全文获取类型
收费全文 | 6036篇 |
免费 | 418篇 |
国内免费 | 670篇 |
专业分类
化学 | 378篇 |
晶体学 | 33篇 |
力学 | 54篇 |
综合类 | 113篇 |
数学 | 4894篇 |
物理学 | 1652篇 |
出版年
2024年 | 5篇 |
2023年 | 60篇 |
2022年 | 87篇 |
2021年 | 140篇 |
2020年 | 115篇 |
2019年 | 163篇 |
2018年 | 167篇 |
2017年 | 190篇 |
2016年 | 156篇 |
2015年 | 130篇 |
2014年 | 197篇 |
2013年 | 922篇 |
2012年 | 205篇 |
2011年 | 272篇 |
2010年 | 247篇 |
2009年 | 415篇 |
2008年 | 423篇 |
2007年 | 402篇 |
2006年 | 372篇 |
2005年 | 290篇 |
2004年 | 308篇 |
2003年 | 282篇 |
2002年 | 284篇 |
2001年 | 199篇 |
2000年 | 188篇 |
1999年 | 169篇 |
1998年 | 164篇 |
1997年 | 171篇 |
1996年 | 100篇 |
1995年 | 73篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1936年 | 5篇 |
排序方式: 共有7124条查询结果,搜索用时 31 毫秒
21.
22.
Characterizations of ( m,n )-Jordan Derivations and ( m,n )-Jordan Derivable Mappings on Some Algebras 下载免费PDF全文
Let R be a ring, M be a R-bimodule and m, n be two fixed nonnegative integers with m + n = 0. An additive mapping δ from R into M is called an(m, n)-Jordan derivation if(m +n)δ(A~2) = 2 mAδ(A) + 2nδ(A)A for every A in R. In this paper, we prove that every(m, n)-Jordan derivation with m = n from a C*-algebra into its Banach bimodule is zero. An additive mappingδ from R into M is called a(m, n)-Jordan derivable mapping at W in R if(m + n)δ(AB + BA) =2mδ(A)B + 2 mδ(B)A + 2 nAδ(B) + 2 nBδ(A) for each A and B in R with AB = BA = W. We prove that if M is a unital A-bimodule with a left(right) separating set generated algebraically by all idempotents in A, then every(m, n)-Jordan derivable mapping at zero from A into M is identical with zero. We also show that if A and B are two unital algebras, M is a faithful unital(A, B)-bimodule and U = [A M N B] is a generalized matrix algebra, then every(m, n)-Jordan derivable mapping at zero from U into itself is equal to zero. 相似文献
23.
Jordan operator algebras are norm‐closed spaces of operators on a Hilbert space with for all . In two recent papers by the authors and Neal, a theory for these spaces was developed. It was shown there that much of the theory of associative operator algebras, in particular, surprisingly much of the associative theory from several recent papers of the first author and coauthors, generalizes to Jordan operator algebras. In the present paper we complete this task, giving several results which generalize the associative case in these papers, relating to unitizations, real positivity, hereditary subalgebras, and a couple of other topics. We also solve one of the three open problems stated at the end of our earlier joint paper on Jordan operator algebras. 相似文献
24.
25.
In order to construct a class of new Turaev-braided group category with nontrivial associativity, the concept of a quasitriangular quasi-Turaev group coalgebras was recently introduced. Inside the definition, the conditions of invertibility of the R-matrix R and bijectivity of the antipode S are required. In this article, we prove that the antipode of a quasitriangular quasi-Turaev group coalgebra without the assumptions about invertibility of the antipode and R-matrix is inner, and a fortiori, bijective. As an application, we prove that for a quasitriangular quasi-Turaev group coalgebra, two conditions mentioned above are unnecessary. 相似文献
26.
27.
28.
29.
Ryoichi Doi 《Analytical letters》2019,52(10):1519-1538
Test strips and similar products are highly feasible tools for the rapid and approximate determination of chemical characteristics. Although the application of both the quantitative observation of coloration and regression modeling has recently enabled these products to become quantitative tools, their precision and accuracy may be further improved. In this study, the pseudocolor imaging of the coloration image, derivative spectrophotometry-like differentiation of the coloration values, and logarithmic conversion of the raw and derivative values were compared in terms of the precision and accuracy of the quantitative determination of corrosiveness, glucose, nitrate, and pH using the products. The best regression models for the determination were provided by the combination of pseudocolor imaging and differentiation (nitrate and pH); pseudocolor imaging, differentiation, and square-conversion (corrosiveness); or all of the techniques (glucose). When compared to the use of the original 10 raw coloration variables of red-green-blue, cyan-magenta-yellow-key black, and L*a*b* color models only, the above combinations improved the normalized mean absolute error from 14.8% to 3.09% (corrosiveness), 6.33% to 3.15% (glucose), 7.46% to 4.56% (nitrate), and 3.22% to 0.94% (pH). These achievements were largely attributed to the combination of multiple variables that have non-linear and nonmonotonic relationships with the chemical characteristics. 相似文献
30.
《Discrete Mathematics》2019,342(10):2846-2849