全文获取类型
收费全文 | 4627篇 |
免费 | 55篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 37篇 |
综合类 | 3篇 |
化学工业 | 450篇 |
金属工艺 | 110篇 |
机械仪表 | 57篇 |
建筑科学 | 140篇 |
矿业工程 | 8篇 |
能源动力 | 49篇 |
轻工业 | 294篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
无线电 | 254篇 |
一般工业技术 | 407篇 |
冶金工业 | 2461篇 |
原子能技术 | 27篇 |
自动化技术 | 365篇 |
出版年
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 24篇 |
2017年 | 36篇 |
2016年 | 27篇 |
2015年 | 19篇 |
2014年 | 33篇 |
2013年 | 128篇 |
2012年 | 57篇 |
2011年 | 102篇 |
2010年 | 76篇 |
2009年 | 84篇 |
2008年 | 103篇 |
2007年 | 100篇 |
2006年 | 87篇 |
2005年 | 96篇 |
2004年 | 77篇 |
2003年 | 71篇 |
2002年 | 86篇 |
2001年 | 59篇 |
2000年 | 60篇 |
1999年 | 136篇 |
1998年 | 654篇 |
1997年 | 381篇 |
1996年 | 259篇 |
1995年 | 162篇 |
1994年 | 166篇 |
1993年 | 168篇 |
1992年 | 74篇 |
1991年 | 59篇 |
1990年 | 66篇 |
1989年 | 71篇 |
1988年 | 68篇 |
1987年 | 57篇 |
1986年 | 69篇 |
1985年 | 91篇 |
1984年 | 66篇 |
1983年 | 39篇 |
1982年 | 44篇 |
1981年 | 55篇 |
1980年 | 40篇 |
1979年 | 34篇 |
1978年 | 35篇 |
1977年 | 81篇 |
1976年 | 175篇 |
1975年 | 33篇 |
1974年 | 26篇 |
1973年 | 19篇 |
1972年 | 22篇 |
排序方式: 共有4685条查询结果,搜索用时 15 毫秒
31.
32.
KJ Clark AB Sarr PG Grant TD Phillips GN Woode 《Canadian Metallurgical Quarterly》1998,63(2-4):137-146
Rotaviruses are the leading cause and coronaviruses are the major contributors of acute gastroenteritis in the young of various mammalian and avian species. Despite numerous trials and decades of research, vaccines have limited efficacy particularly for calves. As an alternative method of controlling infection, we have investigated broad spectrum antiviral agents that are not discriminatory among various viruses. This report involves testing a variety of adsorbent agents including charcoal, clay, and clay minerals to adsorb rotavirus and coronavirus in vitro. Results revealed that all the adsorbent agents had good to excellent capability of adsorbing rotavirus and excellent capability of adsorbing coronavirus. Percent adsorptions ranged from 78.74% to 99.89% for rotavirus and 99.99% for coronavirus; while sand (negative control) was < 0.01%. A high affinity binding was present as determined by a low percent desorption (0.06-3.09%). However, the adsorbent bound virus complex retained, and may have actually enhanced, infectivity. 相似文献
33.
During a flight over sea, the right-hand trailing-edge flap (TEF) from an RAAF F/A-18 separated. Although the flap was not recovered, the mode of failure suggested that the outboard hinge lug was first to fail. A fleet-wide inspection of the TEF outer hinge lugs disclosed two other cracked hinge lugs. Examination of these cracks revealed that they had propagated as the result of a combination of corrosion and fatigue, in that the corrosive environment appeared to have accelerated the fatigue crack growth rate. Laboratory experiments indicated that, in a salt solution, the 7050 aluminium alloy from which the lugs were manufactured is susceptible to corrosion fatigue and that the observed cracking matched that on the cracked lugs: corrosion fatigue was therefore suspected to have been a contributing factor in the unexpected failure. Quantitative fractography on the fatigue cracks, combined with several assumptions and deductions, including information about the failure size of the crack gained from witness marks found on the monoball bearing of the failed TEF, led to an estimate of the fatigue crack growth rate. This crack growth rate and the short service life clearly indicated the limitations of the then-current non-destructive inspection (NDI) technique, and a more sensitive inspection method was developed to assist in the maintenance of adequate RAAF flying hours between inspections. This failure investigation provided an excellent example of how fractography, laboratory experiments and NDI can be combined to determine a possible cause of failure and to establish remedial measures for the fleet. 相似文献
34.
