全文获取类型
收费全文 | 853篇 |
免费 | 52篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 11篇 |
综合类 | 2篇 |
化学工业 | 222篇 |
金属工艺 | 21篇 |
机械仪表 | 23篇 |
建筑科学 | 43篇 |
矿业工程 | 7篇 |
能源动力 | 32篇 |
轻工业 | 75篇 |
水利工程 | 10篇 |
石油天然气 | 5篇 |
无线电 | 96篇 |
一般工业技术 | 169篇 |
冶金工业 | 70篇 |
原子能技术 | 5篇 |
自动化技术 | 118篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 22篇 |
2021年 | 27篇 |
2020年 | 27篇 |
2019年 | 24篇 |
2018年 | 27篇 |
2017年 | 31篇 |
2016年 | 29篇 |
2015年 | 31篇 |
2014年 | 32篇 |
2013年 | 62篇 |
2012年 | 45篇 |
2011年 | 66篇 |
2010年 | 40篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 40篇 |
2006年 | 34篇 |
2005年 | 23篇 |
2004年 | 13篇 |
2003年 | 24篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有909条查询结果,搜索用时 15 毫秒
61.
Jose Andre Morales Peter J. Clarke Yi Deng B. M. Golam Kibria 《Journal in Computer Virology》2006,2(2):135-147
The widespread use of personal digital assistants and smartphones gives securing these devices a high priority. Yet little attention has been placed on protecting handheld devices against viruses. Currently available antivirus software for handhelds is few in number. At this stage, the opportunity exists for the evaluation and improvement of current solutions. By pinpointing weaknesses in the current antivirus software, improvements can be made to properly protect these devices from a future tidal wave of viruses. This research evaluates four currently available antivirus solutions for handheld devices. A formal model of virus transformation that provides transformation traceability is presented. Two sets of ten tests each were administered; nine tests from each set involved the modification of source code of two known viruses for handheld devices. The testing techniques used are well established in PC testing; thus the focus of this research is solely on handheld devices. Statistical analysis of the test results show high false negative production rates for the antivirus software and an overall false negative production rate of 47.5% with a 95% confidence interval between 36.6% and 58.4%. This high rate shows that current solutions poorly identify modified versions of a virus. The virus is left undetected and capable of spreading, infecting and causing damage. 相似文献
62.
F Carreiras V Rigot S Cruet F Andre P Gauduchon J Marvaldi 《Canadian Metallurgical Quarterly》1999,80(2):285-294
Cell migration of ovarian tumoral cells is essential for cell dissemination and for invasion of the submesothelial extracellular matrix (ECM). We have conducted a study of the migratory properties of an ovarian adenocarcinoma cell line (IGROV1) by using 2 distinct methods for the evaluation of cell migration. We found that in a short-term transfilter migration assay, IGROV1 cells migrated toward vitronectin, fibronectin, type IV collagen and laminin in an integrin-dependent manner. When migration was evaluated in a wound healing assay, the restitution of the wounded area was stimulated solely by added, exogenous vitronectin and was almost totally dependent on alpha(v)beta3 integrin function. Moreover, we demonstrated that alpha(v)beta3 was localized in focal contacts restricted to the leading edge of migrating cells, whereas vitronectin notably localized with actin stress fibers and cortical actin. On the other hand, several kinase inhibitors were found to impede migration of IGROV1 induced by vitronectin. It thus appears that alpha(v)beta3-vitronectin interactions lead to the activation of multiple signaling pathway including activation of protein kinase C, phosphatidyl-inositol-3-phosphate kinase and protein tyrosine kinase. The "alpha(v)beta3-vitronectin system" is therefore essential to the migration of human ovarian carcinoma cells. 相似文献
63.
Experimental results concerning the temperature dependence of an m.o.s. field-effect transistor are presented. These results show a striking linear dependence of the temperature coefficient on the gate voltage. Comparison between experiment and simplified theory gives rise to many problems of validity of the theory. 相似文献
64.
The open loop dynamic response of a laboratory scale double effect evaporator has been adequately described by a simple mathematical model based on the unsteady state material and energy balances associated with the various elements of the system. Excellent agreement has been achieved between the experimentally determined response of the evaporator to large disturbances in steam rate and feed rate and the predicted response based on the digital computer solution of the non linear model. 相似文献
65.
66.
The relationship between adiposity and blood pressure has been studied among 17,067 healthy children aged 4 to 18 years old. The correlation of blood pressure with fatness, expressed as non lean body mass, is smaller than the correlation with lean body mass, especially in boys. Blood pressure association with lean body mass strongly increases during puberty growth in boys. These data suggest that during adolescence blood pressure association with weight is mainly due to growth and physical-maturation and that fatness has less influence. A careful analysis of somatic features of adolescents with high blood pressure seems necessary before advocating and improved system of weight control. Preference of blood pressure reference to height is again strengthened. 相似文献
67.
Solid-state and multidimensional solution-state NMR of solid phase extracted and ultrafiltered riverine dissolved organic matter 总被引:1,自引:0,他引:1
Kaiser E Simpson AJ Dria KJ Sulzberger B Hatcher PG 《Environmental science & technology》2003,37(13):2929-2935
In this study we used multidimensional solution-state NMR to elucidate the differences in the chemical composition of solid phase extracted and ultrafiltered DOM isolates. DOM was isolated from water sampled from an oligotrophic river, the River Tagliamento (Italy). The recovery of total DOM was up to 42% with both isolation techniques. In addition to 1- and 2-D solution-state NMR, we also applied 1-D solid-state 13C NMR spectroscopy for DOM characterization. 13C NMR spectroscopy only produced broad overlapping resonances, thus allowing a bulk characterization of DOM composition. However, it demonstrated that the bulk chemical composition of the two DOM fractions exhibited minor spatial-temporal changes. The 2-D experiments (TOCSY, HMQC) showed that the solid phase extracted hydrophobic DOM contained predominantly aliphatic esters, ethers, and hydroxyl groups, whereas the ultrafiltered DOM was comprised partially of peptides/protein, with further evidence for a small amount of aliphatic/fatty acid material. Sugars were present in both DOM fractions. The results show the two isolation techniques selected for different suites of compounds within the bulk DOM pool. 相似文献
68.
69.
Andre N. Klingsheim Veborn Moen Kjell J. Hole 《Computer》2007,40(2):24-30
An increasing number of smart phones support Java 2, Micro Edition. Mobile application developers must deal with J2ME's inherent security weaknesses as well as bugs in implementations on real devices. The new Security and Trust Services API for J2ME addresses some of these challenges, although it too has shortcomings 相似文献
70.
This article addresses process, stamping, and manufacturing engineers, as well as tool designers (prototype and series production tools), and press shop planners in the range of metal forming. The paper deals with methods of modelling and simulating the metal forming process and their application in product design, production, and forming process planning. In models usually applied major effects on the forming process are neglected. For instance, the elastic behaviour of presses and die tools is not considered in process and tool planning. Thus, reworking of tools is a consequence of this model oversimplification. The paper illustrates how interactions between forming press, die tool and metal forming processes can be modelled by enhancing conventional FE models. Several examples demonstrate the information value of the Advanced Forming Process Model (AFPM). 相似文献