全文获取类型
收费全文 | 8176篇 |
免费 | 435篇 |
国内免费 | 76篇 |
专业分类
化学 | 5954篇 |
晶体学 | 59篇 |
力学 | 147篇 |
数学 | 860篇 |
物理学 | 1667篇 |
出版年
2023年 | 38篇 |
2022年 | 103篇 |
2021年 | 169篇 |
2020年 | 141篇 |
2019年 | 153篇 |
2018年 | 130篇 |
2017年 | 125篇 |
2016年 | 285篇 |
2015年 | 246篇 |
2014年 | 296篇 |
2013年 | 518篇 |
2012年 | 581篇 |
2011年 | 666篇 |
2010年 | 398篇 |
2009年 | 319篇 |
2008年 | 533篇 |
2007年 | 475篇 |
2006年 | 473篇 |
2005年 | 424篇 |
2004年 | 383篇 |
2003年 | 327篇 |
2002年 | 290篇 |
2001年 | 145篇 |
2000年 | 142篇 |
1999年 | 101篇 |
1998年 | 78篇 |
1997年 | 75篇 |
1996年 | 80篇 |
1995年 | 64篇 |
1994年 | 65篇 |
1993年 | 62篇 |
1992年 | 50篇 |
1991年 | 31篇 |
1990年 | 50篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 49篇 |
1984年 | 34篇 |
1983年 | 29篇 |
1982年 | 31篇 |
1981年 | 33篇 |
1980年 | 26篇 |
1979年 | 33篇 |
1978年 | 22篇 |
1977年 | 25篇 |
1976年 | 25篇 |
1975年 | 22篇 |
1973年 | 29篇 |
排序方式: 共有8687条查询结果,搜索用时 62 毫秒
991.
Choi SH Hwang IS Lee JH Oh SG Kim ID 《Chemical communications (Cambridge, England)》2011,47(33):9315-9317
Microstructural evolution of spinel Zn(2)SnO(4) nanofibers was manipulated via an in situ phase separation process of inorganic precursors and a matrix polymer during electrospinning and calcination. Chemiresistive gas sensors using porous Zn(2)SnO(4) fibers exhibited superior C(2)H(5)OH sensing response. 相似文献
992.
Jiang S Kim MG Kim SJ Jung HS Lee SW Noh do Y Sadowsky MJ Hur HG 《Chemical communications (Cambridge, England)》2011,47(28):8076-8078
Shewanella oneidensis MR-1 rapidly accumulates long, extracellular, U(VI) nanowires composed of polycrystalline chains of discrete meta-schoepite (UO(3)·2H(2)O) nanocrystallites. The production of uranium(VI) nanowires could provide a novel strategy for remediation of uranium contamination in sediments and aquifers, as well as the recovery of uranium in manufacturing processes. 相似文献
993.
Kim YS Bae SY Kim KH Lee TW Hur JA Hoang MH Cho MJ Kim SJ Kim Y Kim M Lee K Lee SJ Choi DH 《Chemical communications (Cambridge, England)》2011,47(31):8907-8909
A new pyrene-cored π-conjugated molecule has been synthesized through Sonogashira coupling reaction. The single-crystalline microribbon-based FET exhibited the highest mobility of 0.7 cm(2) V(-1) s(-1) (I(on)/I(off) > 10(6)). Single-crystalline microribbons were employed to operate in an organic phototransistor (OPT) under very low light intensity (I = 5.6 μW cm(-2)). 相似文献
994.
DNA-mediated gold nanoparticles were prepared by chemical reduction of DNA-Au(III) complex. The DNA-Au(III) was first formed by reacting DNA with HAuCl? at a pH of 5.6. The complex in solution was reacted with hydrazine reducing Au(III) to Au. The reduced Au formed nanodimensional aggregates. The particle distributions were obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This method resulted in a rather uniform dispersion of Au nanoparticles of near-spherical shape and 45~80 nm in diameter. Gold nanoparticles were embedded and stabilized by DNA. 相似文献
995.
Antioxidant and antityrosinase activities of various extracts from the fruiting bodies of Lentinus lepideus 总被引:1,自引:0,他引:1
Yoon KN Alam N Lee KR Shin PG Cheong JC Yoo YB Lee TS 《Molecules (Basel, Switzerland)》2011,16(3):2334-2347
Lentinus lepideus is an edible mushroom currently available in Korea. The acetone, methanol and hot water extracts were prepared and assayed for their antioxidant and antityrosinase inhibitory activities. The hot water extract showed the strongest β-carotene-linoleic acid inhibition compared to the other extracts. At 8 mg/mL, the methanolic extract showed a high reducing power of 1.21. The acetone and methanol extracts were more effective in scavenging DPPH radicals than the hot water extract. The strongest chelating effect was obtained from the methanolic extract. Xanthine oxidase and tyrosinase inhibitory activities of the acetonic, methanol and hot water extracts increased with increasing concentration. Gallic acid, chlorogenic acid, vanillin, naringin, naringenin, formononetin, and biochanin-A were detected in the acetonitrile and hydrochloric acid (5:1) solvent extract. This study suggests that fruiting bodies of L. lepideus can potentially be used as a readily accessible source of natural antioxidants. 相似文献
996.
Myristicin (1-allyl-5-methoxy-3,4-methylenedioxybenzene) is an active aromatic compound found in nutmeg (the seed of Myristica fragrans), carrot, basil,cinnamon, and parsley. Myristicin has been known to have anti-cholinergic, antibacterial,and hepatoprotective effects, however, the effects of myristicin on virus-stimulated macrophages are not fully reported. In this study, the anti-inflammatory effect of myristicin on double-stranded RNA (dsRNA)-stimulated macrophages was examined. Myristicin did not reduce the cell viability of RAW 264.7 mouse macrophages at concentrations of up to 50 μM. Myristicin significantly inhibited the production of calcium, nitric oxide (NO),interleukin (IL)-6, IL-10, interferon inducible protein-10, monocyte chemotactic protein(MCP)-1, MCP-3, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein (MIP)-1α, MIP-1β, and leukemia inhibitory factor in dsRNA[polyinosinic-polycytidylic acid]-induced RAW 264.7 cells (P < 0.05). In conclusion,myristicin has anti-inflammatory properties related with its inhibition of NO, cytokines,chemokines, and growth factors in dsRNA-stimulated macrophages via the calcium pathway. 相似文献
997.
A simple and efficient seven steps synthesis of brodifacoum and difethialone from phenylacetyl chloride is described. The key synthetic strategies involve Friedel-Crafts acylation, intramolecular ring cyclization and condensation reaction in the presence of Br?nsted-Lowry acids. It was found that brodifacoum showed favorable inhibiting activities on LPS-stimulated nitrite production in BV-2 microglia cells. Brodifacoum exhibited superior anti-inflammatory effects than difethialone. We expect that an efficient linear synthesis of 4-hydroxycoumarin derivatives and key fragments that are useful agents for the modulation of inflammation as well as inhibition of coagulation will be of practical use. 相似文献
998.
999.
1000.