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991.
992.
马加拉山国家公园自建立以来,在自然环境保护方面面临着一些问题。园内住民向来使用药用植物治疗各种疾病,长期依赖周围的植物资源提供食品、房舍、饲料、保健品和其他人文生活的需要。然而,工业化的兴起以及随之而来的人们生活方式的改变,使得利用当地植物作医药的情况不断减少。因此,有必要进行民族植物学研究,把本土植物的利用信息在丧失之前记录下来。调查结果表明,AsparagusadescendensRoxb.,BerberislyciumRoyle(柯杞小檗)和ViolacanescenceWal.exRoxb.只能少量采集,AcaciamodestaWal.,A.nilotica(L.)Delile(阿拉伯胶金合欢),BuxuspipilosaC.K.Schneid.和Dodonaeaviscosa(L.)Jacq.(车桑子)等作为薪材面临砍伐的压力。而GrewiaoptivaDrum.exBurret作为持续利用的饲料和制绳用的种类显示良好的前景 相似文献
993.
994.
Wayne A. Mackay 《In vitro cellular & developmental biology. Plant》1999,35(4):283-284
Summary There are many Chihuahuan desert species that have potential as landscape plants for the arid communities of the southwestern
United States [agarita, Berberis trifoliata Moric.; Mexican buckeye, Ungnadia speciosa Endl.; Texas madrone, Arbutus xalapensis var. texana (Buckl.). A. Gray]. Within these plant populations, there are superior genotypes that offer even greater interest for the
landscape. However, it is difficult to clonally propagate many of these species with conventional techniques, and the seed-derived
populations often do not breed true. Therefore, selection of superior genotypes in wild populations coupled with clonal propagation
through tissue culture may offer an attractive option. It is relatively easy to achieve disinfestation of explants from desert
plants due to a general lack of natural surface contamination by fungi and bacteria, even though interference from numerous
trichomes can impede good contact with disinfesting agents. However, there is only a narrow window of time that is ideal for
explant collection, because of the brief, periodic flushes of growth that characterize this unusual plant group. There may
be years when, due to the harsh environment, the amount of suitable explant material is severely limited. Phenolics and exudates
are also problematic in this group of plants, and acclimatization of ex vitro plantlets to the harsh desert environment is
a particular challenge. For these reasons, specific adaptations and modifications were necessary to achieve success with micropropagation
of desert plant species such as Mexican redbud (Cercis canadensis var. mexicana L.). 相似文献
995.
996.
小麦与高冰草属间体细胞杂交获可育杂种植株 总被引:11,自引:0,他引:11
普通小麦(TriticumaestivumL.2n=42)“济南177”与紫外线照射的高冰草(长穗偃麦草Agropyronelongatum,2n=70)原生质体在PEG诱导下融合,获杂种再生植株。取杂种子房诱导产生愈伤组织并再生植株,经染色体和同工酶鉴定,它们仍保留杂种性质。其中两株移栽成活并结实,杂种性质也经表型、染色体、同工酶和RAPD分析得到证明。在F0和F1代植株根尖细胞中,均发现高频率地存在着染色体断片;从F2代花粉母细胞减数分裂的染色体数目及行为发现,杂种细胞染色体数目主要分布在18Ⅱ~22Ⅱ,染色体断片发生配对及分离,表明它们是小染色体(minichromosomes)。F1及F2代植株比亲本小麦(“济南177”)秆茎粗硬、生长健壮,穗大粒大,已经产生具有优良性状的F2代穗系 相似文献
997.
