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981.
982.
以108国道凉山境高速公路Vb合同段为例,针对高边坡的复杂地质条件,采用传递系数法和毕晓普法进行稳定性分析,从而不同的高边坡采用不同的防护设计。 相似文献
983.
Phenotypic (rp), genotypic (rg), genotype × location (rgl) and error (re)correlations for important agronomic characters were estimated for eleven Norwegian populations of white clover (Trifolium repens L.), originating from between 58°52′N and 69°30′N latitude, and from altitudes of 10 to 450 m a.s.l. The populations were evaluated in monoculture clonal field plots for
two years at two locations in Norway. All pairwise correlations between foliage height, leaflet length, dry matter yield (DMY)
and general performance were positive and significant. Winter survival was positively correlated with general performance,
spring growth and DMY, but negatively associated with internode length, while seed yield showed a small positive genotypic
correlation with foliage height. Considerable differences were, however, revealed among populations with regard to sign and
magnitude of the estimated correlations. Within-population estimates of rg were consistently positive between DMY, general performance and most other characters; between foliage height on the one
hand and leaflet length, winter survival and seed yield on the other hand, and between internode length and leaflet length,
indicating pleiotropy. Correlations involving other character-combinations varied substantially among populations, and imply
presence of linkage and/or coadaptation. Path coefficient analysis was used to partition the genotypic correlations between
some of the characters into direct and indirect effects. Path coefficients revealed that foliage height had the highest positive
direct effect on DMY, followed by winter survival and internode length. Leaflet length, which showed a positive, significant
simple correlation with DMY, exhibited a negligible direct influence, counterbalanced nearly completely by the positive indirect
effect on DMY via foliage height. Positive indirect effects on DMY via foliage height were also found for winter survival
and internode length. The coastal populations from North and Middle Norway, and a southern highland population showed the
largest expected responses to phenotypic selection for most of the characters. The results demonstrate that there is enough
genetic variation in adapted local populations to develop new improved cultivars adapted to high-latitude environments that
combine upright growth habit with sufficient winter-hardiness and persistency.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
984.
985.
CO_2浓度增加对C_3、C_4作物生理特性影响的实验研究 总被引:2,自引:1,他引:1
通过对 C3小麦、大豆、大白菜和 C4 玉米在不同 CO2 浓度 ( 350× 10 -5、 50 0× 10 -6、 60 0×10 -6、 70 0× 10 -6)条件下的生长模拟实验和生理特性研究表明 ,CO2 浓度增加 ,促使作物光合速率增长 ,光合时间略有延长 ,光补偿点明显下降 ,蒸腾系数减小 ,叶气温差增大 ,叶温升高。 70 0× 10 -6和50 0× 10 -6比 350× 10 -6小麦光合速率分别增长 30 .7%和 11.7% ,大豆增长 63.4 %和 4 2 .7% ,大白菜增长 68.0 %和 39.0 % ,玉米增长 15.7%和 4 .7% ,C3作物比 C4 反应明显 ;蒸腾系数小麦下降 14.3%和 7.7% ,大白菜下降 2 7.1%和 2 3.1% ,玉米下降 16.8%和 10 .4 % 相似文献
986.
987.
Recently, riparian forests have attracted attention as they are effective for ecological preservation and landscape enhancement.
Uses of such forests in flood prevention, sediment control, and erosion control works have been actively promoted. This study
aims to clarify the effect of density of riparian trees on drag exerted on trees along river channels under the regime of
bed load transport. Hydraulic model experiments were performed using a straight channel, and the methods to calculate the
drag coefficient necessary for deriving drag exerted on trees were studied. Previous studies have stated that the drag coefficient
of a cylinder is fairly constant when Reynolds number,R
e, is between 103 and 105 (e.g., Schlichting, 1979). This study clarified, however, that in cases of relatively dense arrangements of model trees (cylinders),
the drag coefficient varies greatly with the density of the trees. As such, correlation between the drag coefficient and Reynolds
number was found to be slight. Test results indicated that the drag coefficient of trees,C
d, correlates strongly with the coefficient of velocity,U′/U
*
′, friction factor of the channel bed,f′, and roughness concentration of trees × flow depth,aH′ or ratio of the area occupied by trees,λ. Furthermore, the drag coefficient,C
d, was also found to be slightly correlated with the gradient of the channel bed,I. Equations using either of the following parameters were obtained for deriving the drag coefficient,C
d, based on the experiment results:aH′; λ; U′/U
*
′; and Froude numberF
r. These equations allow fairly accurate calculation of drag exerted on trees. 相似文献
988.
天山北坡平原区水面蒸发的实验研究 总被引:14,自引:0,他引:14
本文以新疆地勘局昌吉地下水均衡试验场20m63水面蒸发池水面蒸发量及常规气象观测资料为基础,应用灰色关联分析方法分析了各气象要素对水面蒸发量的影响程度,给出了E601蒸发四和Φ20蒸发器水面蒸发折算系数,建立了计算水面蒸发量的经验公式。 相似文献
989.
990.
Nine horizon samples of three soil profiles representative of Dystri-gelic Cambisol, Fibri-gelic Histosol and Relic Ornithosol were taken from Fildes Peninsula of King George Island, South Shetland Islands to quantitatively demonstrate the enrichment, migration and loss of the elements (Si, Al, Fe, Ca, Mg, Mn, K, Na and P) in soil horizons and their behaviour within profiles by application of the enrichment coefficient calculated in terms of the abundance of Ti. Six horizon samples of 4 other profiles randomly taken from the studied area were examined for calculation of the redistributing enrichment coefficient, which was applied for a better understanding of the element redistribution between soil and clay fraction along with soil development. The results showed that the enrichment, migration and redistribution of the elements varied strongly among the investigated soils and horizons, due to the differences of weathering degrees and moisture status, influences of sea bird activities, etc. 相似文献