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901.
使用PAN-Ni(Ⅱ)共沉淀体系分离富集、微量流向进样火焰原子吸收光谱测定饮水和人发中的微量锰。样品中的共存元素不干扰测定,锰的标准加入回收率90%-108%之间。12次重复测定锰含量为0.15μg/mL的试样溶液的变异系数为4.6%,本法简便快捷,取得了较满意的结果. 相似文献
902.
端视等离子体原子发射光谱仪的性能评价 总被引:4,自引:0,他引:4
端视等离子体原子发射光谱仪与侧视等离子体原子发射光谱仪相比在分析性能方面所表现出来的差异一直是光谱分析工作者所关注的一个重要方面。此文较系统的总结了近年来在此方面所做的研究工作,引用47篇文献。 相似文献
903.
Yu Ping ZHANG Wen Jun GONG Li Qun FAN Yi Jun ZHANG Kwang Pill LEE 《中国化学快报》2006,17(11):1485-1488
A porous monolithic sol-gel column with the solution of methacryloxypropyltrimethoxysilane in toluene with an acid catalyst was prepared in the presence and absence of sodium dodecyl sulfate. In situ polymerization was carried out byγ-ray irradiation within the capillary. Theγ-radiation-initiated synthesis could generate radicals directly on the monomer avoiding use of any initiator. The chromatographic behavior of the capillary monolithic columns were studied in the modes of CEC, p-CEC and low pressure-driven separation, all the tests exhibited reversed-phase character. It provided a viable alternative to either thermally initiated or photo polymerization method for the preparation of monolithic columns. 相似文献
904.
Terbium copper disulfide, TbCuS2, has been synthesized in the reaction of the elements in a KI flux at 850 ℃. The compound crystallizes in space group P21/c of the monoclinic system with four formula units in a cell of dimensions of a= 0.639 3(1) nm, b=0.702 5(1) nm, c=0.670 8(1) nm, β=98.097(4)°, and V=0.298 3(1) nm3 at 153 K. The structure comprises two-dimensional 2∞[CuS2] layers along [100] separated by the Tb atoms. In the structure, each Tb and Cu atoms are coordinated to seven and four S atoms, respectively. CSD: 415490. 相似文献
905.
AnExplanationontheElectronIonizationMassSpectraofCrownEthersbyMNDOComputationalMethodYUANHu-shan,TANGMing-shengandWUYang-jie(... 相似文献
906.
907.
908.
Masayoshi Nakasako Masamitsu Wada Satoru Tokutomi Kotaro T. Yamamoto Jun Sakai Mikio Kataoka Fumio Tokunaga † Masaki Furuya 《Photochemistry and photobiology》1990,52(1):3-12
Abstract— The quaternary structure of pea phytochrome type I (PI) dimer in the red-light-absorbing form was studied by small-angle X-ray scattering (SAXS) technique and rotary-shadowing electron microscopy. Structural parameters for PI 114 kDa chromopeptide dimer and its tryptically digested N-terminal 59 kDa chromopeptide monomer, such as average electron density, molecular volume and the second moment of electron density distribution, were determined in terms of SAXS using the contrast variation method. Furthermore, by means of model simulation for the scattering profiles of the chromopeptides, most plausible structural models for both peptides were constructed. The distance between the chromophoric domains was estimated to be about 70 A in the resultant model for 114 kDa chromopeptide dimer. Furthermore, the model was consistent with the electron-micrographic images of both the intact PI dimer and the PI 114 kDa chromopeptide dimer, so that the N-terminal 7 kDa fragment did not significantly contribute the low-resolution images of the dimer. 相似文献
909.
Okada Y Yokozawa M Akiba M Oishi K O-kawa K Akeboshi T Kawamura Y Inokuma S Nakamura Y Nishimura J 《Organic & biomolecular chemistry》2003,1(14):2506-2511
A variety of aromatic compounds with both activating and deactivating substituents were brominated with sodium monobromoisocyanurate (SMBI) 1, diethyl ether, diethyl ether-methanesulfonic acid, trifluoroacetic acid, or sulfuric acid were employed as solvents. Thus nitrobenzene was conveniently brominated in sulfuric acid, benzene was readily monobrominated in diethyl ether-methanesulfonic acid, and phenol was selectively brominated at the ortho position under mild conditions in refluxing diethyl ether. With substituents that are easily protonated, trifluoroacetic acid may be employed as solvent in the reaction with 1, in contrast NBS was ineffective in trifluoroacetic acid. This renders 1 a superior reagent relative to NBS. In addition to aromatics, alkenes, ketones and esters were also brominated with 1. Diethyl malonate was brominated with 1 and then subjected to a Bingel reaction with NaH to afford the desired methanofullerene in reasonable yield. 相似文献
910.
N,N′-双吡咯的合成及其邻位基团效应 总被引:1,自引:0,他引:1
2,2-联吡咯是某些天然存在的活性吡咯化合物中关键组成,关于手性联吡咯的研究己有详细的综述报道。近年发现,某些含N-取代氨基的空间阻碍吡咯有明显的生理活性和可贵的药理性质。N,N′-联吡咯中N-N键,很容易发生均裂反应而生成游离基,后 相似文献