全文获取类型
收费全文 | 405篇 |
免费 | 37篇 |
出版年
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 18篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1967年 | 6篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1919年 | 3篇 |
排序方式: 共有442条查询结果,搜索用时 78 毫秒
81.
The dynamics of ubiquitin pools within the cultured human lung fibroblast line IMR-90 were examined using solid phase immunochemical methods to quantitate free and conjugated polypeptide. Fetal calf serum was found to contain a nondialyzable factor that induced a transient accumulation of ubiquitin. During the induction, free and conjugated ubiquitin pools changed in concert so that the fraction conjugated remained constant. The induction of ubiquitin by the serum factor resulted from an enhanced rate of protein synthesis. Within experimental error no change in the first order rate constant for intracellular ubiquitin degradation was observed. Pulse-chase studies revealed ubiquitin to turn over with a half-life of 28-31 h in conditioned and freshly fed cultures. Withdrawal of serum from cultures led to a rapid decline in total ubiquitin during which the fractional level of conjugation remained constant. The accelerated ubiquitin turnover following removal of serum likely involves lysosomal autophagy since 10 mM NH4Cl led to an accumulation of the polypeptide. Since no similar effect of the lysosomotropic compound was observed in conditioned or freshly fed cultures, nonlysosomal processes are probably responsible for ubiquitin turnover under nutritional balance. The dynamics of these intracellular pools suggests that the ubiquitin ligation system is subject to regulatory constraints not previously suspected. The short half-life for ubiquitin is consistent with the apparent ability of cells to alter ubiquitin levels in response to external stimuli and stress. 相似文献
82.
83.
Collaborating with recreational fishers to inform fisheries management: Estimating population abundance for an iconic freshwater crayfish
下载免费PDF全文
![点击此处可从《Ecological Management & Restoration》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sylvia Zukowski Martin Asmus Nick Whiterod Anthony Conallin Josh Campbell Ian Fisher Troy Bright 《Ecological Management & Restoration》2018,19(1):85-88
Can the abundance of fish populations be effectively determined by the collection of scientific research with support from recreational fishers? Collecting and analysing fishing data from recreational fishers to aid management are not new; however, engaging fishers in a scientific survey design to produce specific population estimates is rarely undertaken. We engaged recreational fishers to assist with field sampling to provide an estimate Murray Crayfish (Euastacus armatus von Martens, 1866) abundance at three sites on the Edward River which were recently impacted by an extreme blackwater disturbance. Employing mark‐resight models, fishers undertook crayfish surveys and produced research data which estimated adult population sizes of Murray Crayfish in the studied reaches ranging between 94.27 ± 24.72 individuals (Below Stevens) and 450.01 ± 175.30 individuals (Twin Rivers). Both the effective undertaking of the mark‐resight designs in collaboration with fishers and acquiring population abundance estimates for Murray Crayfish in a river reach are concepts which have not previously been published and are important attributes for the management of aquatic species. 相似文献
84.
Bright Varghese Mushira Enani Abdulrahman Alrajhi Sameera Al Johani Ali Albarak Sahar Althawadi Noura Elkhizzi Hawra AlGhafli Mohammed Shoukri Sahal Al - Hajoj 《Respiratory research》2018,19(1):259
Background
Growing evidences suggested that the Mycobacterium tuberculosis complex (MTBC) lineages can determine the clinical outcome of pulmonary and extra-pulmonary tuberculosis. However, limited data only available revealing such association of bacterial genotypes and clinical phenotypes from immigrant rich countries.Methods
A multicenter study has been carried out on a collection of 2092 (1003 extrapulmonary and 1089 pulmonary) MTBC isolates. Genotyping of all the isolates were carried out by spoligotyping and 24 loci based MIRU-VNTR typing.Results
Demographically domination of young Saudi nationals (61.4%) and men (61.2%) were found in this cohort. Lymph nodes (62.4%) and gastrointestinal sites (16.7%) were the most common anatomical sites of infection. The predominant lineages were Delhi/CAS (26.9%), EAI (14.2%) and Ghana (9.9%). Mycobacterium africanum type I and II were reported for the first time in the country among extrapulmonary cases. ‘Ancestral’ lineages M.bovis (OR-5.22; 95% CI-2.23-8.22, p-?<?0.001) and Delhi/CAS (OR-0.57; 95% CI-0.411-0.734, p-?<?0.001) were directly associated with lymph node tuberculosis and gastrointestinal tuberculosis (M. bovis-OR-0.33; 95% CI-0.085-0.567, p-0.001 and Delhi/CAS-OR-1.87; 95% CI-1.22-2.53, p-?<?0.001) respectively. Among the ‘Modern’ lineages, EAI showed significant association to central nervous system tuberculosis (OR-1.98; 95% CI-0.76-3.19, p-0.04) and Uganda-I to gastrointestinal tuberculosis (OR-2.41; 95% CI-0.77-4.06, p-0.02).Conclusions
The findings substantially contribute to the emerging evidences that MTBC lineages influence disease phenotypes and epidemiological consequences.85.
