全文获取类型
收费全文 | 7049篇 |
免费 | 1127篇 |
国内免费 | 716篇 |
专业分类
化学 | 4680篇 |
晶体学 | 72篇 |
力学 | 413篇 |
综合类 | 41篇 |
数学 | 642篇 |
物理学 | 3044篇 |
出版年
2024年 | 26篇 |
2023年 | 149篇 |
2022年 | 199篇 |
2021年 | 203篇 |
2020年 | 261篇 |
2019年 | 220篇 |
2018年 | 207篇 |
2017年 | 189篇 |
2016年 | 301篇 |
2015年 | 299篇 |
2014年 | 370篇 |
2013年 | 511篇 |
2012年 | 547篇 |
2011年 | 589篇 |
2010年 | 397篇 |
2009年 | 403篇 |
2008年 | 426篇 |
2007年 | 363篇 |
2006年 | 355篇 |
2005年 | 330篇 |
2004年 | 274篇 |
2003年 | 201篇 |
2002年 | 222篇 |
2001年 | 173篇 |
2000年 | 168篇 |
1999年 | 176篇 |
1998年 | 128篇 |
1997年 | 128篇 |
1996年 | 151篇 |
1995年 | 107篇 |
1994年 | 113篇 |
1993年 | 108篇 |
1992年 | 100篇 |
1991年 | 82篇 |
1990年 | 63篇 |
1989年 | 74篇 |
1988年 | 52篇 |
1987年 | 46篇 |
1986年 | 39篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有8892条查询结果,搜索用时 0 毫秒
951.
952.
953.
Peng Yu Guoping Yang Hongyi Tan Zeneng Cheng Ming Song Zhenkun Gu Xiao Li 《Chromatographia》2011,73(9-10):921-927
A sensitive, specific and rapid high performance liquid chromatography?Catmospheric pressure chemical ionization source-tandem mass spectrometry (LC-APCI-MS-MS) method for the determination of pilocarpine in human plasma was developed and validated. The method is based on liquid?Cliquid extraction, followed by a reversed-phase liquid chromatographic separation, and detected by means of tandem mass spectrometry. The linear calibration curve covered a concentration range of 2?C500 ??g L?1. The intra- and inter-day precisions for pilocarpine were <10% and the accuracies were between 90 and 110%. The method was applied successfully to a pharmacokinetic study involving 20 healthy Chinese male volunteers after oral administration of 6 mg pilocarpine. 相似文献
954.
Xi‐Bin Xiao Yue‐Xing Lin Geng‐Bo Xu Xu‐Bo Gong Ying Gu Jie‐Feng Tong Jing Yang 《Helvetica chimica acta》2011,94(9):1594-1599
Two new alkaloids, mappine A ( 1 ) and mapposidic acid ( 2 ), together with eleven known compounds, were isolated from the stems of Mappianthus iodoides Hand.‐Mazz. Their structures were elucidated by means of spectroscopic and mass‐spectrometric analyses, particularly 1D‐ and 2D‐NMR spectroscopy. The cytotoxic activities of the two new alkaloids were also evaluated. 相似文献
955.
Zhijie Gu Tatsuya Kanto Kousuke Tsuchiya Takeshi Shimomura Kenji Ogino 《Journal of polymer science. Part A, Polymer chemistry》2011,49(12):2645-2652
Novel block copolymers, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) (P3HT‐b‐PEO) were synthesized via Suzuki coupling reaction of P3HT and PEO homopolymers. The copolymers were characterized by NMR, gel permeation chromatography, differential scanning calorimeter, and UV–vis measurements. A series of devices based on the block copolymers with a fullerene derivative were evaluated after thermal or solvent annealing. The device using P3HT‐b‐PEO showed higher efficiency than using P3HT blend after thermal annealing. Phase‐separated structures in the thin films of block copolymer blends were investigated by atomic force microscopy to clarify the relationship between morphologies constructed by annealing and the device performance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
956.
