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21.
The impact of salinity on CH4 emission was studied by adding salt to a Philippine rice paddy, increasing pore water EC to approx. 4 dS.m-1 Methane emission from the salt-amended plot and adjacent control plots was monitored with a closed chamber technique. The
addition of salt to the rice field caused a reduction by 25% in CH4 emission. Rates of methane emissions from intact soil cores were measured during aerobic and anaerobic incubations. The anaerobic
CH4 fluxes from the salt-amended soil cores were three to four times lower than from cores of the control plot, whereas the aerobic
CH4 fluxes were about equal. Measurements of the potential CH4 production with depth showed that the CH4 production in the salt-amended field was strongly reduced compared to the control field. Calculation of the percentage CH4 oxidized of the anaerobic flux indicated that CH4 oxidation in the salt-amended plot was even more inhibited than CH4 production. The net result was about equal aerobic CH4 fluxes from both salt-amended plots and non-amended plots. The data illustrate the importance of both CH4 production and CH4 oxidation when estimating CH4 emission and show that the ratio between CH4 production and CH4 oxidation may depend on environmental conditions. The reduction in CH4 emission from rice paddies upon amendment with salt low in sulfate is considerably smaller than the reduction in CH4 emission observed in a similar study where fields were amended with high-sulfate containing salt (gypsum). The results indicate
that CH4 emissions from wetland rice fields on saline, low-sulfate soils are lower than CH4 emissions from otherwise comparable non-saline rice tields. However, the reduction in CH4 emission is not proportional to the reduction in CH4 production 相似文献
22.
D. B. Morton P. J. Simpson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(6):417-427
Previous studies have shown that the neuropeptide, eclosion hormone, stimulates a nitric oxide-independent increase in the levels of cGMP in the nervous system of Manduca sexta. By contrast, recent results in Bombyx mori suggest that eclosion hormone increases cGMP via the production of nitric oxide. In view of these conflicting results we have carried out additional studies to test whether nitric oxide is involved in this process in Manduca. Evidence presented here supports our earlier observations that in Manduca the eclosion hormone-stimulated increase in cGMP is nitric oxide-and carbon monoxide-independent. In addition, we show that a wide variety of inhibitors of lipid metabolism block the eclosion hormone-stimulated cGMP increase. This supports the hypothesis that the activation of the guanylate cyclase is mediated by a lipid messenger. We also show that eclosion hormone stimulates an increase in the levels of inositol(1,4,5)trisphosphate. The time-course of this increase is consistent with the hypothesis that eclosion hormone stimulation of a phospholipase C is an early event in the cascade that results in an increase in cGMP. Receptor-mediated lipid hydrolysis is often mediated by G protein-coupled receptors. Experiments using pertussis toxin show that the eclosion hormone-stimulated increase in cGMP is not mediated by a pertussis toxin-sensitive G protein.Abbreviations
AACOCF
3
arachidonyl trifluoromethyl ketone
-
4-BPB
4-bromophenacyl bromide
- cGMP
guanosine 3,5 cyclic monophosphate
-
D609
tricyclodecan-9-yl-xanthogenate
-
DEDA
7,7 dimethyleicosadienoic acid
-
DAG
diacylglycerol
-
EH
eclosion hormone
-
ET-18-OCH
3
1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine
-
ETYA
5,8,11,14-eicosatetraynoic acid
-
InsP
3
inositol(1,4,5)trisphosphate
-
LO
lipoxygenase
-
Lyso-PA
lysophosphatidic acid
-
HPLC
highpressure liquid chromatography
-
NDGA
nordihydroguaiaretic acid
-
NOS
nitric oxide synthase
-
OEPC
oleoxyethyl phosphorylylcholine
-
ONO-RS-082
2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid
-
oxo-M
oxotremorine-M
-
PAF
platelet-activating factor
-
PKC
protein kinase C
-
PLA
2
phospholipase A2
-
PLC
phospholipase C
-
PLD
phospholipase D
-
PPH
phosphatidate phosphohydrolase
-
PtdIns(4,5)P
2
phosphatidylinositol bisphosphate
-
PTX
pertussis toxin
-
TEA
triethylamine
-
TFA
trifluoroacetic acid
-
U-73122
1-(6-((17-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione 相似文献
23.
Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of CO2, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those based on CO2 pore-water gradients using Fick's First law indicates that apparent diffusion coefficients are 2 to 28 times higher than bulk sediment diffusion coefficients based on molecular diffusion. Seasonal changes in gaseous carbon fluxes or CO2 pore water concentrations cannot be used directly, or in a simple way, to determine seasonal rates of mineralization, because of marked seasonal changes in pore-water storage and exchange parameters.The annual amount of carbon delivered to the sediment is 42 mol m–2, of which about 42% becomes buried, the remaining being emitted as methane (7%) or carbon dioxide (50%). Each year about 2.6 mol N m–2 of particulate nitrogen reaches the sediment; 1.1 mol m–2 is buried and 1.6 mol m–2 is mineralized to ammonium. Only 0.42 mol m–2 yr–1 of the ammonium produced escapes from the sediments, the remaining being first nitrified (1.2 mol m–2 yr–1) and then denitrified (1.7 mol m–2 yr–1). Simple calculations indicate that intertidal sediments may account for about 14% and 30% of the total estuarine retention of nitrogen and carbon, respectively. 相似文献
24.
