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101.
Sediment pore water concentrations of Fe2+, Mn2+, NH
inf4
sup+
and CH4 were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station
with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4
mM m−2 day−1 (0.3 g m−2 day−1). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly
using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment
loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe2+ and CH4. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe2+ and Mn2+ to as high as 26% for NH
inf4
sup+
, and 30% for CH4. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this
station. 相似文献
102.
GASTON DUCET 《Physiologia plantarum》1980,50(3):241-250
Oxidation of succinate by potato tuber mitochondria has been investigated from aerobiosis to complete anuerobiosis. Difference spectra of the various steps were recorded by a rapid scan spectrometer delivering averaged spectra every 3 s in the range 380 to 630 mm. The transitions between state 3 and 4 resulted in large redox changes, essentially for the b cytochromes, and in significant changes in the spectral baseline (light scattering). At anaerobiosis the cytochromes c, c1 and a were reduced while cytochrome a, remained oxidized. – Addition of uncouplers in aerobiosis induced oxidation of the b cytochromes, and when anaerobiosis occurred cytochromes c, c1a and a3 were reduced simultaneously. When uncouplers were added in anaerobiosis a partial oxidation of the b cytochromes and the reduction of cytochrome a3 were observed. These results are interpreted as the building up of a membrane potential, maximal in state 4 and stable after anaerobiosis. The cytochromes buried in the membrane equilibrate with the membrane potential, and their redox states are sensitive to the changes. Variations of membrane potential also induce changes in the light scattering by the mitochondrial membrane. 相似文献
103.
Hubert G. D. Niekus Els van Doorn Adrian H. Stouthamer 《Archives of microbiology》1980,127(2):137-143
The kinetics of oxygen utilization by the microaerophile Campylobacter sputorum subspecies bubulus was studied. With formate as substrate two enzyme systems were found to be responsible for electron transfer between formate and oxygen. In the case of lactate oxidation one enzyme system could account for the activity measured. One of the formateoxidizing systems possessed a high affinity for oxygen [K
m(O2)=approx. 4M O2]. From inhibitor studies it was concluded that a respiratory chain was involved in its activity. Respiration by this system must be responsible for proton translocation and electron transport-linked phosphorylation at formate oxidation. The other enzyme system had an extremely low affinity for oxygen [K
m (O2)=approx. 1 mM O2]. It was tentatively identified as the H2O2-producing formate oxidase previously found in C. sputorum. The H2O2 production by this enzyme is implicated in an explanation of the microaerophilic nature of C. sputorum. Sensitivity of formate dehydrogenase to H2O2 was demonstrated. The influence of the formate concentration on aerobic formate oxidation was determined. The pH- and temperature dependencies of oxygen uptake with formate as substrate were examined at airsaturation and at a low dissolved oxygen tension.Abbreviations TL medium
tryptose-lactate medium
- TF medium
tryptose-formate medium
- HQNO
2-n-heptyl-4-hydroxyquinoline N-oxide
- SHAM
salicylhydroxamic acid
- DCPIP
2,6-dichlorophenolindophenol 相似文献
104.
Data are presented which were collected in the course of the past ten years and bear on the correlation of absorbance at 800 nm and the EPR signal at g = 2 (‘copper signal’) of cytochrome c oxidase in various states of oxidation and ligation. Both EPR and optical reflectance spectra were obtained at low temperature (?170 to ?190°C). For some sets of samples spectra were recorded in the range 500–1100 nm. A particular effort was made to study this correlation with what are called ‘mixed valence’ states (Greenwood, C., Wilson, M.T. and Brunori, M. (1974) Biochem. J. 137, 205–215), when cytochrome a and the EPR-detectable copper are thought to be oxidized and the other components reduced and vice versa. These data show no evidence that the copper component of cytochrome oxidase which has so far not been detected by EPR makes a contribution to the absorption between 800 and 900 nm exceeding 10–15% of the total, which is close to or within the error of the respective measurements. For the various states of the oxidase examined in this work the 700–800 nm region did not appear to be more useful than the 800–900 nm region for determining the state of the EPR-undetectable copper in a reliable way. These conclusions are in agreement with results presented previously from other laboratories concerning the relationship of optical (approx. 800 nm) and EPR spectroscopic (g = 2) data obtained with the enzyme. 相似文献
105.
