全文获取类型
收费全文 | 248篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 176篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 30篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
61.
M.?Jamil?AmirEmail author Sadia?Sattar 《International Journal of Theoretical Physics》2016,55(4):1988-2000
This paper contains the study of spherically symmetric perfect fluid collapse in the frame work of f(R, T) modified theory of gravity. We proceed our work by considering the non-static spherically symmetric background in the interior and static spherically symmetric background in the exterior regions of the star. The junction conditions between exterior and interior regions are presented by matching the exterior and interior regions. The field equations are solved by taking the assumptions that the Ricci scalar as well as the trace of energy-momentum tensor are to be constant, for a particular f(R, T) model. By inserting the solution of the field equations in junction conditions, we evaluate the gravitational mass of the collapsing system. Also, we discuss the apparent horizons and their time formation for different possible cases. It is concluded that the term f(R 0, T 0) behaves as a source of repulsive force and that’s why it slowdowns the collapse of the matter. 相似文献
62.
Shakeel Sadia Gul Somia Zahoor Aqib Khan Saleha Suleman Sheikh Zeeshan Ahmed Naveed Safila Usmanghani Khan 《平面色谱法杂志一现代薄层色谱法》2015,28(5):386-390
JPC – Journal of Planar Chromatography – Modern TLC - The technological improvement in the structural elucidation of natural compounds has made it probable to generate appropriate... 相似文献
63.
Interior-point methods for semidefinite optimization have been studied intensively, due to their polynomial complexity and
practical efficiency. Recently, the second author designed a primal-dual infeasible interior-point algorithm with the currently
best iteration bound for linear optimization problems. Since the algorithm uses only full Newton steps, it has the advantage
that no line-searches are needed. In this paper we extend the algorithm to semidefinite optimization. The algorithm constructs
strictly feasible iterates for a sequence of perturbations of the given problem and its dual problem, close to their central
paths. Two types of full-Newton steps are used, feasibility steps and (ordinary) centering steps, respectively. The algorithm
starts from strictly feasible iterates of a perturbed pair, on its central path, and feasibility steps find strictly feasible
iterates for the next perturbed pair. By using centering steps for the new perturbed pair, we obtain strictly feasible iterates
close enough to the central path of the new perturbed pair. The starting point depends on a positive number ζ. The algorithm terminates either by finding an ε-solution or by detecting that the primal-dual problem pair has no optimal solution (X
*,y
*,S
*) with vanishing duality gap such that the eigenvalues of X
* and S
* do not exceed ζ. The iteration bound coincides with the currently best iteration bound for semidefinite optimization problems. 相似文献
64.
Sajjad Ahmad Momin Khan Najeeb Ur Rehman Muhammad Ikram Sadia Rehman Mahboob Ali Jalal Uddin Ajmal Khan Aftab Alam Ahmed Al-Harrasi 《Molecules (Basel, Switzerland)》2022,27(20)
Background: Hydrazides play a vital role in making biologically active compounds in various fields of chemistry. These determine antioxidant, antidepressant, antimalarial, anti-inflammatory, antiglycating, and antimicrobial activity. In the present study, twenty-three new N′ benzylidene-4-(tert-butyl)benzohydrazide derivatives (4–26) were synthesized by the condensation of aromatic aldehydes and commercially available 4-(tert-butyl)benzoic acid. All the target compounds were successfully synthesized from good to excellent yield; all synthesized derivatives were characterized via spectroscopic techniques such as HREI-MS and 1H-NMR. Synthesized compounds were evaluated for in vitro urease inhibition. All synthesized derivatives demonstrated good inhibitory activities in the range of IC50 = 13.33 ± 0.58–251.74 ± 6.82 µM as compared with standard thiourea having IC50 = 21.14 ± 0.425 µM. Two compounds, 6 and 25, were found to be more active than standard. SAR revealed that electron donating groups in phenyl ring have more influence on enzyme inhibition. However, to gain insight into the participation of different substituents in synthesized derivatives on the binding interactions with urease enzyme, in silico (computer simulation) molecular modeling analysis was carried out. 相似文献
65.
