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   6385篇
  免费   547篇
  国内免费   21篇
耳鼻咽喉   69篇
儿科学   254篇
妇产科学   188篇
基础医学   809篇
口腔科学   88篇
临床医学   728篇
内科学   1461篇
皮肤病学   139篇
神经病学   604篇
特种医学   300篇
外科学   974篇
综合类   80篇
一般理论   6篇
预防医学   549篇
眼科学   50篇
药学   380篇
中国医学   15篇
肿瘤学   259篇
  2023年   49篇
  2022年   54篇
  2021年   97篇
  2020年   94篇
  2019年   104篇
  2018年   144篇
  2017年   135篇
  2016年   137篇
  2015年   143篇
  2014年   153篇
  2013年   285篇
  2012年   324篇
  2011年   296篇
  2010年   210篇
  2009年   191篇
  2008年   291篇
  2007年   302篇
  2006年   268篇
  2005年   205篇
  2004年   210篇
  2003年   175篇
  2002年   172篇
  2001年   175篇
  2000年   180篇
  1999年   154篇
  1998年   108篇
  1997年   101篇
  1996年   102篇
  1995年   81篇
  1994年   72篇
  1993年   83篇
  1992年   154篇
  1991年   139篇
  1990年   143篇
  1989年   134篇
  1988年   136篇
  1987年   126篇
  1986年   124篇
  1985年   99篇
  1984年   97篇
  1983年   82篇
  1982年   46篇
  1981年   47篇
  1978年   43篇
  1977年   48篇
  1976年   40篇
  1975年   47篇
  1974年   39篇
  1973年   39篇
  1972年   40篇
排序方式: 共有6953条查询结果,搜索用时 15 毫秒
101.

Objectives

Implementation intentions are ‘IF-THEN’ plans that encourage goal-intended behaviour. This study was designed to test whether an intervention encouraging the formation of implementation intentions can reduce self-harm in the community.

Design

A randomized controlled design was used.

Methods

At pre-intervention, outcome variables (self-harm in both specified and unspecified critical situations and suicidality) and potential moderators of implementation intentions (goal intention, mental imagery, and exposure to self-harm) were measured using self-report questionnaires. The participants (N = 469, aged 18–66 years, 86.4% female, 6.8% male and 6.7% other) were then randomized to either an experimental (implementation intention) or control task. At three-months post-intervention, self-report questionnaires were used again to measure the outcome variables.

Results

There were no overall differences between the conditions at post-intervention. However, goal intention and mental imagery, but not exposure to self-harm, moderated the effects of condition on self-harm in specified critical situations. At high (mean + 1SD) levels of both goal intention and mental imagery, the experimental condition reported self-harming less frequently in the situations specified in their implementation intentions.

