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   1532篇
  免费   149篇
耳鼻咽喉   43篇
儿科学   49篇
妇产科学   59篇
基础医学   235篇
口腔科学   82篇
临床医学   295篇
内科学   283篇
皮肤病学   26篇
神经病学   164篇
特种医学   14篇
外科学   83篇
综合类   6篇
一般理论   1篇
预防医学   149篇
眼科学   53篇
药学   51篇
中国医学   1篇
肿瘤学   87篇
  2023年   10篇
  2022年   11篇
  2021年   31篇
  2020年   33篇
  2019年   26篇
  2018年   34篇
  2017年   31篇
  2016年   52篇
  2015年   68篇
  2014年   68篇
  2013年   90篇
  2012年   93篇
  2011年   113篇
  2010年   53篇
  2009年   70篇
  2008年   96篇
  2007年   104篇
  2006年   81篇
  2005年   99篇
  2004年   106篇
  2003年   86篇
  2002年   77篇
  2001年   22篇
  2000年   20篇
  1999年   26篇
  1998年   24篇
  1997年   19篇
  1996年   16篇
  1995年   8篇
  1994年   18篇
  1993年   9篇
  1992年   9篇
  1991年   11篇
  1990年   13篇
  1989年   5篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1984年   3篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1980年   5篇
  1979年   2篇
  1977年   2篇
  1976年   4篇
  1971年   2篇
  1970年   1篇
  1964年   1篇
排序方式: 共有1681条查询结果,搜索用时 15 毫秒
1.
OBJECTIVE: To identify the possible contribution of electromyogram (EMG) to scalp electroencephalogram (EEG) rhythms at rest and induced or evoked by cognitive tasks. METHODS: Scalp EEG recordings were made on two subjects in presence and absence of complete neuromuscular blockade, sparing the dominant arm. The subjects undertook cognitive tasks in both states to allow direct comparison of electrical recordings. RESULTS: EEG rhythms in the paralysed state differed significantly compared with the unparalysed state, with 10- to 200-fold differences in the power of frequencies above 20 Hz during paralysis. CONCLUSIONS: Most of the scalp EEG recording above 20 Hz is of EMG origin. Previous studies measuring gamma EEG need to be re-evaluated. SIGNIFICANCE: This has a significant impact on measurements of gamma rhythms from the scalp EEG in unparalysed humans. It is to be hoped that signal separation methods will be able to rectify this situation.  相似文献   
2.
Purpose. Nitrocatechol COMT inhibitors are a new class of bioactive compounds, for which glucuronidation is the most important metabolic pathway. The objective was to characterize the enzyme kinetics of nitrocatechol glucuronidation to improve the understanding and predicting of the pharmacokinetic behavior of this class of compounds. Methods. The glucuronidation kinetics of seven nitrocatechols and 4-nitrophenol, the reference substrate for phenol UDP-glucuronosyltrans-ferase activity, was measured in liver microsomes from creosote-treated rats and determined by non-linear fitting of the experimental data to the Michaelis-Menten equation. A new method that combined densitometric and radioactivity measurement of the glucuronides separated by HPTLC was developed for the quantification. Results. Apparent Km values for the nitrocatechols varied greatly depending on substitution pattern being comparable with 4-nitrophenol (0.11 mM) only in the case of 4-nitrocatechol (0.19 mM). Simple nitrocatechols showed two-fold Vmax values compared with 4-nitrophenol (68.6 nmol min–1 mg–1), while all disubstituted catechols exhibited much lower glucuronidation rate. Vmax/Km values were about 10 times higher for monosubstituted catechols compared to disubstituted ones. The kinetic parameters for COMT inhibitors were in the following order: Km nitecapone >> entacapone > tolcapone; Vmax nitecapone > entacapone > tolcapone; Vmax/Km tolcapone > nitecapone > entacapone. Conclusions. Nitrocatechols can in principle be good substrates of UGTs. However, substituents may have a remarkable effect on the enzyme kinetic parameters. The different behaviour of nitecapone compared to the other COMT inhibitors may be due to its hydrophilic 5-substituent. The longer elimination half-life of tolcapone in vivo compared to entacapone could not be explained by glucuronidation kinetics in vitro.  相似文献   
3.
A population-based survey was conducted in northern Finland in order to study the incidence rate and survival in patients with pharyngeal cancer diagnosed between 1986 to 1996. A total of 95 new patients with hypopharyngeal, oropharyngeal or nasopharyngeal cancers were identified. The overall age-adjusted incidence rates (per 100,000 years) were 1.28 in men and 0.60 in women, giving an overall incidence rate of 0.89. Most of the tumours were diagnosed at stage IV, and the median disease-specific survival times were 27.6 months for the patients with oropharyngeal cancer, 13.5 months for nasopharyngeal cancer and 17.7 for hypopharyngeal cancer. The most important factors that were associated with a poor prognosis were stage IV in oropharyngeal [Hazard ratio (HR) 3.68, 95% confidence interval (CI) 0.97-13.92] and hypopharyngeal cancer (HR 3.99, CI 1.51-10.67) and age over 65 years in nasopharyngeal cancer (HR 9.28, CI 1.79-47.99).  相似文献   
4.
