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91.
A. J. FENLON T. DAVID 《Computer methods in biomechanics and biomedical engineering》2013,16(4):323-339
Abstract A numerical model of the coupled motion of a flexing surface in a high Reynolds number flow is presented for the simulation of flexible polyurethane heart valves in the aortic position. This is achieved by matching a Lagrangian dynamic leaflet model with a panel method based flow solver. The two models are coupled via the time-dependent pressure field using the unsteady Bernoulli equation. Incorporation of sub-cycling in the dynamic model equations and fast pre conditioning techniques in the panel method solver yields efficient convergence and near real-time simulations of valve motion. The generality of dynamic model allows different material properties and/or geometries to be studied easily and interactively. This interactivity is realized by embedding the models within a design environment created using the software IRIS Explorer TM. Two flow domains are developed, an infinite domain and an internal domain using conformal mapping theory. In addition bending stress on the valve is computed using a simple stress model based on spline and circle equation techniques. 相似文献
92.
DAVID BODIE CAROL A. BENNETT-CLARKE KATHLEEN DAVIS JENNIFER P. POSTELWAITE NICOLAS L. CHIAIA ROBERT W. RHOADES 《Somatosensory & motor research》2013,30(3):168-180
Previous experiments from this laboratory have indicated that transection of the infraorbital nerve (ION, the trigeminal \[V] branch that supplies the mystacial vibrissae follicles) at birth and in adulthood has markedly different effects on galanin immunoreactivity in the V brainstem complex. Adult nerve transection increases galanin immunoreactivity in the superficial layers of V subnucleus caudalis (SpC) only, while neonatal nerve transection results in increased galanin expression in vibrissae-related primary afferents throughout the V brainstem complex. The present study describes the distribution of binding sites for this peptide in the mature and developing V ganglion and brainstem complex and determines the effects of neonatal and adult ION damage and the associated changes in galanin levels upon their distribution and density. Galanin binding sites are densely distributed in all V brainstem subnuclei and are particularly dense in V subnucleus interpolaris and the superficial layers of SpC. They are present at birth (P-0) and their distribution is similar to that in adult animals. Transection of the ION in adulthood and examination of brainstem 7 days later indicated marked reductions in the density of galanin binding sites in the V brainstem complex. With the exception of the superficial laminae of SpC, the same reduction in density remained apparent in rats that survived 45 days after nerve cuts. Transection of the ION on P-0 resulted in no change in the density of galanin binding sites in the brainstem after either 7 or 60 days survival. These results indicate that densely distributed galanin binding sites are present in the V brainstem complex of both neonatal and adult rats, that they are located in regions not innervated by galanin-positive axons, and that their density is not significantly influenced by large lesion-induced changes in the primary afferent content of their natural ligand. 相似文献
93.
ABSTRACT Attraction of flying mole crickets to individual males calling in an outdoor arena was influenced significantly by the relative intensity of the males calling in the arena. Louder males attracted more individuals than males whose calling songs were less intense. Making simple assumptions about the acoustic output from calling males and about the flight pattern and response of flying females, the differential attraction can be explained by a mathematical model. Computer simulation of the model was used to examine the importance of a male's intensity relative to others and the effect of distance between males on the attraction of females. The model and its relation to active female choice and passive attraction are discussed. The model makes predictions about differences in spacing behaviour of males that maximize attraction relative to other males. 相似文献
94.
DAVID E. RICHARDSON JEFFREY D. VANWYE AMY M. EXUM ROBERT K. COWEN DOUGLAS L. CRAWFORD 《Molecular ecology resources》2007,7(2):199-207
Ichthyoplankton collections provide a valuable means to study fish life histories. However, these collections are greatly underutilized, as larval fishes are frequently not identified to species due to their small size and limited morphological development. Currently, there is an effort underway to make species identification more readily available across a broad range of taxa through the sequencing of a standard gene. This effort requires the development of new methodologies to both rapidly produce and analyse large numbers of sequences. The methodology presented in this paper addresses these issues with a focus on the larvae of large pelagic fish species. All steps of the methodology are targeted towards high‐throughput identification using small amounts of tissue. To accomplish this, DNA isolation was automated on a liquid‐handling robot using magnetic bead technologies. Polymerase chain reaction and a unidirectional sequencing reaction followed standard protocols with all template cleanup and transferring also automated. Manual pipetting was thus reduced to a minimum. A character‐based bioinformatics program was developed to handle the large sequence output. This program incorporates base‐call quality scores in two types of sample to voucher sequence comparisons and provides suggested identifications and sequence information in an easily interpreted spreadsheet format. This technique when applied to tuna and billfish larvae collected in the Straits of Florida had an 89% success rate. A single species (Thunnus atlanticus) was found to dominate the catch of tuna larvae, while billfish larvae were more evenly divided between two species (Makaira nigricans and Istiophorus platypterus). 相似文献
95.
ALAN D. CHRISTIAN EMY M. MONROE ALLISON M. ASHER JEANNETTE M. LOUTSCH DAVID J. BERG 《Molecular ecology resources》2007,7(4):570-573
Freshwater mussels (Unionidae) are among North America's most imperilled organisms. Mussels produce small larvae (glochidia) that parasitize aquatic vertebrates. We modified the Epicentre QuickExtract protocol to extract DNA from a single glochidium, collected directly from the marsupium of a female mussel, to use as template in polymerase chain reactions (PCRs). Yield per glochidium in a 40 µL extraction volume provided enough DNA for ≥ 15 PCRs per individual. We were successful in using this DNA for microsatellite analysis of up to three loci per individual. Offspring from one female showed evidence for multiple paternity within her brood. Our results are the first documentation of this phenomenon in freshwater mussels. 相似文献
96.
