全文获取类型
收费全文 | 3157篇 |
免费 | 568篇 |
国内免费 | 197篇 |
专业分类
化学 | 583篇 |
晶体学 | 2篇 |
力学 | 192篇 |
综合类 | 48篇 |
数学 | 1542篇 |
物理学 | 426篇 |
无线电 | 1129篇 |
出版年
2024年 | 10篇 |
2023年 | 49篇 |
2022年 | 76篇 |
2021年 | 84篇 |
2020年 | 117篇 |
2019年 | 105篇 |
2018年 | 131篇 |
2017年 | 161篇 |
2016年 | 153篇 |
2015年 | 166篇 |
2014年 | 216篇 |
2013年 | 279篇 |
2012年 | 215篇 |
2011年 | 198篇 |
2010年 | 158篇 |
2009年 | 182篇 |
2008年 | 198篇 |
2007年 | 188篇 |
2006年 | 174篇 |
2005年 | 179篇 |
2004年 | 123篇 |
2003年 | 114篇 |
2002年 | 99篇 |
2001年 | 83篇 |
2000年 | 87篇 |
1999年 | 60篇 |
1998年 | 74篇 |
1997年 | 49篇 |
1996年 | 38篇 |
1995年 | 27篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有3922条查询结果,搜索用时 234 毫秒
931.
本文研究了D4 型量子包络代数的Gelfand-Kirillov 维数的计算问题. 利用文献[1] 中给出的Gelfand-Kirillov 维数的计算方法和文献[2] 中给出的D4 型量子包络代数的Groebner-Shirshov 基计算了D4型量子包络代数的Gelfand-Kirillov 维数, 得到的主要结果是D4 型量子包络代数的Gelfand-Kirillov 维数为28. 希望此结果为计算Dn型量子包络代数的Gelfand-Kirillov 维数提供一些思路. 相似文献
932.
933.
934.
Giampietro Allasia 《Numerical Functional Analysis & Optimization》2013,34(3):237-254
A class of cardinal basis functions is proposed in order to achieve a generalization to Banach spaces of Hermite-Birkhoff interpolation on arbitrarily distributed data. First, a constructive characterization of the class of cardinal basis functions is given. Then, the interpolation problem is solved by using a suitable combination of such functions and Taylor-Fréchet expansions. The performance of the obtained interpolants is improved by applying a localizing scheme, and the corresponding approximation error is estimated. A noteworthy case in Hilbert spaces and a numerical test comparing the Hermite-Birkhoff and Lagrange interpolants complete the presentation. 相似文献
935.
936.
Michal Pitoňák Dr. Pavel Neogrády Dr. Jiří Černý Dr. Stefan Grimme Prof. Pavel Hobza Prof. 《Chemphyschem》2009,10(1):282-289
Scaled MP3 interaction energies calculated as a sum of MP2/CBS (complete basis set limit) interaction energies and scaled third‐order energy contributions obtained in small or medium size basis sets agree very closely with the estimated CCSD(T)/CBS interaction energies for the 22 H‐bonded, dispersion‐controlled and mixed non‐covalent complexes from the S22 data set. Performance of this so‐called MP2.5 (third‐order scaling factor of 0.5) method has also been tested for 33 nucleic acid base pairs and two stacked conformers of porphine dimer. In all the test cases, performance of the MP2.5 method was shown to be superior to the scaled spin‐component MP2 based methods, e.g. SCS–MP2, SCSN–MP2 and SCS(MI)–MP2. In particular, a very balanced treatment of hydrogen‐bonded compared to stacked complexes is achieved with MP2.5. The main advantage of the approach is that it employs only a single empirical parameter and is thus biased by two rigorously defined, asymptotically correct ab‐initio methods, MP2 and MP3. The method is proposed as an accurate but computationally feasible alternative to CCSD(T) for the computation of the properties of various kinds of non‐covalently bound systems. 相似文献
937.
Orthogonal design has been used to the optimization of separation and determination of two active components in traditional Chinese medicines by capillary electrophoresis. The concentration of phosphate, applied voltage, organic modifier content and buffer pH were selected as variable parameters. Their different effects on peak resolution were studied by the experimental design method. Optimized separation conditions were obtained and successfully applied to the separation and determination of aconitine and hypaconitine in Aconitum medicinal herbs. Good separation was achieved within 7 min using a buffer system composed of 20 mmol L−1 phosphate and 35% acetonitrile at pH 9.5. The applied voltage was 14 kV and the detection was set at 235 nm. In addition, a radial basis function neural network with a “4-18-1” structure was developed based on the experimental results of orthogonal design and uniform design, and was applied to the prediction of peak resolution of the two active components under the optimum separation conditions given by orthogonal design. The predicted results were in good agreement with the experimental values, indicating that radial basis function neural network is a potential way for the selection of separation conditions in capillary electrophoresis. 相似文献
938.
We provide a geometric realization of the crystal B(∞) for quantum generalized Kac-Moody algebras in terms of the irreducible components of certain Lagrangian subvarieties in the representation spaces of a quiver. 相似文献
939.
Let , and for k=0,1,…, denote the orthonormalized Jacobi polynomial of degree k. We discuss the construction of a matrix H so that there exist positive constants c, c1, depending only on H, α, and β such that Specializing to the case of Chebyshev polynomials, , we apply this theory to obtain a construction of an exponentially localized polynomial basis for the corresponding L2 space. 相似文献
940.
Stochastic portfolio specific mortality and the quantification of mortality basis risk 总被引:1,自引:0,他引:1
In the last decade a vast literature on stochastic mortality models has been developed. However, these models are often not directly applicable to insurance portfolios because:
- (a) For insurers and pension funds it is more relevant to model mortality rates measured in insured amounts instead of measured in the number of policies.
- (b) Often there is not enough insurance portfolio specific mortality data available to fit such stochastic mortality models reliably.