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111.
Martin Kaller Dipl.‐Chem. Stefan Tussetschläger Dr. Peter Fischer Priv.‐Doz. Dr. Christopher Deck Dipl.‐Chem. Angelika Baro Dr. Frank Giesselmann Prof. Dr. Sabine Laschat Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(37):9530-9542
Dibenzo[18]crown‐6 derivatives 1 with two lateral tetraalkyloxy o‐terphenyl units were prepared and converted to the corresponding complexes KX ?1 (X=halide, BF4, PF6, SCN) and NH4PF6 ?1 . Complexation was probed by MALDI‐TOF spectrometry and NMR spectroscopy. Downfield shifts of 1H NMR signals for complexes with soft anions Br, I, SCN, and PF6 indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF4 showed no or little shifts. In 13C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX ?1 (M=K, NH4), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1 . Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 °C phase widths in the case of KI ?1 , KPF6 ?1 , and NH4PF6 ?1 . For complexes KSCN ?1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase. 相似文献
112.
Angelika Kühnle 《Current Opinion in Colloid & Interface Science》2009,14(2):157-168
Self-assembly represents a promising strategy for surface functionalisation as well as creating nanostructures with well-controlled, tailor-made properties and functionality. Molecular self-assembly at solid surfaces is governed by the subtle interplay between molecule–molecule and molecule–substrate interactions that can be tuned by varying molecular building blocks, surface chemistry and structure as well as substrate temperature.In this review, basic principles behind molecular self-assembly of organic molecules on metal surfaces will be discussed. Controlling these formation principles allows for creating a wide variety of different molecular surface structures ranging from well-defined clusters, quasi one-dimensional rows to ordered, two-dimensional overlayers. An impressive number of studies exist, demonstrating the ability of molecular self-assembly to create these different structural motifs in a predictable manner by tuning the molecular building blocks as well as the metallic substrate.Here, the multitude of different surface structures of the natural amino acid cysteine on two different gold surfaces observed with scanning tunnelling microscopy will be reviewed. Cysteine on Au(110)-(1×2) represents a model system illustrating the formation of all the above mentioned structural motifs without changing the molecular building blocks or the substrate surface. The only parameters in this system are substrate temperature and molecular coverage, controlling both the molecular adsorption state (physisorption versus chemisorption) and molecular surface mobility. By tuning the adsorption state and the molecular mobility, distinctly different molecular structures are formed, exemplifying the variety of structural motifs that can be achieved by molecular self-assembly. 相似文献
113.
Robert Lindner Dr. Philipp Rahe Dr. Markus Kittelmann Prof. Dr. André Gourdon Dr. Ralf Bechstein Prof. Dr. Angelika Kühnle 《Angewandte Chemie (International ed. in English)》2014,53(30):7952-7955
A substrate‐guided photochemical reaction of C60 fullerenes on calcite, a bulk insulator, investigated by non‐contact atomic force microscopy is presented. The success of the covalent linkage is evident from a shortening of the intermolecular distances, which is clearly expressed by the disappearance of the moiré pattern. Furthermore, UV/Vis spectroscopy and mass spectrometry measurements carried out on thick films demonstrate the ability of our setup for initiating the photoinduced reaction. The irradiation of C60 results in well‐oriented covalently linked domains. The orientation of these domains is dictated by the lattice dimensions of the underlying calcite substrate. Using the lattice mismatch to deliberately steer the direction of the chemical reaction is expected to constitute a general design principle for on‐surface synthesis. This work thus provides a strategy for controlled fabrication of oriented, covalent networks on bulk insulators. 相似文献
114.
Abstract
Oil-in-water emulsions can be stabilized by solid particles. These so-called Pickering emulsions are regularly used in many technological applications. Here we describe the efficiency of sol–gel-synthesized anatase nanoparticles with a diameter of 6 nm in stabilizing emulsions. Key parameters were the surface charge of the particles—depending on pH and salt concentration—and their contact angle—depending on the surface groups and the polarity of the oil phase. The effect of these properties on the stability of the emulsions was investigated. The sol–gel nanoparticles were most efficient in stabilizing emulsions at pH 3 (depending on the salt and particle concentration). Highly apolar oil phases (cyclohexane, n-hexane) were required to obtain stable emulsions with the investigated system and addition of salt or hydrophobic coupling molecules in the oil phase, such as long alkyl chain containing phosphonates, increased the stability of the emulsions. 相似文献115.
Ján Derco Andreja Žgajnar Gotvajn Jana Zagorc-Končan Beáta Almásiová Angelika Kassai 《Chemical Papers》2010,64(2):237-245
Kinetics and efficiency of Fenton’s and ozonation processes for the pretreatment of two landfill leachates (fresh and mature)
resulting from municipal waste disposal were studied. Both samples presented high organic load, high toxicity and low biodegradability.
These were the reasons why oxidative treatment was proposed. Fresh and mature leachate showed different behaviors in the oxidation
experiments. The final extents of removal were attained in comparable time intervals in both oxidation systems. Maximal removal
of organics by the Fenton’s oxidation reached more than 50 % according to COD. Zero or first order kinetics were found the
best to describe the organic components (in terms of COD and DOC) removal by the Fenton’s oxidation for both landfill leachates.
Higher reaction rate values of the Fenton’s oxidation were achieved with fresh leachate samples. The efficiency of initial
organics removal with ozone was about 70 % for mature leachate, while in case of the fresh one only 41 % of COD were removed.
