全文获取类型
收费全文 | 412490篇 |
免费 | 44212篇 |
国内免费 | 17251篇 |
专业分类
电工技术 | 22996篇 |
技术理论 | 46篇 |
综合类 | 27361篇 |
化学工业 | 78095篇 |
金属工艺 | 22377篇 |
机械仪表 | 24564篇 |
建筑科学 | 31153篇 |
矿业工程 | 12349篇 |
能源动力 | 11132篇 |
轻工业 | 32805篇 |
水利工程 | 7679篇 |
石油天然气 | 24438篇 |
武器工业 | 3044篇 |
无线电 | 47519篇 |
一般工业技术 | 51361篇 |
冶金工业 | 19864篇 |
原子能技术 | 3963篇 |
自动化技术 | 53207篇 |
出版年
2024年 | 1581篇 |
2023年 | 5898篇 |
2022年 | 10602篇 |
2021年 | 14924篇 |
2020年 | 12345篇 |
2019年 | 11698篇 |
2018年 | 13125篇 |
2017年 | 14698篇 |
2016年 | 14153篇 |
2015年 | 18281篇 |
2014年 | 22019篇 |
2013年 | 26928篇 |
2012年 | 26804篇 |
2011年 | 29004篇 |
2010年 | 26328篇 |
2009年 | 24948篇 |
2008年 | 24074篇 |
2007年 | 23005篇 |
2006年 | 22954篇 |
2005年 | 20061篇 |
2004年 | 14119篇 |
2003年 | 12781篇 |
2002年 | 12038篇 |
2001年 | 10735篇 |
2000年 | 10257篇 |
1999年 | 10151篇 |
1998年 | 7425篇 |
1997年 | 6355篇 |
1996年 | 5970篇 |
1995年 | 4914篇 |
1994年 | 3987篇 |
1993年 | 2697篇 |
1992年 | 2151篇 |
1991年 | 1628篇 |
1990年 | 1270篇 |
1989年 | 1036篇 |
1988年 | 845篇 |
1987年 | 545篇 |
1986年 | 425篇 |
1985年 | 267篇 |
1984年 | 217篇 |
1983年 | 176篇 |
1982年 | 132篇 |
1981年 | 81篇 |
1980年 | 101篇 |
1979年 | 48篇 |
1978年 | 20篇 |
1977年 | 27篇 |
1976年 | 29篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Neural Processing Letters - This paper presents an approach to identify the unknown parameters of genetic regulatory network (GRN) in finite-time. The adaptive synchronization-based method is used... 相似文献
72.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
73.
Xiao-Lei Qiu Zi-Rui Fan Yang-Yang Liu Ding-Fu Wang Shi-Xin Wang Chun-Xia Li 《International journal of molecular sciences》2021,22(8)
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation. 相似文献
74.
Chuncheng Wei Zhen Liu Yun Wu Yeqing Liu Heng Zhang Peng Wang Qiyan Sun Lijuan Zhou 《Ceramics International》2021,47(13):18693-18698
Laminated Si3N4/SiCw ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si3N4/SiCw ceramics was 13.5 MPa m1/2, which was almost 1.6 times that of Si3N4/SiCw composite ceramics, namely 8.5 MPa m1/2. Moreover, the indentation strength of laminated Si3N4/SiCw ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si3N4/SiCw ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si3N4/SiCw ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work. 相似文献
75.
在液化天然气(LNG)接收站工程设计建设过程中,火炬系统的设计是保证LNG接收站安全生产的必要条件。以国内某LNG接收站为例,分析了LNG蒸发气(BOG)产生的因素和机理,及6种工况组合下火炬排放量的计算方法。结果表明:在工况1条件下与实际生产情况吻合良好,其对应的火炬气排放量约为142.7 t/h。在此基础上确定了:BOG支管管径为DN600,BOG总管的管径为DN900;被分离液滴的直径不大于600μm;火炬分液罐尺寸为?2.5 m×8.0 m;电加热器的功率为195 kW;火炬形式为封闭式地面火炬。研究结果可为今后LNG接收站项目火炬系统的处理能力及设备配置提供理论指导。 相似文献
76.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
77.
Hyun Sun Choi Yun Kee Jo Gwang-Noh Ahn Kye Il Joo Dong-Pyo Kim Hyung Joon Cha 《Advanced functional materials》2021,31(46):2104602
The esophagus is a tubular-shaped muscular organ where swallowed fluids and muscular contractions constitute a highly dynamic environment. The turbulent, coordinated processes that occur through the oropharyngeal conduit can often compromise targeted administration of therapeutic drugs to a lesion, significantly reducing therapeutic efficacy. Here, magnetically guidable drug vehicles capable of strongly adhering to target sites using a bioengineered mussel adhesive protein (MAP) to achieve localized delivery of therapeutic drugs against the hydrodynamic physiological conditions are proposed. A suite of highly uniform microparticles embedded with iron oxide (IO) nanoparticles (MAP@IO MPs) is microfluidically fabricated using the genipin-mediated covalent cross-linking of bioengineered MAP. The MAP@IO MPs are successfully targeted to a specific region and prolongedly retained in the tubular-structured passageway. In particular, orally administered MAP@IO MPs are effectively captured in the esophagus in vivo in a magnetically guidable manner. Moreover, doxorubicin (DOX)-loaded MAP@IO MPs exhibit a sustainable DOX release profile, effective anticancer therapeutic activity, and excellent biocompatibility. Thus, the magnetically guidable locomotion and robust underwater adhesive properties of the proteinaceous soft microbots can provide an intelligent modular approach for targeted locoregional therapeutics delivery to a specific lesion site in dynamic fluid-associated tubular organs such as the esophagus. 相似文献
78.
79.
80.