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691.
导出了扇形截面杆扭转问题偏微分方程的差分线法常微分方程组, 并解析求解了该方程组,
得到了扭转应力函数的半解析解, 计算了扭转应力及扭转刚度. 计算过程中, 用追赶法计算
常微分方程组的特解, 用公式计算三对角矩阵的特征值与特征向量, 利用实对阵矩阵的特征
向量相互正交的特性避免矩阵求逆计算, 利用复化梯形公式计算扭转刚度. 整个求解过程在
角度方向离散微分方程和用复化梯形公式进行面积积分时引入了误差, 其他求解过程是精确
的. 计算结果与已有结果进行了对比, 显示了算法的正确性. 该算法对工程中扇形截面扭
转杆的设计有一定的实用价值. 相似文献
692.
Michael E. Picollelli 《Discrete Mathematics》2011,(20):2113
A 3-simplex is a collection of four sets A1,…,A4 with empty intersection such that any three of them have nonempty intersection. We show that the maximum size of a set system on n elements without a 3-simplex is for all n≥1, with equality only achieved by the family of sets containing a given element or of size at most 2. This extends a result of Keevash and Mubayi, who showed the conclusion for n sufficiently large. 相似文献
693.
It was shown in Bíró et al. (2001) [7] that every cyclic subgroup C of the circle group T admits a characterizing sequence (un) of integers in the sense that unx→0 for some x∈T iff x∈C. More generally, for a subgroup H of a topological (abelian) group G one can define:
- (a)
- g(H) to be the set of all elements x of G such that unx→0 in G for all sequences (un) of integers such that unh→0 in G for all h∈H;
- (b)
- H to be g-closed if H=g(H).
694.
695.
696.
We establish the existence of smooth stable manifolds in Banach spaces for sufficiently small perturbations of a new type of dichotomy that we call nonuniform polynomial dichotomy. This new dichotomy is more restrictive in the “nonuniform part” but allow the “uniform part” to obey a polynomial law instead of an exponential (more restrictive) law. We consider two families of perturbations. For one of the families we obtain local Lipschitz stable manifolds and for the other family, assuming more restrictive conditions on the perturbations and its derivatives, we obtain C1 global stable manifolds. Finally we present an example of a family of nonuniform polynomial dichotomies and apply our results to obtain stable manifolds for some perturbations of this family. 相似文献
697.
We establish the robustness under sufficiently small linear perturbations of nonuniform exponential trichotomies defined by linear equations x′=A(t)x in Banach spaces. We also establish the continuous dependence on the perturbation of the constants in the notion of trichotomy. We consider both trichotomies in semi-infinite intervals and trichotomies in R. 相似文献
698.
We study an invariant of a 3-manifold which consists of Reidemeister torsion for linear representations which pass through a finite group. We show a Dehn surgery formula on this invariant and compute that of a Seifert manifold over S2. As a consequence we obtain a necessary condition for a result of Dehn surgery along a knot to be Seifert fibered, which can be applied even in a case where abelian Reidemeister torsion gives no information. 相似文献
699.
Arkadiusz Jadczyk 《Advances in Applied Clifford Algebras》2009,19(1):63-82
In relativistic quantum mechanics wave functions of particles satisfy field equations that have initial data on a space-like
hypersurface. We propose a dual field theory of “wavicles” that have their initial data on a time-like worldline. Propagation
of such fields is superluminal, even though the Hilbert space of the solutions carries a unitary representation of the Poincaré
group of mass zero. We call the objects described by these field equations “Kairons”. The paper builds the field equations
in a general relativistic framework, allowing for a torsion. Kairon fields are section of a vector bundle over space-time.
The bundle has infinite-dimensional fibres. 相似文献
700.
S.C. Ulhoa 《Annalen der Physik》2012,524(5):273-278
The paper is devoted to an explanation of the accelerated rate of expansion of the Universe. Usually the acceleration of the Universe, which is described by FRW metric, is due to dark energy. It is shown that this effect may be considered as a manifestation of torsion tensor for a flat Universe in the realm of Teleparallel gravity. An observer with radial field velocity obey Hubble's Law. As a consequence it is established that this is radial acceleration in a flat Universe. In Eq. (35) the acceleration is written in terms of the deceleration parameter, the Hubble’s constant and the proper distance. This may be interpreted as an acceleration of the Universe. 相似文献