全文获取类型
收费全文 | 371篇 |
免费 | 95篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 40篇 |
综合类 | 26篇 |
化学工业 | 74篇 |
金属工艺 | 18篇 |
机械仪表 | 12篇 |
建筑科学 | 29篇 |
矿业工程 | 13篇 |
能源动力 | 12篇 |
轻工业 | 66篇 |
水利工程 | 14篇 |
石油天然气 | 25篇 |
武器工业 | 3篇 |
无线电 | 44篇 |
一般工业技术 | 63篇 |
冶金工业 | 5篇 |
原子能技术 | 1篇 |
自动化技术 | 53篇 |
出版年
2024年 | 12篇 |
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 65篇 |
2020年 | 35篇 |
2019年 | 26篇 |
2018年 | 38篇 |
2017年 | 31篇 |
2016年 | 25篇 |
2015年 | 41篇 |
2014年 | 30篇 |
2013年 | 27篇 |
2012年 | 20篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1993年 | 1篇 |
排序方式: 共有498条查询结果,搜索用时 15 毫秒
1.
Tumor Therapy: Bifunctional Platinated Nanoparticles for Photoinduced Tumor Ablation (Adv. Mater. 46/2016) 下载免费PDF全文
2.
Influence maximization of temporal social networks (IMT) is a problem that aims to find the most influential set of nodes in the temporal network so that their information can be the most widely spread. To solve the IMT problem, we propose an influence maximization algorithm based on an improved K-shell method, namely improved K-shell in temporal social networks (KT). The algorithm takes into account the global and local structures of temporal social networks. First, to obtain the kernel value Ks of each node, in the global scope, it layers the network according to the temporal characteristic of nodes by improving the K-shell method. Then, in the local scope, the calculation method of comprehensive degree is proposed to weigh the influence of nodes. Finally, the node with the highest comprehensive degree in each core layer is selected as the seed. However, the seed selection strategy of KT can easily lose some influential nodes. Thus, by optimizing the seed selection strategy, this paper proposes an efficient heuristic algorithm called improved K-shell in temporal social networks for influence maximization (KTIM). According to the hierarchical distribution of cores, the algorithm adds nodes near the central core to the candidate seed set. It then searches for seeds in the candidate seed set according to the comprehensive degree. Experiments show that KTIM is close to the best performing improved method for influence maximization of temporal graph (IMIT) algorithm in terms of effectiveness, but runs at least an order of magnitude faster than it. Therefore, considering the effectiveness and efficiency simultaneously in temporal social networks, the KTIM algorithm works better than other baseline algorithms. 相似文献
3.
为有效指导农业温室气体减排政策的制定,本研究分别采用CH4MOD模型和排放因子法估算了2018年长三角地区农作物甲烷(CH4)和氧化亚氮(N2O)排放,并分析其时空分布规律,最终建立了2018年长三角地区农作物1 km×1 km网格化温室气体排放清单.研究结果表明:长三角稻田CH4排放因子为348.54 kg/hm2,农作物N2O排放因子为0.95 kg/hm2,与前人研究结果具有一致性.长三角地区稻田CH4排放为176.9万t(折合约3 714.9万t CO2当量),最主要排放源为单季稻稻田;农作物N2O排放为15114.9 t(折合约450.4万t CO2当量),小麦是主要贡献源.CH4和N2O排放均主要来源于江苏省和安徽省,且集中在4—8月.建议加强对农业温室气体排放的管控,从源头上减少农田碳氮源的输入. 相似文献
4.
5.
Shuangshuang Song Baocheng Tian Fen Chen Wenji Zhang Yusheng Pan Qiang Zhang 《Drug development and industrial pharmacy》2015,41(1):51-62
Objective: The objectives of this study were, first, to develop a free-flowing and stable proniosome formulation for poorly water-soluble drugs such as vinpocetine; and second, to estimate its bioavailability as oral drug delivery system.Methods: The proniosomes consisting of span60, cholesterol, sorbitol and vinpocetine were prepared by a novel approach. After the proniosomes were contacted with water, the suspension of vinpocetine-loaded niosomes formed automatically. The proniosomes and reconstituted niosomes were evaluated for their physicochemical characteristics, in vitro drug dissolution and release, integrity and stability at different GI tract pH conditions, in situ single-pass intestinal perfusion and in vivo bioavailability.Results: The proniosome powder exhibited excellent flowability. The reconstituted niosomes with high drug entrapment efficiency (89.67?±?3.28%) showed spherical morphology with smooth surface under transmission electron microscope (TEM). X-ray diffraction (XRD) indicated that the drug was in an amorphous or molecular state in proniosome powder. In vitro dissolution and release study, proniosomes did enhance the dissolution and release rate compared to vinpocetine suspension in phosphate buffer solution (pH 7.2). Proniosome-derived niosomes could keep their integrity and stability at different GI tract pH conditions. The in situ single-pass intestinal perfusion indicated that encapsulation of vinpocetine into niosomes could largely improved the absorption of vinpocetine. The AUC(0?∞) of F2 and F3 was about 4.0- and 4.9-fold higher than that of the vinpocetine suspension, respectively. The results demonstrated the proniosomes indeed remarkably enhanced the oral bioavailability of vinpocetine.Conclusion: This study suggested the potential of proniosomes as stable precursors for the immediate preparation of niosome carrier systems. 相似文献
6.
