全文获取类型
收费全文 | 1915篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 128篇 |
金属工艺 | 19篇 |
机械仪表 | 20篇 |
建筑科学 | 25篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 68篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 128篇 |
一般工业技术 | 137篇 |
冶金工业 | 1203篇 |
原子能技术 | 4篇 |
自动化技术 | 145篇 |
出版年
2021年 | 11篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 42篇 |
2012年 | 23篇 |
2011年 | 40篇 |
2010年 | 30篇 |
2009年 | 25篇 |
2008年 | 39篇 |
2007年 | 28篇 |
2006年 | 34篇 |
2005年 | 35篇 |
2004年 | 35篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 58篇 |
1998年 | 360篇 |
1997年 | 204篇 |
1996年 | 154篇 |
1995年 | 83篇 |
1994年 | 64篇 |
1993年 | 83篇 |
1992年 | 33篇 |
1991年 | 28篇 |
1990年 | 38篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 26篇 |
1986年 | 14篇 |
1985年 | 30篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 30篇 |
1976年 | 60篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1971年 | 3篇 |
1970年 | 6篇 |
排序方式: 共有1928条查询结果,搜索用时 15 毫秒
81.
82.
83.
SP Newman J Brown KP Steed SJ Reader H Kladders 《Canadian Metallurgical Quarterly》1998,113(4):957-963
STUDY OBJECTIVES: To compare lung deposition of fenoterol or flunisolide administered from a novel, multidose inhalation device delivering liquid droplets (RESPIMAT; Boehringer Ingelheim Ltd; Bracknell, UK) or from conventional metered-dose inhalers (MDIs) with and without spacers. DESIGN: Two randomized, three-way crossover studies. SETTING: Clinical research laboratory. PARTICIPANTS: Healthy, nonsmoking volunteers. INTERVENTIONS: In one study, radiolabeled aerosols of fenoterol from the RESPIMAT device and from a conventional MDI with or without an Aerochamber spacer (Trudell Medical; London, Ontario Canada). In the second study, radiolabeled aerosols of flunisolide from a RESPIMAT device, from a RESPIMAT device modified by inclusion of a baffle/impactor in the mouthpiece, and from a conventional MDI with an Inhacort spacer (Boehringer Ingelheim; Ingelheim, Germany). MEASUREMENTS AND RESULTS: Assessment of the deposition of fenoterol or flunisolide in the lung and oropharynx using gamma scintigraphy. Safety was assessed based on reported adverse effects and spirometry (FEV1, FVC, and peak expiratory flow rate) to detect any paradoxical bronchoconstriction. The RESPIMAT device delivered significantly more fenoterol to the lungs than either an MDI alone or an MDI with Aerochamber (39.2% vs 11.0% and 9.9% of metered dose, respectively; p<0.01). Oropharyngeal deposition of fenoterol from the new device was lower than that from the MDI (37.1% vs 71.7%, respectively; p<0.01). The RESPIMAT device deposited significantly more flunisolide in the lungs compared with MDI plus spacer (44.6% vs 26.4%, respectively; p<0.01), while resulting in similar oropharyngeal deposition (26.2% vs 31.2%, respectively). Introduction of a baffle into the RESPIMAT system reduced lung deposition of flunisolide to 29.5%, and oropharyngeal deposition to 7.8% (p<0.01). CONCLUSION: The RESPIMAT device may prove to be an effective alternative to MDIs for the administration of inhaled bronchodilators and corticosteroids. The high lung deposition and low oropharyngeal deposition may lead to improved efficacy and tolerability of inhaled medications, especially corticosteroids. 相似文献
84.
L Dawson CG Schaar PH de Meijer AE Meinders 《Canadian Metallurgical Quarterly》1998,142(32):1826-1829
A women aged 36 with a positive family anamnesis for autoimmune endocrine diseases and a history of thyroid diseases, developed major complaints of general malaise, orthostatic hypotension and loss of appetite after the start of a treatment with levothyroxin because of (sub)clinical hypothyroidism. She was found to suffer from primary adrenocortical insufficiency masked by excessive use of liquorice and a lowered metabolism, but which via the suppletion with thyroid hormone had led to an addisonian crisis. 相似文献
85.
