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21.
Summary The root systems ofEucalyptus grandis W. Hill ex Maiden, irrigated with recycled municipal effluent at two sites in north-western Victoria, Australia, were studied
by excavation and coring. Trees at Robinvale were four years-old and were irrigated using micro-sprays that covered only 70%
of the ground surface area, whereas at Mildura, effuent was uniformly was uniformly applied to six years-old trees by flood
and sprinkler irrigation.
At Mildura where roots were excavated from a 2.80×2.80×1.20 m block of soil, a total root length of 1193 m.m−2 and a total root weight of 3.1 kg m−2 were estimated in the top metre. For roots >1 mm diameter, 77% of intercepts were at 0–30 cm, whereas only 50% were in the
50–100 cm soil horizon.
At both sites where roots in the top 30 cm were studied by coring, the vertical distributions of root intercepts, length and
weight were similar. Root length was greatest in the 0–10 cm soil horizon at both sites, and intercepts of roots <1 mm diameter
comprised 73% and 81% of all roots at Mildura and Robinvale respectively. Roots <1 mm diameter contributed 85% of total length
at both sites, but only 19% and 21% of total weight at Mildura and Robinvale respectively. The horizontal distribution of
roots differed at the two sites. With uniform application of effuent at Mildura, root intercepts and length were concentrated
in the centre of the irrigation bay, but at Robinvale, the concentration occurred closer to the tree row due mainly to the
different method of irrigation. Root weight at both sites was highest within 50 cm of the tree row.
Root densities of 0.11 to 0.57 cm cm−3 were estimated in the two plantations; these were similar to root densities measured inPinus radiata D. Don plantations up to 46 months old, but were considerably lower than those estimated for pastures. The implications of
the results for the management of irrigated plantations of eucalypts are discussed. 相似文献
22.
Endosymbiotic origin and codon bias of the nuclear gene for chloroplast glyceraldehyde-3-phosphate dehydrogenase from maize 总被引:19,自引:0,他引:19
Henner Brinkmann Pascal Martinez Françoise Quigley William Martin Rüdiger Cerff 《Journal of molecular evolution》1987,26(4):320-328
Summary The nuclei of plant cells harbor genes for two types of glyceraldehyde-3-phosphate dehydrogenases (GAPDH) displaying a sequence divergence corresponding to the prokaryote/eukaryote separation. This strongly supports the endosymbiotic theory of chloroplast evolution and in particular the gene transfer hypothesis suggesting that the gene for the chloroplast enzyme, initially located in the genome of the endosymbiotic chloroplast progenitor, was transferred during the course of evolution into the nuclear genome of the endosymbiotic host. Codon usage in the gene for chloroplast GAPDH of maize is radically different from that employed by present-day chloroplasts and from that of the cytosolic (glycolytic) enzyme from the same cell. This reveals the presence of subcellular selective pressures which appear to be involved in the optimization of gene expression in the economically important graminaceous monocots. 相似文献
23.
Takakazu Yumoto 《Ecological Research》1987,2(2):133-145
Animal pollination in a warm temperate evergreen broad-leaved forest was observed on Yaku-shima Island, south of Kyushu, Japan.
Three groups of plants were categorized: canopy-flowering tree species, understory-flowering tree species, and climber and
epiphyte species. Each of these formed different pollination systems. The canopy-flowering tree species had shallow, dish-shaped
flowers and utilized various types of opportunistic pollinators. Most of the climber and epiphyte species had deep, tube-shaped
flowers and specialized pollinators, although some climber species which bloomed in the canopy especially in winter, had opportunistic
pollinators. The understory-flowering tree species had large dish- or funnel-shaped flowers and endothermic pollinators able
to tolerate the dark and cold conditions under the canopy. The individual trees of canopy-flowering tree species produced
large numbers of flowers simultaneously (mass-flowering) and had a well synchronized flowering period. Each canopy-flowering
tree species segregated its flowering time from those of the anothers. Climber and epiphyte species and most of the understory-flowering
tree species produced small numbers of flowers sequentially (extended flowering) and showed a long flowering period. 相似文献
24.
Multiple shoot formation and their elongation from excised apical vegetative shoots of a 40-year old-tree ofMitragyna parvifolia Korth. was achieved in Murashige and Skoog's medium supplemented with 4.44 M benzyl adenine. The in vitro regenerated shoots rooted when cultured on modified Murashige and Skoog's medium containing low inorganic salts and the three auxins. Regeneration by this method was suitable for mass propagation of the plant. 相似文献
25.
