全文获取类型
收费全文 | 1025篇 |
免费 | 2篇 |
专业分类
化学工业 | 4篇 |
机械仪表 | 1篇 |
建筑科学 | 2篇 |
轻工业 | 3篇 |
石油天然气 | 19篇 |
无线电 | 2篇 |
一般工业技术 | 10篇 |
冶金工业 | 976篇 |
原子能技术 | 1篇 |
自动化技术 | 9篇 |
出版年
2018年 | 1篇 |
2016年 | 1篇 |
2013年 | 4篇 |
2011年 | 1篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 29篇 |
1998年 | 300篇 |
1997年 | 172篇 |
1996年 | 99篇 |
1995年 | 64篇 |
1994年 | 72篇 |
1993年 | 58篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 31篇 |
1976年 | 71篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1027条查询结果,搜索用时 546 毫秒
171.
JO Atkinson K Mahomed MA Williams GB Woelk S Mudzamiri NS Weiss 《Canadian Metallurgical Quarterly》1998,44(4):86-92
OBJECTIVE: To identify specific foods that predispose Zimbabwean women to a higher or lower risk of pre-eclampsia and/or eclampsia. DESIGN: A case control study was implemented. Participants were asked by questionnaire to recall the specific amounts of meats, poultry, fruits, fish, vegetables and dairy products they had consumed in the month prior to giving birth. SETTING: Harare Maternity Hospital, Harare, Zimbabwe between June of 1995 and April of 1996. SUBJECTS: 180 women clinically diagnosed with pre-eclampsia (144) or eclampsia (36), and 194 normotensive women without these conditions. MAIN OUTCOME MEASURES: Pre-eclampsia/eclampsia. RESULTS: There were few associations between consumption of specific food items and the occurrence of pre-eclampsia/eclampsia. Meat and fruit were the only foods found to be significantly associated with pre-eclampsia. Women who consumed 12 or more servings of meat per month were more likely to have pre-eclampsia/eclampsia when compared to women eating 11 servings of meat or less per month. While intake of bananas and mangos was unrelated to risk, women who consumed other fruits (i.e. apples, oranges, grapes, peaches, apricots, paw paw, and plums), were 1.7 (95% CI = 1.0 to 3.1) times more likely to develop pre-eclampsia/eclampsia as women who ate none of these fruits. However, women who consumed relatively large quantities of these fruits were not at a particularly high risk. Increased consumption of kapenta was modestly associated with a decrease in disease risk, but this finding was well within the limits of chance and no association was present with intake of other types of fish. CONCLUSIONS: Our findings suggest that variation in consumption of specific foods do not have a strong effect on the incidence of pre-eclampsia in this population. However, further research involving the use of a more comprehensive dietary measure, biochemical measurements of nutrients, pre-pregnancy assessment and ascertainment of dietary intake prior to the development of pre-eclampsia are needed. 相似文献
172.
JA Silva GB Leong BE Harry J Ronan R Weinstock 《Canadian Metallurgical Quarterly》1998,43(6):1107-1111
Changes in the fatty acid composition of phospholipid and triglyceride fractions in Spirometra erinaceieuropaei plerocercoids were investigated after 0, 0.5, 1, 3, and 6 hr incubation at 10 C and 37 C with physiological saline containing 5 mM arachidonic acid and 10 mg/ml bovine serum albumin, pH 7.0. At 37 C, arachidonic acid was absorbed and incorporated rapidly into the triglyceride fraction (over 14.4% in composition), and decreased after 2-3 hr; at 10 C, the amount of triglyceride increased slowly and continued to a maximum of 12.9% during 6 hr of incubation. We used a simplified method to extract and purify prostaglandins from the plerocercoid of S. erinaceieuropaei. Prostaglandins were quantified using gas chromatography-mass spectrometry. Prostaglandin E2, PGD2, PGF2alpha, and 6-keto-PGF1alpha were detected under different incubation conditions. In the dose-dependent experiment, PGD2 was detected in plerocercoids incubated with 0.5, 1, 2, and 5 mM arachidonic acid, pH 7.0, at 25 C; PGE2 was detected with 2 and 5 mM arachidonic acid. In the time-dependent experiment, where plerocercoids were incubated with 5 mM arachidonic acid, pH 7.0 at 25 C, PGF2alpha was first detected at 15 min; thereafter, 6-keto-PGF1alpha was detected at 30 min and PGD2 and PGE2 were detected at 1 hr. Thromboxane B2 was not detected in either the dose-dependent or time-dependent experiments, and only PGE2 was detected in the incubation medium with 5 mM arachidonic acid at 1 hr. These results reveal that when plerocercoids change from reptilian to mammalian hosts, they are able to absorb and modify arachidonic acid bound to albumin and generate prostaglandins under suitable conditions. Prostaglandins exhibit potent biological functions for immunoresponses that may be relevant to parasitism and the success of larva migrans in S. erinaceieuropaei. 相似文献
173.
