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31.
Three species of the arcto-boreal, large gastropod Neptunea , described by Linnaeus in 1758 and 1771, occur in large numbers over wide areas of the inshore North Atlantic and adjacent Arctic seas and are conspicuous among Pliocene and Pleistocene molluscs in the Icelandic, North Sea, and western Mediterranean basins. Selections of lectotypes for these species from shells in the collection of the Linnean Society of London, and designations of their type localities, establish the identity of Linnaeus' neptunes and more accurately determine their geographic and geologic distribution. The geographic range of Neptunea (Neptunea) antiqua (L.), the type species, now extends from southern Norway to the northern Biscay coast of France and from the westernmost Baltic Sea to southwestern Ireland; this species also occurs in Pliocene-Holocene marine deposits in West and East Germany, Sweden, the Netherlands, England and France. Its type locality is determined to be the North Sea. N. (Neptunea) despecta (L.) lives in the eastern Canadian Arctic, off southern Greenland, the Barents Sea, and North Atlantic as far south as Massachusetts and Portugal; it also occurs in Pliocene-Holocene strata of eastern Canada, east-central Greenland, Norway (including Svalbard), the Soviet Union, Sweden and England. Its type locality is determined to be the postglacial deposits at Uddevalla in southwestern Sweden. N. (Sulcosipho) contraria (L.) now extends from the southern Biscay coast of France to Cape Spartel, Morocco; this species also occurs in Pleistocene and lower Holocene sequences of the western Mediterranean. Its type locality is determined to be Vigo Bay, Spain. A closely related fossil species, N. (S.) angulata (S. V. Wood), occurs in Pliocene and Pleistocene deposits of the North Sea basin. 相似文献
32.
Omotayo Sarafadeen Amuda Olumuyiwa Idowu Ojo Theresa Ibibia Edewor 《Bioremediation Journal》2007,11(4):183-194
The shell of the seed of Chrysophyllum albidum carbon was used to adsorb lead (Pb) from aqueous solution, the sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration, and particle size on adsorption were also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The first-order rate equation by Lagergren was tested on the kinetic data and the adsorption process followed first-order rate kinetics. Isotherm data were analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms; the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 72.1 mg Pb (II) g- 1 at initial pH of 5.0 at 30°C for the particle size of 1.00 to 1.25 mm with the use of 2.0 g/100 ml adsorbent mass. The structural features of the adsorbent were characterized by Fourier transform infrared (FTIR) spectrometry; the presence of hydroxyl, carbonyl, amide, and phosphate groups confirms the potential mechanism adsorption of the adsorbent. This readily available adsorbent is efficient in the uptake of Pb (II) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater. 相似文献
33.
S. S. C. ONYEKWELU 《Botanical journal of the Linnean Society. Linnean Society of London》1990,103(2):133-138
ONYEKWELU, S. S. C, 1990. Germination, seedling morphology and establishment of Cotnbretum bauchiense Hutch. & Dalz. (Combretaceae). Cotnbretum bauchiense is a suffrutex with short, erect, usually herbaceous stems arising from a woody root stock. It appears in savanna soon after fire and (lowers within a few weeks. The fruits germinate in 5–6 days. The germination is cryptogeal. On germination the true radicle and the apparent radicle formed by fused cotyledon stalks push down into the soil, carrying the plumule with them. The cotyledon lamina and part of the fused cotyledon stalks remain above the soil. Both the apparent radicle and the true radicle produce roots. Below the soil at the joint of the apparent radicle and the true radicle the plumule produces 1–3 shoots which grow out to the surface of the soil. The underground portion of the shoot bears scale leaves, from which the plant regenerates when the aerial shoot is damaged by fire. This type of germination is an adaptation that ensures successful establishment in an environment that is subjected to fire. 相似文献
34.
Alexandra Zieritz Antonio G. Checa David C. Aldridge Elizabeth M. Harper 《Journal of Zoological Systematics and Evolutionary Research》2011,49(1):6-15
Microprojections of unionoid shells are virtually unstudied but could be important characters for resolving questions on the phylogeny and ecology of these bivalves. By investigating 26 unionoid and three species of their closest living relatives, the Trigonioida, using scanning electron microscopy, we identified three types of periostracal microprojections. (1) Microridges were present only in one species from each of the two unionoid families Mycetopodidae (Anodontites trapesialis) and Iridinidae (Chambardia bourguignati) and may represent a synapomorphy for the mycetopodid‐iridinid clade. In A. trapesialis, microridges were additionally equipped with (2)ensp;flag‐like projections (microfringes), possibly a synapomorphic character for the Mycetopodidae. Examination of partially bleached specimens indicated that both microridges and microfringes are predominantly or purely organic. In contrast, previously undescribed (3) spicule‐like spikes represent calcifications within the periostracum. These were found in 20 of the 29 species and four of the six unionoid families. Spikes were particularly large and abundant in umbonal (juvenile) shell regions and species characteristic of fast‐flowing habitats. These structures may thus serve in protecting the periostracum and shell underneath, and/or stabilizing life position by increasing shell friction. Microfringes and microridges, on the other hand, possibly aid in the orientation of the mussel within the sediment. 相似文献
35.
