全文获取类型
收费全文 | 1133篇 |
免费 | 26篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 31篇 |
综合类 | 96篇 |
化学工业 | 128篇 |
金属工艺 | 42篇 |
机械仪表 | 5篇 |
建筑科学 | 120篇 |
矿业工程 | 13篇 |
能源动力 | 8篇 |
轻工业 | 91篇 |
水利工程 | 26篇 |
石油天然气 | 14篇 |
武器工业 | 1篇 |
无线电 | 80篇 |
一般工业技术 | 176篇 |
冶金工业 | 5篇 |
原子能技术 | 60篇 |
自动化技术 | 292篇 |
出版年
2024年 | 4篇 |
2023年 | 51篇 |
2022年 | 8篇 |
2021年 | 61篇 |
2020年 | 84篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 6篇 |
2016年 | 42篇 |
2015年 | 59篇 |
2014年 | 26篇 |
2013年 | 55篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 36篇 |
2009年 | 63篇 |
2008年 | 70篇 |
2007年 | 49篇 |
2006年 | 31篇 |
2005年 | 17篇 |
2004年 | 13篇 |
2003年 | 20篇 |
2002年 | 14篇 |
2001年 | 197篇 |
2000年 | 45篇 |
1999年 | 27篇 |
1998年 | 34篇 |
1997年 | 40篇 |
1996年 | 22篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1188条查询结果,搜索用时 78 毫秒
1.
Heiko Drachenfels 《Informatik-Spektrum》1997,20(5):286-293
Eingegangen am 13.11.1996, in überarbeiteter Form am 12.5.1997 相似文献
2.
Arjunan Arulchakkaravarthi Rakesh Kumar Parthasarathy Santhanaraghavan Sivaramakrishnan Muralithar Rengasamy Gopalakrishanan Perumalsamy Ramasamy 《Materials Research Innovations》2002,6(5-6):273-276
Organic molecular scintillating crystals are noted for their good timing and particle discrimination process. Trans-stilbene
is one such candidate noted for its good particle detection characteristics for the past five decades. Progressive strengthening
of detection characteristics of trans-stilbene has been attempted by improving crystal perfection. A series of timing resolution
studies have been carried out for the Bridgman grown trans-stilbene crystals under different experimental conditions. The
results were compared with the previously reported values. Pulse shape discrimination process has been carried out for 241Am and 252Cf sources and good discrimination has been obtained for gamma-alpha and gamma-neutron sources from the grown organic phosphor
crystal.
Electronic Publication 相似文献
3.
4.
Phosphorus modification of ZSM-5 leads to extra framework P5+ and probably incorporation of +3 valence state of P in the framework. The resulting system has increased Brønsted acidity. Theoretical calculations also favour the postulate that phosphorus in +3 valence state can be incorporated into the lattice. 相似文献
5.
Justin H. Dingle Stephen Zimmerman Alexander L. Frie Justin Min Heejung Jung 《Aerosol science and technology》2019,53(4):449-463
Refractive index and optical properties of biogenic and anthropogenic secondary organic aerosol (SOA) particles were investigated. Aerosol precursors, namely longifolene, α-pinene, 1-methylnaphthalene, phenol, and toluene were oxidized in a Teflon chamber to produce SOA particles under different initial hydrocarbon concentrations and hydroxyl radical sources, reflecting exposures to different levels of nitrogen oxides (NOx). The real and imaginary components (n and k, respectively) of the refractive index at 375?nm and 632?nm were determined by Mie theory calculations through an iterative process, using the χ2 function to evaluate the fitness of the predicted optical parameters with the measured scattering, absorption, and extinction coefficients from a Photoacoustic Extinctiometer and Cavity Attenuated Phase Shift Spectrometer. Single scattering albedo (SSA) and bulk mass absorption coefficient (MAC) at 375?nm were calculated. SSA values of SOA particles from biogenic precursors (longifolene and α-pinene) were ~0.98–0.99 (~6.3% uncertainty), reflecting purely scattering aerosols regardless of the NOx regime. However, SOA particles from aromatic precursors were more absorbing and displayed NOx-dependent SSA values. For 1-methylnaphthalene SOA particles, SSA values of 0.92–0.95 and ~0.75–0.90 (~6.1% uncertainty) were observed under intermediate- and high-NOx conditions, respectively, reflecting the absorbing effects of SOA particles and NOx chemistry for this aromatic system. In mixtures of longifolene and phenol or longifolene and toluene SOA under intermediate- and high-NOx conditions, k values of the aromatic-related component of the SOA mixture were higher than that of 1-methylnaphthalene SOA particles. With the increase in OH exposure, kphenol decreased from 0.10 to 0.02 and 0.22 to 0.05 for intermediate- and high-NOx conditions, respectively. A simple relative radiative forcing calculation for urban environments at λ?=?375?nm suggests the influence of absorbing SOA particles on relative radiative forcing at this wavelength is most significant for aerosol sizes greater than 0.4?µm.
