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1.
目前,测定柴油十六烷值的试验机价格较高,现有十六烷指数预测精度低,为满足炼油厂生产柴油在线调合的需要,迫切需要建立预测精度高的柴油十六烷值预测模型。基于450个具有代表性的柴油样本,建立了柴油理化性质、烃族组成与十六烷值数据库;进而采用逐步回归分析方法,应用统计产品和服务解决方案(SPSS)软件,建立了基于柴油理化性质的十六烷值预测模型和基于柴油烃族组成的十六烷值预测模型。采用F检验、T检验、残差分析验证了上述模型的有效性,并通过计算均方根误差,比较了上述两个模型的精度,结果表明,两种预测模型均有效,基于理化性质模型的预测精度优于基于烃族组成的模型。  相似文献   
2.
《Journal of dairy science》2022,105(5):4461-4473
The provision of pasture and outdoor access for dairy cattle differs around the globe. For example, in Ireland, New Zealand, and Australia, dairy farms are largely pasture based, whereas dairy farms in the United States and Canada are largely confinement based. There is a high level of public support for pasture and outdoor access for dairy cows, and the available evidence shows that dairy cattle are highly motivated to access pasture, especially at night. The decision as to whether to provide outdoor access is typically made by farmers, but little is known about dairy farmers' perspectives on this topic. We investigated perspectives of Western Canadian dairy farmers on outdoor access, as well as how they believe different stakeholders (i.e., the dairy industry, the dairy cows, and the general public) regard outdoor access for dairy cows. Data were collected via (1) 11 focus group discussions with a total of 50 Western Canadian dairy farmers, and (2) semi-structured individual interviews with an additional 6 dairy farmers of Hutterite colonies. Data were analyzed using template analysis. Although most participants in this study did not provide outdoor access on their farms, or only provided outdoor access to certain cow groups, participants generally mentioned that they enjoyed seeing cows on pasture or outdoors. However, participants shared that the Canadian supply management system (including processors) required a consistent flow of production, which was thought to be easier and more economically realized with indoor housing of lactating cows. Participants believed that pasture or outdoor access for dairy cows was desired by the public. Some participants believed that dairy cows prefer to spend time outside under favorable weather conditions, but others felt that cows preferred to stay indoors in modern, ventilated freestall barns. The results of this study describe the perspectives of dairy farmers regarding the views of dairy industry stakeholders as they relate to outdoor access, helping to inform conversations around the provision of outdoor access for dairy cattle.  相似文献   
3.
The presence of oxygen vacancies and hydroxyl groups are both favorable for the methanol electrooxidation on Pt-based catalysts.Understanding and differentiating the enhancing mechanism between oxygen vacancies and hydroxyl groups for high activity of Pt catalysts in methanol oxidation reaction(MOR)is essential but still challenging.Herein,we developed two kinds of co-catalyst for Pt/CNTs,Pr6O11is rich in oxygen vacancies but contains substantially no hydroxyl groups,while Pr(OH)3 possesses abundant hydroxyl groups without oxygen vacancies.After a seque nce of designed experiments,it can be found that both oxygen vacancies and hydroxyl groups can improve the performance of Pt/CNTs electrocatalysts,but the enhancing mechanism and improving degree of oxygen vacancies and hydroxyl groups for the MOR are different.Since the oxygen vacancies are more conducive to increasing the intrinsic activity of the Pt catalyst,and the hydroxyl groups play a decisive role in dehydrogenation and deproto nation of methanol,the co-catalysts with both oxygen vacancies and hydroxyl groups mixed with Pt/CNTs have higher catalytic performance.Therefore,hydroxyl-rich Pr6O11·xH2O was prepared and used as MOR electrocatalyst after mixed with Pt/CNTs.Benefiting from the synergistic effect of oxygen vacancies and hydroxyl groups,the Pr6O11·xH2O/Pt/CNTs shows a high peak current density of 741 mA/mg,which is three times higher than that of Pt/CNTs.These new discoveries serve as a promising strategy for the rational design of MOR catalysts with low cost and high activity.  相似文献   
4.
Self-assembly of artificial peptides has been widely studied for constructing nanostructured materials, with numerous potential applications in the nanobiotechnology field. Herein, we report the synthesis and hierarchical self-assembly of collagen-mimetic peptides (CMPs) bearing various aromatic groups at the N-termini, including 2-naphthyl, 1-naphtyl, anthracenyl, and pyrenyl groups, into nanofibers. The CMPs (R-(GPO)n: n > 4) formed a triple helix structure in water at 4 °C, as confirmed via CD analyses, and their conformations were more stable with increasing hydrophobicity of the terminal aromatic group and peptide chain length. The resulting pre-organized triple helical CMPs showed diverse self-assembly into highly ordered nanofibers, reflecting their slight differences in hydrophobic/hydrophilic balance and configuration of aromatic templates. TEM analysis demonstrated that 2Np-CMPn (n = 6 and 7) and Py-CMP6 provided well-developed natural collagen-like nanofibers and An-CMPn (n = 5–7) self-assembled into rod-like micelle fibers. On the other hand, 2Np-CMP5 and 1Np-CMP6 were unable to form nanofibers under the same conditions. Furthermore, the Py-CMP6 nanofiber was found to encapsulate a guest hydrophobic molecule, Nile red, and exhibited unique emission behavior based on the specific nanostructure. In addition to the ability of CMPs to bind small molecules, their controlled self-assembly enables their versatile utilization in drug delivery and wavelength-conversion nanomaterials.  相似文献   
5.
