全文获取类型
收费全文 | 1066篇 |
免费 | 2篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 47篇 |
金属工艺 | 5篇 |
机械仪表 | 6篇 |
建筑科学 | 8篇 |
能源动力 | 6篇 |
轻工业 | 44篇 |
水利工程 | 4篇 |
石油天然气 | 25篇 |
无线电 | 47篇 |
一般工业技术 | 31篇 |
冶金工业 | 764篇 |
原子能技术 | 4篇 |
自动化技术 | 69篇 |
出版年
2021年 | 4篇 |
2019年 | 4篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 34篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 30篇 |
1998年 | 242篇 |
1997年 | 138篇 |
1996年 | 96篇 |
1995年 | 56篇 |
1994年 | 40篇 |
1993年 | 48篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 18篇 |
1976年 | 43篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有1068条查询结果,搜索用时 15 毫秒
51.
J Werner C Fernández-del Castillo JA Rivera N Kollias KB Lewandrowski DW Rattner AL Warshaw 《Canadian Metallurgical Quarterly》1998,43(3):401-407
Nucleosome dimers from chicken erythrocytes show an ionic strength dependence of sedimentation coefficient similar to that of trimers, and indicative of a degree of compaction over a range of low ionic strengths. This is not easily reconciled with straight linkers but is consistent with bending or kinking of the linker DNA. 相似文献
52.
H Glover C Ohlde S Silver P Packard P Goodnick CL Hamlin 《Canadian Metallurgical Quarterly》1994,1(2):70-79
Twenty-one antimicrobial agents were incorporated individually into Frey's agar to evaluate their inhibitory activities against 86 isolates of avian mycoplasmas recently detected in Taiwan. Among them, 45 and 37 isolates were found positive with Mycoplasma gallisepticum and Mycoplasma synoviae fluorescent antibody conjugate, respectively. Twenty-one other isolates were unable to be identified by the above 2 conjugates. All of the field isolates were highly sensitive (with MIC50 < 1 microgram/ml) to enrofloxacin, gentamicin, myplabin, tiamutin and tylosin. However, those field isolates were highly resistant (with MIC50 > 32 micrograms/ml) to apramycin, chlortetracycline (CTC), erythromycin (ER), flumequine (FI), nalidixic acid (NA), oxolinic acid (OA), oxytetracycline (OTC) and spiramycin (SP). The inhibitory activities of the antibiotics which possessed an MIC90 of 50 micrograms/ml or less against local isolates were, in decreasing order, enrofloxacin (< 0.004 microgram/ml), gentamicin (1.53 micrograms/ml), tiamutin (1.81 micrograms/ml), tylosin (3.2 micrograms/ml), streptomycin (SM; 12.0 micrograms/ml), colistin (13.1 micrograms/ml), chloramphenicol (14.0 micrograms/ml), spectinomycin (15.0 micrograms/ml), myplabin (16.0 micrograms/ml), spiramycin (30.0 micrograms/ml), minocycline (32.0 micrograms/ml). The MIC90 of OA, CTC, SM, FI, SP, OTC, ER or NA was greater than 50 micrograms/ml; which work poorly in the control of mycoplasmoses. Since the antibiotic control policy is quite loose in Taiwan, many antimicrobial agents are often freely used in clinics, with a resulting gradual decrease in the inhibitory activity to the avian mycoplasmas. 相似文献
53.
Disinfectant surveys from responding members of the American Society of Postanesthesia Nurses were divided into two groups based on whether or not they considered themselves to be exposed to disinfectants in their work environment. Their survey responses were then compared with those obtained previously from members of the Society of Gastroenterology Nurses and Associates, Inc., who were regularly exposed to 2% alkaline glutaraldehyde in the work setting. There were significant differences among the groups in the percentage of respondents who reported having headaches, eye irritations, respiratory problems, shortness of breath, rashes, memory loss, mood swings, and fatigue. These findings support the association of these complaints with 2% alkaline glutaraldehyde exposure. In contrast, there were no significant differences among the groups in the percentage of respondents who reported having asthma, rhinitis, chest pain, nausea, diarrhea, muscle/joint pain, visual disturbances, or dermatitis. 相似文献
54.