Crystal structure of the hydroxylase component of methane monooxygenase from Methylosinus trichosporium OB3b. 总被引:1,自引:0,他引:1
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N. Elango R. Radhakrishnan W. A. Froland B. J. Wallar C. A. Earhart J. D. Lipscomb D. H. Ohlendorf 《Protein science : a publication of the Protein Society》1997,6(3):556-568
Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the O2-dependent conversion of methane to methanol. The soluble form of the enzyme (sMMO) consists of three components: a reductase, a regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which contains a hydroxo-bridged dinuclear iron cluster. Two genera of methanotrophs, termed Type X and Type II, which differ markedly in cellular and metabolic characteristics, are known to produce the sMMO. The structure of MMOH from the Type X methanotroph Methylococcus capsulatus Bath (MMO Bath) has been reported recently. Two different structures were found for the essential diiron cluster, depending upon the temperature at which the diffraction data were collected. In order to extend the structural studies to the Type II methanotrophs and to determine whether one of the two known MMOH structures is generally applicable to the MMOH family, we have determined the crystal structure of the MMOH from Type II Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A resolution, respectively, both determined at 18 degrees C. The crystal forms differ in that MMOB was present during crystallization of the second form. Both crystal forms, however, yielded very similar results for the structure of the MMOH. Most of the major structural features of the MMOH Bath were also maintained with high fidelity. The two irons of the active site cluster of MMOH OB3b are bridged by two OH (or one OH and one H2O), as well as both carboxylate oxygens of Glu alpha 144. This bis-mu-hydroxo-bridged "diamond core" structure, with a short Fe-Fe distance of 2.99 A, is unique for the resting state of proteins containing analogous diiron clusters, and is very similar to the structure reported for the cluster from flash frozen (-160 degrees C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid sequence differences in the beta chain when compared to the previously reported sequence inferred from the cloned gene. Fifteen additional sequence differences distributed randomly over the three chains were also observed, including D alpha 209E, a ligand of one of the irons. 相似文献
25.
Methane monooxygenase mutants of Methylosinus trichosporium constructed by marker-exchange mutagenesis 总被引:1,自引:0,他引:1
Abstract Methylosinus trichosporium OB3b synthesizes a soluble cytoplasmic methane monooxygenase when grown in copper-depleted medium and a membrane-bound particulate methane monooxygenase under copper-replete conditions. The genes encoding the hydroxylase component of soluble methane monooxygenase, carried on a plasmid in Escherichia coli , were insertionally inactivated using a kanamycin cassette and transferred back into M. trichosporium by conjugation. Marker-exchange mutagenesis, via a double homologous recombination event, yielded a soluble methane monooxygenase-negative mutant which grew only on methane using the particulate methane monooxygenase during copper-replete growth conditions, thus proving that the two methane oxidation systems in this methanotroph are genetically distinct. 相似文献
26.
庭园生态经济系统设计及应用 总被引:5,自引:0,他引:5
庭园生态经济系统设计及应用刘东飙邓立平(湖南省益阳市农村能源办公室413000)(湖南省南县农村能源办公室413200)DesigningOfHomeGardenEcolomicSystemwithMethaneGeneratingasaTieand... 相似文献
27.
The composition of volatile fatty acids in the biogas digester based on cattle manure as substrate and stabilised at 25°C
showed that it contained 87–88% branched chain fatty acids, comprising of isobutyric and isovaleric acids, in comparison to
38 % observed in the digester operating at 35°C.
Mixed cellulolytic cultures equilibrated at 25°C (C-25) and 35‡C (C-35) showed similar properties, but rates of hydrolysis
were three times higher than that observed in a standard biogas digester. The proportion of isobutyric and isovaleric were
drastically reduced when C-25 was grown with glucose or filter paper as substrates. The volatile fatty acids recovered from
C-25 (at 25°C) inhibited growth of methanogens on acetate, whereas that from C-35 was not inhibitory. The inhibitory effects
were due to the branched chain fatty acids and were observed with isobutyric acid at concentrations as low as 50 ppm.
Addition of another micro-organismRhodotorula selected for growth on isobutyric completely reversed this inhibition. Results indicate that the aceticlastic methanogens
are very sensitive to inhibition by branched chain fatty acids and reduction in methane formation in biogas digester at lower
temperature may be due to this effect. 相似文献
28.
A major improvement in the purification of the oxygenase protein (component A) of the methane monooxygenase has been effected. By employing high-pressure gel permeation chromatography several purification steps may be omitted from the previously published scheme. Furthermore the yield of the protein is enhanced and more importantly the recovered protein displays an increased specific activity, unlike that purified by other techniques. 相似文献
29.
Abstract In Methanothrix soehngenii acetate is first activated by an acetate thiokinase rather than a phosphotransacetylase. The specific activity of the acetate thiokinase was 5.29 μmol acetate activated min−1 mg−1 protein with a half maximum rate at 0.74 mM acetate and at 0.047 mM CoA. In cell-free extracts a CO-dehydrogenase activity was measured of 3.02 μmol min−1 mg−1 protein with a half maximum rate at 0.44 mM CO and at 0.18 mM methylviologen. NADP and NAD could not replace methylviologen. F420 showed only low activity as electron acceptor. 相似文献
30.
Kazuo Okamura Kazuyasu Kisaichi Ken-ichiro Takamiya Mitsuo Nishimura 《Archives of microbiology》1984,139(2-3):143-146
A soluble cytochrome, cytochrome c-551 was purified from an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942) by ammonium sulfate fractionation, ion-exchange chromatography and gel-filtration. The cytochrome had absorption maxima at 277, 410, and 524–525 nm in the oxidized form, and at 415, 522, and 550.5 nm in the reduced form. At 77 K, the -band of the absorption spectrum of the reduced form split in two at 547 and 549 nm. The millimolar absorption coefficient at 550.5 nm was 26.8 mM-1 cm-1 in the reduced form. This cytochrome was an acidic protein with an isoelectric point of 4.9. Its molecular weight was determined to be 15,000 by gel-filtration on Sephadex G-100 and 14,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The midpoint potential of this cytochrome was +250 mV at pH 7.0. This cytochrome did not bind CO. 相似文献