沉降助剂法是脱除催化裂化外甩油浆中固体颗粒的有效方法。针对现有油浆沉降剂中存在的不足,本文将提供氢键和酸碱对作用的胺类基团与提供架桥作用的嵌段聚醚相结合,制备出一种端氨基嵌段聚醚,并通过液体核磁图谱确定其化学结构。对比实验证明,胺类基团与聚醚结构起到协同作用,且键接的方式有助于促进胺类基团在油浆中分散。为方便后续应用,将端氨基嵌段聚醚与溶剂油、乙二醇进行复配,得到不同含量的端氨基嵌段聚醚类油浆沉降剂。通过对加剂量、沉降温度和沉降时间的考察,确定最佳沉降工艺为加入400mg/kg端氨基嵌段聚醚质量分数为40%的沉降剂,在90℃下沉降48h。此时脱灰率能达到90%以上,可将灰分降至0.02%以下,可用于生产高级炭黑等高附加值产品。该沉降剂原料易得且效果好,有望实现大规模的工业化生产和应用。  相似文献   
6.
Ending group halogenation is an effective strategy for modulating the energy levels, bandgaps, and intermolecular interactions of nonfullerene acceptors. Understanding the influence of different halogen atoms on the acceptor properties is of great importance for designing high-performance nonfullerene acceptors. Here, three acceptor–donor–acceptor (A-D-A) type nonfullerene acceptors (M5, M6, and M7), which are constructed by using a ladder-type heteroheptacene core without the traditional sp3 carbon-bonded side chains as the electron-rich core, and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile without or with halogen atoms as the ending groups. The nonfullerene acceptors with chlorinated (M6) and brominated (M7) ending groups exhibit broadened absorption spectra, down-shifted energy levels, and enhanced molecular ordering compared to the counterpart without any halogenated ending groups (M5). Among the nonfullerene acceptors, M6 has the strongest intermolecular π π interaction with its shortest π π interaction distance and the longest coherent length which are beneficial for enhancing the charge transport and therefore boosting the photovoltaic performance. An excellent power conversion efficiency of 15.45% is achieved for the best-performing polymer solar cell based on M6. These results suggest that the halogenated ending groups are essential for high-performance heteroheptacene-based nonfullerene acceptors considering their simultaneous enhancements in both the light-harvesting and the charge transport.  相似文献   
7.
In view of the problems in the construction of characteristic professional groups in higher vocational colleges, the professional group of "intelligent manufacturing" is taken as the research object, and the "platform + module" suitable for the development of the industry will be constructed according to the content of the vocational ability planning courses of the post group. The curriculum system establishes the framework of professional groups, and explores and forms a strategic study to optimize and integrate professional group resources.  相似文献   
8.
纳米微晶纤维素的表面基团及其改性   总被引:2,自引:1,他引:1       下载免费PDF全文
纳米微晶纤维素(Nanocrystalline Cellulose,NCC)是一种纤维素经酸水解后获得的棒状晶体,由于其原料丰富、可再生、生物兼容性好以及机械性能优良等特点,已成为纳米材料研究领域的热点。本文为探索其进一步改性应用,重点分析了NCC表面存在的基团种类,对其化学改性方法进行了概括,并对其进一步发展应用进行了展望。  相似文献   
9.
A mass balance model of trophic interactions among ten key functional producer and consumer groups in Lake Volta was constructed using the Ecopath model to study the energy flows and species interactions in the lake. The present study was based on secondary and primary data on fish catch, diet composition, phytoplankton and zooplankton biomasses, collected in 2015 and 2016. Additional information on growth parameters of major species required for balancing the Ecopath model was obtained from sampling and FishBase. The functional groups were detritus, phytoplankton, zooplankton, benthos, prey fish, Tilapia, Bagrus, Chrysichthys, Alestes and Synodontis species. Four trophic levels were identified in the Lake Volta ecosystem, with the energy flow occurring mainly within the first three trophic levels. The calculated ecotrophic efficiency value of the primary producers (phytoplankton: 0.17; detritus: 0.22) indicated they were least exploited, compared to the secondary producers, zooplankton (0.80) and benthos (0.50). All secondary consumers had ecotrophic efficiency values higher than the primary producers, indicating they are exploited in the ecosystem. The main energy flows in the lake were from phytoplankton and detritus at trophic level I, and Bagrus species, the top predator, at a level of 3.30. The network analysis, illustrating a connectance index of 0.43 and an omnivory index of 0.06, in the lake system indicated the ecosystem is unstable, somewhat immature and still in a developing stage.  相似文献   
10.
运用集成方法从重大工程业主统筹项目的角度进行系统性思考是应对重大工程项目群系统复杂性的关键视角。基于综合集成管理方法,以项目群型重大工程为例,结合深圳前海19 单元03 街坊项目,以综合集成管理的相关文献为基础,建立了综合集成管理的理论模型,从重大工程综合集成管理的多层次协调机制、过程集成、知识集成、技术集成、治理机制集成5 个维度全面分析了综合集成管理方法在重大工程管理的应用。相关案例发现和经验总结丰富了重大项目群管理系统集成的内涵和方法,同时为业主项目群管理带来实践指导。  相似文献   
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