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排序方式: 共有3024条查询结果,搜索用时 46 毫秒
121.
Kazuo Umemura Ryo Hamano Hiroaki Komatsu Takashi Ikuno Eko Siswoyo 《Molecules (Basel, Switzerland)》2021,26(10)
Solubilization of carbon nanotubes (CNTs) is a fundamental technique for the use of CNTs and their conjugates as nanodevices and nanobiodevices. In this work, we demonstrate the preparation of CNT suspensions with “green” detergents made from coconuts and bamboo as fundamental research in CNT nanotechnology. Single-walled CNTs (SWNTs) with a few carboxylic acid groups (3–5%) and pristine multi-walled CNTs (MWNTs) were mixed in each detergent solution and sonicated with a bath-type sonicator. The prepared suspensions were characterized using absorbance spectroscopy, scanning electron microscopy, and Raman spectroscopy. Among the eight combinations of CNTs and detergents (two types of CNTs and four detergents, including sodium dodecyl sulfate (SDS) as the standard), SWNTs/MWNTs were well dispersed in all combinations except the combination of the MWNTs and the bamboo detergent. The stability of the suspensions prepared with coconut detergents was better than that prepared with SDS. Because the efficiency of the bamboo detergents against the MWNTs differed significantly from that against the SWNTs, the natural detergent might be useful for separating CNTs. Our results revealed that the use of the “green” detergents had the advantage of dispersing CNTs as well as SDS. 相似文献
122.
This paper investigates finite-stretching corrections
to the classical Milner-Witten-Cates theory for semi-dilute
polymer brushes in a good solvent. The dominant correction to the
free energy originates from an entropic repulsion caused by the
impenetrability of the grafting surface, which produces a
depletion of segments extending a distance μ∝L-1
from the substrate, where L is the classical brush height. The
next most important correction is associated with the
translational entropy of the chain ends, which creates the
well-known tail where a small population of chains extend beyond
the classical brush height by a distance ξ∝L-1/3.
The validity of these corrections is confirmed by quantitative
comparison with numerical self-consistent field theory. 相似文献
123.
É. Biémont A. Ellmann P. Lundin S. Mannervik L.-O. Norlin P. Palmeri P. Quinet D. Rostohar P. Royen P. Schef 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):211-219
The difficulty associated with an accurate determination of transition rates for forbidden lines in lowly ionized heavy elements
is illustrated in the case of Nd II. We have investigated the radiative decay of the low-lying metastable levels in Nd+ including the two levels
K11/2 and
I13/2. In these two particular cases, using different theoretical approaches, we find that the decay is dominated by the M1 channels
but that the E2 contributions are of the same order of magnitude. These levels have also been studied experimentally by lifetime
measurements with the heavy ion storage ring CRYRING of Stockholm University. The difficulties encountered when performing
such experiments are underlined and discussed. 相似文献
124.
L. Ye 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):413-416
We propose two schemes for generating a four-atom cluster state in a thermal
cavity. With the assistant of a strong classical field the
photon-number-dependent parts in the effective Hamiltonian are canceled.
Thus the schemes are insensitive to the thermal field. The schemes can also
be used to generate the cluster state for the trapped ions in thermal
motion. 相似文献
125.
M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):289-303
We reconsider the procedure
developed for atoms a few decades ago by Girardeau, in the light of
the composite-boson many-body theory we recently proposed. The
Girardeau's procedure makes use of a so called “unitary Fock-Tani
operator” which in an exact way transforms one composite bound
atom into one bosonic “ideal” atom. When used to transform the
Hamiltonian of interacting atoms, this operator generates an extremely
complex set of effective scatterings between ideal bosonic atoms and free
fermions which makes the transformed Hamiltonian impossible to write
explicitly, in this way forcing to some truncation. The scatterings
restricted to the ideal-atom subspace are shown to read rather simply in
terms of the two elementary scatterings of the composite-boson many-body
theory, namely, the energy-like direct interaction scatterings
— which describe fermion interactions without fermion exchange — and
the dimensionless Pauli scatterings — which describe fermion exchanges
without fermion interaction. We here show
that, due to a fundamental difference in the scalar products of
elementary and composite bosons, the Hamiltonian expectation
value for N ground state atoms
obtained by staying in the ideal-atom subspace and working
with boson operators only, differ from the exact ones even for N = 2 and
a mapping to the ideal-atom subspace performed, as advocated, from
the fully antisymmetrical atomic state, i.e., the state which obeys the
so-called “subsidiary condition”. This shows that, within this
Girardeau's procedure too, we cannot completely forget the underlying
fermionic components of the particles if we want to correctly describe
their interactions. 相似文献
126.