Moon-Sun Lin Jay M. Chaffin Meng Liu C.J. Glover R.R. Davison J.A. Bullin 《Petroleum Science and Technology》1996,14(1):139-162
Interactions among asphalt components have significant effects on the performance of asphalt binder. To understand those interactions, four asphalts, SHRP AAA-I, AAD-I, AAF-I, and AAG-I, were fractionated into three generic fractions according to Corbett's procedure and reblended into asphaltenes/aromatics/saturates ternary mixtures in various ratios. Mixtures were oxidatively aged with atmospheric air at temperatures of 87.7, 93.3, and 98.8°C for 5 to 33 days. The changes in chemical composition and physical properties were monitored using fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical rheometry
The formation of asphaltenes is a major factor in the hardening of asphalt with aging. The data collected in this study indicate that the saturate content in the maltene phase has a profound impact on the contribution that asphaltenes have on the viscosity of aged asphalt. The data also suggest that the aromatics fraction is solely responsible for the formation of asphaltenes as an asphalt oxidizes. 相似文献
The formation of asphaltenes is a major factor in the hardening of asphalt with aging. The data collected in this study indicate that the saturate content in the maltene phase has a profound impact on the contribution that asphaltenes have on the viscosity of aged asphalt. The data also suggest that the aromatics fraction is solely responsible for the formation of asphaltenes as an asphalt oxidizes. 相似文献
55.
56.
57.
The effect of an enriched inspired oxygen concentration on perceived exertion (RPE) was investigated while running at two submaximal treadmill loads. Twelve males (VO2 max = 49.3 ml/kg-min) worked at 50% and 80% VO2 max, breathing either air or 80% O2-20% N2 in random order using a single blind technique. Subjects were evaluated while running for 10 min and during a 20 min recovery. Heart rate (HR), ventilation (VE), respiration rate (RR), tidal volume (VT) and RPE were measured before, during and after work. Blood lactate was measured 1 min after work. Oxygen concentration did not statistically affect HR, VE, RR or VT during exercise or recovery. At both loads, RPE at the end of exercise was significantly reduced breathing the hyperoxic mixture. At 50% VO2 max, mean RPE decreased from 11.2 breathing room air to 9.6 breathing 80% O2 and, 80% VO2 max, from 13.8 to 11.7 (P less than 0.01). Blood lactates were significantly reduced breathing 80% O2; from 23.4 mg to 13.3 at 50% VO2 max and from 55.5 to 36.5 at 80% VO2 max (P less than 0.01). The RPE correlated with lactate (r=0.64) at the end of work. Results indicate that during moderate and heavy work RPE is significantly affected by the inspired O2 concentration and there is a significant relationship between RPE and blood lactate. 相似文献
58.
A distinctiveness of encoding hypothesis, as applied to the facilitative effects that higher order objectives appear to have on readers' recall for prose, was evaluated in 3 experiments. Also, the effects of different levels of difficulty of decisions during encoding were examined using an externally referenced difficulty-of-learning task hierarchy. Ss were 253 undergraduates. In a series of identification tasks, decisions about higher order objectives were difficult and resulted in higher levels of recall than did decisions about lower order objectives. Specific controls for processing time, processing ability, and meaningfulness of material did not alter the overall results. It is suggested that distinctiveness of encoding may offer a theoretical basis for the effects of adjunct aids as well as a guide to their construction. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
It is shown that the heat-sink thermal conductance for an annular diode is more than twice that of a circular diode with equal area. Moreover, the annular diode radial temperature distribution at the diode/heat-sink interface is found to be considerably more uniform. 相似文献
60.
Gary?A.?KochenbergerEmail author Fred?Glover Bahram?Alidaee Cesar?Rego 《OR Spectrum》2004,26(2):237-250
Combinatorial optimization problems are often too complex to be solved within reasonable time limits by exact methods, in spite of the theoretical guarantee that such methods will ultimately obtain an optimal solution. Instead, heuristic methods, which do not offer a convergence guarantee, but which have greater flexibility to take advantage of special properties of the search space, are commonly a preferred alternative. The standard procedure is to craft a heuristic method to suit the particular characteristics of the problem at hand, exploiting to the extent possible the structure available. Such tailored methods, however, typically have limited usefulness in other problems domains.An alternative to this problem specific solution approach is a more general methodology that recasts a given problem into a common modeling format, permitting solutions to be derived by a common, rather than tailor-made, heuristic method. Because such general purpose heuristic approaches forego the opportunity to capitalize on domain-specific knowledge, they are characteristically unable to provide the effectiveness or efficiency of special purpose approaches. Indeed, they are typically regarded to have little value except for dealing with small or simple problems.This paper reports on recent work that calls this commonly held view into question. We describe how a particular unified modeling framework, coupled with latest advances in heuristic search methods, makes it possible to solve problems from a wide range of important model classes.Correspondence to: Gary A. Kochenberger.This research was supported in part by ONR grants N000140010598 and N000140310621. 相似文献