全文获取类型
收费全文 | 5011篇 |
免费 | 165篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 58篇 |
综合类 | 17篇 |
化学工业 | 925篇 |
金属工艺 | 152篇 |
机械仪表 | 143篇 |
建筑科学 | 259篇 |
矿业工程 | 15篇 |
能源动力 | 153篇 |
轻工业 | 470篇 |
水利工程 | 45篇 |
石油天然气 | 39篇 |
武器工业 | 1篇 |
无线电 | 421篇 |
一般工业技术 | 687篇 |
冶金工业 | 1160篇 |
原子能技术 | 108篇 |
自动化技术 | 540篇 |
出版年
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 49篇 |
2020年 | 38篇 |
2019年 | 45篇 |
2018年 | 66篇 |
2017年 | 74篇 |
2016年 | 75篇 |
2015年 | 78篇 |
2014年 | 99篇 |
2013年 | 293篇 |
2012年 | 181篇 |
2011年 | 274篇 |
2010年 | 217篇 |
2009年 | 202篇 |
2008年 | 263篇 |
2007年 | 273篇 |
2006年 | 248篇 |
2005年 | 184篇 |
2004年 | 156篇 |
2003年 | 144篇 |
2002年 | 118篇 |
2001年 | 86篇 |
2000年 | 84篇 |
1999年 | 121篇 |
1998年 | 188篇 |
1997年 | 124篇 |
1996年 | 102篇 |
1995年 | 100篇 |
1994年 | 104篇 |
1993年 | 95篇 |
1992年 | 82篇 |
1991年 | 53篇 |
1990年 | 62篇 |
1989年 | 62篇 |
1988年 | 65篇 |
1987年 | 77篇 |
1986年 | 54篇 |
1985年 | 73篇 |
1984年 | 74篇 |
1983年 | 57篇 |
1982年 | 39篇 |
1981年 | 47篇 |
1980年 | 27篇 |
1979年 | 44篇 |
1978年 | 23篇 |
1977年 | 38篇 |
1976年 | 35篇 |
1975年 | 21篇 |
1973年 | 14篇 |
排序方式: 共有5193条查询结果,搜索用时 15 毫秒
1.
Argues that while there is potential for successful blending of 12-step approaches and psychotherapies for chemical dependency at the level of helping strategies/techniques, some basic differences in values and philosophy will make it impossible to ever fully integrate the 2 approaches without compromising one or the other approach. Some of the differences between the 2 approaches involve leadership (indigenous vs professional), individual control (increasing vs decreasing), and spirituality (enhanced vs decreased). Given that psychotherapy and the 12-step approach must remain largely independent, a model for interactions based on mutual respect, independent control, and cooperation is suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Ahn Jaeshin Stromsmoe Keith A. Lawson Ronald P. W. 《Industrial Electronics, IEEE Transactions on》1985,(4):405-409
A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films. 相似文献
3.
Dean Gillette 《Information Systems Management》1991,8(2):76-79
As most IS managers know, time is often wasted during most business meetings. As technological advances in the various types of teleconferencing systems continue, teleconferencing will serve as the preferred method of conducting meetings because of the resulting time and cost savings. 相似文献
4.
Dean Gillette 《Information Systems Management》1991,8(4):65-67
Designing a geographically extensive corporate network at the lowest cost means dealing with the vagaries of handling multiple carriers and widely varying levels of service. Further complicating matters are tariff structures that often dictate optimum corporate network infrastructures. This column reviews some of the available and emerging services and the best network structure options. 相似文献
5.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
6.
7.
Two lignite samples, Beulah No. 3 and Big Brown No. 1, were liquefied at 420 °C using H2 and synthesis gas to determine the optimum beneficial amount of H2S in the batch autoclave reactor. Under the conditions employed, 50–100 psi partial pressure of H2S, nominally 4–10 wt% of daf lignite, was optimum for both samples. Synthesis gas outperformed H2 with and without H2S for the liquefaction of the two coals. 相似文献
8.
Modelling the effects of dam removal on migratory walleye (Sander vitreus) early life‐history stages
Many dams in the USA have outlived their intended purpose and an increasing number are being considered for removal. Yet, quantitative studies of the potential physical, biological and ecological responses are needed to assess dam removal decisions. In this paper, the responses of migratory walleye (Sander vitreus) to increased spawning habitat availability as a result of dam removal was studied by comparing scenarios with and without a high‐head dam in the Sandusky River (Ohio), a major tributary to Lake Erie. A conceptual, ecological model was proposed to define the relationship between hydrodynamics and walleye spawning, egg hatching, larval drift and survival. A mathematical, ecological model of the early life‐history stages was then developed and coupled with time series of depth and velocity predictions over the spawning grounds from a 1‐D hydrodynamic model. Model simulations were run for 1984–1993 for both the with‐ and without‐dam scenarios to assess the potential benefit of dam removal. The simulation results demonstrated that velocity, depth and water temperature are major factors influencing adult walleye spawning success. Without the dam, 10 times the amount of spawning habitat would be available for walleye to spawn. This increase in spawning habitat area resulted in up to five times the total egg deposition and seven times the larval output to the nursing grounds, based on the assumption that 5% of the walleye population of Lake Erie migrated up the Sandusky River to spawn. We concluded that the spawning habitat in the current condition (with the dam) is limiting and additional spawning habitat upstream could significantly increase the number of larval walleye drifting to Lake Erie. The model sensitivity analysis showed that the number of walleye migrating up the river in spring is the dominant factor for larval recruitment to the lake. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
9.
10.
Geoffrey Rowden Shirley Dean James Campbell Philip Belitsky 《Microscopy research and technique》1985,2(6):547-555
Aspiration biopsy of tumors and transplanted organs is a popular atraumatic method for diagnosis and also for the management of patients. Apart from the cytological analyses, it is clear that large aggregates of cells are obtained and these may be examined by electron microscopy. A study was carried out with dogs to assess the yield of intact glomeruli and tubules, resulting from a standard fine-needle aspiration procedure. Employing a 20-gauge needle, yields of approximately ten intact glomeruli were obtained with a tissue processing protocol that utilized filtration through a nylon mesh and backwashing, to resuspend the trapped aggregates. Processing for electron microscopy was carried out in microcentrifuge tubes. The ultrastructural preservation was excellent and the extension of these studies to investigations of not only renal transplantation, but also for diagnosis in human renal diseases of a broad spectrum, is suggested. 相似文献