Simone Pilon Steen Ingemann Jørgensen Prof. Dr. Jan H. van Maarseveen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2310-2314
After earlier unsuccessful attempts, this work reports the application of covalent templating for the synthesis of mechanically interlocked molecules (MiMs) bearing no supramolecular recognition sites. Two linear strands were covalently connected in a perpendicular fashion by a central ketal linkage. After subsequent attachment of the first strand to a template via temporary benzylic linkages, the second was linked to the template in a backfolding macrocyclization. The resulting pseudo[1]rotaxane structure was successfully converted to a [2]catenane via a second macrocyclization and cleavage of the ketal and temporary linkages. 相似文献
127.
Dr. Changfeng Hong Takahiro Otabe Saki Matsumoto Dr. Chikara Dohno Dr. Asako Murata Dr. Masaki Hagihara Prof. Dr. Kazuhiko Nakatani 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5282-5287
The hairpin structure is one of the most common secondary structures in RNA and holds a central position in the stream of RNA folding from a non‐structured RNA to structurally complex and functional ribonucleoproteins. Since the RNA secondary structure is strongly correlated to the function and can be modulated by the binding of small molecules, we have investigated the modulation of RNA folding by a ligand‐assisted formation of loop–loop complexes of two RNA hairpin loops. With a ligand (NCT6), designed based on the ligand binding to the G–G mismatches in double‐stranded DNA, we successfully demonstrated the formation of both inter‐ and intra‐molecular NCT6‐assisted complex of two RNA hairpin loops. NCT6 selectively bound to the two hairpin loops containing (CGG)3 in the loop region. Native polyacrylamide gel electrophoresis analysis of two doubly‐labeled RNA hairpin loops clearly showed the formation of intermolecular NCT6‐assisted loop–loop complex. Förster resonance energy‐transfer studies of RNA constructs containing two hairpin loops, in which each hairpin was labeled with Alexa488 and Cy3 fluorophores, showed the conformational change of the RNA constructs upon binding of NCT6. These experimental data showed that NCT6 simultaneously bound to two hairpin RNAs at the loop region, and can induce the conformational change of the RNA molecule. These data strongly support that NCT6 functions as molecular glue for two hairpin RNAs. 相似文献
128.
Synthesis and Photophysical Properties of Multichromophoric Carbonyl‐Bridged Triarylamines
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Natalie Hammer Dr. Richard Hildner Dr. Milan Kivala Prof. Dr. Jürgen Köhler Prof. Hans‐Werner Schmidt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11708-11718
The synthesis and photophysical properties of two novel multichromophoric compounds is presented. Their molecular design comprises a carbonyl‐bridged triarylamine core and either naphthalimides or 4‐(5‐hexyl‐2,2′‐bithiophene)naphthalimides as second chromophore in the periphery. The lateral chromophores are attached to the core via an amide linkage and a short alkyl spacer. The synthetic approach demonstrates a straightforward functionalization strategy for carbonyl‐bridged triarylamines. Steady‐state and time‐resolved spectroscopic investigations of these compounds, in combination with three reference compounds, provide clear evidence for energy transfer in both multichromophoric compounds. The direction of the energy transfer depends on the lateral chromophore used. Furthermore, the compound bearing the lateral 4‐(bithiophene)naphthaimides is capable of forming fluorescent gels at very low concentrations in the sub‐millimolar regime whilst retaining its energy transfer properties. 相似文献
129.
Cong‐Li Gao Xiang Li Dr. Yuan‐Zhi Tan Xin‐Zhou Wu Dr. Qianyan Zhang Prof.Dr. Su‐Yuan Xie Prof. Rong‐Bin Huang 《Angewandte Chemie (International ed. in English)》2014,53(30):7853-7855
Previously reported fused‐pentagon fullerenes stabilized by exohedral derivatization do not share the same cage with those stabilized by endohedral encapsulation. Herein we report the crystallographic identification of #4348C66Cl10, which has the same cage as that of previously reported Sc2@C66. According to the geometrical data of #4348C66Cl10, both strain relief (at the fused pentagons) and local aromaticity (on the remaining sp2‐hybrided carbon framework) contribute to the exohedral stabilization of this long‐sought 66 carbon atom cage. 相似文献
130.
Robert W. Hicklin Tania L. López Silva Prof. Paul J. Hergenrother 《Angewandte Chemie (International ed. in English)》2014,53(37):9880-9883
Fenestranes are an intriguing class of highly strained molecules possessing a quaternary carbon with bonds that deviate from the canonical tetrahedral geometry. Herein we report the discovery that the natural product pleuromutilin can be used as a structurally complex starting material for the synthesis of a series of bridged cis,cis,cis,cis‐[4.5.5.5]‐ and cis,cis,cis,cis‐[4.5.7.5]oxafenestranes through a carbocation rearrangement cascade. X‐ray crystallographic analysis of several cis,cis,cis,cis‐[4.5.5.5]oxafenestranes shows a significant planarization of the central tetracoordinate carbon atom and demonstrates the influence of bridgehead substituents and bridging rings on planarity. 相似文献