The best fits of COD and DOC experimental data from oxidation of fresh and mature leachates were obtained by a combined kinetic
model. No significant improvement of the biodegradability of landfill leachates was achieved using these treatment procedures.
Regarding toxicity, ozonation showed to be more effective than the Fenton’s oxidation. Advanced oxidation experiments confirmed
that the Fenton’s oxidation and ozonation are comparable oxidative treatment techniques for the reduction of organic pollution
in the investigated municipal landfill leachates. However, neither of them is effective enough to be used as a pretreatment
method followed by biological treatment. 相似文献
116.
Schmidt F Lueking A Nordhoff E Gobom J Klose J Seitz H Egelhofer V Eickhoff H Lehrach H Cahill DJ 《Electrophoresis》2002,23(4):621-625
We describe the technical feasibility and methodology to characterize a protein by a minimal set of structural information generated by matrix assisted laser desorption/ionization (MALDI)-mass spectrometry, termed a "minimal protein Identifier" (MPI). MPIs can be determined for proteins from two-dimensional gels and recombinant proteins and can be used to compare and identify proteins from these sources. 相似文献
117.
For about 500 pesticides, the sensitivity of a benchtop high-resolution mass spectrometer using the Orbitrap for mass separation was compared to that of a widely used (low-resolution) tandem mass spectrometer. Both instruments were coupled to LC and used electrospray ionization. The selectivity of the Orbitrap in the full-scan acquisition mode without fragmentation was evaluated at a resolution of 100 000 full width at half maximum for all pesticides detectable with sufficient sensitivity. For this purpose, quasimolecular ions were extracted within 5 ppm windows from total ion chromatograms of two types of extracts of cucumber, lemon, wheat flour, raisin, and tea. In each of the obtained reconstructed ion chromatograms (individual chromatograms for 500 pesticides, each pesticide in 10 different extracts) the sum of signals not arising from the analyte was used to get a measure on selectivity. In addition, the target analyte list was checked for ions of similar mass. The influence of matrix on the ability to detect low concentrations of fortified pesticides was also studied, with the help of spiked extracts. This part of the survey tested whether analyte peaks were lost because of insufficient mass resolution or an early closing C-Trap (used to control the ion current into the Orbitrap). Finally, the stability of the ion ratio [M+H]+/[M+Na]+ was tested, which may be helpful to confirm the identity of an analyte. 相似文献
118.
Xingchao Dai Sven Adomeit Jabor Rabeah Carsten Kreyenschulte Angelika Brückner Hongli Wang Feng Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5305-5309
Glycolic acid (GA), as important building block of biodegradable polymers, has been synthesized for the first time in excellent yields at room temperature by selective oxidation of 1,3‐dihyroxyacetone (DHA) using a cheap supported Cu/Al2O3 catalyst with single active CuII species. By combining EPR spin‐trapping and operando ATR‐IR experiments, different mechanisms for the co‐synthesis of GA, formates, and formamides have been derived, in which .OH radicals formed from H2O2 by a Fenton‐like reaction play a key role. 相似文献
119.
Daniela Hendea Sabine Laschat Angelika Baro Wolfgang Frey 《Helvetica chimica acta》2006,89(9):1894-1909
N‐Boc‐protected L ‐proline ( 6 ) was converted into the bicyclic lactim ether (8aS)‐6,7,8,8a‐tetrahydro‐1‐methoxypyrrolo[1,2‐a]pyrazin‐4(3H)‐one ( 5 ) in four steps (Scheme 1). Deprotonation with LDA or LHMDS and subsequent alkylation resulted in the diastereoisomeric products cis‐ and trans‐ 9 . The diastereoselectivity was mainly dependent on the electrophile. Whereas small alkyl halides gave preferably cis‐ 9 , sterically more‐demanding alkyl halides resulted in cis/trans mixtures. Electrophiles bearing a π‐system favored the trans‐products 9 . Some isolated cis‐ and trans‐lactim ethers 9 were converted to the corresponding diketopiperazines cis‐ and trans‐ 10 by acid hydrolysis. The structures and configurations of several compounds were confirmed by NMR and NOE experiments, as well as by X‐ray crystallography (Figs. 1–4). 相似文献
120.
Schumann CA Dörrenhaus A Franzke J Lampen P Dittrich PS Manz A Roos PH 《Analytical and bioanalytical chemistry》2008,392(6):1159-1166
To understand molecular networking at the cellular level, analyses of processes and effects at the single-cell level are most
appropriate. Usual biochemical or molecular biological analyses are based on integrated signals of numerous cells which differ,
however, in their expression and activity profiles. Here we show that it is possible to determine different types of properties
of individual cells by means of a specifically designed microfluidic device. As part of investigations to characterize the
human urothelial cell line 5637 as a potential model system for studies of toxic and carcinogenic effects on urothelial cells,
we use this cell line to assign cytochrome P450 activity, and expression of the enzymes involved, to individual cells. It
is shown that the cell population is very heterogeneous with respect to the extent and kinetics of CYP1A1-dependent ethoxyresorufin
O-deethylase (EROD). This is also true for the cells’ CYP1A1 protein content. With some exceptions, the EROD activity largely
coincides with the presence of CYP1A1 protein in the cells. The results obtained with the microfluidic device are promising
and open up new perspectives with regard to multi-property determinations in individual cells and to studies focusing on the
biochemical and molecular heterogeneity of cells.
Figure Formation of fluorescent resorufin from ethoxyresorufin by cytochrome P450 activity in urothelial cells attached within the
chamber of a microfluidic device 相似文献