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   1216篇
  免费   64篇
  国内免费   13篇
耳鼻咽喉   1篇
儿科学   50篇
妇产科学   46篇
基础医学   74篇
口腔科学   22篇
临床医学   125篇
内科学   245篇
皮肤病学   7篇
神经病学   62篇
特种医学   192篇
外科学   99篇
综合类   46篇
预防医学   66篇
眼科学   6篇
药学   202篇
  1篇
中国医学   1篇
肿瘤学   48篇
  2021年   8篇
  2018年   6篇
  2017年   9篇
  2016年   10篇
  2015年   9篇
  2014年   15篇
  2013年   25篇
  2012年   31篇
  2011年   29篇
  2010年   22篇
  2009年   25篇
  2008年   19篇
  2007年   36篇
  2006年   47篇
  2005年   34篇
  2004年   31篇
  2003年   44篇
  2002年   48篇
  2001年   43篇
  2000年   30篇
  1999年   31篇
  1998年   32篇
  1997年   28篇
  1996年   24篇
  1995年   30篇
  1994年   27篇
  1993年   40篇
  1992年   31篇
  1991年   31篇
  1990年   26篇
  1989年   43篇
  1988年   52篇
  1987年   55篇
  1986年   52篇
  1985年   33篇
  1984年   19篇
  1983年   23篇
  1982年   14篇
  1981年   21篇
  1980年   29篇
  1979年   11篇
  1978年   18篇
  1977年   20篇
  1975年   14篇
  1974年   8篇
  1973年   5篇
  1972年   10篇
  1971年   8篇
  1970年   6篇
  1969年   7篇
排序方式: 共有1293条查询结果,搜索用时 968 毫秒
91.
Nurse Practice Act violations pose threats to consumers of nursing services and lead to disciplinary actions against nurses by boards of nursing. To analyze nursing law violations, the actions and decisions of boards of nursing, and evaluate trends in negligent and unsafe nursing practice, the authors reviewed nursing law violations as well as rates of recidivism among nurses who received actions against their nursing licenses in Kentucky. The authors discuss how their findings can assist nurse administrators in investigating nurse care givers before employment and in initiating safeguards against nurse violations that affect client safety.  相似文献   
92.
93.
The aim of this study was to examine if the drug chlorzoxazone has any influence on the toxicokinetics of acetone and toluene. Chlorzoxazone is mainly metabolized by the same enzyme (Cytochrome P450 2E1) as ethanol and many other organic solvents. Ten male volunteers were exposed to solvent vapor (2 h, 50 watt) in an exposure chamber. Each subject was exposed to acetone only (250 ppm), acetone + chlorzoxazone, toluene (50 ppm) only, toluene + chlorzoxazone, and chlorzoxazone only. Chlorzoxazone (500 mg) was taken as two tablets 1 h prior to solvent exposure. Samples of blood, urine and exhaled air were collected before, during and until 20 h post exposure. The samples were analyzed by head-space gas chromatography (acetone and toluene) and high-performance liquid chromatography (chlorzoxazone, 6-hydroxychlorzoxazone and hippuric acid). The time-concentration curves of acetone and toluene in blood were fitted to one- and four-compartment toxicokinetic models, respectively. Intake of chlorzoxazone was associated with slight but significant increases in the area under the blood concentration-time curve (AUC) and steady state concentration of acetone in blood, along with non significant tendencies to an increased half time in blood and an increased AUC in urine. Except for a delayed excretion of hippuric acid in urine, no effects on the toluene toxicokinetics were seen after chlorzoxazone treatment. Small increases in chlorzoxazone plasma levels were seen after exposure compared to chlorzoxazone alone. These interactions, although statistically significant, seem to be small compared to the interindividual variability on metabolism and toxicokinetics.  相似文献   
94.
Ethylene glycol monomethyl ether (EGME) and its acetate ester (EGMEA) are highly flammable, colorless, moderately volatile liquids with very good solubility properties. They are used in paints, lacquers, stains, inks and surface coatings, silk-screen printing, photographic and photo lithographic processes, for example, in the semiconductor industry, textile and leather finishing, production of food-contact plastics, and as an antiicing additive in hydraulic fluids and jet fuel. EGME and EGMEA are efficiently absorbed by inhalation as well as via dermal penetration. Dermal absorption may contribute substantially to the total uptake following skin contact with liquids or vapours containing EGME or EGMEA. EGMEA is rapidly converted to EGME in the body and the two substances are equally toxic in animals. Therefore, the two substances should be considered as equally hazardous to man. Effects on peripheral blood, testes, and sperm have been reported at occupational exposure levels ranging between 0.4 and 10 ppm EGME in air, and with additional, possibly substantial, dermal exposure. Severe malformations and disturbed hematopoiesis have been linked with exposure to EGME and EGMEA at unknown, probably high, levels. Embryonic deaths in monkeys and impaired spermatogenesis in rabbits have been reported after daily oral doses of 12 and 25 mg per kg body weight, respectively. In several studies, increased frequency of spontaneous abortions, disturbed menstrual cycle, and subfertility have been demonstrated in women working in the semiconductor industry. The contribution of EGME in relation to other exposure factors in the semiconductor industry is unclear.  相似文献   
95.
