全文获取类型
收费全文 | 2438篇 |
免费 | 3篇 |
专业分类
综合类 | 2篇 |
化学工业 | 8篇 |
机械仪表 | 1篇 |
轻工业 | 1篇 |
石油天然气 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 4篇 |
冶金工业 | 2420篇 |
自动化技术 | 2篇 |
出版年
2022年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 2篇 |
2012年 | 2篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2007年 | 1篇 |
2003年 | 3篇 |
2000年 | 1篇 |
1999年 | 70篇 |
1998年 | 744篇 |
1997年 | 415篇 |
1996年 | 298篇 |
1995年 | 148篇 |
1994年 | 128篇 |
1993年 | 144篇 |
1992年 | 14篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 21篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 1篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1977年 | 62篇 |
1976年 | 176篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1965年 | 1篇 |
1964年 | 3篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有2441条查询结果,搜索用时 0 毫秒
1.
The neuronal nicotinic synapse in tissue slices of the adrenal medulla was studied with whole-cell patch-clamp. Excitatory postsynaptic currents (EPSCs) were evoked by local field stimulation or occurred spontaneously especially when external [K+] was increased. EPSCs were carried by channels sharing biophysical and pharmacological properties of neuronal-type nicotinic receptors (nAChRs). A single-channel conductance (gamma) of 43-45 pS was found from nonstationary variance analysis of EPSCs. Spontaneous EPSCs were tetrodotoxin-insensitive and Ca(2+)-dependent and occurred in burst-like clusters. Quantal analysis of spontaneous EPSCs gave a quantal size of 20 pA and amplitude histograms were well described by binomial models with low values of quantal content, consistent with a small number of spontaneously active release sites. However, rare large amplitude EPSCs suggest that the total number of sites is higher and that extrajunctional receptors are involved. Our estimates of quantal content and size at the chromaffin cell neuronal nicotinic synapse may be useful in characterizing central neuronal-type nicotinic receptor-mediated cholinergic synaptic transmission. 相似文献
2.
AG Niessen JG Bollemeijer RJ de Keizer PH de Meijer 《Canadian Metallurgical Quarterly》1994,138(15):770-775
OBJECTIVE: To assess how often the aetiology is established in patients with uveitis, what systemic disease are found and what is the contribution of the internist to the diagnostic process. DESIGN: Retrospective study. SETTING: University Hospital Leiden, the Netherlands. METHOD: From January 1987 to April 1992, 342 patients presented with uveitis. All patients underwent a standard ophthalmological examination. Referral to an internist and individualised laboratory screening followed in patients with recurrent, chronic, bilateral or panuveitis. Recorded were: ophthalmological data, results of laboratory screening, results of analysis by the internist, final diagnosis and presence of systemic disease. RESULTS: 149 (44%) patients were examined by the internist, 18 (5.2%) were seen by another specialist. In 169 (49%) patients a specific diagnosis was made. 74 (22%) had a systemic disease, 74 a primary ocular disease. In 28 (8%) a systemic disease was presumed (5% were HLA-B27 positive, 3% had abnormal laboratory results); 5 (1%) patients had endophthalmitis as a complication of a septic process. CONCLUSION: In approximately 1/3 of the patients with uveitis a systemic disease was found. Examination by the internist tailored to the individual patient is essential in the evaluation of uveitis patients. 相似文献
3.
ST O'Sullivan GT McGreal A Lyons L Burke JG Geoghegan MP Brady 《Canadian Metallurgical Quarterly》1994,47(9):851-852
A case of histologically confirmed Paget's disease of the breast in a 72 year old man, without underlying breast carcinoma, is reported. This report raises questions about the pathogenesis of this condition and suggests that Paget's disease is an independent, intraepidermal carcinoma rather than a direct extension of intraductal carcinoma of the breast to the nipple and areola. 相似文献
4.
5.
