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991.
992.
Environmental and stomatal control of transpiration, canopy conductance and decoupling coefficient in young lemon trees under shading net 总被引:2,自引:0,他引:2
E. Nicols V.L. Barradas M.F. Ortuo A. Navarro A. Torrecillas J.J. Alarcn 《Environmental and Experimental Botany》2008,63(1-3):200-206
Sap flow, as a measure of transpiration, was monitored in 2-year-old lemon trees growing in pots. Eight trees were used in the experiment, four of which were placed under a rectangular shading net, while the other four were maintained in the open air. Daily averages of canopy conductance and photosynthesis were not affected by shading; however, the daily transpiration was reduced in shaded plants, which displayed an increase in water use efficiency compared with exposed trees. The decoupling coefficient was higher in the shaded trees, indicating that the transpiration of lemon trees was efficiently controlled by stomata in exposed plants, while the transpiration rate was mainly influenced by radiation in the plants growing under the net. This influence was more pronounced in the afternoon, when the whole tree transpiration was largely dominated by equilibrium transpiration in the plants under netting, and the relationship between transpiration and radiation showed a steeper slope in shaded trees. The reduction in transpiration and the maintenance of photosynthesis in shaded plants with respect to exposed trees indicated that screen structures in semi-arid and arid environments could be considered as an intermediate solution for reducing plant water stress and increasing water use efficiency. 相似文献
993.
994.
Epichloë内生真菌感染能够影响宿主植物的生长发育, 但关于内生真菌感染对宿主植物叶形状和叶面积的研究很少。该研究以羽茅(Achnatherum sibiricum)为实验材料, 采用长宽系数计算和扫描测定叶面积相结合的方法探究内生真菌种类和羽茅母本基因型对羽茅-内生真菌共生体叶形状和叶面积的影响。结果表明: 内生真菌感染与否、内生真菌种类和宿主母本基因型对反映叶形状的叶校正系数、叶片长度、宽度和长宽比均无显著影响, 经计算与验证, 确定了羽茅叶片的校正系数为0.594 9。采用该校正系数及叶长宽计算的叶面积与实测叶面积无显著差异, 且二者均未受到内生真菌感染与否、内生真菌种类或宿主植物母本基因型的显著影响。 相似文献
995.
《Saudi Journal of Biological Sciences》2020,27(1):1-5
Plutella xylostella L. (Lepidoptera: Plutellidae) is an important pest causing significant losses to vegetables worldwide. Insecticides resistance in P. xylostella is a serious issue for scientists since last 30 years. However, deltamethrin and Bt Cry1Ac are commonly used insecticides against P. xylostella but studies involving development of resistance in P. xylostella against these two insecticides at different temperatures are lacking. The current study was aimed to find out the toxicity of deltamethrin and Bt Cry1Ac, and resistance development in P. xylostella. Results showed that the positive correlation between the temperature and toxicities of deltamethrin and Bt Cry1Ac. The results indicated −0.051, −0.049, −0.047, and −0.046 folds of deltamethrin resistance at 15 °C, 20 °C, 25 °C, and 30 °C temperatures, respectively from 1st to 12th generations. The toxicity of Bt Cry1Ac after 24 h was 2.2 and 4.8 folds on 1st generation at 20 °C and 25 °C temperatures, respectively compared to the toxicity recorded at 15 °C (non-overlapping of 95% confidence limits). Based on the results of this study, it is concluded that the temperature has a positive correlation with the toxicity of deltamethrin and Bt Cry1Ac against the larvae of P. xylostella. This study suggests that deltamethrin and Bt Cry1Ac can be included in the management program of P. xylostella on many vegetable crops. The baseline susceptibility data might be helpful to understand the resistance mechanisms in P. xylostella. 相似文献
996.
Marion Segall Raphaël Cornette Ramiro Godoy‐Diana Anthony Herrel 《Ecology and evolution》2020,10(14):6993-7005
Phenotypic diversity, or disparity, can be explained by simple genetic drift or, if functional constraints are strong, by selection for ecologically relevant phenotypes. We here studied phenotypic disparity in head shape in aquatic snakes. We investigated whether conflicting selective pressures related to different functions have driven shape diversity and explore whether similar phenotypes may give rise to the same functional output (i.e., many‐to‐one mapping of form to function). We focused on the head shape of aquatically foraging snakes as they fulfill several fitness‐relevant functions and show a large amount of morphological variability. We used 3D surface scanning and 3D geometric morphometrics to compare the head shape of 62 species in a phylogenetic context. We first tested whether diet specialization and size are drivers of head shape diversification. Next, we tested for many‐to‐one mapping by comparing the hydrodynamic efficiency of head shape characteristic of the main axes of variation in the dataset. We 3D printed these shapes and measured the forces at play during a frontal strike. Our results show that diet and size explain only a small amount of shape variation. Shapes did not fully functionally converge as more specialized aquatic species evolved a more efficient head shape than others. The shape disparity observed could thus reflect a process of niche specialization. 相似文献
997.