Conclusions

Implementation intentions therefore represent a useful intervention for reducing self-harm in specified critical situations for people in the community who wish to avoid self-harm and those who frequently experience self-harm and suicide related mental imagery.  相似文献   
102.
The authors prospectively evaluated the efficacy of caudal epidural block versus local infiltration combined with ilioinguinal/iliohypogastric block for analgesia after inguinal herniorrhaphy with laparoscopic inspection of the peritoneum. During standardized anesthetic care, 24 children were randomized to Group I (caudal epidural block with 1.2 mL/kg of 0.25% bupivacaine) or to Group II (local infiltration with an ilioinguinal/iliohypogastric block). Postoperative pain scores were significantly lower at all four evaluation points in Group I than in Group II. Patients in Group I had a significantly decreased requirement for supplemental intravenous fentanyl. Intra-operative requirements for isoflurane were decreased in Group I. The expired concentration of isoflurane was 0.4 +/- 0.1 (mean +/- SEM) in Group I and 1.5 +/- 0.3 in Group II. Time to extubation was 3.8 +/- 0.5 minutes in Group I and 8.2 +/- 1.1 minutes in Group II. The time from arrival in the postanesthesia care unit until discharge home was 113 +/- 3 minutes in Group I and 152 +/- 11 minutes in Group II. Caudal epidural block was more effective than local infiltration in controlling pain after herniorrhaphy with laparoscopy in children and resulted in earlier discharge home.  相似文献   
103.
104.
Olanzapine, an atypical antipsychotic, has a broad receptor binding profile, which may account for its pharmacological effects in schizophrenia. In vitro receptor binding studies showed a high affinity for dopamine D2, D3, and D4 receptors; all 5-HT2 receptor subtypes and the 5-HT6 receptor; muscarinic receptors, especially the M1 subtype: and alpha 1-adrenergic receptors. In vivo studies showed that olanzapine had potent activity at D2 and 5-HT2A receptors, but much less activity at D1 and muscarinic receptors, and that it inhibited dopaminergic neurons in the A10 but not the A9 tract, suggesting that this agent will not cause extrapyramidal side-effects (EPS). Microdialysis studies showed that olanzapine increased the extracellular levels of norepinephrine and dopamine, but not 5-HT, in the prefrontal cortex, and increased extracellular dopamine levels in the neostriatum and nucleus accumbens, areas of the brain associated with schizophrenia. Studies of gene expression showed that olanzapine 10 mg/kg also increased Fos expression in the prefrontal cortex, the dorsolateral striatum, and the nucleus accumbens. These findings are consistent with the effectiveness of olanzapine on both negative and positive symptoms and suggest that, with careful dosing, olanzapine should not cause EPS.  相似文献   
105.
Specific nutrition standards are now developed by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) in order to improve the nutritional status in hospitalized patients. We investigated the use of clinical nutrition in Danish hospitals and compared it with the standards of JCAHO by doing a questionnaire-based investigation among doctors and nurses randomly selected in 40 hospitals including internal medicine, gastroenterology, oncology, orthopedic departments and intensive care units (ICU).Overall, 857 (43.4%) responded to the questionnaire (doctors: 395, nurses: 462). Seventy-seven percent stated that nutritional assessment ought to be performed on admission, but only 24% stated that it was a routine procedure. Forty percent found it difficult to identify risk-patients, and 52% needed specific screening tools. Twenty-two percent registered body weight in all patients, and 18% registered nutrient intake routinely. Eighty-four percent found that a nutrition plan should be described in the patient record, but 39% found it difficult to set up an individual plan, and 79% expressed a need for specific guidelines. Eighty-four percent would only accept a patient being on isotonic glucose and/or electrolyte infusion for < 5 days (42% for < 2 days), and 33% would only accept a weight loss of 5% before active nutrition was initiated. About 50% would be restrictive in supplying enteral or parenteral nutrition to patients with impaired liver or kidney function. Twenty-seven percent did not use active nutritional therapy at all. Seventy-six percent found that nutritional assessment should be performed during hospital stays, but only 23% monitored the nutritional status. Sixty-eight percent stated that responsibility should be assigned to one or more persons, but this was the case in only 20%The use of clinical nutrition in Danish hospitals did not fulfill the standards for nutrition support according to the criteria established by JCAHO. Special efforts should be aimed at education, specific screening tools and introduction of guidelines in clinical nutrition.  相似文献   
106.
A history of placental dysfunction and risk of placental abruption   总被引:1,自引:0,他引:1  
In a population-based historic cohort study, we assessed the possible association of fetal growth retardation, preterm birth and pregnancy-induced hypertension in the immediately preceding pregnancy with placental abruption in the current pregnancy, which would suggest a shared aetiological factor. We also assessed whether chronic hypertension, diabetes mellitus and a history of Caesarean section are associated with placental abruption. Preterm birth and small-for-gestational-age (SGA) in the immediately preceding delivery were associated with an increased risk of placental abruption with unadjusted odds ratios (ORs) of 2.1 [95% CI = 1.9, 2.4] and 1.6 [95% CI = 1.5, 1.8] respectively. Women with a history of an SGA preterm birth in the immediately preceding delivery and an appropriate-for-gestational-age infant in the current had an adjusted OR of 3.2 [95% CI = 2.3, 4.5]. The adjusted odds ratio of placental abruption in women who had pregnancy-induced hypertension in the previous pregnancy, but not in the current, was 1.4 [95% CI = 1.2, 1.7]. Women who delivered a preterm or SGA infant in the previous delivery and had chronic hypertension or diabetes mellitus in the current had adjusted ORs of 2.3–5.7 and 2.5–6.0 respectively. Caesarean section in the previous delivery increased the risk of placental abruption by 40%. These results suggest that pregnancy-induced hypertension, intrauterine growth retardation, preterm delivery and placental abruption share an aetiological factor or represent different clinical expressions of recurring placental dysfunction. Chronic hypertension and diabetes mellitus may cause or aggravate such dysfunction thus causing placental abruption. A history of Caesarean section is associated with an increased risk of placental abruption.  相似文献   
