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71.
[reaction: see text] A series of oligo(octithienylene-diethynylene)s alternately composed of octithiophene and diacetylene units have been prepared by a random Eglinton coupling reaction among mono- and diethynyloctithiophenes. The largest compound isolated in the oligomeric series is comprised of twelve octithiophene units and eleven diacetylene units, and its molecular length reaches ca. 43 nm, which is the longest among single-component conjugated nanomolecules. 相似文献
72.
Cyril T. Langlois Tetsuo Oikawa Pascale Bayle-Guillemaud Christian Ricolleau 《Journal of nanoparticle research》2008,10(6):997-1007
CuAg core–shell nanoparticles are synthesized by ultra-high vacuum thermal evaporation. We show on this system how the Energy-Filtered
Transmission Electron Microscopy (EFTEM) technique allows one to improve the characterization by precisely pointing out the
formation of core–shell arrangements in bimetallic nanoparticle assemblies. A criterion to measure the shell thickness from
EFTEM images on unique core–shell nanoparticles is defined, that can be used for core–shell nanoparticles of any sizes, with
shell thicknesses over 1 nm. It is based on the intensity variation along a line drawn across a core–shell nanoparticle on
a EFTEM image. This criterion has been validated by a close comparison of the shell thickness measurements performed in this
work and the ones obtained by acoustic micro-Raman spectroscopy. Using this criterion, we report a strong correlation between
the size of the Cu cores and the formation of the core–shell arrangements in the nanoparticle assembly studied in this work.
The influence of the Cu core shape is also evidenced. The characterisation of such systems using High Resolution TEM (HRTEM)
is also discussed. 相似文献
73.
Tetsuo Nakamura 《Proceedings of the American Mathematical Society》1999,127(6):1589-1595
Let be an elliptic curve over a number field such that
and let denote the number of roots of unity in . Ross proposed a question: Is isogenous over to an elliptic curve such that is cyclic of order dividing ? A counter-example of this question is given. We show that is isogenous to such that . In case has complex multiplication and , we obtain certain criteria whether or not is isogenous to such that .
and let denote the number of roots of unity in . Ross proposed a question: Is isogenous over to an elliptic curve such that is cyclic of order dividing ? A counter-example of this question is given. We show that is isogenous to such that . In case has complex multiplication and , we obtain certain criteria whether or not is isogenous to such that .
74.
75.
Tetsuo Kanamoto Anagnostis E. Zachariades Roger S. Porter 《Journal of Polymer Science.Polymer Physics》1982,20(8):1485-1496
The aliphatic polyamides nylon 6 and 6,6 have been cold drawn by using the new concept of reversible plasticization with NH3. Two aspects were investigated: the effect of NH3 plasticization on the stress-strain behavior of nylon 6,6, and the extent of NH3 absorption as determined by x-ray analysis for the structurally simpler nylon 6. X-ray analysis shows that ammonia is absorbed preferentially by the amorphous phase and that the plasticization has a significant effect on the unit-cell orientation, the small-angle void scattering, and the interplanar spacings between sheets of hydrogen-bonded chains. The effect of plasticization was seen in the lower yield stress, the higher draw ratio (up to 8X) and tensile modulus (10 GPa) not attainable with unplasticized specimens. 相似文献
76.
Tetsuo Kodama 《Archiv der Mathematik》1971,22(1):271-274
Ohne ZusammenfassungThe author acknowledges support received from the National Research Council of Canada, Grant A-7210.Herrn. Prof. E.Lamprecht und Herrn Dr. H.Mathieu dankt Verfasser für ihre Anmerkungen, die zu Verbesserungen der ursprünglichen Fassung führten. 相似文献
77.
