全文获取类型
收费全文 | 2715篇 |
免费 | 0篇 |
专业分类
化学工业 | 4篇 |
建筑科学 | 1篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
石油天然气 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 7篇 |
冶金工业 | 2684篇 |
自动化技术 | 1篇 |
出版年
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2011年 | 3篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 3篇 |
1999年 | 78篇 |
1998年 | 805篇 |
1997年 | 467篇 |
1996年 | 290篇 |
1995年 | 152篇 |
1994年 | 141篇 |
1993年 | 177篇 |
1992年 | 21篇 |
1991年 | 33篇 |
1990年 | 43篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 21篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 14篇 |
1980年 | 31篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 70篇 |
1976年 | 181篇 |
1975年 | 4篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2715条查询结果,搜索用时 0 毫秒
61.
NM Forones M Tanaka D Machado JB Falc?o M Giovanoni 《Canadian Metallurgical Quarterly》1997,34(1):3-6
Female SJL mice are more susceptible than male mice to experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein (MBP)-specific T lymphocytes. In the present study, we examined mechanisms involved in this gender-related difference in disease susceptibility. MBP-specific T lymphocytes derived from spleens of males during the effector phase of adoptive EAE produced significantly higher levels of IL-10, an anti-inflammatory cytokine in EAE. A protective effect of testosterone was then shown. Females implanted with dihydrotestosterone pellets demonstrated a significantly less severe course of EAE as compared with females implanted with placebo pellets. Finally, MBP-specific T lymphocytes derived from dihydrotestosterone-implanted females produced significantly higher levels of IL-10 than those from placebo. Together these data indicate that testosterone exerts a protective effect in EAE that is mediated at least in part by enhanced production of IL-10 by autoantigen-specific T lymphocytes. 相似文献
62.
Early surgery in patients with mitral regurgitation due to flail leaflets: a long-term outcome study
LH Ling M Enriquez-Sarano JB Seward TA Orszulak HV Schaff KR Bailey AJ Tajik RL Frye 《Canadian Metallurgical Quarterly》1997,96(6):1819-1825
BACKGROUND: The optimal timing for surgery in patients with mitral regurgitation is disputed. Because of the frequency of left ventricular dysfunction, which is difficult to predict, early surgery has been recommended, but its potential benefits have not been demonstrated. METHODS AND RESULTS: The outcomes of 221 patients (mean age, 65 +/- 13 years; 71% males) with flail leaflets diagnosed with two-dimensional echocardiography between 1980 and 1989 who were eligible for operation were analyzed. Group I comprised 63 patients who had early mitral valve surgery (within 1 month after diagnosis). Group II comprised 158 patients initially treated conservatively (80 of whom were operated on later). Group I patients were younger (P=.009), had more symptoms (P<.0001), and were more frequently in atrial fibrillation (P=.023) than group II patients. There was no difference in ejection fraction between the groups. The early surgery strategy was followed by an improved overall survival rate (P=.028) and a lower incidence of cardiovascular deaths (P=.025), congestive heart failure (P=.046), and new chronic atrial fibrillation (P=.032), as confirmed by multivariate analysis (adjusted risk ratios of 0.31, 0.18, 0.38, and 0.05, respectively; all P<.02). CONCLUSIONS: In patients with mitral regurgitation due to flail leaflets, the strategy of early surgery versus conservative management is associated with an improved long-term survival rate, decreased cardiac mortality, and decreased morbidity after diagnosis. This outcome advantage suggests that early surgery is a reasonable treatment option to be considered in low-risk candidates with repairable valves and severe mitral regurgitation. 相似文献
63.
SA Gould EE Moore FA Moore JB Haenel JM Burch H Sehgal L Sehgal R DeWoskin GS Moss 《Canadian Metallurgical Quarterly》1997,43(2):325-31; discussion 331-2
We have previously documented the safety of 1 unit (50 gram) of human polymerized hemoglobin (Poly SFH-P) in healthy volunteers. This report describes the first patient trial to assess the therapeutic benefit of Poly SFH-P in acute blood loss. Thirty-nine patients received 1 (n = 14), 2 (n = 2), 3 (n = 15), or 6 (n = 8) units of Poly SFH-P instead of red cells as part of their blood replacement after trauma and urgent surgery. There were no safety issues related to the infusion of Poly SFH-P. The plasma hemoglobin concentration ([Hb]) after the infusion of 6 units (300 gram) of Poly SFH-P was 4.8 +/- 0.8 g/dL (mean +/- SD). Although the red cell [Hb] fell to 2.9 +/- 1.2 g/dL, the total [Hb] was maintained at 7.5 +/- 1.2 g/dL. Poly SFH-P maintained total [Hb], despite the marked fall in red cell [Hb] due to blood loss. The utilization of O2 (extraction ratio) was 27 +/- 16% from the red cells and 37 +/- 13% from the Poly SFH-P. Twenty-three patients (59%) avoided allogeneic transfusions during the first 24 hours after blood loss. Poly SFH-P effectively loads and unloads O2 and maintains total hemoglobin in lieu of red cells after acute blood loss, thereby reducing allogeneic transfusions. Poly SFH-P seems to be a clinically useful blood substitute. 相似文献
64.
