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   7586篇
  免费   759篇
  国内免费   11篇
耳鼻咽喉   130篇
儿科学   218篇
妇产科学   156篇
基础医学   1096篇
口腔科学   182篇
临床医学   914篇
内科学   1555篇
皮肤病学   122篇
神经病学   539篇
特种医学   446篇
外科学   979篇
综合类   203篇
预防医学   710篇
眼科学   186篇
药学   399篇
中国医学   9篇
肿瘤学   512篇
  2021年   119篇
  2020年   63篇
  2019年   96篇
  2018年   126篇
  2017年   103篇
  2016年   121篇
  2015年   136篇
  2014年   169篇
  2013年   219篇
  2012年   375篇
  2011年   334篇
  2010年   216篇
  2009年   212篇
  2008年   300篇
  2007年   328篇
  2006年   282篇
  2005年   254篇
  2004年   262篇
  2003年   255篇
  2002年   220篇
  2001年   241篇
  2000年   227篇
  1999年   216篇
  1998年   119篇
  1997年   120篇
  1996年   117篇
  1995年   91篇
  1994年   92篇
  1993年   100篇
  1992年   167篇
  1991年   168篇
  1990年   174篇
  1989年   191篇
  1988年   182篇
  1987年   160篇
  1986年   178篇
  1985年   157篇
  1984年   130篇
  1983年   135篇
  1982年   81篇
  1981年   59篇
  1980年   63篇
  1979年   86篇
  1978年   71篇
  1977年   61篇
  1976年   65篇
  1975年   62篇
  1974年   68篇
  1973年   54篇
  1971年   56篇
排序方式: 共有8356条查询结果,搜索用时 15 毫秒
11.
OBJECTIVE: The aim of this study was to assess the severity of epilepsy and its effect on patients lives, and to describe patients' use of and attitudes to health care. METHOD: A questionnaire was sent to 595 people with epilepsy identified from 14 general practices in north-west Bristol. All patients aged 16 years and over receiving anti-epileptic medication for their epilepsy were included in the study. Areas investigated included severity of epilepsy and its effect on quality of life, anti-epileptic medication and its perceived effect, health care utilization and preferences for health care. RESULTS: Seizure frequency was strongly associated with adverse effects of epilepsy. Attacks of epilepsy were experienced at least monthly by 20.4% (95% confidence intervals (Cl) 17.0-23.7%) of patients, 29.4% (25.4-33.4%) took more than one anti-epileptic drug, 56.1% (50.1-62.2%) reported drug side effects, 74.1% (70.3-77.8%) would prefer to receive all or most of their epilepsy care in a general practice setting, and 69.8% (63.5- 76.2%) would like contact with a primary care-based epilepsy specialist nurse. During the previous year 42.4% (35.9-48.8%) of patients had not seen a doctor about their epilepsy. Of patients who had attended the general practice only 13.4% (9.6-17.2%) had regular arrangements to see their GP about epilepsy. Patients receiving both primary and secondary care had the greatest needs and wants for improved care. CONCLUSIONS: Structured care, including regular appointments, co-ordination of primary and secondary care, and increased monitoring and discussion, may improve the quality of life of people with epilepsy, but requires evaluation.   相似文献   
12.
 Accurate, timed urine collections for the measurement of glomerular filtration rate (GFR) may be impractical in infants or in patients with urological abnormalities. GFR may be measured without urine collection using a constant subcutaneous infusion of iothalamate. We compare the infusion clearance with conventional renal clearance in 14 children and young adults. The mean clearance ratio (infusion clearance/renal clearance ± 1 SD) was 0.99±0.1 and the mean discrepancy between the two methods was 8.5%±4.7%. The 95% limits of agreement for the ratio of the two methods are 0.83–1.23. These data indicate that subcutaneous infusion of iothalamate is a practical method for measuring GFR in children without a urine collection. Received March 18, 1996; received in revised form February 12, 1997; accepted March 26, 1997  相似文献   
13.
14.
