全文获取类型
收费全文 | 5401篇 |
免费 | 50篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 2篇 |
化学工业 | 443篇 |
金属工艺 | 49篇 |
机械仪表 | 49篇 |
建筑科学 | 94篇 |
矿业工程 | 6篇 |
能源动力 | 61篇 |
轻工业 | 163篇 |
水利工程 | 31篇 |
石油天然气 | 9篇 |
无线电 | 195篇 |
一般工业技术 | 367篇 |
冶金工业 | 3695篇 |
原子能技术 | 11篇 |
自动化技术 | 263篇 |
出版年
2021年 | 24篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 35篇 |
2015年 | 26篇 |
2014年 | 35篇 |
2013年 | 112篇 |
2012年 | 53篇 |
2011年 | 72篇 |
2010年 | 61篇 |
2009年 | 62篇 |
2008年 | 82篇 |
2007年 | 62篇 |
2006年 | 77篇 |
2005年 | 53篇 |
2004年 | 56篇 |
2003年 | 61篇 |
2002年 | 60篇 |
2001年 | 48篇 |
2000年 | 37篇 |
1999年 | 151篇 |
1998年 | 1015篇 |
1997年 | 580篇 |
1996年 | 390篇 |
1995年 | 258篇 |
1994年 | 208篇 |
1993年 | 261篇 |
1992年 | 64篇 |
1991年 | 65篇 |
1990年 | 67篇 |
1989年 | 85篇 |
1988年 | 68篇 |
1987年 | 79篇 |
1986年 | 76篇 |
1985年 | 83篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 34篇 |
1981年 | 67篇 |
1980年 | 66篇 |
1979年 | 26篇 |
1978年 | 31篇 |
1977年 | 148篇 |
1976年 | 302篇 |
1975年 | 39篇 |
1974年 | 23篇 |
1973年 | 18篇 |
1971年 | 14篇 |
排序方式: 共有5453条查询结果,搜索用时 15 毫秒
111.
112.
113.
WR Bishai NM Graham S Harrington DS Pope N Hooper J Astemborski L Sheely D Vlahov GE Glass RE Chaisson 《Canadian Metallurgical Quarterly》1998,280(19):1679-1684
Stevioside is a sweet-tasting glycoside, composed of stevia, a diterpenic carboxylic alcohol with three glucose molecules, mainly used as a substitute for non-alcoholic sweetener. It has previously been shown to reduce blood pressure in studies in animals and human. The effect of intravenous stevioside on the blood pressure was studied in spontaneously hypertensive rats (SHR). The hypotensive effect on both systolic and diastolic blood pressure was dose-dependent for intravenous doses of 50, 100 and 200 mg/kg in conscious SHR. The maximum reductions in systolic and diastolic blood pressure were 31.4 +/- 4.2% and 40.8 +/- 5.6% (mean +/- SEM) respectively and the hypotensive effect lasted for more than 60 min with a dose of 200 mg/kg. Serum dopamine, norepinephrine and epinephrine levels were not changed significantly 60 min after intravenous injection of stevioside 100 mg/kg in anesthetized SHR. The present data show that stevioside given intravenously to conscious SHR was effective in blood pressure reduction and there was no change in serum catecholamines in anaesthetized animals with this natural compound. 相似文献
114.
115.
116.
RE Whitley 《Canadian Metallurgical Quarterly》1996,41(2):219-221
Polyvalent antivenin remains the most recommended treatment of crotalid envenomation, including copperhead snakebites. Because of the significant morbidity associated with antivenin therapy, some have proposed conservative therapy for less serious envenomations. Few if any studies have separated the treatment of the less serious copperhead bite from the more serious bite of a rattlesnake or a water moccasin. Fifty-five patients, including 12 children, with copperhead bites were treated over a 12-year period. All 55 patients were successfully treated conservatively without antivenin. Conservative treatment resulted in no deaths, limb loss, or residual disability. The mean hospital stay was 2.15 days compared with 3.9 days in patients with systemic symptoms. These data support a conservative approach to most copperhead envenomations and suggest that the treatment for copperhead bites should be segregated from the more serious rattlesnake and water moccasin snakebites. 相似文献
117.
118.
RE Schrohenloher WJ Koopman TG Woodworth LW Moreland 《Canadian Metallurgical Quarterly》1996,23(11):1845-1848
OBJECTIVE: To investigate the effect of diphtheria toxin interleukin 2 recombinant fusion protein (DAB 486IL-2) on in vitro synthesis of immunoglobulin and rheumatoid factor (RF) in patients with severe refractory rheumatoid arthritis (RA) enrolled in a phase II, double blind, placebo controlled study. METHODS: Anticoagulated venous blood samples were obtained before (Day 1) and after (Day 28) intravenous infusion of either DAB 486IL-2 at 0.075 mg/kg/day (12 patients) or saline placebo (10 patients) on Days 1-5. Peripheral blood leukocytes (PBL) were prepared by density gradient centrifugation, cultured in the presence and absence of pokeweed mitogen (PWM) for one week, and culture supernatants assayed for immunoglobulins and IgM RF by ELISA. RESULTS: Compared to placebo treated patients, PWM induced IgM RF synthesis by PBL decreased after treatment with DAB 486IL-2 (p = 0.043). However, there was no apparent correlation with clinical improvement. PWM induced IgM, IgA, and IgG synthesis also tended to decrease, although the changes did not attain statistical significance. In contrast, PWM induced IgM RF, IgM, IgA, and IgG synthesis by PBL from patients treated with placebo tended to increase during the observation period. Spontaneous immunoglobulin and IgM RF production by PBL from either the DAB 486IL-2 or placebo patients remained stable. CONCLUSION: These observations raise the possibility that DAB 486IL-2 may diminish B cell function either directly or indirectly through effects on T cell function, but the change may not correspond to clinical response. 相似文献
119.
A case of clofazimine enteropathy is described. A young male received clofazimine 200 mg daily for four years. He was admitted in a pigmented, emaciated state with abdominal pain, diarrhoea and weight loss. At laparotomy his abdominal organs were stained with dark brown-black pigment due to heavy infiltration with clofazimine crystals. Despite withdrawal of clofazimine his symptoms failed to settle. He developed oedema and hypoalbuminaemia. He died following a cerebral infarction. 相似文献
120.
Eernisse EP Ward RW Watts MH Wiggins RB Wood OL 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1990,37(6):566-570
Experimental results are presented to support the hypothesis that the shape and location of the active region of vibration in a thickness shear mode quartz resonator are the dominant factors in determining the acceleration sensitivity of the resonator. The shape and location of the mode in a real world resonator vary sufficiently from unit to unit (due to material and processing variations) that all other considerations are overwhelmed. It is shown experimentally that the mode shape and/or location can be trimmed with energy trapping by judicious addition or subtraction of mass to produce resonators with improved acceleration sensitivity. 相似文献