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61.
Axillary bud banks of two semiarid perennial grasses: occurrence, longevity, and contribution to population persistence 总被引:4,自引:0,他引:4
The occurrence, longevity, and contribution of axillary bud banks to population maintenance were investigated in a late-seral
perennial grass, Bouteloua curtipendula, and a mid-seral perennial grass, Hilaria belangeri, in a semiarid oak-juniper savanna. Axillary buds of both species were evaluated over a 2-year period in communities with
contrasting histories of grazing by domestic herbivores. A double staining procedure utilizing triphenyl tetrazolium chloride
and Evan's blue indicated that both viable and dormant axillary buds remained attached to the base of reproductive parental
tillers for 18–24 months which exceeded parental tiller longevity by approximately 12 months. Bud longevity of the late-seral
species, B. curtipendula, exceeded bud longevity of the mid-seral species, H. belangeri, by approximately 6 months. Younger buds located on the distal portion of the tiller base were 3.2 and 1.4 times more likely
to grow out than older proximal buds of B. curtipendula and H. belangeri, respectively. The percentage of older proximal buds, which included comparable portions of viable and dormant buds, that
grew out to produce tillers following mortality of parental tillers was 6.0% for B. curtipendula and 8.4% for H. belangeri. In spite of the occurrence of relative large axillary bud banks for both species, the magnitude of proximal bud growth did
not appear sufficient to maintain viable tiller populations. We found no evidence to support the hypothesis of compensatory
bud growth on an individual tiller basis for either species. Grazing history of the communities from which the buds were collected
did not substantially affect the number, status, longevity, or outgrowth of axillary buds on an individual tiller basis for
either species. However, long-term grazing by domestic herbivores influenced axillary bud availability by modifying population
structure of these two species. Bud number per square meter for B. curtipendula was 25% lower in the long-term grazed compared to the long-term ungrazed community based on a reduction in both tiller number
per plant and plant number per square meter. In contrast, bud number per square meter for H. belangeri was 190% greater in the long-term grazed than in the long-term ungrazed community based on a large increase in plant density
per square meter. Minimal contributions of axillary bud banks to annual maintenance of tiller populations in this mid- and
late-seral species underscores the ecological importance of consistent tiller recruitment from recently developed axillary
buds. Consistent tiller recruitment in grasslands and savannas characterized by intensive grazing and periodic drought implies
that (1) bud differentiation and maturation must be remarkably tolerant of adverse environmental conditions and/or (2) tiller
recruitment may resume from buds that mature following the cessation of severe drought and/or grazing, rather than from mature
buds that survive these disturbances. These scenarios warrant additional research emphasis given the critical importance of
this demographic process to tiller replacement in species populations and the maintenance of relative species abundance in
grasslands and savannas.
Received: 12 August 1996 / Accepted: 30 December 1996 相似文献
62.
63.
To clarify the timing of the differentiation of the first and second inflorescences in strawberry (Fragaria × ananassa Duch.), morphological changes on shoot apices during short day and low night temperature treatments were observed by scanning electron microscopy (SEM) and optical microscopy. Axillary buds just below the first inflorescence (axillary bud 1) became visible when sepal primordia of the primary flower were differentiated. By this time, other axillary buds had already developed. Axillary bud 1 developed four leaf primordia, and then a differentiated inflorescence at its summit. The phase transition of shoot apices from the vegetative to the reproductive phase may therefore trigger the differentiation of axillary bud 1 which is destined to develop into extension crowns. 相似文献
64.
介绍了植物茎尖和芽超低温保存的意义和现状。影响超低温保存的一些主要因素及其所采取的措施,主要包括预培养、低温锻炼、使用冰冻保护剂以及适当采用不同的降温方法和化冻洗涤方法,并就今后的研究提出了一些看法。 相似文献
65.
The sectioned thin cell layers (TCL) of flower stalk of Cichorium intybus L. were cultured in MS medium supplemented with NAA and BA or IAA and BA where floral and vegetative buds were developed from the explant. Endogenous IAA, DHZ+DHZR, iPA increased significantly during the floral bud formation, while Z+ZR remained changed. The levels of cytokinins, DHZ +DHZR, iPA, and Z-f-ZR all increased significantly during the vegetative bud formation, however IAA level was reduced during the first 7 days of culture and increased to two-thirds of initial values on the day when the bud primordia were formed. The results suggested that the initiation of floral buds was associated with a high IAA/CTK ratio, whereas the induction of vegetative bud differentiation was related to a low IAA/CTK ratio. 相似文献
66.
