全文获取类型
收费全文 | 146310篇 |
免费 | 33025篇 |
国内免费 | 25135篇 |
专业分类
化学 | 98747篇 |
晶体学 | 1985篇 |
力学 | 9057篇 |
综合类 | 754篇 |
数学 | 18259篇 |
物理学 | 75668篇 |
出版年
2023年 | 1968篇 |
2022年 | 2307篇 |
2021年 | 3021篇 |
2020年 | 3728篇 |
2019年 | 4118篇 |
2018年 | 3641篇 |
2017年 | 4173篇 |
2016年 | 5370篇 |
2015年 | 5712篇 |
2014年 | 6220篇 |
2013年 | 9212篇 |
2012年 | 10677篇 |
2011年 | 12197篇 |
2010年 | 13748篇 |
2009年 | 13693篇 |
2008年 | 8200篇 |
2007年 | 7207篇 |
2006年 | 6468篇 |
2005年 | 6238篇 |
2004年 | 6332篇 |
2003年 | 5136篇 |
2002年 | 4958篇 |
2001年 | 4822篇 |
2000年 | 3774篇 |
1999年 | 3964篇 |
1998年 | 3182篇 |
1997年 | 2961篇 |
1996年 | 3223篇 |
1995年 | 3535篇 |
1994年 | 3460篇 |
1993年 | 3424篇 |
1992年 | 2935篇 |
1991年 | 2519篇 |
1990年 | 2139篇 |
1989年 | 2129篇 |
1988年 | 2056篇 |
1987年 | 1331篇 |
1986年 | 1372篇 |
1985年 | 1024篇 |
1984年 | 1082篇 |
1983年 | 466篇 |
1982年 | 959篇 |
1981年 | 789篇 |
1980年 | 821篇 |
1979年 | 562篇 |
1978年 | 568篇 |
1977年 | 666篇 |
1976年 | 1075篇 |
1973年 | 465篇 |
1972年 | 557篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
71.
72.
73.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
74.
Pu Duan Bo Zhi Luke Coburn Christy L. Haynes Klaus Schmidt-Rohr 《Magnetic resonance in chemistry : MRC》2020,58(11):1130-1138
The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave-assisted reaction of citric acid and ethylenediamine was investigated by 13C, 13C{1H}, 1H─13C, 13C{14N}, and 15N solid-state nuclear magnetic resonance (NMR) experiments. 13C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases. 15N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved 13C NMR peaks, including an unusual ═CH signal at 84 ppm (1H chemical shift of 5.8 ppm) and ═CN2 at 155 ppm, and two distinctive 15N NMR resonances near 80 and 160 ppm proved the presence of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross-peaks in a 1H─13C HETCOR spectrum with brief 1H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative 13C and 15N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in 13C chemical-shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation. 相似文献
75.
Jia Yang Xingang Li Wenjun Li Xin Xi Qian Du Feng Pan Songqing Liu 《Biomedical chromatography : BMC》2020,34(8):e4857
Because of its unpredictable side effects and efficacy, the anticancer drug docetaxel (DTX) requires improved characterisation of its pharmacokinetic profiles through population pharmacokinetic studies. A sensitive and rugged LC–MS/MS method for the detection of DTX in human plasma was developed and optimised using paclitaxel as an internal standard (IS). The plasma samples underwent rapid extraction using hybrid solid-phase extraction-protein precipitation. The analyte and IS were separated with an isocratic system on a Zorbax Eclipse Plus C18 column using water containing 0.05% acetic acid along with 20 μM of sodium acetate and methanol (30/70, v/v) as the mobile phase. Quantification was performed using a triple quadrupole mass spectrometer through multiple reaction monitoring in positive mode, using the m/z 830.3 → 548.8 and m/z 876.3 → 307.7 transitions for DTX and paclitaxel, respectively. The range of the calibration curve was 1–500 ng/mL for DTX, and the linear correlation coefficient was >0.99. The accuracies ranged from −4.6 to 4.2%, and the precision was no higher than 7.0% for the analytes. No significant matrix effect was observed. Both DTX and the IS showed considerable recovery. This method was finally applied to the establishment of a population pharmacokinetic model to optimise the clinical use of DTX. 相似文献
76.
77.
Dr. Wan‐Ling Liu Ni‐Shin Yang Ya‐Ting Chen Stephen Lirio Cheng‐You Wu Prof. Chia‐Her Lin Prof. Hsi‐Ya Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):115-119
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors. 相似文献
78.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
79.
Xin Xiangjun Wang Zhuo Yang Qinglan Li Fagen 《International Journal of Theoretical Physics》2020,59(3):918-929
International Journal of Theoretical Physics - Designated verifier signatures are very useful in the applications such as e-voting and auction. In this paper, an identity-based quantum designated... 相似文献
80.