全文获取类型
收费全文 | 498718篇 |
免费 | 54339篇 |
国内免费 | 208篇 |
专业分类
553265篇 |
出版年
2018年 | 5142篇 |
2017年 | 4781篇 |
2016年 | 7084篇 |
2015年 | 10000篇 |
2014年 | 11572篇 |
2013年 | 15350篇 |
2012年 | 18317篇 |
2011年 | 18701篇 |
2010年 | 12682篇 |
2009年 | 11691篇 |
2008年 | 16726篇 |
2007年 | 17296篇 |
2006年 | 16298篇 |
2005年 | 15638篇 |
2004年 | 15574篇 |
2003年 | 14685篇 |
2002年 | 14269篇 |
2001年 | 18159篇 |
2000年 | 17978篇 |
1999年 | 14759篇 |
1998年 | 6101篇 |
1997年 | 5994篇 |
1996年 | 5557篇 |
1995年 | 5163篇 |
1994年 | 5031篇 |
1993年 | 5113篇 |
1992年 | 12099篇 |
1991年 | 11994篇 |
1990年 | 11709篇 |
1989年 | 11264篇 |
1988年 | 10869篇 |
1987年 | 10377篇 |
1986年 | 9638篇 |
1985年 | 9588篇 |
1984年 | 8215篇 |
1983年 | 7066篇 |
1982年 | 5604篇 |
1981年 | 5055篇 |
1980年 | 4827篇 |
1979年 | 7697篇 |
1978年 | 6148篇 |
1977年 | 5652篇 |
1976年 | 5432篇 |
1975年 | 5784篇 |
1974年 | 6515篇 |
1973年 | 6302篇 |
1972年 | 5865篇 |
1971年 | 5320篇 |
1970年 | 4709篇 |
1969年 | 4643篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
E. Golomer P. Dupui H. Monod 《European journal of applied physiology and occupational physiology》1997,76(2):140-144
We investigated the effects of maturation on the dynamic body sways of healthy girls. Prepubertal and postpubertal girls
practising professional physical activities requiring a good ability to maintain equilibrium (acrobats and dancers) were asked
to stand on a free seesaw platform and the results compared to those for untrained age-matched girls. This platform (stabilometer)
allows self-induced body sways. Stabilograms were obtained by a double integration of the angular acceleration from the recordings
of the platform sways made with an accelerometer. Fast Fourier transform processing of stabilograms allowed spectral frequency
analysis. The total spectrum energy and the energies of three frequency bands (0–0.5 Hz, 0.5–2 Hz, 2–20 Hz) were determined.
ANOVA showed that, for all groups of different equilibrium activity and independent of visual input, prepubertal girls had
higher energy values than postpubertal girls in the 0- to 0.5-Hz band whereas the opposite was true for 0.5- to 2-Hz band.
Ballet dancers were more dependent than acrobats on visual inputs for the regulation of their postural control but were less
dependent than untrained girls at both ages. Maturation seemed to shift body sways towards higher frequencies and the utilization
of the cues of postural control was different according to the type of equilibrium activity practised by the subjects.
Accepted: 7 February 1997 相似文献
972.
973.
N Brinkmann M Malissard M Ramuz U R?mer T Schumacher E G Berger L Elling C Wandrey A Liese 《Bioorganic & medicinal chemistry letters》2001,11(18):2503-2506
The alpha-Gal trisaccharide Gal(alpha)(1-->3)Galbeta(1-->4)GlcNAc 11 was synthesized on a homogeneously soluble polymeric support (polyethylene glycol, PEG) by use of a multi-enzyme system consisting of beta-1,4-galactosyltransferase (EC 2.4.1.38), alpha-1,3-galactosyltransferase (EC 2.4.1.151), sucrose synthase (EC 2.4.1.13) and UDP-glucose-4-epimerase (EC 5.1.3.2). In addition workup was simplified by use of dia-ultrafiltration. Thus the advantages of classic chemistry/enzymology and solid-phase synthesis could be united in one. Subsequent hydrogenolytic cleavage afforded the free alpha-Gal trisaccharide. 相似文献
974.
