全文获取类型
收费全文 | 838篇 |
免费 | 21篇 |
国内免费 | 2篇 |
专业分类
化学 | 433篇 |
晶体学 | 9篇 |
力学 | 28篇 |
数学 | 183篇 |
物理学 | 208篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 26篇 |
2017年 | 21篇 |
2016年 | 25篇 |
2015年 | 28篇 |
2014年 | 23篇 |
2013年 | 58篇 |
2012年 | 51篇 |
2011年 | 50篇 |
2010年 | 37篇 |
2009年 | 43篇 |
2008年 | 47篇 |
2007年 | 26篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 26篇 |
2003年 | 13篇 |
2002年 | 5篇 |
2001年 | 14篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有861条查询结果,搜索用时 31 毫秒
101.
In the present communication an analysis of interionic potentials in fourteen chalcogenide crystals has been performed. This interionic potential has been used to predict the values of cohesive energy, isothermal bulk modulus and the pressure derivatives of bulk modulus in the solids under study. The many body interaction (MBI) effects have been taken into account within the framework of Hafemeister Zarht potential. Instead of using BM potential the Hafemeister-Zarht (HZ) type short range overlap potential has been considered between nearest as well as between next nearest neighbour ions. The short-range interactions, effective up to second neighbours are treated by considering the hardness parameter as an ionic property. The hardness parameter ρij is evaluated using the data on overlap integrals. The results achieved in the present study are generally in good agreement with available experimental data. Values of cohesive energy, bulk modulus and its pressure derivatives calculated by previous investigators have also been shown for the sake of comparison. 相似文献
102.
Somenath Sarkar Arun Kumar I.C. Goyal Enakshi K. Sharma Ramanand Tewari 《Optics Communications》1985,53(2):91-94
We present an analytical method to evaluate the auxiliary function and spot sizes determining microbending loss in single mode fibers with arbitrary refractive index profiles. Comparison with the exact numerical results shows that the present method gives very accurate results for spot sizes. The method is simple and requires relatively less computational effort. 相似文献
103.
104.
Karr AF Feng J Lin X Sanil AP Young SS Reiter JP 《Journal of computer-aided molecular design》2005,19(9-10):739-747
We present a method for performing statistically valid linear regressions on the union of distributed chemical databases that preserves confidentiality of those databases. The method employs secure multi-party computation to share local sufficient statistics necessary to compute least squares estimators of regression coefficients, error variances and other quantities of interest. We illustrate our method with an example containing four companies' rather different databases. 相似文献
105.
106.
107.
Three-dimensional quantitative structure–activity relationship (3D-QSAR) models were developed based on comparative molecular
field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), on a series of 43 hydroxyethylamine
derivatives, acting as potent inhibitors of β-site amyloid precursor protein (APP) cleavage enzyme (BACE-1). The crystal structure of the BACE-1 enzyme (PDB ID: 2HM1)
with one of the most active compound 28 was available, and we assumed it to be the bioactive conformation of the studied series, for 3D-QSAR analysis. Statistically
significant 3D-QSAR model was established on a training set of 34 compounds, which were validated by a test set of 9 compounds.
For the best CoMFA model, the statistics are, r
2 = 0.998, r2cv = 0.810{r^{2}_{\rm cv} = 0.810} , n = 34 for the training set and r2pred = 0.934{r^{2}_{\rm pred} = 0.934} , n = 9 for the test set. For the best CoMSIA model (combined steric, electrostatic, hydrophobic, and hydrogen bond donor fields),
the statistics are r
2 = 0.978, r2cv = 0.754{r^{2}_{\rm cv} = 0.754} , n = 34 for the training set and r2pred = 0.750{r^{2}_{\rm pred} = 0.750} , n = 9 for the test set. The resulting contour maps, produced by the best CoMFA and CoMSIA models, were used to identify the
structural features relevant to the biological activity in this series of analogs. The data generated from the present study
will further help to design novel, potent, and selective BACE-1 inhibitors. 相似文献
108.
Pallav Goyal 《代数通讯》2018,46(10):4511-4529
109.
Fuzzy optimization models are used to derive crisp weights (priority vectors) for the fuzzy analytic hierarchy process (AHP) based multicriteria decision making systems. These optimization models deal with the imprecise judgements of decision makers by formulating the optimization problem as the system of constrained non linear equations. Firstly, a Genetic Algorithm based heuristic solution for this optimization problem is implemented in this paper. It has been found that the crisp weights derived from this solution for fuzzy-AHP system, sometimes lead to less consistent or inconsistent solutions. To deal with this problem, we have proposed a consistency based constraint for the optimization models. A decision maker can set the consistency threshold value and if the solution exists for that threshold value then crisp weights can be derived, otherwise it can be concluded that the fuzzy comparison matrix for AHP is not consistent for the given threshold. Three examples are considered to demonstrate the effectiveness of the proposed method. Results with the proposed constraint based fuzzy optimization model are more consistent than the existing optimization models. 相似文献
110.