全文获取类型
收费全文 | 890篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
综合类 | 4篇 |
化学工业 | 33篇 |
金属工艺 | 7篇 |
机械仪表 | 8篇 |
建筑科学 | 9篇 |
能源动力 | 6篇 |
轻工业 | 17篇 |
水利工程 | 2篇 |
无线电 | 67篇 |
一般工业技术 | 87篇 |
冶金工业 | 493篇 |
原子能技术 | 1篇 |
自动化技术 | 158篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 32篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 8篇 |
2005年 | 17篇 |
2004年 | 23篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 22篇 |
2000年 | 23篇 |
1999年 | 37篇 |
1998年 | 148篇 |
1997年 | 99篇 |
1996年 | 64篇 |
1995年 | 38篇 |
1994年 | 31篇 |
1993年 | 34篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 14篇 |
1976年 | 25篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有901条查询结果,搜索用时 46 毫秒
21.
A practical approach to detect and identify ceftazidime-hydrolyzing extended-spectrum mutants of OXA-10 beta-lactamase is presented. Large numbers of bacteria were screened by colony hybridization, a 720-bp part of blaOXA was amplified by PCR from the hybridization-positive isolates, and the products were digested by PvuII and HaeIII. 相似文献
22.
This study is concerned with investigating the antifungal effects of cement mortar with an organic antifungal agent on the Aspergilus niger which might be easily discovered in the interiors and exteriors of buildings. Two types of organic antifungal agents: isothiazoline/cabamate and nitrofuran, were used in this study for the purpose of investigating the antifungal effect of cement mortar with antifungal agent on the A. niger of various fungus which can be easily discovered in the interiors and exteriors of building. In addition to the investigation of the antifungal effect, the experiment of basic physical properties, such as compressive and flexural strengths, and flow test was carried out. Cement mortar with the antifungal agent of isothiazoline/cabamate exhibited the outstanding antifungal effects but the antifungal agent of nitrofuran did not give the antifungal effects to cement mortar. Although there is a very slight decrease in the strength, it is almost equal to that of cement mortar without antifungal agents. 相似文献
23.
Geetanjali Yadav Leonard A. Fabiano Lindsay Soh Julie Zimmerman Ramkrishna Sen Warren D. Seider 《American Institute of Chemical Engineers》2021,67(1):e16992
Algae-to-biodiesel processes are hindered by high costs and low energy return on investment.1,2. Herein, three foci in research improve algae-to-biodiesel processes by: (1) reducing high installation and energy costs in the CO2 sequestration, cultivation, and harvesting stages; (2) improving oil extraction and biodiesel generation; and (3) increasing utilization of the proteins in lipid-extracted biomass (e.g., for animal feed), as well as the omega-3 fatty acids for nutraceuticals and food supplements. A process is introduced that uses carbon dioxide to aid in all three of these foci. CO2 is used first in the form of microbubbles to lyse algae cell walls, releasing triglyceride oils. CO2 also aids with transesterification of these triglycerides using methanol. At low temperatures (353.15–368.15 K) and intermediate pressures (5–10 MMPa), carbon dioxide causes methanol to dissolve partially in the triglyceride phase and triglyceride to dissolve partially in the methanol phase, increasing the transesterification reaction rate. Due to the nondestructive nature of these processes, other metabolites can also be harvested providing improvements in both mass and economic efficiency with an overall sharp reduction in the modeled price of biodiesel. 相似文献
24.
In cellular networks, QoS degradation or forced termination may occur when there are insufficient resources to accommodate handoff requests. One solution is to predict the trajectory of mobile terminals so as to perform resource reservations in advance. With the vision that future mobile devices are likely to be equipped with reasonably accurate positioning capability, we investigate how this new feature may be used for mobility predictions. We propose a mobility prediction technique that incorporates road topology information, and describe its use for dynamic resource reservation. Simulation results are presented to demonstrate the improvement in reservation efficiency compared with several other schemes. 相似文献
25.
