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131.
Olga Bienemann Ann‐Kathrin Froin Ines dos Santos Vieira Ramona Wortmann Alexander Hoffmann Prof. Dr. Sonja Herres‐Pawlis 《无机化学与普通化学杂志》2012,638(11):1683-1690
This contribution reports the synthesis of the novel tetradentate bisguanidine ligand 2′,2′‐[ethane‐1, 2‐diylbis(methylazanediyl)]bis(ethane‐2, 1‐diyl)bis(1, 1, 3, 3‐tetramethylguanidine) ( L1 , TMG2dmtrien), which combines two weak amine and two strong guanidine donor functions. Two new copper(II) complexes were isolated and structurally characterized as complexes [Cu(TMG2dmtrien)][Br]2 · 3MeCN ( C1 [Br]2 · 3MeCN) and [Cu(TMG2dmtrien)][Cl]2 · 3MeCN ( C2 [Cl]2 · 3MeCN). The cations C1 and C2 [Cu(TMG2dmtrien)]2+ show a square‐planar coordination environment and are chiral with both enantiomers being observed in the unit cell. We investigated the application of L1 in copper‐mediated styrene ATRP. L1 shows with CuBr and PEBr as initiator a high polymerization activity according to the polymerization rate. First order kinetics confirm the living character of the polymerization. However, the deviation of molecular weights from theoretical molecular weights and the broad molecular weight distributions hint for a low controlled ATRP. The ATRP with further copper(I) salts {CuCl, [Cu(MeCN)4]BF4 and [Cu(MeCN)4]PF6} and PECl and PEBr as initiators were investigated as well. Herein the use of [Cu(MeCN)4]PF6 with PECl led to promising results. 相似文献
132.
Daniel Crespy Kathrin Friedemann Ana‐Maria Popa 《Macromolecular rapid communications》2012,33(23):1978-1995
Solution‐, melt‐, and co‐axial electrospinning are well‐known methods for producing nano‐ and microfibers. The electrospinning of colloids (or colloid‐electrospinning) is a new field that offers the possibility to elaborate multicompartment nanomaterials. However, the presence of colloids in the electrospinning feed further complicates theoretical predictions in a system that is dependent on chemical, physical, and process parameters. Herein, we give a summary of recent important results and discuss the perspectives of electrospinning of colloids for the synthesis and characterization of multicompartment fibers. 相似文献
133.
134.
Dr. Xin Chen Malte Kohring Dr. M'hamed Assebban Dr. Bartłomiej Tywoniuk Dr. Cian Bartlam Narine Moses Badlyan Prof. Janina Maultzsch Prof. Georg S. Duesberg Prof. Heiko B. Weber Dr. Kathrin C. Knirsch Prof. Andreas Hirsch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13117-13122
The development of an efficient method to patterning 2D MoS2 into a desired topographic structure is of particular importance to bridge the way towards the ultimate device. Herein, we demonstrate a patterning strategy by combining the electron beam lithography with the surface covalent functionalization. This strategy allows us to generate delicate MoS2 ribbon patterns with a minimum feature size of 2 μm in a high throughput rate. The patterned monolayer MoS2 domain consists of a spatially well-defined heterophase homojunction and alternately distributed surface characteristics, which holds great interest for further exploration of MoS2 based devices. 相似文献
135.
136.
Dr. Kathrin Heckenbichler MSc Anna Schweiger Lea Alexandra Brandner Dr. Alexandra Binter MSc Marina Toplak Prof. Dr. Peter Macheroux Prof. Dr. Karl Gruber Prof. Dr. Rolf Breinbauer 《Angewandte Chemie (International ed. in English)》2018,57(24):7240-7244
Ene reductases from the Old Yellow Enzyme (OYE) family reduce the C=C double bond in α,β‐unsaturated compounds bearing an electron‐withdrawing group, for example, a carbonyl group. This asymmetric reduction has been exploited for biocatalysis. Going beyond its canonical function, we show that members of this enzyme family can also catalyze the formation of C?C bonds. α,β‐Unsaturated aldehydes and ketones containing an additional electrophilic group undergo reductive cyclization. Mechanistically, the two‐electron‐reduced enzyme cofactor FMN delivers a hydride to generate an enolate intermediate, which reacts with the internal electrophile. Single‐site replacement of a crucial Tyr residue with a non‐protic Phe or Trp favored the cyclization over the natural reduction reaction. The new transformation enabled the enantioselective synthesis of chiral cyclopropanes in up to >99 % ee. 相似文献
137.
The structures and stability of the designed PNP pincer amido M(NO)2(PNP) and amino HM(NO)2(PNHP) complexes [M = V, Nb, and Ta, PNP = N(CH2CH2P(isopropyl)2)2, PNHP = HN(CH2CH2P(isopropyl)2)2] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-CN, Ph-CHNH, Ph-CHNH-Ph, Ph-CHNCH2Ph, Ph-CCH, Ph-CHCH2, Ph-CHO, and Ph-COCH3, the reaction prefers either a two-step or one-step mechanism for the hydridic MH and protonic NH transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges. 相似文献
138.
Prof. Dr. Karl Kratzl Friedrich W. Vierhapper Erich Tengler 《Monatshefte für Chemie / Chemical Monthly》1975,106(2):321-332
Bicreosol, labelled with14C in ring position 1.1-, 4.4-, 5.5-, in the methyl- or in the methoxy substituent was oxygenated in 0.25m-NaOH. Isolation of low molecular fragments and determination of their specific activities indicate that at least two fragmentation pathways take place simultaneously: one with ring opening between the oxygen substituted carbon atoms, and one in which the bond between these atoms is not cleaved.
Meinem Lehrer, Herrn Prof. Dr. Dr. h.c. mult.H. Mark, zum 80. Geburtstag gewidmet.
3. Mitt.:K. Kratzl, P. Claus undf. W. Vierhapper, Mh. Chem.103, 100 (1972). 相似文献
Meinem Lehrer, Herrn Prof. Dr. Dr. h.c. mult.H. Mark, zum 80. Geburtstag gewidmet.
3. Mitt.:K. Kratzl, P. Claus undf. W. Vierhapper, Mh. Chem.103, 100 (1972). 相似文献
139.
Although proteases are capable of synthesizing peptide bonds, they are not proficient at peptide fragment ligation. Further manipulations are needed to shift the native enzyme activity from the cleavage to the synthesis of peptides. This account reports on the synthetic potential of nonactivatable trypsinogen and zymogen-like enzymes designed to minimize proteolytic side reactions during peptide synthesis. 相似文献
140.
Zusammenfassung Die Synthese zweier Glukoside, des Vanillinsäurediäthylamid--d-glukosids und des Vanillinsäurepiperidid--d-glukosids wird beschrieben, wobei das erste auf zwei verschiedenen Wegen dargestellt wurde.Infolge des Kristallwassergehaltes der Glukosidacetate und freien Glukoside und deren großer Empfindlichkeit beim Trocknen wurde die Konstitution durch Vergleich des Ultrarotabsorptionsspektrums der auf verschiedenen Wegen gewonnenen Substanzen sowie durch chemischen Abbau sichergestellt.Das Vanillinsäurediäthylamid--d-glukosid zeigte auch in der 300-fachen Menge der wirksamen Dosis des Aglukons keine analeptische Wirkung.I. Mitt. siehe Mh. Chem.83, 18 (1952). 相似文献