全文获取类型
收费全文 | 20068篇 |
免费 | 3912篇 |
国内免费 | 5881篇 |
专业分类
化学 | 14970篇 |
晶体学 | 699篇 |
力学 | 1273篇 |
综合类 | 792篇 |
数学 | 2752篇 |
物理学 | 9375篇 |
出版年
2024年 | 68篇 |
2023年 | 246篇 |
2022年 | 671篇 |
2021年 | 684篇 |
2020年 | 710篇 |
2019年 | 812篇 |
2018年 | 693篇 |
2017年 | 844篇 |
2016年 | 787篇 |
2015年 | 1028篇 |
2014年 | 1267篇 |
2013年 | 1642篇 |
2012年 | 1704篇 |
2011年 | 1834篇 |
2010年 | 1608篇 |
2009年 | 1702篇 |
2008年 | 1867篇 |
2007年 | 1741篇 |
2006年 | 1552篇 |
2005年 | 1274篇 |
2004年 | 1055篇 |
2003年 | 780篇 |
2002年 | 827篇 |
2001年 | 792篇 |
2000年 | 751篇 |
1999年 | 536篇 |
1998年 | 318篇 |
1997年 | 222篇 |
1996年 | 233篇 |
1995年 | 217篇 |
1994年 | 200篇 |
1993年 | 195篇 |
1992年 | 171篇 |
1991年 | 118篇 |
1990年 | 112篇 |
1989年 | 101篇 |
1988年 | 99篇 |
1987年 | 73篇 |
1986年 | 63篇 |
1985年 | 62篇 |
1984年 | 48篇 |
1983年 | 42篇 |
1982年 | 28篇 |
1981年 | 28篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1976年 | 3篇 |
1966年 | 3篇 |
1959年 | 6篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing 下载免费PDF全文
2.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
3.
以4-羟基吲哚为原料,经吲哚环4位乙酰基化、3位亲电取代、酰胺化和还原加氢等反应合成目标化合物7.通过核磁共振氢谱及碳谱对化合物进行结构表征,并对目标化合物进行体外抗氧化生物活性测试.初步生物活性测试结果表明,化合物7a,7b,7c和7d对DPPH·均有很强的清除作用(清除率为85.25%~90.73%),7e,7f,7g,7h作用较差;目标化合物与Vc相比,对·OH的清除作用稍差,最高清除率25.66%(Vc的最高清除率为34.67),但各化合物整体水平相当;在清除O-2·能力上化合物7a,7d,7g,7h最大清除率(分别为19.34,35.35,27.93和31.74)均强于同等浓度的Vc(17.58). 相似文献
4.
Recyclable and reusable Pd(OAc)2/PPh3/PEG‐2000 system for homocoupling reaction of arylboronic acids under air without base 下载免费PDF全文
A stable and efficient Pd(OAc)2/PPh3/PEG‐2000 catalytic system for homocoupling of arylboronic acids has been developed. In the presence of Pd(OAc)2 and PPh3, the homocoupling reaction of arylboronic acids was carried out smoothly in PEG‐2000 at 70 °C under air without base to afford a variety of symmetric biaryls in good to excellent yields. The isolation of the products was readily performed by extraction with diethyl ether, and the Pd(OAc)2/PPh3/PEG‐2000 system could be easily recycled and reused six times without significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Journal of Thermal Analysis and Calorimetry - A complete analysis of the thermal process about melamine was presented, in which different methods were applied to determine the characteristic of the... 相似文献
6.
Facile fabrication of fast recyclable and multiple self‐healing epoxy materials through diels‐alder adduct cross‐linker 下载免费PDF全文
Xiao Kuang Guoming Liu Xia Dong Xianggui Liu Jianjun Xu Dujin Wang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(18):2094-2103
A reversibly cross‐linked epoxy resin with efficient reprocessing and intrinsic self‐healing was prepared from a diamine Diels‐Alder (DA) adduct cross‐linker and a commercial epoxy oligomer. The newly synthesized diamine cross‐linker, comprising a DA adduct of furan and maleimide moieties, can cure epoxy monomer/oligomer with thermal reversibility. The reversible transition between cross‐linked state and linear architecture endows the cured epoxy with rapid recyclability and repeated healability. The reversibly cross‐linked epoxy fundamentally behaves as typical thermosets at ambient conditions yet can be fast reprocessed at elevated temperature like thermoplastics. As a potential reversible adhesive, the epoxy polymer with adhesive strength values about 3 MPa showed full recovery after repeated fracture‐thermal healing processes. The methodology explored in this contribution provides new insights in modification of conventional engineering plastics as functional materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2094–2103 相似文献
7.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献
8.
Supposa that f(x) is a quasidifferentiable function, defined on S(?)R~n where S is an open set, with a -equivalent bounded quasidifferential subfam ily. Lenma I 相似文献
9.
10.
与HBV X蛋白相互作用的细胞蛋白的筛选及其鉴定 总被引:1,自引:1,他引:0
参考GenBank核苷酸序列库中的HBV的核苷酸序列设计合成了一对对应于HBx基因的引物,从原发性肝癌(hepatocellular carcinoma,HCC)患者的血清中提取HBV基因组DNA作为模板,扩增HBx编码区并测定了核苷酸序列.将该编码区克隆到酵母双杂交系统的诱饵蛋白表达载体pGBKT7中,转入酵母细胞AH109,进行表型鉴定.然后通过Mating实验从已制备好用于酵母双杂交系统的肝cDNA表达文库中筛选与HBx相互作用的细胞蛋白,并用体外免疫共沉淀实验进一步验证.研究表明,分离得到的与HBx基因编码的蛋白相互作用的4种新的细胞蛋白,分别是醛缩酶B、C8α亚基、一种丝氨酸蛋白酶Hepsin和一种未知蛋白. 相似文献