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排序方式: 共有1763条查询结果,搜索用时 15 毫秒
31.
Sarkar S Sarkar B Chanda N Kar S Mobin SM Fiedler J Kaim W Lahiri GK 《Inorganic chemistry》2005,44(17):6092-6099
The complex framework [Ru(tpy)(dpk)]2+ has been used to study the generation and reactivity of the nitrosyl complex [Ru(tpy)(dpk)(NO)]3+ ([4]3+). Stepwise conversion of the chloro complex [Ru(tpy)(dpk)(Cl)]+ ([1]+) via [Ru(tpy)(dpk)(CH3CN)]2+ ([2]2+) and the nitro compound [Ru(tpy)(dpk)(NO2)]+ ([3]+) yielded [4]3+; all four complexes were structurally characterized as perchlorates. Electrochemical oxidation and reduction was investigated as a function of the monodentate ligand as was the IR and UV-vis spectroscopic response (absorption/emission). The kinetics of the conversion [4]3+/[3]+ in aqueous environment were also studied. Two-step reduction of [4]3+ was monitored via EPR, UV-vis, and IR (nu(NO), nu(CO)) spectroelectrochemistry to confirm the {RuNO}7 configuration of [4]2+ and to exhibit a relatively intense band at 505 nm for [4]+, attributed to a ligand-to-ligand transition originating from bound NO-. 相似文献
32.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
33.
Inside Cover: Expanding the Scope of Chelating Triazolylidenes: Mesoionic Carbenes from the 1,5‐“Click”‐Regioisomer and Catalytic Synthesis of Secondary Amines from Nitroarenes (Chem. Eur. J. 50/2016)
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34.
Nahar Singh Rama Devi Ramachandran Ajit Kumar Sarkar 《International journal of environmental analytical chemistry》2013,93(10):891-896
Silica is removed from fly ash sample by hydroflourination for its effective determination gravimetrically and the remaining residue is subjected to lithium tetraborate (Li2B4O7) fusion followed by dissolution in dilute nitric acid to obtain a clear solution in which elements including aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu) and zinc (Zn), have been determined by Flame Atomic Absorption Spectrometry (FAAS). Two fly ash samples analyzed by the proposed method have been received from the National Council of Cement and Building Materials (NCCBM), India (proposed CRM in future) and fly ash CRM 1633 (b) from NIST, USA. The validity of the method has been established by analyzing fly ash CRM 1633 (b) as reference standard. The standard deviation has been calculated for each measurement. 相似文献
35.
Dr. Pritam Ghosh Dr. Natalia Fridman Prof. Dr. Galia Maayan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):634-640
The construction of synthetic protein mimics is a central goal in chemistry. A known approach for achieving this goal is the self-assembly of synthetic biomimetic sequences into supramolecular structures. Obtaining different 3D structures via a simple sequence modification, however, is still challenging. Herein we present the design and synthesis of biomimetic architectures, via the self-assembly of distinct copper-peptoid duplexes. We demonstrate that changing only one non-coordinating side-chain within the peptoids—sequence-specific N-substituted glycine oligomers—leads to different supramolecular structures. Four peptoid trimers incorporating 2,2’-bipyridine and pyridine ligands, and a non-coordinating but rather a structure-directed bulky group were synthesized, and their solutions were treated with Cu2+ in a 1:1 ratio. Single-crystal X-ray analysis of the products revealed the self-assembly of each peptoid into a metallopeptoid duplex, followed by the self-assembly of multiple duplexes and their packing into a three-dimensional supramolecular architecture via hydrogen bonding and π–π interactions. Tuning the non-coordinating side-chain enables to regulate both the final structure being either a tightly packed helical rod or a nano-channel, and the pore width of the nano-channels. Importantly, all the metallopeptoids structures are stable in aqueous solution as verified by cryo-TEM measurements and supported by UV/Vis and EPR spectroscopies and by ESI-MS analysis. Thus, we could also demonstrate the selective recognition abilities of the nano-channels towards glycerol. 相似文献
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Reaction of bis-lactone embodied in the rigid tircyclo [5.2.1.02,6] decane 5 with MeLi and t-BuLi produced the novel oxa-cage compounds 9 and 11 instead of the expected ketones 6. 相似文献
40.
Philipp Rietsch Dr. Sebastian Sobottka Dr. Katrin Hoffmann Dr. Alexey A. Popov Pascal Hildebrandt Prof. Dr. Biprajit Sarkar Dr. Ute Resch-Genger Prof. Dr. Siegfried Eigler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17361-17365
Reversibly switching the light absorption of organic molecules by redox processes is of interest for applications in sensors, light harvesting, smart materials, and medical diagnostics. This work presents a symmetrical benzothiadiazole (BTD) derivative with a high fluorescence quantum yield in solution and in the crystalline state and shows by spectroelectrochemical analysis that reversible switching of UV absorption in the neutral state, to broadband Vis/NIR absorption in the 1st oxidized state, to sharp band Vis absorption in the 2nd oxidized state, is possible. For the one-electron oxidized species, formation of a delocalized radical is confirmed by electron paramagnetic resonance spectroelectrochemistry. Furthermore, our results reveal an increasing quinoidal distortion upon the 1st and 2nd oxidation, which can be used as the leitmotif for the development of BTD based redox switches. 相似文献