全文获取类型
收费全文 | 3023篇 |
免费 | 145篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 45篇 |
综合类 | 5篇 |
化学工业 | 710篇 |
金属工艺 | 89篇 |
机械仪表 | 96篇 |
建筑科学 | 98篇 |
矿业工程 | 6篇 |
能源动力 | 399篇 |
轻工业 | 269篇 |
水利工程 | 16篇 |
石油天然气 | 60篇 |
无线电 | 256篇 |
一般工业技术 | 567篇 |
冶金工业 | 147篇 |
原子能技术 | 14篇 |
自动化技术 | 415篇 |
出版年
2024年 | 8篇 |
2023年 | 64篇 |
2022年 | 144篇 |
2021年 | 183篇 |
2020年 | 125篇 |
2019年 | 106篇 |
2018年 | 187篇 |
2017年 | 134篇 |
2016年 | 151篇 |
2015年 | 89篇 |
2014年 | 138篇 |
2013年 | 250篇 |
2012年 | 155篇 |
2011年 | 191篇 |
2010年 | 119篇 |
2009年 | 135篇 |
2008年 | 99篇 |
2007年 | 94篇 |
2006年 | 83篇 |
2005年 | 44篇 |
2004年 | 56篇 |
2003年 | 61篇 |
2002年 | 41篇 |
2001年 | 30篇 |
2000年 | 29篇 |
1999年 | 30篇 |
1998年 | 50篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 39篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 11篇 |
排序方式: 共有3192条查询结果,搜索用时 0 毫秒
71.
Siew Hui Voon Lik Voon Kiew Hong Boon Lee Siang Hui Lim Mohamed Ibrahim Noordin Anyanee Kamkaew Kevin Burgess Lip Yong Chung 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(24):4993-5013
Animal models, particularly rodents, are major translational models for evaluating novel anticancer therapeutics. In this review, different types of nanostructure‐based photosensitizers that have advanced into the in vivo evaluation stage for the photodynamic therapy (PDT) of cancer are described. This article focuses on the in vivo efficacies of the nanostructures as delivery agents and as energy transducers for photosensitizers in animal models. These materials are useful in overcoming solubility issues, lack of tumor specificity, and access to tumors deep in healthy tissue. At the end of this article, the opportunities made possible by these multiplexed nanostructure‐based systems are summarized, as well as the considerable challenges associated with obtaining regulatory approval for such materials. The following questions are also addressed: (1) Is there a pressing demand for more nanoparticle materials? (2) What is the prognosis for regulatory approval of nanoparticles to be used in the clinic? 相似文献
72.
Obead Yaseen Maher M. El‐Masri Wasim S. El Nekidy Derrick Soong Mohammed Ibrahim John W. Speirs Albert Kadri 《Hemodialysis international. International Symposium on Home Hemodialysis》2013,17(3):434-440
Hemodialysis catheter (HDC) dysfunction due to thrombosis is common, and dysfunction incidence can reach up to 50% within 1 year of use. Although administration of intraluminal alteplase (tissue plasminogen activator [tPA]) is the standard of practice to pharmacologically restore HDC function, there are no evidence‐based guidelines concerning the optimal tPA dose. The purpose of this study was to compare the efficacy of 1.0‐mg vs. 2.0‐mg tPA dwell protocols in restoring the HDC function in thrombotic dysfunctional catheters. A retrospective, single‐center study was conducted on two independent cohorts of patients; the first (n = 129) received 2.0 mg tPA/catheter lumen, while the second (n = 108) received 1.0 mg tPA/catheter lumen. Kaplan–Meier and Cox regression analyses were performed to compare the catheter survival time between patients who received 1.0 mg tPA and those who received 2.0 mg tPA. Catheter removal occurred in 25 (19.4%) of those catheters treated with 1.0 mg tPA compared with 11 (10.2%) of catheters treated with 2.0 mg tPA (P = 0.05). The hazard ratio (HR) for catheter removal was 2.75 (95% confidence interval [95%CI] = 1.25–6.04) for the 1.0‐mg tPA cohort compared with the 2.0‐mg tPA cohort. Correction added on 3 December 2012, after first online publication: The tPA cohort values were changed. Female gender (HR = 2.51; 95%CI = 1.20–5.27) and age (HR = 0.96; 95%CI = 0.94–0.98) were also associated with catheter survival. Our findings suggest that treatment of dysfunctional HDC with 2.0‐mg tPA dwells is superior to 1.0‐mg tPA dwells. 相似文献
73.
74.
A single-basin solar still was constructed from locally available materials to concentrate palm tree juice (neera) for jaggery-making application. The performance of the still was tested with and without an acrylic mirror booster on both partially cloudy and clear sunshine days. About 73% of water content from neera was evaporated within 2 days by using the mirror booster technique in clear sunshine days. Distilled water of about 7.26 l was extracted from 10 l of neera with the mirror booster condition. Wind velocity showed a considerable effect on neera juice temperature and water vapour temperature during partially cloudy conditions. The calculated efficiency of the still with the mirror booster technique was 36.53% in clear sunshine conditions. The calculated energy conservation for the neera concentration process by using the mirror booster solar still was about 16408 kJ. 相似文献
75.