67.
杜仲雌雄株细胞学,顶芽及叶含胶量的比较 总被引:14,自引:0,他引:14
杜仲(EucommiaulmoidesOliv.)为严格的雌雄异株植物,其雌雄株的比例近似于1:1,说明其性别可能由性染色体决定。但在形态上看不到特异的性染色体,雄株花粉母细胞整个减数分裂过程中,同源染色体的配对和分离是正常的。偶尔可发现个别细胞有染色体桥和环状或链状四价体。从1993年和1994年的12月到翌年4月芽完全展开前对顶芽的测量说明,雄株顶芽的长度和最大直径都明显大于雌株的(P<0.01),而整个生长季节中雌株叶子的杜仲胶含量却明显高于雄株的(P<0.01)。不管雄株还是雌株,其叶的含胶量都随季节变化和叶子的长大而降低。实践证明可用芽的大小鉴别杜仲幼株的性别。 相似文献
68.
诱导风信子再生花芽不断分化花被片的研究 总被引:8,自引:0,他引:8
通过外源激素及外植体年龄的控制,诱导风信子再生花芽不断分化花被片已经获得成功。在250d的继代培养中平均每个花芽可分化70多片花被片,最多的可分化140多片。对这种花芽不断分化花被片的形态发生过程以及生长发育特点的观察表明,花芽的第1轮器官与风信子野生型花基本相同,查花被,它由花被筒及其上部的裂片-花被片组成。 相似文献
69.
大野芋种子形成丛生芽的微繁殖 总被引:3,自引:0,他引:3
大野芋(Colocasiagigantea)的成熟种子(褐色)和未成熟的种子(淡黄色)在1/2MS培养基上均能萌发,种子萌发率最高达50%,种子没有休眠期。在室温下,种子在1/4MS 1%蔗糖培养基上,寿命约可达1年。种子在MS BA2mg·L-1 IAA0.25mg·L-1的培养基上,产生丛生芽。增值率1∶4/60d。生根培养基为MS NAA0.3mg·L-1,生根率达95%以上。通过诱导大野芋种子产生丛生芽,建成了快繁无性系,并成功地实现了种子的离体保存。本研究工作的完成,对于芋头的这一野生近缘种的保存和利用、芋头品种的改良,均具有较大意义。 相似文献
70.
J. Purkayastha T. Sugla A. Paul S. Solleti L. Sahoo 《In vitro cellular & developmental biology. Plant》2008,44(5):442-447
A rapid and efficient method for the large-scale propagation of a highly valuable medicinal plant, Andrographis paniculata Nees, through in vitro culture of nodal explants obtained from 15-d-old aseptic seedling has been developed. High frequency direct shoot proliferation
was induced in nodal explants cultured on Murashige and Skoog’s medium supplemented with 6-benzylaminopurine (BAP). Amongst
the various cytokinins tested (BAP, kinetin, thidiazuron and 2-isopentyl adenine), BAP proved to be the most effective. The
shoot forming capacity of the nodal explants was influenced by the BAP concentration (1–12.5 μM), and the optimal response
was observed at 10 μM BAP, which induced an average of 34 shoots in 94% of the cultures within 4 wk. Significant differences
were recorded in terms of average number of shoots per explant (8.6–34.1) among the different concentrations of BAP investigated.
Concentrations of all cytokinins tested reach a level that can be considered above the optimum level, as marked by a reduced
frequency of shoot proliferation. The multiple shoots obtained on various concentrations of BAP failed to elongate even after
transfer to hormone-free MS medium. Elongation of the induced shoots was achieved on MS basal medium supplemented with 1.0 μM
GA3 within 2 wk. A proliferating shoot culture was established by repeatedly subculturing the original nodal explants on shoot
multiplication medium after each harvest of the newly formed shoots. The explants retained their morphogenic potential even
after three harvests. Therefore, in 90 d, about 60–70 shoots were obtained from a single nodal explant and the nodal explants
from primary shoots further regenerated equivalent number of shoots, depicting their high frequency regeneration potential
in A. paniculata. Rooting was best induced in 94% of shoots cultured on MS medium supplemented with 2.5 μM indole-3-butyric acid (IBA), within
a wk. The plantlets were successfully transferred to soil after hardening with a 92% survival rate. The system is rapid: the
initiation of shoot buds to the transplanting of regenerants to soil is completed in 8–9 wk. 相似文献