全文获取类型
收费全文 | 1431篇 |
免费 | 95篇 |
出版年
2022年 | 12篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 24篇 |
2017年 | 33篇 |
2016年 | 40篇 |
2015年 | 45篇 |
2014年 | 44篇 |
2013年 | 73篇 |
2012年 | 65篇 |
2011年 | 71篇 |
2010年 | 55篇 |
2009年 | 33篇 |
2008年 | 56篇 |
2007年 | 76篇 |
2006年 | 86篇 |
2005年 | 46篇 |
2004年 | 52篇 |
2003年 | 41篇 |
2002年 | 45篇 |
2001年 | 45篇 |
2000年 | 53篇 |
1999年 | 40篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1995年 | 19篇 |
1993年 | 7篇 |
1992年 | 25篇 |
1991年 | 25篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 25篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 17篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 8篇 |
1971年 | 7篇 |
1969年 | 8篇 |
排序方式: 共有1526条查询结果,搜索用时 15 毫秒
851.
Pas J Wyszko E Rolle K Rychlewski L Nowak S Zukiel R Barciszewski J 《The international journal of biochemistry & cell biology》2006,38(9):1594-1602
Tenascin-C is a multidomain large extracellular matrix glycoprotein composed of six monomers. The size of tenascin-C monomers (180-250 kDa) varies as a result of an alternative splicing of the fibronectin repeats at the pre-mRNA level. For the first time we applied bioinformatic and molecular modeling procedures, for detailed analysis of the organization of tenascin-C and we performed bioinformatic analysis of tenascin-C gene. We detected the presence of heat shock protein 33 in the tenascin-C N-terminal domain that may suggest its role in the protein-protein interactions and stress response. The number of fibronectin type III-like repeats and epidermal growth factor-like repeats were corrected to 15 and 14, respectively. Using polyactylamide gel electophoresis, RT/PCR analysis and microarrays data, we showed the higher level of tenascin-C in the human tumor tissues: brain, intestine and breast. These results suggested a new role of tenascin-C as the potential tumor marker and drug target. 相似文献
852.
Nowak P Saluk-Juszczak J Olas B Kołodziejczyk J Wachowicz B 《Cellular & molecular biology letters》2006,11(1):1-11
Many selenoorganic compounds play an important role in biochemical processes and act as antioxidants, enzyme inhibitors or
drugs. The effects of a new selenocompound — bis(2-aminophenyl)-diselenide on oxidative/nitrative changes in human plasma
proteins induced by peroxynitrite (ONOO−) were studied in vitro and compared with the those of ebselen, a well-known antioxidant. We also studied the role of the tested selenocompounds
in peroxynitrite-induced plasma lipid peroxidation. Exposure of the plasma to peroxynitrite (0.1 mM) resulted in an increase
in the level of carbonyl groups and nitrotyrosine residues in plasma proteins (estimated using the ELISA method and Western
blot analysis). In the presence of different concentrations (0.025–0.1 mM) of the tested selenocompounds, 0.1 mM peroxynitrite
caused a distinct decrease in the level of carbonyl group formation and tyrosine nitration in plasma proteins. Moreover, these
selenocompounds also inhibited plasma lipid peroxidation induced by ONOO−1 (0.1 mM). The obtained results indicate that in vitro bis(2-aminophenyl)-diselenide and ebselen have very similar protective effects against peroxynitrite-induced oxidative/nitrative
damage to human plasma proteins and lipids. 相似文献
853.
