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301.
302.
PEDRO CÓZAR DANIEL VACHARD 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2004,37(4):351-363
Well‐preserved specimens of Calcifolium ? punctatum Maslov from the Guadiato area (Spain) show a great adaptability to environmental modifications. Six morphotypes are recognized: flabellum‐shaped cups, massive erect cups, stockade cups, crustose growth, petals and inter‐cup segments. These morphologies are an adaptative response to fluctuation of the following factors: substratum, light/turbidity/depth, competition for space, influx of micrite/rate of sedimentation, hydrodynamic energy and bioturbation. 相似文献
303.
In Anchusa capensis, where the polyploid divisions are restrictedto a particular time and place in germination, cytophotometricanalysis showed that the polyploid cells arise at the time ofconversion of the globular-shaped embryo to the heart-shapedembryo. In Spinacia oleracea, where the divisions occur throughoutthe growth of the root, these polyploid cells do not arise duringembryogenesis but during germination and subsequent growth. Anchusa capensis Thunb., summer forget-me-not, Spinacia oleracea L., spinach, root meristem, polyploid divisions, determinate divisions, indeterminate divisions, germination, embryogenesis, cytophotometry 相似文献
304.
APARICIO-TEJO PEDRO M.; SANCHEZ-DIAZ MANUEL F.; PENA JOSE I. 《Journal of experimental botany》1980,31(3):839-843
The relationship between transpiration measured gravimetrically,a generalized transpiration equation, and the ratio VPD/rleafwas investigated in Trifolium repens plants subjected to varyingwater potentials. Dawn leaf water potential was measured witha pressure chamber, leaf diffusion resistance with a diffusionporometer, leaf temperatures with a thermistor, and relativehumidity with an aspirated psychrometer. During drought transpirationrates determined by both methods were quite similar particularlyat the lowest water potentials. After rewatering calculatedrates were somewhat higher than measured ones. It is concludedthat transpiration calculated by the indirect method is a usefuland reasonable estimate of transpiration for single plants undervarying water potentials. 相似文献
305.
JORGE S. RAISMAN RITA W. DE CUNIO MARCELO O. CABADA ENRIQUE J. DEL PINO MARTA I. MARIANO 《Development, growth & differentiation》1980,22(3):289-297
Acrosome breakdown in Leptodactylus chaquensis is described: during this process acrosome enlarges, becomes round-shaped and finally disrupts. Low tonicity media (0.025 M sucrose and 1/10 Holtfreter's solutions) favor acrosome breakdown and sperm fertility loosing. High tonicity media (0.250 M sucrose and Holtfreter's solutions) maintain acrosomes in an unreacted stage and sperm fertilizing capacity is preserved. Sperm motility does not seem to be a sufficient condition for the sperm to fertilize and also does not seem to be related with acrosome breakdown. The presence of lectins in the incubation media does not modify the time-course of acrosome breakdown. 相似文献
306.
Calling behaviour in M.convecta females under different temperature and photoperiodic conditions 总被引:1,自引:0,他引:1
Abstract. . The effects of temperature and photoperiod on calling behaviour in females of the Australian common armyworm, Mythimna corwecta (Walker) (Lepidoptera: Noctuidae), were studied in the laboratory. Age at first calling was greater at 15 and 20o C compared with 25o C, but there were no significant differences between 25 and 30o C. Females kept at 10o C did not call, but if transferred at 10 days to 20o C they called after a period similar to the pre-calling period at constant 20o C. Onset time of calling was earlier at 15 and 20o C compared with 25 and 30o C, but there were no significant differences in calling duration. At 20o C, age at first calling was increased by shorter day length (12h and 14h, compared with 16h), and there was an interaction between daylength and moth age affecting the duration of calling. Onset times advanced with longer daylength, but peak calling was later in relation to the lengtii of the scotophase. These results are discussed in connection with migration in M.convecta. Evidence for a circadian rhythm of calling was found in females entrained for 3 and 8 days after emergence under reverse-cycle conditions and then transferred to constant darkness. However, after 56 h and 80 h respectively of darkness, calling became de-synchronized. Subsequently, it appeared to re-synchronize to a different clock, which approximately correlated with the normal photoperiods the moths had experienced during larval development. 相似文献