Alcoholism and dental management   总被引:1,自引:0,他引:1  
Alcohol is widely used and abused in the United States. Because alcohol affects all parts of the body, it is important for dentists as well as all other medical practitioners to be aware of the signs of alcoholism. Some dental problems occur more frequently in alcoholic patients, and often general dental care for these patients must be modified.  相似文献   
15.
A number of anorexic young women develop bulimia, a condition in which binge eating is driven so intensely they cannot resist it. Although this drive has the character of a compulsion the patients do not as a rule suffer from obsessional-compulsive neurosis. A questionnaire was developed and used to determine whether similar compulsive drives manifest themselves in restricting anorexics and whether there are compulsive features resembling patients with compulsive personality disorder (as described in DSM-III) in eating disorders. A total of 162 patients were studied, comprising 42 controls, 30 depressed patients, 34 non-bingeing anorexics, 28 bingeing anorexics and 28 compulsive patients. The questionnaire was shown to be a stable instrument and, on the compulsion scale, the anorexics, bulimics and compulsive patients all scored very highly (mean +/- S.E.; 32.1 +/- 1.9, 35.8 +/- 1.9, 28.0 +/- 2.2, respectively) compared to the controls (13.1 +/- 1.1, p < 0.005). The compulsive patients did not have anorexia-type eating disorders. It was concluded that many of the factors which underlie compulsive personality disorder are present in primary eating disorders and the compulsive nature of anorexia could not be ignored when treatment was considered. The difference between compulsive behaviour and addiction is discussed in the light of the failure of long-term naloxone infusion to cure severe anorexia, even though some patients had dramatic weight gains associated with the antilipolytic action of naloxone.  相似文献   
16.
Spinal cord injury (SCI) produces an increase in extracellular excitatory amino acid (EAA) concentrations that results in glutamate receptor-mediated excitotoxic events. An important class of these receptors is the metabotropic glutamate receptors (mGluRs). mGluRs can activate a number of intracellular pathways that increase neuronal excitability and modulate neurotransmission. Group I mGluRs are known to modulate EAA release and the development of chronic central pain (CCP) following SCI; however, the role of group II and III mGluRs remains unclear. To begin evaluating group II and III mGluRs in SCI, we administered the specific agonists for group II, APDC, or group III, L-AP4, by interspinal injection immediately following SCI. Contusion injury was produced at spinal segment T10 with a New York University impactor (12.5-mm drop, 10-g rod 2 mm in diameter) in 30 adult male Sprague-Dawley rats (175-200 g). Evoked and spontaneous behavioral measures of CCP, locomotor recovery, changes in mGluR expression, and amount of spared tissue were examined. Neither APDC nor L-AP4 affected locomotor recovery or the development of thermal hyperalgesia; however, L-AP4 and APDC attenuated changes in mechanical thresholds and changes in exploratory behavior indicative of CCP. APDC- and L-AP4-treated groups had higher expression levels of mGluR2/3 at the epicenter of injury on post contusion day 28; however, there was no difference in the amount of spared tissue between treatment groups. These results demonstrate that treatment with agonists to group II and III mGluRs following SCI affects mechanical responses, exploratory behavior, and mGluR2/3 expression without affecting the amount of tissue spared, suggesting that the level of mGluR expression after SCI may modulate nociceptive responses.  相似文献   
17.
This study examines the relationship between renin levels and physiologic reactivity to stressors. Seventy-five normotensive and mildly hypertensive men were studied on a high salt diet (200 mEq/day Na) and on a low salt diet (10 mEq/day Na). Renin, plasma catecholamines, heart rate, and blood pressure were examined at rest, after standing in place for 8 minutes, and after a brief mathematics task. Renin levels increased in response to the stressor tasks, particularly on the low salt diet. The change in diastolic pressure in response to the stressor tasks was correlated with the change in renin (r = 0.45, p less than 0.001) but not with the change in norepinephrine. The combination of change in renin and norepinephrine levels accounted for 21% of the variance in predicting diastolic pressure reactivity (p less than 0.0015).  相似文献   
18.