Excretion was studied of catecholamines and diphenilamine (DOPA) in 310 patients with carcinoma of the stomach and large intestine and 43 patients with non-malignant diseases. The oncological patients showed decrease in activity of the mediator link of the sympathoadrenal system (SAS) as well as its reserves but there was no association with sex, age, location or histological structure. Three types of SAS functioning were identified, such as compensation, overstrain and emaciation. Surgical intervention led to activation of the hormonal link and exhaustion of the system's reserves. Two kinds of sympathoadrenal response to stress were described--adequate and inadequate. In the former type, phases of stress remain as they are, unchanged, as are time periods of formation thereof, while under the latter one time periods of the phases formation or formation thereof get disordered. 相似文献
65.
JB Kotch DC Browne CL Ringwalt V Dufort E Ruina PW Stewart JW Jung 《Canadian Metallurgical Quarterly》1997,21(11):1025-1037
OBJECTIVE: The purpose of this research was to determine whether risk factors for a maltreatment report in the first year of life, especially the interaction of life event stress and social support, persist into the second and third years of life. METHOD: Predominantly low income mothers who had been interviewed shortly after the birth of infants in a longitudinal cohort were re-interviewed around the infants' first birthdays, and reports to North Carolina's Central Registry of Child Abuse and Neglect were tracked for substantiated maltreatment reports. RESULTS: Variables significantly associated with a substantiated maltreatment report in the second or third year of life (p < .01) were first year maltreatment reports and participation in Medicaid. Three interactions between a stressful life event indicator variable and a social support indicator variable were significant predictors of substantiated second or third year reports (p < .05). CONCLUSIONS: Even in the presence of significant risk factors from the first year of life, life event stress can increase the risk of a substantiated maltreatment report in the second or third years of life, but social support may moderate the effect of life events. 相似文献
66.
Coastal marine ecosystems world-wide are threatened by invasions of nonindigenous species. The ubiquity of marine sibling species identifiable only by genetic analysis suggests that many invasions are cryptic and therefore undetected, causing an underestimation of the actual number and impacts of invading species. We test this hypothesis with European crabs in the genus Carcinus that have invaded five regions globally. Partial 16S ribosomal RNA gene sequences confirm sibling species status of morphologically similar Atlantic C. maenas and Mediterranean C. aestuarii. Based on 16S rRNA haplotypes, crabs from California, New England and Tasmania were all C. maenas. However, we report the cryptic multiple invasion of both species in Japan and South Africa, where only C. aestuarii and C. maenas, respectively, were previously recognized. 相似文献
67.
A beta-adrenoceptor agonist isoprenaline potently stimulated cyclic AMP formation in chick cerebral cortical slices. L-Noradrenaline (10-1000 microM) also increased cortical nucleotide synthesis, the effect being antagonized by beta-adrenoceptor blocker propranolol, and not affected by alpha 1- and alpha 2-adrenoceptor blockers, prazosin and yohimbine, respectively. Clonidine, a selective alpha 2-agonist, had no effect on cerebral cyclic AMP production stimulated by both isoprenaline and forskolin. However, clonidine (0.001-10 microM) concentration-dependently suppressed forskolin-driven cyclic AMP synthesis in intact chick pineal glands. In living chicks clonidine suppressed the nocturnal activity of cyclic AMP-dependent serotonin N-acetyltransferase, a rate-limiting enzyme in melatonin biosynthesis, the effect being prevented by yohimbine. The data suggest that the cyclic AMP generating system of the pineal gland, but not that of cerebral cortex in chick, is negatively regulated by alpha 2-adrenergic receptor-mediated signal. 相似文献
68.
C Chapron P Devroey JB Dubuisson JL Pouly P Vercellini 《Canadian Metallurgical Quarterly》1997,12(4):867-868
69.
EM Prvulovich JB Bomanji WA Waddington P Rudrasingham AM Verbruggen PJ Ell 《Canadian Metallurgical Quarterly》1997,38(5):809-814
1. Effects of feeding condition from birth were examined on the sensitivity of neuromuscular transmission to d-tubocurarine (dTc) in vitro in male mice of the ddY strain. 2. Mice were trained to climb two separated cylindrical steel-wire tubes for feeding and drinking, respectively, from 16 days of age. Some mice were conventionally fed, from 99 days of age. Nerve-muscle preparations were made from the left phrenic nerve diaphragm muscle (DPH), the sciatic nerve soleus muscle (SOL), and the sciatic nerve extensor digitorum longus muscle (EDL) of 99-day-old and 155-day-old mice. The nerve trunk was electrically activated with trains of four pulses and tetanic pulses. 3. The sensitivity to the effects of dTc decreased in the order EDL, SOL, and DPH. This result held true in all mice tested. 4. This sensitivity was significantly potentiated by the compulsory movement. 5. The supersensitivity remained even when mice were conventionally fed after 99 days of age. 6. The compulsion rendered EDL antifatigable on tetanic stimulation. This property was also retained after a return to conventional feeding. 7. These results suggest that the effects of feeding condition from birth might remain on neuromuscular functions after termination of the conditioning. 相似文献
70.