全文获取类型
收费全文 | 616篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
633篇 |
出版年
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 14篇 |
2009年 | 24篇 |
2008年 | 15篇 |
2007年 | 20篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 17篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 19篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 18篇 |
1973年 | 8篇 |
1972年 | 25篇 |
1971年 | 23篇 |
1970年 | 6篇 |
1968年 | 8篇 |
1966年 | 6篇 |
1958年 | 7篇 |
1957年 | 6篇 |
1956年 | 5篇 |
1953年 | 9篇 |
1952年 | 10篇 |
1913年 | 5篇 |
1908年 | 4篇 |
排序方式: 共有633条查询结果,搜索用时 15 毫秒
611.
EDWARD M. SCOLNICK WADE P. PARKS GEORGE J. TODARO STUART A. AARONSON 《Nature: New biology》1972,235(54):35-40
612.
D. G. GEORGE 《Freshwater Biology》1981,11(1):37-60
SUMMARY. The results of direct current measurements in the South Basin of Windermere are presented and related to wind history and horizontal variations in near-surface water temperature. Currents were measured by Lagrangian methods using drift-bottles and depth-specific drogues. Except when sudden calms followed strong winds, internal seiche movements had little effect on horizontal transport in the epilimnion. The most important factor governing mass water movement was direct wind forcing. Variations in wind speed accounted for 93% of the variation in near-surface current speed.
For wind speeds between 100 and 500 cm s−1 the wind factor (current speed/wind speed) decreased linearly with wind speed. At wind speeds above 500 cm s−1 the wind factor remained relatively constant around 1 %.
Coriolis effects deflected near-surface currents 4–38° to the right of the wind. The degree of deflection was strongly correlated with the relative depth DE / D * (where DE was the depth of the epilimnion and D * the depth of frictional resistance). The influence of the Coriolis force also produced pronounced rotations, with depth, of the wind-driven current. The circulation pattern within the epilimnion was broadly that of a distorted conveyor belt moving at some angle to the wind axis. The strength of the transverse circulation was greatest at low wind speeds with a deep thermocline.
Richardson-number calculations suggest that the thermocline generally acts as a low-friction boundary between a turbulent epilimnion and a relatively quiescent hypolimnion. Horizontal variations in water temperature, although ranging from only 0.2 to 1.0°C per km, served as a good indirect 'tracer' of the circulation pattern. 相似文献
For wind speeds between 100 and 500 cm s
Coriolis effects deflected near-surface currents 4–38° to the right of the wind. The degree of deflection was strongly correlated with the relative depth D
Richardson-number calculations suggest that the thermocline generally acts as a low-friction boundary between a turbulent epilimnion and a relatively quiescent hypolimnion. Horizontal variations in water temperature, although ranging from only 0.2 to 1.0°C per km, served as a good indirect 'tracer' of the circulation pattern. 相似文献
613.
RUTH ATKINSON KWITON JONG GEORGE ARGENT 《Botanical journal of the Linnean Society. Linnean Society of London》1995,117(3):135-145
Chromosome numbers are reported for 36 accessions representing 31 species from nine genera of the tribe Vaccinieae, family Ericaceae. The plants are tropical and come from Southeast Asia and Central and South America. The taxonomy of the tribe is outlined in these regions. Genera are often poorly defined and taxa were chosen to reflect the range of variation of the Vaccinieae. Most Southeast Asian Vaccinium species were diploid (2 n = 24) as were those of Agapetes subgenus Agapetes (apart from the Himalayan A. flava ), Agapetes scortechinii and Costera endertii. All other accessions were found to be polyploid. The correlation between polyploidy, geographical distribution and the possession of an 'anatomical complex' of the leaf and stem in Vaccinieae of New Guinea and the neotropics is discussed. 相似文献
614.
615.
616.
GEORGE SICHUK MAN HEI SHIU RONALD W. CSURNY JOSEPH G. FORTNER 《Nature: New biology》1971,231(22):151-152
THIS report describes a positive correlation between sequential serum concentrations of EγG and the dosage schedule of equine anti-dog-lymphocyte globulin (EADLG) in dogs in which tolerance was induced by pretreatment with ultra-centrifuged EγG (tolerogen). This was in marked contrast to results in dogs which were not pretreated with tolerogen. 相似文献
617.
618.
619.
Use of canonical analysis in time series model identification 总被引:1,自引:0,他引:1
620.
A total of 41,099 insect specimens of 133 families and 492 morphospecies were collected from 31 trees of six species of Acacia in north-east Tanzania, representing one of the largest insect samples ever analysed from a tropical savannah habitat. Herbivores (sapsuckers and chewers) and parasitoids had the highest diversity shares, whereas the highest biomass shares were obtained by phytophagous chewers, ants and predators. The percentage biomass of ants was correlated positively with the diversity share of sapsuckers and negatively with the diversity share of tourists. A positive correlation was found with the residual biomass share of phytophagous sapsuckers, indicating a protective function of ants for this guild. Diversity and abundance share was much higher in egg and coccoid parasitoids compared to larval parasitoids, probably due to predation by ants on larval parasitoids. Their low diversity supports the hypothesis of a decline towards the equator in ichneumonid diversity. 相似文献