全文获取类型
收费全文 | 173篇 |
免费 | 0篇 |
出版年
2013年 | 4篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 10篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 9篇 |
2006年 | 2篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 1篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 16篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1951年 | 4篇 |
1950年 | 2篇 |
排序方式: 共有173条查询结果,搜索用时 31 毫秒
41.
ANDERS MARTINSSON 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1976,9(4):459-462
The two large organizations in international geology, the permanent International Union of Geological Sciences (IUGS) and the long-term International Geological Correlation Programme (IGCP), are strongly stratified units and victims of platform sedimentation. Their National Committees and corresponding bodies are often useless as channels of the active scientists' initiative and influence. Their constituent and affiliated scientific bodies are deprived of all influence on the management of the organizations, in favour of managements bureaucratically and autocratically recruited according to a pattern of equitable geographical distribution. The IGCP is wasting effort in hunting for programme gaps, whilst both organizations are campaigning against regional concentrations of interest and consequent influence. Both organizations are in bad need of activating their national members and opening up their management to influence from their scientific bodies. For this purpose important changes in their constitutions are needed. Only then can their formal strength become real and their many challenging tasks be efficiently tackled. 相似文献
42.
43.
ANDERS WAREN 《Zoologica scripta》1980,9(1-4):283-306
Eleven new genera and 17 species are described, with one exception parasites on echinoderms: Trochostilifer gen. n. with T. domus sp.n. (type species) (Philippines) on Stylocidaris efftuens, T. mortenseni sp.n. (New Caledonia) on Prionocidaris australis and T. slriatus (Hedley) on P. baculosa annulifera; Ophioarachnicola biformis gen. et sp.n. (Solomon Is.) on Ophio-arachna incrassata; Hemiliostraca sloani sp.n. (Aldabra I.) on Ophiomyxa australis; Robil-lardia solida sp.n. (Loyalty Is.), host unknown. Ersilia Monterosato is transferred from Lacunidae to Eulimidae, E. stancyki sp.n. (Florida) is a parasite of Ophiolepis elegans. Hyper-mastus echinodisci sp.n. and H. sauliae sp.n. (both Borneo) are parasitic on Echinodiscus bisperforatus; Monogamus parasaleniae sp.n. (Tonga I.) on Parasalenia gratiosa. Scalari-balcis gen.n. is erected for Mucronalia angulata Mandahl-Barth. Concavibalcis scalaris gen. et sp.n. is described from the Philippines, host unknown. Echiuroidicola cicatricosa gen. et sp.n. (Malaysia) is a parasite on the echiuroid Ochetostoma erythrogrammon. Peasistilifer gen.n. (type species Mucronalia nitidula Pease) is erected for a group of holothurian parasites. Prostilifer gen.n. is erected for Eulima subpellucida Pease, parasitic on Pacific holo-thurians. Paramegadenus scutellicola sp.n. (Pacific) is parasitic on Stellaster incei, P. incerta sp.n. on an Australian starfish. Asterolamia hians gen. et sp.n. is described from Astropecten indicus and A. cingulata from Craspidaster hesperus , both Pacific. Microstilifer gen.n. is erected for Stilifer auricula Hedley. Vitreobalcis gen.n. is erected for Apicalia holdsworthi H. Adams, a parasite of Mespilia globulus and V. laevis sp.n. (from Synaptula purpurea , Australia) is provisionally placed here. Luetzenia asthenosomae gen. et sp.n. (Australia) and L. toki Habe are both parasites on Asthenosoma. 相似文献
44.
FRED W. STAUFFER ANDERS BARFOD PETER K. ENDRESS 《Botanical journal of the Linnean Society. Linnean Society of London》2009,161(1):66-77
The structure and late development of the flowers of the South‐East Asian bee‐pollinated palm Licuala peltata are described with special focus on the architecture of the unusual labyrinthine nectaries. The nectaries are derived from septal nectaries by extensive convolution of the carpel flank surfaces below the ovary throughout the inner floral base, thus also encompassing the inner surface of the corolla–androecium tube. A comparison with septal nectaries elsewhere in Arecaceae and with labyrinthine nectaries in other monocots shows that labyrinthine nectaries situated below the ovary, as described here, are not known from any other palms, but are similar to those of a few Bromeliaceae and, less strongly convoluted, some Haemodoraceae and Xanthorrhoeaceae. In addition, the substantial participation of parts other than the gynoecium in the nectary architecture of Licuala appears unique at the level of monocots. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 66–77. 相似文献
45.
