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61.
Steven M. Maley Graham R. Lief Richard M. Buck Orson L. Sydora Qing Yang Steven M. Bischof Daniel H. Ess 《Journal of computational chemistry》2023,44(4):506-515
Quantum-mechanical-based computational design of molecular catalysts requires accurate and fast electronic structure calculations to determine and predict properties of transition-metal complexes. For Zr-based molecular complexes related to polyethylene catalysis, previous evaluation of density functional theory (DFT) and wavefunction methods only examined oxides and halides or select reaction barrier heights. In this work, we evaluate the performance of DFT against experimental redox potentials and bond dissociation enthalpies (BDEs) for zirconocene complexes directly relevant to ethylene polymerization catalysis. We also examined the ability of DFT to compute the fourth atomic ionization potential of zirconium and the effect the basis set selection has on the ionization potential computed with CCSD(T). Generally, the atomic ionization potential and redox potentials are very well reproduced by DFT, but we discovered relatively large deviations of DFT-calculated BDEs compared to experiment. However, evaluation of BDEs with CCSD(T) suggests that experimental values should be revisited, and our CCSD(T) values should be taken as most accurate. 相似文献
62.
多核过渡金属配合物作为一类广泛应用的均相催化剂,其设计灵感往往来自天然酶的多金属活性位点所发挥的重要作用.目前,三核金属配合物作为活化小分子的多金属催化剂受到了广泛的关注.为深入理解三核过渡金属配合物在催化反应中作用特点,对近年报道的代表性三核过渡金属配合物按金属中心进行分类,并对配体环境形成特点及催化应用进行综述.从金属中心出发,讨论了三核过渡金属配合物的几何结构和电子特征;从配体环境出发,总结了关联三个独立的金属位点的配位环境特征;在催化应用方面,重点综述了三核过渡金属配合物在涉及特定化学键活化反应的催化作用机制,最后对三核过渡金属配合物的催化应用前景进行展望. 相似文献
63.
64.
1902年,瑞士化学家维尔纳对氯化铵结构的解释为氢键概念的形成奠定了基础。1920年,美国化学家拉提麦尔和罗德布什首先认识了水中的氢键:2个八隅体所持的氢核构成的“弱键(weak bond)”。1928年,美国化学家鲍林在解释[FHF]-的结构时首次使用“氢键(hydrogen bond)”一词,但并未对氢键的概念进行明确定义。1939年,鲍林在《化学键的本质》中明确提出了氢键的概念,并解释了氢键的性质,自此,氢键的概念正式形成。近年来,科学家经过深入研究发现了氢键的新类型:π型氢键、双氢键、金属氢键和单电子氢键。随着科学思想和科学技术的发展,关于氢键的认识也会越来越深入。 相似文献
65.
Guopeng Du Pingliang Zhu Jing Wang Xinjin Li Dao-Peng Zhang Chuan-Zeng Wang Prof. Dr. Feng-Gang Sun 《European journal of organic chemistry》2023,26(6):e202201382
Herein, we report a palladium/norbornene/copper co-catalyzed single-step approach that merges selective ortho C−H bond esterification with ipso thiolation for construction of synthetically versatile 2-arylthio aryl esters under exceptionally mild conditions. Importantly, this process proceeded in a highly efficient manner, allowing alkoxycarbonyl and thio groups to be installed into one aryl iodides simultaneously by harnessing thiocarbonate as bifunctional reagent. The method has been demonstrated to accommodate good functionalities and features broad substrate scope. 相似文献
66.
Dr. Serhii Krykun Dr. Muriel Durandetti 《European journal of organic chemistry》2023,26(4):e202201393
A convenient and efficient approach for the construction of aryl trifluoromethyl selenoethers from aryl iodides under mild conditions is reported. Electrochemical activation of stable and inexpensive NiBr2bipy (bipy – bipyridine) complex instead of labile Ni(COD)2 (COD – cyclooctadiene) catalyst. [NMe4][SeCF3] is employed as shelf-stable source of SeCF3 fragment. The reaction tolerates a wide range of substrates, including modification of drug-like molecules. Cyclic voltammetry studies allow insight into the reaction mechanism. 相似文献
67.
Prof. Domenico C. M. Albanese Dr. Michele Penso 《European journal of organic chemistry》2023,26(19):e202300224
Phase Transfer Catalysis (PTC) is a powerful tool to perform reactions in a practical fashion, both in laboratory and industrial scale. Significant cost savings and major process improvements can be achieved in reactions performed under PTC conditions. In the last few years remarkable results in stereoselective reactions were achieved using chiral, non-racemic quaternary ammonium salts. Moreover, the use of bulky, chiral phosphate anions paired with achiral cations to generate lipophilic ion pairs allowed to design new avenues for the stereoselective construction of important building blocks. Hydrogen bond interactions were also shown to provide new pathways for asymmetric nucleophilic substitutions using insoluble reagents under PTC conditions. This Review will focus on recent advances in developing practical synthetic routes to construct molecules in a stereoselective fashion under PTC conditions. 相似文献
68.
Prof. Dr. Takanori Iwasaki Prof. Dr. Nobuaki Kambe 《Chemical record (New York, N.Y.)》2023,23(9):e202300033
Carbon-fluorine bonds are stable and have demonstrated sluggishness against various chemical manipulations. However, selective transformations of C−F bonds can be achieved by developing appropriate conditions as useful synthetic methods in organic chemistry. This review focuses on C−C bond formation at monofluorinated sp3-hybridized carbons via C−F bond cleavage, including cross-coupling and multi-component coupling reactions. The C−F bond cleavage mechanisms on the sp3-hybridized carbon centers can be primarily categorized into three types: Lewis acids promoted F atom elimination to generate carbocation intermediates; nucleophilic substitution with metal or carbon nucleophiles supported by the activation of C−F bonds by coordination of Lewis acids; and the cleavage of C−F bonds via a single electron transfer. The characteristic features of alkyl fluorides, in comparison with other (pseudo)halides as promising electrophilic coupling counterparts, are also discussed. 相似文献
69.
Dr. Pablo Pinacho Dr. Donatella Loru Dr. Tatjana Šumanovac Dr. Marina Šekutor Prof. Dr. Melanie Schnell 《Chemphyschem》2023,24(23):e202300561
We report on the synthesis and characterization using high-resolution rotational spectroscopy of three bulky thioethers that feature an adamantyl group connected to a sulfur atom. Detailed experimental and theoretical structures are provided and compared with the 1,1′-diadamantyl ether. In addition, we expand on previous findings concerning microsolvation of adamantyl derivatives by investigating the cluster formation between these thioethers and a water molecule. The investigation of such clusters provides valuable insights into the sulfur-centered hydrogen bonding in thioethers with increasing size and steric repulsion. 相似文献
70.
Amlan J. Kalita Namrata Gohain Abhik Bordoloi Dr. Kusum K. Bania Dr. Ankur K. Guha 《Chemphyschem》2023,24(9):e202200873
Number of bonds formed by sharing an electron pair between two atoms is not restricted to one, it can go beyond four and six is the maximum. While homopolar sextuple bond in Mo2 and W2 has been reported, such a high bond order in heteropolar diatomics has remained elusive. In the pursuit of the sextuple bond in polar diatomics, the present study depicts the existence of such multiple bonds in Rhodium-Scandium hetero-diatom based on relativistic quantum chemical calculations. The bonding comprises of three normal electron sharing covalent bonds and three dative covalent bonds. 相似文献