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931.
Immature fruits of Aesculus yield powerful stimuli to growthand cell division. Therefore, the developing fruit of Aesculuswoerlitzensis Koehne has been investigated from pollinationto maturity. The fluid, or liquid endosperm, which containsthe growth-promoting substances is produced in a large vesiclewhich forms at the chalazal tip of the embryo sac. As the vesiclegrows, it encroaches upon the nucellus and, when the embryodevelops, one of its cotyledons penetrates into the vesicleof the embryo sac where it grows and absorbs the contents. Theembryo, which has only a vestigial suspensor, reaches the vesicleby growing along the neck of the long curved embryo sac. Thecotyledon which first penetrates the vesicle grows into a massivestructure; the other remains small. The tip of the cotyledonseems to function as an absorbing surface, for the endospermwith which it comes into contact disorganizes. Fertilizationand the presence of a viable embryo at the micropylar end ofthe embryo sac therefore sets in train a number of other events.These are the extensive development of the nucellus at the chalazalend of the embryo sac, the swelling of the vesicle and the formationof a free nuclear and some cellular endosperm, and the disorganizationof the nucellus as it is encroached upon by the vesiculate embryosac. Attention is directed to the organization of the nucellusin the vicinity of the embryo sac. Files or richly protoplasmicnucellar cells(hypostase) which converge upon the chalazal tipof the embryo sac suggest a principal route by which the vesiclemay be nourished. Special attention is drawn to the very differentsizes of cells, their nuclei and nucleoli, in the differentparts of the nucellus. The growth and development of the embryohas also been traced from the zygote to the mature seed. Thenutritive role of the veaiculate embryo sac, and the supplyof growthstimulating substances, through the function of a cotyledonas an absorbing organ, are now seen as important features ofthe development of the Aesulus embryo in the ovule. Many outstandingproblems still remain. The sequential events that follow fertilizationin the different interdependent regions (nucellus, embryo sac,cotyledon, &c.) are here described, but not casually explained. 相似文献
932.
This investigation was conducted to examine the contribution of intrasite variation on the volar forearm to the overall variation in irritation under the conditions of a soap chamber test. Six sites on each forearm of human volunteers were patched with an eight percent aqueous solution of a commercial bar soap, known to be moderately irritating. Clinical evaluations of the sites were made independently by two judges twenty-four hours after the first patch application and six hours following applications conducted over the next four consecutive days. Site to site variability was estimated to be only 3.2% of the total variance component. It is suggested that as with any biologic assay, this variance can be reduced by an increase in the number of panelists. 相似文献
933.
Abstract. Female preferences for conspicuous male calls have been documented in many groups. However, relatively few studies have examined the metabolic costs associated with the production of call types preferred by females. We measured the oxygen consumption of calling male Gryllus lineaticeps Stål crickets using closed chamber respirometry. Calling song was recorded concurrently. The average increase in mass-specific oxygen consumption during calling was 2.7 times basal rates of oxygen consumption, and calling males consumed approximately 1.2ml O2 g-l h-1 . Oxygen consumption increased with increasing chirp rate and pulse duration, but not with increasing chirp duration. Females of this species prefer higher chirp rates, thus some call types that increase the male's attractiveness to females require more metabolic energy to produce. 相似文献
934.
TIMOTHY J. SMYSER JAMES C. BEASLEY ZACHARY H. OLSON OLIN EUGENE RHODES JR. 《The Journal of wildlife management》2010,74(6):1405-1416
Abstract: Passive treatment of raccoons (Procyon lotor) through distribution of vaccine-laden baits recently has emerged as a potential solution to address health and economic conflicts associated with raccoon rabies and may have applications in the management of other pathogens carried by raccoons if frequent bait deployments are used. Consumption of baits by nontarget species reduces the efficiency in which baits can be used to manage wildlife disease, although no study has explicitly evaluated the influence of bait competitor density on the ability to treat raccoons. Our objectives were to use the biomarker Rhodamine B (RB) to 1) evaluate patterns of raccoon bait acceptance as a function of competition with Virginia opossums (Didelphis virginiana), the dominant bait competitor; 2) characterize attributes of opossum bait acceptance to improve efficiency of raccoon treatment; and 3) evaluate the effect of repeated bait exposure on rates of bait acceptance as may be required in the management of wildlife disease issues beyond rabies. Identifying bait consumption by individuals based on the presence of an RB mark in a sample of whiskers, we used logistic regression to model raccoon and opossum bait acceptance as a function of bait availability, previous exposure to baits, demographic attributes, and an index of time spent in the baited area (residency index). For both raccoons and opossums, the best measure of bait availability was the variable number of baits per opossum. The most parsimonious logistic regression model for raccoon bait acceptance included the variables baits per opossum, exposure history, and residency index. The strength of the variable baits per opossum relative to competing measures of bait availability indicated bait consumption by opossums significantly limited the ability to treat raccoons. The most parsimonious model for opossum acceptance was composed of the variables baits per opossum, sex, weight, residency index, baits per opossum X sex, and weight X sex. Patterns of opossum bait acceptance likely were driven by effects of bait availability and sex-dependent differences in movement. Our results call attention to the importance of bait competition in limiting the ability to effectively treat raccoon populations through distribution of baits and suggest managers incorporate information on density of bait competitors, particularly opossums, in allocation of baits. 相似文献
935.
Chlorophyll content decreased when excised lemon fruits were exposed to light. A quantitative model for the photodestruction of chlorophyll exhibited reasonable agreement with data on in vivo destruction of chlorophyll. Photodestruction of chlorophyll was enhanced by treating fruit with 2′,4′-dichloro-l-cyanoethane-sulphonanilide (R33417). Measurable enhancement of chlorophyll destruction was observed with concentrations of R33417 as low as 10 μg/l. Maximum activity was achieved at approximately 600 μg/1. R33417 treatment enhanced photodestruction of chlorophyll to a greater extent at higher photon flux densities. 相似文献
936.