全文获取类型
收费全文 | 31152篇 |
免费 | 388篇 |
国内免费 | 91篇 |
专业分类
电工技术 | 415篇 |
综合类 | 234篇 |
化学工业 | 5516篇 |
金属工艺 | 664篇 |
机械仪表 | 613篇 |
建筑科学 | 1087篇 |
矿业工程 | 97篇 |
能源动力 | 1026篇 |
轻工业 | 4065篇 |
水利工程 | 276篇 |
石油天然气 | 171篇 |
武器工业 | 7篇 |
无线电 | 2388篇 |
一般工业技术 | 4418篇 |
冶金工业 | 6286篇 |
原子能技术 | 248篇 |
自动化技术 | 4120篇 |
出版年
2024年 | 260篇 |
2023年 | 210篇 |
2022年 | 547篇 |
2021年 | 884篇 |
2020年 | 648篇 |
2019年 | 708篇 |
2018年 | 725篇 |
2017年 | 811篇 |
2016年 | 803篇 |
2015年 | 620篇 |
2014年 | 923篇 |
2013年 | 1507篇 |
2012年 | 1335篇 |
2011年 | 1694篇 |
2010年 | 1228篇 |
2009年 | 1277篇 |
2008年 | 1190篇 |
2007年 | 1039篇 |
2006年 | 839篇 |
2005年 | 872篇 |
2004年 | 930篇 |
2003年 | 832篇 |
2002年 | 813篇 |
2001年 | 711篇 |
2000年 | 552篇 |
1999年 | 556篇 |
1998年 | 2048篇 |
1997年 | 1331篇 |
1996年 | 927篇 |
1995年 | 606篇 |
1994年 | 483篇 |
1993年 | 532篇 |
1992年 | 220篇 |
1991年 | 283篇 |
1990年 | 231篇 |
1989年 | 194篇 |
1988年 | 209篇 |
1987年 | 162篇 |
1986年 | 168篇 |
1985年 | 183篇 |
1984年 | 131篇 |
1983年 | 95篇 |
1982年 | 121篇 |
1981年 | 126篇 |
1980年 | 117篇 |
1979年 | 94篇 |
1978年 | 82篇 |
1977年 | 145篇 |
1976年 | 229篇 |
1975年 | 85篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A study was carried out with a trained panel for the purpose of determining if modifications produced in slaughtered chickens during the storage period, caused significant organoleptic differences, detectable by the consumer. The products examined corresponded to chickens slaughtered on three consecutive days, stored at 2 degrees C until their evaluation. Qualitative aspects in the raw product were investigated by a score test in which optimum quality is 13 points, as follows: for color (range 3), general appearance (range 5), and presence of defects (range 5). The values obtained were then analyzed through variance and Duncan multiple range test. Simultaneously, taste changes were estimated in fatty and meager meat by the triangular test. Homogeneity between judgements of panel members on both types of meat was statistically established (P = 0.05). The results obtained indicate that at the 0.1% level of significance, two products were identical; a third one proved to be different and of a significantly higher quality at the 5% level. The degree of difference, from slight to moderate, was due to flavor. 相似文献
992.
J C Morales de León H Bourges Rodríguez M I Zardain 《Archivos latinoamericanos de nutrición》1985,35(2):326-336
The purpose of this research was to determine adequate conditions for the preparation of soybeans at home level. In accordance with the results, soaking the soybeans for eight hours in a 0.25% bicarbonate solution, gives the appropriate hydration to the soybeans, which can then be easily cooked. Boiling them at atmospheric pressure during 20 minutes was required to destroy 80% of the soybeans antitrypsin activity, and a high PER was also obtained. Nevertheless, the soybeans texture was not satisfactory; therefore, longer boiling periods were tested so as to establish the most suitable time needed to achieve a softness similar to that of common beans as usually consumed. Softness was measured instrumentally, and the optimal conditions found were: 40 min boiling after 8 hr soaking in a 0.25% bicarbonate solution. Under these conditions, the PER and NPU values increased 18% and 33%, respectively, with respect to those of the casein PER and NPU. It is concluded that with this procedure, large amounts of protein can become available at an equivalent price to US$0.40/kg ($80.00/kg). 相似文献
993.
L De Zutter J M De Smedt R Abrams H Beckers M Catteau J de Borchgrave J Debevere J Hoekstra F Jonkers J Lenges 《International journal of food microbiology》1991,13(1):11-20
A collaborative study was performed in 15 laboratories to evaluate the use of motility enrichment on modified semisolid Rappaport-Vassiliadis (MSRV) medium for rapid Salmonella detection in a variety of food products. The results of this procedure were compared with those obtained by the cultural procedure using Rappaport-Vassiliadis (RV) broth as selective enrichment and modified brilliant green agar for selective plating. The tests were performed with Salmonella reference samples (SRS) as well as with naturally contaminated food products. When SRS were used without added food the productivity of both MSRV and RV was 96%. When SRS were combined with reference samples containing competitive bacteria the productivity was 98% for MSRV and 95% for RV. In the tests with food samples the productivity of MSRV was 92% with SRS added to food and 96% with naturally contaminated samples, while the productivity of RV was 88% and 90%, respectively. Statistical analysis showed that there was no significant difference between the procedures. 相似文献
994.