Jin Tang Jialiang Jiang Ning Wang Yaodong Wu Yihao Wang Junbo Li Yona Soh Yimin Xiong Lingyao Kong Shouguo Wang Mingliang Tian Haifeng Du 《Advanced functional materials》2023,33(4):2207770
Magnetic skyrmions are localized particle-like nontrivial swirls that are promising in building high-performance topological spintronic devices. The read-out functions in skyrmionic devices require the translation of magnetic skyrmions to electrical signals. Here, combined real-space magnetic imaging and anisotropic magnetoresistance studies on dipolar skyrmions are reported. A single skyrmion chain and single skyrmion are observed using Lorentz transmission electron microscopy imaging. Meanwhile, the field, helicity, and skyrmion count dependence of anisotropic magnetoresistance of the Fe3Sn2 nanostructures are obtained simultaneously. These results demonstrate that the anisotropic magnetoresistance of skyrmions is independent of the helicity and proportional to the skyrmion count. This study promotes read-out operations in skyrmion-based spintronic devices. 相似文献
26.
JE Greenleaf EM Bernauer LT Juhos HL Young JT Morse RW Staley 《Canadian Metallurgical Quarterly》1977,43(1):126-132
To determine the cause of the body weight loss during bed rest (BR), fluid balance and anthropometric measurements were taken from seven men (19-21 yr) during three 2-wk BR periods which were separated by 3-wk ambulatory recovery periods. Caloric intake was 3,073 +/- 155 (SD) kcal/day. During two of the three BR periods they performed supine isotonic exercise at 68% of VO2max on the ergometer for 1 h/day; or supine isometric exercise at 21% of maximal leg extension force for 1 min followed by a 1-min rest for 1 h/day. No prescribed exercise was given during the other BR period. During BR, body weight decreased slightly with no exercise (-0.43 kg, NS), but decreased significantly (P less than 0.05) by -0.91 kg with isometric and by -1.77 kg with isotonic exercise. About one-third of the weight reduction with isotonic exercise was due to fat loss (-0.69 kg) and, the remainder, to loss of lean body mass (-0.98 kg). It is concluded that the reduction in body weight during bed rest has two major components: First, a loss of lean body mass caused by assumption of the horizontal body position that is independent of the metabolic rate. Second, a loss of body fat content that is proportional to the metabolic rate. 相似文献
27.
Xie Lihua Du Chunling Soh Yeng Chai Zhang Cishen 《Multidimensional Systems and Signal Processing》2002,13(3):265-287
This paper deals with output feedback stabilization and H
control problems for two-dimensional (2-D) discrete linear systems without or with parameter uncertainty. The class of systems under investigation is described by the 2-D local state space Fornasini-Marchesini second model. We aim at designing a dynamical output feedback controller to achieve asymptotic stability and H
performance for the 2-D system. It is shown that the design of output feedback controller can be recast into a convex optimization problem characterized by linear matrix inequalities (LMIs). The LMI solution is further extended to solve the robust stabilization problem for 2-D systems subject to norm-bounded uncertainty. The solutions for the H
control and robust stabilization are applied to two application examples: thermal process control and robust stabilization of processes in Darboux equation. 相似文献
28.
The evidence for and against the prophylactic use of anticonvulsants and antibiotics in head injury is reviewed. There is a lack of blinded placebo-controlled trials in this area. On balance there is no compelling evidence to support the use of either anticonvulsant or antibiotic prophylaxis in head injury, with the possible exception of antibiotic prophylaxis in compound depressed skull fractures and penetrating brain injuries. 相似文献
29.
利用复变函数的保角映射及罗纶级数展开法对在无穷远处受非均匀反平面剪应力场及非均匀平面电位移场作用下的内含螺旋位错和椭圆夹杂的压电材料作了理论分析,给出了映射平面上压电材料基质和夹杂中的解析解形式。 相似文献
30.
Closed laboratories are becoming an increasingly popular approach to teaching introductory computer science courses. Unlike open laboratories that tend to be an informal environment provided for students to practice their skills with attendance optional, closed laboratories are structured meeting times that support the lecture component of the course, and attendance is required. This paper reports on an integrated approach to designing, implementing, and assessing laboratories with an embedded instructional research design. The activities reported here are parts of a departmentwide effort not only to improve student learning in computer science and computer engineering (CE) but also to improve the agility of the Computer Science and Engineering Department in adapting the curriculum to changing technologies, incorporate research, and validate the instructional strategies used. This paper presents the design and implementation of the laboratories and the results and analysis of student performance. Also described in this paper is cooperative learning in the laboratories and its impact on student learning. 相似文献