全文获取类型
收费全文 | 19542篇 |
免费 | 2419篇 |
国内免费 | 1489篇 |
专业分类
电工技术 | 699篇 |
综合类 | 1576篇 |
化学工业 | 1284篇 |
金属工艺 | 1907篇 |
机械仪表 | 1370篇 |
建筑科学 | 1191篇 |
矿业工程 | 314篇 |
能源动力 | 292篇 |
轻工业 | 519篇 |
水利工程 | 247篇 |
石油天然气 | 309篇 |
武器工业 | 190篇 |
无线电 | 2303篇 |
一般工业技术 | 2866篇 |
冶金工业 | 2996篇 |
原子能技术 | 145篇 |
自动化技术 | 5242篇 |
出版年
2024年 | 53篇 |
2023年 | 371篇 |
2022年 | 543篇 |
2021年 | 691篇 |
2020年 | 659篇 |
2019年 | 539篇 |
2018年 | 484篇 |
2017年 | 586篇 |
2016年 | 616篇 |
2015年 | 641篇 |
2014年 | 967篇 |
2013年 | 1096篇 |
2012年 | 1166篇 |
2011年 | 1571篇 |
2010年 | 1214篇 |
2009年 | 1284篇 |
2008年 | 1272篇 |
2007年 | 1423篇 |
2006年 | 1224篇 |
2005年 | 1129篇 |
2004年 | 1008篇 |
2003年 | 851篇 |
2002年 | 737篇 |
2001年 | 616篇 |
2000年 | 424篇 |
1999年 | 359篇 |
1998年 | 296篇 |
1997年 | 274篇 |
1996年 | 232篇 |
1995年 | 217篇 |
1994年 | 176篇 |
1993年 | 142篇 |
1992年 | 109篇 |
1991年 | 66篇 |
1990年 | 71篇 |
1989年 | 67篇 |
1988年 | 54篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1977年 | 11篇 |
1964年 | 6篇 |
1963年 | 6篇 |
1961年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Isabelle Duroux-Richard Jimena Cuenca Clara Ponsolles Alejandro Badilla Pi?eiro Fernando Gonzalez Christine Roubert Roser Areny Rosa Chea Jacqueline Pefaur Yves-Marie Pers Fernando E. Figueroa Christian Jorgensen Maroun Khoury Florence Apparailly 《International journal of molecular sciences》2015,16(8):16953-16965
MicroRNAs control the differentiation and function of B cells, which are considered key elements in the pathogenesis of systemic lupus erythematosus (SLE). However, a common micro(mi)RNA signature has not emerged since published data includes patients of variable ethnic background, type of disease, and organ involvement, as well as heterogeneous cell populations. Here, we aimed at identifying a miRNA signature of purified B cells from renal and non-renal severe SLE patients of Latin American background, a population known to express severe disease. Genome-wide miRNA expression analyses were performed on naive and memory B cells and revealed two categories of miRNA signatures. The first signature represents B cell subset-specific miRNAs deregulated in SLE: 11 and six miRNAs discriminating naive and memory B cells of SLE patients from healthy controls (HC), respectively. Whether the miRNA was up or down-regulated in memory B cells as compared with naive B cells in HC, this difference was abolished in SLE patients, and vice versa. The second signature identifies six miRNAs associated with specific pathologic features affecting renal outcome, providing a further understanding for SLE pathogenesis. Overall, the present work provided promising biomarkers in molecular diagnostics for disease severity as well as potential new targets for therapeutic intervention in SLE. 相似文献
52.