Copyright © 2019 American Association for Aerosol Research 相似文献
6.
针对商品化聚乳酸微球粒径分布较宽难于适用气溶胶给药要求的不足,采用水力空化混合强化超临界流体辅助雾化技术(SAA-HCM)制备聚乳酸(PLA)超细微粒.该技术主要特点是通过在超临界流体和液相进料处引入水力空化混合器,强化两相间的混合.考察SAA-HCM过程混合器压力、温度、沉淀器温度、进料中CO2与液体溶液质量流量比和溶液质量浓度等操作参数对微粒形态和粒径分布的影响,成功制备出球形度较好,粒径分布较窄(1~3μm)的PLA微球.经X射线衍射(XRD)分析和差示扫描量热(DSC)分析显示,与原料PLA相比,微球晶型及热曲线变化不大,但结晶度下降.同时把操作参数与相行为进行关联,探讨了影响颗粒形貌的机理.对比超临界流体辅助雾化法(SAA)的实验结果表明:水力空化的引入能有效强化混合器内的两相传质,混合更好,能制备出适用于气溶胶给药要求的超细微粒. 相似文献
7.
Definition of the problem:
Being satisfied with one’s work depends on professional autonomy, which is attributed to the medical profession to a high degree, combined with specialized knowledge and moral authority for vital questions. That is why physicians enjoy a high reputation. At the beginning of a person's medical career, moral competence is developed nearly completely, but specialized knowledge must be learned. Hospitals, in which further medical education regularly takes place, are still traditionally hierarchically organized today. Unfortunately, feudalistic or military structures hinder autonomous moral decisions and cause structural irresponsibility.Arguments:
Obstructions and pressure by superiors, financial restrictions, arrogance and trying to make one's mark are shown in typical conflict situations. Stress, discontent, moral conflicts and illness, even including burn out are possible. Commitment and creativity by employees are prevented and mistakes cannot be constructively managed. Thus, patients may suffer unreasonably or be hurt.Conclusion:
There is a risk to subordinate moral principles under other interests, not only with subordinates but also with superiors. Ways to create a culture that promotes autonomy among physicians and between different professions are discussed. Therefore it is necessary to institutionalize communication based on a reciprocal high regard in a team with people treated as equal partners, who are then able to discuss moral questions in a discourse. 相似文献8.
Jet loop reactors are used as apparatus to facilitate chemical or biological reactions. This type of apparatus is characterized by an internal circulation flow, essentially driven by the injection of liquid. The nozzle can also be used to inject and disperse gas. The internal fluid dynamics and thus the reactor behavior is significantly determined by the introduced momentum and by the internal gas distribution. To describe the mutual influence of a gas-consuming reaction and the internal fluid dynamics, a simplified model based on a momentum balance and a material balance was used. From the exemplary calculations, a critical range for non-selective reactions and for fluid dynamic stability is given. 相似文献
9.
Ralf Habermann 《化学,工程师,技术》2021,93(10):1649-1656
Discontinuous solids mixing processes are largely carried out over the mixing time. The required mixing time is often determined separately in mixing tests. It remains to be seen whether this corresponds to the optimum. There is a lack of models to describe the mixing quality curve over time. The present article adds a simple, two-parameter model that considers not only the homogenization but also the segregation process. In this way, possible mixing quality optima can be approximated with the help of fewer mixing tests that have been carried out. 相似文献
10.
p-y 曲线法是计算分析水平受荷桩常采用的方法。但现场多为 3 m 以内直径试桩,对于海上风电大直径单桩( 4~8 m) 结构的桩土相互作用计算分析,其适用性值得商榷。结合江苏某海上风电大直径钢管桩水平静载荷试验,得到桩身挠度曲线和弯矩曲线; 采用 ABAQUS 建立单桩三维数值模型,将数值模拟结果与试验结果进行了对比分析,并对桩土接触法向刚度进行初步的敏感性分析,验证数值模型的有效性和适用性。随后对大直径单桩进行水平静载数值模拟,与规范推荐的 p-y 曲线法计算结果进行对比,结果表明,规范推荐的 p-y 曲线法过于保守,规范推荐的 p-y 曲线法不适于直接应用在大直径钢管桩的水平承载力分析; 所得结论对该区域海上风电大直径钢管桩设计优化具有指导意义。 相似文献