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991.
为了解决在乒乓球比赛和训练中人工手动捡球的问题,从机器视觉的角度出发,综合嵌入式、图像处理和测量控制等技术,基于第三方库OpenCV设计了一种自动捡乒乓球系统。系统是以Contex-A8平台为控制核心,首先通过对云台和USB摄像头的控制获取视频信号;然后通过霍夫圆变换和SVM分类器算法识别出视频中的乒乓球,并根据质心计算出其与系统的相对位置;最后将视频信号中抽象出的位置信息传递给机械运动控制终端,控制小车和机械手将乒乓球捡起,并送到指定位置。实验结果表明本系统能够正确的检测和识别乒乓球,并对其进行定位捡取,效果良好,提高了拾取乒乓球的效率,减轻工作人员的负担。 相似文献
992.
993.
The Crystal Structure and Synthesis Mechanism of 3,6‐Bis(3,5‐dimethylpyrazol‐1‐yl)‐1,4‐dihydro‐1,2,4,5‐tetrazine (BDT): A Key Precursor of S‐tetrazine 下载免费PDF全文
Jian‐Guo Zhang Jin‐Ting Wu Mou Sun Jin‐Ling Feng Tong‐Lai Zhang Zun‐Ning Zhou 《Journal of heterocyclic chemistry》2014,51(Z1):E234-E240
The single crystal structure of 1,1′‐bis (3,5‐dimethyl‐pyrazole) methenehydrazine (BDM) was determined by X‐ray single crystal diffraction for the first time. The obtained experimental results indicated that BDM was the intermediate of 3,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,4‐dihydro‐1,2,4,5‐tetrazine (BDT), which was the key precursor of s‐tetrazine. By this evidence, the preparation mechanism of BDT was proved: At 318.15 K, triaminoguanidine and pentanedione reacted to achieve the intermediate (BDM) by molecular nucleophilic addition and intramolecular nucleophilic substitution; when heated to 363.15 K, BDT was then generated by two molecules of BDM with nucleophilic substitution reaction. Furthermore, the thermal decomposition properties and also the non‐isothermal kinetic parameters have been investigated in the present work. 相似文献
994.
Silica Sulfuric Acid‐Catalyzed Five‐component Efficient Synthesis of Five‐Substituted Tetrahydropyridines 下载免费PDF全文
Xiao‐xiao Zhang Yu Wan Li‐ling Pang Hai‐ying Wang Ling‐ling Zhao Chao Wang Shu Ying Hang Gui Xiang Liu Liang‐Feng Chen Hui Wu 《Journal of heterocyclic chemistry》2014,51(2):442-449
A highly atom‐economic one‐pot synthesis of five‐substituted tetrahydropyridines via a five‐component condensation of two equivalents of aromatic aldehyde, two equivalents of aromatic aniline, and one equivalent of β‐keto ester catalyzed by silica sulfuric acid is reported. In this reaction, up to five new bonds and one new ring were formed in one pot with water as the only one by‐product. 相似文献
995.
Guangfeng Wang Yanhong Zhu Xiuping He Ling Chen Lun Wang Xiaojun Zhang 《Mikrochimica acta》2014,181(3-4):411-418
We report on the detection of trace quantities of melamine (MA) by a colorimetric method that exploits the conformational change of hemin G-quadruplex-DNAzyme. The addition of MA to hemin G-quadruplex-DNAzyme structure containing thymine bases causes the thymine in the DNAzyme to interact with MA via a stable triple H-bond and leads to a conformational change. This, in turn, affects the peroxidase-like activity of hemin which is determined colorimetrically at 450 nm by adding 3,3’,5,5’-tetramethylbenzidine and hydrogen peroxide. The method was applied to the colorimetric determination of MA over a wide range of concentrations (0.2 to 24 μM) with a detection limit of 80 nM. The effect also can be detected with bare eyes. The method was successfully applied to the determination of MA in spiked milk powder. Figure
A novel, simple and rapid, visual colorimetric method is applied for the detection of melamine with a wide range of 8?×?10?7 M to 1?×?10?3 M and low detection limit of 2.7?×?10?7 M. 相似文献
996.
