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11.
Chlorinated methanes are important environmental pollutants, which can be metabolized by bacteria. The biotransformation of chlorinated methanes by bacteria has been shown to be due either to gratuitous metabolism (cometabolism) or their use as a source of carbon and energy. The reactions which result in carbon-halogen bond cleavage include substitutive, reductive, oxygenative, and gem-elimination mechanisms. Certain methylotrophic bacteria can use dichloromethane as a source of carbon and energy. Dichloromethane dehalogenase catalyzes the first substitutive reaction in this metabolism. The enzyme shows a 1010-fold rate enhancement over the reaction of the bisulfide anion with dichloromethane in water. Pseudomonas putida G786 synthesizes cytochrome P-450CAM which catalyzes the gratuitous reduction of chlorinated methanes. These studies with purified enzymes are beginning to reveal more detailed mechanistic features of bacterial chlorinated methane metabolism.Abbreviations DNA
deoxyribonucleic acid
- kcat
catalytic first order rate constant for an enzyme catalyzed reaction
- KM
Michaelis constant for an enzyme catalyzed reaction
- MNDO
modified neglect of diatomic overlap
- PIMA
pattern induced multialignment
- DCMD
dichloromethane dehalogenase 相似文献
12.
The immunocytochemical demonstration of Toxoplasma antigen in the brains of congenitally infected mice 总被引:1,自引:0,他引:1
J Hay D I Graham G N Dutton S Logan 《Zeitschrift für Parasitenkunde (Berlin, Germany)》1986,72(5):609-615
The peroxidase anti-peroxidase immunocytochemical staining method was used to identify Toxoplasma antigen in paraffin embedded sections of the brains of 22 mice congenitally infected with the parasite. Intact Toxoplasma tissue cysts were readily demonstrated in the brain in all cases. In 4 of the 22 infected mice there was evidence of rupture of the cyst wall and/or presence of extra-cystic Toxoplasma antigen. Further support for the extra-cystic location of Toxoplasma antigen was obtained by electron microscopy of reprocessed tissue which revealed endozoites in the area immediately surrounding a ruptured cyst. The possible implications of these findings in relation to the pathogenesis of congenital toxoplasmic meningo-encephalitis are discussed. 相似文献
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Four kits for the detection of serum transaminase based on the spectrophotometric method and 15 kits based on the colorimetric procedure were evaluated. Two kits contained faulty reagents in both the SGOT and SGPT packages. Four of the 15 kits gave results which differed significantly from those of the reference method. The precision of the various kit procedures was adequate in each case for the determinations of SGOT and SGPT. The need to evaluate the adequacy of each kit in a routine operation before relying upon the results obtained with it is stressed. 相似文献
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Direct observation of phytoplankton, TEP and aggregates on polycarbonate filters using brightfield microscopy 总被引:1,自引:0,他引:1
Logan Bruce E.; Grossart Hans-Peter; Simon Meinhard 《Journal of plankton research》1994,16(12):1811-1815
There has been little use of standard (i.e. non-inverted) microscopesfor observing and counting phytoplankton in filtered water samplesusing brightfield white light illumination due to light interferencefrom the filters. If filters are placed on newly designed frostedslides (Cyto-clear, Poretics Corp.), however, phytoplanktoncan be viewed directly on the surfaces of polycarbonate filtersunder brightfield illumination. Lake and seawater samples wereused to show that samples stained with alcian blue (to identifythe presence of paniculate polysaccharides) and analyzed withwhite light can also be simultaneously stained with fluorochromes(i.e. DAPI and acridine orange) for additional examination ofthe sample using fluorescent techniques. Black filters, whichare necessary for epifluorescent techniques, did not interferewith brightfield viewing. Using double staining techniques,we found that transparent exopolymer particles (TEP) recentlydiscovered in marine systems are also present in lakes. Notall aggregates in the fresh and seawater systems absorbed thealcian blue stain, however, indicating that not all amorphousparticles in these systems are rich in negatively charged polysaccharides. 相似文献
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X-radiography was used to study annual linear skeletal extension rates of the reef-building scleractinian corals Diploria strigosa and Diploria labyrinthiformis from the high-latitude reefs of Bermuda. Coral samples for X-radiography were collected from seven localities of varying biotopes and depths around the Bermuda platform and band couplets were measured. Mean extension rates of both species were highest on inshore and nearshore reefs, gradually decreasing towards the edge of the Bermuda platform and onto the fore-reef slope. Extension rates of D. labyrinthiformis were statistically higher than those of D. strigosa at three localities, while at the other four, the rates of both species were not statistically separable. extension rates of d. labyrinthiformis were statistically higher than D. strigosa within depths of 20 m and 32 m but not statistically separable at 3 m and 6 m depths. Extension rates of both species decreased significantly with increasing depth (r
2=0.92, P<0.03 for D. labyrinthiformis and r
2=0.95, P<0.02 for D. strigosa). Each species showed an inverse curvilinear relationship between extension rate and depth, the rate of change (i.e. slope) being the same for each species. Comparison of extension rates of each species from Berumuda with published rates of these species from lower latitudes showed an inverse relationship between extension rate and latitude. 相似文献
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