An efficient regeneration system of Rhynchostylis retusa was established to provide technical reference for the
application of tissue culture tube seedlings in production. The mixtures of callus and protocorm from aseptic germination were used as explants. The optimal media of each stage was selected for callus proliferation, protocorm
occurrence and growth, rejuvenation and rooting via a single, complete combination and orthogonal experiment.
The results showed that the optimal medium for callus proliferation, protocorms occurrence and growth was 1/2
Murashige and Skoog (MS) medium adding 50 g·L−1 banana puree, 0.1 mg·L−1 α-naphthaleneacetic acid (NAA),
1.5 mg·L−1 6-benzylaminopurine (6-BA) and 1.0 mg·L−1 kinetin (KT) with 17.33 proliferation coefficient of callus
and 19.63 occurrence coefficient of buds after 90 days. Then the buds occurred from protocorm were cultured on
1/2 MS medium including 100 g·L−1 banana puree, 1.0 mg·L−1 NAA, 2.0 mg·L−1 6-BA and 0.05 mg·L−1 KT, in
which the proliferation coefficient of callus was 10.32 and occurrence coefficient of buds reached 17.87. In the
further subculture, the same medium was simultaneously used for callus proliferation, protocorm occurrence
and bud growth. The plantlets developed roots in 1/2 MS medium containing 70 mL·L−1 coconut water and
1.5 mg·L−1 NAA with 100% rooting rates after 90 days. The survival rate was more than 90% after domestication
and transplantation. This regeneration protocol will provide technique foundation for protecting wild resource
and developing artificial cultivation. 相似文献
998.
The intraclass correlation coefficient (ICC) is a classical index of measurement reliability. With the advent of new and complex types of data for which the ICC is not defined, there is a need for new ways to assess reliability. To meet this need, we propose a new distance‐based ICC (dbICC), defined in terms of arbitrary distances among observations. We introduce a bias correction to improve the coverage of bootstrap confidence intervals for the dbICC, and demonstrate its efficacy via simulation. We illustrate the proposed method by analyzing the test‐retest reliability of brain connectivity matrices derived from a set of repeated functional magnetic resonance imaging scans. The Spearman‐Brown formula, which shows how more intensive measurement increases reliability, is extended to encompass the dbICC. 相似文献
999.
以大兴安岭新林林业局翠岗林场49块兴安落叶松不同蓄积占比的固定样地调查数据为基础,分别从林分非空间结构、林分空间结构、林木多样性、土壤条件和立地条件5个方面37项观测指标,在相关性分析的基础上,构建林分尺度更新密度和更新多样性(包括树高和地径)的结构方程模型,并计算各路径的直接、间接和总影响系数,量化和提取影响大兴安岭地区兴安落叶松天然林更新密度和更新多样性的关键可控因素,为该地区森林的可持续经营提供理论基础和技术依据。结果表明: 对林分更新密度影响最大的潜变量依次为:林分非空间结构(-0.410)>林木多样性(0.380)>土壤条件(0.250)>立地条件(0.249)>林分空间结构(0.197);对林分更新多样性影响最大的潜变量依次为:土壤条件(0.778)>立地条件(0.748)>林分空间结构(0.684)>林分非空间结构(0.287)>林木多样性(0.105)。综合来看,影响更新密度和多样性的共性观测变量主要为:pH值、全钾、树种多样性、树高多样性、角尺度和单位蓄积。在后续经营中,可通过采伐或补植阔叶树种的方式来优化和调整林分的树种组成、多样性、土壤pH值和养分等特征,最终达到促进天然更新的目的。 相似文献
1000.
PurposeThe aim of this methods work is to explore the different behavior of radiomic features resulting by using or not the contrast medium in chest CT imaging of non-small cell lung cancer.MethodsChest CT scans, unenhanced and contrast-enhanced, of 17 patients were selected from images collected as part of the staging process. The major T1-T3 lesion was contoured through a semi-automatic approach. These lesions formed the lesion phantoms to study features behavior. The stability of 94 features of the 3D-Slicer package Radiomics was analyzed. Feature discrimination power was quantified by means of Gini's coefficient. Correlation between distance matrices was evaluated through Mantel statistic. Heatmap, cluster and silhouette plots were applied to find well-structured partitions of lesions.ResultsThe Gini's coefficient evidenced a low discrimination power, <0.05, for four features and a large discrimination power, around 0.8, for five features. About 90% of features was affected by the contrast medium, masking tumor lesions variability; thirteen features only were found stable. On 8178 combinations of stable features, only one group of four features produced the same partition of lesions with the silhouette width greater than 0.51, both on unenhanced and contrast-enhanced images.ConclusionsGini’s coefficient highlighted the features discrimination power in both CT series. Many features were sensitive to the use of the contrast medium, masking the lesions intrinsic variability. Four stable features produced, on both series, the same partition of cancer lesions with reasonable structure; this may merit being objects of further validation studies and interpretative investigations. 相似文献