Lin Gu Xianhong Wang Xuesi Chen Xiaojiang Zhao Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5162-5168
Aliphatic poly(urethane‐amine) (PUA) was synthesized from copolymerization of CO2 and 2‐methylaziridine (MAZ) using Y(CCl3COO)3‐ZnEt2‐glycerine coordination catalyst, the urethane content of PUA was over 80%, and its yield could reach 90%. PUA with molecular weight as high as 31.0 kg/mol was obtained when the copolymerization reaction was carried out in N,N‐dimethylacetamide (DMAc), mainly due to the good solubility of PUA in DMAc. PUA exhibited reversible thermo‐responsive property in deionized water, and the lower critical solution temperature (LCST) was highly sensitive to its urethane content and molecular weight, which was observed in a broad window from 37 to 90 °C. Furthermore, the phase transition behavior could also be controlled by change of pH value. When the pH value of the PUA aqueous solution changed from 9.2 to 13, the LCST value of the solution decreased from 48.4 °C to 30 °C. Therefore, the PUA showed thermo‐ and pH‐ dual responsive performance in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
957.
Two new complexes, {[Co(INAIP) · H2O] · 2H2O}n ( 1 ), and {[Cu(INAIP)] · H2O}n ( 2 ) [H2INAIP = 5‐(isonicotinamido)isophthalic acid] were synthesized under hydrothermal conditions, and characterized by single‐crystal X‐ray structure determination, thermogravimetric analysis, X‐ray powder diffraction, and magnetic studies. In complex 1 both CoII atoms and INAIP2– ligands act as four‐connected node, whereas in 2 both CuII atoms and INAIP2– ligands act as three‐connected node. 相似文献
958.
Jiajian Gao Chunmiao Jia Jing Li Meiju Zhang Fangna Gu Guangwen Xu Ziyi Zhong Fabing Su 《天然气化学杂志》2013,(6):919-927
The correlation between phase structures and surface acidity of Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in the production of synthetic natural gas(SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al2O3 catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al2O3 supports were adjusted by calcining the commercial γ-Al2O3 at different temperatures(600–1200 C). CO methanation reaction was carried out in the temperature range of 300–600 C at different weight hourly space velocities(WHSV = 30000 and 120000 mL·g-1h-1) and pressures(0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al2O3 supports due to the rapid decrease of the specific surface area and acidity of Al2O3 supports. Interestingly, Ni catalysts supported on Al2O3 calcined at 1200 C(Ni/Al2O3-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al2O3-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures(600, 800 and 1000 C). These findings would therefore be helpful to develop Ni/Al2O3 methanation catalyst for SNG production. 相似文献
959.
960.
采用氨基-过硫酸盐氧化还原引发体系, 先实现了甲基丙烯酸羟乙酯(HEMA)在微米级硅胶微粒表面的引发接枝聚合, 制得高接枝度的接枝微粒PHEMA/SiO2. 然后使接枝大分子PHEMA的侧羟基与5-氯-8-羟基喹啉(CHQ)发生亲核取代反应, 将8-羟基喹啉(HQ)基团键合在接枝大分子侧链, 使接枝大分子PHEMA实现8-羟基喹啉功能化转变, 制得表面含有高密度HQ基团的功能接枝微粒HQ-PHEMA/SiO2, 考察研究了功能微粒HQ-PHEMA/SiO2对Cd2+离子的强螯合吸附作用. 在此基础上, 采用本课题组建立的新的分子表面印迹技术, 以Cd2+离子为模板离子, 二氯乙醚为交联剂, 对接枝在硅胶表面的功能大分子链HQ-PHEMA进行了离子印迹, 制备了Cd2+离子表面印迹材料IIP-HQP/SiO2, 深入考察研究了其离子识别与结合特性. 实验结果表明, 该离子表面印迹材料对Cd2+离子具有特异的识别选择性与优良的结合亲和性, 相对于Cu2+和Pb2+两种对比离子, 印迹材料IIP-HQP/SiO2对Cd2+离子的识别选择性系数分别高达25.52和22.91, 显示出超高的离子识别能力. 相似文献