全文获取类型
收费全文 | 2390篇 |
免费 | 89篇 |
国内免费 | 61篇 |
专业分类
电工技术 | 62篇 |
综合类 | 138篇 |
化学工业 | 122篇 |
金属工艺 | 58篇 |
机械仪表 | 51篇 |
建筑科学 | 46篇 |
矿业工程 | 15篇 |
能源动力 | 28篇 |
轻工业 | 113篇 |
水利工程 | 25篇 |
石油天然气 | 9篇 |
武器工业 | 4篇 |
无线电 | 76篇 |
一般工业技术 | 78篇 |
冶金工业 | 1586篇 |
原子能技术 | 8篇 |
自动化技术 | 121篇 |
出版年
2024年 | 5篇 |
2023年 | 17篇 |
2022年 | 36篇 |
2021年 | 39篇 |
2020年 | 33篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 43篇 |
2012年 | 67篇 |
2011年 | 70篇 |
2010年 | 70篇 |
2009年 | 74篇 |
2008年 | 70篇 |
2007年 | 80篇 |
2006年 | 73篇 |
2005年 | 43篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 31篇 |
2000年 | 17篇 |
1999年 | 50篇 |
1998年 | 464篇 |
1997年 | 294篇 |
1996年 | 170篇 |
1995年 | 97篇 |
1994年 | 71篇 |
1993年 | 91篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 1篇 |
1978年 | 9篇 |
1977年 | 48篇 |
1976年 | 131篇 |
1975年 | 6篇 |
1955年 | 2篇 |
排序方式: 共有2540条查询结果,搜索用时 15 毫秒
31.
SJ McPherson RN Gibson NA Collier TG Speer ND Sherson 《Canadian Metallurgical Quarterly》1998,206(3):665-672
Ancylostoma duodenale is still the dominant hookworm species in the Mediterranean area, India, China and Japan. In the present study, biopsied materials were taken from the small intestine of 30 patients infected only with A. duodenale and 12 cross matched controls. The results showed some pathological changes in severely infected cases. However, normal or insignificant changes were seen in the enzymatic activity of the intestinal mucosa. 相似文献
32.
GA Storch RS Buller TC Bailey NA Ettinger T Langlois M Gaudreault-Keener PL Welby 《Canadian Metallurgical Quarterly》1994,32(4):997-1003
This study compared PCR and an assay for cytomegalovirus (CMV) pp65 antigenemia (CMV-vue; INCSTAR Corp.) with a quantitative shell vial culture (QSVC) technique for the detection of CMV in serial blood specimens from 46 solid-organ transplant recipients. In a comparison based on 535 specimens tested by PCR and QSVC, CMV was detected by PCR in 41 and by QSVC in 37 of 43 recipients at risk of CMV infection. The mean number of days after transplantation of initial detection of CMV was 29.9 for PCR and 34.0 for QSVC (P = 0.01). The antigenemia assay was performed on 395 specimens, including 304 of those also tested by PCR. In these specimens, CMV was detected by the antigenemia assay, QSVC, and PCR in 30, 32, and 35 (respectively) of 38 patients at risk, with no statistically significant difference in the time to detection. Each of the assays detected CMV in similar proportions of patients with and without clinically significant CMV infection. PCR stayed positive longer after transplantation than the other assays but frequently returned to negative when more than 6 months had elapsed after transplantation. The antigenemia assay and PCR stayed positive longer after institution of antiviral therapy than QSVC. PCR can provide highly sensitive detection of CMV viremia, but a PCR assay for CMV is not yet available in kit form. The pp65 antigenemia assay and shell vial culture are quantifiable and comparable in sensitivity. Either is recommended for rapid detection of CMV in blood specimens from solid-organ transplant recipients. 相似文献
33.
34.
Phenylbutazone was administered intravenously (i.v.) to a group of four lactating cows at a dosage of 6 mg/kg body weight. Whole plasma, protein-free plasma and milk were analysed for phenylbutazone residues. Pharmacokinetic parameters of total and free phenylbutazone in plasma were calculated using a non compartmental method. In regards to whole plasma data, the mean volume of distribution at steady state (Vss), was 147 mL/kg body weight, with a mean (+/-SEM) terminal elimination half-life (t1/2) of 40+/-6 h. The mean clearance (Cl) was 3 mL/h/kg body weight. The Vss as determined from the protein-free plasma fraction was 50021 mL/kg body weight. This larger Vss of free phenylbutazone compared to total plasma phenylbutazone was attributed to a high degree of plasma protein binding, as well as the greater penetration of free phenylbutazone into tissues. The mean t1/2 of free phenylbutazone was 39+/-5 h. This similarity to the t1/2 estimated from total plasma phenylbutazone data is attributed to an equilibrium between free and plasma phenylbutazone during the terminal elimination phase. Mean t1/2 as determined from milk, applying a urinary excretion rate model, was 47+/-4 h. Milk clearance of phenylbutazone was 0.009 mL/h/kg body weight, or about 0.34% of total body clearance. Furthermore, evidence suggests that phenylbutazone either binds to milk proteins, or is actively transported into milk, as its concentration in milk was greater than that predicted due to a simple partitioning from plasma into milk. 相似文献
35.
36.
37.
首先建立了局部一维搜索方法,以客车车身线框模型与型钢截面库为基础,通过截面库优化排序、杆件局部模型一维搜索以及局部-整体迭代等优化步骤,得出一个满足多工况强度要求的车身结构杆件截面尺寸下限。然后通过灵敏度分析选择关键杆件,利用多目标遗传算法NSGA-II对选定杆件的截面尺寸在截面库的范围内进行优化,以提高整体刚度及模态性能。最后在某承载式客车车身杆件截面优化设计中,将该方法的优化结果作为设计输入,结果表明,车身结构的最终方案具有明显的轻量化效果。 相似文献
38.
39.
40.