The present experiment studied whether a dysfunction of the noradrenergic neurons is related to spatial learning impairment by investigating the levels of noradrenaline in the brain and periphery as well as the acquisition of water maze task in saline-pretreated young rats, in noradrenergic neurotoxin (DSP-4)-pretreated young rats and in saline-pretreated aged rats. Aged rats, which had an increased escape latency onto the hidden platform, revealed a decreased noradrenaline content in the heart, but not in the hippocampus, striatum, or hypothalamus, whereas DSP-4-pretreated rats had decreased noradrenaline content in the brain; the acquisition of water maze task was not impaired. These results suggest that the peripheral noradrenergic system can show age-related changes different from those in the central noradrenergic system, and they failed to provide support for the hypothesis that decreased activity of the central noradrenergic nerves is related to impairment in the acquisition of the water maze task.  相似文献   
5.
Social competence assessment and training has long focused on specific skills within the clinical setting. In addition, emphasis has been placed on identifying deficits relative to an arbitrary, often idiosyncratic metric. In this article, we discuss the importance of the principles that underlie communication and which are reflected in the range of behaviours described as social competence . We review methods we have found productive in the training of these principles with persons who have suffered traumatic brain injuries.  相似文献   
6.
7.
8.
Hakulinen T, Paunonen M, Laippala P. International Journal of Nursing Practice 1997; 3: 247–254
Relationships between demographic variables and family dynamics of childbearing families
In this study relationships between demographic variables and family dynamics of childbearing families in Finland were studied. The sample was 160 urban families expecting their first or second child in the third trimester of pregnancy. One-hundred and eighteen families participated in the study. The Family Dynamics Questionnaire (FDQ) and the Family Dynamics Measure (FDM) were used in this study. Most expectant parents reported their family was well-functioning. Mothers of higher socioeconomic status found more flexibility in their families than mothers of lower socioeconomic status. Fathers in families expecting their first baby reported more mutuality, role reciprocity and more stability than second-time fathers. The findings contribute cues for public health nurses and midwives regarding parity, socioeconomic status and family dynamics to provide more specific family guidance during the transition to parenthood. Realistic information on the changes in family dynamics after childbirth should be given to pregnant parents.  相似文献   
9.
Previous studies in the MPTP-lesioned primate model of Parkinson's disease have demonstrated that alpha(2) adrenergic receptor antagonists such as idazoxan, rauwolscine, and yohimbine can alleviate L-dopa-induced dyskinesia and, in the case of idazoxan, enhance the duration of anti-parkinsonian action of L-dopa. Here we describe a novel alpha(2) antagonist, fipamezole (JP-1730), which has high affinity at human alpha(2A) (K(i), 9.2 nM), alpha(2B) (17 nM), and alpha(2C) (55 nM) receptors. In functional assays, the potent antagonist properties of JP-1730 were demonstrated by its ability to reduce adrenaline-induced (35)S-GTPgammaS binding with K(B) values of 8.4 nM, 16 nM, 4.7 nM at human alpha(2A), alpha(2B), and alpha(2C) receptors, respectively. Assessment of the ability of JP-1730 to bind to a range of 30 other binding sites showed that JP-1730 also had moderate affinity at histamine H1 and H3 receptors and the serotonin (5-HT) transporter (IC(50) 100 nM to 1 microM). In the MPTP-lesioned marmoset, JP-1730 (10 mg/kg) significantly reduced L-dopa-induced dyskinesia without compromising the anti-parkinsonian action of L-dopa. The duration of action of the combination of L-dopa and JP-1730 (10 mg/kg) was 66% greater than that of L-dopa alone. These data suggest that JP-1730 is a potent alpha(2) adrenergic receptor antagonist with potential as an anti-dyskinetic agent in the treatment of Parkinson's disease.  相似文献   
10.
Even though the roles of different known or suggested prognostic factors in laryngeal cancer have been studied in detail, clinical stage at time of diagnosis and anatomic subsite of the tumour remain the only practical predictors of clinical outcome and offer the only guidelines in the planning of treatment. In this study, the relative roles of known demographic and clinical prognostic factors, in addition to four histopathological factors, were evaluated in a sample of 100 laryngeal carcinoma patients with multivariate analysis using the Cox regression model. In addition to advanced stage (stage III-IV) (relative hazard of death (HR) 8.9, p=0.01) and supraglottic disease (HR 5.6, p=0.02), high apoptotic index (HR 11.1, p=0.05) was significantly associated with poor survival. Cell proliferation, p53 and angiogenesis did not significantly affect the prognosis. In the future, high degree of apoptosis could be used to identify patients with poor prognosis in laryngeal cancer.  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