全文获取类型
收费全文 | 13758篇 |
免费 | 376篇 |
国内免费 | 101篇 |
专业分类
化学 | 9673篇 |
晶体学 | 134篇 |
力学 | 315篇 |
数学 | 1904篇 |
物理学 | 2209篇 |
出版年
2023年 | 72篇 |
2022年 | 106篇 |
2021年 | 140篇 |
2020年 | 178篇 |
2019年 | 180篇 |
2018年 | 143篇 |
2017年 | 124篇 |
2016年 | 255篇 |
2015年 | 272篇 |
2014年 | 314篇 |
2013年 | 599篇 |
2012年 | 740篇 |
2011年 | 949篇 |
2010年 | 471篇 |
2009年 | 387篇 |
2008年 | 836篇 |
2007年 | 852篇 |
2006年 | 907篇 |
2005年 | 942篇 |
2004年 | 806篇 |
2003年 | 680篇 |
2002年 | 633篇 |
2001年 | 198篇 |
2000年 | 180篇 |
1999年 | 152篇 |
1998年 | 168篇 |
1997年 | 198篇 |
1996年 | 214篇 |
1995年 | 141篇 |
1994年 | 146篇 |
1993年 | 146篇 |
1992年 | 127篇 |
1991年 | 115篇 |
1990年 | 82篇 |
1989年 | 87篇 |
1988年 | 88篇 |
1987年 | 80篇 |
1986年 | 70篇 |
1985年 | 134篇 |
1984年 | 125篇 |
1983年 | 97篇 |
1982年 | 103篇 |
1981年 | 115篇 |
1980年 | 118篇 |
1979年 | 86篇 |
1978年 | 85篇 |
1977年 | 70篇 |
1975年 | 67篇 |
1974年 | 70篇 |
1973年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Malkinson JP Anim MK Zloh M Searcey M Hampshire AJ Fox KR 《The Journal of organic chemistry》2005,70(19):7654-7661
[reaction: see text] In this article, the first solid-phase-based total synthesis of TANDEM, a synthetic analogue of triostin A, is described. In initial studies, the synthesis incorporated depsipeptide formation, introduction of chromophores, and disulfide bond formation on the solid phase, prior to a final solution-phase macrolactamization, to give the target molecule. Although pure TANDEM was obtained in an overall yield comparable to those for all syntheses to date, the yield of the final cyclization was low (11%). A more efficient approach involved removal from the solid phase prior to disulfide bond formation. The resulting linear peptide underwent macrolactamization under mild conditions and high dilution. Final disulfide bond formation was essentially quantitative and gave the target molecule, TANDEM, in an overall yield of 18%. The final compound was assessed for its ability to bind to 5'-TpA sequences on DNA by DNase I footprinting. This efficient synthesis sets the stage for a study of the structure-activity relationship of TANDEM and the natural product triostin A, with analogues containing "point mutations" at every site within the cyclic compounds. 相似文献
92.
Woodward C. A. Macinnis J. M. Lewis S. N. Greenbaum E. 《Applied biochemistry and biotechnology》1992,34(1):819-826
Applied Biochemistry and Biotechnology - Normal photosynthesis byCyanidium results in O2 evolution, suggesting that the uptake and subsequent reduction of CO2 also occur. This process, therefore,... 相似文献
93.
Alan D. Potoff Bertrand L. Chamberland Lewis Katz 《Journal of solid state chemistry》1973,8(3):234-237
A single crystal study of hydrothermally prepared eight-layer BaMnO3 has been carried out which confirms the (Zhdanov notation) 121121 layer stacking scheme for the BaO3 layers. The MnO6 octahedra share faces in strings of four, and these strings are connected to each other by corner sharing. The compound has an hexagonal unit cell of dimensions a = 5.667 ± 0.003 and c = 18.738 ± 0.009 Å, probable space group . Its structure has been determined from 352 independent reflections, of which 242 were considered observed, collected manually by a counter technique and refined to a conventional R value of 0.079. 相似文献
94.
95.
Applied Biochemistry and Biotechnology - 相似文献
96.
Applied Biochemistry and Biotechnology - 相似文献
97.
Twenty years of gibberellin research 总被引:4,自引:0,他引:4
Mander LN 《Natural product reports》2003,20(1):49-69
This review covers research into the chemistry and biology of the gibberellin family of plant bioregulators carried out in the author's laboratory over the past 20 years and has 231 references. 相似文献
98.
99.
Yan B Collins N Wheatley J Irving M Leopold K Chan C Shornikov A Fang L Lee A Stock M Zhao J 《Journal of combinatorial chemistry》2004,6(2):255-261
We have developed a high-throughput purification system to purify combinatorial libraries at a 50-100-mg scale with a throughput of 250 samples/instrument/day. We applied an accelerated retention window method to shorten the purification time and targeted one fraction per injection to simplify data tracking, lower QC workload, and simplify the postpurification processing. First, we determined the accurate retention time and peak height for all compounds using an eight-channel parallel LC/UV/MS system, and calculated the specific preparative HPLC conditions for individual compounds. The preparative HPLC conditions include the compound-specific gradient segment for individual compounds with a fixed gradient slope and the compound-specific UV or ELSD threshold for triggering a fraction collection device. A unique solvent composition or solvent strength was programmed for each compound in the preparative HPLC in order to elute all compounds at the same target time. Considering the possible deviation of the predicted retention time, a 1-min window around the target time was set to collect peaks above a threshold based on UV or ELSD detection. Dual column preparative instruments were used to maximize throughput. We have purified more than 500 000 druglike compounds using this system in the past 3 years. We report various components of this high-throughput purification system and some of our purification results. 相似文献
100.
Dendritic molecular capsules for hydrophobic compounds 总被引:1,自引:0,他引:1
Morgan MT Carnahan MA Immoos CE Ribeiro AA Finkelstein S Lee SJ Grinstaff MW 《Journal of the American Chemical Society》2003,125(50):15485-15489
Reichardt's dye, a highly solvatochromic dye, was encapsulated within poly (glycerol succinic acid) ([Gn]-PGLSA-OH) dendrimers to investigate the interior environment of these dendritic macromolecules. The absorption maximum for the encapsulated Reichardt's dye in water was indicative of a relatively high dielectric constant present within the dye/dendrimer complex. (1)H NMR of the encapsulated complex showed the presence of aromatic protons from Reichardt's dye along with the aliphatic protons of the dendrimer. Additionally, there were substantial changes in T(1) and T(2) times of the encapsulated dye when compared with the free dye, and (1)H NOESY spectra for the complex showed a significant number of intermolecular NOE cross-peaks. These data reveal the close through-space proximity of the dye to the dendrimer and the restricted motion of the encapsulated dye. To demonstrate the potential use of these macromolecules as drug delivery vehicles, the poorly water-soluble anticancer drug 10-hydroxycamptothecin (10HCPT) was encapsulated within a carboxylated PGLSA dendrimer ([G4]-PGLSA-COONa). Cytotoxicity assays with human breast cancer cells showed a significant reduction of cell viability, demonstrating that 10HCPT retains activity upon encapsulation. 相似文献