全文获取类型
收费全文 | 6510篇 |
免费 | 1185篇 |
国内免费 | 883篇 |
专业分类
化学 | 3810篇 |
晶体学 | 91篇 |
力学 | 120篇 |
综合类 | 40篇 |
数学 | 70篇 |
物理学 | 4447篇 |
出版年
2024年 | 17篇 |
2023年 | 67篇 |
2022年 | 191篇 |
2021年 | 194篇 |
2020年 | 241篇 |
2019年 | 210篇 |
2018年 | 201篇 |
2017年 | 282篇 |
2016年 | 318篇 |
2015年 | 302篇 |
2014年 | 437篇 |
2013年 | 525篇 |
2012年 | 458篇 |
2011年 | 416篇 |
2010年 | 355篇 |
2009年 | 378篇 |
2008年 | 478篇 |
2007年 | 460篇 |
2006年 | 398篇 |
2005年 | 324篇 |
2004年 | 331篇 |
2003年 | 282篇 |
2002年 | 264篇 |
2001年 | 225篇 |
2000年 | 173篇 |
1999年 | 167篇 |
1998年 | 134篇 |
1997年 | 133篇 |
1996年 | 116篇 |
1995年 | 109篇 |
1994年 | 97篇 |
1993年 | 53篇 |
1992年 | 54篇 |
1991年 | 31篇 |
1990年 | 33篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有8578条查询结果,搜索用时 15 毫秒
51.
The use of a low-temperature (0 degrees C) bath-assisted coupled capillary for the separation of naphthalene-2,3-dicarboxaldehyde (NDA)-derivatized dopamine and norepinephrine using the sweeping-micellar electrokinetic capillary chromatography (MEKC) mode is described. In this technique, a capillary consisting of two portions with different inside diameters is used. Therefore, the field strength inside the capillary is different. Hence, the electrophoretic migration velocities of the analytes and the electro-osmotic flow (EOF) also are different. Furthermore, when a portion of the capillary (wide portion, used for sweeping) is immersed in a low-temperature bath, the viscosity of the buffer and the retention factor of the analytes inside are increased. Thus, not only are the interactions between the SDS micelles and the analytes increased, but the SDS-analytes also move more slowly. As a result, a more complete separation can be achieved, even when the sample injection volume is large, up to approximately 2 microL. In general, when the volume of an injected sample is larger, the effects of sweeping and separation would become insufficient, especially when the retention values (k) of the analytes are quite different. However, this limitation can be improved when the low-temperature bath/coupled capillary/sweeping-MEKC mode is used. 相似文献
52.
A novel method for the determination of proteins in aqueous solutions has been developed based on the enhancement of resonance light scattering (RLS) of Ag nanoparticles in the presence of proteins. Factors including acidity of the media, concentration of Ag hydrosol, reaction time, temperature, and interference of non-protein substances were investigated. Under the optimal conditions, with the enhanced RLS signals at 452nm, the linear ranges of calibration curves were 0–0.8µgmL–1 for bovine serum albumin (BSA), 0–1.2µgmL–1 for human serum albumin (HSA), and 0–2.5µgmL–1 for human -IgG (-IgG), respectively. The detection limits were 1.3ngmL–1 for BSA, 10ngmL–1 for HAS, and 5.7ngmL–1 for -IgG.This method has been applied to the analysis of synthetic samples and real human serum samples, and the results were in good agreement with those reported by the hospital, indicating that the method presented here is not only sensitive and simple, but also reliable and suitable for practical applications. 相似文献
53.
PRODUCTION OF LIGHTOLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅱ. PROMOTION EFFECT OF MnO PROMOTER 下载免费PDF全文
IntroductionItilasbeenshot'-nthattileadditionofMnOpromotertoFocatal}stcanresultinaremarkableimprovementinthesclectivit}'to11ghtalkenesforCOh}!drogenationll'l.Ho-c'cvcr.thecadetofMnOonCH4formationandCOconversionisvery'ambigUouslltolMoreover.MnOpromotergrca… 相似文献
54.
Karl Sigman 《Queueing Systems》1992,11(4):429-442
General exact light traffic limit theorems are given for the distribution of steadystate workloadV, in open queueing networks having as input a general stationary ergodic marked point process {(t
n
,K
n
)n0 (where tn denotes the arrival time and Kn the routing and service times of the nth customer). No independence assumptions of any kind are required of the input. As the light traffic regime, it is only required that the Palm distribution for the exogenous interarrival time converges weakly to infinity (while the service mechanism is not allowed to change much). As is already known in the context of a single-server queue, work is much easier to deal with mathematically in light traffic than is customer delayD, and consequently, our results are far more general than existing results forD. We obtain analogous results for multi-channel and infinite-channel queues. In the context of open queueing networks, we handle both the total workload in the network as well as the workload at isolated nodes.Research supported in part by the Japan Society for the Promotion of Science during the author's fellowship in Tokyo, and by NSF Grant DDM 895 7825. 相似文献
55.
56.
57.
58.
59.
本文采用远场光斑法和光强法测量了石英单模光纤的数值孔径.实验结果表明,由光纤耦合条件不同导致的光斑形状变化,对数值孔径的测量影响不大,单模光纤的纤芯直径小,导致出射光存在较强的衍射现象,对数值孔径的测量造成较大的影响,无论采用光斑法还是光强法,需以衍射第1次极大为计算标准,尽量选择光斑中心为亮斑时测量其数值孔径.此外,... 相似文献
60.
利用光纤中的量子几何相位(又称Berry相位),制作了单模光纤的线偏振光偏振面旋转器,并对器件进行了测量.实验数据表明,这种光纤偏振旋转器对光偏振面的旋转基本符合理论预计.对偏差进行处理后得到修正的定标公式,可更精确地反映出此光纤偏振旋转器的特性. 相似文献