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排序方式: 共有4298条查询结果,搜索用时 15 毫秒
91.
本文给出了一种数值求解变系数对流扩散反应方程的指数型高精度紧致差分方法.我们首先将模型方程变形,借助常系数对流扩散方程的指数型高精度紧致差分格式,采用残量修正法得到变系数对流扩散反应方程的指数型高精度紧致差分格式;并从理论上分析了当Pelect数很大时,本文格式达到四阶计算精度时网格步长的限制条件;离散得到的代数方程组可采用追赶法直接求解.数值实验结果与理论分析完全吻合,表明了本文格式对于边界层问题或大梯度变化的物理量求解问题具有的高精度和鲁棒性的优点. 相似文献
92.
Oxidative Stress Imaging: Visualizing Oxidative Cellular Stress Induced by Nanoparticles in the Subcytotoxic Range Using Fluorescence Lifetime Imaging (Small 23/2018)
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93.
目的 探究不同处理对贮藏0~60 d期间蓝靛果实贮藏品质及活性氧(ROS)代谢的影响,为蓝靛果贮藏保鲜提供技术依据。方法 以蓝靛果为实验材料,采后将其装入保鲜箱中,用1−甲基环丙烯(1-MCP)、乙烯吸收剂(EA)、1-MCP+EA进行处理,在(−0.5±0.3)℃下贮藏60 d,每隔15 d取样观察果实的感官品质,并测定其营养、生理及活性氧代谢相关指标。结果 与对照组相比,3种处理方式均能保持果实较好的感官特性,延缓果实抗坏血酸、花色苷、总酚和黄酮等含量的流失,以及果实的软化;在贮藏60 d时,处理组果实的呼吸强度分别比对照组果实的呼吸强度低22.73、12.92、34.04 mg/(kg.h),乙烯生成速率分别比对照组果实的低6.38、3.98、10.11 μL/(kg.h);可抑制超氧阴离子(O2−.)活性、过氧化氢(H2O2)含量、丙二醛含量及相对电导率的升高,保持较高的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)活性。通过SPSS分析可知,综合得分顺序为CK<EA<1-MCP<1-MCP+EA,表明1-MCP+EA处理的效果最好。结论 1-MCP+EA处理对蓝靛果贮藏60 d的保鲜效果最好,可更好地保留果实的外观和内在品质,利于运输和销售。 相似文献
94.
《Advanced Powder Technology》2023,34(1):103886
Reactive oxygen species (ROS) are reactive substances closely related to the inflammatory response, and previous studies have shown that anti-inflammatory therapy can achieve significant effects by scavenging ROS. Nanozymes are synthetic mimics of natural enzymes that are more stable, customizable, inexpensive, and catalytic for ROS. Therefore, we prepared a novel manganese-loaded mesoporous silica nanozyme (MnMSN) by template method and KMnO4 oxidation surfactant templates. The physicochemical properties of the nanomaterials were investigated by XRD, TEM, SEM, size, Zeta potential and BET, etc. The results showed that MnMSN contains MnO2 (Mn4+) and MnSiO3 (Mn2+), and the particle size of MnMSN is smaller with the increase of KMnO4 oxidation surfactant templates time, and the in vitro scavenging of ROS (H2O2, ·OH and ·O2–) is more effective. MnMSN has good cytocompatibility, scavenging intracellular ROS and inducing a shift from M1 to anti-inflammatory M2 phenotype. Furthermore, the intrinsic mechanism of MnMSN regulation of macrophage polarization was investigated by ELISA and qPCR, and the results showed that MnMSN is through scavenging ROS, leading to the down-regulation of NF-κB, which further leads to the down-regulation of TNF-α and IL-Iβ. The results of this work highlight the potential of MnMSN in catalyzing anti-inflammatory therapy. 相似文献
95.
