全文获取类型
收费全文 | 5297篇 |
免费 | 31篇 |
专业分类
电工技术 | 14篇 |
综合类 | 3篇 |
化学工业 | 169篇 |
金属工艺 | 9篇 |
机械仪表 | 17篇 |
建筑科学 | 77篇 |
矿业工程 | 1篇 |
能源动力 | 41篇 |
轻工业 | 220篇 |
水利工程 | 16篇 |
石油天然气 | 32篇 |
无线电 | 105篇 |
一般工业技术 | 164篇 |
冶金工业 | 4321篇 |
原子能技术 | 18篇 |
自动化技术 | 121篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 25篇 |
2016年 | 17篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 65篇 |
2012年 | 35篇 |
2011年 | 51篇 |
2010年 | 41篇 |
2009年 | 30篇 |
2008年 | 52篇 |
2007年 | 45篇 |
2006年 | 59篇 |
2005年 | 48篇 |
2004年 | 38篇 |
2003年 | 56篇 |
2002年 | 39篇 |
2001年 | 36篇 |
2000年 | 38篇 |
1999年 | 184篇 |
1998年 | 1362篇 |
1997年 | 753篇 |
1996年 | 479篇 |
1995年 | 258篇 |
1994年 | 216篇 |
1993年 | 273篇 |
1992年 | 45篇 |
1991年 | 60篇 |
1990年 | 79篇 |
1989年 | 81篇 |
1988年 | 78篇 |
1987年 | 61篇 |
1986年 | 44篇 |
1985年 | 58篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 7篇 |
1978年 | 14篇 |
1977年 | 109篇 |
1976年 | 229篇 |
1975年 | 14篇 |
1974年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有5328条查询结果,搜索用时 0 毫秒
41.
Each of twelve volunteers, at 2 week intervals, received 1 g of antipyrine, a test drug, and were exposed for 4 h either to toluene (375 mg/m3) or xylene (435 mg/m3) singly or in combination with ethanol (0.45 g/kg body wt. before the onset of exposure and 0.15 g/kg thrice every 1 h during exposure to maintain a steady level of ethanol in blood approximately 11 mmol/dm3). No significant differences were found in salivary antipyrine half-life (T1/2 approximately 12 h); and clearance (ClAP approximately 0.83 cm3/s) between control and groups exposed to solvents and/or ethanol. Nevertheless, a tendency to increase the metabolic rate of antipyrine in xylene-exposed group (T1/2 approximately 6.8 h; ClAP approximately 1.40 cm3/s) and counteraction of ethanol (T1/2 approximately 15 h; ClAP approximately 0.63 cm3/s) should be noted. The stimulation of lipid peroxidation in the serum as a biological effect of combined exposure to ethanol and toluene/xylene was observed. 相似文献
42.
43.
OBJECTIVES: Reoperative coronary artery bypass grafting presents unique challenges for myocardial preservation. The purpose of this study was to compare oxygenated blood cardioplegia with oxygenated crystalloid cardioplegia during reoperative coronary artery bypass grafting using transesophageal echocardiography to assess regional wall motion of the left ventricle before and after cardiopulmonary bypass. METHODS: Sixty-one patients undergoing reoperative coronary artery bypass grafting were prospectively randomized to receive oxygenated blood cardioplegia or oxygenated crystalloid cardioplegia delivered with a combined antegrade-retrograde technique. Transgastric short axis views of the left ventricle were made with transesophageal echocardiography during the operation before cardiopulmonary bypass and immediately after cardiopulmonary bypass. Regional wall motion was graded by a blinded observer, and before cardiopulmonary bypass scores were compared with after cardiopulmonary bypass scores. RESULTS: No significant differences were found in the change in regional wall motion score from before cardiopulmonary bypass to after cardiopulmonary bypass between the blood and crystalloid cardioplegia groups. CONCLUSIONS: This study found blood and crystalloid cardioplegia to be equally efficacious for myocardial preservation during reoperative coronary artery bypass grafting. 相似文献
44.
