全文获取类型
收费全文 | 707439篇 |
免费 | 28167篇 |
国内免费 | 13743篇 |
专业分类
电工技术 | 25217篇 |
技术理论 | 56篇 |
综合类 | 20034篇 |
化学工业 | 112716篇 |
金属工艺 | 32163篇 |
机械仪表 | 32611篇 |
建筑科学 | 35410篇 |
矿业工程 | 12186篇 |
能源动力 | 20045篇 |
轻工业 | 53993篇 |
水利工程 | 8376篇 |
石油天然气 | 26686篇 |
武器工业 | 2618篇 |
无线电 | 85905篇 |
一般工业技术 | 111832篇 |
冶金工业 | 87078篇 |
原子能技术 | 10109篇 |
自动化技术 | 72314篇 |
出版年
2023年 | 5939篇 |
2022年 | 10614篇 |
2021年 | 15257篇 |
2020年 | 11747篇 |
2019年 | 10514篇 |
2018年 | 13221篇 |
2017年 | 14490篇 |
2016年 | 13597篇 |
2015年 | 15207篇 |
2014年 | 21090篇 |
2013年 | 35926篇 |
2012年 | 28652篇 |
2011年 | 34354篇 |
2010年 | 28741篇 |
2009年 | 29246篇 |
2008年 | 29758篇 |
2007年 | 29241篇 |
2006年 | 28860篇 |
2005年 | 25713篇 |
2004年 | 19683篇 |
2003年 | 18637篇 |
2002年 | 17233篇 |
2001年 | 16994篇 |
2000年 | 16823篇 |
1999年 | 18860篇 |
1998年 | 29831篇 |
1997年 | 22341篇 |
1996年 | 18641篇 |
1995年 | 14887篇 |
1994年 | 13012篇 |
1993年 | 11496篇 |
1992年 | 8868篇 |
1991年 | 8185篇 |
1990年 | 7537篇 |
1989年 | 7019篇 |
1988年 | 6588篇 |
1987年 | 5549篇 |
1986年 | 5296篇 |
1985年 | 5749篇 |
1984年 | 5194篇 |
1983年 | 4927篇 |
1982年 | 4608篇 |
1981年 | 4425篇 |
1980年 | 4217篇 |
1979年 | 4035篇 |
1978年 | 3723篇 |
1977年 | 4496篇 |
1976年 | 5905篇 |
1975年 | 3196篇 |
1974年 | 3032篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Business process redesign (BPR) has been widely touted as a means for leveraging the power of information technology to change business processes radically, resulting in substantial improvements in organizational effectiveness and efficiency. This study represents an early attempt at examining the strategic nature of the phenomenon. Because BPR is radical change and has the ability to alter both the competitive and operational nature of the corporation, it is critical that BPR be coordinated with corporate strategy. Through a survey of information system executives, the relationships between corporate competitive strategy and three types of BPR – intrafunctional, interfunctional and interorganizational – were examined. It was found that organizations following a cost strategy tended to do more BPR projects on interfunctional processes. Furthermore, the positive effect of a cost strategy on interfunctional BPR was found to be strengthened by the degree of integration of IS and business planning. It was also found that while interorganizational BPR was not related to a specific strategy, it was strongly related directly with IS–business planning integration. 相似文献
972.
973.
Munish Agarwal Ali K. Kamrani Hamid R. Parsaei 《Journal of Intelligent Manufacturing》1994,5(4):235-249
The philosophy of group technology (GT) is an important concept in the design of flexible manufacturing systems and manufacturing cells. Group technology is a manufacturing philosophy that identifies similar parts and groups them into families. Beside assigning unique codes to these parts, group technology developers intend to take advantage of part similarities during design and manufacturing processes. GT is not the answer to all manufacturing problems, but it is a good management technique with which to standardize efforts and eliminate duplication. Group technology classifies parts by assigning them to different families based on their similarities in: (1) design attributes (physical shape and size), and/or (2) manufacturing attributes (processing sequence). The manufacturing industry today is process focused; departments and sub units are no longer independent but are interdependent. If the product development process is to be optimized, engineering and manufacturing cannot remain independent any more: they must be coordinated. Each sub-system is a critical component within an integrated manufacturing framework. The coding and classification system is the basis of CAPP and the functioning and reliability of CAPP depends on the robustness of the coding system. The proposed coding system is considered superior to the previously proposed coding systems, in that it has the capability to migrate into multiple manufacturing environments. This article presents the design of a coding and classification system and the supporting database for manufacturing processes based on both design and manufacturing attributes of parts. An interface with the spreadsheet will calculate the machine operation costs for various processes. This menu-driven interactive package is implemented using dBASE-IV. Part Family formation is achieved using a KAMCELL package developed in TURBO Pascal. 相似文献
974.