Sam Van Wassenbergh Nuno Zavattieri Potes Dominique Adriaens 《Journal of the Royal Society Interface》2015,12(109)
Presumably as an adaptation for mouthbrooding, many cichlid fish species have evolved a prominent sexual dimorphism in the adult head. Since the head of fishes serves as a bow during locomotion, an evolutionary increase in head volume to brood more eggs can trade-off with the hydrodynamic efficiency of swimming. Here, the differences between males and females in three-dimensional shape and size of the external head surfaces and the effect thereof on drag force during locomotion was analysed for the Nile tilapia (Oreochromis niloticus), a maternal mouthbrooder. To do so, three-dimensional body surface reconstructions from laser scans and computational fluid dynamics simulations were performed. After scaling the scanned specimens to post-cranial body volume, in order to theoretically equalize propulsive power, the external volume of the head of females was 27% larger than that of males (head length + 14%; head width + 9%). These differences resulted in an approximate 15% increase in drag force. Yet, hydrodynamics imposed important constraints on the adaptation for mouthbrooding as a much more drastic drop in swimming efficiency seems avoided by mainly enlarging the head along the swimming direction. 相似文献
53.
《Mechatronics》2015
Tactile display is recently attracting much attention in the field of human–computer interaction. There is a strong need for such a device especially for applications in which the touch feeling is lost, such as surgeons who are willing to feel the tissue hardness during laparoscopic surgeries. In this paper, a novel multi-modal tactile display device which can display both surface shape and stiffness of an object is introduced. The conceptual design is built upon using two springs, made of Shape Memory Alloys (SMA), for displaying shape and stiffness. The design parameters of this device are selected based on the spatial resolution of human finger and the elasticity range of the soft tissue. The display device is simulated using Finite Element Method (FEM) to study the effect of design parameters on the resulting stiffness. Simulation results show that the device can display stiffness of an object independent of its shape display. The experimental setup is built and used for the characterization and control of the SMA springs. Experimental results show that the device can display a stiffness range of (35–110) N/m and elongation up to 5 mm. 相似文献
54.
Consideration of multi‐coil type magnetization system for magnetic particle testing of omnidirectional crack in all surfaces of 3D shape test object 下载免费PDF全文
Katsuhiro Fukuoka Masaki Kobayashi Tomohiro Ozaki Yoshiro Oikawa 《Electrical Engineering in Japan》2018,204(4):36-42
Mechanical parts, plants, and cross‐linkages inspected with magnetic‐particle testing (MT) are typically complex 3D shapes. In complex 3D shape portions, because a magnetizer often cannot be configured to inspection portions and the test object cannot be appropriately magnetized, there is a possibility of overlooking a crack in such an instance. Thus, MT system development that was successfully able to detect omnidirectional cracks in 3D shape portions was considered in this study's trials. Two multi‐coil type magnetizers were hence arranged face‐to‐face, and the magnetization of omnidirectional scenarios for all surfaces of 3D shape test object was evaluated. 相似文献
55.
The deterministic and probabilistic prediction of ship motion is important for safe navigation and stable real-time operational control of ships at sea. However, the volatility and randomness of ship motion, the non-adaptive nature of single predictors and the poor coverage of quantile regression pose serious challenges to uncertainty prediction, making research in this field limited. In this paper, a multi-predictor integration model based on hybrid data preprocessing, reinforcement learning and improved quantile regression neural network (QRNN) is proposed to explore the deterministic and probabilistic prediction of ship pitch motion. To validate the performance of the proposed multi-predictor integrated prediction model, an experimental study is conducted with three sets of actual ship longitudinal motions during sea trials in the South China Sea. The experimental results indicate that the root mean square errors (RMSEs) of the proposed model of deterministic prediction are 0.0254°, 0.0359°, and 0.0188°, respectively. Taking series #2 as an example, the prediction interval coverage probabilities (PICPs) of the proposed model of probability predictions at 90%, 95%, and 99% confidence levels (CLs) are 0.9400, 0.9800, and 1.0000, respectively. This study signifies that the proposed model can provide trusted deterministic predictions and can effectively quantify the uncertainty of ship pitch motion, which has the potential to provide practical support for ship early warning systems. 相似文献
56.
目前,对互联网上虚假健康信息的研究多集中于谣言识别,而对医学信息自动分类的研究较少。采用基于双向编码的语言表征模型和注意力增强的双向长短时记忆模型(BERT-Att-BiLSTM模型),对健康信息文本进行分类,实现自动识别虚假健康信息。实验结果表明,BERT-Att-BiLSTM模型可以高效地对医学信息进行分类,其中BERT模型相较于BiLSTM模型,性能提升明显;与融合Word2Vec的BiLSTM模型相比,BERT-Att-BiLSTM模型效果更佳。 相似文献
57.