Hanaoka K Kikuchi K Kojima H Urano Y Nagano T 《Journal of the American Chemical Society》2004,126(39):12470-12476
Detection of chelatable zinc (Zn(2+)) in biological studies has attracted much attention recently, because chelatable Zn(2+) plays important roles in many biological systems. Lanthanide complexes (Eu(3+), Tb(3+), etc.) have excellent spectroscopic properties for biological applications, such as long luminescence lifetimes of the order of milliseconds, a large Stoke's shift of >200 nm, and high water solubility. Herein, we present the design and synthesis of a novel lanthanide sensor molecule, [Eu-7], for detecting Zn(2+). This europium (Eu(3+)) complex employs a quinolyl ligand as both a chromophore and an acceptor for Zn(2+). Upon addition of Zn(2+) to a solution of [Eu-7], the luminescence of Eu(3+) is strongly enhanced, with high selectivity for Zn(2+) over other biologically relevant metal cations. One of the important advantages of [Eu-7] is that this complex can be excited with longer excitation wavelengths (around 340 nm) as compared with previously reported Zn(2+)-sensitive luminescent lamthanide sensors, whose excitation wavelength is at too high an energy level for biological applications. The usefulness of [Eu-7] for monitoring Zn(2+) changes in living HeLa cells was confirmed. This novel Zn(2+)-selective luminescent lanthanide chemosensor [Eu-7]should be an excellent lead compound for the development of a range of novel luminescent lanthanide chemosensors for biological applications. 相似文献
78.
We introduce a technique for computing approximate
solutions to optimization problems. If $X$ is the set
of feasible solutions, the standard goal
of approximation algorithms is to compute $x\in X$ that is an
$\varepsilon$-approximate solution in the following sense:
$$d(x) \leq (1+\varepsilon)\, d(x^*),$$
where $x^* \in X$ is an optimal solution,
$d\colon\ X\rightarrow {\Bbb R}_{\geq 0}$ is
the optimization function to be minimized, and
$\varepsilon>0$ is an input parameter.
Our approach is first to devise algorithms that
compute pseudo $\varepsilon$-approximate solutions
satisfying the bound
$$d(x) \leq d(x_R^*) + \varepsilon R,$$
where $R>0$ is a new input parameter.
Here $x^*_R$ denotes an optimal solution in the space $X_R$ of
$R$-constrained feasible solutions. The parameter $R$ provides
a stratification of $X$ in the sense that (1) $X_R \subseteq X_{R}$ for
$R < R$ and (2) $X_R = X$ for $R$ sufficiently large.
We first describe a highly efficient scheme
for converting a pseudo $\varepsilon$-approximation
algorithm into a true $\varepsilon$-approximation algorithm.
This scheme is useful because
pseudo approximation algorithms seem to be
easier to construct than $\varepsilon$-approximation algorithms.
Another benefit is that our algorithm is
automatically precision-sensitive.
We apply our technique to two problems in robotics:
(A) Euclidean Shortest Path (3ESP), namely
the shortest path for a point robot amidst polyhedral obstacles in
three dimensions, and
(B) $d_1$-optimal motion for a rod moving amidst
planar obstacles (1ORM).
Previously, no polynomial time $\varepsilon$-approximation algorithm
for (B) was known. For (A), our new solution
is simpler than previous solutions and has
an exponentially smaller complexity in terms
of the input precision. 相似文献
79.
The cationic ruthenium catalyst (Cp*RuCl2)2/AgOTf/Ligand promotes the addition reaction of carboxylic acids across olefins without beta-hydride elimination. 相似文献
80.
Kameda T Zhao C Ashida J Asakura T 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,160(2):91-96
It is important to know the structure of silk I (Bombyx mori silk structure before spinning in the solid state) in order to understand the mechanism of fiber formation at the atomic level. In this study, 15N-dephased, 13C-observe REDOR has been carried out to determine the atomic distance of intra-molecular hydrogen bond between the 13C=O carbon of the 14th Gly residue and the 15N nitrogen of the 17th Ala residue of (AG)(6)A[1-13C]GAG[15N]AG(AG)(6) with silk I form after removal of the effect of MAS frequency on the re-coupling. The distance was determined to be 4.3A, which confirmed the intra-molecular hydrogen bonding formation between these two atomic sites. 相似文献