David C. Holt Venetia J. Lay Eric D. Clarke Andrew Dinsmore Ian Jepson Simon W. J. Bright Andrew J. Greenland 《Planta》1995,196(2):295-302
The safener-induced maize (Zea mays L.) glutathione S-transferase, GST II (EC 2.5.1.18) and another predominant isoform, GST I, were purified from extracts of maize roots treated with the safeners R-25788 (N,N-diallyl-2-dichloroacetamide) or R-29148 (3-dichloroace-tyl-2,2,5-trimethyl-1,3-oxazolidone). The isoforms GST I and GST II are respectively a homodimer of 29-kDa (GST-29) subunits and a heterodimer of 29 and 27-kDa (GST-27) subunits, while GST I is twice as active with 1-chloro-2,4-dinitrobenzene as GST II, GST II is about seven times more active against the herbicide, alachlor. Western blotting using antisera raised against GST-29 and GST-27 showed that GST-29 is present throughout the maize plant prior to safener treatment. In contrast, GST-27 is only present in roots of untreated plants but is induced in all the major aerial organs of maize after root-drenching with safener. The amino-acid sequences of proteolytic fragments of GST-27 show that it is related to GST-29 and identical to the 27-kDa subunit of GST IV.Abbreviations CDNB
1-chloro-2,4-dinitrobenzene
- DEAE
di-ethylaminoethyl
- FPLC
fast protein liquid chromatography
- GSH
reduced glutathione
- GST
glutathione S-transferase
- GST-26
26-kDa subunit of maize GST
- GST-27
27-kDa subunit of maize GST
- GST-29
29-kDa subunit of maize GST
- R-25788
safener N,N-diallyl-2-dichloroacetamide
- R-29148
safener 3-dichloroacetyl-2,2,5-trimethyl-1,3-oxazolidone
- RPLC
reverse phase liquid chromatography
We are grateful to M-M. Lay, ZENECA AG Products (formerly ICI Americas), Richmond, Calif., USA for providing [14C] R-25788. ZENECA Seeds in the UK is part of ZENECA Limited. 相似文献
86.
Patterns of survivorship and growth of rescued boulder corals from two vessel groundings in Biscayne National Park, Homestead, Florida, U.S.A., were evaluated over 5 years and compared to nearby undamaged reference corals. The rescued colonies had been dislodged but reattached in situ 10–12 years later (hereafter termed “restored” corals). Change in live coral tissue area was assessed using novel contoured tissue measurements which proved useful in detecting small changes in tissue area for slow‐growing coral species. At the initial survey, restored boulder corals had a higher level of partial mortality (33.8 ± 3.1%, mean ± SE) relative to reference corals (19.9 ± 2.5%), likely a result of prolonged detachment. During the course of the 5‐year monitoring period, whole‐colony mortality was greater for restored corals (13.1%) compared to reference corals (3.3%). For surviving corals, restored coral growth and recent mortality rates were similar to reference corals even though restored corals, especially those of Dichocoenia stokesii, had greater disease prevalence (19.7%) than reference corals (6.6%). These results suggest that dislodged boulder coral rescue following an acute disturbance can be an effective tool in stemming tissue loss. If dislodged corals were reattached in a more timely manner, we predict that the survival and tissue growth would be greater. 相似文献
87.
Solar Cells: Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells (Adv. Energy Mater. 19/2016)
下载免费PDF全文
![点击此处可从《Liver Transplantation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
88.
