全文获取类型
收费全文 | 2478篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 88篇 |
金属工艺 | 21篇 |
机械仪表 | 18篇 |
建筑科学 | 25篇 |
矿业工程 | 3篇 |
能源动力 | 10篇 |
轻工业 | 39篇 |
水利工程 | 6篇 |
石油天然气 | 5篇 |
无线电 | 37篇 |
一般工业技术 | 97篇 |
冶金工业 | 2064篇 |
原子能技术 | 7篇 |
自动化技术 | 62篇 |
出版年
2022年 | 4篇 |
2021年 | 11篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 30篇 |
2012年 | 11篇 |
2011年 | 23篇 |
2010年 | 22篇 |
2009年 | 28篇 |
2008年 | 27篇 |
2007年 | 30篇 |
2006年 | 28篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 13篇 |
2001年 | 17篇 |
2000年 | 8篇 |
1999年 | 71篇 |
1998年 | 682篇 |
1997年 | 334篇 |
1996年 | 227篇 |
1995年 | 111篇 |
1994年 | 124篇 |
1993年 | 129篇 |
1992年 | 23篇 |
1991年 | 27篇 |
1990年 | 36篇 |
1989年 | 33篇 |
1988年 | 31篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 21篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 25篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 42篇 |
1976年 | 89篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有2491条查询结果,搜索用时 15 毫秒
951.
JF Winther FW Bach S Friis WJ Blot L Mellemkjaer K Kj?ller C H?gsted JK McLaughlin JH Olsen 《Canadian Metallurgical Quarterly》1998,50(4):951-955
US angiography, enhanced with intraarterial CO2 microbubbles imaging, documented 40 nodules of hepatocellular carcinoma (HCC) lesser than 20 mm in diameter in 34 patients, which were convinced histopathologically. As to the imaging acuity of arterial vascularity in nodules, US angiography was compared with DSA and US color angio. The detection of arterial vascularity was possible in 34 (85.0%) of 40 nodules by US angiography, 26 (65.0%) by DSA, and 28 (70.0 %) by US color angio. US angiography was available for detection of HCC, particularly with small HCC lesser than 20 mm in size. 相似文献
952.
JK Patnaik BS Das SK Mishra S Mohanty SK Satpathy D Mohanty 《Canadian Metallurgical Quarterly》1994,51(5):642-647
To document histopathologic evidence on the pathogenic mechanism of human cerebral malaria, we used light microscopy to study brain specimens from 23 patients who died of central nervous system involvement with Plasmodium falciparum. Sequestration of parasitized red blood cells (PRBCs) leading to cerebral capillary clogging was seen. In a few specimens, vascular clogging by PRBCs was associated with margination of mononuclear cells. In others, capillaries were virtually empty and lymphocytes and monocytes were seen in apposition (marginated) to the capillary endothelial surface. The endothelial cells appeared plump, hypertrophied, and prominent. The capillary wall appeared thickened by fibrinous material. Massive intercellular brain edema along with extravasated red blood cells, mononuclear cells, and plasmatic fluid was also noticed. In addition to hypoxia induced by PRBC-mediated vascular clogging, marginating mononuclear cells may contribute to the pathogenesis of cerebral malaria. The precise role played by this phenomenon needs further evaluation. 相似文献
953.
954.
955.
FJ van Spronsen Y Thomasse GP Smit JV Leonard PT Clayton V Fidler R Berger HS Heymans 《Canadian Metallurgical Quarterly》1994,20(5):1187-1191
Hereditary tyrosinemia type I (McKusick 27670) is a heterogeneous disease with poor prognosis, yet there are few reports of the long-term prognosis. It is therefore difficult to decide on the treatment for individual patients. We have conducted an international survey of patients with tyrosinemia type I and examined the probability of survival on dietary treatment and the causes of death in 108 patients with tyrosinemia type I. The survival after the onset of symptoms varied with the age at onset; the earlier the symptoms developed the poorer the outlook. Liver failure and recurrent bleeding (67%), hepatocellular carcinoma (17%) and the porphyria-like syndrome with respiratory failure (10%) were the most common causes of death. The 1- and 2-yr survival probability after the onset of symptoms in patients in whom symptoms developed before 2 mo, between 2 and 6 mo and after 6 mo were 38%/29%, 74%/74% and 96%/96%, respectively. On the basis of these survival rates, a new classification--which is important with respect to choices in treatment--is proposed: very early (onset of symptoms < 2 mo), early (2 to 6 mo) and late presenting form (> 6 mo). 相似文献
956.