107.
Automatic border detection (ABD) has been developed as a potentially useful means for evaluating ventricular function on line in an automatic fashion. Its success with tracking left ventricular function is established, but little is known about its ability to assess right ventricular (RV) function. Accordingly, 20 patients with severe pulmonary hypertension due to chronic thromboembolic disease underwent standard two-dimensional echocardiography and imaging with ABD before and after pulmonary thromboendarterectomy to correct pulmonary hypertension. ABD-derived results were compared to manually planimetered RV areas calculated from the apical four-chamber view. Doppler tricuspid regurgitant velocity fell significantly with surgery from 4.4 ± 0.6 to 2.9 ± 0.7 m / sec (P < 0.001). The mean values for RV areas derived by manual planimetry and ABD were similar, as was fractional area shortening, which improved significantly with surgery (manual 0.24 ± 0.01 preoperative vs 0.31 ± 0.11 postoperative, P < 0.05; and ABD 0.19 ± 0.05 preoperative vs 0.32 ± 0.15 postoperative, P < 0.001). There was, however, very little correlation between the individual values for ABD versus manually derived RV areas and fractional area shortening, with the best correlation being the RV end-diastolic areas after surgery (y = 0.684x + 7.9, r = 0.564, P = 0.01). These results demonstrate that both manually planimetered RV areas and those determined by ABD can adequately follow changes in ventricular function over time. However, variability within each technique may prevent direct comparison of the absolute values of the two techniques.  相似文献   
108.
109.
Various N--hydroxyalkyl derivatives of N-acyl amino acids and di- and tripeptides were prepared by hydrolysis or aminolysis of N-acyl 5-oxazolidinones. The stability of these derivatives was studied in aqueous solution as a function of pH. The compounds were all degraded quantitatively to their parent N-acylated amino acid or peptide and aldehyde but with vastly different rates. At pH 7.4 and 37°C the half-lives of decomposition ranged from 4 min to 1500 hr. The structural factors influencing the stability included both steric and polar effects within the acyl and N--hydroxyalkyl moieties as well as within the amino acid attached to the N--hydroxyalkylated N-acyl amino acid. Whereas the N-benzyloxycarbonyl (Z) derivatives of the dipeptides Gly-L-Leu and Gly-L-Ala were readily hydrolyzed by carboxypeptidase A, the N-hydroxymethylated compounds, i.e., Z-Gly(CH2OH)-Leu and Z-Gly(CH2OH)-Ala, were resistant to cleavage by the enzyme as revealed by their similar rates of decomposition in the presence or absence of the enzyme at pH 7.4 and 37°C. The results suggest that N--hydroxyalkylation of a peptide bond protects not only this bond but also an adjacent peptide bond against proteolytic cleavage. Since the N--hydroxyalkyl derivatives are readily bioreversible, undergoing spontaneous hydrolysis at physiological pH, this prodrug approach promises to overcome the enzymatic barrier to absorption of various peptides.  相似文献   
110.
Facial pain     
Summary In a prospective material of 1052 patients the precipitating factors, associated symptoms, psychological and neurological deficits have been examined.Mastication and talking are the most frequently occurring precipitating factors, 76% as regards Neuralgia, with typical starting difficulties. As regards Non-neuralgiform Pain 24%, with precipitation late in the masticatory process. There were trigger zones in 50% of the cases of Typical Trigeminal Neuralgia and in 9% of the patients with Non-neuralgiform Pain. In a series of cases the jaw joint is perceived as a trigger zone. Cold precipitates pain in 48%–39%. Other precipitating factors are much more rare-psychological stress in 15% of the patients with Non-neuralgiform Pain, however.Vegetative associated symptoms were relatively frequent, lacrimation occurred in 31% of the cases of Typical Trigeminal Neuralgia and in 20% of the cases of Non-neuralgiform Pain. Rhinorrhea and salivation were less frequent. In terms of figures migrainoid associated symptoms had no connection with vegetative associated symptoms or with pain in the eye.In 11 % of the patients pain occurred most frequently during the night and in 20% the frequency of pain was the same day and night. About 1/3 of the patients with Neuralgia experienced seasonal variations.Tenderness of foramina is a symptom of no significance. Very few patients had primary sensory loss. No eye or ear symptoms have been found which may be referred to as the patho-anatomical basis of the pain.About 1/3 of the patients with Non-neuralgiform Pain had psychological symptoms whereas hardly any patients with Neuralgia had them. MMPI test performed on a small matched material showed no difference between Neuralgia and Non-neuralgiform Pain.In material B an examination has been made of the jaw joint arthrosis symptoms. A restriction of the diagnosis of arthrosis has had the effect that it must be recognized that patients with facial pain do not have the high frequency of jaw joint diseases previously assumed. As was also the case in a series of normal material previously published, between 1/5 and 1/3 of the patients with Neuralgia had jaw joint arthrosis which was due to old age.This study has not revealed any connection between previous diseases, the onset of pain, the character and course of the pain, the character of the attack, the localization of pain, precipitating factors, associated symptoms and symptoms of loss on the one hand and the patho-anatomical substratum on the other.The psychological examinations were performed by Mr. Peter Bruun, chief psychologist, for whose cooperation I am grateful.  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