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1.
Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites ( F =5.97, P <0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance. 相似文献
2.
Robert Ornduff 《Plant Systematics and Evolution》1977,127(4):293-297
Hedyotis caerulea, a spring flowering herb widely distributed in eastern North America, has distylous flowers that differ by a number of morphological and physiological traits. The presence of a strong incompatibility system is indicated by the fact that intramorph crosses or self-pollinations produced little or no seed and intermorph crosses produced copious seed. An unusual homostyle was located that had most floral characters intermediate between pin and thrum flowers, although its pollen size was that of pin. The homostyle was only moderately self-compatible, and its pollen did not behave as pin pollen on thrum stigmas. It appears that, despite their intermediate position and morphology, the homostyle stigmas were fundamentally pin. Although the exceptional rarity of the homostyle suggests that it is an inadaptive failure, workers should watch for its further occurrence since additional study of it may provide insights into the genetic and physiological basis of heterostyly in theRubiaceae. 相似文献
3.
E. S. Krafsur 《Biochemical genetics》1993,31(5-6):231-240
Polyacrylamide gel electrophoresis was used to resolve allozymes in the cosmopolitan blood-feeding stable fly,Stomoxys calcitrans (L.). Nineteen of 38 loci were polymorphic (53%). Mean heterozygosities among all loci and among only polymorphic loci were 0.096 and 0.182, respectively. These gene diversity measures are about half those among other muscid Diptera. Variation in gene frequencies was examined in 10 natural stable fly populations from Iowa and Minnesota. Gene frequencies were homogeneous at five of eight loci among six populations in 1990 and eight of eight loci among four populations in 1992. Wright'sF statistics showed no significant departure from random mating among stable flies. It was concluded that gene flow compensates for any local differentiation in stable fly populations. 相似文献
4.
5.
A. Acou † T. Robinet ‡ E. Lance § C. Gerard § B. Mounaix L. Brient § B. Le Rouzic § E. Feunteun ‡ 《Journal of fish biology》2008,72(3):753-762
Thirty migrating silver eels Anguilla anguilla were collected in a river system where algal blooms occurred yearly. Fifty per cent of eel livers were contaminated by microcystin-LR (mean ± s . d . toxin level: 28·1 ± 22·4 ng g−1 ). Contaminated silver ( v. healthy) eels had lower fish condition. Consequences of this impact for the breeding potential of these migrating eels are discussed. 相似文献
6.
《Ethology, Ecology and Evolution》2012,24(2):179-190
A population of migratory Buzzards Buteo buteo breeding in the pristine deciduous forests ol the Białowieża National Park (eastern Poland) was studied in 1986–1989. Bleeding densities were 4.5–5.2 pairs/10 km2. Mean clutch size was 2.4 eggs (n = 22), from which 1.9 young hatched, and 1.3 juveniles fledged per breeding pair. Breeding performance of pairs with territories located near the forest edge was positively correlated with the cyclic abundance of Microtus spp. in the open river valley and meadows. During the breeding season Buzzards fed primarily on birds (42–75% of prey biomass), rodents (10–26%), and moles (7– 23%). Variation in the proportion of rodents in the diet during May-July was not related lo the changes in either Microtus or Clethrionomys and Apodemus numbers. From the bird community living in the Białowieża National Park, Buzzards selectively preyed on medium-sized birds, particularly Turdus philomelos and woodpeckers, and neglected very numerous small passerines. At least 40% of the birds taken by Buzzards were juveniles or fledglings. 相似文献
7.
Herbicide-resistant Indica rice plants from IRRI breeding line IR72 after PEG-mediated transformation of protoplasts 总被引:9,自引:0,他引:9
Swapan K. Datta Karabi Datta Nouchine Soltanifar Gunter Donn Ingo Potrykus 《Plant molecular biology》1992,20(4):619-629
The commercially important Indica rice cultivar Oryza sativa cv. IR72 has been transformed using direct gene transfer to protoplasts. PEG-mediated transformation was done with two plasmid constructs containing either a CaMV 35S promoter/HPH chimaeric gene conferring resistance to hygromycin (Hg) or a CaMV 35S promoter/BAR chimaeric gene conferring resistance to a commercial herbicide (Basta) containing phosphinothricin (PPT). We have obtained so far 92 Hgr and 170 PPTr IR72 plants from protoplasts through selection. 31 Hgr and 70 PPTr plants are being grown in the greenhouse to maturity. Data from Southern analysis and enzyme assays proved that the transgene was stably integrated into the host genome and expressed. Transgenic plants showed complete resistance to high doses of the commercial formulations of PPT. 相似文献
8.
The Raggiana Bird-of-paradise (Paradisaea raggiana) has been held by the San Diego Zoo for more than 50 years, but the population remained in low numbers until the mid-1990s. A previous article published in 1997 documented the beginning of the rise in the population; however, no new information has been published since that time. Over the past 25 years, behavioral observations by animal staff have led to improvements in husbandry techniques, which includes artificial incubation of eggs and hand-rearing of chicks. The ability to simulate a lek with various housing arrangements, in which the males can display with each other, be given access to a female for copulation, and then be separated again has proven paramount for breeding success. Additionally, females are allowed mate choice, further mimicking natural behaviors observed by this species. The refinement of these methods has led to a greater number of fertile eggs as well as higher hatchability and survivability, which in turn has resulted in a significant increase in the captive population. 相似文献
9.
JEROEN C. S. CREUWELS JAN A. VAN FRANEKER SUSAN J. DOUST ANNA BEINSSEN BELINDA HARDING & OLIVER HENTSCHEL 《Ibis》2008,150(1):160-171
Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but Antarctic Petrels Thalassoica antarctica bred up to 16 days earlier than Southern Fulmars. During the pre-laying exodus, all Antarctic Petrels deserted the colony, whereas some Southern Fulmars Fulmarus glacialoides remained. Antarctic Petrels exhibited stronger synchronization in breeding, made longer foraging trips and spent less time guarding their chicks than Southern Fulmars. Overall breeding success of both species was similar but failures of Antarctic Petrels were concentrated in the early egg-phase and after hatching, when parents ceased guarding. Southern Fulmars lost eggs and chicks later in the breeding cycle and so wasted more parental investment in failed breeding attempts. Different breeding strategies may be imposed by flight characteristics; Southern Fulmars are less capable of crossing large expanses of pack ice and need to delay breeding until the sea ice retreats and breaks up. However, due to the short summer they risk chick failure when weather conditions deteriorate late in the season. 相似文献
10.
Capsule We report on the courtship behaviour of the Eurasian Bittern from direct observation in rice fields. 相似文献