全文获取类型
收费全文 | 212篇 |
免费 | 11篇 |
国内免费 | 16篇 |
专业分类
化学 | 46篇 |
力学 | 14篇 |
综合类 | 7篇 |
数学 | 68篇 |
物理学 | 104篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 21篇 |
2008年 | 9篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 15 毫秒
1.
The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH2, and DINP−NO2) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate .OH and provides free radicals for the photodegradation of microplastics in the environment. 相似文献
2.
For approximate wave functions, we prove the theorem that there is a one‐to‐one correspondence between the constraints of normalization and of the Fermi–Coulomb and Coulomb hole charge sum rules at each electron position. This correspondence is surprising in light of the fact that normalization depends on the probability of finding an electron at some position. In contrast, the Fermi–Coulomb hole sum rule depends on the probability of two electrons staying apart because of correlations due to the Pauli exclusion principle and Coulomb repulsion, while the Coulomb hole sum rule depends on Coulomb repulsion. We demonstrate the theorem for the ground state of the He atom by the use of two different approximate wave functions that are functionals rather than functions. The first of these wave function functionals is constructed to satisfy the constraint of normalization, and the second that of the Coulomb hole sum rule for each electron position. Each is then shown to satisfy the other corresponding sum rule. The significance of the theorem for the construction of approximate “exchange‐correlation” and “correlation” energy functionals of density functional theory is also discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
3.
线性方程组通解并行数值方法 总被引:4,自引:0,他引:4
1预备知识 线性方程组消息传递MIMD算法是20世纪90年代至今的活跃课题,但尚无此问题 的通用有效算法发表.用!.}.}表示矩阵列分块划分,记AX=b为[AI司.定理1、2是文 {l]、[s]成果综述和推广. 定理i[‘]设有线性方程组!e}己l,e〔尺”“m,d〔R”“‘,rank(e)=r.当且仅当rank(! 相似文献
4.
We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics
expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not
change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction
significantly. 相似文献
5.
Steven J. Sepanski 《Journal of Theoretical Probability》1997,10(4):1053-1063
For independent identically distributed random vectors belonging to the generalized Domain of Attraction of the multivariate normal law, we define two partial sum processes analogous to that of Donsker's Theorem. We prove that each converges in distribution to a Brownian Motion in the space of continuous functions. One process uses nonrandom operator normalization, and the other is a studentization of the first, using normalization by the empirical covariance operator. 相似文献
6.
The main objects of study in this article are two classes of Rankin–Selberg L-functions, namely L(s,f×g) and L(s, sym2(g)× sym2(g)), where f,g are newforms, holomorphic or of Maass type, on the upper half plane, and sym2(g) denotes the symmetric square lift of g to GL(3). We prove that in general, i.e., when these L-functions are not divisible by L-functions of quadratic characters (such divisibility happening rarely), they do not admit any LandauSiegel zeros. Such zeros, which are real and close to s=1, are highly mysterious and are not expected to occur. There are corollaries of our result, one of them being a strong lower bound for special value at s=1, which is of interest both geometrically and analytically. One also gets this way a good bound onthe norm of sym2(g). 相似文献
7.
8.
Normalized Dynamic Characterization and Application of Multiple Heat Storage Materials Based on Standard Thermal Resistance北大核心CSCD 下载免费PDF全文
基于标准热阻和能量流法,推导出储热材料与换热流体的瞬态换热热阻,通过类比电路分析法,获得了储热-换热过程的瞬态热量流模型及动态响应时间常数。进一步引入节点温度,重新定义换热热阻,获得了储热与换热过程耦合的三阶电路瞬态热量流模型,求解得到了加热、储热和释热三类时间常数,可用于协同表征储热材料中储热与释热的快慢程度,从而实现了多类储热材料的归一化动态表征。通过数值模拟验证与应用对比分析,发现基于多时间常数的归一化动态模型用于表征储热材料的动态特性是可行的,可直接对不同换热、储热材料进行对比分析。案例分析发现与固体储热材料换热时,液态金属的动态换热能力优于熔融盐,而相比于水蒸气和CO2,空气与陶瓷材料换热能更快达到稳态。 相似文献
9.
Winfried Mientus Hans-Georg Bartel Werner Haberditzl Hans-Joachim Spitzer 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):597-606
A normalization of the wave functions by means of the theoretical exact Multiple-Scattering-(MS)-formalism is discussed within the framework of the SCF-X-SW-method. For the atomic and extramolecular regions the integrals of normalization can be easily determined and the results can be described by the corresponding electronic charges. The calculation of the integral of the interatomic region is problematic. The needful volume integration is only necessary to theGreen's functions of the wave functions and can be solved by means of the residual theory. The further analytical calculation of the surface integrals leads to a complicated formalism which can be numerically evaluated. 相似文献
10.
The combination of Fourier transform (FT)-Raman spectroscopy and partial least squares (PLS) regression is proposed to be used in off-line kerosene quality control. Here, six important physico-chemical properties have been studied: Abel flash point, initial boiling point (IBP), 10% of distilled sample, final boiling point (FBP), total percentage of aromatic compounds (% aromatics) and viscosity. The Raman spectra were obtained directly from standard 2 ml glass vials ( mm), using a Bruker RFS 100 FT-Raman spectrometer, equipped with a 1064 nm Nd:YAG laser and a Ge detector, in back-scattering mode and accumulating 25 scans (150 s acquisition time) with a laser power of 300 mW. All Raman spectra were unit normalized in order to avoid the influence of the laser power into the regression models. Different Raman shift spectral ranges have been evaluated, the 193.5-1688.1 cm−1 region being the most satisfactory one. Corrected standard errors of prediction of 1.9, 2.3, 2.8 °C, 0.19 cSt and 0.7% were obtained for flash point, IBP, FBP, viscosity and % aromatics, respectively. The influences of the glass vials, sample positioning and laser power have been studied, as well. 相似文献