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101.
102.
Katrin Strauss Holger Scharpenberg Robin M. Crewe Felix Glahn Heidi Foth Robin F. A. Moritz 《Behavioral ecology and sociobiology》2008,62(9):1523-1531
Queen pheromones interfere with worker reproduction in social insects. However, there is still an unresolved question as to
whether this pheromone acts as an “honest” signal for workers, giving a reliable indication of the queen’s reproductive value,
or as a suppressive agent, inhibiting worker reproduction independent of the queen’s reproductive capacity. In honeybees (Apis mellifera), the queen’s mandibular gland secretion, a mix of fatty acids and some aromatic compounds, is crucial for regulating the
reproductive division of labor in the colony inhibiting ovary development in workers. We quantified the mandibular gland secretions
of virgin, drone-laying, and naturally mated queens using gas chromatography to test whether the queens’ mating, ovary activation,
or the reproductive value for workers correlated with the composition of the secretion. Although the absolute amounts of the
“queen substance” 9-oxo-2(E)-decenoic acid (9-ODA) were similar among the three groups, the proportions of 9-ODA decreased
with increasing reproductive quality. Furthermore, the ratios of queen to worker compounds were similar in all three treatment
groups, irrespective of the reproductive capacity. A multivariate analysis including all six compounds could not separate
drone-laying queens from naturally mated ones, both with active ovaries but only the latter ensuring colony survival. We suggest
that the mandibular gland pheromones are unlikely to function as reliable indicators of queen reproductive value and rather
operate as an agent to suppress worker reproduction. This does not exclude the possibility that other “honest” pheromone signals
exist in the honeybee colony, but these would have to arise from other semiochemicals, which could be produced by both the
queen and the brood. 相似文献
103.
K. F. Ehrlich 《Marine Biology》1974,24(1):39-48
Plaice (Pleuronectes platessa L.) were sampled during periods of growth and starvation, from the end of the yolk-sac stage through metamorphosis, for changes in water, triglyceride, carbohydrate, total nitrogen, total carbon, and ash. The percentage of water in larvae decreased continuously during development. During post-hatching growth (up to late Stage 2) nitrogen and carbohydrate were laid down faster than triglyceride. The pattern changed during later larval development. The early deposition of protein in preference to neutral fat suggests that conversion of food during growth, without simultaneously laying down fatty energy stores, may be advantageous to pelagic marine fish larvae. During starvation the percentage of water in plaice larvae increased. Triglyceride, carbohydrate, nitrogen and carbon (as a percentage of the dry body weight) decreased during starvation, but ash increased sharply. The continuous use of nitrogen during starvation may be a catabolic adaptation to the marine environment. 相似文献
104.
105.
M. Felix V. Perez-Puyana A. Romero A. Guerrero 《Journal of Polymers and the Environment》2017,25(1):91-100
Bioplastic materials from renewable polymers, like proteins, constitute a highly interesting field for important industrial applications such as packaging, agriculture, etc., in which thermo-mechanical techniques are increasingly being used. This study assesses bioplastic materials produced by injection from blends previously prepared in a batch mixer using various protein concentrates and isolates. A mixing time of 5 min has been selected in order to ensure correct homogenous blends. A comparison between different protein-based specimens was performed by dynamic mechanical thermal analysis, tensile strength, water uptake and transmittance tests. The comparison reveals that the protein nature and the percentage of plasticizer lead to bioplastics with different properties and, consequently, different applications. Protein concentrates and isolates, wastes and surpluses from the food industry, may be useful for producing bioplastics with suitable mechanical properties and processability, as well as biodegradability, by means of suitable mixing and injection moulding conditions. 相似文献
106.
Werth S Wagner HH Gugerli F Holderegger R Csencsics D Kalwij JM Scheidegger C 《Ecology》2006,87(8):2037-2046
Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment. 相似文献
107.
Grunion Leuresthes tenuis (Ayres), an atherine fish, were reared, from artificially fertilized eggs to 160 days posthatching, at temperatures from 18.0° to 25.4° C. The rearing was carried out in five 60 l rectangular containers and two hard moulded plastic pools holding 60 and 450 l. The growth rate was highly correlated with temperature at least up to metamorphosis. Thereafter, the effect of temperature on growth, within lethal limits, appeared to be lost or at least masked by other factors. At low densities, after metamorphosis, growth was proportional to the population density. Size and shape of the rearing containers also influenced the growth rate. 相似文献
108.
Resting schools of juvenile grunts (less than 12 cm length), composed primarily of Haemulon flavolineatum and H. plumieri, were studied from 1972 to 1976 on a series of patch reefs surrounded by seagrass beds on the northeast coast of St. Croix, U.S. Virgin Islands. Juvenile grunts form large inactive multispecies schools in reef areas by day. Repeated censuses over several years reveal that certain parts of the reef, particularly those with large formations of the corals Porites porites and Acropora palmata, are traditional schooling areas. When the fishes reach a size of about 15 cm, the H. plumieri form homotypic schools which roam the patch reefs but are no longer associated with particular formations of coral. In contrast, larger H. flavolineatum are uncommon on the patch reefs and they may move offshore to deeper water. The schools of juvenile grunts migrate some distance away (often 100 to 300 m) into seagrass-covered areas to feed on invertebrates at dusk each day. The routes which are followed into the seagrass beds are precise and persist over years. At dawn the grunts return to the reef on the same routes. Mass marking and release experiments show that juvenile grunts will move over long distances (approximately 3 km) to reach a home reef. 相似文献
109.
Techniques and Guidelines for Monitoring Neotropical Butterflies 总被引:11,自引:0,他引:11
Helen R. Sparrow Thomas D. Sisk Paul R. Ehrlich Dennis D. Murphy 《Conservation biology》1994,8(3):800-809
Long-term monitoring of selected species can identify changes in biological diversity, permitting the timely adjustment of management activities to reverse or avoid undesired trends. This paper addresses several related issues bearing on the development of inexpensive and easily implemented monitoring programs for tropical butterflies. First, we discuss the use of butterflies as ecological indicators. Next, we present field evaluations of butterfly sampling techniques, indicating that: (1) light-gap size greatly affects sampling results in forests and should be of critical concern in site selection and sampling design; (2) baited traps and visual censuses provide complementary data on butterfly abundances; (3) monitoring a subset of locally common butterfly species can provide data for comparing community composition and relative abundance of species in areas where species inventories are incomplete. Drawing on these results, we develop guidelines for designing monitoring programs. These address the formulation of explicit questions to be addressed through monitoring and the selection of appropriate study sites, study species, sampling techniques, and sampling frequency. A protocol for the ongoing butterfly monitoring program that emerged from these studies is appended. The techniques and guidelines presented here are intended to serve as an adaptable model for biologists designing monitoring projects to help guide applied conservation efforts in the tropics. 相似文献
110.