Julia Klose Karin Aistleitner Matthias Horn Liselotte Krenn Verena Dirsch Martin Zehl Monika Bright 《PloS one》2016,11(1)
The giant tubeworm Riftia pachyptila lives in symbiosis with the chemoautotrophic gammaproteobacterium Cand. Endoriftia persephone. Symbionts are released back into the environment upon host death in high-pressure experiments, while microbial fouling is not involved in trophosome degradation. Therefore, we examined the antimicrobial effect of the tubeworm’s trophosome and skin. The growth of all four tested Gram-positive, but only of one of the tested Gram-negative bacterial strains was inhibited by freshly fixed and degrading trophosome (incubated up to ten days at either warm or cold temperature), while no effect on Saccharomyces cerevisiae was observed. The skin did not show antimicrobial effects. A liquid chromatography-mass spectrometric analysis of the ethanol supernatant of fixed trophosomes lead to the tentative identification of the phospholipids 1-palmitoleyl-2-lyso-phosphatidylethanolamine, 2-palmitoleyl-1-lyso-phosphatidylethanolamine and the free fatty acids palmitoleic, palmitic and oleic acid, which are known to have an antimicrobial effect. As a result of tissue autolysis, the abundance of the free fatty acids increased with longer incubation time of trophosome samples. This correlated with an increasing growth inhibition of Bacillus subtilis and Listeria welshimeri, but not of the other bacterial strains. Therefore, the free fatty acids produced upon host degradation could be the cause of inhibition of at least these two bacterial strains. 相似文献
89.
Barbara J. Steven Dennis W. Kirk Simon W.J. Bright John L. Wray 《Molecular & general genetics : MGG》1989,219(3):421-428
Summary Three plants, R9201 and R11301 (from cv. Maris Mink) and R12202 (from cv. Golden Promise), were selected by screening M2 populations of barley (Hordeum vulgare L.) seedlings (mutagenised with azide in the M1) for resistance to 10 mM potassium chlorate. Selections R9201 and R11301 were crossed with the wild-type cv. Maris Mink and analysis of the F2 progeny showed that one quarter lacked shoot nitrate reductase activity. These F2 plants also withered and died in the continuous presence of nitrate as sole nitrogen source. Loss of nitrate reductase activity and withering and death were due in each case to a recessive mutation in a single nuclear gene. All F1 progeny derived from selfing selection R12202 lacked shoot nitrate reductase activity and also withered and subsequently died when maintained in the continuous presence of nitrate as sole nitrogen source. All homozygous mutant plants lacked not only shoot nitrate reductase activity but also shoot xanthine dehydrogenase activity. The plants took up nitrate, and possessed wild-type or higher levels of shoot nitrite reductase activity and NADH-cytochrome c reductase activity when treated with nitrate for 18 h. We conclude that loss of shoot nitrate reductase activity, xanthine dehydrogenase activity and withering and death, in the three mutants R9201, R11301 and R12202 is due to a mutation affecting the formation of a functional molybdenum cofactor. The mutants possessed wild-type levels of molybdenum and growth in the presence of unphysiologically high levels of molybdate did not restore shoot nitrate reductase or xanthine dehydrogenase activity. The shoot molybdenum cofactor of R9201 and of R12202 is unable to reconstitute NADPH nitrate reductase activity from extracts of the Neurospora crassa nit-1 mutant and dimerise the nitrate reductase subunits present in the respective barley mutant. The shoot molybdenum cofactor of R11301 is able to effect dimerisation of the R11301 nitrate reductase subunits and can reconstitute NADPH-nitrate reductase activity up to 40% of the wild-type molybdenum cofactor levels. The molybdenum cofactor of the roots of R9201 and R11301 is also defective. Genetic analysis demonstrated that R9201, but not R11301, is allelic to R9401 and Az34 (nar-2a), two mutants previously shown to be defective in synthesis of molybdenum cofactor. The mutations in R9401 and R9201 gave partial complementation of the nar-2a gene such that heterozygotes had higher levels of extractable nitrate reductase activity than the homozygous mutants.We conclude that: (a) the nar-2 gene locus encodes a step in molybdopterin biosynthesis; (b) the mutant R11301 represents a further locus involved in the synthesis of a functional molybdenum cofactor; (c) mutant Rl2202 is also defective in molybdopterin biosynthesis; and (d) the nar-2 gene locus and the gene locus defined by R11301 govern molybdenum cofactor biosynthesis in both shoot and root. 相似文献
90.