全文获取类型
收费全文 | 31583篇 |
免费 | 3441篇 |
国内免费 | 3304篇 |
专业分类
化学 | 26125篇 |
晶体学 | 808篇 |
力学 | 1848篇 |
综合类 | 263篇 |
数学 | 508篇 |
物理学 | 8776篇 |
出版年
2024年 | 16篇 |
2023年 | 273篇 |
2022年 | 561篇 |
2021年 | 706篇 |
2020年 | 924篇 |
2019年 | 943篇 |
2018年 | 1012篇 |
2017年 | 1389篇 |
2016年 | 1586篇 |
2015年 | 1228篇 |
2014年 | 1397篇 |
2013年 | 3140篇 |
2012年 | 2073篇 |
2011年 | 1835篇 |
2010年 | 1669篇 |
2009年 | 1944篇 |
2008年 | 1688篇 |
2007年 | 1823篇 |
2006年 | 1625篇 |
2005年 | 1427篇 |
2004年 | 1297篇 |
2003年 | 1143篇 |
2002年 | 963篇 |
2001年 | 835篇 |
2000年 | 863篇 |
1999年 | 793篇 |
1998年 | 661篇 |
1997年 | 575篇 |
1996年 | 460篇 |
1995年 | 517篇 |
1994年 | 427篇 |
1993年 | 380篇 |
1992年 | 319篇 |
1991年 | 244篇 |
1990年 | 229篇 |
1989年 | 209篇 |
1988年 | 250篇 |
1987年 | 227篇 |
1986年 | 142篇 |
1985年 | 101篇 |
1984年 | 108篇 |
1983年 | 36篇 |
1982年 | 84篇 |
1981年 | 49篇 |
1980年 | 35篇 |
1979年 | 45篇 |
1978年 | 21篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
81.
提出了折射率温敏式光纤温度传感器的理论模型,包括子午光线和偏射光线的影响,讨论了多模光纤的弯曲损耗,理论的分析和结果与实验相当一致。 相似文献
82.
83.
A method employing a wide pore polymeric reversed phase column has been developed for the separation of most of the chlorophylls and related compounds previously described as occurring in marine microalgae. The high selectivity toward molecular shape of this kind of stationary phase has enabled compounds of very similar structure, such as chlorophylls c1, c2 and Mg-divinylpheoporphyrin a5 monomethyl ester, and chlorophyll a and the phytol-substituted chlorophyll c-like pigments, which commonly coelute on monomeric bonded phases, to be resolved in a single run. Some of these pigments, formerly thought to be a single compound, have, in fact, been demonstrated to be groups of two or more. The method has been successfully applied to both algal cultures and natural sea water samples. When visible light absorbance detection was used, the method proved suitable for separation of various carotenoids. 相似文献
84.
脂肪乳剂Intralipid代谢产物的高效液相色谱测定 总被引:2,自引:0,他引:2
本文介绍了利用HPLC色谱柱前衍生化技术简便,正确和灵敏地测定血清中游离脂肪酸的方法。在最佳条件下,一些脂肪酸的最低检知量为0.04μg。方法已用于脂肪乳剂Intralipid在诱发急性坏死性胰腺炎动物体内代谢产物测定。 相似文献
85.
86.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
87.
88.
The stability of Ochratoxin A during its extraction using different extraction techniques has been evaluated. Microwave-assisted extraction and pressurised liquid extraction, in addition to two other reference methods of extraction, i.e. ultrasound-assisted and magnetic stirring-assisted extraction, were evaluated. The effect of extraction temperature using the cited techniques was checked.The results show that Ochratoxin A can be extracted using microwave-assisted extraction at temperatures up to 150 °C without degradation. Pressurised liquid extraction can be used at temperatures up to 100 °C, for extraction times of less than 30 min. Further, both ultrasound-assisted extraction and magnetic stirring extraction can be applied at temperatures up to 65 °C.High-performance liquid chromatography combined with fluorescence detection using a Chromolith RP-18e column at a flow rate of 5 mL min−1 was used to quantify the Ochratoxin A. The retention time for the Ochratoxin A was 1.3 min. The limits of detection (LOD) and of quantification (LOQ) were 0.03 and 0.10 μg L−1, respectively. 相似文献
89.
HPLC-MS/MS技术在中华绒螯蟹硝基呋喃类代谢物残留量检测中的应用 总被引:3,自引:0,他引:3
建立了中华绒螯蟹中硝基呋喃类代谢物残留量的液相色谱-串联质谱检测方法.取均质后的中华绒螯蟹可食部分样品,用盐酸水解组织中蛋白结合代谢物,经2-硝基苯甲醛37℃过夜衍生化,调节pH值至约7.0~7.4后,用乙酸乙酯提取,正己烷净化.选用电喷雾离子源,在正离子、多反应监测方式模式下进行定性,以同位素内标法进行定量.方法的检出限为0.5 μg·kg-1,工作曲线的线性范围为1.25~50.0 μg·L-1.在添加浓度为0.5~10.0 μg·kg-1的范围内,AMOZ、SEM、AHD和AOZ的回收率分别在92.8%~106%、84.5%~94.6%、80.6%~98.6%和88.4%~105%之间,相对标准偏差均小于10%. 相似文献
90.
The knowledge of hydrocarbon/water phase equilibria is important in the design and operation of equipment for petroleum transport and refining and petrochemical plants. The presence of water in a hydrocarbon mixture can affect the product quality and damage the operation equipment due to corrosion and formation of gas hydrates. Tracing the concentration of hydrocarbons in aqueous media is also important for technical purposes like preventing oil spills and for ecological concerns such as predicting the fate of these organic pollutants in the environment. 相似文献