全文获取类型
收费全文 | 7280篇 |
免费 | 1344篇 |
国内免费 | 690篇 |
专业分类
化学 | 5076篇 |
晶体学 | 41篇 |
力学 | 432篇 |
综合类 | 44篇 |
数学 | 915篇 |
物理学 | 2806篇 |
出版年
2024年 | 22篇 |
2023年 | 144篇 |
2022年 | 246篇 |
2021年 | 288篇 |
2020年 | 344篇 |
2019年 | 259篇 |
2018年 | 245篇 |
2017年 | 232篇 |
2016年 | 349篇 |
2015年 | 383篇 |
2014年 | 417篇 |
2013年 | 521篇 |
2012年 | 666篇 |
2011年 | 703篇 |
2010年 | 453篇 |
2009年 | 410篇 |
2008年 | 454篇 |
2007年 | 423篇 |
2006年 | 404篇 |
2005年 | 288篇 |
2004年 | 256篇 |
2003年 | 162篇 |
2002年 | 190篇 |
2001年 | 120篇 |
2000年 | 134篇 |
1999年 | 147篇 |
1998年 | 127篇 |
1997年 | 142篇 |
1996年 | 126篇 |
1995年 | 116篇 |
1994年 | 100篇 |
1993年 | 99篇 |
1992年 | 68篇 |
1991年 | 59篇 |
1990年 | 57篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 11篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有9314条查询结果,搜索用时 31 毫秒
81.
Xiaoyan Deng Guihong Liao Qingwu Long Yujiao Gao Hao Peng Hongwu He 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):663-671
Abstract A series of [(substituted phenoxyacetoxy)(substituted phenyl)methyl](methyl)phos- phinates containing fluorine were designed and synthesized. All the synthesized compounds were identified by elemental analysis, IR, 1H NMR, mass spectrometry. O-methyl [(2-fluorophenoxyacetoxy)(2,4-dichlorophenyl)methyl](methyl)phosphinate was further analyzed by X-ray single-crystal diffraction. Their herbicidal activity against a set of weed species was examined. Some of the compounds showed potential herbicidal activity, which provided some indications for further studies on structure modification. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
82.
Hongming Chen Zhenghua Deng Yungui Zheng Wu Xu Guoxiang Wan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1273-1281
Abstract The ion conduction of a blend of poly(oxyethylene) (PEO) and lithium methoxy oligo(oxyethylene) sulfate (SAL8) and its electrochemical characteristics were studied. The maximum ambient conductivity of the blend reaches 1.2 × 10?6 S/cm. The blend exhibits single-ion conduction, excellent mechanical performance, and electrochemical stability. A battery of Li/PEO + SAL8/Li1+xV3O8 has a constant discharge capacity at different discharge current densities up to a certain voltage, while the discharge capacity of Li/P (MEO16-AM) + LiClO4/Li1+xV3O8 decreases with an increase of the discharge current density. 相似文献
83.
84.
Fu-Jun Duan Jin-Chang Ding Hong-Juan Deng Ding-Ben Chen Jiu-Xi Chen Miao-Chang Liu Hua-Yue Wu 《中国化学快报》2013,24(9):793-796
An efficient and facile method for the synthesis of N-substituted pyrroles in moderate to good yields by the Paal–Knorr reaction of γ-diketones with amines in the presence of β-cyclodextrin in aqueous media has been developed.Moreover,this process tolerated diamines(e.g.,para-,meta- or orthophenylenediamine)to construct bis-pyrrole or mono-pyrrole derivates.β-Cyclodextrin can be recovered easily after the reactions and reused without evident loss in activity. 相似文献
85.
Lu Ban Liang Zhao Bang-Li Deng Yan-Ping Huang Zhao-Sheng Liu 《Analytical and bioanalytical chemistry》2013,405(7):2245-2253
A method based on reverse atom transfer radical polymerization (R-ATRP) and molecular crowding has been used for design and synthesis of monolithic molecularly imprinted polymers (MIPs) capable of recognizing ibuprofen (IBU). 4-Vinylpyridine (4-VP) was used as the functional monomer, and ethylene glycol dimethacrylate (EDMA) was the crosslinking monomer. Azobisisobutyronitrile (AIBN)–CuCl2–N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) was used as the initiating system. Compared with conventional radical polymerization-based IBU-MIPs, the imprinting effects of the obtained IBU-MIPs was enhanced, suggesting the merit of combination of reverse ATRP and molecular crowding. In addition, it was found that the polymerization time of the molecularly imprinted monolithic column, the amount of template, the degree of crosslinking, and the composition of mobile phase greatly affected retention of the template and the performance of molecular recognition . Figure
Schematic representation of molecular imprinting under molecular crowding conditions in the presence of R-ATRP 相似文献
86.
The anion derived from diethyl malonate reacts with a series of halides readly under microwave irradiation, and the isolated yield of alkylated products varying from 64% to 86%. 相似文献
87.
Gold (Au) nanoparticle arrays with tunable morphology and optical characteristics were synthesized by in-situ self-assembly process that occurred on the surface of aniline-modified polystyrene (PS) microspheres. The method can be used to control the growth of both single and aggregated Au nanoparticle arrays on PS microsphere surface. This method could also be adapted for synthesis of other noble metals hybrid materials, which opens exciting opportunities for their practical applications. 相似文献
88.
Zheng Wang Shuai Luo Dr. Shoude Zhang Wu‐Lin Yang Yang‐Zi Liu Prof. Dr. Honglin Li Prof. Dr. Xiaoyan Luo Prof. Dr. Wei‐Ping Deng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6739-6745
The first catalytic enantioselective 1,3‐dipolar cycloaddition of azomethine ylides to α‐aminoacrylate catalyzed by a AgOAc/ferrocenyl oxazolinylphosphine (FOXAP) system was developed, which exhibits excellent exo‐ and enantioselectivity (92–99 % ee). This process provides efficient access to useful 4‐aminopyrrolidine‐2,4‐dicarboxylic acid (APDC)‐like compounds containing a unique quaternary α‐amino acid unit. 相似文献
89.
新一代运载火箭时序仿真系统具有数字电路速度快、集成度高的特点,系统要求发出多路高精度时序、时串信号以满足新一代运载火箭地面测试设备的检查与校准需求,因此信号完整性问题在系统设计中不容忽视。针对仿真系统的典型模块(USB 3.0 Super-speed差分线、FPGA外设数据走线、时钟走线)进行建模分析仿真得出PCB硬件电路设计参数,给出时序仿真系统设计信号完整性问题的抑制和解决方法,优化了板级信号质量,改善系统可靠性、工作连续性和输出精度,可有效提高新一代运载火箭测试效率和测试可靠性。 相似文献
90.
砂尘浓度指标严重影响砂尘风洞试验效果;在大型砂尘风洞中准确的测量及有效的控制砂尘浓度是砂尘风洞设备研制中的两个关键问题;针对动态试验工况环境中浓度传感器标定的问题,分析了浓度测量时标定参数与风速和浓度的关系,使用模型树算法建立了三者之间的关系模型,以此模型来预测各种动态情况下的标定参数;针对复杂环境下浓度动态控制问题,采用专家PID算法,提出了多回路控制系统结构和专家规则;工程实践表明该测量和控制方法满足了动态试验环境的需求,取得了良好效果;模型树算法和专家PID系统能有效的解决动态工况下砂尘浓度的测量与控制问题。 相似文献