Krick R.F. Clark L.T. Deleganes D.J. Wong K.L. Fernando R. Debnath G. Banik J. 《Solid-State Circuits, IEEE Journal of》1994,29(12):1455-1463
An implementation of the Pentium microprocessor architecture in 0.6 μm BiCMOS technology is described. Power dissipation is reduced and performance is enhanced over the previous generation. Processor features, implementation technology, and circuit techniques are discussed. An internal clock rate of 150 MHz is achieved at 3.7 V and -55°C 相似文献
35.
IA Likhtarev GM Gulko IA Kairo K Henrichs HG Paretzke 《Canadian Metallurgical Quarterly》1994,66(2):137-146
In the context of the radiation exposure of the Ukrainian population resulting from the Chernobyl accident, the quantification of the thyroid doses due to iodine incorporation is of special interest. This first part of a series of planned publications deals with the dose and risk estimation for Kiev citizens. Although these doses are expected to be considerably lower than those for some other regions of Ukraine, the investigations started with this population because the quantification of the thyroid doses due to iodine incorporation is of special interest. This first part of a series of planned publications deals with the dose and risk estimation for Kiev citizens. Although these doses are expected to be considerably lower than those for some other regions of Ukraine, the investigations started with this population because of the availability of rather reliable measurements and because of the size of this population. The methods developed allowed the estimation of individual thyroid doses. The average values of individual thyroid doses for five age groups (birth years 1983-1986, 1979-1982, 1975-1978, 1971-1974, and < 1971) are 104, 62, 19, 18, and 41 mGy, respectively. The collective thyroid doses were estimated as 83 x 10(3) person-Gy for those born before 1971 and as 38 x 10(3) person-Gy for younger inhabitants. The numbers of expected thyroid cancers in the whole Kiev population are 66 and 130, respectively. 相似文献
36.
37.
38.
The hierarchies of knowledge and the mathematics of discovery 总被引:1,自引:1,他引:0
Clark Glymour 《Minds and Machines》1991,1(1):75-95
Rather than attempting to characterize a relation of confirmation between evidence and theory, epistemology might better consider which methods of forming conjectures from evidence, or of altering beliefs in the light of evidence, are most reliable for getting to the truth. A logical framework for such a study was constructed in the early 1960s by E. Mark Gold and Hilary Putnam. This essay describes some of the results that have been obtained in that framework and their significance for philosophy of science, artificial intelligence, and for normative epistemology when truth is relative.I am indebted to Kevin Kelly for several years of happy conversation from which the perspective and views of this paper grew, for comments on a draft of the paper, and for constructing some of the illustrations. A fellowship from the John Simon Guggenheim Memorial Foundation provided the liberty to write this paper. It was first presented in the Turing Colloquium, 1990. 相似文献
39.
40.
In this study we have examined (1) the integrated function of the mitochondrial respiratory chain by polarographic measurements and (2) the activities of the respiratory chain complexes I, II-III, and IV as well as the ATP synthase (complex V) in free mitochondria and synaptosomes isolated from gerbil brain, after a 30-min period of graded cerebral ischaemia. These data have been correlated with cerebral blood flow (CBF) values as measured by the hydrogen clearance technique. Integrated functioning of the mitochondrial respiratory chain, using both NAD-linked and FAD-linked substrates, was initially affected at CBF values of approximately 35 ml 100 g-1 min-1, and declined further as the CBF was reduced. The individual mitochondrial respiratory chain complexes, however, showed differences in sensitivity to graded cerebral ischaemia. Complex I activities decreased sharply at blood flows below approximately 30 ml 100 g-1 min-1 (mitochondria and synaptosomes) and complex II-III activities decreased at blood flows below 20 ml 100 g-1 min-1 (mitochondria) and 35-30 ml 100 g-1 min-1 (synaptosomes). Activities declined further as CBF was reduced below these levels. Complex V activity was significantly affected only when the blood flow was reduced below 15-10 ml 100 g-1 min-1 (mitochondria and synaptosomes). In contrast, complex IV activity was unaffected by graded cerebral ischaemia, even at very low CBF levels. 相似文献