全文获取类型
收费全文 | 23731篇 |
免费 | 2483篇 |
国内免费 | 1409篇 |
专业分类
电工技术 | 724篇 |
技术理论 | 6篇 |
综合类 | 3418篇 |
化学工业 | 1562篇 |
金属工艺 | 1812篇 |
机械仪表 | 1445篇 |
建筑科学 | 5592篇 |
矿业工程 | 440篇 |
能源动力 | 280篇 |
轻工业 | 2390篇 |
水利工程 | 860篇 |
石油天然气 | 686篇 |
武器工业 | 132篇 |
无线电 | 1429篇 |
一般工业技术 | 1768篇 |
冶金工业 | 516篇 |
原子能技术 | 113篇 |
自动化技术 | 4450篇 |
出版年
2024年 | 117篇 |
2023年 | 337篇 |
2022年 | 629篇 |
2021年 | 781篇 |
2020年 | 770篇 |
2019年 | 710篇 |
2018年 | 618篇 |
2017年 | 804篇 |
2016年 | 804篇 |
2015年 | 917篇 |
2014年 | 1582篇 |
2013年 | 1394篇 |
2012年 | 1772篇 |
2011年 | 1829篇 |
2010年 | 1504篇 |
2009年 | 1523篇 |
2008年 | 1435篇 |
2007年 | 1715篇 |
2006年 | 1544篇 |
2005年 | 1225篇 |
2004年 | 1100篇 |
2003年 | 865篇 |
2002年 | 658篇 |
2001年 | 560篇 |
2000年 | 477篇 |
1999年 | 400篇 |
1998年 | 316篇 |
1997年 | 259篇 |
1996年 | 193篇 |
1995年 | 156篇 |
1994年 | 135篇 |
1993年 | 102篇 |
1992年 | 72篇 |
1991年 | 60篇 |
1990年 | 80篇 |
1989年 | 48篇 |
1988年 | 38篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mehmet Dorduncu Junuthula Narasimha Reddy 《Journal of Adhesion Science and Technology》2019,33(2):156-186
This study presents an improved mathematical model to analyse the stress wave propagation in adhesively bonded functionally graded (FG) circular cylinders (butt joint) under an axial impulsive load. The volume fractions of the material constituents in the upper and lower cylinders were functionally tailored through the thickness of each cylinder using a power-law. The effective material properties of both cylinders, which are made of aluminum (Al) and silicon carbide (SiC), at any point were predicted by using the Mori–Tanaka homogenization scheme. In this improved model, the governing equations of the wave propagation include the spatial derivatives of local mechanical properties and were discretized by means of the finite difference method. The influence of these spatial derivatives and the compositional gradient exponent on the displacement and stress distributions of the joint was investigated. The material composition variations of both cylinders affected the displacement and stress fields whereas the compositional gradient exponent had a minor effect. The stress concentrations were alleviated in time, the displacement and stress distributions/variations around/along the upper and lower cylinder-adhesive interfaces were significantly affected by the adhesive layer. The spatial derivatives also affected the temporal histories of the displacement and stress components evaluated at the selected critical points of the upper cylinder, adhesive layer and lower cylinder. The consideration of the spatial local material derivatives provided a more accurate mathematical model of wave propagations through the graded layered structures. 相似文献
2.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
3.
Aditi Chatterjee Jayabrata Biswas Kiranmoy Das 《International Journal of Communication Systems》2020,33(9)
In recent years, Internet of Things (IoT) devices are used for remote health monitoring. For remotely monitoring a patient, only the health information at different time points are not sufficient; predicted values of biomarkers (for some future time points) are also important. In this article, we propose a powerful statistical model for an efficient dynamic patient monitoring using wireless sensor nodes through Bayesian Learning (BL). We consider the setting where a set of correlated biomarkers are measured from a patient through wireless sensors, but the sensors only report the ordinal outcomes (say, good, fair, high, or very high) to the sink based on some prefixed thresholds. The challenge is to use the ordinal outcomes for monitoring and predicting the health status of the patient under consideration. We propose a linear mixed model where interbiomarker correlations and intrabiomarker dependence are modeled simultaneously. The estimated and the predicted values of the biomarkers are transferred over the internet so that health care providers and the family members of the patient can remotely monitor the patient. Extensive simulation studies are performed to assess practical usefulness of our proposed joint model, and the performance of the proposed joint model is compared to that of some other traditional models used in the literature. 相似文献
4.
5.
This paper deals with three-dimensional non-linear finite element analyses to assess the structural behavior of adhesively-bonded double supported tee joint of laminated FRP composites having embedded interfacial failures. The onset of interfacial failures is predicted by using Tsai–Wu coupled stress failure criterion with pre-determined stress values. The concept of fracture mechanics principle is utilized to study the sustainability of the tee joint having interfacial failures pre-existed at the critical locations. Individual modes of the strain energy release rates (SERR) GI, GII and GIII, are considered as the damage growth parameters and, are evaluated using the Modified crack closure integral (MCCI) technique based on the concept of linear elastic fracture mechanics (LEFM). Based on the stress analyses, it has been observed that the interfacial failures in tee joint structure trigger at the interface of base plate and adhesive layer from both ends of base plate. Depending on the SERR magnitudes, it has been noticed that the interfacial failure propagates under mixed mode condition. Therefore total SERR (GT) is considered as the governing parameter for damage propagation. Furthermore, efforts have been made to retard damage propagation rate by employing functionally graded adhesive (FGA) instead of monolithic adhesive material. Series of numerical simulations have been performed for varied interfacial failure length in functionally graded adhesively bonded double supported tee joint structure in order to achieve the significant effect of FGA with various modulus ratios on SERR. Material gradation of adhesive indicates significant SERR reduction at the incipient stage of failure which necessitates the use of functionally graded adhesive for the tee joint and prolong the service life of the structure. 相似文献
6.
