全文获取类型
收费全文 | 348篇 |
免费 | 18篇 |
专业分类
化学 | 244篇 |
晶体学 | 5篇 |
力学 | 15篇 |
数学 | 20篇 |
物理学 | 82篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 23篇 |
2018年 | 17篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 34篇 |
2011年 | 25篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有366条查询结果,搜索用时 890 毫秒
41.
The problem of temperature distribution and heat transfer for laminar flow through two parallel porous disks of different
permeability, has been investigated when the flow is entirely due to injection and/or suction at the two disks. Viscous dissipation
terms have been included in the energy equation and the injection and/or suction velocities at the two disks are assumed to
be small. The boundaries are kept at constant temperatures. The variation of temperature and Nusselt numbers at the two disks
has been graphically depicted for various values of the injection and suction velocities. 相似文献
42.
Shukla R Bansal V Chaudhary M Basu A Bhonde RR Sastry M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10644-10654
Macrophages are one of the principal immune effector cells that play essential roles as secretory, phagocytic, and antigen-presenting cells in the immune system. In this study, we address the issue of cytotoxicity and immunogenic effects of gold nanoparticles on RAW264.7 macrophage cells. The cytotoxicity of gold nanoparticles has been correlated with a detailed study of their endocytotic uptake using various microscopy tools such as atomic force microscopy (AFM), confocal-laser-scanning microscopy (CFLSM), and transmission electron microscopy (TEM). Our findings suggest that Au(0) nanoparticles are not cytotoxic, reduce the production of reactive oxygen and nitrite species, and do not elicit secretion of proinflammatory cytokines TNF-alpha and IL1-beta, making them suitable candidates for nanomedicine. AFM measurements suggest that gold nanoparticles are internalized inside the cell via a mechanism involving pinocytosis, while CFLSM and TEM studies indicate their internalization in lysosomal bodies arranged in perinuclear fashion. Our studies thus underline the noncytotoxic, nonimmunogenic, and biocompatible properties of gold nanoparticles with the potential for application in nanoimmunology, nanomedicine, and nanobiotechnology. 相似文献
43.
The weighted geometric mean of resistors considered for determining the effective thermal conductivityK E of two-phase systems has been optimised. Solutions of the equations lead to a useful set of bounds. When compared with other bounds the present bounds give the better results in estimating the upper and lower values of the effective thermal conductivity of a two-phase system. 相似文献
44.
S. Ahmad M. S. Chaudhary I. H. Qureshi 《Journal of Radioanalytical and Nuclear Chemistry》1980,57(1):185-193
An instrumental neutron activation analysis technique has been developed for simultaneous determination of 10 REE in low grade U/Zr ores and other geological materials. The samples were irradiated with reactor neutrons for 2 min to 8 hrs followed by a cooling of 30 min to 3 weeks. The γ-ray activity was measured with a semi-planar Ge(Li) detector. A precision of 5% has been obtained by the repeated analysis of NBS-SRM. The technique is relatively simple and adaptable on the routine basis. 相似文献
45.
Shridhar R. Gadre Savita S. Pundlik Indira H. Shrivastava 《Journal of Chemical Sciences》1994,106(2):303-314
The conventional electrostatic charge models (PD-AC) are constructed so as to reproduce the molecular electrostatic potential
(MESP) on and beyond the van der Waals’ (vdW) surface. The MESP distribution has recently [S R Gadre, S A Kulkarni and I H
Shrivastava (1992)J. Chem. Phys.
96 5253] been shown to exhibit rich topographical features. With this in view, a detailed topographical comparison of the MESP
derived from the charge models, with the respectiveab initio (MO) ones is taken up for water, hydrogen sulphide, methane and benzene molecules as test cases. It is shown that the point
charge models have a fundamental lacuna, viz. they fail to mimic the essential topographical features of MESP. A new model
incorporating a small number of floating spherical Gaussians is shown to restore all the critical features of the molecules
under study. A comparative study of the standard deviations of MESP derived from charge models on scaled vdW surfaces further
reveals that the present model leads to a better representation ofab initio MESP. 相似文献
46.
The paper describes the availability of crank-case manufacturing system in an automobile industry. The units discussed here fail either directly from normal working state or indirectly through partial failure state. The machines are subjected to both preventive and corrective maintenance. Failure and repair times of the units are independent. The problem is formulated using probability consideration and supplementary variable technique. The system of equations governing the working of system consists of ordinary as well as partial differential equations. Lagrange method and Runge–Kutta method is used to solve partial differential equation and ordinary differential equation respectively. The study reveals that successful program of preventive and routine maintenance will reduce equipment failures, extend the life of the equipment, and increase the system availability to considerable margin. 相似文献
47.
Reshma Khemchandani Nishil Gupta Arpit Chaudhary Suresh Chandra 《Optimization Letters》2013,7(3):575-592
In this paper, we develop optimal trading strategies for a risk averse investor by minimizing the expected cost and the risk of execution. Here we consider a law of motion for price which uses a convex combination of temporary and permanent market impact. In the special case of unconstrained problem for a risk neutral investor, we obtain a closed form solution for optimal trading strategies by using dynamic programming. For a general problem, we use a quadratic programming approach to get approximate dynamic optimal trading strategies. Further, numerical examples of optimal execution strategies are provided for illustration purposes. 相似文献
48.
Sudhakar Chaudhary V.V.K. Srinivas Kumar 《Numerical Methods for Partial Differential Equations》2013,29(4):1322-1340
In this article, we give some numerical techniques and error estimates using web‐spline based mesh‐free finite element method for the heat equation and the time‐dependent Navier–Stokes equations on bounded domains. The web‐spline method uses weighted extended B‐splines on a regular grid as basis functions and does not require any grid generation. We demonstrate the method by providing numerical results for the Poisson's and stationary Stokes equation. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2013 相似文献
49.
Sudhakar Chaudhary V. V. K. Srinivas Kumar 《Numerical Functional Analysis & Optimization》2013,34(3):264-283
The objective of this article is to discuss the existence and the uniqueness of a weighted extended B-spline-(WEB-spline) based discrete solution for the Maxwell equations in low frequency limit. The domain is composed of insulating and conducting regions. This problem has saddle point structure where the electric field in insulating region is the Lagrange multiplier that forces curl-free constraint on the magnetic field. 相似文献
50.
Asymmetric transfer hydrogenation of ketones using Ru(II)arene/amino alcohol catalyst system proceeds with significant rate enhancement by ultrasound promotion. Comparison of the silent reactions carried out at 25 degrees C with reactions under sonochemical activation at 25 degrees C clearly showed enhancement in catalytic activity by 5-10 times without significantly affecting the enantioselectivity. 相似文献