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991.
Xuean?ChenEmail author Chunyan?Yang Zhipeng?Chu Xinan?Chang Hegui?Zang Weiqiang?Xiao 《Journal of chemical crystallography》2011,41(6):816-822
Abstract
A novel quaternary borate, Na2.18K0.82SrB5O10, has been prepared by high-temperature solution reaction below 800 °C. Single-crystal XRD analyses showed that it crystallizes in the triclinic P[`1] P\bar{1} group with a = 7.3900(15) ?, b = 7.6490(15) ?, c = 9.773(2) ?, α = 79.31(2)°, β = 70.85(2)°, γ = 62.09(1)°, Z = 2. The basic structural unit in Na2.18K0.82SrB5O10 is a double ring [B5O10]5− composed of one BO4 tetrahedron and four BO3 triangles. The [B5O10]5− groups are arranged around crystallographic centers of symmetry to form [B10O20]10− columns that are held together by Na+, K+/Na+, and Sr2+ cations via electrostatic interactions. The IR spectrum further confirmed the presence of both BO3 and BO4 groups. UV–vis diffuse reflectance spectrum showed a band gap of about 3.80 eV. Solid-state fluorescence spectrum exhibited the maximum emission peak at around 337.6 nm. 相似文献992.
Kwak HB Yang D Ha H Lee JH Kim HN Woo ER Lee S Kim HH Lee ZH 《Experimental & molecular medicine》2006,38(3):256-264
Bone is a dynamic tissue that is regulated by the activity of bone-resorbing osteoclasts and bone-forming osteoblasts. Excessive osteoclast formation causes diseases such as osteoporosis and rheumatoid arthritis. Natural substances may be useful as therapeutic drugs to prevent many diseases in humans because they avoid the many side effects of treatment with chemical compounds. Here we show that tanshinone IIA isolated from Salvia miltiorrhiza Bunge inhibits the receptor activator of NF-kappaB ligand (RANKL)-mediated osteoclast differentiation of osteoclast precursors. Tanshinone IIA suppressed the expression levels of c-Fos and NFATc1 induced by RANKL. However, retrovirus-mediated overexpression of c-Fos induced the expression of NFATc1 despite the presence of tanshinone IIA and reversed the inhibitory effect of tanshinone IIA on osteoclast differentiation. Also, the introduction of osteoclast precursors with the NFATc1 retrovirus led to osteoclast differentiation in the presence of tanshinone IIA. Our results suggest that tanshinone IIA may have a role as a therapeutic drug in the treatment of bone disease such as osteoporosis. 相似文献
993.
Wu J Wang F Ma Y Cui X Cun L Zhu J Deng J Yu B 《Chemical communications (Cambridge, England)》2006,(16):1766-1768
The first asymmetric transfer hydrogenation of cyclic imines and iminiums in water was successfully performed in high yields and enantioselectivities with sodium formate as the hydrogen source and CTAB as an additive catalyzed by a water-soluble and recyclable ruthenium(II) complex of the ligand (R,R)-2. 相似文献
994.
Shen Q Wei H Zhou Y Huang Y Yang H Wang D Xu D 《The journal of physical chemistry. B》2006,110(7):2994-3000
The fast mixing of aqueous solutions of calcium chloride and sodium carbonate could immediately result in amorphous calcium carbonate (ACC). Under vigorous stirring, the formed ACC in the precipitation system will dissolve first and, then, transform within minutes to produce crystalline forms of vaterite and calcite. After that, the solution-mediated mechanism dominates the transformation of the thermodynamically unstable vaterite into the thermodynamically stable calcite. Although ACC is the least stable form of the six anhydrous phases of calcium carbonate (CaCO(3)), it could be, however, produced and stabilized by a variety of organisms. To better understand the formation-transformation mechanism of ACC and vaterite into calcite, ex-situ methods (i.e., scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy) were used to characterize the formation-transformation process of ACC and vaterite in aqueous systems without organic additives, showing that ACC sampled at different conditions has different properties (i.e., lifetime, morphology, and spectrum characterization). It is also very interesting to capture the obviously polycrystalline particles of CaCO(3) during the transformation process from vaterite to calcite, which suggests the formation mechanism for the calcite superstructure with multidimensional morphology. 相似文献
995.