174.
DR Jeyarajah GJ Netto SP Lee G Testa O Abbasoglu BS Husberg MF Levy RM Goldstein TA Gonwa GW Tillery JS Crippin GB Klintmalm 《Canadian Metallurgical Quarterly》1998,66(10):1300-1306
BACKGROUND: The possibility of primary sclerosing cholangitis (PSC) recurrence after liver transplantation has been debated. The aim of this study is to examine whether recurrent PSC and chronic rejection (CR) are different expressions of the same disease process. METHODS: One hundred consecutive patients receiving 118 grafts for the diagnosis of PSC were reviewed and placed into three groups: group A, recurrent disease, as evidenced by cholangiographic and pathologic findings with radiographic arterial flow to the liver (n=18; 15.7%); group B, those who developed CR (n=15; 13.0%); and group C, all others (n=82; 71.3%). Cholangiograms and histopathologic specimens were examined in a blinded fashion. RESULTS: Demographic factors were similar, except for age, with a significantly younger age and more episodes of rejection in groups A and B (P<0.03). Group A had a higher incidence of cytomegalovirus hepatitis (P=0.008). Five-year graft survivals for A, B, and C were 64.6%, 33.3%, and 76.1%, respectively (P=0.0001), 5-year patient survivals were 76.2%, 66.7%, and 89.1%, respectively (P=0.0001), and repeat transplantation rates were 27.8%, 46.7%, and 8.5%, respectively (P=0.005). Radiographically, 90% of cholangiograms in patients with recurrent disease showed at least multiple intrahepatic strictures. Histopathologically, patients with recurrent disease and CR shared many features. CONCLUSIONS: We have described a high incidence of recurrent PSC and CR in patients who received transplants for PSC. Histopathologic analysis suggests that CR and recurrent PSC could represent a spectrum of indistinguishable disease. However, the distinct difference in clinical outcome, as evidenced by an increased repeat transplantation rate and lower graft and patient survival in the CR group, clearly suggests that they are two distinct entities that require very different treatment strategies. 相似文献
175.
176.
L Gregorini J Marco C Palombo M Kozàkovà GB Anguissola B Cassagneau M Bernies A Distante I Marco J Fajadet A Zanchetti 《Canadian Metallurgical Quarterly》1998,31(5):992-1001
OBJECTIVES: We sought to evaluate the efficacy of alpha-adrenergic blocking agents in counteracting left ventricular (LV) dysfunction occurring after transient ischemia in humans. BACKGROUND: The mechanisms underlying postischemic LV dysfunction are largely unknown. METHODS: Percutaneous transluminal coronary angioplasty (PTCA) provides a clinical model of ischemia and reperfusion. In 50 patients undergoing coronary stenting for 77+/-5% stenosis, LV function was monitored by transesophageal echocardiography during and 30-min after PTCA. Fifteen minutes after stenting, 15 patients received 12 microg/kg body weight of the alpha-blocker phentolamine intracoronarily, 15 patients received 600 microg/kg of the alpha1-blocker urapidil intravenously, 10 patients received the combination of phentolamine and 1.2 mg of propranolol intracoronarily, and 10 patients received saline. RESULTS: Fifteen minutes after successful coronary dilation, significant contractile dysfunction occurred in previously ischemic and nonischemic myocardium. LV dysfunction was accompanied by an increase in coronary resistance and diffuse vasoconstriction. Alpha-blockers counteracted LV dysfunction and coronary resistance and the increase in vasoconstriction. Phentolamine and urapidil increased global LV shortening from 34+/-9% to 45+/-8% and to 49+/-8%, respectively (p < 0.05). After the administration of propranolol combined with phentolamine, LV dysfunction remained unchanged (34+/-6%), as in control subjects. CONCLUSIONS: LV dysfunction occurs after PTCA, as described in animal models after ischemia. Alpha-blockers abolished LV, macrocirculatory and microcirculatory dysfunction, whereas the alpha-blocker effect was prevented by combining alpha- and beta-blockers. The evidence of diffuse rather than regional dysfunction, together with the opposite effects of alpha- and beta-blockade, supports the hypothesis of neural mechanisms eliciting postischemic LV dysfunction. 相似文献
177.