D A Wharton 《Experimental parasitology》1979,48(3):398-406
The ability of embryonating eggs of Ascaris lumbricoides to avoid desiccation by reducing the loss of water through the egg shell was investigated. When exposed to desiccation the eggs lost water at a rate dependent upon the relative humidity and ambient temperature, eventually resulting in the collapse of the eggs and the death of the enclosed embryo. The eggs are small with a large surface to volume ratio. A low permeability to gaseous exchange thus restricts water loss while still ensuring an adequate supply of oxygen for embryonic development. Relative humidity did not appear to affect the rate of development. In eggs exposed to desiccation at various constant temperatures, the rate of water loss increased as an exponential function of increasing temperature. When eggs were exposed to various temperatures before exposure to desiccation at 22 C, the rate of water loss increased as a function of increasing pretreatment temperature. After exposure to 63–65 C, the ability of the egg shell to slow down the loss of water was destroyed. These phenomena suggest that there is not a simple “critical” or “transition” temperature, but a gradual melting of the complex mixture of components forming the lipid layer. 相似文献
36.
J. B. Richards D. R. Lloyd B. Kuehlewind L. Militello M. Paredez L. Solberg Woods A. A. Palmer 《Genes, Brain & Behavior》2013,12(5):490-502
A fundamental challenge for any complex nervous system is to regulate behavior in response to environmental challenges. Three measures of behavioral‐regulation were tested in a panel of eight inbred rat strains. These measures were: (1) sensation seeking as assessed by locomotor response to novelty and the sensory reinforcing effects of light onset, (2) attention and impulsivity, as measured by a choice reaction time task and (3) impulsivity as measured by a delay discounting task. Deficient behavioral‐regulation has been linked to a number of psychopathologies, including ADHD, Schizophrenia, Autism, drug abuse and eating disorders. Eight inbred rat strains (August Copenhagen Irish, Brown Norway, Buffalo, Fischer 344, Wistar Kyoto, Spontaneous Hypertensive Rat, Lewis, Dahl Salt Sensitive) were tested. With n = 9 for each strain, we observed robust strain differences for all tasks; heritability was estimated between 0.43 and 0.66. Performance of the eight inbred rat strains on the choice reaction time task was compared to the performance of outbred Sprague Dawley (n = 28) and Heterogeneous strain rats (n = 48). The results indicate a strong genetic influence on complex tasks related to behavioral‐regulation and indicate that some of the measures tap common genetically driven processes. Furthermore, our results establish the potential for future studies aimed at identifying specific alleles that influence variability for these traits. Identification of such alleles could contribute to our understanding of the molecular genetic basis of behavioral‐regulation, which is of fundamental importance and likely contributes to multiple psychiatric disorders . 相似文献
37.
Natural climate solutions versus bioenergy: Can carbon benefits of natural succession compete with bioenergy from short rotation coppice? 总被引:1,自引:0,他引:1
Gerald Kalt Andreas Mayer Michaela C. Theurl Christian Lauk Karl‐Heinz Erb Helmut Haberl 《Global Change Biology Bioenergy》2019,11(11):1283-1297
Short rotation plantations are often considered as holding vast potentials for future global bioenergy supply. In contrast to raising biomass harvests in forests, purpose‐grown biomass does not interfere with forest carbon (C) stocks. Provided that agricultural land can be diverted from food and feed production without impairing food security, energy plantations on current agricultural land appear as a beneficial option in terms of renewable, climate‐friendly energy supply. However, instead of supporting energy plantations, land could also be devoted to natural succession. It then acts as a long‐term C sink which also results in C benefits. We here compare the sink strength of natural succession on arable land with the C saving effects of bioenergy from plantations. Using geographically explicit data on global cropland distribution among climate and ecological zones, regionally specific C accumulation rates are calculated with IPCC default methods and values. C savings from bioenergy are given for a range of displacement factors (DFs), acknowledging the varying efficiency of bioenergy routes and technologies in fossil fuel displacement. A uniform spatial pattern is assumed for succession and bioenergy plantations, and the considered timeframes range from 20 to 100 years. For many parameter settings—in particular, longer timeframes and high DFs—bioenergy yields higher cumulative C savings than natural succession. Still, if woody biomass displaces liquid transport fuels or natural gas‐based electricity generation, natural succession is competitive or even superior for timeframes of 20–50 years. This finding has strong implications with climate and environmental policies: Freeing land for natural succession is a worthwhile low‐cost natural climate solution that has many co‐benefits for biodiversity and other ecosystem services. A considerable risk, however, is C stock losses (i.e., emissions) due to disturbances or land conversion at a later time. 相似文献
38.