Developing imprinted polymer nanoparticles for the selective separation of antidiabetic drugs 下载免费PDF全文
Isma Haq Adnan Mujahid Adeel Afzal Naseer Iqbal Sadia Zafar Bajwa Tajamal Hussain Khurram Shehzad Hadia Ashraf 《Journal of separation science》2015,38(19):3469-3476
In this study, new molecularly imprinted polymer (MIP) nanoparticles are designed for selective recognition of different drugs used for the treatment of type 2 diabetes mellitus, i.e. sitagliptin (SG) and metformin (MF). The SG‐ and MF‐imprinted polymer nanoparticles are synthesized by free‐radical initiated polymerization of the functional monomers: methacrylic acid and methyl methacrylate; and the crosslinker: ethylene glycol dimethacrylate. The surface morphology of resultant MIP nanoparticles is studied by atomic force microscopy. Fourier transform infrared spectra of MIP nanoparticles suggest the presence of reversible, non‐covalent interactions between the template and the polymer. The effect of pH on the rebinding of antidiabetic drugs with SG‐ and MF‐imprinted polymers is investigated to determine the optimal experimental conditions. The molecular recognition characteristics of SG‐ and MF‐imprinted polymers for the respective drug targets are determined at low concentrations of SG (50–150 ppm) and MF (5–100 ppm). In both cases, the MIP nanoparticles exhibit higher binding response compared to non‐imprinted polymers. Furthermore, the MIPs demonstrate high selectivity with four fold higher responses toward imprinted drugs targets, respectively. Recycled MIP nanoparticles retain 90% of their drug‐binding efficiency, which makes them suitable for successive analyses with significantly preserved recognition features. 相似文献
66.
Kahled Bahlali M. Hassani B. Mansouri N. Mrhardy 《Comptes Rendus Mathematique》2009,347(19-20):1201-1206
We prove the existence and uniqueness of solutions to Reflected Backward Doubly Stochastic Differential Equations (RBDSDEs) with one continuous barrier and uniformly Lipschitz coefficients. The existence of a maximal and a minimal solution for RBDSDEs with continuous generator is also established. To cite this article: K. Bahlali et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009). 相似文献
67.
Ferheen S Ahmed E Malik A Afza N Lodhi MA Choudhary MI 《Chemical & pharmaceutical bulletin》2006,54(8):1088-1090
Hyperinols A (1) and B (2) are new taraxastane type triterpenes which have been isolated from the chloroform soluble fraction of Hypericum oblongifolium and their structures elucidated on the basis of spectroscopic data. Both showed significant inhibitory activity against chymotrypsin enzyme. 相似文献
68.
Gerasimova YV Peck S Kolpashchikov DM 《Chemical communications (Cambridge, England)》2010,46(46):8761-8763
The new enzyme-assisted assay for DNA/RNA detection provides real-time fluorescent signal readout along with low limit of detection and high discrimination power toward a single-base substitution. Requiring only two new unmodified DNA oligonucleotides for the detection of each new analyte, the assay is an efficient tool for low-cost analysis of multiple analytes. 相似文献
69.
Alvarado F Bari S Hoekstra R Schlathölter T 《Physical chemistry chemical physics : PCCP》2006,8(16):1922-1928
Recent experiments on low energy ion-induced damage to DNA building blocks indicate that ion induced DNA damage is dominated by deoxyribose disintegration (Phys. Rev. Lett., 2005, 95, 153201). We have studied interactions of keV H+ and He(q+) with isolated deoxyribose molecules by means of high resolution time-of-flight spectrometry. Extensive statistical fragmentation of the molecules is observed. The fragment distribution is found to follow a power law dependence. The exponent can be used to characterize and quantify the molecular damage. 相似文献
70.
Ionic Conductivity of the Phases Isolated in the Binary Systems PbF2? SnF4 and PbF2? GeF4 The study of PbF2? MF4 (M ?; Sn, Ge) systems reveals a restricted solid solution domain, with a fluorine structure and edfinite Pb3GeF10, Pb3Ge2F14 and PbMF6 phases. The ionic conductivity has been measured by complex impedance technic. It appears that, in the solid solutions the M4+ cations adopt a distorted octahedral environment. 相似文献