全文获取类型
收费全文 | 4024篇 |
免费 | 124篇 |
国内免费 | 14篇 |
专业分类
化学 | 2690篇 |
晶体学 | 97篇 |
力学 | 121篇 |
数学 | 335篇 |
物理学 | 919篇 |
出版年
2023年 | 32篇 |
2022年 | 82篇 |
2021年 | 76篇 |
2020年 | 97篇 |
2019年 | 96篇 |
2018年 | 72篇 |
2017年 | 68篇 |
2016年 | 106篇 |
2015年 | 103篇 |
2014年 | 135篇 |
2013年 | 305篇 |
2012年 | 263篇 |
2011年 | 292篇 |
2010年 | 148篇 |
2009年 | 147篇 |
2008年 | 246篇 |
2007年 | 216篇 |
2006年 | 170篇 |
2005年 | 139篇 |
2004年 | 113篇 |
2003年 | 76篇 |
2002年 | 77篇 |
2001年 | 55篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 35篇 |
1995年 | 38篇 |
1994年 | 40篇 |
1993年 | 43篇 |
1992年 | 39篇 |
1991年 | 20篇 |
1990年 | 24篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 41篇 |
1984年 | 42篇 |
1983年 | 42篇 |
1982年 | 42篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 41篇 |
1978年 | 49篇 |
1977年 | 33篇 |
1976年 | 27篇 |
1974年 | 26篇 |
1973年 | 20篇 |
排序方式: 共有4162条查询结果,搜索用时 0 毫秒
101.
102.
Venkata Rami Reddy Vaka Jaswanth Kumar Inamadugu Nageswara Rao Pilli Mullangi Ramesh Hussain Reddy Katreddi 《Biomedical chromatography : BMC》2013,27(11):1406-1412
An improved, simple and highly sensitive LC‐MS/MS method has been developed and validated for quantification of febuxostat with 100 μL human plasma using febuxostat‐d7 as an internal standard (IS) according to regulatory guidelines. The analyte and IS were extracted from human plasma via liquid–liquid extraction using diethyl ether. The chromatographic separation was achieved on a Zorbax C18 column using a mixture of acetonitrile and 5 mm ammonium formate (60:40, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The total run time was 5.0 min and the elution of febuxostat and IS occurred at 1.0 and 1.5 min, respectively. A linear response function was established for the range of concentrations 1–6000 ng/mL (r > 0.99). The precursor to product ion transitions monitored for febuxostat and IS were m/z 317.1 → 261.1 and 324.2 → 262.1, respectively. The intra‐ and inter‐day precisions (%RSD) were within 1.29–9.19 and 2.85–7.69%, respectively. The proposed method was successfully applied to pharmacokinetic studies in humans. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
103.
Condensation of uracil derivatives (1,3,4) with acetone in the presence of triethylamine gave pyranopyrimidines (2,5,6). 相似文献
104.
Ramesh Naik 《合成通讯》2013,43(10):1723-1726
Dimethylsulfoxide (DMSO) oxidizes benzyl ethers into corresponding benzaldehydes at 110°C; the reaction is accelerated by 49% aq. HBr. The conditions work well for different aryl‐substituted benzyl ethers. This protocol is inert toward dialkyl ethers. 相似文献
105.
B. H. Doreswamy Chandra K. Mantelingu M. A. Sridhar M. Mahendra 《Research on Chemical Intermediates》2014,40(8):2659-2665
The isolation of stable carbenes of the Arduengo and Wanzlick type has prompted us to look for stable nitrenium ions of the related structural type 1-Hydroxy-3-methyl benzotriazolium trifluromethane sulfonate. Nitrenium ions are azocations with structure and survive long enough under in vitro conditions to bind with biological nucleophiles, i.e. DNA bases, and play an important role in carcinogenic processes involving the metabolism of aromatic amines. The title compound (C15H16F3N6O5S) was isolated and crystallized in the monoclinic space group Cc with cell parameters a = 19.866(1) Å, b = 13.128(9) Å, c = 7.673(5) Å, and Z = 4. The structure has both intra- and intermolecular hydrogen bonds. 相似文献
106.
