全文获取类型
收费全文 | 2414篇 |
免费 | 7篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 43篇 |
金属工艺 | 2篇 |
机械仪表 | 5篇 |
建筑科学 | 17篇 |
能源动力 | 4篇 |
轻工业 | 42篇 |
水利工程 | 5篇 |
无线电 | 81篇 |
一般工业技术 | 83篇 |
冶金工业 | 2102篇 |
原子能技术 | 2篇 |
自动化技术 | 28篇 |
出版年
2021年 | 7篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 17篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 80篇 |
1998年 | 748篇 |
1997年 | 406篇 |
1996年 | 251篇 |
1995年 | 133篇 |
1994年 | 126篇 |
1993年 | 124篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 23篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 36篇 |
1976年 | 76篇 |
1975年 | 8篇 |
1974年 | 3篇 |
1972年 | 9篇 |
1971年 | 4篇 |
1965年 | 2篇 |
1963年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有2421条查询结果,搜索用时 15 毫秒
31.
32.
L Vulchanova MS Riedl SJ Shuster LS Stone KM Hargreaves G Buell A Surprenant RA North R Elde 《Canadian Metallurgical Quarterly》1998,10(11):3470-3478
The P2X3 receptor subunit, a member of the P2X family of ATP-gated ion channels, is almost exclusively localized in sensory neurons. In the present study, we sought to gain insight into the role of P2X3 and P2X3-containing neurons in sensory transmission, using immunohistochemical approaches. In rat dorsal root ganglia (DRG), P2X3-immunoreactivity (-ir) was observed in small- and medium-sized neurons. Approximately 40% of DRG neuronal profiles in normal rats contained P2X3-ir. In rats that had received neonatal capsaicin treatment, the number of P2X3-positive neurons was decreased by approximately 70%. Analysis of the colocalization of P2X3-ir with cytochemical markers of DRG neurons indicated that approximately 94% of the P2X3-positive neuronal profiles were labelled by isolectin B4 from Bandeiraea simplicifolia, while only 3% contained substance P-ir, and 7% contained somatostatin-ir. In dorsal horn of rat spinal cord, P2X3-ir was observed in the inner portion of lamina II and was reduced subsequent to dorsal rhizotomy, as well as subsequent to neonatal capsaicin treatment. Finally, P2X3-ir accumulated proximal to the site of sciatic nerve ligation, and was seen in nerve fibres in skin and corneal epithelium. In summary, our results suggest that P2X3 is expressed by a functionally heterogeneous population of BSI-B4-binding sensory neurons, and is transported into both central and peripheral processes of these neurons. 相似文献
33.
34.
SA Geier E Schielke K Tatsch I Sadri JR Bogner G Hammel KM Einh?upl FD Goebel 《Canadian Metallurgical Quarterly》1993,7(12):1589-1594
OBJECTIVE: The pathogenesis of neurologic and neuropsychologic dysfunction in HIV-1 infection is unclear. The purpose of the study was to determine an association between cerebral perfusion and HIV-1-related ocular microangiopathic syndrome. METHODS: We studied 28 HIV-1-infected patients, seven of whom presented with asymptomatic HIV infection, nine with lymphadenopathy syndrome or AIDS-related complex, and 12 with AIDS. Cerebral perfusion was semi-quantitatively measured by single photon emission computed tomography of the brain using technetium-99 hexamethyl-propylenamine oxime (HMPAO-SPECT). The conjunctival manifestation of HIV-1-related microangiopathic syndrome was measured by a rating scale determining blood-flow sludging and, retinal cotton-wool spots were counted. CD4 count, neopterin, beta 2-microglobulin (beta 2M), haemoglobin, and age were determined as putative confounding variables. RESULTS: Mean conjunctival sludge in patients with normal HMPAO-SPECT findings was 1.3 +/- 0.5 (mean +/- s.e.m.); no cotton-wool spots were present. In patients with slightly impaired HMPAO-SPECT, it was 2.1 +/- 0.6 and mean cotton-wool spot count was 1.1 +/- 0.4. In patients with severely impaired HMPAO-SPECT, mean conjunctival sludge was 4.5 +/- 0.3 and mean cotton-wool spot count was 4.9 +/- 1.1 HMPAO-SPECT findings were closely associated with conjunctival sludge (r = 0.72; P < 0.001) and number of cotton-wool spots (r = 0.78; P < 0.001), whereas only a slight association with staging of HIV disease was found (P = 0.052). Analysis of covariance controlling for CD4 count neopterin, beta 2M, age, and haemoglobin demonstrated a significant difference between the three HMPAO-SPECT groups for both the number of cotton-wool spots (P < 0.001) and the conjunctival sludge rating (P < 0.001). CONCLUSION: There was a close association between severity of HIV-1-related ocular microangiopathic syndrome and severity of cerebral hypoperfusion. Microvascular alterations might contribute to the pathogenesis of neurological and neuropsychological symptoms in patients with HIV-1 disease. Furthermore, the conjunctival sludge rating and the number of cotton-wool spots might be appropriate indicators for severity of microvascular changes of the central nervous system [corrected]. 相似文献
35.
