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61.
Tomato pericarp tissue was studied by low-field nuclear magnetic resonance (NMR) relaxometry. Two kinds of experiments were
performed to investigate the correlation between multi-exponential NMR relaxation and the subcellular compartments. The longitudinal
(T
1) versus transverse (T
2) relaxation times were first measured on fresh samples and then the transverse relaxation time was measured on samples exposed
to water stress. Four signal components were found in all experiments. The results showed that all signal components corresponded
to the water in different cell compartments, and that no signal from non-exchangeable protons was present. Moreover, we demonstrated
that NMR relaxation is suitable for the continuous monitoring of water rebalancing between subcellular compartments of plant
tissues. 相似文献
62.
63.
For a non-decreasing integer sequence a=(a1,...,an) we define La to be the set of n-tuples of integers = (1,...,n) satisfying
. This generalizes the so-called lecture hall partitions corresponding to ai=i and previously studied by the authors and by Andrews. We find sequences a such that the weight generating function for these a-lecture hall partitions has the remarkable form
In the limit when n tends to infinity, we obtain a family of identities of the kind the number of partitions of an integer m such that the quotient between consecutive parts is greater than is equal to the number of partitions of m into parts belonging to the set P, for certain real numbers and integer sets P. We then underline the connection between lecture hall partitions and Ehrhart theory and discuss some reciprocity results. 相似文献
64.
1-Decyl-2,3-dimethylimidazolium bromide (ddmimBr) has been synthesized by the reaction of 1,2-dimethylimidazole and 1-bromodecane. Micellization of ddmimBr surfactant in water (W) and water-ethanolamine (W-EA) with the weight percent of EA changing within the range 0-39.79%, has been investigated at 298.15 K. Information about the influence of the added EA on the critical micelle concentration (CMC) was obtained through density and surface tension measurements. This last provides information about the dependence of the surface excess concentration, the minimum area per surfactant molecule and the surface pressure at the CMC on the added weight percentage of organic solvent. The effect of binary aqueous mixtures of W-EA on the apparent molar volume (phi V) of the ddmimBr has been investigated. The apparent molar volume upon aggregation (Delta phi V) shows a maximum at about 15 wt% of EA, this behavior is discussed in terms of the changes of the solvent structure. Partial specific volume data, obtained by density measurements, indicate that the fraction of solvent molecules interact with the surfactant remained roughly constant. 相似文献
65.
Ha-Thi MH Penhoat M Drouin D Blanchard-Desce M Michelet V Leray I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(19):5941-5950
A series of fluorescent phosphane oxide derivatives based on diphenylphosphanoethane (DPPE) and diphenylphosphanomethane (DPPM) skeletons has been prepared by means of Grignard reactions and Sonogashira cross-couplings. The photophysical properties and the linear and nonlinear spectra of these compounds have been investigated. An edge-to-face conformation resulting in the formation of an excimer was confirmed by fluorescence lifetime measurements of these multichromophoric derivatives. Upon complexation with heavy metal ions such as Pb2+ and Cd2+, a red shift of the one- and two-photon excitation spectra was observed in the absorption and emission spectra. Furthermore, enhancement of the electron-withdrawing character of the phosphane oxide resulted in a significant enhancement of the two-photon absorption cross-section, leading to the first biphotonic Cd2+ sensors combining high affinity for Cd2+, large two-photon absorption cross-sections, and significant enhancement of the two-photon excited fluorescence in the presence of the cation. Such derivatives are highly promising for incorporation into devices for the detection of heavy metal ions in water and effluents. 相似文献
66.
Cyclizations of bicyclic amides via an intramolecular Heck reaction followed by an oxidation reaction generate tricyclic spirocyclohexadienones. From these compounds, tetracyclic ketones can be synthesized to provide useful intermediates for the synthesis of indole alkaloids. 相似文献
67.
Mongin O Porrès L Charlot M Katan C Blanchard-Desce M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(5):1481-1498
An extensive series of push-push and pull-pull derivatives was prepared from the symmetrical functionalization of an ambivalent core with conjugated rods made from arylene-vinylene or arylene-ethynylene building blocks, bearing different acceptor or donor end-groups. Their absorption and photoluminescence, as well as their two-photon-absorption (TPA) properties in the near infrared (NIR) region, were systematically investigated to derive structure-property relationships and to lay the guidelines for both spectral tuning and amplification of molecular TPA in the target region. Whatever the nature of the core or of the connectors, push-push systems were found to be more efficient than pull-pull systems, and planarization of the core (fluorene versus biphenyl) always leads to an increase in the TPA cross sections. In contrast, increasing the conjugation length as well as replacement of a phenylene moiety by a thienylene moiety in the conjugated rods did not necessarily lead to increased TPA responses. The present study also demonstrated that the topology of the conjugated rods can dramatically influence the TPA properties. This is of particular interest in terms of molecular engineering for specific applications, as both TPA properties and photoluminescence characteristics can be considerably affected. Thus, it becomes possible to optimize the transparency/TPA and fluorescence/TPA efficiency trade-offs for optical limiting in the red-NIR region (700-900 nm) and for two-photon-excited fluorescence (TPEF) microscopy applications, respectively. 相似文献
68.
Nerambourg N Werts MH Charlot M Blanchard-Desce M 《Langmuir : the ACS journal of surfaces and colloids》2007,23(10):5563-5570
The insertion of fluorescently labeled thiols into the protecting self-assembled monolayer on the surface of gold nanoparticles through place exchange reactions and the effects of this insertion on the photophysical properties of the fluorophores are investigated. Analysis of solution-phase fluorescence data using a dynamic equilibrium model yields the equilibrium constant for the place exchange equilibrium, as well as the relative fluorescence brightness of the fluorophores on the particle surface. In all cases we find a significant quenching of the fluorescence, and potential reasons for this quenching are discussed. In the case of these relatively small particles (4.5 nm diameter), the quenching appears to be mainly related to enhanced nonradiative deactivation pathways. The place exchange equilibrium constant reveals a reduced affinity of the fluorescently labeled thiols for insertion into the nonfluorescent alkylthiol monolayer (K(eq) approximately 0.2) compared to unlabeled alkylthiols. 相似文献
69.
Swarupa Chatterjee Bram A. Schotpoort Thieme Elbert Jeroen J. L. M. Cornelissen Mireille M. A. E. Claessens Christian Blum 《Molecules (Basel, Switzerland)》2021,26(19)
Supramolecular protein complexes are the corner stone of biological processes; they are essential for many biological functions. Unraveling the interactions responsible for the (dis)assembly of these complexes is required to understand nature and to exploit such systems in future applications. Virus capsids are well-defined assemblies of hundreds of proteins and form the outer shell of non-enveloped viruses. Due to their potential as a drug carriers or nano-reactors and the need for virus inactivation strategies, assessing the intactness of virus capsids is of great interest. Current methods to evaluate the (dis)assembly of these protein assemblies are experimentally demanding in terms of instrumentation, expertise and time. Here we investigate a new strategy to monitor the disassembly of fluorescently labeled virus capsids. To monitor surfactant-induced capsid disassembly, we exploit the complex photophysical interplay between multiple fluorophores conjugated to capsid proteins. The disassembly of the capsid changes the photophysical interactions between the fluorophores, and this can be spectrally monitored. The presented data show that this low complexity method can be used to study and monitor the disassembly of supramolecular protein complexes like virus capsids. However, the range of labeling densities that is suitable for this assay is surprisingly narrow. 相似文献
70.