Increases in Desert Shrub Productivity under Elevated Carbon Dioxide Vary with Water Availability 总被引:2,自引:1,他引:1
David C. Housman Elke Naumburg Travis E. Huxman Therese N. Charlet Robert S. Nowak Stanley D. Smith 《Ecosystems》2006,9(3):374-385
Productivity of aridland plants is predicted to increase substantially with rising atmospheric carbon dioxide (CO2) concentrations due to enhancement in plant water-use efficiency (WUE). However, to date, there are few detailed analyses
of how intact desert vegetation responds to elevated CO2. From 1998 to 2001, we examined aboveground production, photosynthesis, and water relations within three species exposed
to ambient (around 38 Pa) or elevated (55 Pa) CO2 concentrations at the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility in southern Nevada, USA. The functional types sampled—evergreen (Larrea tridentata), drought-deciduous (Ambrosia dumosa), and winter-deciduous shrubs (Krameria erecta)—represent potentially different responses to elevated CO2 in this ecosystem. We found elevated CO2 significantly increased aboveground production in all three species during an anomalously wet year (1998), with relative
production ratios (elevated:ambient CO2) ranging from 1.59 (Krameria) to 2.31 (Larrea). In three below-average rainfall years (1999–2001), growth was much reduced in all species, with only Ambrosia in 2001 having significantly higher production under elevated CO2. Integrated photosynthesis (mol CO2 m−2 y−1) in the three species was 1.26–2.03-fold higher under elevated CO2 in the wet year (1998) and 1.32–1.43-fold higher after the third year of reduced rainfall (2001). Instantaneous WUE was also
higher in shrubs grown under elevated CO2. The timing of peak canopy development did not change under elevated CO2; for example, there was no observed extension of leaf longevity into the dry season in the deciduous species. Similarly,
seasonal patterns in CO2 assimilation did not change, except for Larrea. Therefore, phenological and physiological patterns that characterize Mojave Desert perennials—early-season lags in canopy
development behind peak photosynthetic capacity, coupled with reductions in late-season photosynthetic capacity prior to reductions
in leaf area—were not significantly affected by elevated CO2. Together, these findings suggest that elevated CO2 can enhance the productivity of Mojave Desert shrubs, but this effect is most pronounced during years with abundant rainfall
when soil resources are most available. 相似文献
854.
Roel GW Verhaak Frank JT Staal Peter JM Valk Bob Lowenberg Marcel JT Reinders Dick de Ridder 《BMC bioinformatics》2006,7(1):105-15
Background
Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers. 相似文献855.
The identification of protozoan and metazoan parasites is traditionally carried out using a series of classical keys based upon the morphology of the whole organism. However, in stained tissue sections prepared for light microscopy, taxonomic features will be missing, thus making parasite identification difficult. This work highlights the characteristic features of representative parasites in tissue sections to aid identification. The parasite examples discussed are derived from species affecting finfish, and predominantly include parasites associated with disease or those commonly observed as incidental findings in disease diagnostic cases. Emphasis is on protozoan and small metazoan parasites (such as Myxosporidia) because these are the organisms most likely to be missed or mis-diagnosed during gross examination. Figures are presented in colour to assist biologists and veterinarians who are required to assess host/parasite interactions by light microscopy. 相似文献
856.
In vitro inoculation of Vitis vinifera L. cv. Chardonnay explants with a plant growth-promoting rhizobacterium, Burkholderia phytofirmans strain PsJN, increased grapevine growth and physiological activity at a low temperature. There was a relationship between endophytic bacterial colonization of the grapevine plantlets and their growth at both ambient (26 degrees C) and low (4 degrees C) temperatures and their sensitivities to chilling. The major benefits of bacterization were observed on root growth (11.8- and 10.7-fold increases at 26 degrees C and 4 degrees C, respectively) and plantlet biomass (6- and 2.2-fold increases at 26 degrees C and 4 degrees C, respectively). The inoculation with PsJN also significantly improved plantlet cold tolerance compared to that of the nonbacterized control. In nonchilled plantlets, bacterization enhanced CO(2) fixation and O(2) evolution 1.3 and 2.2 times, respectively. The nonbacterized controls were more sensitive to exposure to low temperatures than were the bacterized plantlets, as indicated by several measured parameters. Moreover, relative to the noninoculated controls, bacterized plantlets had significantly increased levels of starch, proline, and phenolics. These increases correlated with the enhancement of cold tolerance of the grapevine plantlets. In summary, B. phytofirmans strain PsJN inoculation stimulates grapevine growth and improves its ability to withstand cold stress. 相似文献
857.