Kolundzija B.M. Ognjanovic J.S. Sarkar T.K. Harrington R.F. 《Antennas and Propagation Magazine, IEEE》1996,38(1):75-79
WIPL is a program which allows fast and accurate analysis of antennas. The geometry of any metallic structure (even a very large structure) is defined as a combination of wires and plates. WIPL's analysis features include evaluations of the current distribution, near and far field, and impedance, admittance and s-parameters. The program uses an entire-domain Galerkin method. Efficiency of the program is based on the flexible geometrical model, and sophisticated basis functions. In this paper, the basic theory implemented in the program, and some results concerning TV UHF panel antennas and large horn antennas are given 相似文献
36.
KM Peltekian F Wong PP Liu AG Logan M Sherman LM Blendis 《Canadian Metallurgical Quarterly》1997,92(3):394-399
OBJECTIVE: Large volume paracentesis is an effective treatment for refractory ascites, but the need for routine infusion of albumin or other volume expanders remains controversial. The aim of this study was to assess the short term effects of a single 5-L paracentesis without albumin replacement on total central blood volume, systemic and renal hemodynamics, sodium homeostasis, and neurohumoral factors. PATIENTS AND METHODS: Twelve patients with biopsy-proven cirrhosis and tense, diuretic-resistant ascites were studied before and 48 h after a single 5-L paracentesis without albumin infusion. Systemic hemodynamics and total central blood volume were assessed using radionuclide angiography. Glomerular filtration rate and effective renal plasma flow were measured by inulin and para-aminohippurate clearances, respectively. Lithium clearance was used as an index of proximal tubular reabsorption of sodium. In addition, plasma concentrations of neurohumoral factors were determined. RESULTS: Total central blood volume was 2.41 +/- 0.33 L/m2 (mean +/- SEM) before and 2.34 +/- 0.18 L/m2 48 h after large volume paracentesis (p = 0.76). Similarly, no differences were detected in the cardiac index, glomerular filtration rate, effective renal plasma flow, urinary sodium excretion, hematocrit, plasma renin activity, or concentrations of plasma aldosterone, norepinephrine, or atrial natriuretic factor. CONCLUSIONS: A single large volume paracentesis without albumin replacement causes no disturbances in systemic and renal hemodynamics 48 h after the procedure. These results suggest that a single 5-L paracentesis without albumin infusion is a safe and satisfactory short term option for the management of patients with cirrhosis and tense, diuretic-resistant ascites. 相似文献
37.
Ws/Ws rats are deficient in both mucosal- and connective tissue-type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined in Ws/Ws, heterogenic Ws/+, and normal +/ + rats sensitized with the nematode Nippostrongylus brasiliensis. Antigen challenge resulted in fatal anaphylactic shock in some +/+ and Ws/+ rats, but not in Ws/Ws rats. Marked dye leakage developed within 30 min in the trachea of +/+ and Ws/+ rats, while Ws/Ws rats showed no substantial increases in the levels of vascular permeability. Ex vivo stimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitized Ws/Ws rat-lung fragments did not. In Ws/Ws rats, levels of nematode-specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell-deficient Ws/Ws rats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell-derived mediators required for initiation of the reaction. 相似文献
38.
B Rehermann KM Chang JG McHutchison R Kokka M Houghton FV Chisari 《Canadian Metallurgical Quarterly》1996,98(6):1432-1440
Hepatitis C virus (HCV)-specific cytotoxic T lymphocytes (CTL) are present in the peripheral blood and liver of chronically infected patients. The current study was performed to study the relationship between the strength of the CTL response, liver disease severity, and viral load. The results may be summarized as follows: first, using CTL precursor frequency (CTLpf) analysis to quantitate the peripheral blood CTL response, chronically infected patients were less strongly sensitized to a panel of well-defined HCV epitopes than they were to an epitope within the influenza matrix protein. Second, HCV-specific CTLpf did not correlate with disease activity or viral load in the majority of patients on a cross-sectional basis, although it did increase in three patients concomitant with sharp increases in liver disease. Finally, interferon therapy did not enhance the CTLpf against the HCV epitopes studied in these patients, indicating that its antiviral effect is independent of the CTL response. Since the HCV-specific CTLpf in the blood is actually quite low, the CTL may contribute to ongoing liver disease in these patients while being quantitatively inadequate to destroy all of the infected hepatocytes, thereby facilitating HCV persistence and contributing to chronic liver disease. 相似文献
39.
40.
The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of torsemide are reviewed. Torsemide belongs to the pyridine-sulfonylurea class of loop diuretics. Its primary site of activity is the thick ascending limb of the loop of Henle, where it blocks active reabsorption of sodium and chloride, resulting in diuresis, natriuresis, and other effects. Torsemide has high bioavailability, a relatively long half-life, and a prolonged duration of activity. It is highly protein bound. Clinical trials indicate that torsemide is effective in the treatment of hypertension and of edema and other symptoms in patients with chronic renal failure (CRF), hepatic dysfunction, or congestive heart failure (CHF). Torsemide has infrequent, mild, and transient adverse effects; among the most common are orthostatic hypotension, fatigue, dizziness, and nervousness. The recommended initial oral dosages of torsemide are 10-20 mg/day for CHF, 20 mg/day for CRF, 5 mg/day for hypertension, and 5-10 mg/day (in combination with a potassium-sparing diuretic or aldosterone antagonist) for hepatic cirrhosis. In most patients, the pharmacokinetic advantages of torsemide over other loop diuretics are unlikely to translate into a substantial edge in clinical outcomes, and in practice there may be no cost advantages. Although torsemide does not offer major advantages over other loop diuretics, it may be of benefit in patients who do not respond to or cannot tolerate other agents. 相似文献