全文获取类型
收费全文 | 3179篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 314篇 |
金属工艺 | 94篇 |
机械仪表 | 63篇 |
建筑科学 | 106篇 |
矿业工程 | 10篇 |
能源动力 | 51篇 |
轻工业 | 184篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
无线电 | 138篇 |
一般工业技术 | 341篇 |
冶金工业 | 1612篇 |
原子能技术 | 13篇 |
自动化技术 | 265篇 |
出版年
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 25篇 |
2017年 | 21篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 97篇 |
2012年 | 62篇 |
2011年 | 84篇 |
2010年 | 61篇 |
2009年 | 54篇 |
2008年 | 65篇 |
2007年 | 77篇 |
2006年 | 80篇 |
2005年 | 57篇 |
2004年 | 65篇 |
2003年 | 65篇 |
2002年 | 74篇 |
2001年 | 45篇 |
2000年 | 50篇 |
1999年 | 85篇 |
1998年 | 423篇 |
1997年 | 253篇 |
1996年 | 172篇 |
1995年 | 113篇 |
1994年 | 115篇 |
1993年 | 115篇 |
1992年 | 32篇 |
1991年 | 37篇 |
1990年 | 46篇 |
1989年 | 50篇 |
1988年 | 48篇 |
1987年 | 48篇 |
1986年 | 39篇 |
1985年 | 37篇 |
1984年 | 37篇 |
1983年 | 38篇 |
1982年 | 36篇 |
1981年 | 38篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 44篇 |
1976年 | 83篇 |
1975年 | 27篇 |
1974年 | 17篇 |
1973年 | 20篇 |
1972年 | 19篇 |
排序方式: 共有3231条查询结果,搜索用时 62 毫秒
41.
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
42.
M Wartmann N Cella P Hofer B Groner X Liu L Hennighausen NE Hynes 《Canadian Metallurgical Quarterly》1996,271(50):31863-31868
43.
Ethics and international research. Placebo trials are unethical for established, untested treatments
EC Edi-Osagie NE Edi-Osagie 《Canadian Metallurgical Quarterly》1998,316(7131):625-6; author reply 627
44.
MA Heneghan B Cleary M Murray TA O'Gorman CF McCarthy 《Canadian Metallurgical Quarterly》1998,43(6):1356-1361
Thromboembolic events frequently complicate the clinical course of patients with inflammatory bowel disease (IBD). Hereditary thrombophilia may contribute to this tendency. Resistance to activated protein C is the most recently described thrombophilic state and may account for up to 40% of patients with thrombophilia. Thirty-seven patients with IBD were studied (mean age 44 years, range 18-82 years). Three patients had a history of thrombotic episodes. The 37 controls included 23 men and 17 women (mean age 48 years, range 16-89 years). Disease activity was assessed using the Harvey Bradshaw index for patients with Crohn's disease and the Truelove and Witts grading system for patients with ulcerative colitis. Levels of fibrinogen, antithrombin III (ATIII), protein C, protein S, activated protein C resistance (APCR), and the presence of a lupus anticoagulant (LA) were determined. Median ATIII levels in patients with IBD were significantly lower than controls (98% vs 106%, P = 0.007), while fibrinogen was elevated (4.2 vs 3.3 g/liter, P = 0.026) despite quiescent disease activity. LA was detected in 7/37 patients in the IBD group compared to 0/37 controls. (chi2 = 5.68, P = 0.017). No significant difference was observed in levels of inherited thrombophilic factors and in particular APCR between IBD patients and controls. In conclusion, the presence of inherited thrombophilic defects, in particular APCR, is uncommon in patients with IBD and does not merit routine screening. 相似文献
45.
P O'Hara JE Connett WW Lee M Nides R Murray R Wise 《Canadian Metallurgical Quarterly》1998,148(9):821-830
The authors examine weight gains associated with smoking cessation in the Lung Health Study (1986-1994) over a 5-year follow-up period. A cohort of 5,887 male and female smokers in the United States and Canada, aged 35-60 years, were randomized to either smoking intervention or usual care. Among participants who achieved sustained quitting for 5 years, women gained a mean of 5.2 (standard error, 5.0) kg in year 1 and a mean of 3.4 (standard error, 5.5) kg in years 1-5. Men gained a mean of 4.9 (standard error, 4.9) kg in year 1 and a mean of 2.6 (standard error, 5.8) kg in years 1-5. In regression analyses, smoking-change variables were the most potent predictors of weight change. Participants going from smoking to quit-smoking in a given year had mean weight gains of 2.95 kg/year (3.61%) in men and 3.09 kg/year (4.69%) in women. Over 5 years, 33% of sustained quitters gained > or = 10 kg compared with 6% of continuing smokers. Also among sustained quitters, 7.6% of men and 19.1% of women gained > or = 20% of baseline weight; 60% of the gain occurred in year 1, although significant weight gains continued through year 5. The average gains and the high proportions of sustained and intermittent quitters who gained excessive weight suggest the need for more effective early interventions that address both smoking cessation and weight control. 相似文献
46.
