全文获取类型
收费全文 | 3930篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
综合类 | 2篇 |
化学工业 | 162篇 |
金属工艺 | 19篇 |
机械仪表 | 16篇 |
建筑科学 | 58篇 |
矿业工程 | 3篇 |
能源动力 | 25篇 |
轻工业 | 83篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 105篇 |
一般工业技术 | 159篇 |
冶金工业 | 3222篇 |
原子能技术 | 18篇 |
自动化技术 | 65篇 |
出版年
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 35篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 22篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 28篇 |
2005年 | 22篇 |
2004年 | 10篇 |
2003年 | 21篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 110篇 |
1998年 | 905篇 |
1997年 | 503篇 |
1996年 | 337篇 |
1995年 | 205篇 |
1994年 | 146篇 |
1993年 | 215篇 |
1992年 | 44篇 |
1991年 | 54篇 |
1990年 | 46篇 |
1989年 | 67篇 |
1988年 | 53篇 |
1987年 | 54篇 |
1986年 | 54篇 |
1985年 | 53篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 38篇 |
1980年 | 40篇 |
1979年 | 5篇 |
1978年 | 15篇 |
1977年 | 112篇 |
1976年 | 258篇 |
1975年 | 18篇 |
1974年 | 8篇 |
1972年 | 7篇 |
1955年 | 6篇 |
排序方式: 共有3951条查询结果,搜索用时 15 毫秒
1.
H.C. Weigele L. Gygax A. Steiner B. Wechsler J.-B. Burla 《Journal of dairy science》2018,101(3):2370-2382
Lameness is one of the most prevalent diseases affecting the welfare of cows in modern dairy production. Lameness leads to behavioral changes in severely lame cows, which have been investigated in much detail. For early detection of lameness, knowledge of the effects of moderate lameness on cow behavior is crucial. Therefore, the behavior of nonlame and moderately lame cows was compared on 17 Swiss dairy farms. On each farm, 5 to 11 nonlame (locomotion score 1 of 5) and 2 to 7 moderately lame (locomotion score 3 of 5) cows were selected for data collection in two 48-h periods (A, B) separated by an interval of 6 to 10 wk. Based on visual locomotion scoring, 142 nonlame and 66 moderately lame cows were examined in period A and 128 nonlame and 53 moderately lame cows in period B. Between these 2 periods, the cows underwent corrective hoof trimming. Lying behavior, locomotor activity, and neck activity were recorded by accelerometers (MSR145 data logger, MSR Electronics GmbH, Seuzach, Switzerland), and feeding and rumination behaviors by noseband sensors (RumiWatch halter, ITIN + HOCH GmbH, Liestal, Switzerland). Furthermore, visits to the brush and the concentrate feeder, and the milking order position were recorded. In comparison with nonlame cows, moderately lame cows had a longer lying duration, a longer average lying bout duration, and a greater lateral asymmetry in lying duration. Average locomotor activity, locomotor activity during 1 h after feed delivery or push-ups, and average neck activity were lower in moderately lame cows. Eating time and the number of eating chews (jaw movements) were reduced in moderately lame compared with nonlame cows, whereas no effect of moderate lameness was evident for ruminating time, number of ruminating chews and boluses, and average number of ruminating chews per bolus. Moderately lame cows visited the concentrate feeder and the brush less frequently, and they were further back in the milking order compared with nonlame cows. In conclusion, nonlame and moderately lame cows differed in a biologically relevant way in many of the behavioral variables investigated in this study. Therefore, the use of these behavioral changes seems to be promising to develop a tool for early lameness detection. 相似文献
2.
RE Vlietstra 《Canadian Metallurgical Quarterly》1993,16(10):2073-2074
3.
BF Habbick JL Nanson RE Snyder RE Casey AL Schulman 《Canadian Metallurgical Quarterly》1996,87(3):204-207
Ethers and thioethers of monosaccharides have been synthesised which show potent toxicity to mouse (LD50 > or = 4 g.kg-1 O.W. and 0.2 to 1.5 g.kg-1 I.P.W.). A study of calcium antagonist activity for the full series of compounds indicated that the activity was similar for both O- and S- ethers and maximum activities were observed for monoacetoneglucose ethers possessing carbon chain close to 8 carbons. 相似文献
4.
