全文获取类型
收费全文 | 44131篇 |
免费 | 4029篇 |
国内免费 | 2012篇 |
专业分类
电工技术 | 2479篇 |
技术理论 | 2篇 |
综合类 | 2504篇 |
化学工业 | 7694篇 |
金属工艺 | 2609篇 |
机械仪表 | 2933篇 |
建筑科学 | 3022篇 |
矿业工程 | 1296篇 |
能源动力 | 1278篇 |
轻工业 | 2861篇 |
水利工程 | 648篇 |
石油天然气 | 2480篇 |
武器工业 | 337篇 |
无线电 | 5417篇 |
一般工业技术 | 5984篇 |
冶金工业 | 2476篇 |
原子能技术 | 492篇 |
自动化技术 | 5660篇 |
出版年
2024年 | 245篇 |
2023年 | 878篇 |
2022年 | 1512篇 |
2021年 | 2160篇 |
2020年 | 1575篇 |
2019年 | 1461篇 |
2018年 | 1516篇 |
2017年 | 1549篇 |
2016年 | 1452篇 |
2015年 | 1899篇 |
2014年 | 2266篇 |
2013年 | 2701篇 |
2012年 | 2784篇 |
2011年 | 3163篇 |
2010年 | 2486篇 |
2009年 | 2445篇 |
2008年 | 2461篇 |
2007年 | 2188篇 |
2006年 | 2292篇 |
2005年 | 1840篇 |
2004年 | 1333篇 |
2003年 | 1200篇 |
2002年 | 1125篇 |
2001年 | 984篇 |
2000年 | 949篇 |
1999年 | 996篇 |
1998年 | 836篇 |
1997年 | 714篇 |
1996年 | 633篇 |
1995年 | 526篇 |
1994年 | 408篇 |
1993年 | 278篇 |
1992年 | 228篇 |
1991年 | 206篇 |
1990年 | 169篇 |
1989年 | 155篇 |
1988年 | 101篇 |
1987年 | 88篇 |
1986年 | 57篇 |
1985年 | 51篇 |
1984年 | 37篇 |
1983年 | 37篇 |
1982年 | 29篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 15篇 |
1976年 | 18篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Peer-to-Peer Networking and Applications - 相似文献
12.
13.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
14.
15.
16.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。 相似文献
17.
18.
19.
Thermosetting materials are widely used as encapsulation in the electrical packaging to protect the core electronic components from external force, moisture, dust, and other factors. However, the spreading and curing behaviors of such kind of fluid on a heated surface have been rarely explored. In this study, we experimentally and numerically investigated the spreading and curing behaviors of the silicone(OE6550 A/B, which is widely used in the light-emitting diode packaging) droplet with diameter of ~2.2 mm on a heated surface with temperature ranging from 25 ℃ to 250 ℃. For the experiments, we established a setup with high-speed camera and heating unit to capture the fast spreading process of the silicone droplet on the heated surface. For the numerical simulation, we built a viscosity model of the silicone by using the Kiuna's model and combined the viscosity model with the Volume of Fluid(VOF) model by the User Defined Function(UDF) method. The results show that the surface temperature significantly affected the spreading behaviors of the silicone droplet since it determines the temperature and viscosity distribution inside the droplet. For surface temperature varied from 25 ℃ to 250 ℃, the final contact radius changed from ~2.95 mm to ~1.78 mm and the total spreading time changed from ~511 s to ~0.15 s. By further analyzing the viscosity evolution of the droplet, we found that the decreasing of the total spreading time was caused by the decrease of the viscosity under high surface temperature at initial spreading stage, while the reduction of the final contact radius was caused by the curing of the precursor film. This study supplies a strategy to tuning the spreading and curing behavior of silicone by imposing high surface temperature, which is of great importance to the electronic packaging. 相似文献
20.
Manjunatha S. Muttigi Byoung Ju Kim Bogyu Choi Inbo Han Hansoo Park Soo-Hong Lee 《International journal of molecular sciences》2020,21(23)
Adipose-derived mesenchymal stromal cells (Ad-MSCs) are a promising tool for articular cartilage repair and regeneration. However, the terminal hypertrophic differentiation of Ad-MSC-derived cartilage is a critical barrier during hyaline cartilage regeneration. In this study, we investigated the role of matrilin-3 in preventing Ad-MSC-derived chondrocyte hypertrophy in vitro and in an osteoarthritis (OA) destabilization of the medial meniscus (DMM) model. Methacrylated hyaluron (MAHA) (1%) was used to encapsulate and make scaffolds containing Ad-MSCs and matrilin-3. Subsequently, the encapsulated cells in the scaffolds were differentiated in chondrogenic medium (TGF-β, 1–14 days) and thyroid hormone hypertrophic medium (T3, 15–28 days). The presence of matrilin-3 with Ad-MSCs in the MAHA scaffold significantly increased the chondrogenic marker and decreased the hypertrophy marker mRNA and protein expression. Furthermore, matrilin-3 significantly modified the expression of TGF-β2, BMP-2, and BMP-4. Next, we prepared the OA model and transplanted Ad-MSCs primed with matrilin-3, either as a single-cell suspension or in spheroid form. Safranin-O staining and the OA score suggested that the regenerated cartilage morphology in the matrilin-3-primed Ad-MSC spheroids was similar to the positive control. Furthermore, matrilin-3-primed Ad-MSC spheroids prevented subchondral bone sclerosis in the mouse model. Here, we show that matrilin-3 plays a major role in modulating Ad-MSCs’ therapeutic effect on cartilage regeneration and hypertrophy suppression. 相似文献