全文获取类型
收费全文 | 39745篇 |
免费 | 5865篇 |
国内免费 | 5436篇 |
专业分类
化学 | 20691篇 |
晶体学 | 973篇 |
力学 | 3666篇 |
综合类 | 635篇 |
数学 | 9106篇 |
物理学 | 15975篇 |
出版年
2024年 | 51篇 |
2023年 | 445篇 |
2022年 | 798篇 |
2021年 | 911篇 |
2020年 | 1120篇 |
2019年 | 967篇 |
2018年 | 977篇 |
2017年 | 1295篇 |
2016年 | 1558篇 |
2015年 | 1284篇 |
2014年 | 1911篇 |
2013年 | 3212篇 |
2012年 | 2320篇 |
2011年 | 2683篇 |
2010年 | 2408篇 |
2009年 | 2801篇 |
2008年 | 2757篇 |
2007年 | 2908篇 |
2006年 | 2665篇 |
2005年 | 2159篇 |
2004年 | 1974篇 |
2003年 | 1757篇 |
2002年 | 1496篇 |
2001年 | 1359篇 |
2000年 | 1247篇 |
1999年 | 1090篇 |
1998年 | 1005篇 |
1997年 | 851篇 |
1996年 | 774篇 |
1995年 | 645篇 |
1994年 | 592篇 |
1993年 | 456篇 |
1992年 | 456篇 |
1991年 | 310篇 |
1990年 | 236篇 |
1989年 | 227篇 |
1988年 | 179篇 |
1987年 | 156篇 |
1986年 | 115篇 |
1985年 | 125篇 |
1984年 | 123篇 |
1983年 | 58篇 |
1982年 | 129篇 |
1981年 | 85篇 |
1980年 | 71篇 |
1979年 | 95篇 |
1978年 | 50篇 |
1977年 | 40篇 |
1976年 | 25篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Bajdik J. Pintye-Hódi K. Novák Cs. Kelemen A. Regdon G. Erős I. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):613-627
The extents of the protective effects of coating films on the surface of crystals were determined. Three different samples
were made with different quantities of coating fluid (Sepifilm LP 010 in 10% aqueous solution). Since the atomizing rate was
constant, the coating time increased in parallel with the volume of coating fluid applied. The direct measurement of film
thickness and smoothness is very difficult, and therefore indirect methods were used. Dimenhydrinate was chosen as model drug;
this is a heat-sensitive antihistamine with a low melting point. This temperature can be reached during the tableting process.
The behaviour of samples on exposure to heat was examined by differential scanning calorimetry. The water uptakes of the samples
were determined with an Enslin apparatus. Plasticity was studied with an instrumented tablet machine. These indirect methods
(thermal conductivity, water uptake and plasticity measurements) revealed connections between the results of the various experiments.
An overlong coating time decreased the protective effect of the coating film.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
72.
The paper proposes a rational method to derive fairness measures for surfaces. It works in cases where isophotes, reflection lines, planar intersection curves, or other curves are used to judge the fairness of the surface. The surface fairness measure is derived by demanding that all the given curves should be fair with respect to an appropriate curve fairness measure. The method is applied to the field of ship hull design where the curves are plane intersections. The method is extended to the case where one considers, not the fairness of one curve, but the fairness of a one parameter family of curves. Six basic third order invariants by which the fairing measures can be expressed are defined. Furthermore, the geometry of a plane intersection curve is studied, and the variation of the total, the normal, and the geodesic curvature and the geodesic torsion is determined. 相似文献
73.
为了准确计算出镀膜过程中每层膜的折射率,介绍了实时监控过程中确定膜层折射率的2种方法:一种是由实测的透射比光谱直接反算出膜层的折射率;另一种是用最小二乘法的优化算法实时拟合折射率。试验结果表明:在线反算适合单点监控,所得折射率误差小于2%。然而在实际镀膜过程中,由于宽带内膜层参数误差较大,一般大于25%。为此,采用最小二乘法拟合,即在整个宽光谱范围内采集每个波长点的信息,所得结果误差很小,一般都在2%~5%之间,有时可达到10%,在很大程度上提高了实际镀膜时膜厚监控的精度。 相似文献
74.
75.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
76.
77.
78.
烷基硫酸盐表面张力的量子化学研究 总被引:1,自引:0,他引:1
用AMl量子化学计算法优化了十三烷基硫酸根阴离子和——CH3在不同取代位的十二烷基硫酸根阴离子的几何构型,得到最优构型时最高占据分子轨道能级EHOMO、最低空轨道能级ELUMO、电子能量Eele和偶极矩μ等数据.将这些电子结构数据分别与表面张力相拟合,得到很好的相关性。文中讨论了——CH3在不同位置取代对表面张力的影响。 相似文献
79.
80.