Carbon pool densities and a first estimate of the total carbon pool in the Mongolian forest‐steppe 下载免费PDF全文
Choimaa Dulamsuren Michael Klinge Jan Degener Mookhor Khishigjargal Tselmeg Chenlemuge Banzragch Bat‐Enerel Yolk Yeruult Davaadorj Saindovdon Kherlenchimeg Ganbaatar Jamsran Tsogtbaatar Christoph Leuschner Markus Hauck 《Global Change Biology》2016,22(2):830-844
The boreal forest biome represents one of the most important terrestrial carbon stores, which gave reason to intensive research on carbon stock densities. However, such an analysis does not yet exist for the southernmost Eurosiberian boreal forests in Inner Asia. Most of these forests are located in the Mongolian forest‐steppe, which is largely dominated by Larix sibirica. We quantified the carbon stock density and total carbon pool of Mongolia's boreal forests and adjacent grasslands and draw conclusions on possible future change. Mean aboveground carbon stock density in the interior of L. sibirica forests was 66 Mg C ha?1, which is in the upper range of values reported from boreal forests and probably due to the comparably long growing season. The density of soil organic carbon (SOC, 108 Mg C ha?1) and total belowground carbon density (149 Mg C ha?1) are at the lower end of the range known from boreal forests, which might be the result of higher soil temperatures and a thinner permafrost layer than in the central and northern boreal forest belt. Land use effects are especially relevant at forest edges, where mean carbon stock density was 188 Mg C ha?1, compared with 215 Mg C ha?1 in the forest interior. Carbon stock density in grasslands was 144 Mg C ha?1. Analysis of satellite imagery of the highly fragmented forest area in the forest‐steppe zone showed that Mongolia's total boreal forest area is currently 73 818 km2, and 22% of this area refers to forest edges (defined as the first 30 m from the edge). The total forest carbon pool of Mongolia was estimated at ~ 1.5?1.7 Pg C, a value which is likely to decrease in future with increasing deforestation and fire frequency, and global warming. 相似文献
39.
Ingo Burghardt 《Molluscan research.》2015,35(1):37-50
The genus Rhagada is the second most diverse camaenid genus in Australia. We examined anatomical and mitochondrial characters of previously unidentified material from the Kimberley that was earmarked to potentially represent new species in recently published molecular phylogenetic studies. Our comparisons revealed that specimens from Gibbings Island (‘R. sp. Gibbings’) were morphologically and genetically most similar to Rhagada cygna from the Dampier Peninsula. Hence, ‘R. sp. Gibbings’ is considered to be identical to R. cygna. In addition, we found that R. cygna as so delimited is not clearly distinguished from the second species on the Dampier Peninsula, Rhagada bulgana. Both species differ rather subtly in anatomical and mitochondrial characters, indicating their close relationships and potentially incomplete evolutionary differentiation. Furthermore, we describe two new species based on comparative morphology and mitochondrial sequences: Rhagada worora n. sp. from the Prince Regent Reserve in the Kimberley and Rhagada karajarri n. sp. from Dampierland. The present study confirms that species in Rhagada are best identified by means of both morphological and molecular data.http://zoobank.org/urn:lsid:zoobank.org:pub:556E1866-6F9E-4CC0-8ACF-CD56E929501F 相似文献
40.
We used the polymerase chain reaction (PCR) and direct DNA sequencing to study genetic variation within and among populations of Atlantic cod, Gadus morhua , in the western North Atlantic. In a 307 bp region of the mitochondrial cytochrome b gene, 24 variable nucleotide positions define 24 genotypes, which differ by from one to six nucleotide substitutions. Greenland cod ( G. ogac ) differs from the most similar G. morhua genotype by an additional 12 nucleotide substitutions. Silent transitions dominate both intra- and interspecific comparisons, however four nucleotide substitutions within morhua result in amino acid replacements. Direct sequencing of DNA reveals substantially more of the genetic variation that exists within and between species than do previous indirect methods based on restriction fragment length polymorphisms, and thus has far greater potential to quantify such differences as may exist among fish stocks. Preliminary experiments also indicate that automation of DNA sequencing provides an efficient, rapid, and accurate means for detection of genetic variation in natural populations offish. 相似文献