Storms can cause Europe-wide reduction in forest carbon sink 总被引:1,自引:0,他引:1
ANDERS LINDROTH FREDRIK LAGERGREN ACHIM GRELLE† LEIF KLEMEDTSSON‡ OLA LANGVALL§ PER WESLIEN‡ JANNO TUULIK 《Global Change Biology》2009,15(2):346-355
Disturbance of ecosystems is a major factor in regional carbon budgets, and it is believed to be partly responsible for the large inter-annual variability of the terrestrial part of the carbon balance. Forest fires have so far been considered as the most important disturbance but also other forms of disturbance such as insect outbreaks or wind-throw might contribute significantly to the largely unexplained inter-annual variability, at least in specific regions. The effect of wind-throw has not yet been estimated because of lack of data on how carbon fluxes are affected. The Gudrun storm, which hit Sweden in January 2005, resulted in ca. 66 million m3 of wind-thrown stem wood on an area of ca. 272 000 ha. Using a model (BIOME-BGC) calibrated to CO2 flux measurements at two sites, the annual net ecosystem productivity during the first year after the storm was estimated to be in the range −897 to −1259 g C m−2 yr−1 . This is a much higher loss compared with harvested (clear-cut) forests in Europe, which ranged between ca. −420 and −100 g m−2 yr−1 . The reduction in the carbon sink scaled to the whole wind-thrown area was estimated at ca. 3 million tons C during the first year. By historical data on wind-throw in Europe combined with modelling, we estimated that the large Lothar storm in 1999 reduced the European carbon balance by ca. 16 million tons C, this is ca. 30% of the net biome production in Europe. We conclude that the impact of increased forest damage by more frequent storms in future climate change scenarios must be considered and that intermittent large wind-throw events may explain a part of the large inter-annual variability in the terrestrial carbon sink. 相似文献
46.
PAULA F. CAMPOS TOMMY KRISTENSEN LUDOVIC ORLANDO ANDREI SHER MARINA V. KHOLODOVA ANDERS GÖTHERSTRÖM MICHAEL HOFREITER DOROTHÉE G. DRUCKER PAVEL KOSINTSEV ALEXEI TIKHONOV GENNADY. F. BARYSHNIKOV ESKE WILLERSLEV M. THOMAS P. GILBERT 《Molecular ecology》2010,19(22):4863-4875
Prior to the Holocene, the range of the saiga antelope (Saiga tatarica) spanned from France to the Northwest Territories of Canada. Although its distribution subsequently contracted to the steppes of Central Asia, historical records indicate that it remained extremely abundant until the end of the Soviet Union, after which its populations were reduced by over 95%. We have analysed the mitochondrial control region sequence variation of 27 ancient and 38 modern specimens, to assay how the species’ genetic diversity has changed since the Pleistocene. Phylogenetic analyses reveal the existence of two well‐supported, and clearly distinct, clades of saiga. The first, spanning a time range from >49 500 14C ybp to the present, comprises all the modern specimens and ancient samples from the Northern Urals, Middle Urals and Northeast Yakutia. The second clade is exclusive to the Northern Urals and includes samples dating from between 40 400 to 10 250 14C ybp. Current genetic diversity is much lower than that present during the Pleistocene, an observation that data modelling using serial coalescent indicates cannot be explained by genetic drift in a population of constant size. Approximate Bayesian Computation analyses show the observed data is more compatible with a drastic population size reduction (c. 66–77%) following either a demographic bottleneck in the course of the Holocene or late Pleistocene, or a geographic fragmentation (followed by local extinction of one subpopulation) at the Holocene/Pleistocene transition. 相似文献
47.
48.
ANDERS ERICSSON 《Physiologia plantarum》1979,45(2):270-280
The effects of fertilization, irrigation or both on the seasonal changes of starch and soluble carbohydrates (glucose, fructose, myo-inositol, pinitol and sucrose) in needles of 20-year-old Scots pine trees (Pinus silvestris L.) were studied during three consecutive years. The starch content of the mature needles increased during spring and early summer to about 25% of dry weight. Neither fertilization nor irrigation affected the general pattern of starch accumulation during the spring. The starch reserves were mobilized when the shoot started to grow. Starch content decreased more rapidly in needles from fertilized than in those from unfertilized trees. The current needles from the control trees accumulated starch while they were still growing. The current needles of the fertilized trees did so to a lesser extent. The amount of starch was closely correlated to the air temperature and to the growth rate. Large amounts were found at low temperatures and low growth rates. The concentrations of soluble carbohydrates showed the well-known seasonal variation, with the highest value during the winter. The levels of sugars were nearly similar, irrespective of fertilization. An exception was sucrose, which was found in small quantities in needles from fertilized plots. Small amounts of sucrose were also found in growing current needles. The results are discussed in relation to growth limitation by assimilate availability and indicate that the ‘sink demand’ is the limiting factor. 相似文献
49.
50.