全文获取类型
收费全文 | 4023篇 |
免费 | 536篇 |
国内免费 | 878篇 |
专业分类
化学 | 3089篇 |
晶体学 | 85篇 |
力学 | 228篇 |
综合类 | 107篇 |
数学 | 547篇 |
物理学 | 1381篇 |
出版年
2024年 | 5篇 |
2023年 | 27篇 |
2022年 | 99篇 |
2021年 | 123篇 |
2020年 | 117篇 |
2019年 | 142篇 |
2018年 | 114篇 |
2017年 | 136篇 |
2016年 | 163篇 |
2015年 | 187篇 |
2014年 | 212篇 |
2013年 | 314篇 |
2012年 | 265篇 |
2011年 | 299篇 |
2010年 | 218篇 |
2009年 | 279篇 |
2008年 | 294篇 |
2007年 | 288篇 |
2006年 | 252篇 |
2005年 | 225篇 |
2004年 | 223篇 |
2003年 | 203篇 |
2002年 | 221篇 |
2001年 | 225篇 |
2000年 | 168篇 |
1999年 | 123篇 |
1998年 | 44篇 |
1997年 | 51篇 |
1996年 | 36篇 |
1995年 | 34篇 |
1994年 | 34篇 |
1993年 | 25篇 |
1992年 | 35篇 |
1991年 | 18篇 |
1990年 | 28篇 |
1989年 | 12篇 |
1988年 | 25篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 8篇 |
排序方式: 共有5437条查询结果,搜索用时 10 毫秒
81.
R. D. Sinisterra R. Najjar O. L. Alves P. S. Santos C. A. Alves De Carvalho A. L. Conde Da Silva 《Journal of inclusion phenomena and macrocyclic chemistry》1995,22(2):91-98
The preparation and characterization of the 1:1 inclusion compound of rhodium(II) -methyl cinnamate in -cyclodextrin is reported. Evidence of inclusion was obtained from X-ray powder diffraction results, Raman, IR and UV-Vis spectroscopic studies and thermal analysis. Given the potential antitumor activity of the rhodium(II) carboxylate and its virtual insolubility in water, its inclusion in -cyclodextrin opens the possibility for its transference to the aqueous phase. 相似文献
82.
J. C. Moreno J. Nilsen J. A. Koch B. J. MacGowan J. H. Scofield L. B. Da Silva 《Applied physics. B, Lasers and optics》1994,58(1):3-5
Neon-like niobium X-ray lasers have been studied using both slab and thin-foil target geometries. Niobium foils of various lengths were irradiated from both sides with two beams of the frequency-doubled Nova laser system using a line focus. We looked for gain by measuring spectrally integrated line intensities at different plasma lengths. Gain was observed in four neon-like niobium lines corresponding to 3s–3p transitions. The line profile of theJ = 0–1 line ( = 145.9 ) shows splitting due to the hyperfine effect. Improved contrast in the hyperfine structure is observed as the plasma length is increased. Hyperfine splitting may be relevant to other 3s–3p transitions in neon-like niobium as well as other neon-like X-ray laser systems. 相似文献
83.
Sílvia S. P. R. Almeida Joo J. R. Fraústo Da Silva Armando J. L. Pombeiro 《Journal of organometallic chemistry》1993,450(1-2)
Treatment of a THF solution of trans-[ReCl(N2)(dppe)2] (dppe = Ph2PCH2CH2PPh2) with a 1-alkyne HCCR (R =tBu, CO2Me, CO2Et, or C6H4Me-4), in the presence of Tl[BF4]/[NH4][BF4], under sunlight, affords the corresponding carbyne-fluoro complexes trans-[ReF(CCH2R)(dppe)2][BF4] in an unprecedented single-pot synthesis. Further reaction with [BU4N]OH leads to the vinylidenefluoro compounds trans-[ReF(=C=CHR)(dppe)2] (R = CO2Me, CO2Et, or C6H4Me-4). 相似文献
84.
Da Yeon Park 《Tetrahedron letters》2006,47(37):6641-6645
Polysubstituted benzene derivatives were synthesized starting from the Baylis-Hillman adducts via the sequential introduction of primary nitroalkane at the primary position, Michael addition to β-branched Michael acceptor, aldol condensation, elimination of nitrous acid, and the final aromatization process. 相似文献
85.
Seghezzo L Trupiano AP Liberal V Todd PG Figueroa ME Gutiérrez MA Da Silva Wilches AC Iribarnegaray M Guerra RG Arena A Cuevas CM Zeeman G Lettinga G 《Applied biochemistry and biotechnology》2003,109(1-3):167-180
A pilot-scale sewage treatment system consisting of two upflow anaerobic sludge bed (UASB) reactors followed by five waste stabilization ponds (WSPs) in series was studied under subtropical conditions. The first UASB reactor started up in only 1 mo (stable operation, high chemical oxygen demand [COD] removal efficiency, low volatile fatty acids concentration in the effluent, alkalinity ratio above 0.7, biogas production above 0.1 Nm3/kg of CODremoved). Removal efficiencies up to 90% were obtained in the anaerobic steps at a hydraulic retention time of 6 + 4 h (80% removal in the first step). Fecal coliform removal in the whole system was 99.9999% (99.94% in anaerobic steps and 99.98% in WSPs). COD balances over UASB reactors are provided. A minimum set of data necessary to build COD balances is proposed. Intermittent sludge washout was detected in the reactors with the COD balances. Sludge washout from single-step UASB reactors should be monitored and minimized in order to ensure constant compliance with discharge standards, especially when no posttreatment is provided. The system combined high COD and fecal coliform removal efficiency with an extremely low effluent concentration, complying with discharge standards, and making it an attractive option for sewage treatment in subtropical regions. 相似文献
86.
Determination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide 总被引:4,自引:0,他引:4
Mei HUANG Xian Da WANG Ren Tian XIONG Ping Dong WU Qi Long REN* National Laboratory of Secondary Resources Chemical Engineering Zhejiang University Hangzhou 《中国化学快报》2002,13(1)
The use of supercritical fluids (SCFs) as solvents has been attracting widespread interest in the research and commercial applications. The study of partial molar volumes of solutes at infinite dilution in the near-critical region is of considerable fundamental importance, as these data reflects the interactions occurring between the solute and the solvent. Experimental measurements of partial molar volumes may be divided into two categories: direct and indirect methods. The direct methods… 相似文献
87.
Monoclonal antibody technique was employed to detect the conformational difference of CaM induced by metal ions. A trivalent europium ion induced conformation-specific anti-calmodulin monoclonal antibody was successfully prepared with europium-saturated calmodulin as antigen. 相似文献
88.
89.
90.