全文获取类型
收费全文 | 6094篇 |
免费 | 6篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 280篇 |
机械仪表 | 10篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 505篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 23篇 |
一般工业技术 | 58篇 |
冶金工业 | 5168篇 |
原子能技术 | 3篇 |
自动化技术 | 32篇 |
出版年
2013年 | 79篇 |
2011年 | 7篇 |
2009年 | 5篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2000年 | 5篇 |
1999年 | 140篇 |
1998年 | 1531篇 |
1997年 | 868篇 |
1996年 | 586篇 |
1995年 | 340篇 |
1994年 | 314篇 |
1993年 | 333篇 |
1992年 | 58篇 |
1991年 | 102篇 |
1990年 | 75篇 |
1989年 | 100篇 |
1988年 | 107篇 |
1987年 | 100篇 |
1986年 | 93篇 |
1985年 | 58篇 |
1984年 | 26篇 |
1983年 | 33篇 |
1982年 | 46篇 |
1981年 | 48篇 |
1980年 | 67篇 |
1979年 | 25篇 |
1978年 | 50篇 |
1977年 | 162篇 |
1976年 | 364篇 |
1975年 | 40篇 |
1974年 | 27篇 |
1973年 | 26篇 |
1972年 | 29篇 |
1971年 | 28篇 |
1970年 | 23篇 |
1969年 | 13篇 |
1968年 | 10篇 |
1967年 | 11篇 |
1966年 | 11篇 |
1965年 | 14篇 |
1964年 | 11篇 |
1963年 | 8篇 |
1959年 | 6篇 |
1958年 | 8篇 |
1957年 | 5篇 |
1956年 | 10篇 |
1955年 | 7篇 |
排序方式: 共有6100条查询结果,搜索用时 15 毫秒
71.
A lectin-like protein was isolated from L. muta venom by gel filtration on BIO Gel P-100 followed by column Chromatography on DEAE-sephades A-50. The protein eluted at 0.4 M Nacl in 0.01 Tris pH 7.3 and exhibited agglutinin activity toward 0+ human erythrocytes. The protein is a dimer with Mr 28 kDa. Amino acid analysis revealed high content of tryptophan and acid recidues and low content of cysteine and methionine residues. No neutral carbohydrates and sialic acid were detected. Circular dichroic spectrum shows 78% of B structure and 1% of alpha structure. In vitro experiments with erythrocytes from rat, rabbit and dog revealed strong agglutination while red blood cells from mice, sheep and goat were not agglutinated. In vivo experiments using anesthetized rats, a sharp and prolonged fall in the blood pressure was observed at protein dose of 1.5 mg/kg. Double dose of protein caused the death of the animal. 相似文献
72.
SA Syed KS Zahir JR Zink O Saglaam RJ Restifo JG Thomson 《Canadian Metallurgical Quarterly》1997,38(4):396-403
Reinstatement and spontaneous recovery of previously extinguished nicotine-taking behavior were examined in rats. Male subjects were trained to self-administer nicotine (30 microg/kg per infusion, IV; one 60-min session per day for 3 weeks). Extinction sessions were then given for 5-10 days during which saline was substituted for nicotine. Subsequently, in the first set of tests for nicotine seeking, the reinstatement of lever presses that previously delivered nicotine was examined after priming injections of saline and nicotine (75, 150 and 300 microg/kg, SC; and 30 and 60 microg/kg, IV). In the second set of tests for nicotine-seeking, rats were tested after an additional 21-day drug-free period during which they were not exposed to the self-administration chambers (a test for the spontaneous recovery of drug seeking), and after priming injections of nicotine (150 and 300 microg/kg, SC). Reinstatement of extinguished food-reinforced behavior after exposure to nicotine was also determined. Priming injections of nicotine reinstated nicotine seeking regardless of the route of administration. In addition, previously extinguished nicotine seeking recovered spontaneously after a 21-day period during which rats were not exposed to the drug-taking environment. Nicotine also reinstated extinguished food-reinforced behavior in rats with a history of nicotine self-administration, but not in drug-naive rats. The present results extend previous work with opioid and stimulant drugs on reinstatement of drug seeking by the self-administered drug. It also appears that, as with other positive reinforcers, the mere passage of time is a sufficient condition for the spontaneous recovery of extinguished nicotine seeking. 相似文献
73.