47.
The Surveillance Research Program of the American Cancer Society's Department of Epidemiology and Surveillance reports its 32nd annual compilation of cancer incidence, mortality, and survival data for the United States and around the world. 相似文献
48.
X Chen DJ Kempf HL Sham BE Green A Molla M Korneyeva S Vasavanonda NE Wideburg A Saldivar KC Marsh E McDonald DW Norbeck 《Canadian Metallurgical Quarterly》1998,8(24):3531-3536
The 2-isopropyl thiazolyl group is a highly optimized P3 ligand for C2 symmetry-based HIV protease inhibitors, as exemplified in the drug ritonavir. Here we report that incorporation of this P3 ligand into a piperazine hydroxyethylamine series also yielded novel, highly potent inhibitors. In tissue culture assays, the presence of human serum was less deleterious to the activity of these inhibitors than to that of ritonavir. Furthermore, potent activity against ritonavir resistant HIV was observed. 相似文献
49.
J Br?ns-Poulsen NE Petersen M H?rder K Kristiansen 《Canadian Metallurgical Quarterly》1998,12(6):345-348
The antimicrobial activity of a combination of lactic acid and whey permeate fermented by a nisin-producing Lactococcus lactis strain was tested by the agar diffusion method using bacteria isolated from fish as test organisms. Lactic acid inhibited all bacterial strains studied, but nisin whey permeate inhibited Gram-positive bacteria only. The combination was more effective than lactic acid alone against Pseudomonas fluorescens and Staphylococcus hominis isolated from fish, and Pseudomonas aeruginosa ATCC9721 and Micrococcus luteus ATCC9341. 相似文献
50.
JW Erdman AJ Thatcher NE Hofmann JD Lederman SS Block CM Lee S Mokady 《Canadian Metallurgical Quarterly》1998,128(11):2009-2013
The algae Dunaliella bardawil and Dunaliella salina naturally contain large concentrations of all-trans and 9-cis beta-carotene (betaC). The purpose of this study was to compare the relative serum and tissue accumulation of all-trans and 9-cis betaC in ferrets fed different ratios of all-trans/9-cis betaC derived from two commercial sources, D. bardawil or D. salina (Betatene). Male ferrets (7 wk old) were fed carotene-free, pelleted diets for 27 d. Beginning on d 18, groups of ferrets (n = 6 or 7) received daily, one of six oral supplements varying in ratios of 9-cis and all-trans betaC mixed with approximately 1.0mL of Ensure. Four supplements containing 5.2-8.3 micromol total betaC were prepared from a 20% Betatene preparation, D. bardawil, a high-cis Betatene preparation, and Betatene further enriched in 9-cis betaC with all-trans betaC/9-cis betaC ratios of 2.2, 1.5, 0.6 and 0.4, respectively. Two control supplements, high and low betaC, were prepared from commercial betaC beadlets. The high control supplement had an all-trans/9-cis ratio of 19.0, whereas 9-cis betaC was not detected in the low supplement. On d 27, serum and tissues were obtained for HPLC analysis of betaC and its isomers. Analysis of livers showed that all-trans betaC was the primary isomer present, but 9-cis and other isomers were also detected in all groups. The hepatic all-trans/9-cis ratios were 5.9, 4.9, 2.5, 1.4, 52.2 and47.5, respectively, for the groups listed above. Lower amounts of all-trans and 9-cis betaC were found in kidneys compared with the liver, but ratios of all-trans/9-cis were not different among groups. Only trace amounts of 9-cis betaC were found in serum. These results demonstrate that the algae D. bardawil and D. salina provide a bioavailable source of betaC isomers, but, as in humans, absorption of 9-cis betaC is poor and any 9-cis betaC absorbed is apparently cleared by the liver. 相似文献