全文获取类型
收费全文 | 6836篇 |
免费 | 122篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 55篇 |
综合类 | 19篇 |
化学工业 | 723篇 |
金属工艺 | 67篇 |
机械仪表 | 68篇 |
建筑科学 | 117篇 |
矿业工程 | 19篇 |
能源动力 | 72篇 |
轻工业 | 350篇 |
水利工程 | 30篇 |
石油天然气 | 25篇 |
无线电 | 491篇 |
一般工业技术 | 667篇 |
冶金工业 | 3681篇 |
原子能技术 | 52篇 |
自动化技术 | 534篇 |
出版年
2022年 | 31篇 |
2021年 | 42篇 |
2020年 | 36篇 |
2019年 | 28篇 |
2018年 | 46篇 |
2017年 | 35篇 |
2016年 | 36篇 |
2015年 | 37篇 |
2014年 | 84篇 |
2013年 | 186篇 |
2012年 | 140篇 |
2011年 | 140篇 |
2010年 | 120篇 |
2009年 | 128篇 |
2008年 | 148篇 |
2007年 | 158篇 |
2006年 | 116篇 |
2005年 | 134篇 |
2004年 | 110篇 |
2003年 | 121篇 |
2002年 | 106篇 |
2001年 | 92篇 |
2000年 | 95篇 |
1999年 | 189篇 |
1998年 | 1080篇 |
1997年 | 618篇 |
1996年 | 440篇 |
1995年 | 276篇 |
1994年 | 258篇 |
1993年 | 284篇 |
1992年 | 96篇 |
1991年 | 74篇 |
1990年 | 80篇 |
1989年 | 73篇 |
1988年 | 83篇 |
1987年 | 74篇 |
1986年 | 69篇 |
1985年 | 86篇 |
1984年 | 58篇 |
1983年 | 73篇 |
1982年 | 64篇 |
1981年 | 61篇 |
1980年 | 74篇 |
1979年 | 49篇 |
1978年 | 47篇 |
1977年 | 124篇 |
1976年 | 197篇 |
1975年 | 45篇 |
1973年 | 33篇 |
1972年 | 25篇 |
排序方式: 共有6970条查询结果,搜索用时 15 毫秒
1.
Good requirements practices are neither necessary nor sufficient 总被引:2,自引:2,他引:0
2.
MA Nowak AL Lloyd GM Vasquez TA Wiltrout LM Wahl N Bischofberger J Williams A Kinter AS Fauci VM Hirsch JD Lifson 《Canadian Metallurgical Quarterly》1997,71(10):7518-7525
Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus. 相似文献
3.
In the editorial by J.C. Bezdek (ibid., p.1), an example is presented to demonstrate differences between fuzzy membership and probability. The authors argue that probability can be used in a way much more closely analogous to this use of fuzzy membership, weakening the argument for the latter 相似文献
4.
A. M. J. Davis 《Journal of Engineering Mathematics》1996,30(1-2):239-252
A previously presented method is extended to describe the fully three-dimensional Stokes flow generated by the translation in any direction of an arbitrarily oriented disk in fluid bounded by a plane wall. The velocity field is represented solely in terms of stokeslet distributions on the disk, modified to take account of the bounding wall according to the century-old idea of Lorentz. Sets of integral equations of the second kind, not all disjoint, are obtained for the Abel transforms in each Fourier mode of the density functions. However, only a few modes need be considered in determining the flow field to order D
-3, where D is the distance of the disk axis from the wall. Less detail is required to evaluate the drag force and torque experienced by the disk. 相似文献
5.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents 相似文献
6.
Temperature control offers benefits in land‐based marine aquaculture: stock growth rates may be enhanced by heating in winter; mortality rates in summer may be reduced by cooling. However, if the plant is not well designed, temperature control may create very large energy demands. This paper describes the application of temperature control in abalone aquaculture in New Zealand, with a focus on energy considerations in plant design. An abalone farm using a semi‐closed water conditioning system is used as a case study for which an energy model, based on a heat pump system, is developed. The model is used to determine the impact of plant design and tank conditions on the economics of the operation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
7.
8.
BACKGROUND: There is controversy over whether colonization with drug-resistant organisms is a contraindication to lung transplantation. METHODS: We undertook a retrospective review of the results of lung transplantation for patients with cystic fibrosis (CF) at Duke University Medical Center. RESULTS: As of May 1996, 21 patients with CF underwent bilateral lung transplantation. The first patient died within 24 h of transplantation from sepsis due to Stenotrophomonas maltophilia. Of the remaining 20 patients, 17 (85%) are alive and in stable condition. The three deaths were related primarily to bronchiolitis obliterans at 4 and 18 months in two patients and to cytomegalovirus pneumonitis at 5 months in the other patient. The 17 surviving patients have been followed up for a mean of 13 months (range, 0.5 to 34 months). Most of them were colonized and infected with multidrug-resistant organisms before transplantation. Following transplantation, 11 patients had complications from infections. One patient had bacteremia due to a panresistant Burkholderia cepacia and was treated successfully. Two patients had bacteremia and wound infection due to Burkholderia gladioli, previously thought to be pathogenic only in plants. Both patients were treated successfully. Of the six patients with Aspergillus fumigatus isolated from cultures before transplantation, only one had invasive disease following transplantation and responded to treatment. CONCLUSION: The organisms present before transplantation were not the primary cause of mortality in our patient population. Our findings suggest that lung transplantation should be considered in CF patients infected with multidrug-resistant organisms. 相似文献
9.
10.