全文获取类型
收费全文 | 241275篇 |
免费 | 2627篇 |
国内免费 | 427篇 |
专业分类
电工技术 | 4292篇 |
综合类 | 257篇 |
化学工业 | 39373篇 |
金属工艺 | 9380篇 |
机械仪表 | 7397篇 |
建筑科学 | 5446篇 |
矿业工程 | 1391篇 |
能源动力 | 5153篇 |
轻工业 | 24809篇 |
水利工程 | 2476篇 |
石油天然气 | 5092篇 |
武器工业 | 32篇 |
无线电 | 25044篇 |
一般工业技术 | 44781篇 |
冶金工业 | 45355篇 |
原子能技术 | 5950篇 |
自动化技术 | 18101篇 |
出版年
2021年 | 2110篇 |
2019年 | 2017篇 |
2018年 | 3490篇 |
2017年 | 3425篇 |
2016年 | 3690篇 |
2015年 | 2236篇 |
2014年 | 3900篇 |
2013年 | 10184篇 |
2012年 | 6148篇 |
2011年 | 8299篇 |
2010年 | 6548篇 |
2009年 | 7234篇 |
2008年 | 7583篇 |
2007年 | 7712篇 |
2006年 | 6887篇 |
2005年 | 6046篇 |
2004年 | 5815篇 |
2003年 | 5598篇 |
2002年 | 5673篇 |
2001年 | 5560篇 |
2000年 | 5383篇 |
1999年 | 5303篇 |
1998年 | 12576篇 |
1997年 | 8897篇 |
1996年 | 6857篇 |
1995年 | 5329篇 |
1994年 | 4735篇 |
1993年 | 4625篇 |
1992年 | 3667篇 |
1991年 | 3387篇 |
1990年 | 3593篇 |
1989年 | 3472篇 |
1988年 | 3303篇 |
1987年 | 2895篇 |
1986年 | 2932篇 |
1985年 | 3373篇 |
1984年 | 3219篇 |
1983年 | 2893篇 |
1982年 | 2738篇 |
1981年 | 2821篇 |
1980年 | 2720篇 |
1979年 | 2624篇 |
1978年 | 2684篇 |
1977年 | 2948篇 |
1976年 | 3805篇 |
1975年 | 2368篇 |
1974年 | 2242篇 |
1973年 | 2376篇 |
1972年 | 1970篇 |
1971年 | 1858篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
Participants' usage of informational variables in learning visual relative-mass discrimination in collisions was tracked by means of PROBIT correlations. Four groups received feedback that was true or accorded with either of three nonspecificational cue variables. A majority in each group adopted the feedback, but several participants defied the false feedback. Unlike in previous research, the fit to data of the relative-mass invariant could not be bettered by post hoc linear combinations of the cues. Discriminability was lower in the use of the invariant. Analytic complexity was rejected as an explanation for discriminability differences. A "smart mechanism" for pickup of the relative-mass invariant was developed as an extension of G. Johansson's (1950/1994) vector model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 5, pp. 6–7, May, 1989. 相似文献
994.
L Rudzik E Wüst F J Laven U Marquardt 《Zeitschrift für Lebensmittel-Untersuchung und -Forschung》1987,185(4):271-274
The theory of deconvolution of infra-red spectra is presented and illustrated using milk protein spectra. The advantage of this method is impressively demonstrated and its relevance for dairy farming shown using a simple example, the cooling of milk. 相似文献
995.
Paul W. Angel Chandra S. Ray Delbert E. Day 《Journal of the American Ceramic Society》1986,69(6):134-C
996.
997.
998.
Estrogenic personal care products in a greywater reuse system. 总被引:1,自引:0,他引:1
H R Andersen M Lundsbye H V Wedel E Eriksson A Ledin 《Water science and technology》2007,56(12):45-49
The occurrence and fate of parabens in a greywater system was assessed. The potential for removal of residual paraben concentrations in effluent greywater with chlorine dioxide was also investigated. The influent to the greywater plant was characterised by considerable variation, with concentrations from below the detection limit to 40 microg/L and the five commonly used parabens in consumer products were frequently detected. After the biological treatment only two paraben were detected with concentration from 65-120 ng/L. Chlorine dioxide treatment of the biologically treated effluent with dosages down to 0.75 mg/L resulted in more than 97% reduction of all parabens. Formation of the by-product chloroform was insignificant from the chlorine dioxide treatment. 相似文献
999.
Male weanling rats were subjected to standard 28-day PER trials following the outline by the AOAC (1984) except that the diets contained 8.5% protein (N × 6.25) as one of six wheat-based breakfast cereals, white flour, whole wheat flour or casein. One of the cereals was an extrusion puffed product, three were flaked and toasted cereals and two were extruded cereals. Of the two extruded cereals, one was lightly toasted and the other was more heavily toasted. Relative PER (R-PER) was lowest for the puffed cereal (- 15.3) and highest for the extruded-lightly toasted cereal (69.9). R-PER for the flaked cereals ranged from 1.7 to 16.3; the other extruded cereal had a R-PER of 2.8 and each of the two flours had a R-PER of 42.9. 相似文献
1000.
Bovine growth hormone was administered to eight Holstein cows during two 10-d periods (commencing 20 and 60 d postpartum). Treatments involved daily subcutaneous injection of excipient (control) or of 50 IU growth hormone. Feed intake and yields of milk and milk components were measured during the last 5 d of treatment. In the first injection period, milk yield of treated cows was 6% greater than that of controls (36.2 kg/d). Fat content of milk was increased by treatment with the result that fat yield was elevated by 25%. Protein content was not altered. In the second period, milk yield increased by 12%, but composition of milk was not changed. As a result, milk energy secretion was increased by a similar amount in each treatment period (4.4 versus 4.5 Mcal/d). Feed intake was not changed in either period. During early lactation the ability of cows to increase milk yield in response to exogenous growth hormone may be limited by the supply of glucose for lactose synthesis rather than by ability to mobilize body reserves in support of lactation. 相似文献