全文获取类型
收费全文 | 282845篇 |
免费 | 3110篇 |
国内免费 | 842篇 |
专业分类
化学 | 151903篇 |
晶体学 | 4310篇 |
力学 | 12423篇 |
综合类 | 34篇 |
数学 | 32198篇 |
物理学 | 85929篇 |
出版年
2020年 | 2381篇 |
2019年 | 2594篇 |
2018年 | 3453篇 |
2017年 | 3410篇 |
2016年 | 4988篇 |
2015年 | 3139篇 |
2014年 | 4807篇 |
2013年 | 11641篇 |
2012年 | 9091篇 |
2011年 | 11010篇 |
2010年 | 7790篇 |
2009年 | 7481篇 |
2008年 | 10172篇 |
2007年 | 10290篇 |
2006年 | 9640篇 |
2005年 | 8749篇 |
2004年 | 8015篇 |
2003年 | 7205篇 |
2002年 | 7072篇 |
2001年 | 7586篇 |
2000年 | 5921篇 |
1999年 | 4562篇 |
1998年 | 4009篇 |
1997年 | 3976篇 |
1996年 | 3745篇 |
1995年 | 3444篇 |
1994年 | 3609篇 |
1993年 | 3316篇 |
1992年 | 3794篇 |
1991年 | 3780篇 |
1990年 | 3708篇 |
1989年 | 3571篇 |
1988年 | 3653篇 |
1987年 | 3555篇 |
1986年 | 3363篇 |
1985年 | 4461篇 |
1984年 | 4735篇 |
1983年 | 3939篇 |
1982年 | 4096篇 |
1981年 | 4022篇 |
1980年 | 3977篇 |
1979年 | 3962篇 |
1978年 | 4279篇 |
1977年 | 4176篇 |
1976年 | 4252篇 |
1975年 | 3912篇 |
1974年 | 3952篇 |
1973年 | 4115篇 |
1972年 | 2874篇 |
1971年 | 2405篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
JETP Letters - At the resonant passage of a plane elastic shear wave through an acoustically continuous heterostructure consisting of magnetic and nonmagnetic layers in a symmetric nonmagnetic... 相似文献
82.
Kaplunov I. A. Kolesnikov A. I. Kropotov G. I. Rogalin V. E. 《Optics and Spectroscopy》2019,126(3):191-194
Optics and Spectroscopy - The transmission of intrinsic, antimony-doped, and gallium-doped Ge single crystals in the THz spectral range have been experimentally investigated. It is shown that the... 相似文献
83.
Dr. Liat Avram Dr. Václav Havel Ronit Shusterman-Krush Dr. Mark A. Iron Dr. Moritz Zaiss Prof. Vladimír Šindelář Dr. Amnon Bar-Shir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1687-1690
The accumulated knowledge regarding molecular architectures is based on established, reliable, and accessible analytical tools that provide robust structural and functional information on assemblies. However, both the dynamicity and low population of noncovalently interacting moieties within studied molecular systems limit the efficiency and accuracy of traditional methods. Herein, the use of a saturation transfer-based NMR approach to study the dynamic binding characteristics of an anion to a series of synthetic receptors derived from bambusuril macrocycles is demonstrated. The exchange rates of BF4− are mediated by the side chains on the receptor (100 s−1<kex<5000 s−1), which play a critical role in receptor-anion binding dynamics. The signal amplification obtained with this approach allows for the identification of different types of intermolecular interactions between the receptor and the anion, something that could not have been detected by techniques hitherto used to study molecular assemblies. These findings, which are supported by a computational molecular dynamic study, demonstrate the uniqueness and added value of this NMR method. 相似文献
84.
Yingchun Wu Haipeng Li Xuecheng Wu Gérard Gréhan Lutz Mädler Cyril Crua 《Proceedings of the Combustion Institute》2019,37(3):3211-3218
Droplet evaporation characterization, although of great significance, is still challenging. The recently developed phase rainbow refractometry (PRR) is proposed as an approach to measuring the droplet temperature, size as well as evaporation rate simultaneously, and is applied to a single flowing n-heptane droplet produced by a droplet-on-demand generator. The changes of droplet temperature and evaporation rate after a transient spark heating are reflected in the time-resolved PRR image. Results show that droplet evaporation rate increases with temperature, from ?1.28 m2/s at atmospheric 293 K to a range of (?1.5, ?8) m2/s when heated to (294, 315) K, agreeing well with the Maxwell and Stefan–Fuchs model predictions. Uncertainty analysis suggests that the main source is the indeterminate gradient inside droplet, resulting in an underestimation of droplet temperature and evaporation rate. With the demonstration on simultaneous measurements of droplet refractive index as well as droplet transient and local evaporation rate in this work, PRR is a promising tool to investigate single droplet evaporation in real engine conditions. 相似文献
85.
86.
87.
88.
89.
90.
Design and development of a two‐dimensional system based on hydrophilic and reversed‐phase liquid chromatography with on‐line sample treatment for the simultaneous separation of excreted xenobiotics and endogenous metabolites in urine
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Diego García‐Gómez Encarnación Rodríguez‐Gonzalo Rita Carabias‐Martínez 《Biomedical chromatography : BMC》2015,29(8):1190-1196
In the present work we describe a two‐dimensional liquid chromatographic system (2D‐LC) with detection by mass spectrometry (MS) for the simultaneous separation of endogenous metabolites of clinical interest and excreted xenobiotics deriving from exposure to toxic compounds. The 2D‐LC system involves two orthogonal chromatographic modes, hydrophilic interaction liquid chromatography (HILIC) to separate polar endogenous metabolites and reversed‐phase (RP) chromatography to separate excreted xenobiotics of low and intermediate polarity. Additionally, the present proposal has the novelty of incorporating an on‐line sample treatment based on the use of restricted access materials (RAMs), which permits the direct injection of urine samples into the system. The work is focused on the instrumental coupling, studying all possible options and attempting to circumvent the problems of solvent incompatibility between the RAM device and the two chromatographic columns, HILIC and RP. The instrumental configuration developed, RAM‐HILIC‐RPLC‐MS/MS, allows the simultaneous assessment of urinary metabolites of clinical interest and excreted compounds derived from exposure to toxic agents with minimal sample manipulation. Thus, it may be of interest in areas such as occupational and environmental toxicology in order to explore the possible relationship between the two types of compounds. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献