Hongge Jia Jun Li Yu Zang Toshiki Aoki Masahiro Teraguchi Takashi Kaneko 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5134-5143
Four novel chiral phenylacetylenes having an L ‐amino alcohol residue and two hydroxymethyl groups were synthesized and polymerized by an achiral catalyst ((nbd)Rh+[η6‐(C6H5)B?(C6H5)3]) or a chiral catalytic system ([Rh(nbd)Cl]2/(S)‐ or (R)‐phenylethylamine ((S)‐ or (R)‐PEA)). The two resulting polymers having an L ‐valinol or L ‐phenylalaninol residue showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one‐handed helical backbones. Positive and negative Cotton effects were observed only for the polymers having an L ‐valinol residue produced by using (R)‐ and (S)‐PEA as a cocatalyst, respectively, although the monomer had the same chirality. Even when the achiral catalyst was used, the two resulting polymers having an L ‐valinol or L ‐phenylalaninol residue showed Cotton effects despite the long distance between the chiral groups and the main chain. We have found the first example of a new type of chiral monomer, that is, a chiral phenylacetylene monomer having an L ‐amino alcohol residue and two hydroxy groups that was suitable for both modes of asymmetric polymerization, that is, the helix‐sense‐selective polymerization ( HSSP ) with the chiral catalytic system and the asymmetric‐induced polymerization ( AIP ) with the achiral catalyst. The other two monomers having L ‐alaninol and L ‐tyrosinol were found to be unsuitable to neither HSSP nor AIP because of their polymers' low solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
996.
Novel isolated,L‐amino acid‐ligated rhodium catalysts that induce highly helix‐sense‐selective polymerization of an achiral 3,4,5‐trisubstituted phenylacetylene
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Hongge Jia Yongqiang Shi Liqun Ma Xuan Gao Yazhen Wang Yu Zang Jijun Peng Toshiki Aoki Masahiro Teraguchi Takashi Kaneko Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2346-2351
Two novel chiral well‐defined rhodium complexes, Rh(cod)(L‐Phe) (cod = 1,5‐cyclooctadiene, Phe = phenylalanine) and Rh(cod)(L‐Val) (Val = valine) were synthesized, isolated by recrystallization, and characterized. The helix‐sense‐selective polymerization (HSSP) of an achiral 3,4,5‐trisubstituted phenylacetylene, p‐dodecyloxy‐m,m‐dihydroxyphenylacetylene (DoDHPA) was examined by using the two Rh complexes as catalysts. These catalysts provided high molecular weight polymers (Mw 28 × 104?45 × 104) in about 40%–85% yields. The resulting polymers exhibited a bisignated CD signal at about 300 nm and a broad signal around 470 nm, indicating that they have preferential one‐handed helical structure. The present catalysts achieved larger molar ellipticity up to [θ]310 = 13.0 × 104 deg cm2/dmol than those with binary chiral catalytic systems, [Rh(cod)Cl]2/(L‐phenylalaninol), [Rh(cod)Cl]2/(L‐valinol), and [Rh(nbd)Cl]2/(R)‐PEA. All these results manifest that the present, well‐defined Rh complexes serve as excellent catalysts for the HSSP of DoDHPA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2346–2351 相似文献
997.
Jiwu Wen Limin Liu Xiaochun Zhou Ronghua Hu Yaping Xu 《Tetrahedron: Asymmetry》2013,24(13-14):860-865
A variety of novel hydroxyl-containing tetradentate bisoxazolines were successfully synthesized from natural l-serine and β-DDB. The applications of these ligands in the asymmetric pinacol coupling of aromatic aldehydes revealed that the absolute configurations of the resulting pinacols were entirely dominated by the axial chirality of the biphenyl component and that the bulky substituent adjacent to the hydroxyl group was favorable for achieving both high diastereoselectivities and enantioselectivities. Among the ligands screened, (S,aR,S)-1c exhibited much better asymmetric induction capacity to furnish the (R,R)-pinacols with diastereoselectivities up to 99/1 and with 63–89% enantiomeric excess. A plausible mechanism of the asymmetric pinacol coupling was also suggested. 相似文献
998.
999.
微热管以其效率高、响应快且无能耗,在高功率集成微电子散热方面应用广泛。针对电子器件的小型化、高能耗发展趋势,本文提出一种新型沟槽道微热管结构,对该沟槽道微热管进行稳态和瞬态热性能实验研究,研究了风速、角度、加热功率等因素对该新型热管的热性能影响规律。结果表明,该微热管在整个散热器传热上起主导作用,性能比达到0.88,冷凝端温差为0.8℃,具有良好的均温性,该微热管加热功率为140 W,空气流速1.5 m/s时,换热系数可达2 359 W/(m^2·℃),热阻为0.27℃/W;高功率状态下可保持良好的热扩散性能,有效避免微热管的热应力集中,有望高效解决集成电子器件的散热问题。 相似文献
1000.
Back Cover: Controlled Synthesis of Ultrathin Lanthanide Oxide Nanosheets and Their Promising pH‐Controlled Anticancer Drug Delivery (Chem. Eur. J. 34/2015)
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