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   18648篇
  免费   1338篇
  国内免费   45篇
耳鼻咽喉   176篇
儿科学   636篇
妇产科学   501篇
基础医学   2534篇
口腔科学   202篇
临床医学   2282篇
内科学   3477篇
皮肤病学   342篇
神经病学   1948篇
特种医学   503篇
外国民族医学   5篇
外科学   2000篇
综合类   146篇
一般理论   14篇
预防医学   2286篇
眼科学   270篇
药学   1200篇
中国医学   13篇
肿瘤学   1496篇
  2024年   34篇
  2023年   246篇
  2022年   457篇
  2021年   841篇
  2020年   446篇
  2019年   800篇
  2018年   865篇
  2017年   611篇
  2016年   656篇
  2015年   705篇
  2014年   940篇
  2013年   1083篇
  2012年   1679篇
  2011年   1671篇
  2010年   829篇
  2009年   709篇
  2008年   1158篇
  2007年   1134篇
  2006年   1020篇
  2005年   958篇
  2004年   869篇
  2003年   685篇
  2002年   624篇
  2001年   74篇
  2000年   76篇
  1999年   72篇
  1998年   131篇
  1997年   88篇
  1996年   73篇
  1995年   57篇
  1994年   54篇
  1993年   42篇
  1992年   30篇
  1991年   28篇
  1990年   20篇
  1989年   20篇
  1988年   18篇
  1987年   15篇
  1986年   16篇
  1985年   14篇
  1984年   11篇
  1983年   14篇
  1982年   10篇
  1980年   13篇
  1979年   13篇
  1978年   9篇
  1977年   10篇
  1976年   15篇
  1972年   11篇
  1970年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
MUC1 represents a promising marker in breast cancer. However, due to the structural complexity of the MUC1 glycoprotein, multiple epitopes can be detected by monoclonal antibodies. This fact may be responsible for the contradictory results of previous investigations regarding the clinical and prognostic relevance of MUC1 expression in breast cancer. Therefore, we tried to evaluate the role of different glycosylated and non-glycoslyated MUC1 epitopes as well as other mucin-associated peptides (MUC2) and carbohydrates (Thomsen-Friedenreich antigen, sialyl-Lewisa, sialyl-Lewisx) as predictors of the clinical course and prognosis in mammary carcinomas. An immunohistochemical study applying numerous monoclonal antibodies (mabs) was performed to characterize the expression of a selected panel of MUC1 epitopes, and of MUC2, Thomsen-Friedenreich antigen, sialyl-Lewisa, and sialyl-Lewisx in a series of 140 patients with breast cancer. The results were correlated with clinicopathological variables as well as overall survival. Generally, more than 90% of the mammary cancers, were strongly stained with the MUC1-specific mabs. Especially ductal and lobular carcinomas were strongly MUC1- and sialyl Lewisa-positive, whereas MUC2 binding was significantly elevated in mucinous neoplasms. Associations between the immunoreactivity of any mab under study and tumor progression as reflected by pTNM staging could not be observed. However, expression of the sialylated MUC1 epitope detected by mab MY1.E12 was revealed as a favourable independent prognostic factor. These results confirm that MUC1 is generally strongly expressed in mammary carcinomas. As an exception, mucinous carcinomas are significantly less MUC1 reactive, but strongly express MUC2. Our data suggest that only the presence of a sialylated short-chain MUC1 glycoform is associated with a better prognosis, whereas the other molecules under study are not correlated with the course of disease and survival probability.  相似文献   
992.
993.
994.
OBJECTIVES: To compare the costs and effectiveness of adjustable maintenance dosing with budesonide/formoterol in a single inhaler versus fixed dosing in adults with asthma. METHODS: In this prospective, randomised, open-label, parallel-group, multicentre trial conducted in Germany, patients with asthma received budesonide/formoterol 160 microg/4.5 microg in a single inhaler (Symbicort Turbuhaler with two inhalations twice daily for a 4-week run-in period. Patients were then randomised to either adjustable maintenance dosing (one inhalation twice daily, stepping up to four inhalations twice daily for 1 week if asthma worsened; n=1679) or fixed dosing (two inhalations twice daily; n=1618) for 12 weeks. The primary efficacy variable was the change in health-related quality of life (HR-QOL), measured using the Asthma Quality of Life Questionnaire (standardised) during the randomised treatment period. Resource utilisation data were collected in parallel and combined with German unit costs to estimate direct and indirect costs (year 2001 values). RESULTS: Both treatment regimens were equally effective in maintaining HR-QOL and asthma control during the randomised treatment period. However, overall, patients in the adjustable maintenance dosing group took fewer daily inhalations of