Two new complexes, {[Co(INAIP) · H2O] · 2H2O}n ( 1 ), and {[Cu(INAIP)] · H2O}n ( 2 ) [H2INAIP = 5‐(isonicotinamido)isophthalic acid] were synthesized under hydrothermal conditions, and characterized by single‐crystal X‐ray structure determination, thermogravimetric analysis, X‐ray powder diffraction, and magnetic studies. In complex 1 both CoII atoms and INAIP2– ligands act as four‐connected node, whereas in 2 both CuII atoms and INAIP2– ligands act as three‐connected node. 相似文献
997.
998.
A method is proposed for the estimation of absolute binding free energy of interaction between proteins and ligands. The linear interaction energy method is combined with atom‐bond electronegativity equalization method at σπ level Force field (fused into molecular mechanics) and generalized Born continuum model calculation of electrostatic solvation for the estimation of the absolute free energy of binding. The parameters of this method are calibrated by using a training set of 24 HIV‐1 protease–inhibitor complexes (PDB entry 1AAQ). A correlation coefficient of 0.93 was obtained with a root mean square deviation of 0.70 kcal mol?1. This approach is further tested on seven inhibitor and protease complexes, and it provides small root mean square deviation between the calculated binding free energy and experimental binding free energy without reparametrization. By comparing the radii of gyration and the hydrogen bond distances between ligand and protein of three training model molecules, the consistent comparison result of binding free energy is obtained. It proves that this method of calculating the binding free energy with appropriate structural analysis can be applied to quickly assess new inhibitors of HIV‐1 proteases. To test whether the parameters of this method can apply to other drug targets, we have validated this method for the drug target cyclooxygenase‐2. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011 相似文献
999.
The amorphous and crystalline phase behavior, spherulite morphology, and interactions between amorphous poly(vinyl acetate)
(PVAc) and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) were examined using differential scanning calorimetry,
polarized-light optical and scanning electron, atomic-force microscopy (DSC, POM, SEM, AFM), and small-angle X-ray scattering
(SAXS). The PHBV/PVAc blend was found to be miscible with an almost linear T
g-composition relationship, indicating perfect homogeneity. Interaction parameter by melting point depression is a negative
value of χ = −0.32, suggesting quite favorable interaction strength. With the intimate interaction between the amorphous PVAc and crystalline
PHBV polymers, effects of PVAc on the spherulitic morphology of PHBV are quite significant. Owing to the higher T
g of PVAc (than that of PHBV), the spherulite growth rate of PHBV was depressed by increasing PVAc content in blends. Neat
PHBV exhibits ring-banded spherulites when crystallized at Tc = 60 ~ 110° C {T_{\rm{c}}} = {6}0\sim {11}0^\circ {\hbox{C}} ; however, with increasing PVAc content in the blends, the temperature range at which the PHBV/PVAc blends exhibit ring-banded
spherulites remains similar but the regularity increases, and the inter-ring spacing significantly decreases. In addition,
the spherulite size and ring-band patterns therein are strongly dependent on T
max (190 vs. 220 °C, respectively, for erasing prior nuclei), from which the blends were quenched to a T
c (60–110 °C) for crystallization. For PHBV/PVAc blends crystallized at the same T
c from different T
max, higher T
max tends to erase nuclei, leading to larger spherulites. However, such larger spherulites owing to higher T
max are not necessarily packed with thicker lamellae. 相似文献
1000.
Computational and theoretical models of millimeter-sized bubbles placed on upright hydrophobic and superhydrophobic surfaces are compared with experimental data here. Although the experimental data for a hydrophobic surface corroborated the computational and theoretical data, the case of a superhydrophobic surface showed the bubbles to be able to contain significantly larger volumes than predicted. This is attributed to the greater ability of the bubble contact line to advance compared with its tendency to detach from the surface because of buoyancy. We surmise that a static model therefore describes only an unstable equilibrium for these bubbles, which unless heavily isolated from external influences are more likely to assume a larger stable size. 相似文献