A flexible method to align large numbers of biological sequences 总被引:5,自引:0,他引:5
William R. Taylor 《Journal of molecular evolution》1988,28(1-2):161-169
Summary A method for the alignment of two or more biological sequences is described. The method is a direct extension of the method of Taylor (1987) incorporating a consensus sequence approach and allows considerable freedom in the control of the clustering of the sequences. At one extreme this is equivalent to the earlier method (Taylor 1987), whereas at the other, the clustering approaches the binary method of Feng and Doolittle (1987). Such freedom allows the program to be adapted to particular problems, which has the important advantage of resulting in considerable savings in computer time, allowing very large problems to be tackled. Besides a detailed analysis of the alignment of the cytochrome c superfamily, the clustering and alignment of the PIR sequence data bank (3500 sequences approx.) is described. 相似文献
26.
Leaf senescence and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBP carboxylase, EC 4.1.1.39) degradation in orange [ Citrus sinensis (L.) Osbeck cv. Washington Navel] explants have been investigated. Explants consisted of a segment of stem (ca 15 cm) and 5 mature leaves. In vitro RuBP carboxylase degradation was determined by culturing the explants in water for different periods of time (3 days usually) and quantifying the two RuBP carboxylase subunits in the extracts following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In vitro RuBP carboxylase degradation was estimated by autodigestion of leaf extracts and SDS-PAGE. The extent of in vivo RuBP carboxylase degradation in explants cultured under 16 h light/8 h dark photoperiod varied throughout the year and showed a cyclic behaviour correlated with the growth cycle of Citrus. The highest proteolytic activity both in vivo and in vitro was found in explants made from April to August coinciding with the maximum vegetative growth period of the tree.
Leaf senescence and abscission could be retarded significantly at any time of the year by maintaining the explants continuously in the dark. Treatment of the explants in the dark with a continuous flow of ethylene enhanced both leaf abscission and rate of RuBP carboxylase degradation, proportionally to ethylene concentration (0.1-0.6 ppm). Ethylene-induced senescence of Citrus leaf explants in the dark appears to be a convenient model system to study the regulation of the proteolytic degradation of RuBP carboxylase. 相似文献
Leaf senescence and abscission could be retarded significantly at any time of the year by maintaining the explants continuously in the dark. Treatment of the explants in the dark with a continuous flow of ethylene enhanced both leaf abscission and rate of RuBP carboxylase degradation, proportionally to ethylene concentration (0.1-0.6 ppm). Ethylene-induced senescence of Citrus leaf explants in the dark appears to be a convenient model system to study the regulation of the proteolytic degradation of RuBP carboxylase. 相似文献
27.
R. Habib 《Plant and Soil》1988,108(2):267-274
A method is proposed for estimating the total length of a root system from sub-samples. This method is based on the measurement
of the length and diameter of small pieces of roots, and on the measurements of the bulk density of root sub-samples. It is
assumed that roots are cylinders with a given bulk density. The length and diameter of small root pieces are measured by image
analysis. A weighted quadratic mean (W.Q.M.) root diameter is then calculated and used in estimating the root length. This
W.Q.M. diameter is defined as the real mean diameter of an equivalent single root with the same length and volume as the tested
root system. The accuracy of prediction is demonstrated for one theoretical root system. The standard deviation of estimation
can be calculated using sampling simulations. 相似文献
28.
K. M. Song T. C. Osborn P. H. Williams 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1988,76(4):593-600
Summary Preliminary analysis using nuclear RFLPs provided evidence that subspecies within Brassica rapa originated from two different centers. One center is in Europe, represented by turnip and turnip rape from which the oilseed sarson was derived. A second center is in South China containing a variety of Chinese vegetables of which pak choi and narinosa seem to be the most ancient forms. Based on RFLP data, the accessions of B. oleracea examined could be divided into three distinct groups, represented by thousand head kale, broccoli and cabbage. Thousand head kale and Chinese kale appear to be the primitive types. Observations of parallel variation among subspecies of both species are discussed. 相似文献
29.
30.
图论在中国慈姑属数量分类研究中的应用 总被引:1,自引:0,他引:1
.黄德世;.钟扬;.陈家宽 《武汉植物学研究》1988,6(4):405-406
慈姑属(Sagittaria L.)是水生单子叶植物泽泻科(Alismataceae)的一个重要属。近年来,陈家宽等对中国慈姑属进行了系统研究。作者应用聚类分析和主成分分析进行了中国慈姑属的数量分类,取得了良好的效果。由于慈姑属分类性状数目较大,因而在压缩后的三维空间中描述分类群间的距离, 相似文献