首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   641篇
  免费   0篇
化学工业   6篇
冶金工业   632篇
自动化技术   3篇
  2013年   1篇
  2008年   1篇
  2003年   1篇
  2001年   1篇
  1999年   23篇
  1998年   199篇
  1997年   115篇
  1996年   76篇
  1995年   45篇
  1994年   32篇
  1993年   34篇
  1992年   5篇
  1991年   8篇
  1990年   5篇
  1989年   4篇
  1988年   7篇
  1987年   5篇
  1986年   11篇
  1985年   6篇
  1984年   1篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1977年   13篇
  1976年   33篇
  1975年   2篇
排序方式: 共有641条查询结果,搜索用时 10 毫秒
61.
OBJECTIVE: To assess the frequency of methotrexate (MTX)-induced pancytopenia in rheumatoid arthritis (RA). METHODS: A MEDLINE literature search was conducted to identify articles published during the last 15 years (1980-1995) that presented data on MTX-associated pancytopenia. Two case reports of our own experience are also presented. In addition, articles that examined risk factors associated with MTX-related pancytopenia were identified. RESULTS: A total of 70 patients with pancytopenia related to MTX therapy were identified (68 reported in the literature, 2 from our own experience). Sixty-one of the patients were described in published case reports, 7 patients were from 5 long-term prospective studies. In many of these cases, predisposing factors for the development of pancytopenia were described. The 5 long-term prospective studies reported toxicity data on patients who had been treated with MTX for at least 13 weeks. A total of 511 patients were included in the prospective trials, yielding an overall incidence of pancytopenia of 1.4% (7 of 511). Of the 70 cases reported, 12 patients died (17%). Most of them had impaired renal function, hypoalbuminemia, concurrent infection, and/or concomitant medication with more than 5 drugs. The minimal cumulative MTX dose leading to fatal pancytopenia was 10 mg, observed in one of our patients. CONCLUSION: Pancytopenia is not an uncommon side effect of low-dose pulse MTX therapy in RA. It can lead to serious complications, including death.  相似文献   
62.
63.
64.
65.
66.
67.
The cerebral cortex of anaesthetised 2- to 12-day-old rats was superfused with artificial cerebrospinal fluid containing 100 mM acetate substituted for chloride to condition the brain for spreading depression (SD). After such superfusion, the earliest SD-like events were found at day 9 and full blown SD at day 10, whereas in the unconditioned brain the first SD occurred between days 12 and 15. Acetate conditioning of the cerebral cortex may be used to unmask neuronal and glial properties that are hidden in early stages of development.  相似文献   
68.
Eptifibatide, a synthetic peptide inhibitor of the platelet glycoprotein IIb/IIIa receptor, has been studied as an antithrombotic agent in a variety of acute ischemic coronary syndromes. The purpose of the present study was to characterize the disposition of 14C-eptifibatide in man after a single intravenous (i.v.) bolus dose. 14C-Eptifibatide (approximately 50 microCi) was administered to eight healthy men as a single 135-microgram/kg i.v. bolus. Blood, breath carbon dioxide, urine, and fecal samples were collected for up to 72 hours postdose and analyzed for radioactivity by liquid scintillation spectrometry. Plasma and urine samples were also assayed by liquid chromatography with mass spectrometry for eptifibatide and deamidated eptifibatide (DE). Mean (+/- SD) peak plasma eptifibatide concentrations of 879 +/- 251 ng/mL were achieved at the first sampling time (5 minutes), and concentrations then generally declined biexponentially, with a mean distribution half-life of 5 +/- 2.5 minutes and a mean terminal elimination half-life of 1.13 +/- 0.17 hours. Plasma eptifibatide concentrations and radioactivity declined in parallel, with most of the radioactivity (82.4%) attributed to eptifibatide. A total of approximately 73% of administered radioactivity was recovered in the 72-hour period following 14C-eptifibatide dosing. The primary route of elimination was urinary (98% of the total recovered radioactivity), whereas fecal (1.5%) and breath (0.8%) excretion was small. Eptifibatide is cleared by both renal and nonrenal mechanisms, with renal clearance accounting for approximately 40% of total body clearance. Within the first 24 hours, the drug is primarily excreted in the urine as unmodified eptifibatide (34%), DE (19%), and more polar metabolites (13%).  相似文献   
69.
A study of the binding site requirements associated with the N-substituent of (+)-(3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) derivatives was undertaken using a set of rigid vs flexible N-substituents. The study showed that compounds 7-9 bearing the trans-cinnamyl N-substituent most closely reproduced the potency at the opioid receptor of the flexible N-propylphenyl or N-propylcyclohexyl analogues previously reported. Neither the N-substituted cis-cinnamyl nor the cis-phenylcyclopropylmethyl compounds 10 and 11, respectively, showed high affinity for the opioid receptor. However, the N-trans-phenylcyclopropylmethyl compound 12 closely approximated the affinity of compounds 7-9. Additionally, we found that free rotation of the phenyl ring is necessary for high affinity binding and mu receptor subtype selectivity as the planar N-substituted thianaphthylmethyl and benzofuranylmethyl compounds 13 and 14 had significantly lower binding affinities. Altogether, these findings suggest that the high binding affinity, selectivity, and antagonist potency of N-propylphenyl or N-propylcyclohexyl analogues of (+)-(3R, 4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) are achieved via a conformation wherein the connecting chain of the N-substituents is extended away from piperidine nitrogen with the appended ring system rotated out-of-plane relative to the connecting chain atoms. This conformation is quite similar to that observed in the solid state for 5, as determined by single crystal X-ray analysis. Additionally, it was found that, unlike naltrexone, N-substituents bearing secondary carbons attached directly to the piperidine nitrogen of 4 suffer dramatic losses of potency vs analogues not substituted in this manner. Using a functional assay which measured stimulation or inhibition of [35S]GTP-gamma-S binding, we show that the trans-cinnamyl analogues of (+)-(3R, 4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (4) retain opioid pure antagonist activity and possess picomolar antagonist potency at the mu receptor.  相似文献   
70.
In this study, symptom (item) level data were used to perform a psychometric analysis of the DSM-III-R personality disorders (PDs). Determined for each PD criteria set were convergent validity, discriminant validity, and internal consistency. The results indicated that the majority of the PD criteria sets (6 of the 11 ) possessed adequate convergent validity, although discriminant validity was problematic for most of these disorders. Internal consistency was also weak for the PD criteria sets, with only 3 of the 11 exceeding a minimum cutoff score of .70. The present study employed a methodology modeled after the one reported by Morey (1988a), and the results of the two studies were highly similar. Consistent findings across the two data sets can be taken to reflect the actual psychometric properties of the DSM-III-R PDs. The success of our replication demonstrates the potential that large-scale psychometric investigations hold for aiding the development and refinement of the DSM PDs.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号