全文获取类型
收费全文 | 1176篇 |
免费 | 19篇 |
专业分类
化学 | 827篇 |
晶体学 | 8篇 |
力学 | 7篇 |
数学 | 83篇 |
物理学 | 270篇 |
出版年
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 46篇 |
2012年 | 31篇 |
2011年 | 71篇 |
2010年 | 39篇 |
2009年 | 32篇 |
2008年 | 49篇 |
2007年 | 64篇 |
2006年 | 50篇 |
2005年 | 40篇 |
2004年 | 47篇 |
2003年 | 54篇 |
2002年 | 37篇 |
2001年 | 33篇 |
2000年 | 21篇 |
1999年 | 20篇 |
1997年 | 29篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 16篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 15篇 |
1990年 | 23篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 30篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1966年 | 7篇 |
排序方式: 共有1195条查询结果,搜索用时 15 毫秒
101.
Sanjay Kumar Ankur Jain Yoshitsugu Kojima 《Journal of Thermal Analysis and Calorimetry》2017,128(2):721-733
This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C3A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C3A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C3A cement, the curve shows the C3S peak in advance and a high intensity of third peak attributed to C3A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements. 相似文献
102.
Takahiro Matsumoto Seikou Nakamura Naoto Kojima Tomohiro Hasei Masayuki Yamashita Tetsushi Watanabe Hisashi Matsuda 《Tetrahedron letters》2017,58(36):3574-3578
From the methanolic extract of the aerial parts of Isodon japonicus, two new ent-kaurane diterpenes, isodonterpenes I and II, were isolated together with 10 known diterpenes. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The absolute configuration of isodonterpene I was elucidated by Cu-Kα X-ray crystallographic analysis. Antimutagenic activities of the major diterpenes were evaluated by the Ames test. This study represents the first evaluation of the antimutagenic activities of ent-kaurane diterpenes. 相似文献
103.
104.
We study polynomial-type solutions of the q-Heun equation, which is related with quasi-exact solvability. The condition that the q-Heun equation has a non-zero polynomial-type solution is described by the roots of the spectral polynomial, whose variable is the accessory parameter E. We obtain sufficient conditions that the roots of the spectral polynomial are all real and distinct. We consider the ultradiscrete limit to clarify the roots of the spectral polynomial and the zeros of the polynomial-type solution of the q-Heun equation. 相似文献
105.
Kentaro Kojima 《Applied mathematics and computation》2010,217(8):4047-4050
This paper extends two existent methods, called the blockability relation and the viability relation, for simple games to compare influence of coalitions, to those for games in characteristic function form, and shows that the newly defined relations satisfy transitivity and completeness. It is shown in this paper that for every game in characteristic function form the blockability relation and the viability relation have a complementary interrelationship. 相似文献
106.
Takeshi Kojima 《Journal of Mathematical Analysis and Applications》2010,364(2):618-629
It is shown that the generalized Ornstein-Uhlenbeck operator “with potential” AΦ,G,Vu:=Δu−∇Φ⋅∇u+G⋅∇u−Vu with suitable domain generates an analytic semigroup on the weighted space Lp(RN,μ), 1<p<∞, where . The result extends the generation theorem established by Metafune-Prüss-Rhandi-Schnaubelt when V≡0 to the case where V?0, while the proof is based on their useful theorem that a class of second order elliptic operators generates an analytic semigroup on the unweighted space Lp(RN). 相似文献
107.
Hisashi Kojima 《Journal of Number Theory》2004,107(1):25-62
The purpose of this paper is to derive a generalization of Shimura's results concerning Fourier coefficients of Hilbert modular forms of half integral weight over total real number fields in the case of Hilbert-Maass wave forms over algebraic number fields by following the Shimura's method. Employing theta functions, we shall construct the Shimura correspondence Ψτ from Hilbert-Maass wave forms f of half integral weight over algebraic number fields to Hilbert-Maass wave forms of integral weight over algebraic number fields. We shall determine explicitly the Fourier coefficients of in terms of these f. Moreover, under some assumptions about f concerning the multiplicity one theorem with respect to Hecke operators, we shall establish an explicit connection between the square of Fourier coefficients of f and the central value of quadratic twisted L-series associated with the image of f. 相似文献
108.
Various conic relaxations of quadratic optimization problems in nonnegative variables for combinatorial optimization problems, such as the binary integer quadratic problem, quadratic assignment problem (QAP), and maximum stable set problem have been proposed over the years. The binary and complementarity conditions of the combinatorial optimization problems can be expressed in several ways, each of which results in different conic relaxations. For the completely positive, doubly nonnegative and semidefinite relaxations of the combinatorial optimization problems, we discuss the equivalences and differences among the relaxations by investigating the feasible regions obtained from different representations of the combinatorial condition which we propose as a generalization of the binary and complementarity condition. We also study theoretically the issue of the primal and dual nondegeneracy, the existence of an interior solution and the size of the relaxations, as a result of different representations of the combinatorial condition. These characteristics of the conic relaxations affect the numerical efficiency and stability of the solver used to solve them. We illustrate the theoretical results with numerical experiments on QAP instances solved by SDPT3, SDPNAL+ and the bisection and projection method. 相似文献
109.
Toru Kojima 《Discrete Mathematics》2008,308(7):1282-1295
The bandwidth B(G) of a graph G is the minimum of the quantity max{|f(x)-f(y)|:xy∈E(G)} taken over all proper numberings f of G. The strong product of two graphs G and H, written as G(SP)H, is the graph with vertex set V(G)×V(H) and with (u1,v1) adjacent to (u2,v2) if one of the following holds: (a) u1 and v1 are adjacent to u2 and v2 in G and H, respectively, (b) u1 is adjacent to u2 in G and v1=v2, or (c) u1=u2 and v1 is adjacent to v2 in H. In this paper, we investigate the bandwidth of the strong product of two connected graphs. Let G be a connected graph. We denote the diameter of G by D(G). Let d be a positive integer and let x,y be two vertices of G. Let denote the set of vertices v so that the distance between x and v in G is at most d. We define δd(G) as the minimum value of over all vertices x of G. Let denote the set of vertices z such that the distance between x and z in G is at most d-1 and z is adjacent to y. We denote the larger of and by . We define η(G)=1 if G is complete and η(G) as the minimum of over all pair of vertices x,y of G otherwise. Let G and H be two connected graphs. Among other results, we prove that if δD(H)(G)?B(G)D(H)+1 and B(H)=⌈(|V(H)|+η(H)-2)/D(H)⌉, then B(G(SP)H)=B(G)|V(H)|+B(H). Moreover, we show that this result determines the bandwidth of the strong product of some classes of graphs. Furthermore, we study the bandwidth of the strong product of power of paths with complete bipartite graphs. 相似文献
110.