Li Lin Harry Haoxiang Wang Yuewei Liu Ciyong Lu Weiqing Chen Vivian Yawei Guo 《Indoor air》2021,31(6):2158-2166
A cross-sectional study was conducted to investigate the impact of solid fuel use for heating and cooking on blood pressure (BP) and hypertension, using data from the China Health and Retirement Longitudinal Study (CHARLS). The primary fuels used for indoor heating and cooking were collected by questionnaires, respectively. Hypertension was defined based on self-report of physician's diagnosis, and/or measured BP, and/or anti-hypertensive medication use. Multivariate logistic regression models were constructed to assess the associations. Among 10 450 eligible participants, 68.2% and 57.2% used indoor solid fuel for heating and cooking, respectively. Compared with none/clean fuel users, solid fuel for heating was associated with elevated BP (adjusted β: 2.02, 95% CI: 1.04–3.01 for systolic BP; adjusted β: 1.36, 95% CI: 0.78–1.94 for diastolic BP) and increased risk of hypertension (adjusted odds ratio: 1.15, 95% CI: 1.03–1.29). The impact of indoor solid fuel for heating on BP was more evident in rural and north residents, and hypertensive patients. We did not detect any significant associations between solid fuel use for cooking and BP/hypertension. Indoor solid fuel use is prevalent in China, especially in the rural areas. Its negative impact on BP suggested that modernization of household fuel use may help to reduce the burden of hypertension in China. 相似文献
7.
The Chinese Remainder Theorem (CRT) explains how to estimate an integer-valued number from the knowledge of the remainders obtained by dividing such unknown integer by co-prime integers. As an algebraic theorem, CRT is the basis for several techniques concerning data processing. For instance, considering a single-tone signal whose frequency value is above the sampling rate, the respective peak in the DFT informs the impinging frequency value modulo the sampling rate. CRT is nevertheless sensitive to errors in the remainders, and many efforts have been developed in order to improve its robustness. In this paper, we propose a technique to estimate real-valued numbers by means of CRT, employing for this goal a Kroenecker based M-Estimation (ME), specially suitable for CRT systems with low number of remainders. Since ME schemes are in general computationally expensive, we propose a mapping vector obtained via Kroenecker products which considerably reduces the computational complexity. Furthermore, our proposed technique enhances the probability of estimating an unknown number accurately even when the errors in the remainders surpass 1/4 of the greatest common divisor of all moduli. We also provide a version of the mapping vectors based on tensorial n-mode products, delivering in the end the same information of the original method. Our approach outperforms the state-of-the-art CRT methods not only in terms of percentage of successful estimations but also in terms of smaller average error. 相似文献
8.
Mingzhi Zhao Jianwei Cao Zhi Wang Guohua Li 《Journal of the European Ceramic Society》2019,39(7):2427-2435
The crystallization phenomena of spinel in CaO-MgO-Al2O3-SiO2-Fe2O3 glass have received much attention due to the particular role in preparation of glass-ceramic materials, which represent an effective option to manage hazardous waste. In this study, both preliminary spinel and secondary spinel were precipitated in the precursor glass. The formation of these spinel was meticulously assessed by a combination of X-ray diffractometry and scanning electron microscopy. The structure of the microenvironment in the precursor glass was characterized by Raman spectrums. These advanced techniques highlight the potential for one-step crystallization of the glass. The investigation, which focused on one-step crystallization, demonstrated the growth of pyroxene on spinel accompanying a migration of chromium. The results also show the microstructure of the obtained glass-ceramic was very dependent on the heat-treat temperature. This study not only unambiguously reveals the precipitation mechanisms of spinel but also provides more documentation for one-step crystallization in the glass-ceramics field. 相似文献
9.
基于深度学习的人体姿态估计方法旨在通过构建合适的神经网络,直接从二维的图像特征中回归出人体姿态信息。主要按照2D人体姿态估计到3D人体姿态估计的顺序,并从单人检测与多人检测、稀疏的关节点检测与密集的模型构建等方面,对近年来基于深度学习的人体姿态估计方法进行系统介绍,从而初步了解如何通过深度学习的方法得到人体姿态的各个要素,包括肢体部件的相对朝向和比例尺度、骨骼关节点的位置坐标和连接关系,甚至更为复杂的人体蒙皮模型信息。最后,对当前研究面临的挑战以及未来的热点动向进行概述,清晰地呈现出该领域的发展脉络。 相似文献
10.
针对传统的小区内开环功率控制算法通常以提升本小区的吞吐量性能为目标,忽略了当前小区用户对邻小区用户同频干扰的问题,为提升边缘用户性能的同时兼顾系统整体性能,提出了一种LTE系统小区间上行联合功率控制(UJPC)算法。该算法采用单基站三扇区为系统模型,以最优化系统吞吐量比例公平函数为目标,首先根据最小信干噪比(SINR)约束值和用户最大发射功率这两个约束条件得到相应的数学优化模型,然后采用连续凸近似的方法求解优化问题得出各个基站所管辖的小区内所有用户的最优发射功率。仿真结果表明,与基准的开环功控方案相比,联合功控方案在保证系统平均频谱利用率的情况下能够较大幅度地提高小区边缘频谱利用率,其最佳性能增益能达到50%。 相似文献