The taxonomic significance of leaf micromorphology in the genus Eugenia L. (Myrtaceae) 总被引:1,自引:0,他引:1
NOORMA WATI HARON DAVID M. MOORE 《Botanical journal of the Linnean Society. Linnean Society of London》1996,120(3):265-277
Leaf micromorphological features of both the Old and New World representatives of Eugenia L. have been studied by light microscopy and scanning electron microscopy. The leaves are hypostomatic and, in the majority of species, the stomata are raised above the epidermis. Trichomes are usually present on the abaxial surface of the New World species. The patterns of abaxial surface sculpturing and arrangement of outer stomatal rims are unique in the New World species. The majority of the Old W'orld species showed different anticlinal wall patterns on the adaxial and abaxial epidermises. In the majority of the New World species the anticlinal wall patterns are more or less the same except in E. axillaris. The paracytic type of stomata, with a non-prominent T-piece cutinization at the poles of the guard cells, is a characteristic feature of the New World species. The taxonomic significance of these features in identification and elucidation of species from both areas is discussed. 相似文献
97.
GEORGE K. RODERICK DAVID H. KAVANAUGH 《Biological journal of the Linnean Society. Linnean Society of London》2012,107(1):95-111
Alpine species often have similar demographic responses to Pleistocene climate changes, but exhibit different spatial patterns of genetic diversity. Using a comparative phylogeographical approach, we examined the factors influencing lineage formation in three alpine carabid beetles of the genus Nebria Latreille inhabiting the California Sierra Nevada. These flightless beetles differ in altitudinal zonation and habitat preferences, but overlap spatially, have limited dispersal capacities and share life history characteristics. Species distribution modelling predicted decreasing population connectivity in relation to increasing altitudinal preferences. Diversity patterns at the cytochrome oxidase subunit I gene revealed north–south genetic structure and recent population growth in all three species. The high‐elevation‐restricted species, Nebria ingens Horn, exhibited a deep phylogeographical split, morphological divergence and evidence of limited, unidirectional gene flow towards the south. This was supported by additional data from three nuclear genes and isolation with migration analysis. Nebria spatulata Van Dyke, inhabiting an intermediate altitudinal range, exhibited fixed morphological differences between northern and southern populations, but showed limited structure. The broadly distributed Nebria ovipennis LeConte showed less structure and lacked morphological variation. Diversification of these Nebria species supports the role of altitudinal zonation in lineage formation and is consistent with the Pleistocene species pump model. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献
98.
99.
MAHMOUD FADL ALI E. DAVID MORGAN 《Biological reviews of the Cambridge Philosophical Society》1990,65(3):227-247
- 1 Chemical communication plays an important part in the lives of insects, and particularly in lives of those that live in groups or social organizations.
- 2 Chemicals which are used in communication in the general sense are called semiochemicals, and there are a number of subdivisions recognized under this title.
- 3 Pheromones are a category of semiochemicals which are used for communication between individuals of the same species.
- 4 Pheromones are in turn subdivided into primer and releaser pheromones. The former produce a relatively long-lasting physiological change in the receiver, and the latter stimulate the receiver to some immediate behavioural response.
- 5 Far more is known about releaser pheromones at present because they are easier to study.
- 6 Nine categories of releaser pheromone are recognized here, used by both social and non-social insects.
- 7 Sex pheromones are widely used to bring the sexes together for mating, and they have been extensively studied in Lepidoptera.
- 8 Invitation pheromones, encouraging the species to feed or oviposit at an explored site, are not extensively known.
- 9 Aggregation pheromones are designed to bring individuals together into groups which may be temporary in sub-social insects, or permanent in social insects.
- 10 Dispersal or spacing pheromones are used by other species to reduce intraspecific competition for scarce resources.
- 11 Alarm pheromones are a broad and sometimes unclearly defined group which communicate alarm or attack, chiefly in colonial species.
- 12 Trail pheromones, applied to a surface by an individual, to be followed by another, are confined to Hymenoptera, Isoptera and a few Lepidoptera as far as is known.
- 13 Territorial and home range pheromones may be widely distributed, but as yet few of them have been recognized.
- 14 Surface and funeral pheromones are even less well known. Surface pheromones may play a large part in species or colony recognition.
- 15 We can expect the number and complexity of pheromones to be much greater in social insects, a part of the subject which until now has received relatively less attention.
- 16 As our understanding of the subject grows we may expect other categories to be added to this list.
100.
Abstract. 1. The relationship between cyanogenesis in bracken fern and the insect fauna feeding on the plant was investigated over a 3 year period. The most common insects between May and July, while cyanide levels were high, were the sawflies Strongylogaster impressata Provancher, S.multicincta Norton, Aneug-menus fzavipes (Norton), the aphid Macrosiphum euphorbiae (Thomas) and a microlepidopteran species of Monochroa .
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds. 相似文献
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds. 相似文献