Laparoscopic cholecystectomy is the treatment of choice for symptomatic cholelithiasis. Since its introduction in 1987, this procedure has been employed with increasing frequency as its safety has been documented in numerous studies. Absolute contraindications to laparoscopic cholecystectomy have become relative contraindications, and patients previously felt to be at excessive risk for laparoscopic cholecystectomy are viewed as patients who may benefit from laparoscopic cholecystectomy. The use of this procedure in patients with comorbid medical conditions has the potential to decrease patient morbidity. Patients who have previously undergone solid organ transplantation and require immunosuppressive therapy are a group of patients who may benefit from laparoscopic cholecystectomy. We report four patients who have previously undergone combined renal and pancreas transplantation who underwent successful laparoscopic cholecystectomy. 相似文献
45.
46.
JS Lewis 《Canadian Metallurgical Quarterly》1993,158(8):548-552
The utilization of a physician critique process in the design of a parenteral nutrition order form, encouraging a standard order option, is assessed. In the critique process, physicians from surgery, medicine, and medical intensive care teams were tasked to use the draft order form and guideline sheet to prescribe a parenteral nutrition order for a hypothetical patient. Prescriber recommendations and problems with the nutrition order form and guideline sheet directed editorial improvements. The physician assessment process is an effective means to measure utility of a draft parenteral order form and prescribing guideline sheet. By utilizing physician expertise, deficiencies inherent in such an order form may be corrected prior to implementation. 相似文献
47.
48.
J. Clausen L. Damkilde L. Andersen 《International journal for numerical methods in engineering》2006,66(6):1036-1059
A new return method for implicit integration of linear isotropic yield criteria is presented. The basic idea is to perform all the manipulations in the principal stress space and thereby achieve very simple formulae for calculating the plastic corrector stresses, based on the constant gradient of such criteria. The return formulae are in closed form and no iteration is required. The method accounts for three types of stress return: return to a single yield plane, to a discontinuity line at the intersection of two yield planes and to a discontinuity point at the intersection between three or more yield planes. The infinitesimal and the consistent elastoplastic constitutive matrix are calculated for each type of stress return, as are the conditions to ascertain which type of return is required. The method is exemplified with the Mohr–Coulomb yield criterion. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
49.
The food antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are structurally related to the hypocholesterolemic drug probucol. The purpose of this study was to determine if BHA can lower serum cholesterol levels as is observed with probucol. Treatment of mice with 0.75% BHA in their feed for 10 days resulted in a significant (P < or = 0.01) elevation of serum cholesterol levels. This effect contrasts with the cholesterol-lowering effect of probucol. Further, the degree of cholesterol elevation was comparable to that observed in mice administered 3% cholesterol in their feed for 7 days. The enzyme acyl CoA:cholesterol acyltransferase (ACAT) was decreased significantly (P < or = 0.01) in liver microsomes from BHA-treated mice. In contrast, hepatic microsomal ACAT activity was increased significantly (P < or = 0.01) in cholesterol-fed mice. These results suggested that the increased serum cholesterol observed in BHA-treated mice was not accompanied by an increase in hepatic cholesterol levels. Indeed, hepatic microsomal cholesterol levels were reduced in BHA-treated mice, but were increased significantly (P < or = 0.01) in cholesterol-fed mice. These results demonstrate that the common food additive BHA elevates serum cholesterol levels by a mechanism that apparently involves the decreased uptake of cholesterol by the liver. 相似文献
50.
We describe three case reports of hematomas in the abdominal wall muscles and discuss etiology, diagnostic findings and treatment. Abdominal wall hematomas are uncommon, and the condition is often misdiagnosed. One of our patients was laparotomised owing to suspected appendicitis, and one patient presented a tuberculous abscess that may have been an infected hematoma. Ultrasonographic examination or CT gives the correct diagnose. Conservative management is the treatment of choice unless bleeding is severe or the course is complicated by infection. 相似文献