状网络,通过氢键相互作用进一步扩展为三维超分子结构。此外,我们还研究了1对阳离子、阴离子的荧光感应以及2的磁性质。 相似文献
26.
A novel near infrared (NIR) modeling method—Laplacian regularized least squares regression (LapRLSR) was presented, which can take the advantage of many unlabeled spectra to promote the prediction performance of the model even if there are only few calibration samples. Using LapRLSR modeling, NIR spectral analysis was applied to the online monitoring of the concentration of salvia acid B in the column separation of Salvianolate. The results demonstrated that LapRLSR outperformed partial least squares (PLS) significantly, and NIR online analysis was applicable. 相似文献
27.
The preparation and properties of cyanobiphenyl liquid crystal droplets encapsulated by the polymerizable lecithin 1,2-bis(10,12-tricosadiynoyl)-sn-glyero-3-phosphocholine (DC8,9PC) are described. Under a wide variety of preparation conditions the droplets obtain a diameter of approximately 10 mum. These droplets are stable for periods of over one year at room temperature. Furthermore, they are stable upon temperature cycling between the nematic and isotropic phases and between the smectic A to nematic to isotropic phase transitions. 相似文献
28.
通过一个含3个羧基基团的多功能配体2-羟基-1,3,5-苯基三羧酸(HO-H3BTC)与锌盐构筑了一个三维多孔锌骨架结构配合物,{[Zn4(O-BTC)2(H2O)5]·2DMF·0.5H2O}n(1)。通过单晶X射线衍射、粉末X射线衍射、元素分析、红外光谱、热重分析以及固体紫外吸收光谱对该配合物进行了表征。配合物1是通过棒状金属锌-羧酸/羟基次级结构单元构筑的一个三维骨架结构,其在室温下显示强烈的蓝色荧光。此外,在低温条件下(10 K)配合物1显示余晖性质。 相似文献
29.
Four new coordination polymers, [Cd(3-TPTP)Cl]2 (3-HTPTP = 4′-(3-tetrazolylphenyl)2,2′:6′2′′-terpyridine, 1), {[Cd(3-TPTP)(pBDC)0.5]?4H2O}n (pH2BDC = 1,4-benzenedicarboxylic acid, 2), {[Mn(3-TPTP)(mBDC)0.5]?5H2O}n (mH2BDC = 1,3-benzenedicarboxylic acid, 3), and [Pb(3-TPTP)(H2O)2]?OH (4), were obtained. Compounds 1–3 are composed of binuclear [M2(3-TPTP)2] ring as building unit. In 1, the binuclear rings pack into a 3-D supramolecular framework via various hydrogen bonds. In 2 and 3, the binuclear rings are connected by mBDC2? and pBDC2?, respectively, resulting in two types of 1-D chains. In 4, the mononuclear [Pb(3-TPTP)] units are connected by Pb?N weak interactions, giving a chiral 1-D coordination chain, which is further connected by O–H?N interaction to form a chiral 3-D supramolecular framework. The phase purity of 1–4 and luminescence properties of 1, 2, and 4 were also investigated. 相似文献
30.
A novel terbium(III) coordination polymer [Tb(C7H3NO4)(C6H4NO2)(H2O)] was successfully synthesized hydrothermally and characterized by single-crystal X-ray diffraction. The complex is of monoclinic, space group P21/c with a = 9.2252(11), b = 14.1477(16), c = 10.5134(12) A, β = 95.770(2)°, V = 1365.2(3) A3, Z = 4, Dc = 2.248 g·cm-3, F(000) = 880, the final R = 0.0176 and w R = 0.0411 for 2149 observed reflections with I 2σ(I). The complex is extended into a three-dimensional network structure with 24-atom rings which are composed of Tb, C and O atoms. The complex displays green fluorescence emission in the solid state at room temperature, which corresponds to 5D4 → 7F5 transition of the Tb(III) ion. 相似文献