CM Hogaboam SW Chensue ML Steinhauser GB Huffnagle NW Lukacs RM Strieter SL Kunkel 《Canadian Metallurgical Quarterly》1997,159(11):5585-5593
Pulmonary granulomatous inflammation modulated by IFN-gamma and IL-12 is also associated with augmented inducible nitric oxide synthase (NOS II). To address the role of increased nitric oxide synthesis in this model, mice received daily i.p. injections of NG-nitro-L-arginine-methyl ester (L-NAME; 8 mg/kg) during both the 2-wk immunization period with purified protein-derivative (PPD) and the subsequent lung challenge with PPD-coated Sepharose beads. Other groups of animals received saline, L-NAME or NG-nitro-D-arginine-methyl ester (D-NAME; 8 mg/kg) during the pulmonary embolization period and not the PPD sensitization period. On day 4 post-PPD bead challenge, PCR analysis of the whole lung revealed that NOS II expression appeared to be similar in both of the L-NAME treatment protocols. L-NAME-treated mice in both dosing protocols had lung lesions that were significantly larger than granuloma lesions measured in mice that received saline or D-NAME. The enlarged lesions from L-NAME-treated mice contained markedly greater numbers of neutrophils and eosinophils. Equivalent numbers of PPD-activated dispersed cells from whole lungs of L-NAME-treated mice produced significantly higher levels of IL-4 and IL-10 and smaller amounts of IL-12 and IFN-gamma compared with similar lung cultures derived from control or D-NAME-treated mice. Levels of C-C chemokines such as monocyte chemoattractant protein-1 (MCP-1), C10, and macrophage inflammatory protein-1alpha (MIP-1alpha) were also significantly elevated in lung cultures from L-NAME-treated mice compared with controls. Thus, nitric oxide regulates the size and cellular composition of the Th1-type lung granuloma, possibly through its effects on the cytokine and chemokine profile associated with this lesion. 相似文献
178.
DL Travis R Fabia GG Netto BS Husberg RM Goldstein GB Klintmalm MF Levy 《Canadian Metallurgical Quarterly》1998,75(2):116-126
BACKGROUND: Cyclosporine A (CYA) is primarily utilized as an immunosuppressant, but its mechanisms of action (including decreased neutrophilic free radical production and stabilization of mitochondrial and lysosomal membranes) may have beneficial effects in ischemia and reperfusion (IR) injury. This study was undertaken to examine the effect of CYA pretreatment on porcine liver histopathologic changes and enzymatic release caused by ischemia and reperfusion. MATERIALS AND METHODS: CYA was administered orally for 4 days prior to surgery in two doses (10 or 20 mg/kg) while controls received only the control vehicle. Pigs were then exposed to 4 h of hepatic ischemia followed by 2 h of reperfusion. RESULTS: Significant decreases in AST levels compared to controls were seen in high dose CYA pigs at the end of ischemia and at 30-min intervals during the reperfusion period. Controls exhibited necrotic hepatocytes and severe inflammatory cell infiltration, while high dose CYA animals demonstrated mild inflammatory cell infiltrates. Controls had decreased survival--20% did not survive reperfusion. CONCLUSIONS: This study indicates that CYA may be useful in decreasing initial damage resulting from warm hepatic IR injury. 相似文献
179.
Thiamine and thiamine triphosphate (TTP) values were assayed in various brain regions in 11 controls and 13 patients with subacute necrotizing encephalomyelopathy (SNE, Leigh disease). The TTP values of normal brain were 5% of the total thiamine value. The relative TTP (or % TTP) level was consistently low in the pons, midbrain, and cerebellum of all the SNE brains. Twenty-five percent of the SNE brains had normal TTP levels in the frontal region. The TTP values correlated with the degrees of pathologic involvement in all sampled regions of the brain except the cerebellum. The concentration of thiamine in the mammillary bodies exceeded its concentration elsewhere in both control and SNE brains. The finding of low TTP levels in morphologically abnormal regions supports the hypothesis that TTP deficiency is etiologically related to SNE. 相似文献
180.
GB Ferguson 《Canadian Metallurgical Quarterly》1976,86(11):1626-1632
Lateral pharyngotomy offers good exposure for the removal of many laryngeal and hypopharyngeal tumors. The simplified operation I present avoids damage to voice, deglutition or airway. This approach can be expanded to reach almost any tumor of the pharynx and radical neck dissection can be incorporated. The cosmetic result has been satisfactory, but if individual consideration prompts it, a more horizontal skin-fold incision can easily be substituted. 相似文献