全文获取类型
收费全文 | 6737篇 |
免费 | 35篇 |
专业分类
电工技术 | 9篇 |
综合类 | 8篇 |
化学工业 | 395篇 |
金属工艺 | 13篇 |
机械仪表 | 26篇 |
建筑科学 | 42篇 |
矿业工程 | 6篇 |
能源动力 | 18篇 |
轻工业 | 582篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 74篇 |
一般工业技术 | 164篇 |
冶金工业 | 5323篇 |
原子能技术 | 6篇 |
自动化技术 | 89篇 |
出版年
2018年 | 18篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 25篇 |
2013年 | 105篇 |
2012年 | 30篇 |
2011年 | 36篇 |
2010年 | 25篇 |
2009年 | 29篇 |
2008年 | 29篇 |
2007年 | 28篇 |
2006年 | 19篇 |
2005年 | 16篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2000年 | 17篇 |
1999年 | 155篇 |
1998年 | 1579篇 |
1997年 | 890篇 |
1996年 | 617篇 |
1995年 | 351篇 |
1994年 | 328篇 |
1993年 | 343篇 |
1992年 | 63篇 |
1991年 | 118篇 |
1990年 | 83篇 |
1989年 | 104篇 |
1988年 | 114篇 |
1987年 | 102篇 |
1986年 | 96篇 |
1985年 | 61篇 |
1984年 | 35篇 |
1983年 | 37篇 |
1982年 | 53篇 |
1981年 | 50篇 |
1980年 | 73篇 |
1979年 | 29篇 |
1978年 | 58篇 |
1977年 | 169篇 |
1976年 | 371篇 |
1975年 | 45篇 |
1974年 | 25篇 |
1973年 | 25篇 |
1972年 | 32篇 |
1971年 | 31篇 |
1970年 | 26篇 |
1968年 | 15篇 |
1967年 | 16篇 |
1965年 | 14篇 |
排序方式: 共有6772条查询结果,搜索用时 15 毫秒
81.
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
82.
83.
84.
85.
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
86.
87.
88.
89.
90.
JR Woods 《Canadian Metallurgical Quarterly》1996,8(6):403-411
Our appreciation of the impact on health of illicit drug use is growing. Once considered a maternal risk, prenatal drug exposure may target fetal neurobehavior, affecting attention and learning as the child grows into adulthood. Cocaine, opiates, marijuana, and amphetamines have each been scrutinized for adverse actions on placental transport, fetal behavior states, newborn withdrawal, and childhood learning and attentive skills. Neurotransmitter analysis in the animal model after prenatal drug exposure now provides biological support for these clinical findings. The increasing prevalence of drug use by pregnant women, the effect of illicit drug use on transmission of the human immunodeficiency virus, and the maternal and fetal consequences of illicit drug exposure make illicit drug use in pregnancy a central challenge in maternal-fetal medicine and a need-to-know field in general obstetrics. 相似文献