全文获取类型
收费全文 | 3151篇 |
免费 | 374篇 |
国内免费 | 182篇 |
专业分类
化学 | 995篇 |
晶体学 | 6篇 |
力学 | 310篇 |
综合类 | 33篇 |
数学 | 1166篇 |
物理学 | 1197篇 |
出版年
2024年 | 8篇 |
2023年 | 39篇 |
2022年 | 85篇 |
2021年 | 99篇 |
2020年 | 88篇 |
2019年 | 88篇 |
2018年 | 78篇 |
2017年 | 96篇 |
2016年 | 102篇 |
2015年 | 87篇 |
2014年 | 175篇 |
2013年 | 191篇 |
2012年 | 195篇 |
2011年 | 195篇 |
2010年 | 161篇 |
2009年 | 162篇 |
2008年 | 169篇 |
2007年 | 174篇 |
2006年 | 171篇 |
2005年 | 185篇 |
2004年 | 140篇 |
2003年 | 152篇 |
2002年 | 142篇 |
2001年 | 99篇 |
2000年 | 109篇 |
1999年 | 88篇 |
1998年 | 71篇 |
1997年 | 63篇 |
1996年 | 45篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 26篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 10篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有3707条查询结果,搜索用时 46 毫秒
21.
在测量微安表内阻的众多方法中,替代法是最简单的方法。本文全面分析了影响测量结果不确定度的因素,求出了实验测量的最佳条件,计算了普通仪器组合下测量结果的相对不确定度。 相似文献
22.
On the Evaluation of Uncertain Courses of Action 总被引:3,自引:0,他引:3
Ronald R. Yager 《Fuzzy Optimization and Decision Making》2002,1(1):13-41
We consider the problem of decision making under uncertainty. The fuzzy measure is introduced as a general way of representing available information about the uncertainty. It is noted that generally in uncertain environments the problem of comparing alternative courses of action is difficult because of the multiplicity of possible outcomes for any action. One approach is to convert this multiplicity of possible of outcomes associated with an alternative into a single value using a valuation function. We describe various ways of providing a valuation function when the uncertainty is represented using a fuzzy measure. We then specialize these valuation functions to the cases of probabilistic and possibilistic uncertainty. 相似文献
23.
X光底片在位相对标定 总被引:3,自引:0,他引:3
本文描述了X光底片在位相对标定技术。其原理是使X射线谱经阶梯形吸收滤片透射后,对X光底片曝光,测量底片的曝光量。文中给出了标定方法和数据处理方法,而且也给出了在X光激光实验中得到的Kodak AA5底片的特性曲线。 相似文献
24.
厄米-双曲余弦-高斯光束的瞄准稳定性 总被引:1,自引:0,他引:1
用失调叠加积分的方法 ,对厄米双曲余弦高斯光束的瞄准稳定性作了研究 ,得到了厄米双曲余弦高斯光束失调因子 ηm2 的精确解析公式和近似解析公式 ,并用数值计算了相对横向偏移和相对角向偏移对失调因子ηm2 的影响以及对精确解析公式和近似解析公式的适用范围作了分析和说明。 相似文献
25.
教学研究:介绍量子力学几个基本概念——兼答《关于量子几何相位的评注》中的几个主要问题 总被引:4,自引:4,他引:0
介绍了量子绝热定理的物理含义及成立的条件,认为有关主要献(Aharonov-Anandan,Bohm,孙昌璞等)的表述是正确的,而《关于量子几何相位的评注》^[1](以下简称《评注》)相应的表述不完全正确。在此基础上,认为这些献和教材(R.Shankar)得出的涉及Berry绝热相位的一些论述(不含Berry绝热相因子的瞬时能量本征态不满足含时Schroedinger方程等)也是正确的,而《评注》的论述与此相反。《评注》认为只有γn(C)才是Berry相位。本作则倾向于把γn(t)叫做Berry绝热相位,而把γn(C)=γn(T)-γn(0)叫做几何相位(geometric phase)^[2]。 相似文献
26.
In this paper, we give a construction of RDS in Galois ring by using some bent function, and obtain the equivalent relationship between RDS and a kind of bent function. At the same time, its existence is demonstrated. 相似文献
27.
28.
T. Drglin 《Accreditation and quality assurance》2003,8(3-4):130-133
A validation procedure based on the ISO/IEC 17025 standard was used to demonstrate the long-term stability of a calibration
process and to assess the measurement uncertainty of a standard test method for optical emission vacuum spectrometric analysis
of carbon and low-alloy steel (ASTM E 415–99a). The validation was used to provide documented evidence that the selected method
fulfils the requirements and that the method is ”fit for purpose”. A test for drift was applied to determine statistically
whether the analytical results vary systematically with time. The accuracy and traceability of the optimised method were tested
by an analysis of closely matched matrix certified reference materials (CRMs). The measurement uncertainty estimations took
account of the precision study, the bias and its uncertainty, and the qualification of uncertainties not considered in the
overall performance studies.
Received: 2 November 2002 Accepted: 2 January 2003
Acknowledgement The author expresses gratitude to Dr. Aleš Fajgelj for helpful discussions during the 3rd Central European Conference on Reference Materials and Measurements.
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials
in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to T. Drglin 相似文献
29.
An analytical result is not considered to be complete without a statement of the measurement uncertainty associated with
it. Evaluation of measurement uncertainty is therefore an essential part of every determination. In the present study the
measurement uncertainty of the result of determination of selenium in the reference material Seronorm Trace Elements Serum
was studied. The combination of a digestion procedure using sulfuric acid, V2O5 in H2SO4 and hydrogen peroxide and the continuous flow approach of hydride generation atomic fluorescence spectrometry (HG-AFS) detection
was used for selenium determination. The total uncertainty budget was calculated with the help of the GUM Workbench program,
in which computations follow the rules of the ’ISO guide to the expression of uncertainty in measurement’. The major sources
of uncertainty were found to be due to the recovery of the procedure, measurement of peak heights and the purity of Na2SeO3. A selenium mass fraction of 77.1±4.8 ng/g (with a coverage factor of 2.1, 95% probability) was determined, which is comparable
with the recommended value of 80 ng/g.
Received: 13 September 2002 Accepted: 23 December 2002
Acknowledgements We would like to thank Tinkara Buˇcar, B.Sc. for useful discussions and the IAEA Vienna, for financial support of the project
11553/RO.
Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials
in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia
Correspondence to V. Stibilj 相似文献
30.
近些年来,许多处理近似问题的方法陆续被提出,其中利用Rough集理论计算两个集合的并和交的Rough隶属函数方法是被用较多的一种方法,但毕竟该方法精度较差。为此,介绍了一种精度较高的计算两个集合的并和交的Rough隶属函数方法,它克服了前者利用Rough集理论计算Rough隶属函数的复杂性,而迎来了简单和高精度的特点。 相似文献