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31.
In many German forest soils low base saturation of CEC in deeper soil layers was reported and acidic deposition is seen as
the major cause of these findings. To test this hypothesis we sampled 5 New Zealand forest soils from pristine beech (Nothofagus fusca, N. menziesii, N. solandri) sites under climatic and geological conditions comparable to higher elevations in Germany. The soils developed from granite
and greywacke. Soil samples were analyzed for pH and the exchangeable cations were extracted with 1M NH4Cl. The base saturation of all soil profiles was very low, even in deeper layers and was thus similar to the patterns found
in many German forest soils. The pH was generally higher in the New Zealand soils as compared to Germany. The reason for the
depletion of base cations in deeper soil layers of New Zealand forest soils is most likely the leaching of base cations with
HCO3
- resulting from the dissociation of carbonic acid in connection with high amounts of seepage. Thus, under high rainfall conditions,
the low base saturation found in deeper layers of forest soils cannot exclusively be attributed to the effects of acidic depositions
and land use. ei]Section editor: R F Huettl 相似文献
32.
Mike H. Jurke 《Primates; journal of primatology》1996,37(1):109-119
The fate of most nonhuman primate species is intimately related to man. The increasing encroachment on the natural habitat
has resulted in the decimation and even near extinction of some species. Along with this development, the basic concept in
many modern zoos has changed from one of merely display to self-perpetuating units. Primate research facilities are orienting
their research programs towards reproductive physiology and behavior in an effort to provide basic knowledge of reproduction
in these species. This increased emphasis in the area of reproductive biology and the various efforts to improve breeding
of these mostly endangered primates in captivity has stimulated the author to write this review. It represents an attempt
to provide the reader with basic background information relating to the endocrinology and behavior of reproduction in the
clawed New World monkeys as it exists at the time of publication.
The intermediate evolutionary position ofCallimico goeldii between the clawed New World monkeys and the ‘true New World monkeys’ and our relatively poor knowledge about reproduction
and behavior in this particular species fully justifies the focus on Goeldi’s monkey in this essay. This review is an attempt
to provide a brief history of previous studies but also the basis for research in the future. The current status of knowledge
of the small-bodied clawed monkeys is also discussed in an evolutionary context, with an emphasis on the different reproductive
strategies in this dynamic group of primates.
The outcome, not surprisingly, confirms the unique position ofCallimico goeldii in its social, ecological, and evolutionary environment. 相似文献
33.
34.
中国紫金牛属一新种 总被引:1,自引:1,他引:0
胡启明 《热带亚热带植物学报》1995,3(4):13-16
中国紫金牛属一新种胡启明(中国科学院华南植物研究所,广州510650)关键词紫金牛属;光萼紫金牛;新种ANEWSPECIESOFARDISIAFROMCHINA¥HuChiming(SouthChinaInstituteofBotany,Academ... 相似文献
35.
云南小孢发属地衣的分类 总被引:3,自引:0,他引:3
报道了云南小孢发属地衣13种,其中中国新记录种6个,它们是:喜马拉雅小孢发,尼泊尔小孢发,光滑小孢发,光亮小孢发,多叉小孢发,波氏小孢发,另外7种的形态及分布也在文中进行了讨论。 相似文献
36.
The distribution of the New Zealand flatworm (Artioposthia triangulata) in Scotland was surveyed between July 1991 and February 1993. There were 348 records from domestic gardens, 56 from botanic gardens, garden centres and nurseries, with only 13 from farms. Although most of the records came from around the major cities the flatworm was found to have become established throughout the Scottish mainland and some of the Islands, e.g. Bute, Gigha, Orkney and Skye. The impact of the flatworm on earthworm populations in agricultural land in Scotland was, as yet, found to be minimal but the fact that seven adjacent farms near Dunoon were infected suggested it could be spread from farm to farm and that in the West of Scotland it could become widespread in agricultural land. 相似文献
37.
武陵山地区鱼类寄生杆咽属线虫两新种 总被引:1,自引:0,他引:1
本文报道在武陵山地区的白甲鱼[(Varicorkinus(Onychostoma)simus(SauvageetDabry)]和沪溪直口峻(RectorisluxiensisWuetYao)中发现的两种杆咽属(Rhabdochona)线虫新种,定名为白甲鱼杆咽线虫,新种(RhabdOchonaonyrkostomisp.nov.)和短咽杆咽线虫,新种(RhabdOchonabrevichonasp.nov.),并对两新种进行了测量和详细的描述。 相似文献
38.
Parasites of all kinds affect the behaviour of their hosts, often making them more susceptible to predators. The associated
loss in expected future reproductive success of infected hosts will vary among individuals, with younger ones having more
lose than older ones. For this reason, young hosts would benefit more by opposing the effects of parasites than old ones.
In a laboratory study, the effects of the trematode Telogaster opisthorchis on the anti-predator responses of the upland bully (Gobiomorphus breviceps) and of the common river galaxias (Galaxias vulgaris) were examined in relation to fish age. In a bully population where parasites were very abundant, the magnitude of the fish's
anti-predator responses decreased as the number of parasites per fish increased, and this effect was significantly more pronounced
in age 2 + and, to a lesser extent, age 3 + fish than in age 1 + fish. In another bully population where parasites were 10
times less abundant, similar effects were noticeable but not significant, whereas no effects of parasites on the responses
of galaxiids to predators were apparent. Differences in the abundance of parasites and in their sites of infection in fish
may explain the variability among host populations or species. However, in the bully population with high parasite abundance,
parasitism has age-dependent effects on responses to predators, providing some support for the prediction that young fish
with high expected future reproductive success invest more energy into opposing the effects of parasites than do older fish. 相似文献
39.
Randall W. Myster 《Plant Ecology》1994,114(2):169-174
Because the fate of seeds is critical to understanding the invasion of old fields by trees, and plant litter is an important component defining the old field microsite of dispersed seeds, I investigated the effects of litter type (Solidago spp./goldenrod,Quercus spp./oak, mixed) and litter amount (100–800 g/m2) on tree seed germination and seedling emergence. I found that at all densities bothSolidago andQuercus litter greatly reduced emergence of the small-seeded, bird-dispersed species,Juniperus virginiana andCornus florida. For one of the large-seeded, mammal-dispersed species,Carya tomentosa, high densitySolidago litter and high density mixed litter treatments reduced emergence. For the other large-seeded species,Quercus rubra, the high density mixed litter treatment and all levels ofSolidago litter reduced emergence.Quercus seedlings emerged twice as often as the other three species in control pots without litter.Carya emerged before the other species but the high density oak treatment delayed the expansion of its cotyledons. My results suggest that litter may contribute to the slow rate of tree invasion and the low probability of tree establishment in old fields. However, old field litter studies taken together point to the difficulty in drawing general conclusions about any net effect of litter on old field tree establishment. 相似文献
40.