全文获取类型
收费全文 | 19810篇 |
免费 | 488篇 |
国内免费 | 437篇 |
专业分类
化学 | 3774篇 |
晶体学 | 933篇 |
力学 | 383篇 |
综合类 | 44篇 |
数学 | 11933篇 |
物理学 | 3668篇 |
出版年
2023年 | 55篇 |
2022年 | 72篇 |
2021年 | 125篇 |
2020年 | 159篇 |
2019年 | 369篇 |
2018年 | 394篇 |
2017年 | 268篇 |
2016年 | 327篇 |
2015年 | 324篇 |
2014年 | 597篇 |
2013年 | 1358篇 |
2012年 | 525篇 |
2011年 | 1578篇 |
2010年 | 1388篇 |
2009年 | 1279篇 |
2008年 | 1376篇 |
2007年 | 1355篇 |
2006年 | 1018篇 |
2005年 | 891篇 |
2004年 | 785篇 |
2003年 | 598篇 |
2002年 | 615篇 |
2001年 | 411篇 |
2000年 | 384篇 |
1999年 | 360篇 |
1998年 | 374篇 |
1997年 | 290篇 |
1996年 | 333篇 |
1995年 | 336篇 |
1994年 | 318篇 |
1993年 | 244篇 |
1992年 | 248篇 |
1991年 | 173篇 |
1990年 | 183篇 |
1989年 | 171篇 |
1988年 | 106篇 |
1987年 | 124篇 |
1986年 | 89篇 |
1985年 | 158篇 |
1984年 | 114篇 |
1983年 | 68篇 |
1982年 | 91篇 |
1981年 | 121篇 |
1980年 | 106篇 |
1979年 | 61篇 |
1978年 | 108篇 |
1977年 | 91篇 |
1976年 | 90篇 |
1975年 | 39篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Marco Masi Maria Chiara Zonno Alessio Cimmino Pierluigi Reveglia Alexander Berestetskiy Angela Boari 《Natural product research》2018,32(13):1537-1547
Ambrosia artemisiifolia L. is responsible for serious allergies induced on humans. Different approaches for its control were proposed during the COST Action FA1203 “Sustainable management of Ambrosia artemisiifolia in Europe” (SMARTER). Fungal secondary metabolites often show potential herbicidal activity. Three phytotoxins were purified from the fungal culture filtrates of Colletotrichum gloeosporioides, isolated from infected leaves of A. artemisiifolia. They were identified by spectroscopic and chemical methods as colletochlorin A, orcinol and tyrosol (1, 2 and 3). The absolute configuration 6’R to colletochlorin A was assigned for the first time applying the advanced Mosher’s method. When assayed by leaf-puncture on A. artemisiifolia only 1 caused the appearance of large necrosis. The same symptoms were also induced by 1 on ambrosia plantlets associated with plant wilting. On Lemna minor, colletochlorin A caused a clear fronds browning, with a total reduction in chlorophyll content. 相似文献
22.
Charles Almeida Aline V. Andrade Rosa M. Miró-Roig 《Journal of Pure and Applied Algebra》2019,223(4):1817-1831
Let be a minimal monomial Togliatti system of forms of degree d. In [4], Mezzetti and Miró-Roig proved that the minimal number of generators of lies in the interval . In this paper, we prove that for and , the integer values in cannot be realized as the number of minimal generators of a minimal monomial Togliatti system. We classify minimal monomial Togliatti systems of forms of degree d with or 3n (i.e. with the minimal number of generators reaching the border of the non-existence interval). Finally, we prove that for , and there exists a minimal monomial Togliatti system of forms of degree d with . 相似文献
23.
Jun Jason Luo 《Mathematische Nachrichten》2019,292(5):1032-1042
Recently Lipschitz equivalence of self‐similar sets on has been studied extensively in the literature. However for self‐affine sets the problem is more awkward and there are very few results. In this paper, we introduce a w‐Lipschitz equivalence by repacing the Euclidean norm with a pseudo‐norm w. Under the open set condition, we prove that any two totally disconnected integral self‐affine sets with a common matrix are w‐Lipschitz equivalent if and only if their digit sets have equal cardinality. The main methods used are the technique of pseudo‐norm and Gromov hyperbolic graph theory on iterated function systems. 相似文献
24.
For wide classes of locally convex spaces, in particular, for the space of continuous real‐valued functions on a Tychonoff space X equipped with the pointwise topology, we characterize the existence of a fundamental bounded resolution (i.e., an increasing family of bounded sets indexed by the irrationals which swallows the bounded sets). These facts together with some results from Grothendieck's theory of ‐spaces have led us to introduce quasi‐ ‐spaces, a class of locally convex spaces containing ‐spaces that preserves subspaces, countable direct sums and countable products. Regular ‐spaces as well as their strong duals are quasi‐ ‐spaces. Hence the space of distributions provides a concrete example of a quasi‐ ‐space not being a ‐space. We show that has a fundamental bounded resolution if and only if is a quasi‐ ‐space if and only if the strong dual of is a quasi‐ ‐space if and only if X is countable. If X is metrizable, then is a quasi‐ ‐space if and only if X is a σ‐compact Polish space. 相似文献
25.
Balázs Gerencsér 《Stochastic Processes and their Applications》2019,129(9):3570-3584
The paper concerns a particular example of the Gibbs sampler and its mixing efficiency. Coordinates of a point are rerandomized in the unit square to approach a stationary distribution with density proportional to for with some large parameter .Diaconis conjectured the mixing time of this process to be which we confirm in this paper. This improves on the currently known estimate. 相似文献
26.
Some cases of the LFED Conjecture, proposed by the second author [15], for certain integral domains are proved. In particular, the LFED Conjecture is completely established for the field of fractions of the polynomial algebra , the formal power series algebra and the Laurent formal power series algebra , where denotes n commutative free variables and k a field of characteristic zero. Furthermore, the relation between the LFED Conjecture and the Duistermaat–van der Kallen Theorem [3] is also discussed and emphasized. 相似文献
27.
Martin Costabel 《Mathematische Nachrichten》2019,292(10):2165-2173
We construct a bounded C1 domain Ω in for which the regularity for the Dirichlet and Neumann problems for the Laplacian cannot be improved, that is, there exists f in such that the solution of in Ω and either on or on is contained in but not in for any . An analogous result holds for Sobolev spaces with . 相似文献
28.
Sarika Goyal 《Mathematische Nachrichten》2019,292(10):2189-2202
In this article, we study the eigenvalues of p‐fractional Hardy operator where , , , and Ω is an unbounded domain in with Lipschitz boundary containing 0. The weight function V may change sign and may have singular points. We also show that the least positive eigenvalue is simple and it is uniquely associated to a nonnegative eigenfunction. Moreover, we proved that there exists a sequence of eigenvalues as . 相似文献
29.
This paper will deal with an anisotropic area-preserving flow which keeps the convexity of the evolving curve and the limiting curve converges to a homothety of a symmetric smooth strictly convex plane curve. 相似文献
30.
Explicit and partly sharp estimates are given of integrals over the square of Bessel functions with an integrable weight which can be singular at the origin. They are uniform with respect to the order of the Bessel functions and provide explicit bounds for some smoothing estimates as well as for the L2 restrictions of Fourier transforms onto spheres in which are independent of the radius of the sphere. For more special weights these restrictions are shown to be Hölder continuous with a Hölder constant having this independence as well. To illustrate the use of these results a uniform resolvent estimate of the free Dirac operator with mass in dimensions is derived. 相似文献