Biosorption is becoming an important component in the integrated approach to the treatment of aqueous effluents. The economics of biomass technical applications are improved by using waste biomass instead of purposely-produced biomass. Biomass derived from an alginate extraction industry - Sargassum sp. - was examined for its ability to function as a biosorbent for metals such as cadmium, zinc and copper. For use in column applications, biomass should be immobilized. To the algae reinforcement, the biomass was embedded in polyethleneimine (PEI), followed by glutaraldehyde crosslinking. Equilibrium Zn and Cu isotherms were analysed using the immobilization ratio that showed the best Cd performance. Either Freundlich or Langmuir models can describe the passive biosorption equilibrium of cadmium, zinc and cooper. The preference for this series of metals by the biomass was found to be Cd > Zn > Cu, with maximum uptake values of 157.8, 118.5 and 77.4 mg/g dry weight biomass for Cd, Zn and Cu. respectively. The metal binding capacity by non-living biomass is an important quality for industrial use. 相似文献
975.
976.
977.
978.
E Arin? A Aydo?mu? 《Comparative biochemistry and physiology. B, Comparative biochemistry》1990,97(3):455-460
1. Formation of catechols from benzene and nitrobenzene have been implicated in the carcinogenic activity of these chemicals. In liver, p-nitrophenol, an intermediate of p-nitrobenzene is enzymatically converted to 4-nitrocatechol. 2. For the first time in this study, the presence of a highly active enzyme catalyzing the formation of 4-nitrocatechol from p-nitrophenol was detected in lung microsomes. The average specific activity of lung p-nitrophenol hydroxylase was found to be 0.494 nmol 4-nitrocatechol formed mg prot-1 min-1. 3. The optimum conditions for sheep lung microsomal p-nitrophenol hydroxylase were established. The maximal activity was noted at pH 6.8. The rate of p-nitrophenol hydroxylation was linear up to 2 mg prot/ml of incubation mixture. The maximal rate of 4-nitrocatechol formation was observed with 0.25 mM p-nitrophenol. 4. The Lineweaver-Burk and Eadie-Hofstee plots were found to be curve-linear. Two different Km values were calculated as 11.6 and 71.4 microM from the Lineweaver-Burk plot and as 10.7 and 74.5 microM from the Eadie-Hofstee plot. This suggested that there were either two forms of enzyme or two different enzymes participating in ortho hydroxylation of p-nitrophenol in lung microsomes. 5. Lung microsomal p-nitrophenol hydroxylase activity of sheep was reconstituted in the presence of purified lung microsomal cytochrome P-450, NADPH dependent cytochrome P-450 reductase and synthetic lipid, phosphatidylcholine dilauroyl. 相似文献
979.
980.
Joseph Bucukovski Neus Latorre-Margalef David E. Stallknecht Benjamin L. Miller 《PloS one》2015,10(8)
Influenza serology has traditionally relied on techniques such as hemagglutination inhibition, microneutralization, and ELISA. These assays are complex, challenging to implement in a format allowing detection of several types of antibody-analyte interactions at once (multiplex), and troublesome to implement in the field. As an alternative, we have developed a hemagglutinin microarray on the Arrayed Imaging Reflectometry (AIR) platform. AIR provides sensitive, rapid, and label-free multiplex detection of targets in complex analyte samples such as serum. In preliminary work, we demonstrated the application of this array to the testing of human samples from a vaccine trial. Here, we report the application of an expanded label-free hemagglutinin microarray to the analysis of avian serum samples. Samples from influenza virus challenge experiments in mallards yielded strong, selective detection of antibodies to the challenge antigen in most cases. Samples acquired in the field from mallards were also analyzed, and compared with viral hemagglutinin inhibition and microneutralization assays. We find that the AIR hemagglutinin microarray can provide a simple and robust alternative to standard methods, offering substantially greater information density from a simple workflow. 相似文献