A value-based test is presented for economic screening of electric utility demand-side management (DSM) programs. The widely used least cost test is valid if the programs do not alter the amount or value of energy services provided to customers. But, in general, DSM programs have such effects and, as a result, the value consumers receive is changed. A more general economic efficiency test, the most value test, provides a practical method for considering the effects of DSM on customer value. The version presented allows for multiple load periods and can account for rate impacts on several customer classes. Four typical DSM programs are evaluated as illustrations 相似文献
975.
The effect of cycloheximide on increased splanchnic prostacyclin release following acute hemorrhage was studied in the rat. Male Sprague-Dawley rats were anesthetized and subjected to acute hemorrhage to 30 mm Hg for 30 min (shock) or sham shock. The superior mesenteric artery was cannulated and removed with its end organ intestine (SV + SI preparation) and perfused in vitro with oxygenated Krebs-Henseleit buffer. Cycloheximide was infused in half of the sham and acute hemorrhage SV + SI preparations at 50 micrograms/ml. Venous effluent from all groups were analyzed for prostanoid release by radioimmunoassay. The SV + SI released 10-fold more 6-keto-prostaglandin (PG) F1 alpha than PGE2 and thromboxane. Acute hemorrhage increased SV + SI release of 6-keto-PGF1 alpha 3-fold compared to sham. Cycloheximide abolished the increased 6-keto-PGF1 alpha following acute hemorrhage but not the basal release in the sham group. Indomethacin decreased PG synthesis in all groups by 90%. Sham PG release was dependent on a stable pool of cyclooxygenase with a long half-life and was not affected by cycloheximide treatment. Acute hemorrhage stimulated a rapid induction of enzymes (cyclooxygenase, prostacyclin synthase) responsible for prostacyclin synthesis and release which were dependent on de novo protein synthesis. 相似文献
976.
977.
Effect of sliding speed on adhesive wear of binary Al-Si alloys 总被引:2,自引:0,他引:2
978.
979.
Over 2000 electrocution deaths were identified among U.S. construction workers from 1980 to 1991, with the highest mean annual crude mortality rate (2.5 per 100,000 people), and second highest mean age-adjusted rate (2.7 per 100,000 people) of all industries. Although the crude fatality rates showed a downward trend, construction workers are still about four times more likely to be electrocuted at work than are workers in all industries combined. Nearly 40% of the 5083 fatal electrocutions in all industries combined occurred in construction, and 80% were associated with industrial wiring, appliances, and transmission lines. Electrocutions ranked as the second leading cause of death among construction workers, accounting for an average of 15% of traumatic deaths in the industry from 1980 to 1991. The study indicates that the workers most at risk of electrical injury are male, young, nonwhite, and electricians, structural metal workers, and laborers. The most likely time of injury is 11 a.m. to 3 p.m. from June to August. Focusing prevention on these populations and characteristics through better methods of worker and supervisor electrical safety training, use of adequate protective clothing, and compliance with established procedures could minimize the average annual loss of 168 U.S. construction workers. 相似文献
980.
The phrase “not much mathematics required” can imply a variety of skill levels. When this phrase is applied to computer scientists, software engineers, and clients in the area of formal specification, the word “much” can be widely misinterpreted with disastrous consequences. A small experiment in reading specifications revealed that students already trained in discrete mathematics and the specification notation performed very poorly; much worse than could reasonably be expected if formal methods proponents are to be believed 相似文献