In wireless sensor network applications where data gathered by different sensor nodes is correlated, not all sensor nodes need to be active for the wireless sensor network to be functional. Given that the sensor nodes that are selected as active form a connected wireless network, the inactive sensor nodes can be turned off. Allowing some sensor nodes to be active and some sensor nodes inactive interchangably during the lifecycle of the application helps the wireless sensor network to have a longer lifetime. The problem of determining a set of active sensor nodes in a correlated data environment for a fully operational wireless sensor network can be formulated as an instance of the connected correlation-dominating set problem. In this work, our contribution is twofold; we propose an effective and runtime-efficient iterative improvement heuristic to solve the active sensor node determination problem, and a benefit function that aims to minimize the number of active sensor nodes while maximizing the residual energy levels of the selected active sensor nodes. Extensive simulations we performed show that the proposed approach achieves a good performance in terms of both network lifetime and runtime efficiency. 相似文献
76.
Ibrahim A. Abbas 《Journal of Mechanical Science and Technology》2014,28(10):4193-4198
The thermoelastic interaction in an unbounded medium with a spherical cavity is studied using two-temperature generalized thermoelasticity theory. The medium is assumed to be initially quiescent. The inner surface of the cavity is taken traction free and subjected to a thermal shock. By the Laplace transformation, the basic equations are expressed in the form of a vector-matrix differential equation, which is solved by an eigenvalue approach. Some comparison have been shown in figures to estimate the effect of the two-temperature parameter. 相似文献
77.
S. Shamsuddin S. N. Supardan Abdel-Baset M. A. Ibrahim A. K. Yahya 《Journal of Superconductivity and Novel Magnetism》2014,27(5):1229-1234
Sr doping in the charge-ordered compound Nd0.3La0.2Ca0.5?x Sr x MnO3 has been systematically studied to examine its effect on ultrasonic velocity and elastic moduli as well as magnetic and electrical transport properties. DC electrical resistivity, ρ and AC susceptibility, χ′ measurements showed all samples exhibit metal-insulator (MI) behavior accompanied by ferromagnetic-paramagnetic (FM-PM) transition where the MI transition temperature, T MI and FM-PM transition temperature, T C increased with Sr content indicating the enhancement of double-exchange mechanism. Analysis of the resistivity change with respect to temperature, dlnρ/dT ?1 versus T indicates onset of charge-ordering (CO) state where its CO transition temperature, T CO decreased with Sr content indicating weakening of the CO state. On the other hand, both absolute longitudinal and shear velocities as well as elastic moduli measured at 80 K increased significantly with Sr doping indicating improvement in elastic properties, which is suggested to be due to the increase in formation of ferromagnetic domains. A longitudinal velocity anomaly characterized by a slope change around the vicinity of T CO was observed for all samples. The longitudinal elastic anomaly is attributed to the Jahn–Teller (JT) effect of Mn3+ ions where analysis of the anomaly using the mean-field theory suggests involvement of the JT effect in the samples, which transforms from dynamic to static type with decreasing temperature. The elastic anomaly shifted down from 222 K (x=0) to 205 K (x=0.05) indicating that the static JT effect was weakened with Sr content. 相似文献
78.
In recent years, the interests of disassembly line have increased owing to economic reasons and the increase of environmental awareness. Effective line can provide many advantages in terms of economic aspect and it facilitates competition the companies with others. This study contributes to the relevant literature by a branch, bound and remember algorithm for disassembly line balancing problem with AND/OR precedence. The proposed exact solution method employs the memory-based dominance rule to eliminate the reduplicated sub-problems by storing all the searched sub-problems and to utilise cyclic best-first search strategy to obtain high-quality complete solutions fast. In this paper, minimising the number of stations is taken as the performance measure. The proposed methodology is tested on a set of 260 instances and compared with the mathematical model using CPLEX solver and five well-known metaheuristics. Computational results show that the proposed method is capable of obtaining the optimal solutions for all the tested instances with less than 0.1?seconds on average. Additionally, comparative study demonstrates that the proposed method is the state-of-the-art algorithm and outperforms the CPLEX solver and metaheuristics in terms of both solution quality and search speed aspects. 相似文献
79.
Motion planning is a fundamental problem in robotics that has motivated research since more than three decades ago. A large variety of algorithms have been proposed to compute feasible motions of multi-body systems in constrained workspaces. In recent years, some of these algorithms have surpassed the frontiers of robotics, finding applications in other domains such as industrial manufacturing, computer animation and computational structural biology. This paper concerns the latter domain, providing a survey on motion planning algorithms applied to molecular modeling and simulation. Both the algorithmic and application sides are discussed, as well as the different issues to be taken into consideration when extending robot motion planning algorithms to deal with molecules. From an algorithmic perspective, the paper gives a general overview of the different extensions to sampling-based motion planners. From the point of view of applications, the survey deals with problems involving protein folding and conformational transitions, as well as protein–ligand interactions. 相似文献
80.