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991.
Silicon‐Directed Rhenium‐Catalyzed Allylic Carbaminations and Oxidative Fragmentations of γ‐Silyl Allylic Alcohols 下载免费PDF全文
Dr. Sanjay W. Chavhan Dr. Matthew J. Cook 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4891-4895
A highly regioselective allylic substitution of β‐silyl allylic alcohols has been achieved that provides the branched isomer as a single product. This high level of regiocontrol is achieved through the use of a vinyl silane group that can perform a Hiyama coupling providing 1,3‐disubstituted allylic amines. An unusual oxidative fragmentation product was also observed at elevated temperature that appears to proceed by a Fleming–Tamao‐type oxidation–elimination pathway. 相似文献
992.
Ruthenium Complexes of Tripodal Ligands with Pyridine and Triazole Arms: Subtle Tuning of Thermal,Electrochemical, and Photochemical Reactivity 下载免费PDF全文
Fritz Weisser Stephan Hohloch Sebastian Plebst Dr. David Schweinfurth Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):781-793
Electrochemical and photochemical bond‐activation steps are important for a variety of chemical transformations. We present here four new complexes, [Ru(Ln)(dmso)(Cl)]PF6 ( 1 – 4 ), where Ln is a tripodal amine ligand with 4?n pyridylmethyl arms and n?1 triazolylmethyl arms. Structural comparisons show that the triazoles bind closer to the Ru center than the pyridines. For L2, two isomers (with respect to the position of the triazole arm, equatorial or axial), trans‐ 2 sym and trans‐ 2 un, could be separated and compared. The increase in the number of the triazole arms in the ligand has almost no effect on the RuII/RuIII oxidation potentials, but it increases the stability of the Ru?Sdmso bond. Hence, the oxidation waves become more reversible from trans‐ 1 to trans‐ 4 , and whereas the dmso ligand readily dissociates from trans‐ 1 upon heating or irradiation with UV light, the Ru?S bond of trans‐ 4 remains perfectly stable under the same conditions. The strength of the Ru?S bond is not only influenced by the number of triazole arms but also by their position, as evidenced by the difference in redox behavior and reactivity of the two isomers, trans‐ 2 sym and trans‐ 2 un. A mechanistic picture for the electrochemical, thermal, and photochemical bond activation is discussed with data from NMR spectroscopy, cyclic voltammetry, and spectroelectrochemistry. 相似文献
993.
用碳酸钠将硫酸钙样品中的钙沉淀为碳酸钙,释放出硫酸根,用阴离子型离子色谱仪,在40℃柱温下,以6.3 mmol/L Na HCO3–1.7 mmol/L Na2CO3缓冲盐为淋洗液,采用电导检测器测定其中硫酸根的浓度,以间接得到硫酸钙含量。实验结果表明,该法与经典的沉淀重量法测定结果相吻合,两者之间的相对误差为0.29%。样品加标回收率在96.0%~105.3%之间,测定结果的相对标准偏差为0.26%(n=6)。该方法精密度与准确度高,可快速、稳定、可靠地分析脱硫灰渣及石膏样品中的硫酸根含量。 相似文献
994.
Various approaches to the synthesis of 1,4‐dihydropyrrolo[3,2‐b]pyrroles are summarized. Many two‐ and three‐step reaction sequences have been developed, and have allowed access to a broad variety of structures, including not only the parent 1,4‐dihydropyrrolo[3,2‐b]pyrroles, but also their π‐expanded analogues. The newest approaches are critically compared with older strategies. The reactivity of these compounds is also reviewed, with special emphasis on electrophilic aromatic substitution. The synthesis of indolo[3,2‐b]indole derivatives has been the subject of intense investigation. Overall, a few interesting and ingenious approaches toward these ladder‐type heteroacenes have been proposed, reaching total yields in the region of 30 %. Finally, the optical, electrochemical, and other physicochemical properties are presented in the broader perspective of heteropentalenes. The parent 1,4‐dihydro‐pyrrolo[3,2‐b]pyrroles constitute the most electron‐rich, simple, aromatic heterocycles, and their simple derivatives and π‐expanded analogues possess strong violet, blue, or green fluorescence both in solution and in the solid state. 相似文献
995.