以高枝化聚乙烯亚胺(PEI)为稳定剂,硼氢化钠为还原剂,利用化学还原法制备了纳米银抗菌剂。探讨了温度、PEI与Ag+的摩尔比对纳米银抗菌剂合成的影响,利用紫外分光光度法及扫描电镜对合成纳米银抗菌剂进行了表征,利用抑菌圈实验分别对纳米银及PEI进行了抑菌性能测试,筛选出稳定性好抑菌性强的纳米银抗菌剂制备工艺。实验结果表明,在45℃,PEI与Ag+的摩尔配比在2∶1~0.6∶1条件下能制备无色透明且抑菌性强的具有核壳结构的纳米银抗菌剂,PEI对纳米银抗菌剂具有协同作用。 相似文献
7.
8.
9.
Development of Electrospun Composite Fibers in Multiscale Structure and Investigating the Performance on Proliferation and Osteogenic Differentiation of ADSCs 下载免费PDF全文
Electrospun composite membranes in multiscale structures are developed for bone tissue engineering. Aligned polycaprolactone (PCL) fibers entrapping CA‐HAp microparticles (containing CaCO3, hydroxyapatite, and casein in a hierarchical organization) are electrospun to find whether synergistic effects of fiber alignment and CA‐HAp microparticles on improving osteogenic differentiation can be obtained. CA‐HAp microparticles are in a spherical morphology of 1.42 ± 0.26 µm. Their presence increases fiber diameter and does not significantly affect fiber alignment. On all membranes, adipose derived stem cells (ADSCs) from humans spread very well. On a random group, cells distribute randomly and the presence of CA‐HAp microparticles facilitates cell proliferation, especially for the one at CA‐HAp/PCL 50 wt%; the one at CA‐HAp/PCL 20 wt% shows significantly much higher alkaline phosphatase (ALP) activity (112.0% higher) than the pure PCL membrane. On aligned samples, cells align along fibers and expression of ALP is enhanced. However, at the same composition (CA‐HAp/PCL 20 wt%), the random sample has much higher ALP activity than the aligned sample. The expressions of osteogenic marker genes are also evaluated. Combining the results and the applicability of membranes together, the random membrane at CA‐HAp/PCL 20 wt% is the best candidate for bone tissue engineering. 相似文献
10.
The direct electrochemistry and electrocatalysis of horseradish peroxidase (HRP) immobilized on a gelatin - N, N-dimethylformamide (DMF) - hydrophobic ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophsohate) gel film coated glassy carbon electrode has been studied for the first time. The immobilized HRP exhibits a pair of well-defined quasi-reversible peaks in pH 7.0 phosphate buffer solutions, which results from the direct electron transfer between the enzyme and the underlying electrode. In this case there is about 2.7% of the immobilized HRP undergoing the electrochemical reaction, which corresponds to multi-layer of HRP on the electrode surface. The HRP immobilized has higher thermal stability than in gelatin hydrogel. Experiment results also show that the voltammetric behavior of the enzyme electrode depends on the type of room temperature ionic liquid (RTIL) used. When a more hydrophobic RTIL is adopted, the resulting enzyme electrode gives better performance. In the presence of hydrogen peroxide, the enzyme electrode shows sensitive response. The sensitivity of the catalytic peak is up to 1.38 A cm−2 M−1 and the Michaelis constant is down to 6.84 × 10−5 M, which are superior to that reported elsewhere. In addition, the UV-visible spectra of HRP entrapped in different films and the mass transfer of hydrogen peroxide are discussed as well. 相似文献