Remote sensing of structural complexity indices for habitat and species distribution modeling 总被引:1,自引:0,他引:1
Spatial distribution models are increasingly used in ecological studies, but are limited by the poor accuracy of remote sensing (RS) for mapping microhabitat (< 0.1 ha) features. Mapping accuracy can be improved by combining advanced RS image-processing techniques with microhabitat data expressed as a structural complexity index (SCI). To test this idea, we used principal components analysis (PCA) and an additive SCI method developed for forest ecology (calculated by re-scaling and summing representative structural variables) to summarize 13 microhabitat-scale (0.04 ha) vegetation structure attributes describing the rare mountain bongo antelope's (Tragelaphus eurycerus isaaci) habitat in Kenya's Aberdare mountains. Microhabitat data were collected in 127 plots: 37 related to bongo habitat use, 90 from 1 km-spaced grid points representing overall habitat availability and bongo non-presence. We then assessed each SCI's effectiveness for discerning microhabitat variability and bongo habitat selection, using Wilcoxon Rank Sum tests for differences in mean SCI scores among plots divided into 4 vegetation classes, and the Area Under the Curve (AUC) of receiver operating characteristics from logistic regressions. We also examined the accuracy of predicted SCI scores resulting from regression models based on variables derived from a) ASTER imagery processed with spectral mixture and texture analysis, b) an SRTM DEM and c) rainfall data, using the 90 grid plots for model training and the bongo plots as an independent test dataset. Of the five SCIs derived, two performed best: the PCA-derived Canopy Structure Index (CSI) and an additive index summarizing 8 structural variables (AI8). CSI and AI8 showed significant differences between 5 of 6 vegetation class pairs, strong abilities to distinguish bongo-selected from available habitat (AUCs = 0.71 (CSI); 0.70 (AI8)), and predicted scores 60-110% more accurate than reported by other studies using RS to quantify individual microhabitat structural attributes (CSI model R2 = 0.51, RMSE = 0.19 (training) and 0.21 (test); AI8 model R2 = 0.46, RMSE = 0.17 (training) and 0.19 (test)). Repeating the Wilcoxon tests and logistic regressions with RS-predicted SCI values showed that AI8 most effectively preserved the patterns found with the observed SCIs. These results demonstrate that SCIs effectively characterize microhabitat structure and selection, and boost microhabitat mapping accuracy when combined with enhanced RS image-processing techniques. This approach can improve distribution models and broaden their applicability, makes RS more relevant to applied ecology, and shows that processing field data to be more compatible with RS can improve RS-based habitat mapping accuracy. 相似文献
96.
Lexi Zhang Jianghong Zhao Haiqiang Lu Liming Gong Li Li Jianfeng Zheng Hui Li Zhenping ZhuAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):364
Nanoparticle-assembled ZnO micro-octahedrons were synthesized by a facile homogeneous precipitation method. The ZnO micro-octahedrons are hexagonal wurtzite with high crystallinity. Abundant structure defects were confirmed on ZnO surface by photoluminescence. Gas sensors based on the ZnO micro-octahedrons exhibited high response, selectivity and stability to 1–1000 ppm formaldehyde at 400 °C. Especially, even 1 ppm formaldehyde could be detected with high response (S = 22.7). It is of interest to point out that formaldehyde could be easily distinguished from ethanol or acetaldehyde with a selectivity of about 3. The high formaldehyde response is mainly attributed to the synergistic effect of high contents of electron donor defects (Zni and VO) and highly active oxygen species (O2−) on the ZnO surface. 相似文献
97.
生物地理学优化算法研究 总被引:2,自引:0,他引:2
张建科 《计算机工程与设计》2011,32(7):2497-2500
对生物地理学优化算法(biogeography-based optimization,BBO)的研究现状进行了总结,并介绍了一些最新的研究进展。从BBO算法提出的背景出发,讨论了算法的主要思想、算法原理以及算法步骤。论述了该算法的研究进展,包括BBO算法的改进、算法的收敛性分析、BBO算法与其他算法的融合以及BBO算法在优化领域的典型应用,对BBO算法有待研究的问题做了总结。 相似文献
98.
主要研究查询点固定,目标对象移动且移动对象在位置不确定的情况下,成为Skyline对象的可能性(采用概率形式表示),并实现移动对象位置不确定条件下的连续Skyline查询。定义了影响P-Skyline集合的Events,提出了一个基于事件的算法E-CPS,该算法并通过计算,跟踪和处理Events来更新P-Skyline集合。该方法大大减少了算法的查找和计算开销,提高了运算效率。 相似文献
99.
100.