Summary The metabolism of adenosine and its effects on phosphoribosylpyrophosphate, PP-ribose-P, dependent nucleotide synthesis were studied using erythrocytes from patients with adenosine deaminase and hypoxanthine phosphoribosyltransferase deficiency as models. The phosphorylation of adenosine was progressively inhibited by concentrations of adenosine greater than 1 µmol L–1 for control and ADA deficient erythrocytes. There was essentially no initial rate of phosphorylation at 30 µmol L–1 adenosine. Adenosine, 1 µmol L–1, also caused a 60% reduction in PP-ribose-P concentration in ADA deficient erythrocytes. For HPRT deficient erythrocytes in which ADA activity was blocked by coformycin, 10 µmol L–1 inosine stimulated PP-ribose-P dependent nucleotide synthesis from adenine, whereas, 10 µmol L–1 adenosine inhibited nucleotide synthesis. These observations suggest that adenosine phosphorylation and PP-ribose-P dependent nucleotide synthesis are inhibited under conditions in which adenosine accumulates, such as in hereditary or pharmacologically induced ADA deficiency.  相似文献   
19.
OBJECTIVE: To use the over-complete discrete wavelet transform (OCDWT) to further examine the dual structure of auditory brainstem response (ABR) in the dog. METHODS: ABR waveforms recorded from 20 adult dogs at supra-threshold (90 and 70dBnHL) and threshold (0-15dBSL) levels were decomposed using a six level OCDWT and reconstructed at individual scales (frequency ranges) A6 (0-391Hz), D6 (391-781Hz), and D5 (781-1563Hz). RESULTS: At supra-threshold stimulus levels, the A6 scale (0-391Hz) showed a large amplitude waveform with its prominent wave corresponding in latency with ABR waves II/III; the D6 scale (391-781Hz) showed a small amplitude waveform with its first four waves corresponding in latency to ABR waves I, II/III, V, and VI; and the D5 scale (781-1563Hz) showed a large amplitude, multiple peaked waveform with its first six waves corresponding in latency to ABR waves I, II, III, IV, V, and VI. At threshold stimulus levels (0-15dBSL), the A6 scale (0-391Hz) continued to show a relatively large amplitude waveform, but both the D6 and D5 scales (391-781 and 781-1563Hz, respectively) now showed relatively small amplitude waveforms. CONCLUSIONS: A dual structure exists within the ABR of the dog, but its relative structure changes with stimulus level. SIGNIFICANCE: The ABR in the dog differs from that in the human both in the relative contributions made by its different frequency components, and the way these components change with stimulus level.  相似文献   
20.
Reversal of opioid effects by naloxone (NX) can lead to significant cardiovascular problems. We have reported previously that hypercapnic dogs develop greater increases in blood pressure and plasma catecholamine (CA) levels than hypocapnic ones when reversed with naloxone. We have also demonstrated differences between NX and nalbuphine (NBPH) in producing excitatory adrenergic responses when administered during normocapnia. The present study was designed to investigate possible dissimilarities in cardiovascular and sympathetic events after administration of either NX or NBPH in dogs made hypercapnic following fentanyl administration. After induction of anaesthesia with thiopentone and intubation, two groups of dogs were maintained with controlled ventilation on enflurane in oxygen anaesthesia and given 50 micrograms.kg-1 fentanyl IV. This caused a significant decrease in heart rate (HR) (P less than 0.001), mean arterial blood pressure (MAP) (P less than 0.001), and plasma concentrations of norepinephrine (NE) (P less than 0.002). Then, ventilation was decreased to produce a PaCO2 of 60 mmHg; this was accompanied by a significant elevation in plasma level of both epinephrine (EPI) (P less than 0.02) and NE (P less than 0.001). Administration of 20 micrograms.kg-1 NX to six dogs resulted in immediate increases in HR (P less than 0.01) and MAP (P less than 0.01), and a further rise in CA levels to greater than pre-fentanyl baseline values. In six other dogs, NBPH (0.3 mg.kg-1) caused increases in HR (P less than 0.001) and MAP (P less than 0.001) only, and the MAP rise was significantly less than that seen in the NX group (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)  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