D.J. Van Der Horst N.M.D. Houben A.M.Th. Beenakkers 《Journal of insect physiology》1980,26(7):441-448
In the two-fuel system for flight of the migratory locust, the haemolymph carbohydrate concentration falls during flight periods of up to 1 hr, the decrease being greater in case the pre-flight carbohydrate level is higher. The increase in the lipid concentration from the onset of flight is virtually independent of the initial lipid concentration. Flight intensity affects these changes in substrate concentrations: the carbohydrate level decreases more rapidly if flight speed is higher, whereas the increase in lipid concentration is delayed at higher flight speeds. Respiratory carbon dioxide production is elevated rapidly during flight and reaches over eight times the resting level. From the rate of 14CO2 production after labelling of the haemolymph diglyceride pool it is concluded that diglycerides contribute to providing the energy for flight from the earliest stage of flying activity; diglyceride oxidation increases until maximum utilization is attained after some 45 min of flight. The decline in haemolymph carbohydrate concentration due to flying activity results in a decrease of haemolymph osmolarity. Free amino acids, particularly taurine, increase markedly in the haemolymph during flight; yet their concentration only partially counterbalances the fall in haemolymph osmolarity. 相似文献
106.
107.
Takeo Yoshida 《Phytochemistry》1976,15(11):1723-1725
A new pyrazine derivative, stizolamine (1-methyl-3-guanidino-6-hydroxymethylpyrazin-2-one), has been isolated from seeds of Stizolobium hassjoo. This amine, which has a blue fluorescence, gives guanidine, N-methyl-alanine, oxalic acid, alanine and glycine on treatment with 6 N HCl. The permanganate oxidation product of stizolamine is 4-amino-6-methylcarbamoyl-1,3,5-triazine-2-carboxylic acid. 相似文献
108.
Bernard L. Powell Jerry W. Pickering Simon H. Wender Eddie C. Smith 《Phytochemistry》1975,14(8):1715-1717
Two anodic isoperoxidases (A1 and A2) from tobacco tissue culture W-38 and two cathodic isoperoxidases (C3 and C4) from tobacco suspension culture WR-132 have been separated and characterized. Molecular weights for each of the isoperoxidases have been determined by two different methods. Only C4 contained a carbohydrate component. The substrate specificity and the pH optima for the four enzymes with each of five substrates were determined. 相似文献
109.
110.
Noureddine Mazoir Ahmed Benharref Laura Vaca Matías Reina Azucena Gonzlez‐Coloma 《化学与生物多样性》2020,17(9)
Semisynthetic functionalized triterpenes (4α,14‐dimethyl‐5α,8α‐8,9‐epoxycholestan‐3β‐yl acetate; 4α,14‐dimethyl‐5α‐cholest‐8‐ene‐3,7,11‐trione; 4α,14‐dimethyl‐5α‐cholesta‐7,9(11)‐dien‐3‐one and 4α,14‐dimethyl‐5α‐cholest‐8‐en‐3β‐yl acetate), previously prepared from 31‐norlanostenol, a natural insecticide isolated from the latex of Euphorbia officinarum, have been subjected to oxidation with hydrogen peroxide (H2O2) and iodosobenzene (PhIO) catalyzed by porphyrin complexes (cytochrome P‐450 models) in order to obtain optimized derivatives with high regioselectivity. The main transformations were epoxidation of the double bonds and hydroxylations of non‐activated C–H groups and the reaction products were 25‐hydroxy‐4α,14‐dimethyl‐5α‐cholesta‐7,9(11)‐dien‐3β‐yl acetate (59 %), 25‐hydroxy‐4α,14‐dimethyl‐5α‐cholest‐8‐ene‐3,7,11‐trione (60 %), 4α,14‐dimethyl‐5α,7β‐7,8‐epoxycholest‐9(11)‐en‐3‐one (22 %), 8‐hydroxy‐4α,14‐dimethyl‐5α‐cholest‐9(11)‐ene‐3,7‐dione (16 %), 12α‐hydroxy‐4α,14‐dimethyl‐5α,7β‐7,8‐epoxycholest‐9(11)‐en‐3‐one (16 %), and 4α,14‐dimethyl‐5α,8α‐8,9‐epoxycholestan‐3β‐yl acetate (26 %), respectively. We also investigated the insect (Myzus persicae, Rhopalosiphum padi and Spodoptera littoralis) antifeedant and postingestive effects of these terpenoid derivatives. None of the compounds tested had significant antifeedant effects, however, all were more effective postingestive toxicants on S. littoralis larvae than the natural compound 31‐norlanostenol, with 4α,14‐dimethyl‐5α,8α‐8,9‐epoxycholestan‐3β‐yl acetate being the most active. The study of their structure–activity relationships points out at the importance of C3 and C7 substituents. 相似文献