budesonide/formoterol than those in the fixed-dosing group (mean: 2.63 vs 3.82 inhalations; p<0.001). Adjustable maintenance dosing was associated with significantly lower asthma-related direct costs compared with fixed dosing (mean: 221 euro vs 292 euro; p<0.001). This pattern was maintained when patients were stratified into those with peak expiratory flow (PEF) of 60% to <80% predicted normal and those with PEF of>/=80% predicted normal and when total costs were considered. CONCLUSION: Adjustable maintenance dosing with budesonide/formoterol in a single inhaler maintained HR-QOL in adult patients with asthma at a significantly lower cost than fixed dosing.  相似文献   
995.
The current review addresses the following 3 frequently encountered challenges in the design and analysis of population pharmacokinetic studies in pediatrics: (1) body size adjustments during the development of pharmacostatistical models, (2) design and validation of limited sampling strategies, and (3) the integration of historical priors in data analysis and trial simulation. Size adjustments with empiric approaches based on body weight or body surface area have frequently proven as a pragmatic tool to overcome large size differences in a pediatric study population. Allometric size adjustments, however, provide a more mechanistic, physiologically based approach that, if used a priori, allows delineation of the effect of size from that of other covariates that show a high degree of collinearity. The frequent lack of dense data sets in pediatric clinical pharmacology because of ethical and logistic constraints in study design can be overcome with the application of D-optimality-based limited sampling schemes in combination with Bayesian and nonlinear mixed-effects modeling approaches. Empirically based dose selection and clinical trial designs for pediatric clinical pharmacology studies can be improved by applying clinical trial simulation techniques, especially if they integrate adult and pediatric in vitro and/or in vivo data as historic priors. Although integration of these concepts and techniques in population pharmacokinetic analyses is not only limited to pediatric research, their application allows researchers to overcome some major hurdles frequently encountered in pharmacokinetic studies in pediatrics and, thus, provides the basis for additional clinical pharmacology research in this previously insufficiently studied fraction of the general population.  相似文献   
996.
Rationale Previous studies have shown that neonatal quinpirole treatment which results in long-term dopamine D2 receptor supersensitization (D2 receptor priming) produces cognitive deficits in preweanling and adult rats behaviorally tested on the Morris water task (MWT).Objective This study was designed to analyze whether pretraining administration of the D2 antagonist eticlopride alleviates cognitive deficits produced by neonatal quinpirole treatment.Methods Both male and female Sprague–Dawley rats were treated with quinpirole HCl (1 mg/kg) or saline from postnatal days 1 to 21. From P22 to P24, rats were tested on the place version of the MWT in which a hidden platform remains stationary throughout training. From P25 to P28, rats were tested on the match-to-place version of the MWT, and rats are given a pair of daily training trials to locate the hidden platform that was moved to a new location each day. Fifteen minutes before each training session, rats were intraperitoneally administered with eticlopride (0.01 or 0.02 mg/kg) or saline.Results Pretraining eticlopride treatment alleviated cognitive deficits produced by neonatal quinpirole treatment in both male and female rats on the place version of the MWT, as well as in males tested on the match-to-place version of the MWT. However, there were no significant deficits produced by neonatal quinpirole treatment in females tested on the match-to-place version of the MWT, and control males demonstrated superiority over control females on this version of the task.Conclusions Pretraining administration of the dopamine D2 antagonist eticlopride alleviated cognitive deficits produced by neonatal quinpirole treatment. However, it appears that the dopamine D2 receptor may have a more important influence on cognitive performance in males than in females, which may be related to increased sensitivity of the D2 receptor in males.  相似文献   
997.

