全文获取类型
收费全文 | 481篇 |
免费 | 8篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 70篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 21篇 |
能源动力 | 5篇 |
轻工业 | 32篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 29篇 |
一般工业技术 | 56篇 |
冶金工业 | 99篇 |
原子能技术 | 8篇 |
自动化技术 | 158篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 24篇 |
2008年 | 31篇 |
2007年 | 19篇 |
2006年 | 24篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有489条查询结果,搜索用时 15 毫秒
1.
Electronic equivalents of traditional cash payment systems are being launched worldwide. Electronic cash can combine the benefits of traditional cash with those of payment by debit and credit card, while circumventing both their shortcomings. As with traditional cash, electronic cash should have high acceptability and be suitable for low value payment from person to person. With the possible exception of online payment platforms such as the Internet, it is preferred that payments be verifiable offline, without the bank's involvement, for reasons of cost effectiveness and speed. To facilitate electronic cash payments over the phone and the Internet, physical proximity of payer and payee should not be necessary. Moreover, electronic cash should offer privacy of payments. In particular, payments by an honest payer should be untraceable, and information about transaction content should remain privy to payer and payee. Yet a payer ought to always be able to trace the payee; traceability suits electronic cash and is as open to extortion, money laundering, and bribery as a check or wire transfer. Lastly, as with payments by debit and credit card, electronic cash should be convenient to store and transport, while protecting users against loss, theft, and accidental destruction 相似文献
2.
Arie Ben-David 《Expert systems with applications》1991,2(4):353-359
Many expert system researchers have reported in recent years that situation-action symbolic production rules frequently fail to provide adequate knowledge representation schemes without resorting to numeric computation. However, despite the need to integrate symbolic and quantitative computation into one coherent framework of knowledge, surprisingly few architectures have been proposed for achieving this goal. This paper explores the integration of qualitative and numeric processing in expert systems. We address the topic with respect to the construction of expert systems that perform the tasks of design and multiple fault troubleshooting. This paper shows that these tasks can be handled effectively when an appropriate interface is established between the heuristic and the numeric knowledge-based components. Specifically, we demonstrate how to interface heuristic knowledge with non-linear optimization models in order to allow an expert system greater expressiveness. An actual example is presented from the machining domain. 相似文献
3.
Heidi Bernas Arie J. Plomp Johannes H. Bitter Dmitry Yu. Murzin 《Catalysis Letters》2008,120(1-2):8-13
The density functional theory (DFT/B3LYP) calculations were applied to investigate the interaction of a Pt6 particle with the ZSM-5 zeolite framework. The electronic structure of the metal particle is strongly affected by the interaction with basic framework oxygens and acid sites of the zeolite support. Adsorption on basic sites (Eads = 6 kcal/mol) favors the formation of the electron enriched metal cluster. Interaction of the platinum cluster with the acid site characterized by stabilization energy of 47 kcal/mol results in oxidation of the metal particle and suppression of Brønsted acidity of the support. The hypothesis is put forward that the oxidized platinum particle can function as an active site for the alkane isomerisation on platinum supported high silica zeolites. 相似文献
4.
Jost John T.; Glaser Jack; Kruglanski Arie W.; Sulloway Frank J. 《Canadian Metallurgical Quarterly》2003,129(3):383
A meta-analysis by J. T. Jost, J. Glaser, A. W. Kruglanski, and F. J. Sulloway (2003) concluded that political conservatism is partially motivated by the management of uncertainty and threat. In this reply to J. Greenberg and E. Jonas (2003), conceptual issues are clarified, numerous political anomalies are explained, and alleged counterexamples are incorporated with a dynamic model that takes into account differences between "young" and "old" movements. Studies directly pitting the rigidity-of-the-right hypothesis against the ideological extremity hypothesis demonstrate strong support for the former. Medium to large effect sizes describe relations between political conservatism and dogmatism and intolerance of ambiguity; lack of openness to experience; uncertainty avoidance; personal needs for order, structure, and closure; fear of death; and system threat. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
6.
Performance analysis of Drever-Hall laser frequency stabilizationusing a proportional+integral servo
In this paper, we derive analytical expressions for finite gain, finite bandwidth laser frequency locking systems. The common case of Drever-Hall (FM sideband) locking to a Fabry-Perot cavity is discussed, using a proportional+integral (PI) controller as an example. The effects of nonnegligible loop time-delay on stability are discussed, and an optimal design procedure for a frequency locking system is given 相似文献
7.
Natasha M. van Poppelen Jolique A. van Ipenburg Quincy van den Bosch Jolanda Vaarwater Tom Brands Bert Eussen Frank Magielsen Hendrikus J. Dubbink Dion Paridaens Erwin Brosens Nicole Naus Annelies de Klein Emine Kili Robert M. Verdijk 《International journal of molecular sciences》2021,22(11)
The aim of this study was exploration of the genetic background of conjunctival melanoma (CM) and correlation with recurrent and metastatic disease. Twenty-eight CM from the Rotterdam Ocular Melanoma Study group were collected and DNA was isolated from the formalin-fixed paraffin embedded tissue. Targeted next-generation sequencing was performed using a panel covering GNAQ, GNA11, EIF1AX, BAP1, BRAF, NRAS, c-KIT, PTEN, SF3B1, and TERT genes. Recurrences and metastasis were present in eight (29%) and nine (32%) CM cases, respectively. TERT promoter mutations were most common (54%), but BRAF (46%), NRAS (21%), BAP1 (18%), PTEN (14%), c-KIT (7%), and SF3B1 (4%) mutations were also observed. No mutations in GNAQ, GNA11, and EIF1AX were found. None of the mutations was significantly associated with recurrent disease. Presence of a TERT promoter mutation was associated with metastatic disease (p-value = 0.008). Based on our molecular findings, CM comprises a separate entity within melanoma, although there are overlapping molecular features with uveal melanoma, such as the presence of BAP1 and SF3B1 mutations. This warrants careful interpretation of molecular data, in the light of clinical findings. About three quarter of CM contain drug-targetable mutations, and TERT promoter mutations are correlated to metastatic disease in CM. 相似文献
8.
9.
Carl C. Gryte Christopher Koroneos Anil Agarwal Arie Hochberg 《Polymer Engineering and Science》1980,20(7):478-484
Graft copolymers were prepared by irradiation of poly(oxyethylene), PEO, aqueous solutions in presence of acrylic acid. Chain transfer to PEO controls the graft length, the measured chain transfer constant of the acrylic acid radicals to PEO being 4.11 × 10?4 at 25°C. The drag reduction characteristics of the graft copolymers were measured in the Reynolds number range 104–105 in a smooth-walled tube, 0.635 cm inside diameter. The drag reduction falls to near zero as the solution pH is lowered to 3, evidence of the formation of a PEO-poly(acrylic acid) coacervate. 相似文献
10.
The equilibrium stage concept used in staged contacting operations was adopted as a measure of heat transfer efficiency for a fluidized bed. A simple model was developed which postulates that solids flow through the bed can be by perfect mixing, plug flow and short-circuiting. Efficiencies were determined experimentally in a 150 mm diameter fluidized bed with air as the fluidizing medium and sand as the solid. Heat transfer efficiencies greater than 100% were obtained indicating that small diameter, low aspect ratio fluidized beds do not behave as perfect mixers. The results indicate that heat transfer measurements can be used to develop information on solids flow behavior. 相似文献