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131.
Robust properties of likelihood ratio tests 总被引:2,自引:0,他引:2
132.
AVNER YAYON JOHN A. VANDE WAA MALKA YAYON TIMOTHY G. GEARY JAMES B. JENSEN 《The Journal of eukaryotic microbiology》1983,30(4):642-647
The erythrocytic developmental cycle of Plasmodium falciparum can be conveniently divided into the ring, trophozoite, and schizont stages based on morphology and metabolism. Using highly synchronous cultures of P. falciparum, considerable variation was demonstrated among these stages in sensitivity to chloroquine. The effects of timed, sequential exposure to several clinically relevant concentrations of chloroquine were monitored by three techniques: morphological analysis, changes in the rate of glucose consumption, and changes in the incorporation of 3H-hypoxanthine into parasite nucleic acids. All three techniques gave essentially identical results. The trophozoite and schizont stages were considerably more sensitive to the drug than ring-stage parasites. Chloroquine sensitivity decreased as nuclear division neared completion. The increase in chloroquine sensitivity was coincident with a marked rise in the rate of glucose consumption and nucleic acid synthesis. The rate of nucleic acid synthesis decreased as schizogony progressed while glucose consumption continued at high rates during this process. The degree of chloroquine sensitivity was not highly correlated with either metabolic activity. 相似文献
133.
Natural convection from leaves at realistic Grashof numbers 总被引:4,自引:2,他引:2
Abstract. The boundary layer resistance of model leaves was measured in still air, at a range of leaf-to-air temperature differences. The results were compared to those calculated from standard formulae for natural convection. The agreement between observed and calculated was only satisfactory when Grashof numbers exceeded about 105. At the lower Grashof numbers, which often prevail in nature, the observed rates of heat transfer considerably exceeded those calculated. 相似文献
134.
Comparative ethological studies of closely related species canplace into clear perspective the functions of behavioral traitsas species diverge and adapt to different environments. In thispaper we contrast the reproductive behavior of species withintwo crustacean groups: the mantis shrimps (stomatopods) andthe fiddler crabs (genus Uca). For the stomatopods, we identifyprobable selective relationships between features of species'ecology and their mating systems. Population density, the kindand availability of shelters in which these shrimps live, theintensity of predation and spawning cycles all play importantroles in molding reproductive behavior in this group. Associationsbetween the ecology and mating systems of fiddler crabs havebeen discussed recently elsewhere. Here we focus on a comparativeanalysis of sexual communication in these crabs. A study ofcompetitive courtship signaling and mate choice in the fiddlercrab Uca beebei has shown that certain male courtship signalsare highly attractive probably because they exploit female sensory-responsesystems that have been molded by selection for escape from predators.Interspecific comparison of male courtship displays and theresponses of females to these displays suggest that sensoryexploitation may play an important role in the evolution ofsexual signals in the genus. Comparative studies have advancedour understanding of how natural and sexual selection affectthe reproductive behavior of both stomatopods and fiddler crabs. 相似文献
135.
JOHN MAGGS 《Austral ecology》1991,16(1):47-51
Nitrogen mineralization and nitrification were measured using in situ incubations for 12 periods of 1 month in a structurally complex rainforest with basaltic soil, and an adjacent structurally simple rainforest with less fertile soil formed on metamorphic rock. The study was undertaken near Lake Eacham on the Atherton Tableland in northeast Queensland. Cumulative nitrogen mineralization for 1 year did not differ between forests. It amounted to 265 ± 13 μg N g-1 oven dry soil at the upper position (0–7.5 cm) and 122 ± 11 μg N g-1 oven dry soil at the lower position (7.5–15 cm; mean ± s.e. for pooled data). Rates were highest during the wet season but were not strongly correlated with moisture content or temperature. Relative nitrification (cumulative nitrate-nitrogen production expressed as a percentage of cumulative nitrogen mineralization) at the upper position was significantly higher in the complex than the simple forest (100% c.f. 88%). At the lower position it amounted to 100% for cumulative data in both forests. Nitrate was the dominant form of inorganic nitrogen in the complex forest but in the simple forest nitrate and ammonium were of similar importance. The association between forest physiognomic structure and nutrient status at Lake Eacham represents a more general pattern in rainforests of northeast Queensland and further study is needed to ascertain whether results from this study apply more generally. 相似文献
136.
Nonparametric tests of the Markov model for survival data 总被引:1,自引:0,他引:1
137.
JOHN C. W. COPE 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1992,25(4):439-441
A lappeted microconch specimen of the phylloceratid ammonoid Juraphyllites from the Tethyan Jurassic of Anatolia (Turkey) indicates that sexual dimorphism in this group was established as early as in the early Lower Pliensbachian (Lower Jurassic) and that dimorphism in this genus of the Phylloceratina follows the same pattern as that proven [or many groups of the Ammonitina. This is the earliest record of well-developed lateral lappets in the Mesozoic Ammonoidea 相似文献
138.
