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101.
罂粟科植物的分类,进化与分布 总被引:5,自引:1,他引:4
罂粟科有38属约700种,作者通过对科内各属的研究,根据其主要器官(雌蕊、雄蕊,花被、果和种子)的进化趋势,重新排列科内的分类系统,在3个亚科下,包括8个亚族。在此基础上,讨论各属可能的演化关系,分析它们的分布规律,最后探讨本科的起源。 相似文献
102.
金粟兰科的起源,演化及其分布 总被引:9,自引:3,他引:6
本文利用形态解剖,孢粉学及化石资料,讨论了金粟兰科的系统;并对其起源,演化和现代分布格局形成等问题做了合理推测,主要结果如下:(1)Sarcandra和Chloranthus的亲缘关系最接近,而Ascarina和Hedyosmum的系统位置最靠近。Sarcandra是金粟兰科中最原始的属,而Hedyosmum则是最进化的属。(2)金粟兰科可能于白垩纪最早期起源于木质部无导管的,具简单两性虫媒花的祖 相似文献
103.
石灰性土壤上植物根际中Fe,Mn的形态分布及其与植物吸收的关系 总被引:2,自引:1,他引:1
研究了石灰性土壤上5种作物品种根际微生态环境中Fe、Mn的形态分布.结果表明,交换态Fe(EX-Fe)、碳酸盐结合态Fe(CARB-Fe)、无定形氧化铁(AO-Fe)和交换态Mn(E-Mn)、碳酸盐结合态Mn(CARB-Mn)在根际土壤中都呈现明显的累积.各品种根际中的累积量有较大差异.相关分析表明,黄潮土上植株含Fe量、吸Fe量与根际土壤AO-Fe含量呈显著正相关.根际有效态Fe累积不仅是根际pH作用的结果,与根系分泌物对难溶性Fe活化有关.根际有效态Mn累积则受到根际土壤Eh的影响. 相似文献
104.
利用树木年轮气候学方法,根据马尾松生长对气候变量具非线性响应,尝试重建江苏暖湿地区过去116年(1874~1990)的年平均气温和降水量。温度的重建效果优于降水量,实测值与重建值两者的缩减误差(RE)分别为0.12和0.10,两者的平均偏差百分率分别为2.3%和20%。绝大部分重建结果可从观测记录和历史文献中得到验证,但在温度较高或降水量较多的若干年份,实测值与重建值有较大偏差。 相似文献
105.
Veronique Blanchard Rita Raisman-Vozari Marc Savasta Etienne Hirsch France Javoy-Agid Claude Feuerstein Yves Agid 《Journal of neurochemistry》1993,61(2):617-626
Abstract: We developed a rapid and sensitive radioimmunohistochemical method for the quantification of tyrosine hydroxylase (TH) at both the anatomical and cellular level. Coronal tissue sections from fresh-frozen rat brains were incubated in the presence of a TH monoclonal antibody. The reaction was revealed with a 35 S-labeled secondary antibody. TH content was quantified in catecholaminergic brain areas by measuring optical density on autoradiographic films or silver grain density on autoradiographic emulsion-coated sections. Regional TH concentrations determined in the locus ceruleus (LC), substantia nigra pars compacta (SNC), and ventral tegmental area (VTA) were significantly increased by 45% after reserpine treatment in the LC but unchanged in the SNC and VTA. Microscopic examination of TH radioimmunolabeling showed a heavy accumulation of silver grains over catecholaminergic cell bodies. In the LC, grain density per cell was heterogeneous and higher in the ventral than in the dorsal part of the structure. After reserpine treatment, TH levels were significantly increased (57%) in the neurons of the LC but not in those of the SNC or VTA. The data support the validity of this radioimmunohistochemical method as a tool for quantifying TH protein at the cellular level and they confirm that TH protein content is differentially regulated in noradrenergic and dopaminergic neurons in response to reserpine. 相似文献
106.
107.
Krešimir Begović Jonathan S. Schurman Marek Svitok Jakob Pavlin Thomas Langbehn Kristyna Svobodová Martin Mikoláš Pavel Janda Michal Synek William Marchand Lucie Vitková Daniel Kozák Ondrej Vostarek Vojtech Čada Radek Bače Miroslav Svoboda 《Global Change Biology》2023,29(1):143-164
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks. 相似文献
108.
鼎湖山自然林豆科固氮植物资源的调查研究 总被引:3,自引:1,他引:2
本文在调查鼎湖山自然林木本豆科植物结瘤固氮的基础上,参阅了国内外有关豆科植物结瘤固氮的主要文献,研究了鼎湖山自然林木本豆科植物的固氮资源。结果得出鼎湖山自然林中常见的木本豆科植物共有41种,其中乔木15种,灌木6种,木质藤本20种;有结瘤固氮特性的26种,其中乔木11种,灌木5种,木质藤本10种;经初步调查未见根瘤的6种,其中乔木2种,灌木1种,木质藤本3种;未调查的9种,其中乔木2种,木质藤本7种。本研究结果为鼎湖山木本豆科固氮植物资源的保护、管理和开发利用提供了科学论据,在理论和应用方面均有重要意义。 相似文献
109.
Aims
Shallow soils on acidic bedrock in dry areas of Central Europe support dry grasslands and heathlands that were formerly used as extensive pastures. These habitats are of high conservation value, but their abandonment in the 20th century triggered slow natural succession that poses a threat to specialized plant species. We asked how this vegetation and its plant diversity have changed over the past three decades and whether protected areas have positively affected habitat quality.Location
Southwestern and central Moravia, Czech Republic.Methods
In 2018–2019, we resurveyed 94 vegetation plots first sampled in 1986–1991 at 47 acidic dry grassland and heathland sites. We compared the number of all vascular plant species, Red List species and alien species per plot using parametric and non-parametric tests, life-form spectra using the chi-square test, species composition using detrended correspondence analysis, and indicator values using a permutation test. We also compared these changes between sites within and outside protected areas.Results
Vegetation changes over the past three decades have been relatively small. However, we detected a decrease in total species richness, the number of Red List species and the number of characteristic species of dry grasslands. Neophytes were infrequent, while archaeophytes increased slightly. The competitive tall grass Arrhenatherum elatius, annual species and young woody plants increased in abundance or newly established at many sites. Indicator values did not change except for a slight increase in nutrient values. These negative trends occurred both within and outside protected areas but were more pronounced outside.Conclusions
Formerly grazed acidic dry grasslands and heathlands in Moravia are slowly losing habitat specialists, including threatened plant species, and are increasingly dominated by Arrhenatherum elatius. Conservation management, especially cutting in protected areas, slows down the negative trends of decline in plant diversity and habitat quality but is insufficient to halt these processes completely. 相似文献110.
Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of plants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive interactions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration +340 µmol CO2 mol-1) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of the C3 sedgeScirpus olneyi growing in a pure stand, while the biomass of the C4 grassSpartina patens in a monospecific community was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species declined.The C4 grassSpartina patens dominated the higher areas of the salt marsh, while the C3 sedgeScirpus olneyi was most abundant at the lower elevations, and the mixed community occupied intermediate elevations.Scirpus growth may have been restricted by drought and salt stress at the higher elevations, whileSpartina growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allowsScirpus to grow at higher elevations where it in turn may affect the growth ofSpartina. 相似文献