BACKGROUND: IgE-mediated hypersensitivity to latex proteins has become a significant clinical problem over the last decade. Nursing and medical staff are at risk because of their occupational exposure to latex. AIMS: To determine the prevalence of type I hypersensitivity to latex allergens in the nursing staff of an Australian hospital. METHODS: A questionnaire which asked about symptoms associated with the use of latex gloves was completed by 140 nurses working in the Alfred Hospital (72 in general medical wards, 68 in intensive care units). Skin prick tests with eluates of five different types of latex glove as well as common aeroallergens (rye pollen and house dust mite) and banana extract were performed. RESULTS: Thirty-one nurses (22%) were skin prick test positive to at least one of the five latex glove eluates. All of these nurses were atopic, having positive skin prick tests to rye pollen or house dust mite. Symptoms of local dryness, itch and erythema associated with glove use were reported by more than half the study group, but not more frequently by those who were skin prick test positive to latex. Urticaria associated with glove use was reported more frequently by those with positive latex skin prick tests (13% vs 4%, p = 0.05). Eighty-seven per cent of the nurses who were latex skin test positive were also positive to banana extract. CONCLUSIONS: IgE-mediated hypersensitivity to latex is common in nurses working in an Australian hospital. Glove associated symptoms were frequently reported, but in most cases the symptoms were more typical of irritant or contact dermatitis rather than type I hypersensitivity reactions. However, the extent of subclinical sensitisation to latex found in this study suggests that symptomatic latex allergy is likely to emerge as an increasing problem for nursing staff in this country. 相似文献
5.
6.
RE O'Carroll A Moffoot KP Ebmeier C Murray GM Goodwin 《Canadian Metallurgical Quarterly》1993,23(2):341-347
Eighteen patients suffering from Alcoholic Korsakoff's Syndrome participated in a placebo-controlled double-blind cross-over trial of clonidine 0.3 mg b.d. for two weeks versus matched placebo for two weeks. A detailed neuropsychological assessment was carried out at the end of each treatment phase and staff ratings of behaviour were also obtained. Clonidine treatment resulted in no significant improvement over placebo on any of the cognitive measures employed. The results contradict previous smaller studies which had suggested that chronic treatment with clonidine had a memory-enhancing effect in Korsakoff's syndrome. 相似文献
7.
Mitochondrial and cytosolic branched-chain amino acid transaminases from yeast, homologs of the myc oncogene-regulated Eca39 protein 总被引:1,自引:0,他引:1
G Kispal H Steiner DA Court B Rolinski R Lill 《Canadian Metallurgical Quarterly》1996,271(40):24458-24464
We have isolated a high copy suppressor of a temperature-sensitive mutation in ATM1, which codes for an ABC transporter of Saccharomyces cerevisiae mitochondria. The suppressor, termed BAT1, encodes a protein of 393 amino acid residues with an NH2-terminal extension that directs Bat1p to the mitochondrial matrix. A highly homologous protein, Bat2p, of 376 amino acid residues was found in the cytosol. Both Bat proteins show striking similarity to the mammalian protein Eca39, which is one of the few known targets of the myc oncogene. Deletion of a single BAT gene did not impair growth of yeast cells. In contrast, deletion of both genes resulted in an auxotrophy for branched-chain amino acids (Ile, Leu, and Val) and in a severe growth reduction on glucose-containing media, even after supply of these amino acids. Mitochondria and cytosol isolated from bat1 and bat2 deletion mutants, respectively, contained largely reduced activities for the conversion of branched-chain 2-ketoacids to their corresponding amino acids. Thus, the Bat proteins represent the first known isoforms of yeast branched-chain amino acid transaminases. The severe growth defect of the double deletion mutant observed even in the presence of branched-chain amino acids suggests that the Bat proteins, in addition to the supply of these amino acids, perform another important function in the cell. 相似文献
8.
Osvath P. Zingales G. Bartnikas R. Salama M.M.A. von Glahn P. Gulski E. Quinlan J. Steiner J.P. Stone G.C. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1995,2(4):685-699
Some of the more salient aspects of the digital processing technology of PD signals are examined. Most of the efforts in this field are concentrated on the application of digital analyzers for pulse height analysis, pattern recognition and identification of the physical phenomena. It is demonstrated that errors in the signal processing unit can lead to dominant mistakes in the interpretation of the test results 相似文献
9.
The phenotypic characteristics of three Serpulina pilosicoli strains isolated from humans with diarrhoea (WesB, Kar, Hrm7) and two porcine S. pilosicoli strains isolated from pigs with intestinal spirochaetosis (1648, 3295), were compared with the type strain of the species P43/6/78T (T = type strain) and other intestinal spirochaetes within the genus Serpulina. All S. pilosicoli strains had a characteristic ultrastructural appearance, displayed similar growth rates, hydrolysed hippurate, lacked beta-glucosidase activity, utilised D-ribose as a growth substrate, and had similar sensitivities to rifampicin and spiramycin. The only consistent phenotypic characteristic that differentiated human strains from porcine strains of S. pilosicoli was that the human strains all utilised the pentose sugar D-xylose. These distinguishing phenotypic traits appear useful for identifying S. pilosicoli. 相似文献
10.