107.
Ashok Zakkula Sreekanth Dittakavi Malika Muskan Maniyar Naveem Syed Suresh P. Sulochana Mohd Zainuddin Ramesh Mullangi 《Biomedical chromatography : BMC》2019,33(11)
Isocitrate dehydrogenase (IDH) inhibitors comprise a novel class of anticancer drugs, which are approved to treat acute myeloid leukemia patients having mutations on IDH1/2. We report the development and validation of a high‐performance liquid chromatography (HPLC) method for the simultaneous quantitation of IDH inhibitors, namely enasidenib (EDB), ivosidenib (IDB) and vorasidenib (VDB), in mouse plasma as per the US Food and Drug Administration regulatory guidelines. The method involves extraction of EDB, IDB and VDB along with internal standard (IS; phenacetin) from mouse plasma (100 μl) using a simple protein precipitation process. The chromatographic analysis was performed on an HPLC system using a gradient mobile phase (comprising 10 mm ammonium acetate and acetonitrile in a flow‐gradient) and an X‐Terra Phenyl column. The UV detection wave length was set at λmax 265 nm. EDB, IDB, VDB and the IS eluted at 7.36, 8.60, 9.50 and 5.12 min, respectively, with a total run time of 10 min. The calibration curve was linear over a concentration range of 0.20–12.5 μg/ml for EDB and 0.50–12.5 μg/ml for IDB and VDB (r2 = ≥0.998 for all of the analytes). Validation results met the acceptance criteria. The validated HPLC method was successfully applied to a pharmacokinetic study in mice. 相似文献
108.
Murthy I. S. Sreenivasulu R. Alluraiah G. Ramesh Raju R. 《Russian Journal of General Chemistry》2019,89(8):1718-1723
Russian Journal of General Chemistry - A series of novel 1,2-isoxazole-pyridobenzimidazole is synthesized. Structures of the products are supported by 1H and 13C NMR, and mass spectra. All... 相似文献
109.
N. Senthilkumar Y. S. Somannavar Brajesh Kumar Sinha G. K. A. S. S. Narayan Ramesh Dandala 《合成通讯》2013,43(2):268-276
A simple synthetic route for active metabolites of carvedilol is reported. The metabolites 4′-hydroxycarvedilol and 5′-hydroxycarvedilol have exhibited high activity for β-blockade. We have disclosed syntheses of 4′-hydroxycarvedilol and 5′-hydroxycarvedilol from commercially available vanillin and isovanillin, respectively. 相似文献
110.
K. A. Sree Raj Afsal S. Shajahan Dr. Brahmananda Chakraborty Dr. Chandra Sekhar Rout 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6662-6669
In this work, the ternary hybrid structure VSe2/SWCNTs/rGO is reported for supercapacitor applications. The ternary composite exhibits a high specific capacitance of 450 F g−1 in a symmetric cell configuration, with maximum energy density of 131.4 Wh kg−1 and power density of 27.49 kW kg−1. The ternary hybrid also shows a cyclic stability of 91 % after 5000 cycles. Extensive density functional theory (DFT) simulations on the structure as well as on the electronic properties of the binary hybrid structure VSe2/SWCNTs and the ternary hybrid structure VSe2/SWCNTs/rGO have been carried out. Due to a synergic effect, there are enhanced density of states near the Fermi level and higher quantum capacitance for the hybrid ternary structure compared to VSe2/SWCNTs, leading to higher energy and power density for VSe2/SWCNTs/rGO, supporting our experimental observation. Computed diffusion energy barrier of electrolyte ions (K+) predicts that ions move faster in the ternary structure, providing higher charge storage performance. 相似文献