全文获取类型
收费全文 | 1433篇 |
免费 | 66篇 |
国内免费 | 11篇 |
专业分类
化学 | 862篇 |
晶体学 | 22篇 |
力学 | 36篇 |
数学 | 180篇 |
物理学 | 410篇 |
出版年
2021年 | 10篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 31篇 |
2015年 | 37篇 |
2014年 | 39篇 |
2013年 | 72篇 |
2012年 | 57篇 |
2011年 | 83篇 |
2010年 | 45篇 |
2009年 | 35篇 |
2008年 | 73篇 |
2007年 | 68篇 |
2006年 | 69篇 |
2005年 | 77篇 |
2004年 | 60篇 |
2003年 | 49篇 |
2002年 | 49篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 18篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 28篇 |
1984年 | 21篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1975年 | 12篇 |
1974年 | 10篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1969年 | 8篇 |
排序方式: 共有1510条查询结果,搜索用时 156 毫秒
11.
Kochocki JA Allison WW Alner GJ Ambats I Ayres DS Balka LJ Barr GD Barrett WL Benjamin D Border P Brooks CB Cobb JH Cockerill DJ Coover K Courant H Dahlin B DasGupta U Dawson JW Edwards VW Fields TH Kirby-Gallagher LM Garcia-Garcia C Giles RH Goodman MC Heller K Heppelman S Hill N Hoftiezer JH Jankowski DJ Johns K Joyce T Kafka T Litchfield PJ Lopez FV Lowe M Mann WA Marshak ML May EN McMaster L Milburn RH Miller W Napier A Oliver WP Pearce GF Perkins DH Peterson EA Price LE Roback D Rosen DB 《Physical review D: Particles and fields》1990,42(9):2967-2973
12.
John R. Peterson Tamara J. Winter Hoang D. Do Robin D. Rogers 《Journal of chemical crystallography》1989,19(1):135-145
Structural and conformational information obtained from the crystal structure and solution1H nmr investigations of the title compound are compared. The 4-aryltetralone, C24H24O10, crystallizes as a chloroform solvate in the monoclinic space group, P21/n, witha=12.519(4),b=17.938(6),c=12.534(9)Å,=111.90(5)°, and Dcalc=1.51 g cm–3 forZ=4. The data for this compound were collected at –150°C. Least-squares refinement of 2796 observed [F
o5(F
o)] reflections led to the final agreement index ofR=0.062. A threefold static disorder was observed for one of the carboxyl groups. The second carboxyl group participates in an intramolecular hydrogen bond and is thus ordered. The1H nmr spectrum revealed the title compound to exist as a keto-enol tautomeric mixture in solution. Vicinal hydrogen coupling constant analysis proved reliable in ascertaining B-ring stereochemistry of 2,3-disubstituted-4-aryltetralones. 相似文献
13.
14.
15.
Bortoletto D Goldberg M Horwitz N Mestayer MD Moneti GC Sharma V Shipsey IP Skwarnicki T Csorna SE Letson T Brock IC Ferguson T Artuso M Bebek C Berkelman K Blucher E Byrd J Cassel DG Cheu E Coffman DM Crawford G DeSalvo R DeWire JW Drell PS Ehrlich R Galik RS Gittelman B Gray SW Halling AM Hartill DL Heltsley BK Kandaswamy J Kowalewski R Kreinick DL Kubota Y Lewis JD Mistry NB Mueller J Namjoshi R Nandi S Nordberg E O'Grady C Peterson D Pisharody M Riley D Sapper M Silverman A Stone S Worden H 《Physical review letters》1989,62(21):2436-2439
16.
Alam MS Katayama N Kim IJ Li WC Lou XC Sun CR Bortoletto D Goldberg M Horwitz N Mestayer MD Moneti GC Sharma V Shipsey IP Skwarnicki T Csorna SE Letson T Brock IC Ferguson T Artuso M Bebek C Berkelman K Blucher E Byrd J Cassel DG Cheu E Coffman DM Crawford G DeSalvo R DeWire JW Drell PS Ehrlich R Galik RS Gittelman B Gray SW Halling AM Hartill DL Heltsley BK Kandaswamy J Kowalewski R Kreinick DL Kubota Y Lewis JD Mistry NB Mueller J Namjoshi R Nandi S Nordberg E O'Grady C Peterson D Pisharody M 《Physical review D: Particles and fields》1989,40(11):3790
17.
E. R. Peterson 《Research on Chemical Intermediates》1994,20(1):93-96
The chemical industry admits to minimal use of microwave power because of its high capital and operating costs relative to
steam, combustion, electrical, and other traditional sources of energy. Other valid historical and persistent reasons for
their lack of proper use include: a poor conceptual understanding of microwaves by chemical professionals, their unwillingness
to replace existing adequate methods with radically new technology, the infancy of the microwave industrial power supply,
and unfamiliarity of microwave power systems manufacturers with the chemical industry. In years past, the North American chemical
industry had few competitors and profits were generally large. Environmental regulations were few and product quality was
less a concern than production volume. The microwave power industry relied on the government and communications for lucrative
sales. Those days appear over.
Chemical manufacturers must probe every technology to achieve the edge necessary to stay competitive while meeting environmental
stewardship demands. Microwave power has always offered unique advantages in heating materials selectively and/or quickly
to high or preselected temperatures with fast control response. In the cases discussed in this paper, novel applications of
microwave power afford: faster production, a reduction in product contaminants, reduced downtime, reduced waste, product quality
improvements, and better pollution control. 相似文献
18.
G. Meissner Kari Hartonen M.-L. Riekkola 《Fresenius' Journal of Analytical Chemistry》1998,360(5):618-621
A method is developed for the determination of β-blockers in serum and urine at levels of 0.5 μg/mL. The technique uses a
combination of solid phase extraction (SPE) with in situ derivatization and supercritical fluid extraction (SFE) with subsequent
gas chromatography mass spectrometry. The optimization of the SFE step shows that a static extraction period can be eliminated.
The method gives good linearity (r = 0.991–0.999) and repeatability in the concentration range of 0.5 to 5 μg/mL. Relative
standard deviations for oxprenolol, propanolol and metoprolol were less than 5% in serum and 5–11% in urine.
Received: 23 May 1997 / Revised: 28 July 1997 / Accepted: 5 August 1997 相似文献
19.
Solid supports for micro analytical systems 总被引:2,自引:0,他引:2
Peterson DS 《Lab on a chip》2005,5(2):132-139
The development of micro analytical systems requires that fluids are able to interact with the surface of the microfluidic chip in order to perform analysis such as chromatography, solid phase extraction, and enzymatic digestion. These types of analyses are more efficient if there are solid supports within the microfluidic channels. In addition, solid supports within microfluidic chips are useful in producing devices with multiple functionalities. In recent years there have been many approaches introduced for incorporating solid supports within chips. This review will explore several state of the art methods and applications of introducing solid supports into chips. These include packing chips with beads, incorporating membranes into chips, creating supports using microfabrication, and fabricating gels and polymer monoliths within microfluidic channels. 相似文献
20.
The Leishmania lipophosphoglycan (LPG) is the most abundant cell surface glycoconjugate of a family of infectious protozoa. Pentamidine, a common drug used in the treatment of Leishmania infections, has been modified with boronic acids so that it might bind more selectively to the phosphodisaccharide repeating unit of the LPG. This could serve to target the drug to the protozoan surface and increase its efficacy in vivo. 相似文献