Rationale and objectives

In schizophrenia research, most of the functional imaging studies have been performed in psychotic patients, but little is known about brain areas involved in the expression of psychotic-like symptoms in animal models. The objective of this study was to visualize and compare brain activity abnormalities in a neurodevelopmental and a pharmacological animal model of schizophrenia.

Methods

Blood perfusion of specific brain areas, taken as indirect measure of brain activity, was investigated in adult rats following either neonatal ventral hippocampal lesion or acute administration of phencyclidine. Quantitative perfusion magnetic resonance imaging was performed on five frontal brain slices using the continuous arterial spin labeling technique. The mean perfusion was calculated in several brain structures, which were identified on anatomical images.

Results

Lesioned animals exhibiting deficits in prepulse inhibition of the startle reflex showed a significant blood perfusion increase in the nucleus accumbens, basolateral amygdala, ventral pallidum, entorhinal–piriform cortex, orbital prefrontal cortex, and in the bed nucleus of the stria terminalis, and a decrease of perfusion in the temporal cortex. Similar effects were seen following acute phencyclidine administration in naïve animals.

Conclusion

Our data point out specific cortical and subcortical brain areas involved in the development of psychotic-like symptoms in two different animal models of schizophrenia. The observed brain activity abnormalities are reminiscent of classical neuroimaging findings described in schizophrenic patients.
  相似文献   
998.
To investigate the importance of secondary structure on peptide deamidation in the solid state, two cyclic beta-turn peptides and their linear analogs were used as models of Asn residues in structured and unstructured domains, and incorporated into poly(vinyl pyrrolidone) (PVP)-based lyophilized solids. The secondary structure of the model peptides was determined in solution and the solid state using a combination of nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), and Fourier transform infrared (FTIR) spectroscopy. The model beta-turn cyclic peptides were found to be type II beta-turns while the linear analogs were determined to be predominantly unstructured. Quantitatively, the cyclic peptides consisted of approximately 80% beta-turn while the linear analogs contained only 30%-35% beta-turn. To characterize the solid environment, T(g), and moisture content of the solid-state formulations were determined. Accelerated stability studies were conducted in the solid state at 37 degrees C using formulations lyophilized from solutions at pH 8.8 (0.1 M borate buffer). The effect of matrix mobility on solid-state deamidation was investigated by altering the moisture content through variation of relative humidity or the addition of a plasticizer. Cyclic peptides degraded 1.2-8 times slower than the linear analogs under all of the conditions studied. The observed rate constants, however, for all of the peptides decreased dramatically (four orders of magnitude) in the glassy solids. This suggests the greater importance of matrix mobility in solid-state degradation. Molecular dynamics (MD) simulations were also performed to explore the low energy, preferred state of the peptides, and determine the structure around the beta-turn.  相似文献   
999.
OBJECTIVE: The contribution of psychiatric comorbidity to cognitive status was assessed in a sample of treatment-seeking alcoholics who met criteria to participate in studies of effects of chronic alcohol misuse on brain structure and cognition. METHOD: Alcoholic men (n = 43) and women (n = 21) who responded to notices about a research study were screened, clinically assessed and administered Wechsler Memory and Intelligence tests after 3 months of sobriety, on average. Cognitive performance was compared with that of an age-matched sample of healthy controls (n = 51). RESULTS: As a group, the alcoholics achieved significantly lower scores than controls on summary indices of the Wechsler Memory and Adult Intelligence Scales and showed greater decline from estimated premorbid intelligence levels than controls. Almost 60% of the alcoholics had at least one additional psychiatric (mood or anxiety) or past substance-dependence comorbidity. There were no marked sex differences in patterns of comorbidity. Comorbid alcoholics were younger, had consumed less alcohol over their lifetime and performed between noncomorbid alcoholics and controls on all tests. CONCLUSIONS: Mood and anxiety comorbidity did not necessarily compound poor cognitive test performance associated with chronic alcohol misuse. While unexpected, this finding suggests that, in this sample, poorer cognitive performance was more a function of alcoholism per se than nonalcoholic comorbidity.  相似文献   
1000.
Phospholipidosis is the excessive accumulation of intracellular phospholipids in cell lysosomes. Drugs that induce this disease often share common physiochemical properties and are collectively classified as cationic amphiphilic drugs (CADs). Although the cause of phospholipidosis and morphologic appearance of affected lysosomes have been studied extensively, less is known about the physiologic effects of the condition. In the current study, U-937 cells were incubated with the CADs amiodarone (2.5-10 microg/mL) and imipramine (2.5-20 microg/mL). Treatment of U-937 cells with these compounds for 96 h resulted in concentration-related increases in phospholipids, as assessed by flow cytometry using the fluorophore nile red. These results were verified by measuring the concentrations of choline-derived phospholipids, which were significantly increased in drug-treated cells. Cell number in amiodarone (10 microg/mL) and imipramine (20 microg/mL) cultures following the 96-h incubation period were markedly reduced compared to control cultures. These observations suggested that accumulation of cellular phospholipids could inhibit cell proliferation. Flow cytometric analysis revealed a decrease in the percentage of cells in the S-phase of the cell cycle following drug treatment, yet DNA replication still occurred in a significant portion of cells. Interestingly, amiodarone and imipramine induced apoptosis in U-937 cells as shown by annexin V-FITC staining and DNA fragmentation. Enzymatic assays demonstrated that amiodarone and imipramine induced the activity of caspases 2 and 3. These results suggest that disruption of cell lysosomes in U-937 cells following accumulation of phospholipids does not cause a cell cycle arrest but instead induces apoptosis by activation of caspase pathways.  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