The historical progress in recent years pertaining to the sucrose-starch conversion in heterotrophic tissues of plants has been described. Special attention has been focused on the enzymatic breakdown of sucrose to produce hexose units that are transported to the amyloplast compartment by means of specific translocator molecules and act as glucose donors for starch biosynthesis. Although the current prevailing view is that variable mechanisms operate in different plant tissues and organs, it is often argued that the following enzymic steps are essential in the overall step of sucrose to starch conversion: sucrose + UDP -> UDPGlc + Fru(sucrose synthase-SS) (UDPGlc UDPGlc + PPi -» G1P + UTPpyrophosphorylase-UGPase) (ADPGlc GlP + ATP -» ADPGlc + PPipyrophosphorylase-AGPase) (starch ADPGlc -> starchsynthase) The presence of an ADPGlc-specific translocator in the amyloplast envelope has been demonstrated in a number of plant sources, which indicates the potential role of ADPGlc-synthesizing machineries located in the cytosol of starch-storing cells. Although it was initially believed that AGPase is present exclusively in the amyloplast compartment, the presence of a cytosolic enzyme has been shown in some cereals. The SS has a potential to produce ADPGlc, but the general belief is that this is not a dominant reaction in the mechanism of starch biosynthesis. Numerous experimental trials have been reported by many scientists employing transgenic plants transformed with cDNAs either in antisense- or sense- orientation encoding enzymes which are presumably involved in the process of sucrose-starch conversion. Although great caution is needed to interpret the data obtained, the general picture is contradictory to the mechanism presented above. It now appears that serious reconsideration is needed for the possible mechanism of SS-catalyzed ADPGlc formation and its subsequent link to starch formation. In the newly proposed mechanistic scheme, which appears to be consistent with the results by other scientists as well, hexokinase, phosphoglucomutase (PGM), and ADPGlc formation by AGPase are components in the cyclic turnover of starch molecules in the amyloplast compartment. 相似文献
998.
Patterns of reproductive effort in male and female shrubs of Oemleria cerasiformis: a 6-year study 总被引:2,自引:0,他引:2
1 We monitored flowering and fruiting of individual male and female plants of Oemleria cerasiformis over a 6-year period in a population in western Canada, and calculated fruit set (percentage of pistils maturing) and reproductive effort (RE) (gram of reproductive tissue per gram of leaf).
2 Over 6 years, male O. cerasiformis had on average much lower total RE, but much higher RE at flowering, than females.
3 In males, strong correlations between RE and light suggested that investment in reproduction was largely determined by light levels. There were strong positive correlations of RE between years, with no evidence of periodic fluctuations.
4 In females, in contrast to males, RE at flowering was not related to light. However, fruit set was strongly correlated with light. Flowering RE and fruit set were uncorrelated in females, indicating that these are affected by different factors.
5 Correlations of RE between years in females, although often significant, were lower than in males, indicating that RE fluctuates more between years in females than in males and may respond to past levels of RE. Flowering may reflect adjustments in response to past reproduction, or may be controlled by resources other than light. Fruit set was not significantly related to previous RE.
6 The greater total RE of females and their limited ability to adjust fruit set are probably major factors contributing to the greater mortality rates of females and the male-biased sex ratios in O. cerasiformis . 相似文献
2 Over 6 years, male O. cerasiformis had on average much lower total RE, but much higher RE at flowering, than females.
3 In males, strong correlations between RE and light suggested that investment in reproduction was largely determined by light levels. There were strong positive correlations of RE between years, with no evidence of periodic fluctuations.
4 In females, in contrast to males, RE at flowering was not related to light. However, fruit set was strongly correlated with light. Flowering RE and fruit set were uncorrelated in females, indicating that these are affected by different factors.
5 Correlations of RE between years in females, although often significant, were lower than in males, indicating that RE fluctuates more between years in females than in males and may respond to past levels of RE. Flowering may reflect adjustments in response to past reproduction, or may be controlled by resources other than light. Fruit set was not significantly related to previous RE.
6 The greater total RE of females and their limited ability to adjust fruit set are probably major factors contributing to the greater mortality rates of females and the male-biased sex ratios in O. cerasiformis . 相似文献
999.
Thierry C. Vrain 《Journal of nematology》1999,31(4):424-436
Bioengineering strategies are being developed that will provide specific and durable resistance against plant-parasitic nematodes in crops. The strategies come under three categories: (i) transfer of natural resistance genes from plants that have them to plants that do not, to mobilize the defense mechanisms in susceptible crops; (ii) interference with the biochemical signals that nematodes exchange with plants during parasitic interactions, especially those resulting in the formation of specialized feeding sites for the sedentary endoparasites—many nematode genes and many plant genes are potential targets for manipulation; and (iii) expression in plant cells of proteins toxic to nematodes. 相似文献
1000.