BE Gilbert C Knight FG Alvarez C Waldrep JR Rodarte V Knight WL Eschenbacher 《Canadian Metallurgical Quarterly》1997,156(6):1789-1793
Cyclosporine A (CsA) in liposomes of dilauroylphosphatidylcholine (DLPC), containing 118 micrograms of CsA/L of aerosol with a particle size of 1.6 to 1.7 micron diameter, was inhaled by 10 nonsmoking, normal volunteers each for 45 min. Aerosol was administered through an Aerotech II nebulizer (CIS-US, Inc., Bedford, MA) mouthpiece. Eight of the 10 volunteers had tracheal irritation and intermittent coughing following exposure. FEV1 and FVC values were mildly reduced, but returned to normal in 1 h. Blood chemical and hematologic values were unchanged at any time point after as opposed to before inhalation. Nine of the 10 volunteers later inhaled DLPC only, administered through the nebulizer mouthpiece. There was no change in FEV1 or FVC values, and there was no coughing or tracheal irritation. Subsequently, five of the volunteers who had previously had respiratory reactions inhaled CsA-DLPC liposome aerosol for 45-min, but through a mouth-only face mask. There was no tracheal irritation, coughing, or changes in spirometric measures. Blood concentrations of CsA at 15 min after the 45-min inhalation with a face mask averaged 83 +/- 42 ng/ml (mean +/- SD). At 24 h after treatment, CsA was undetectable in blood of the initial 10 volunteers. These studies indicate that CsA-DLPC liposome aerosol can be safely explored as a treatment for patients with moderately severe asthma. 相似文献
74.
75.
JR Naranjo B Mellstr?m AM Carrión JJ Lucas NS Foulkes P Sassone-Corsi 《Canadian Metallurgical Quarterly》1997,9(12):2778-2783
Thermal washout curves have been proposed as noninvasive tools for analysing lower airway dimensions and pulmonary blood flow, but how upper airway heat transfer affects these washout curves is unclear. The present study was designed to compare extrathoracic and tracheobronchial contributions to thermal washout curves. Respiratory frequency, air ambient temperature, and body core temperature (tc) were varied in six male subjects before and after immersion in cold (1.1 degrees C) water for up to 2 h under three conditions: 1) control: ambient temperature (tamb) = 25 degrees C, rectal temperature change (delta tre) = 0 degrees C; 2) pre-immersion: tamb = 4 degrees C, delta tre = 0 degrees C; and 3) post-immersion: tamb = 25 degrees C, delta tre = -0.7 degrees C. Both peak expiratory nasal (tpn) and oral (tpo) airstream temperatures were measured. Each subject was tested twice. Expiratory tpo was generally higher than tpn in all conditions. Increasing breathing rates lowered tpn and tpo in the control and cold air environments. Orifice temperatures, which are presumed to reflect upper airway blood temperatures, correlated with both tpn and tpo. Lowering tc had no effect on washout curves during quiet breathing and affected only tpn during rapid breathing. The results suggest that while tracheobronchial conditions may contribute to thermal washout curves, extrathoracic conditions predominate. Strong correlations between orifice temperatures, peak expiratory nasal temperatures and peak expiratory oral temperature demonstrate the dominant role of upper airway heat exchange in determining thermal washout curves. 相似文献
76.
77.
78.
79.
Lactic Acid Concentration and Microbial Spoilage in Anaerobically and Aerobically Stored Ground Beef 总被引:2,自引:0,他引:2
PATRICIA S. NASSOS A. DOUGLAS KING JR. ALLAN E. STAFFORD 《Journal of food science》1985,50(3):710-712
Lactic acid concentration of coarsely ground beef, packaged in low oxygen permeability casings, is inversely related to sensory acceptability of the meat following regrinding and aerobic storage for six additional days. Samples, reground and stored aerobically after periods of anaerobic storage, were assayed for total aerobic bacterial counts, percentage of gram-positive microflora, and pH. Lactic acid concentration ranged from 130 to 1055 mg per 100g ground beef and increased with anaerobic storage. During 6 days of aerobic storage, both increases and decreases in concentration were noted and related to changes in microbial flora. A positive correlation was found between the proportion of gram-positive bacteria (lactic acid bacteria) and lactic acid and pH. 相似文献
80.