Styrene is used in the manufacture of plastics and polymers and in the boat-building industry. The major metabolic route for styrene in rats, mice, and humans involves conversion to styrene-7,8-oxide (SO). The purpose of this study was to evaluate blood SO, SO-hemoglobin (SO-Hb) adducts, and urinary metabolites in styrene-exposed human volunteers and to compare these results with data previously obtained for rodents. Four healthy male volunteers were exposed for 2 h during light physical exercise to 50 ppm (13)C(8)-styrene vapor via a face mask. Levels and time profiles of styrene in exhaled air, blood, and urine (analyzed by GC) and urinary excretion patterns of mandelic acid and phenylglyoxylic acid in urine (analyzed by HPLC) were comparable to previously published volunteer studies. Maximum levels of SO in blood (measured by GC-MS) of 2.5-12.2 (average 6.7) nM were seen after 2 h, i.e., in the first sample collected after exposure had ended. The styrene blood level in humans was about 1.5 to 2 times higher than in rats and 4 times higher than in mice for equivalent styrene exposures. In contrast the SO levels in human blood was approximately fourfold lower than in mice. The level of hydroxyphenethylvaline (determined by GC-MS-MS) in pooled blood collected after exposure was estimated as 0.3 pmol/g globin corresponding to a SO-Hb adduct increment of about 0.003 pmol/g and ppmh. NMR analyses of urine showed that a major portion (> 95%) of the excreted (13)C-derived metabolites was derived from hydrolysis of SO, while only a small percentage of the excreted metabolites (< 5%) was derived from metabolism via phenylacetaldehyde. Signals consistent with metabolites derived from other pathways of styrene metabolism in rodents (such as glutathione conjugation with SO or ring epoxidation) were not detected.  相似文献   
96.
The adult respiratory distress syndrome is a major cause of morbidity and mortality in critical care patients. Lung injury in this syndrome is frequently associated with lung infection. The combined insults result in an influx of neutrophils and damage to the pulmonary epithelium. We investigated whether active neutrophil elastolytic activity was present in the bronchoalveolar fluid in baboons with mild or moderate hyperoxic lung injury and infection. Group A (N = 7) was exposed for 6 days to FIO2 = 0.8 and then inoculated by intratracheal bolus with Pseudomonas aeruginosa strain DGI-R130 (PA); the FIO2 was reduced to 0.5. Group B (N = 6) was exposed to similar concentrations of inspired oxygen but inoculated with buffered saline. Antibiotics included parenteral penicillin and topical gentamicin and polymyxin B. All 3 were given continuously in group B but stopped 24 h prior to PA inoculation in group A. Bronchoalveolar lavage fluid was collected 1 week before oxygen administration, when the FIO2 was reduced (day 6 or 7) and prior to necropsy (day 11). Hemodynamic, pulmonary function, microbiological, and biochemical variables were studied. Injured, infected animals (group A) had significant elevations of mean pulmonary artery pressure and decreases in total lung capacity and PaO2 compared both to baseline and to group B at day 11. At autopsy, group A had significant increases of bronchoalveolar lavage fluid (BALF) neutrophils and bacterial pathogens. Elastase levels in BALF (equal to 0 at baseline) rose to 136 +/- 98 ng/ml in group A vs. 6 +/- 14 ng/ml in group B. The elastase was inhibited by inhibitors of serine proteases including ones specific for neutrophil elastase. On Sephacryl S-300 chromatography the elastase activity eluted near human alpha 2-macroglobulin and separated from other proteolytic activity. These studies demonstrate a significant level of elastase in BALF from injured, infected baboons compared to injured, uninfected animals.  相似文献   
97.
Preference for ethanol versus a placebo was assessed in 12 normal volunteers using a cumulative dosing preference test. The test consisted of four sampling sessions followed by three choice sessions. During the sampling sessions subjects received either five cumulating oral doses of ethanol (0.1g/kg per dose) or equal volumes of placebo, at 15-min intervals. Subjective and observer-rated drug effects, psychomotor performance, drug liking ratings, and breath ethanol levels were measured at regular intervals. During choice sessions, subjects first chose which of the two substances (drug or placebo) they wished to take and ingested one unit dose. Then, at 15-min intervals throughout the session, they could ingest up to ten additional unit doses of the same substance (i.e., up to 1.1 g/kg ethanol). On average, the subjects chose the ethanol-containing beverage on 75% of the choice sessions, and they self-administered a mean total dose of 0.8g/kg per session. Subjects varied in the amount of ethanol ingested on choice sessions, and the amount they chose was related to their subjective responses to the drug during sampling. Subjects who chose the most ethanol reported experiencing stimulant-like effects from the ethanol, whereas the subjects who chose ethanol less frequently and ingested lower doses reported primarily sedative-like effects from the drug. The results demonstrate that the cumulative dosing procedure can be used effectively to evaluate drug preferences and dose preferences in normal volunteers.  相似文献   
98.