Sulfonylureas have, in the past, been reported to have adverse cardiovascular effects. Glimepiride is a new sulfonylurea. In spite of stimulating less insulin secretion, it has, depending on the species, equal or higher blood glucose decreasing activity and according to preliminary studies less cardiovascular activity than glibenclamide. Further studies were performed to confirm the lower cardiovascular activity of glimepiride. The IC50 for inhibition of rilmakalim-activated KATP channel currents in isolated ventricular myocytes was 31.6 nM for glimepiride and 6.8 nM for glibenclamide. In endotoxin shock-rats at a dose of 1 x 2 mg/kg i.v., glibenclamide induced a significantly higher blood pressure increase than glimepiride. At two i.v. doses of 20 mg/kg 4 min apart, in normal rats, glibenclamide produced signs of ischemia in the ECG in nearly all animals, glimepiride almost none, in diabetic rats, glibenclamide produced in all animals a lethal cardiogenic shock preceeded by serious ECG changes, glimepiride only in one fifth of the animals. In open-chest dogs, on intracoronary infusion of equieffective blood glucose-lowering doses, glibenclamide, gliclazide and glimepiride all reduced coronary blood flow, increased coronary resistance, depressed the mechanical activity of the heart, enhanced myocardial O2-extraction, reduced the serum potassium level and induced a moderate endocardial ST-segment elevation, but glimepiride to a significantly less extent than glibenclamide and gliclazide. The presented data confirm that glimepiride at equivalent blood glucose decreasing doses has less cardiovascular activity than conventional sulfonylureas. 相似文献
6.
KW Scheller J G?rres JG Ross M Wiescher R Harkewicz DJ Morrissey BM Sherrill M Steiner NA Orr JA Winger 《Canadian Metallurgical Quarterly》1994,49(1):46-50
The shortage of suitable liver donors for children has motivated the use of ABO-incompatible (ABO-I) grafts for transplantation in urgent situations. However, survival after ABO-I liver grafts has been reported at about 30% as compared with 80% in cases of ABO-identical or -compatible liver grafts. This difference has been attributed to antibody-mediated, hyperacute or chronic liver rejection, due to preformed ABO antibodies (alloantibodies). In this study, we report our results with ABO-I livers in children without alloantibodies at the time of transplantation. From January 1988 to June 1993, 143 OLT were performed in 122 children. Eight children received 8 ABO-I liver grafts. Of these, 7 patients were included in the study. All 7 were alloantibody free before OLT. Five children were spontaneously alloantibody free, while in 2 children, the plasma alloantibodies were eliminated before and after transplantation using intravenous infusion of specific blood group antigens of the donor blood group (soluble antigens). Immunosuppression consisted of a triple-drug treatment combining CsA, AZA, and steroids. The follow-up period was between 10 and 48 months. One child died from a surgical complication. Six children survived, but 1 died 10 months later from intestinal obstruction. There were no graft losses and no episodes of hyperacute or chronic rejection. The graft and patient survival rate was 71%. There was a 28% incidence of rejection, but all were mild (requiring steroid boluses only). Our results suggest that the absence of ABO alloantibodies at the time of and after transplantation can protect ABO-I liver grafts against antibody-mediated rejection, whether hyperacute or chronic, and that soluble antigens are effective in eliminating alloantibodies in children. 相似文献
7.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
8.
9.
BACKGROUND: The effects of beta 2 adrenergic agonists on chemoreceptors remain controversial. This study was designed to examine whether fenoterol, a beta 2 adrenergic agonist, increases the ventilatory responses to hypercapnia (HCVR) and hypoxia (HVR) in normal subjects. METHODS: HCVR was tested with a rebreathing method and HVR was examined with a progressive isocapnic hypoxic method in 11 normal subjects. Both HCVR and HVR were assessed by the slope of occlusion pressure (P0.1) or ventilation (VE) plotted against end tidal carbon dioxide pressure and arterial oxygen saturation, respectively. Respiratory muscle strength, spirometric values and lung volume were measured. After a single oral administration of 5 mg fenoterol or placebo HCVR and HVR were evaluated. RESULTS: Fenoterol treatment did not change the specific airway conductance or forced expiratory volume in one second. Respiratory muscle strength did not change. Fenoterol increased the slope of the HCVR of both P0.1 (from 0.251 (0.116) to 0.386 (0.206) kPa/kPa, average increase 71%) and VE (from 10.7 (3.4) to 15.1 (4.2) l/min/kPa, average increase 52%), and shifted the response curves to higher values. For the HVR fenoterol increased the slopes of both P0.1 and VE (from -4.06 (2.00) x 10(-3) to -7.99 (4.29) x 10(-3) kPa/%, an average increase of 83%, and from -0.221 (0.070) to -0.313 (0.112) l/min/%, a 44.5% increase, respectively), and shifted the response curves to higher values. CONCLUSION: Acute administration of fenoterol increases the ventilatory responses to both hypercapnia and hypoxia in normal subjects. 相似文献
10.