表面织构形状对牙轮钻头轴承摩擦学性能影响的实验研究 总被引:2,自引:0,他引:2
牙轮钻头滑动轴承作为钻头破岩过程中传递载荷的关键部件,在低速重载的钻井过程中易发生黏着磨损失效。为改善牙轮钻头滑动轴承的耐磨性能,利用纳秒激光雕刻技术,在牙轮钻头滑动轴承轴颈表面加工了面积比为10%、深度为20μm的圆形、矩形、三角形及复合织构;基于赫兹相似理论,设计近似模拟钻头轴承工况的环-块配对副单元实验方案,并在UMT摩擦试验机上开展织构形状对钻头滑动轴承摩擦副摩擦因数、磨损量、温升变化和微观形貌影响规律的实验研究。结果表明:仿生织构的形状及布置方式对减摩和耐磨效果影响极大,其中圆形、矩形织构的减摩和耐磨性能最优,其次为三角形织构,而复合织构反而增大了摩擦因数及磨损量;单一织构对试件磨损量及温升的影响不大,而复合织构在增加摩擦的同时温度有明显升高,不利于井下高温环境下延长牙轮钻头寿命。 相似文献
58.
广义逆矩阵理论被广泛应用于不稳定结构的形态分析。不稳定结构在荷载作用下,其形状会发生变化直至其势能达到最低,此时的结构处于无弯矩的平衡状态。根据该原理并结合广义逆矩阵理论提出一种适用于杆系结构的形态创构方法。该方法将杆系模型中杆单元进行分组,在每一组中杆单元总长度不变的条件下,建立控制结构形状变化的移形方程。利用广义逆矩阵理论和势能梯度确定使模型势能下降最快的方向,并逐步调整节点位置直至势能达到最低。临时单元和单元组的引入使得该方法可以应用于多种形式结构的形态创构,合理地设置单元组和临时单元可以实现单元长度与单元内力的重新分配进而实现诸多功能。算例分析说明该方法的特性并验证其有效性。 相似文献
59.
介绍了LNG储罐用06Ni9钢板的技术要求。针对生产中06Ni9钢板性能控制、表面质量控制及超极限规格轧制板形控制的难点问题,经试验及现场实践,提出了相应的控制措施,如优化化学成分设计、优化轧制工艺和热处理工艺,保证了钢板的性能;板坯表面喷涂专用防氧化涂料,并配合合理的除鳞工艺,保证了钢板的表面质量;优化坯料、辊型设计,改进模型参数,保证了极限规格钢板的板形质量。在此基础上,太钢成功开发出LNG工程用06Ni9钢板。 相似文献
60.
Xianyou Wu Jing Qian Chao fu Zhongyang Tan Yixing Gao Antong Ma Wei Nie Xianghai Ran 《应用聚合物科学杂志》2020,137(16):48588
In this work, we fabricated a triple-shape memory polymeric material though in situ crosslinking of poly(butylene adipate-co-terephthalate)/ε-polycaprolactone blends induced by electron beam irradiation. The intrinsic property of irradiation crosslinking, crosslinking rule in this heterogeneous system, formation of interfacial bridge molecular, and the resulted interfacial strength were investigated. No obvious interfacial slips were observed in tensile test, and the elongation at break was above 900%. The high-temperature relaxation and recovery experiments at nonlinear region confirmed the excellent hyperelasticity and recovery ratios (Rr ) can be as high as 95% for samples irradiated above 96 kGy. The mismatch between heating rate and relaxation kinetics resulted in both instable temporary shapes and heating-mode dependent recovery behavior during the recovery process. Self-stability of the temporary shape at middle temperature was also emphasized in view of the phenomenon that the second Rr was above 100% in our experiments. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48588. 相似文献