Dramatic Mechanistic Change in Acid‐Catalyzed Arylation of Azafulleroids Depending on their Ambident N/C Basicity: Formation of Cyclopentene Centered Pentakisadduct 下载免费PDF全文
Dr. Naohiko Ikuma Yuta Doi Koichi Fujioka Tsubasa Mikie Dr. Ken Kokubo Prof. Dr. Takumi Oshima 《化学:亚洲杂志》2014,9(11):3084-3088
Azafulleroid, amino‐bridged [5,6]‐open fullerene, has the ambident N/C basicity of the incorporated enamine moiety. Acid‐catalyzed arylation of N‐substituted azafulleroids proceeded via two types of initial N/C protonation to perform monoarylation or 1,4‐bisarylation for the N‐alkyl substituents and shuttlecock‐type pentakisarylation for the N‐phenyl substituent. The dramatic product change was explained by considering the possible mechanism as well as the DFT computational results. 相似文献
996.
《Arabian Journal of Chemistry》2014,7(6):1017-1023
New aromatic diamine monomers prepared from condensation reactions of aniline, p-chloroaniline, p-nitro aniline, p-chloro-m-nitro aniline with 4-amino-N,N-dimethylaniline (2:1) (aniline:reagent) in the presence of potassium dichromate in acidic media yielded new monomers of a highly colored violet and reddish-violet. Mechanism of the reaction of aniline with 4-amino-N,N-dimethylaniline in the presence of potassium dichromate as an oxidant is expected to proceed through nucleophilic substitution reaction, and the mechanism proceeds facilitated a nucleophilic attack of the substituted aniline ring on the –NH2 group of the reagent; through partial protonation of their –NH2 group, forming in diamine dye and their identification was confirmed by IR, 1H NMR, and CHN analyses. 相似文献
997.
General and Facial Synthesis of 2‐Amino‐5‐halogenpyrimidine‐4‐carboxylic Acids and Their Derivatives
A facile synthetic approach to 2‐amino‐5‐halogen‐pyrimidine‐4‐carboxylic acids from 5‐halogen‐2‐methylsulfonylpyrimidine‐4‐carboxylic acid by nucleophilic displacement of the methylsulfonyl group with primary and secondary aliphatic amines has been developed. The titled amino acids underwent decarboxylation, yielding 2‐amino‐5‐halogenpyrimidines. Starting from 2‐amino‐5‐chloropyrimidine‐4‐carboxylic acid chlorides, 2‐[5‐chloro‐2‐(amino)‐4‐pyrimidinyl]‐2‐oxo‐1‐(2‐pyridyl)‐ethyl cyanides were obtained in excellent yields. 相似文献
998.
In this study, we synthesized a new series of substituted aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives (6-24) in yields ranging from 42 to 70% with an interesting mechanism that involves internal nucleophilic substitution followed by an SN2-type nucleophilic substitution. First, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanone (3) was synthesized from the reaction of 5-methyl-1,3,4-thiadiazole-2-thiol (1) with 2-bromo-1-(4-chlorophenyl)ethanone (2) in the presence of potassium hydroxide. Then, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanol (4) was synthesized by a reduction reaction of this compound using NaBH4. Finally, 5-methyl-3-alkyl-1,3,4-thiadiazol-2(3H)-one derivatives (6-24), which are the target compounds, were synthesized from the reaction of this compound (4), which is a secondary alcohol with various alkyl halides (5a-n) in the presence of sodium hydride (NaH). This study presents an interesting reaction mechanism related to the synthesis of aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives that is not recorded in the literature. 相似文献
999.
The reaction of phenylglyoxal with cyclopentenylmorpholine and its arylidene derivatives leads to hydroxyalkylation products. 相似文献
1000.
The reaction rate of nucleophilic substitution can be dramatically enhanced by microwave irradiation using the ionic liquid [Bmim]BF4 as a solvent. Nucleophilic reagents (anilines, thiophenol) react with ethoxymethylene isopropylidene malonate to give corresponding products in 5–10 min in good yields. 相似文献