JOHN C. CLAMP 《The Journal of eukaryotic microbiology》1992,39(6):732-740
One species of Lagenophrys and two species of Operculigera are described for the first time. Lagenophrys machaerigera n. sp. was discovered on the freshwater crab Gecarcinautes goudoti and varies between two extreme forms in the structure of its lorica aperture. Operculigera carcini n. sp. was also found on G. goudoti and exhibits several characteristics that set it apart from other members of its genus. Some of these characteristics also suggest a phylogenetic link between O. carcini and the genus Lagenophrys. Operculigera madagascarensis n. sp. was discovered on the parastacid crayfish Astacoides granulimanus. The occurrence of O. madagascarensis on a Madagascan parastacid and other species of Operculigera on Chilean parastacids suggests that parastacids are the oldest hosts of the genus Operculigera. Continental drift is the most likely mechanism by which species of Operculigera and parastacids could have been dispersed to distant parts of the southern hemisphere. The absence of Operculigera on Australian parastacids may be due to its replacement by the genus Setonophrys on those hosts. 相似文献
139.
TWO topics on decapod larval biology are discussed: retentionand recruitment of decapod larvae to the parental populationand the ecological role of decapod larvae in the water column. Most decapods have retained a planktonic larval phase whichis generally interpreted as a mechanism for increased dispersal.Evidence of restricted gene flow and biological/physical interactionresearch have suggested that larvae can be retained and recruitedto the parental population via mesoscale processes. To fullyunderstand recruitment processes improved estimates of mortalityrates for planktonic larval stages will be required. Recentevidence suggests that mortality rates are not constant overthe complete larval developmental period but decrease with time. During some seasons meroplankton including decapod l arvae canconstitute more than 50% of the plankton biomass. The quantityof energy transferred into the water column can be significant.Their role in planktonic ecology may be significant and additionalresearch is required. 相似文献
140.
Wind dispersal and settling of first-instar crawlers of the cochineal insect Dactylopius austrinus (Homoptera: Coccoidea: Dactylopiidae) 总被引:1,自引:0,他引:1
Abstract. 1. The efficiency of D.austrinus as a biological control agent depends on successful colonization of the cactus weed Opuntia aurantiaca .
2. Unlike other coccoid insects, the female crawlers (first-instar larvae) of cochineal insects develop long wax fiaments on the dorsal surface of the body that reduce their terminal velocity in air and enhance wind dispersal.
3. Dactylopiid males are dispersed as winged adults and male crawlers of D.austrinus have fewer and shorter filaments than the females and they are blown a shorter distance in a wind tunnel.
4. Vertical and horizontal wind dispersal of D.austrinus from O.aurantiaca in the field is usually very limited, but was greatly improved when crawlers were launched from an elevated 'tower'.
5. Preparatory to dispersal, female crawlers climb to the top of the host plant and 'take-off' from there. This behaviour is most marked in crawlers 2–3 days old at which stage the wax filaments are best developed: the behaviour is never manifest following artificial 'dispersal'.
6. Final settling on cladodes of the host plant is a function of the age of the female crawlers and of the condition of the cladodes.
7. When given a choice, approximately equal numbers of crawlers settled on cladodes that had received high and low fertilizer treatments. More crawlers settled on cladodes that had been kept in the shade than on those kept in the sun, and on basal rather than terminal cladodes.
8. The highest percentage of crawlers settled on cladodes that were 20% dehydrated. Settling success was much lower on more desiccated cladodes. 相似文献
2. Unlike other coccoid insects, the female crawlers (first-instar larvae) of cochineal insects develop long wax fiaments on the dorsal surface of the body that reduce their terminal velocity in air and enhance wind dispersal.
3. Dactylopiid males are dispersed as winged adults and male crawlers of D.austrinus have fewer and shorter filaments than the females and they are blown a shorter distance in a wind tunnel.
4. Vertical and horizontal wind dispersal of D.austrinus from O.aurantiaca in the field is usually very limited, but was greatly improved when crawlers were launched from an elevated 'tower'.
5. Preparatory to dispersal, female crawlers climb to the top of the host plant and 'take-off' from there. This behaviour is most marked in crawlers 2–3 days old at which stage the wax filaments are best developed: the behaviour is never manifest following artificial 'dispersal'.
6. Final settling on cladodes of the host plant is a function of the age of the female crawlers and of the condition of the cladodes.
7. When given a choice, approximately equal numbers of crawlers settled on cladodes that had received high and low fertilizer treatments. More crawlers settled on cladodes that had been kept in the shade than on those kept in the sun, and on basal rather than terminal cladodes.
8. The highest percentage of crawlers settled on cladodes that were 20% dehydrated. Settling success was much lower on more desiccated cladodes. 相似文献