Kinins lower blood pressure but the stimuli leading to kinin generation and their origin are less well known. We administered angiotensin II in graded infusion doses to patients with primary hypertension and normotensive controls to study the effects of on circulating kallikreins. Angiotensin II infusion did not significantly alter plasma prekallikrein or tissue kallikrein levels and the plasma levels and their changes did not correlate with blood pressure levels or changes. In the normotensive group prekallikrein levels and renin activity correlated negatively with urinary sodium and chloride excretion during basal conditions and partially during the infusion. U-tissue kallikrein concentration increased in the normotensive group. Thus, acute elevation of blood pressure induced by angiotensin II does not activate the circulating kallikrein-kinin systems. Data rather indicate that the circulating kallikrein-kinin systems may be related to alterations in volume and sodium balance and that these mechanisms may be altered in primary hypertension. 相似文献
86.
87.
AP Mowat P Gutjahr B Portmann JL Dawson R Williams 《Canadian Metallurgical Quarterly》1976,17(7):492-494
Focal nodular hyperplasia of the liver in a 3 year old child has been successfully treated by ligation of the hepatic artery branches supplying the lesion. The prominence of the abnormal vasculature in the lesion and its possible aetiological involvement is stressed. Because of the risks of partial hepatectomy, hepatic artery ligation is suggested as the treatment of choice for focal nodular hyperplasia. 相似文献
88.
Efforts have been made to establish the chemical constitution of water-blown polyurethane foams. Specific reagents have been used to indicate the presence of biuret or allophanate linkages. Partial hydrolysis techniques have been used to degrade foams selectively and hence isolate parts of the chain network. These methods yield information which is not satisfactorily obtained from the examination of undegraded polymer and which is not available after total degradation. It has been shown that polyureatype linkages are present in the chain network of both polyester and polyether foams. 相似文献
89.
R. Frank R.L. Thomas H. Holdrinet R.K. McMillan H.E. Braun R. Dawson 《Journal of Great Lakes research》1981,7(4):363-381
Suspended solids were collected from 105 streams on the Canadian side of the Great Lakes during snow melt and spring flow between 1974 and 1977. Analyses were performed for organochlorine and organophosphorus insecticides and three industrial chemicals. All streams sampled contained suspended solids that were contaminated with DDT, its metabolites, and polychlorinated biphenyl (PCB). The highest mean concentrations of ΣDDT (356 μg/kg) occurred in 1974 from streams draining the Niagara Peninsula and entering Lake Ontario; these were correlated to areas of high use on fruit in the past. The highest loadings by lake section, however, were along the north shore of Lake Erie involving a very much larger delivery of suspended solids. The highest concentrations of PCB were on suspended solids entering Lake Ontario in 1974 along the northern (191 μg/kg) and southwestern (172 μg/kg) shore and were associated with the high urban-industrial activity in the megalopolis of Hamilton-Burlington-Oakville-Mississauga-Toronto. However, the highest loadings occurred along Lake St. Clair where two large rivers, the Thames and Sydenham, discharge a much larger volume of suspended solids. The highest individual concentrations of HEOD (dieldrin) were found on suspended solids in two streams entering along the southwestern shoreline of Lake Ontario. However, the highest mean residues on solids for all streams was in waters entering Lake Erie (3 μg/kg) and the highest loadings were into Lake St. Clair. Endosulfan, chlordane, and heptachlor epoxide were detected in some streams entering all five lakes. No aldrin, endrin, mirex, heptachlor, or organophosphorus insecticides were detected. 相似文献
90.
KP Maier H Talke G Hoppe-Seyler J Fr?hlich P Schollmeyer G Sch?nbach KP Erhart W Gerok 《Canadian Metallurgical Quarterly》1976,54(21):1021-1025
Enzymes of the Krebs-Henseleit urea-cycle were localized by means of differential centrifugation and fractional tissue extraction in rat liver and in human liver. Argininosuccinatlyase (ASAL) and Argininosuccinatsynthetase (ASAS) represent enzymes of the soluble cytoplasmic fraction. Ornithine-ketoacid-transaminase(OKT), carbamyl-phosphate-synthetase (CPS) and ornithine-carbamyl-transferase (OCT) are localized in the mitochondrial and nuclei fractions of the liver cell. Most of the arginase activity is bound to subcellular structures (probably to nuclei). A small portion of arginase-activity was found in the soluble cytoplasmatic fraction. The enzymes of the Krebs-Henseleit urea-cycle are equally distributed in rat liver and in human liver. Differences in the subcellular localisation of (mitochondrial) enzymes in human liver could be attributed to mitochondrial breakage during tissue preparation and do not represent in-vivo conditions. 相似文献