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991.
[reaction: see text] A fully substrate controlled stereoselective route to construct cis-hexahydronaphthalene 4 is described starting from nonracemic butenolide 6. The key step is an exo-selective transannular Diels-Alder reaction (TADA) of tetraene 5, whose intrinsic constraint allows selective formation of one stereodefined product. Compound 4 is a key intermediate in the synthesis of the novel antibiotic branimycin (1). 相似文献
992.
Vladimir I. Bogachev Nicolai V. Krylov Michael Rckner 《Journal de Mathématiques Pures et Appliquées》2006,85(6):743-757
We consider elliptic equations of the form L*μ=ν for measures on . The membership of solutions in the Sobolev classes is established under appropriate conditions on the coefficients of L. Bounds of the form (x)CΦ(x)−1 for the corresponding densities are obtained. 相似文献
993.
New effective approach to the synthesis of a wide variety of C-2 nitro or aminophenyl substituted quinolines was reported
using diverse intermediate 4-(2-oxopyrrolinidyl-1)-tetrahydroquinolines that were prepared by a three component imino Diels-Alder
reaction was reported. The key aromatisation process occurs cleanly with the loss of the 2-oxopyrrolinidyl-1 fragment. 相似文献
994.
Let (X m+1, g) be a globally hyperbolic spacetime with Cauchy surface diffeomorphic to an open subset of ${\mathbb{R}^{m}}Let (X
m+1, g) be a globally hyperbolic spacetime with Cauchy surface diffeomorphic to an open subset of
\mathbbRm{\mathbb{R}^{m}} . The Legendrian Low conjecture formulated by Natário and Tod says that two events x, y ? X{x, y \in X} are causally related if and only if the Legendrian link of spheres
\mathfrakSx, \mathfrakSy{{\mathfrak{S}_x,\,\mathfrak{S}_y}} whose points are light geodesics passing through x and y is non-trivial in the contact manifold of all light geodesics in X. The Low conjecture says that for m = 2 the events x, y are causally related if and only if
\mathfrakSx, \mathfrakSy{{\mathfrak{S}_x,\,\mathfrak{S}_y}} is non-trivial as a topological link. We prove the Low and the Legendrian Low conjectures. We also show that similar statements
hold for any globally hyperbolic (X
m+1, g) such that a cover of its Cauchy surface is diffeomorphic to an open domain in
\mathbbRm{\mathbb{R}^{m}} . 相似文献
995.
The article gives constructions of disjoint 5‐designs obtained from permutation groups and extremal self‐dual codes. Several new simple 5‐designs are found with parameters that were left open in the table of 5‐designs given in (G. B. Khosrovshahi and R. Laue, t‐Designs with t⩾3, in “Handbook of Combinatorial Designs”, 2nd edn, C. J. Colbourn and J. H. Dinitz (Editors), Chapman & Hall/CRC, Boca Raton, FL, 2007, pp. 79–101), namely, 5−(v, k, λ) designs with (v, k, λ)=(18, 8, 2m) (m=6, 9), (19, 9, 7m) (m=6, 9), (24, 9, 6m) (m=3, 4, 5), (25, 9, 30), (25, 10, 24m) (m=4, 5), (26, 10, 126), (30, 12, 440), (32, 6, 3m) (m=2, 3, 4), (33, 7, 84), and (36, 12, 45n) for 2⩽n⩽17. These results imply that a simple 5−(v, k, λ) design with (v, k)=(24, 9), (25, 9), (26, 10), (32, 6), or (33, 7) exists for all admissible values of λ. © 2010 Wiley Periodicals, Inc. J Combin Designs 18: 305–317, 2010 相似文献
996.
Let X and Y be two smooth Deligne-Mumford stacks and consider a pair of functions f: X → $
\mathbb{A}^1
$
\mathbb{A}^1
, g:Y → $
\mathbb{A}^1
$
\mathbb{A}^1
. Assuming that there exists a complex of sheaves on X × $
\mathbb{A}^1
$
\mathbb{A}^1
Y which induces an equivalence of D
b
(X) and D
b
(Y), we show that there is also an equivalence of the singular derived categories of the fibers f
−1(0) and g
−1(0). We apply this statement in the setting of McKay correspondence, and generalize a theorem of Orlov on the derived category
of a Calabi-Yau hypersurface in a weighted projective space, to products of Calabi-Yau hypersurfaces in simplicial toric varieties
with nef anticanonical class. 相似文献
997.
