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排序方式: 共有244条查询结果,搜索用时 46 毫秒
71.
Nathaniel L. Dominique Isabel M. Jensen Gurkiran Kaur Chandler Q. Kotseos Dr. William C. Boggess Prof. David M. Jenkins Prof. Jon P. Camden 《Angewandte Chemie (International ed. in English)》2023,62(21):e202219182
The widespread application of laser desorption/ionization mass spectrometry (LDI-MS) highlights the need for a bright and multiplexable labeling platform. While ligand-capped Au nanoparticles (AuNPs) have emerged as a promising LDI-MS contrast agent, the predominant thiol ligands suffer from low ion yields and extensive fragmentation. In this work, we develop a N-heterocyclic carbene (NHC) ligand platform that enhances AuNP LDI-MS performance. NHC scaffolds are tuned to generate barcoded AuNPs which, when benchmarked against thiol-AuNPs, are bright mass tags and form unfragmented ions in high yield. To illustrate the transformative potential of NHC ligands, the mass tags were employed in three orthogonal applications: monitoring a bioconjugation reaction, performing multiplexed imaging, and storing and reading encoded information. These results demonstrate that NHC-nanoparticle systems are an ideal platform for LDI-MS and greatly broaden the scope of nanoparticle contrast agents. 相似文献
72.
Air and water free solid-phase synthesis of thiol stabilized au nanoparticles with anchored, recyclable dendrimer templates 总被引:1,自引:0,他引:1
Gilbertson JD Vijayaraghavan G Stevenson KJ Chandler BD 《Langmuir : the ACS journal of surfaces and colloids》2007,23(22):11239-11245
Solid-phase synthetic templates for Au nanoparticles were developed using Merrifield resins and polyamidoamine (PAMAM) dendrimers. This synthetic scheme affords the opportunity to prepare metal nanoparticles in the absence of air and water, and it does not necessitate phase transfer agents that can be difficult to remove in subsequent steps. Amine-terminated generation 5 PAMAM (G5NH2) dendrimers were grafted to anhydride functionalized polystyrene resin beads and alkylated with 1,2-epoxydodecane to produce G5C12anch. The anchored dendrimers bound both CoII and AuIII salts from toluene solutions at ratios comparable to those of solution phase alkyl-terminated PAMAM dendrimers. The encapsulated AuIII salts could be reduced with NaBH4 to produce anchored dendrimer encapsulated nanoparticles (DENs). Treatment of the anchored DENs with decanethiol in toluene extracted the Au nanoparticles from the dendrimers as monolayer protected clusters (MPCs). After a brief NaCN etch, the anchored dendrimers were readily recycled and a subsequent synthesis of decanethiol Au MPCs was performed with comparable MPC yield and particle size distribution. 相似文献
73.
With molecular dynamics simulations of a fluid mixture of classical particles interacting with pairwise additive Weeks-Chandler-Andersen potentials, we consider the time series of particle displacements and thereby determine the distributions for local persistence times and local exchange times. These basic characterizations of glassy dynamics are studied over a range of supercooled conditions and were shown to have behaviors, most notably decoupling, similar to those found in kinetically constrained lattice models of structural glasses. Implications are noted. 相似文献
74.
Bhasker Paliwal William B. Lawrimore Mei Q. Chandler Mark F. Horstemeyer 《哲学杂志》2013,93(15):1179-1208
AbstractWe study interfacial debonding of several representative structures of polyvinyl alcohol (PVA)/pyrophillite-clay systems – both gallery-interface (polymer/clay interface in the interlayer region containing polymer between clay layers stacked parallel to each other) and matrix-interphase (polymer/clay interphase-region when individual clay layers are well separated and dispersed in the polymer matrix) – using molecular dynamics simulations, while explicitly accounting for shearing/sliding (i.e. Mode-II) deformation mode. Ten nanocomposite geometries (five 2-D periodic structures for tension and five 1-D periodic structures for shearing) were constructed to quantify the structure-property relations by varying the number density of polymer chains, length of polymer chains and model dimensions related to the interface deformation. The results were subsequently mapped into a cohesive traction–separation law, including evaluation of peak traction and work of separation that are used to characterise the interface load transfer for larger length scale micromechanical models. Results suggest that under a crack nucleation opening mode (i.e. Mode-I), the matrix-interphase exhibits noticeably greater strength and a greater work of separation compared to the gallery-interface; however, they were similar under the shearing/sliding mode of deformation. When compared to shearing/sliding, the tensile peak opening mode stresses were considerably greater but the displacement at the peak stress, the displacement at the final failure and the work of separation were considerably lower. Results also suggest that PVA/clay nanocomposites with higher degree of exfoliation compared with nanocomposites with higher clay-intercalation can potentially display higher strength under tension-dominated loading for a given clay volume fraction. 相似文献
75.