The effects of bST injection and dietary protein level on blood hormone and metabolite concentrations were examined in four mature Holstein cows in a double crossover design. Cows were assigned at d 5 to 9 postpartum to receive daily injections of either a control (saline) solution or 20.6 mg of bST. Four 3-wk periods were used during which one cow from each group was fed a medium protein diet (17.1% CP), and the other received a high protein diet (23.6% CP). Injections of bST or control solutions began on d 0 of the second period. Intakes of DM were not influenced by dietary protein or bST injection. Milk yield tended to increase with increased CP level but was not affected by bST injection. Based on the rate and extent of decline in milk production after cessation of bST injection, the cows assigned to bST had lower milk production potential than control cows. Thus, the effect of bST injection apparently was to enhance milk yield to levels similar to those of controls. There were no significant CP level or bST injection effects on glucose, FFA, somatostatin, or somatotropin concentrations. Glucagon concentrations were higher in bST-treated cows. Concentrations of insulin-like growth factor-I were increased with increased CP level and also with bST injection. Significant effects of days on bST were observed for insulin, insulin-like growth factor-I, glucose, and FFA. Cows given bST injections and producing equal amounts of milk as control cows did not show major physiological differences in hormones and metabolites with the exception of insulin-like growth factor-I. 相似文献
995.
Mércia de Sousa Galvão Narendra NarainMaria do Socorro Porto dos Santos Maria Lúcia Nunes 《Food research international (Ottawa, Ont.)》2011,44(7):1919-1926
The umbu fruit is appreciated in north and northeast region of Brazil mainly because of its refreshing and acidic flavor. The objective of this work was to determine the volatile compounds in half-ripe and ripe stages of umbu fruit and to identify important characteristic compounds which could contribute for its aroma by performing sniffing evaluation of volatile extracts. The principal volatile compounds identified in the ripe umbu fruit pulp were 4-methyl-3-penten-2-one, ethyl benzene, 1-penten-3-one, 2-acetyl thiazone, p-xylene, limonene, 2,2-dimethyl 4-octenal, 3-hexanol, 2-nonanol, 1-nonanol, 2-pentanol, 2-octanol, 3-methylethyl 2-butanoate, butyl benzoate, 3-allyl cyclohexene, 2-acetyl furan, 2-hexyl furan, ??-caryophyllene and methyl pyrazine. A total of 37 volatile compounds were diagnosed with characteristic aroma attributes. The principal volatile compounds which could be responsible for the characteristic aroma of ripe umbu fruit pulp were ??-(Z)-ocimene, methyl pyrazine, 2-butyl-thiophene, methyl octanoate, 2-hexyl furan, 2-octanol, (E)-2-cyclohexen-1-one, 3-bromo-cyclohexene, 1-heptanol, 2-nonanol and 1-octanol. 相似文献
996.
997.
Isadora R. N. de Oliveira Reinaldo F. Teófilo Eduardo B. de Oliveira Afonso M. Ramos Frederico A. R. de Barros Mariza de P. Maia Paulo C. Stringheta 《International Journal of Food Science & Technology》2017,52(2):511-518
The evaluation of the effects of sugars, metals, acids and other antioxidants on the in vitro antioxidant capacity of purified anthocyanin extract by different techniques was the purpose of this study. Three methods and the ways of expressing their results were evaluated: ABTSTEAC (capacity equivalent to Trolox, by ABTS (2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid))), DPPHTEAC (capacity equivalent to Trolox, by DPPH (2,2‐diphenyl‐1‐picrylhydrazyl)), DPPHEC50 (50% reduction in the radical, by DPPH), DPPH%Sca (reduction in the scavenging capacity, by DPPH), FRAPTEAC (capacity equivalent to Trolox, by FRAP (reduction power of iron)) and FRAPEC50 (50% reduction in the radical, by FRAP). The way of expressing DPPH and FRAP results as EC50 showed the greater interfering extent, mainly when the medium contained tartaric and ascorbic acids. The most coherent method was ABTSTEAC in which only ascorbic acid interfered. Ascorbic acid was shown to interfere in all methods; thus, it must be removed prior to determining the in vitro antioxidant capacity of anthocyanins in food materials. 相似文献
998.
999.
E López de la Osa Gonzalez A Novo Dominguez C Chinchilla Calvo J Montalvo Montes 《Canadian Metallurgical Quarterly》1977,181(4):281-287
Seventy five pregnancies where the presence of antepartum meconium was detected by transabdominal amniocentesis, were compared with 224 cases showing clear amniotic fluid (A.F.). The statistical differences were analized in terms of data of anamnesis, diseases complicating pregnancy, gestational age, fetal maturity diagnosis from the A.F. study, oxytocin test, labor characteristics, perinatal mortality and neurologic morbidity during the first nine months of life. The results suggest that the presence of antepartum meconium implies an increase in fetal risk, demanding an adequate analysis of the obstetric solutions, which is discussed. 相似文献
1000.
S Bar-Meir M Topilsky H Kessler J Pinkhas A de Vries 《Canadian Metallurgical Quarterly》1977,71(4):542-544
Amyloidosis was diagnosed in a patient with sarcoidosis. There was no evidence of any other disease known to be associated with amyloidosis. The joint occurrence of amyloidosis and sarcoidosis appears to be extremely rare, and to our knowledge, this is the second such patient to be reported. Whether the association of the two diseases in this patient represents a causal relationship remains an open question. 相似文献