858.
Włodzimierz Jędrzejewski Magdalena Niedzialkowska Robert W. Mysłajek Sabina Nowak Bogumiła Jędrzejewska 《Acta theriologica》2005,50(3):417-428
Using data from the National Wolf Census, carried out in Poland in 2000–2001, and GIS techniques we analysed habitat selection
by wolvesCanis lupus Linnaeus, 1758 in uplands and mountains of southern Poland. We compared ten habitat variables and two parameters related
to wolf abundance in 52 circular plots (154 km2 each) with recorded wolves and 97 randomly selected plots with no signs of wolf presence. Wolf plots were characterized by
higher elevation and closer location to the state border than wolf-free plots. Furthermore, wolf plots had higher forest cover,
but smaller number of villages and towns and shorter railways and roads than plots without wolves. The best model explaining
wolf distribution included forest cover, number of villages, length of roads and railway lines. Compared to northern Poland,
the southern part of the country offers worse habitats for wolves due to significantly denser network of settlements and transportation
routes. 相似文献
859.
The advantages of the analysis of electrical impedance changes for the prediction of the metabolic activity of mixed Bacillus cultures used for high temperature industrial wastewater utilization are demonstrated. The primary aim of this study was to investigate the possibilities of a fast assessment of the biodegradative capabilities of microorganisms, their requirements regarding the medium composition as well as the inhibiting effect of high‐strength (i.e., highly concentrated) wastewaters on microbial growth. Four mixed Bacillus cultures were cultivated at 45 and 55 °C on two kinds of wastewater from the potato starch industry. The course of changes in the electrical impedance during the cultivation of the bacteria in the examined wastewaters was described by the mathematical Gompertz model. Three kinetics parameters (maximum rate of impedance changes, Imax; the time necessary to reach, Imax, TI; and the duration of the lag phase, λ) were proposed for the statistical analysis of the bacterial metabolic activity. The temperature of the biodegradation process and the type and strength of the wastewater significantly influenced the microbial metabolic activity of the mixed bacterial cultures used. Monitoring of the impedance changes, caused by microbial metabolism, and its proposed mathematical specification allowed for predicting the dynamics of the microbiological degradation of wastewater and estimating the inhibiting effects of these media on the microorganisms. 相似文献
860.
Wójcik-Gładysz A Nowak KW Pierzchała-Koziec K Wańkowska M Misztal T Polkowska J Nowak M Kaczmarek P Górska T Szczepankiewicz D Zubel J 《Reproductive biology》2006,6(Z1):89-103
To increase our knowledge concerning the central and peripheral regulation of reproduction in mammals a series of studies were performed. In the first experiment, we found that exogenous leptin altered the activity of the hypothalmo-pituitary-gonadotropic axis in sheep during insufficient feeding. The action of leptin appears to be mediated by changes in GnRH and LH secretion as well as NPY immunoreactivity. The aim of the second experiment was to investigate the role of the adipoinsular axis hormones during pregnancy in rats. The elevated levels of plasma leptin as wells as the increased mRNAs expression of the leptin receptors in placenta indicate the significant role of the hormone in fetal growth and development. On the other hand, a decrease in leptin receptors mRNA content within hypothalamus and pituitary together with unchanged plasma insulin level may suggest that during rat pregnancy leptin resistance was developed in the hypothalamus, pituitary and pancreatic islets. The third experiment was carried out to establish the role of opioids and glucocorticoids in the regulation of the hypothalmo-pituitary-gonadal axis in ewes during natural or synchronized estrous cycle. Prolonged treatment with progesterone resulted in significant changes in plasma levels of Met-enkephalin, cortisol and steroids and altered the expression of proenkephalin mRNA in the hypothalamus, pituitary, ovary and adrenals. Injections of Met-enkephalin or naltrexone (blocker of opioid receptors) modulated the progesterone influence in tested tissues. The data clearly suggest that opioids are involved in the regulation of the estrous cycle at the hypothalamo-pituitary-gonadal/adrenal axes. 相似文献