Kerry J. GoodworthAnne-Cécile Hervé Evangelos StavropoulosGwénaelle Hervé Isabel Casades Alison M. HillGordon G. Weingarten Ricardo E. TasconM. Joseph Colston Helen C. Hailes 《Tetrahedron》2011,67(2):373-382
A series of large-ringed calix[6,7,8]arene analogues have been synthesised and their affect against Mycobacterium tuberculosis in vivo established. In general, when p-phenylcalixarenes and tert-butylcalixarenes were not functionalised at the lower rim, low biological activities were observed. However on going from partially to fully lower rim pegylated calixarenes the anti-mycobacterial properties improved. The addition of cyanopropoxy groups at the lower rim gave rise to low activities, whereas the addition of acetate moieties interestingly had pro-TB effects. Two upper rim sulfonated calixarenes showed promising properties. In the course of this work, a high yielding procedure to synthesise p-phenylcalix[7]arene was also established. 相似文献
76.
de Rooy SL Das S Li M El-Zahab B Jordan A Lodes R Weber A Chandler L Baker GA Warner IM 《The journal of physical chemistry. C, Nanomaterials and interfaces》2012,116(14):8251-8260
Groups of uniform materials based on organic salts (GUMBOS), derived from thiacarbocyanine (TC)-based dyes with increasing methyne chain lengths, were prepared through a single-step metathesis reaction between the iodide form of the TC dye and lithium bis(perfluoroethylsulfonyl)imide as the lipophilic anion source. Ionic self-assembly of these fluorescent hydrophobic GUMBOS resulted in aqueous dispersions of one-dimensional micro-and nano-scale molecular aggregates. Blended binary and ternary aggregates containing multiple TC GUMBOS were also prepared. These nanostructures exhibited a variety of aspect ratios, affording tunable F?rster resonance energy transfer (FRET) and aggregation-dependent spectroscopic properties. 相似文献
77.
B. F. Parsons K. E. Strecker D. W. Chandler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):15-20
In our previous work we investigated electronically non-adiabatic effects in
using crossed molecular beam scattering
coupled with velocity mapped ion imaging. The prior experiments placed
limits on the cross-section for electronically non-adiabatic spin-orbit
excitation
and electronically non-adiabatic spin-orbit
quenching
.
In the present work, we investigate
electronically non-adiabatic spin-orbit quenching for
which is the required first step for the
reaction of Cl* to produce ground state HCl+H products. In these
experiments we collide Cl (2P) with H2 at a series of fixed
collision energies using a crossed molecular beam machine with velocity
mapped ion imaging detection. Through an analysis of our ion images, we
determine the fraction of electronically adiabatic scattering in
Cl* +H2, which allows us to place limits on the cross-section for
electronically non-adiabatic scattering or quenching. We determine the following
quenching cross-sections σ quench(2.1 kcal/mol) = 26 ±
21 ?2, σ quench(4.0 kcal/mol) = 21 ±
49 ?2, and σ quench(5.6 kcal/mol) = 14 ±
41 ?2. 相似文献
78.
C. M. Sands H. W. Chandler I. A. Guz Y. A. Zhuk 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(2):161-173
This paper demonstrates that, at extreme levels of kinematic hardening, the traditional formulation of the Bodner–Partom model
can produce anomalous results. The reasons for this anomalous behaviour are explained, and a reformulated version of the model
is presented. This reformulation extends the range of the model to include levels of kinematic hardening that may be problematic
in the traditional formulation. The formulation of the model is adjusted so as to retain the rate dependency of the original
Bodner–Partom model; and to permit the values of the material parameters used with the traditional formulation to be re-used
with the extended model—with the exception only of the hardening coefficients which become dimensionless constants holding
different numerical values. This revised formulation also imposes associated flow, thereby ensuring phase consistency between
stress and plastic strain during non-proportional loading. In this way, the anomalies are removed, the range and stability
of the model is increased, and all the advantages and important features of the Bodner–Partom model are retained. 相似文献
79.
The two-Hilbert-space theory of scattering is reviewed with particular reference to its application to nonrelativistic multichannel
quantum- mechanical scattering theory. In Part I the abstract assumptions of the theory are collected, transition operators
(both on- and off-energy-shell) are defined, the dynamical equations that determine the off-shell transition operators are
presented and their real-energy limits examined, and the convergence of sequences of approximate transition operators is established.
A section on how to incorporate group symmetries into the formalism reports new work. The material of Part I is relevant to
a variety of both classical and quantum scattering systems. In Part II attention is directed specifically to N-body nonrelativistic quantum scattering systems in which the particles interact via short-range pair potentials. A method
of constructing approximate transition operators is presented and shown to satisfy all the abstract assumptions of Part I.
The dynamical equations that determine the half-on-shell approximate transition operators are shown to be coupled one-dimensional
integral equations that have compact kernels and unique solutions when considered as operators on a Hilbert space of H?lder
continuous functions. Moreover, the on-shell parts of those approximate transition amplitudes are shown to converge to the
exact on-shell amplitudes as the order of the approximation increases. Detailed formulas for the kernels of the integral equations
are written down for systems of particles that are distinguishable and for systems containing identical particles. Finally,
some important open problems are described.
Received July 2, 1999; accepted in final form October 27, 1999 相似文献
80.
F. Becker W. Korten F. Hannachi P. Paris N. Buforn C. Chandler M. Houry H. Hübel A. Jansen Y. Le Coz C.F. Liang A. Lopez-Martens R. Lucas E. Mergel P. H. G. Schönwasser C. Theisen 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):103-105
The atomic nucleus 74Kr has been investigated using combined conversion-electron (CE) and γ-ray spectroscopy. In order to confirm the existence
of the expected low-lying isomeric 0+
2 state, the possibility of an electric-monopole (E0) decay to the ground state was examined. The observation of an E0 transition
at 508 keV allowed the determination of the mixing between coexisting prolate and oblate shapes.
Received: 16 November 1998 相似文献