全文获取类型
收费全文 | 5940篇 |
免费 | 138篇 |
国内免费 | 126篇 |
专业分类
电工技术 | 247篇 |
综合类 | 259篇 |
化学工业 | 854篇 |
金属工艺 | 243篇 |
机械仪表 | 519篇 |
建筑科学 | 379篇 |
矿业工程 | 510篇 |
能源动力 | 388篇 |
轻工业 | 461篇 |
水利工程 | 64篇 |
石油天然气 | 140篇 |
武器工业 | 38篇 |
无线电 | 258篇 |
一般工业技术 | 400篇 |
冶金工业 | 146篇 |
原子能技术 | 83篇 |
自动化技术 | 1215篇 |
出版年
2024年 | 7篇 |
2023年 | 44篇 |
2022年 | 94篇 |
2021年 | 116篇 |
2020年 | 118篇 |
2019年 | 110篇 |
2018年 | 120篇 |
2017年 | 144篇 |
2016年 | 158篇 |
2015年 | 160篇 |
2014年 | 252篇 |
2013年 | 389篇 |
2012年 | 263篇 |
2011年 | 399篇 |
2010年 | 253篇 |
2009年 | 323篇 |
2008年 | 322篇 |
2007年 | 293篇 |
2006年 | 296篇 |
2005年 | 280篇 |
2004年 | 289篇 |
2003年 | 244篇 |
2002年 | 219篇 |
2001年 | 157篇 |
2000年 | 127篇 |
1999年 | 140篇 |
1998年 | 151篇 |
1997年 | 106篇 |
1996年 | 100篇 |
1995年 | 93篇 |
1994年 | 78篇 |
1993年 | 80篇 |
1992年 | 53篇 |
1991年 | 48篇 |
1990年 | 27篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 25篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有6204条查询结果,搜索用时 15 毫秒
1.
Esperanza González-Redondo 《建筑学研究前沿(英文版)》2022,11(2):255-277
The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector. 相似文献
2.
3.
4.
We report a simple processing method to simultaneously improve the efficiency and stability of organic solar cells (OSCs). Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxy-thiophene (PEDOT:PSS), widely used as hole transport layer (HTL) in OSCs, tends to accelerate the degradation of devices because of its hygroscopic and acidic properties. In this regard, we have modified PEDOT:PSS to reduce its hygroscopic and acidic properties through a condensation reaction between PEDOT:PSS and poly(ethylene glycol) methyl ether (PEGME) in order to improve the efficiency and stability of OSCs. As a result, the power conversion efficiency (PCE) increased by 21%, from 2.57% up to 3.11%. A better energy level alignment by the reduced work function of the modified PEDOT:PSS with a highest occupied molecular orbital (HOMO) level of poly(3-hexylthiophene-2,5-diyl) (P3HT) is considered the origin of the improved the efficiency. The half-life of OSCs with PEDOT:PSS modified with PEGME buffer layer also increased up to 3.5 times compared to that of devices with pristine PEDOT:PSS buffer layer. 相似文献
5.
The paper considers the problem of stabilization of systems possessing a multiple zero eigenvalue at the origin. The controller that we propose, uses multiple delayed measurements instead of derivative terms. Doing so, we increase the performances of the closed loop in presence of system uncertainties and/or noisy measurements. The problem formulation and the analysis is presented through a classical engineering problem which is the stabilization of an inverted pendulum on a cart moving horizontally. On one hand, we perform a nonlinear analysis of the center dynamics described by a three dimensional system of ordinary differential equations with a codimension-three triple zero bifurcation. On the other hand, we present the complementary stability analysis of the corresponding linear time invariant system with two delays describing the behavior around the equilibrium. The aim of this analysis is to characterize the possible local bifurcations. Finally, the proposed control scheme is numerically illustrated and discussed. 相似文献
6.
Gang Zheng Xiaoxuan Yu Haizuo Zhou Xinyu Yang Wei Guo Pengbo Yang 《Geotextiles and Geomembranes》2021,49(1):180-187
Incompressible dipping substrata are commonly encountered in engineering practice. Compared to horizontal underlying strata, the inclined underlying stratum increase the risk of collapse of embankments reinforced with columns because it weakens the restraint of the column base. The objective of this study is to investigate the effectiveness of geosynthetics on improving the embankment stability when the underlying stratum is inclined. The influence of geosynthetic tensile stiffness on the ultimate surcharge and failure mechanism is studied. A deep-seated failure with column tilting occurs when the geosynthetic tensile stiffness is low, whereas a lateral sliding occurs when the geosynthetic tensile stiffness is high. To illustrate the contribution of geosynthetics, the distribution of the lateral pressures acting on the columns is analyzed. 相似文献
7.
This paper proposes an event-triggered distributed receding horizon control (DRHC) approach for the formation and tracking problems of homogeneous multi-agent systems. For each agent, an event-triggering condition, based on assumed predictive information of the neighbours, is derived from stability analysis. Considering the uncertain deviation between the assumed and true predictive information, we design a time-varying compatibility constraint for the individual optimization problem. In the event-triggered DRHC algorithm, each agent solves the optimization problem and communicates with its neighbours only when the event-triggering condition is satisfied, so the communication and computation burden are reduced. Moreover, guarantees for the recursive feasibility and asymptotic stability of the overall system are proved. A simulation example is provided to illustrate effectiveness of the proposed approach. 相似文献
8.
《Ceramics International》2020,46(10):16548-16555
In this article, NiFe2O4 nanoparticles (NPs) were prepared by co-precipitation method with subsequent thermal annealing leading to obtainment NPs with average sizes of 78 nm. Structure and magnetic analysis were performed by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and vibrating sample magnetometry techniques. Stability of NiFe2O4 NPs was evaluated in PBS solution during 20 days. The toxicity of prepared NPs was evaluated in vitro using different cancer cell lines: HeLa (cervical cancer cell), PC-3 (prostate cancer cell). Fibroblasts like cells of L929 obtained from subcutaneous adipose tissue of mouse were used as normal cells. Results indicate successful synthesis of NiFe2O4 NPs that exhibit low cytotoxicity in concentration range from 1 to 100 μg/ml. Presented physical and biological results indicate the possibility of application investigated magnetic nanoparticles in hyperthermia, targeted drug delivery, magnetic resonance imaging or cell separation. 相似文献
9.
10.
Al-10Mg型固溶合金自然时效稳定性研究 总被引:3,自引:0,他引:3
测定了ZL30 5合金自然时效 33年的力学性能变化 ,观察了晶界的析出相 ,研究了组织和性能的关系 ,从而确定了ZL30 5合金具有长期自然时效稳定性。 相似文献