全文获取类型
收费全文 | 6509篇 |
免费 | 698篇 |
国内免费 | 629篇 |
专业分类
化学 | 955篇 |
晶体学 | 91篇 |
力学 | 623篇 |
综合类 | 125篇 |
数学 | 4580篇 |
物理学 | 1462篇 |
出版年
2024年 | 8篇 |
2023年 | 63篇 |
2022年 | 90篇 |
2021年 | 111篇 |
2020年 | 173篇 |
2019年 | 204篇 |
2018年 | 182篇 |
2017年 | 216篇 |
2016年 | 244篇 |
2015年 | 191篇 |
2014年 | 335篇 |
2013年 | 566篇 |
2012年 | 309篇 |
2011年 | 398篇 |
2010年 | 341篇 |
2009年 | 372篇 |
2008年 | 413篇 |
2007年 | 410篇 |
2006年 | 349篇 |
2005年 | 323篇 |
2004年 | 275篇 |
2003年 | 254篇 |
2002年 | 297篇 |
2001年 | 250篇 |
2000年 | 245篇 |
1999年 | 214篇 |
1998年 | 179篇 |
1997年 | 168篇 |
1996年 | 114篇 |
1995年 | 75篇 |
1994年 | 62篇 |
1993年 | 45篇 |
1992年 | 34篇 |
1991年 | 43篇 |
1990年 | 22篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 29篇 |
1984年 | 28篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有7836条查询结果,搜索用时 0 毫秒
91.
《Arabian Journal of Chemistry》2022,15(7):103933
In this study, a fingerprint-activity relationship modeling between chemical fingerprints and antirheumatic activity was established, and multivariate statistical analysis was used to evaluate the quality of Taxilli Herba (TH) from different hosts. Characteristic fingerprints of 20 batches of TH samples were generated by high-performance liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (HPLC-Triple TOF-MS/MS), and the similarity analysis was calculated based on thirteen common characteristic peaks by hierarchical clustering analysis (HCA). Subsequently, nine efficacy markers were discovered by combining fingerprints and antirheumatic activity through grey correlation analysis (GCA) and bivariate correlation analysis (BCA). Meanwhile, the content of 5 constituents in 9 markers was determined by high-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (HPLC-QTRAP-MS/MS). The comprehensive quality of TH was assessed using multivariate statistical analysis, including principal components analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS). The results showed that a high dose of TH extract could markedly ameliorate arthritis damage compared to other doses, with flavonoids playing an important role in the antirheumatic activity. The comprehensive quality of samples from Morus alba L. (SS) was superior to those from Liquidambar formosana Hance (FXS). The present study will demonstrate the markers associated with efficacy, and provide an applicable strategy for more comprehensive quality control and evaluation of TH. 相似文献
92.
Paul Ruelle Michel Buchmann Hô Nam-Tran Ulrich W. Kesselring 《Journal of computer-aided molecular design》1992,6(5):431-448
Summary The thermodynamics of mobile order is applied to predict the aqueous solubility of liquid and solid aliphatic and polycyclic aromatic hydrocarbons. The solubility values are mainly determined by the magnitude of the hydrophobic effect. However, contrary to the solubilities of the alkanes, the solubilities of polycyclic aromatic hydrocarbons in water predicted in absence of solute-solvent hydrogen (H) bonds are systematically too low. This shows the contribution of weak specific interactions between the OH groups and the electrons of the aromatic substances. According to the theory, these interactions are characterized by a stability bility constant Ko which can be derived from solubility data. At 25°C, this constant amounts to 80 cm3/mol, the order of magnitude of which can be explained by the competition of these intermolecular bonds with the rather weak self-association bonds in the secondary chains of water. 相似文献
93.
Abdel-Wahab M. Nourein 《BIT Numerical Mathematics》1976,16(3):291-297
In this paper we describe a new technique for generating iteration formulas — of arbitrary order — for determining a zero (assumed simple) of a functionf, assumed analytic in a region containing the zero. The 1/p Padé Approximant (p0) to the functiong(t)f(z) is formed wherez=w+t, using the Taylor series forf at the pointw, an approxination to the zero off. The value oft for which the 1/p Padé Approximant vanishes provides the basis of iteration formulas of orderp+2.Some known iteration formulas, e.g., Newton-Raphson's, Halley's and Kiss's of order of convergence two, three and four, are directly obtained by settingp=0,1 and 2, respectively. 相似文献
94.
We study the characteristics of phase transition to take the top-priority of randomization in the rules of NaSch model (i.e.noise-first model) into account via computing the relaxation time and the order parameter.The scaling exponents of the relaxation time and the scaling relation of order parameter,respectively,axe obtained. 相似文献
95.
作为零位干涉检测方法中非常有前途的一种方法.计算全息可以用于非旋转对称的非球面的检测.以三次相位板为例,阐述了利用计算全息图检测非旋转对称的非球面的基本原理.分析并推导了三次相位传播过程引入的高阶波像差的理论公式,给出了三次相位板的检测系统的没计结果.详细讨论了计算全息图衍射级次的分离以及计算全息图的二元化,给出了振幅型的计算全息图的图样.计算全息图的刻线最小问隔是40μm,计算全息图的制作精度对检测结果的波前误差的影响仅仅为0.005λ.对检测系统作了详细的公差分析,结果表明所有调整公差对整个检测系统的影响和方根值为83.954 nm. 相似文献
96.
刘湘蓉 《高校应用数学学报(A辑)》2008,23(4)
对于线性模型y=Xθ ε,ε服从椭球等高单峰分布,未知参数θ满足不等式约束a′θ≥0,证明了在参数估计优良性的集中概率准则下,θ的约束最小二乘估计θ~*优于最小二乘估计θ. 相似文献
97.
在标准Rough集理论的指导下,利用偏序关系性质构造了不同分类,并以此为基础探讨了上、下近似集,从而构建了基于偏序关系的Rough集模型。新模型将Rough集理论的应用范围由等价关系扩展到偏序关系。为了更好地增强模型的实用性和灵括性,一方面从程度、精度、概率等角度出发分别对其进行了扩展,另一方面引入依赖度使其适用于研究各种非严格的偏序关系。给出了实例分析,并结合现实生活中的现象阐述了模型的应用价值。 相似文献
98.
99.
100.
对一类函数的无穷积分余项与该函数的比值得到当x趋于无穷大时的收敛阶,这类函数是幂函数与指数函数的乘积函数,并将其应用到Mittag-Leffler函数.同时考虑了对应的级数情形. 相似文献