Vladimir I. Arnold 《Functional Analysis and Other Mathematics》2010,3(1):91-96
The Gibbs phenomenon is described for the Fourier series of a function at its jump, the function being defined along the finite circle ?/p?.The phenomenon consists in the fact, that the jump of the truncated Fourier series is greater, than that of the original function (being approximately 1+1/p times greater). 相似文献
998.
Vladimir Gurvich 《Discrete Applied Mathematics》2010,158(14):1496-302
Consider an electrical circuit, each edge e of which is an isotropic conductor with a monomial conductivity function . In this formula, ye is the potential difference and current in e, while μe is the resistance of e; furthermore, r and s are two strictly positive real parameters common for all edges. In particular, the case r=s=1 corresponds to the standard Ohm’s law.In 1987, Gvishiani and Gurvich [A.D. Gvishiani, V.A. Gurvich, Metric and ultrametric spaces of resistances, in: Communications of the Moscow Mathematical Society, Russian Math. Surveys 42 (6 (258)) (1987) 235-236] proved that, for every two nodes a,b of the circuit, the effective resistance μa,b is well-defined and for every three nodes a,b,c the inequality holds. It obviously implies the standard triangle inequality μa,b≤μa,c+μc,b whenever s≥r. For the case s=r=1, these results were rediscovered in the 1990s. Now, after 23 years, I venture to reproduce the proof of the original result for the following reasons:
- •
- It is more general than just the case r=s=1 and one can get several interesting metric and ultrametric spaces playing with parameters r and s. In particular, (i) the effective Ohm resistance, (ii) the length of a shortest path, (iii) the inverse width of a bottleneck path, and (iv) the inverse capacity (maximum flow per unit time) between any pair of terminals a and b provide four examples of the resistance distances μa,b that can be obtained from the above model by the following limit transitions: (i) r(t)=s(t)≡1, (ii) r(t)=s(t)→∞, (iii) r(t)≡1,s(t)→∞, and (iv) r(t)→0,s(t)≡1, as t→∞. In all four cases the limits μa,b=limt→∞μa,b(t) exist for all pairs a,b and the metric inequality μa,b≤μa,c+μc,b holds for all triplets a,b,c, since s(t)≥r(t) for any sufficiently large t. Moreover, the stronger ultrametric inequality μa,b≤max(μa,c,μc,b) holds for all triplets a,b,c in examples (iii) and (iv), since in these two cases s(t)/r(t)→∞, as t→∞.
- •
- Communications of the Moscow Math. Soc. in Russ. Math. Surveys were (and still are) strictly limited to two pages; the present paper is much more detailed.Although a translation in English of the Russ. Math. Surveys is available, it is not free in the web and not that easy to find.
- •
- The last but not least: priority.
999.
We formulate the multiperiod, distribution-free perishable inventory problem as a problem of prediction with expert advice and apply an online learning method (the Weak Aggregating Algorithm) to solve it. We show that the asymptotic average performance of this method is as good as that of any time-dependent stocking rule in a given parametric class. 相似文献
1000.
We study pairs of structures, such as the Poisson-Nijenhuis structures, on the tangent bundle of a manifold or, more generally,
on a Lie algebroid or a Courant algebroid. These composite structures are defined by two of the following, a closed 2-form,
a Poisson bivector or a Nijenhuis tensor, with suitable compatibility assumptions. We establish the relationships between
PN-, P
Ω- and Ω
N-structures. We then show that the non-degenerate Monge-Ampère structures on 2-dimensional manifolds satisfying an integrability
condition provide numerous examples of such structures, while in the case of 3-dimensional manifolds, such Monge-Ampère operators
give rise to generalized complex structures or generalized product structures on the cotangent bundle of the manifold. 相似文献