Objective To undertake a five year follow up of a cohort of women and children delivered by forceps or vacuum extractor in a randomised controlled study.
Design Follow up of a randomised controlled trial.
Setting District general hospital in the West Midlands.
Population Follow up questionnaires were sent to 306 of the 313 women originally recruited at the North Staffordshire Hospital to a randomised controlled study comparing forceps and vacuum extractor for assisted delivery. Two hundred and twenty-eight women responded (74.5%) and all were included in the study; forceps (   n = 115  ) and vacuum extractor (   n = 113  ).
Main outcome measures Bowel and urinary dysfunction, child vision assessment, and child development.
Results Maternal adverse symptoms at long term follow up were relatively common. Urinary incontinence of various severity was reported by 47%, bowel habit urgency was reported by 44% (98/225), and loss of bowel control 'sometimes' or 'frequently' by 20% of women (46/226). No significant differences between instruments were found in terms of either bowel or urinary dysfunction. Overall, 13% (20/158) of children were noted to have visual problems. There was no significant difference in visual function between the two groups: ventouse 11/86 (12.8%), compared with forceps 9/72 (12.5%); odds ratio 0.97,95% CI 0.38–2.50. Of the 20 children with visual problems, a family history was known in 18, and 17/18 (94%) had a positive family history for visual problems. No significant differences in child development were found between the two groups.
Conclusions There is no evidence to suggest that at five years after delivery use of the ventouse or forceps has specific maternal or child benefits or side effects.  相似文献   
99.
Psoriasis is associated with significant physical and psychological burden affecting all facets of a patient’s life – relationships, social activities, work and emotional wellbeing. The cumulative effect of this disability may be self‐perpetuating social disconnection and failure to achieve a ‘full life potential’ in some patients. Health‐related quality of life studies have quantified the burden of psoriasis providing predominantly cross‐sectional data and point‐in‐time images of patients’ lives rather than assessing the possible cumulative disability over a patient’s lifetime. However, social and economic outcomes indicate there are likely negative impacts that accumulate over time. To capture the cumulative effect of psoriasis and its associated co‐morbidities and stigma over a patient’s life course, we propose the concept of ‘Cumulative Life Course Impairment’ (CLCI). CLCI results from an interaction between (A) the burden of stigmatization, and physical and psychological co‐morbidities and (B) coping strategies and external factors. Several key aspects of the CLCI concept are supported by data similar to that used in health‐related quality of life assessments. Future research should focus on (i) establishing key components of CLCI and determining the mechanisms of impairment through longitudinal or retrospective case–control studies, and (ii) assessing factors that put patients at increased risk of developing CLCI. In the future, this concept may lead to a better understanding of the overall impact of psoriasis, help identify more vulnerable patients, and facilitate more appropriate treatment decisions or earlier referrals. To our knowledge, this is a first attempt to apply and develop concepts from ‘Life Course Epidemiology’ to psoriasis research.  相似文献   
100.
(+/-)-Phenylpropanolamine (PPA), a widely available anorectic and decongestant, was evaluated in several behavioral paradigms in rhesus monkeys and for central nervous system neurotoxicity in rats. PPA (1-30 mg/kg intragastric) reduced food intake in rhesus monkeys but was not self-administered i.v. (0.3-10 mg/kg/injection) by monkeys experienced in drug self-administration. PPA (30-100 mg/kg intragastric) resulted in amphetamine-like responding in two of four monkeys trained in a drug discrimination paradigm to discriminate d-amphetamine from saline. In rats, a 4-day injection regimen of high doses of PPA (200 and 400 mg/kg/day) resulted in approximately a 20% depletion of dopamine in the frontal cortex but failed to deplete dopamine, norepinephrine or serotonin in any other brain region studied. Thus, PPA is an effective anorectic in rhesus monkeys that, based upon drug discrimination results, would be expected to have limited amphetamine-like subjective effects and only at doses well in excess of effective anorectic doses. However, based upon self-administration results, PPA would not be predicted to have amphetamine-like dependence potential. Moreover, repeated administration of PPA did not produce the severe central nervous system neurotoxicity associated with many other amphetamine congeners.  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