全文获取类型
收费全文 | 5055篇 |
免费 | 809篇 |
国内免费 | 577篇 |
专业分类
化学 | 3500篇 |
晶体学 | 46篇 |
力学 | 355篇 |
综合类 | 25篇 |
数学 | 627篇 |
物理学 | 1888篇 |
出版年
2024年 | 26篇 |
2023年 | 107篇 |
2022年 | 170篇 |
2021年 | 206篇 |
2020年 | 204篇 |
2019年 | 195篇 |
2018年 | 189篇 |
2017年 | 139篇 |
2016年 | 278篇 |
2015年 | 238篇 |
2014年 | 266篇 |
2013年 | 394篇 |
2012年 | 492篇 |
2011年 | 466篇 |
2010年 | 317篇 |
2009年 | 300篇 |
2008年 | 318篇 |
2007年 | 252篇 |
2006年 | 249篇 |
2005年 | 211篇 |
2004年 | 189篇 |
2003年 | 162篇 |
2002年 | 133篇 |
2001年 | 113篇 |
2000年 | 95篇 |
1999年 | 110篇 |
1998年 | 75篇 |
1997年 | 75篇 |
1996年 | 77篇 |
1995年 | 63篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 27篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 26篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1974年 | 2篇 |
1944年 | 4篇 |
1943年 | 1篇 |
1942年 | 3篇 |
1941年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有6441条查询结果,搜索用时 0 毫秒
971.
Chunxu Bai 《Physics letters. A》2008,372(5):725-729
Spin-polarized transports of relativistic electrons through graphene-based ferromagnet/insulator/ferromagnet (FG/IG/FG) single junctions have been investigated theoretically. Large oscillating tunnel magnetoresistance (TMR) has been found in monolayer and bilayer FG/IG/FG junctions. The oscillating amplitudes of TMR do not decrease with the increase of the thickness and the height of barrier, in contrast to the exponential decay in conventional ferromagnet/insulator/ferromagnet single junction. The physical origin for such a phenomenon has also been analyzed. It is anticipated to apply such a phenomenon to design the spin-polarized electron device based on the graphene materials. 相似文献
972.
Kang Tao Dairen Lu Ruke Bai Hongfei Li Lijia An 《Macromolecular rapid communications》2008,29(17):1477-1483
We have developed a novel strategy for the preparation of ion‐bonded supramolecular star polymers by RAFT polymerization. An ion‐bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert‐butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by 1H NMR and GPC. The results show that the polymerization possesses the character of living free‐radical polymerization and the ion‐bonded supramolecular star polymers PSt, PtBA, and PSt‐b‐PtBA, with six well‐defined arms, were successfully synthesized.
973.
高分辨电感耦合等离子体质谱可以区分干扰元素和目标元素微弱的质量数差别,能解决大多数多原子、氧化物干扰问题,在煤炭痕量元素分析领域受到关注,但煤炭样品中痕量金属元素尤其是稀土元素受到的质谱干扰挑战未被系统地报道.采用HNO3-HF混酸微波消解煤炭样品,优化了消解时间、赶酸、复溶等前处理条件,研究了煤炭中V、Cr、Mn、C... 相似文献
974.
975.
Pingping Li Jian Sun Xiaohe Xu Zhisheng Mi Yuyan Lin Jingya Cheng Renren Bai Yuanyuan Xie 《Tetrahedron letters》2018,59(27):2640-2643
A ferric nitrate-promoted cross-dehydrogenative coupling reaction of N-hydroxyphthalimide (NHPI) with toluene derivatives is reported. The reaction proceeded smoothly using molecular oxygen as an oxidant, providing an efficient method for the synthesis of N-hydroxyimide esters. Furthermore, a plausible mechanism was proposed. 相似文献
976.
Shengqiang?LiEmail author Xu?Liu Shuchao?Pang Ruojun?Lu Yonghua?Liu MeiHong?Fan Zhijie?Jia Hongxue?Bai 《Mikrochimica acta》2018,185(9):433
An electrochemical biosensor for determination of DNA is described that is based on the reaction of regulated DNA (reg-DNA) first with substrated DNA (subs-DNA) to form a reaction intermediate. The intermediate binds target DNA (T) by hybridization and initiates a branch migration leading to the production of complex of substrated DNA and target DNA (TC). Once TC is produced, it reacts with assisted DNA (ass-DNA) through a toehold exchange mechanism, yielding the product complex of substrated DNA and assisted DNA (CS). The target is then released back into the solution and and catalyzes the next cycle of toehold-exchange with the reaction intermediate of substrated DNA and regulated DNA (CPR). Unlike in a conventional DNA toehold that is hardwired with the branch migration domain, the allosteric DNA toehold is designed into a reg-DNA which is independent of the branch migration domain. Under the optimal experimental conditions and at a working potential as low as 0.18 V, response to DNA is linear in the 1 fM to 1000 pM concentration range, and the detection limit is 0.83 fM. The assay is highly specific and can discriminate target DNA even from a single-base mismatch. It was applied to the analysis of DNA spiked plasma samples. 相似文献
977.
An efficient, novel and convenient method for the synthesis of modified polyacrylonitrile (PAN) with antibacterial property is reported. The modification of PAN was prepared by a nitrile click chemistry reaction with sodium azide (NaN3) and silver nitrate (AgNO3) as catalyst to yield antibacterial polymeric materials with 5-vinyltetrazole units. The results showed that 5-vinyltetrazole units had coordinated with silver ion (Ag+). Through the electrostatic spinning technology, the post-modification PAN nanofibers (PAN–Ag+ nanofibers) were prepared and the fibers were tested for their antimicrobial properties by the bacterial infection experiment. Afterwards, the antibacterial and stable performance of different proportions of silver ions in PAN nanofibers has been compared. The PAN–Ag+ nanofibers are characterized for mechanical and thermomechanical properties, structural analysis, appearance characteristics, as well as the antibacterial properties. And the nanofibers exhibit marvelous chemical stability according to the thermogravimetric analysis. When at 800 °C, the PAN decomposed about 60%, while the decomposition of the PAN–Ag+s was 40%. Based on the bacterial infection experiment, PAN–Ag+ nanofibers’ antibacterial properties were stronger with the increase of silver ions, such as the number of bacteria clone was smaller and the bacteriostatic ring was larger. Hence, with combination of silver ions, the final polymers show strong antimicrobial properties. 相似文献
978.
Inside Cover: Peripheral Templation‐Modulated Interconversion between an A4L6 Tetrahedral Anion Cage and A2L3 Triple Helicate with Guest Capture/Release (Angew. Chem. Int. Ed. 7/2018) 下载免费PDF全文
979.
One three-dimensional Sr(II) coordination polymer [C6(MIm)2][Sr3(1,4-NDC)4] (I) (C6(MIm)2 = 1,3-bis(3-methylimidazolium-1-yl)hexyl, 1,4-H2NDC = 1,4-naphthalenedicarboxylate acid) has been synthesized using an ionothermal method and structurally characterized by IR spectroscopy, UV-Vis spectroscopy, XRPD, and X-ray single-crystal structure analysis (СIF file CCDC 1033958). Two types of strontium centers are bridged by two coordination modes of 1,4-H2NDC ligands to form a Sr(II) chain. Each Sr(II) chain is crossconnected to four other chains to generate a 3D coordination polymer, in which C6(MIm) 2 2+ cations as charge balancing species are filled in the channels of the anionic framework. The polymeric solid of I exhibits strong luminescent emission at room temperature. 相似文献