全文获取类型
收费全文 | 1013篇 |
免费 | 73篇 |
国内免费 | 52篇 |
专业分类
化学 | 349篇 |
晶体学 | 5篇 |
力学 | 59篇 |
综合类 | 4篇 |
数学 | 142篇 |
物理学 | 579篇 |
出版年
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 12篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 37篇 |
2016年 | 34篇 |
2015年 | 41篇 |
2014年 | 75篇 |
2013年 | 70篇 |
2012年 | 36篇 |
2011年 | 73篇 |
2010年 | 48篇 |
2009年 | 70篇 |
2008年 | 65篇 |
2007年 | 62篇 |
2006年 | 70篇 |
2005年 | 48篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有1138条查询结果,搜索用时 15 毫秒
321.
322.
Viktor G. Berezkin Irina V. Malyukova Victor R. Alishoev Jaap de Zeeuw 《Journal of separation science》1996,19(5):272-276
In capillary gas-solid chromatography where interactions between solute and carrier gas and adsorption of the solute on the surface of the adsorbent are considered to be imperfect, it has been shown that chromatographic retention is determined largely by adsorption processes. It has been established that correlation relationships k(P2)=A k(P1) + B, where k is the retention factor, and A and B are equation constants, was valid for use of different carrier gases P1 and P2. Column efficiency could be improved by use of carbon dioxide. The advantages of using carbon dioxide as the carrier gas were investigated. 相似文献
323.
324.
The quantum non-relativistic two-component Bose and Fermi gases with infinitely strong point-like coupling between particles in one space dimension are considered. Time- and temperature-dependent correlation functions are represented in the thermodynamic limit as Fredholm determinants of integrable linear integral operators. 相似文献
325.
本文在各种溶剂粘度下对18-冠醚-6的两种稳定构象Ci和D3d进行了Langevin模分析。结果表明,溶剂的粘度对18-冠醚-6的性质,特别是对振动频率分布和键偶极矢量的摇摆角度有较大的影响。同时表明,Langevin模方法是解释溶液中分子运动情况的一种简捷有力的模型。 相似文献
326.
Hai Ying HE Chen Lin Cheng Xue ZHAO* Xi Kui JIANG* Department of Chemistry Shanghai Jiaotong University Shanghai Shanghai Institute of Organic Chemistry Shanghai 《中国化学快报》2001,(12)
It has been suggested about forty years ago that the transition states of polarographic potential-determining steps possess free radical character1. However, the dual-parameter correlation analysis [eqn. (1)] have never been successfully applied to the redox potentials until our recent report on five series of aromatic compounds shows that polarographic processes are affected by the polar effect as well as the spin-delocalization effect2. The purpose of this paper is to study the correlation… 相似文献
327.
328.
用于检测油膜厚度的光纤传感器系统 总被引:1,自引:0,他引:1
非接触式光纤传感器因其抗干扰性强、灵敏度高、电绝缘性好等特点在某些场合占有不可替代的位置.本文介绍了一种用于检测大型涡轮机液压轴承运动状态及其周围油膜厚度分布情况的光纤传感器系统.详细讨论了传感器的结构及数据模型,并着重介绍了系统的几个重要组成部分,其中包括双光路、调制解调和并行数据采集等,最后给出了传感器的特性测试数据. 相似文献
329.
Large cooling towers are sensitive to wind effects with their increasing heights and flexibilities. Unlike traditional approaches, which employed Code-defined normal winds to check the loading characteristics, this paper developed a framework for checking the typhoon-induced wind loading on a large cooling tower using Monte Carlo simulations and multi-fan wind tunnel tests. Some distinct characteristics of typhoon winds were compared with those of Code-defined normal winds. Furthermore, wind characteristics of incoming normal and typhoon winds in terms of vertical profile of mean wind speed, turbulence intensity, turbulence integral length scale and power spectrum density of fluctuating winds were well reproduced by a feedback control process of a multi-fan actively controlled wind tunnel. The surface wind pressure distributions of a large cooling tower under these conditions were then investigated by testing a 1:600 reduced scale model. Mean and fluctuating external wind pressures along the circumferential direction under various incoming winds were discussed and quantitatively formulated with eight-term trigonometric equations. Moreover, the cross correlations of wind pressures in the circumferential and meridian directions and correlations with structure base forces, i.e. integral drag and lift forces, were investigated. Non-Gaussian characteristics in terms of skewness and kurtosis of fluctuating wind pressures were also analyzed under two wind climates. Peak factors for modeling extreme wind pressures were examined and compared with those of various models. Finally, the extreme wind loads on a large cooling tower obtained from different wind pressure combinations were compared with peak-factor-theory-based results to identify an appropriate combination for structural design. 相似文献
330.
烃源岩的可溶烃含量(S1)、热解烃含量(S2)和总有机碳含量(TOC)是进行烃源岩研究和评价的重要指标,以往主要通过实验室分析方法获得,时效性得不到保证。为了探讨野外快速测量这些指标的可行性,采集了乌兹别克斯坦克孜勒库姆地块10件烃源岩样品,运用地面ASD光谱仪和碳硫分析仪,分别测定了样品的可见光-近红外-短波红外(Vis-NIR-SWIR)反射光谱和S1, S2和TOC含量参数。运用光谱拟合微分,获得了上述样品反射光谱的一阶导数、二价导数等微分数据;并运用线性回归方程拟合和拟合结果统计分析,研究了这些数据同S1, S2和TOC含量之间的相关性。结果表明:烃源岩S1含量与原始光谱、光谱一阶导数、二阶导数分别有1 973, 511和239个波段相关,相关系数绝对值最大值分别为0.612, 0.823和0.889,相关性程度分别为弱、较强、极强;烃源岩S2含量与原始光谱、光谱一阶导数、二阶导数分别有2, 144和205个波段相关,相关系数绝对值最大值分别为0.561, 0.867和0.926,相关性程度分别为弱、较强、极强;烃源岩TOC含量与原始光谱无相关性,与光谱一阶导数、二阶导数分别有18、 180个波段相关,相关系数绝对值最大值分别为0.882和0.879,相关性都极强。此外, S1含量与光谱二阶导数的2 012 nm波段拟合优度最高,达0.790;S2含量与光谱二阶导数的363 nm波段拟合优度最高,达0.858;TOC含量与光谱一阶导数的2 480 nm波段拟合优度最高,达0.777。结果说明,利用可见光-近红外-短波红外反射光谱反演烃源岩S1, S2和TOC含量具有比较好的效果。为研究野外烃源岩的原位检测奠定了重要的基础。 相似文献