GW Miller JK Staley CJ Heilman JT Perez DC Mash DB Rye AI Levey 《Canadian Metallurgical Quarterly》1997,41(4):530-539
The plasma membrane dopamine transporter (DAT) is considered to be a reliable marker of presynaptic dopaminergic terminal loss. Previous in vivo imaging and postmortem binding studies have detected a loss in striatal DAT binding in Parkinson's diseased (PD) brain; however, these techniques have poor spatial resolution and may suffer from nonspecific binding of some ligands. In this study, we use novel highly specific monoclonal antibodies to distinct epitopes of human DAT to quantify and localize the protein. Western blot analysis revealed marked reductions in DAT immunoreactivity in putamen, caudate, and nucleus accumbens of PD brain compared with control cases, and the reductions were significantly correlated to disease duration. Immunohistochemistry revealed DAT-immunoreactive fibers and puncta that were dense throughout the striatum of control brains but that were drastically reduced in putamen of PD brains. Caudate from PD brains showed a significant degree of sparing along the border of the ventricle, and the nucleus accumbens was relatively preserved. An unexpected finding was that discrete islands of DAT immunoreactivity were preserved within the matrix of PD putamen. Thus, immunological analysis of DAT protein provides novel and sensitive means for localizing and quantifying DAT protein in PD and other neurological disorders involving dopaminergic systems. 相似文献
957.
The classical clinical picture of coeliac disease includes prolonged diarrhoea with failure to thrive. During the past two decades this type of active presentation of coeliac disease has decreased in many European countries, giving the impression that coeliac disease is a disappearing disease. However, this is not true. The disease can be found in older children with a more or less silent presentation. Silent coeliac disease can be detected by active screening with serological tests. Coeliac disease can be suspected in children suffering from mild gastrointestinal symptoms, such as abdominal pain, and in those with signs of nutritional deficiencies, as well as in children of first-degree relatives of already diagnosed coeliacs, patients with IgA-deficiency, patients suffering from dental enamel hypoplasia or dermatitis herpetiformis, and patients with some other disease known to be associated with coeliac disease, such as diabetes mellitus. According to the fundamental criteria of coeliac disease, the intestinal mucosa is flat when the individual is eating gluten-containing foods. However, this is not strictly true. Intolerance to gluten is obviously variable and the intestinal mucosa may be normal. This type of latent coeliac disease can be detected by analysing genetic markers, measuring antibodies in intestinal fluid or counting the density of intra-epithelial gamma/delta T cells which are increased greatly even in the latent phase of coeliac disease. Thus the general concept of the natural history of coeliac disease is changing. 相似文献
958.
959.
SB Kombian TM Saleh NI Fiagbe X Chen JJ Akabutu JK Buolamwini QJ Pittman 《Canadian Metallurgical Quarterly》1997,44(5):603-610
Ibogaine is a natural alkaloid of Voacanga africana that is effective in the treatment of withdrawal symptoms and craving in drug addicts. As the synaptic and cellular basis of ibogaine's actions are not well understood, this study tested the hypothesis that ibogaine and Voacanga africana extract modulate neuronal excitability and synaptic transmission in the parabrachial nucleus using the nystatin perforated patch-recording technique. Ibogaine and Voacanga africana extract dose dependently, reversibly, and consistently attenuate evoked excitatory synaptic currents recorded in parabrachial neurons. The ED50 of ibogaine's effect is 5 microM, while that of Voacanga africana extract is 170 micrograms/ml. At higher concentrations, ibogaine and Voacanga africana extract induce inward currents or depolarization that are accompanied by increases in evoked and spontaneous firing rate. The depolarization or inward current is also accompanied by an increase in input resistance and reverses polarity around 0 mV. The depolarization and synaptic depression were blocked by the dopamine receptor antagonist haloperidol. These results indicate that ibogaine and Voacanga africana extract 1) depolarize parabrachial neurons with increased excitability and firing rate; 2) depress non-NMDA receptor-mediated fast synaptic transmission; 3) involve dopamine receptor activation in their actions. These results further reveal that the Voacanga africana extract has one-hundredth the activity of ibogaine in depressing synaptic responses. Thus, ibogaine and Voacanga africana extract may produce their central effects by altering dopaminergic and glutamatergic processes. 相似文献
960.
Sleep apnea syndrome in acromegalic patients] 总被引:1,自引:0,他引:1
H Konop A Frank-Piskorska JK Podgórski L Delimat 《Canadian Metallurgical Quarterly》1998,32(2):351-358
Hippocampal slices prepared from adult rats were loaded with fura-2 and the intracellular free Ca2+ concentration ([Ca2+]i) in the CA1 pyramidal cell layer was measured. Hypoxia (oxygen-glucose deprivation) elicited a gradual increase in [Ca2+]i in normal Krebs solution. At high extracellular sodium concentrations ([Na+]o), the hypoxia-induced response was attenuated. In contrast, hypoxia in low [Na+]o elicited a significantly enhanced response. This exaggerated response to hypoxia at a low [Na+]o was reversed by pre-incubation of the slice at a low [Na+]o prior to the hypoxic insult. The attenuation of the response to hypoxia by high [Na+]o was no longer observed in the presence of antagonist to glutamate transporter. However, antagonist to Na+-Ca2+ exchanger only slightly influenced the effects of high [Na+]o. These observations suggest that disturbance of the transmembrane gradient of Na+ concentrations is an important factor in hypoxia-induced neuronal damage and corroborates the participation of the glutamate transporter in hypoxia-induced neuronal injury. In addition, the excess release of glutamate during hypoxia is due to a reversal of Na+-dependent glutamate transporter rather than an exocytotic process. 相似文献