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   2109篇
  免费   94篇
  国内免费   14篇
耳鼻咽喉   29篇
儿科学   50篇
妇产科学   20篇
基础医学   243篇
口腔科学   97篇
临床医学   179篇
内科学   325篇
皮肤病学   19篇
神经病学   215篇
特种医学   119篇
外科学   361篇
综合类   3篇
一般理论   6篇
预防医学   175篇
眼科学   64篇
药学   216篇
肿瘤学   96篇
  2023年   5篇
  2022年   12篇
  2021年   17篇
  2020年   23篇
  2019年   29篇
  2018年   28篇
  2017年   35篇
  2016年   45篇
  2015年   34篇
  2014年   59篇
  2013年   100篇
  2012年   112篇
  2011年   126篇
  2010年   82篇
  2009年   85篇
  2008年   156篇
  2007年   130篇
  2006年   156篇
  2005年   155篇
  2004年   152篇
  2003年   121篇
  2002年   131篇
  2001年   38篇
  2000年   18篇
  1999年   23篇
  1998年   36篇
  1997年   26篇
  1996年   19篇
  1995年   27篇
  1994年   20篇
  1993年   13篇
  1992年   13篇
  1991年   14篇
  1990年   6篇
  1989年   12篇
  1988年   9篇
  1987年   8篇
  1986年   10篇
  1985年   20篇
  1984年   14篇
  1983年   20篇
  1982年   14篇
  1981年   23篇
  1980年   11篇
  1979年   7篇
  1978年   5篇
  1977年   4篇
  1976年   4篇
  1972年   2篇
  1967年   3篇
排序方式: 共有2217条查询结果,搜索用时 78 毫秒
81.
A randomized study was performed for the comparison of two copper-releasing intrauterine contraceptive devices (IUDs), the Nova-T and the Copper-T-200, simultaneously in Denmark, Finland, and Sweden. Five years' experience demonstrated that Nova-T users had a significantly lower pregnancy rate than Copper-T-200 users. The Pearl index over 5 years was 0.8 for Nova-T users and 2.0 for Copper-T users. The performance and tolerance of the Nova-T were less affected by parity and age than was the performance of the Copper-T. Infections were treated by removal of the device and with antibiotics. The cumulative rate of removals because of infections and suspected infections was below 5 with both devices over 5 years. The copper wire in the Nova-T has a silver core which prevents corrosion-induced fragmentation of the wire. Hence, the effective lifetime of this device is more than 5 years. The results indicate that the Nova-T, which is easy to insert and remove and is associated with a low pregnancy rate and a low medical termination rate, is a real improvement over other IUDs.  相似文献   
82.
OBJECTIVE: Previous studies have shown that pregnancy may have unfavourable effects on oral health. The pH and buffer capacity (BC) of paraffin-stimulated saliva, for example, have been found to decrease towards late pregnancy. Salivary carbonic anhydrase VI (CA VI) probably protects the teeth by accelerating the neutralization of hydrogen ions in the enamel pellicle on dental surfaces. Since estrogens and androgens are known to regulate CA expression in some tissues, we studied here whether salivary CA VI concentration shows pregnancy-related changes. DESIGN: Paraffin-stimulated salivary samples were collected from nine pregnant women 1 month before delivery and about 2 months afterwards and assayed for salivary CA VI concentration, BC and flow rate. The enzyme concentration was determined using a specific time-resolved immunofluorometric assay. The control group consisted of 17 healthy non-pregnant women. RESULTS: The results indicated that salivary CA VI levels varied markedly among individuals, but no significant differences in mean concentrations were seen between the samples collected during late pregnancy and postpartum. BC values were lower during pregnancy, however. CONCLUSIONS: Our findings suggest that CA VI secretion is not significantly affected by the hormonal alterations associated with pregnancy, and confirm the earlier reports that CA VI is not involved in the regulation of actual salivary BC.  相似文献   
83.
Background/Purpose: Laparoscopic appendectomy is an accepted way of dealing with suspected uncomplicated appendicitis in children. The role of laparoscopy in complicated acute appendicitis is more controversial. The purpose of this trial was to compare laparoscopic appendectomy with open appendectomy in children with complicated appendicitis. Methods: A total of 102 children with suspected acute appendicitis were selected randomly to undergo either a laparoscopic or an open appendectomy. The outcomes of 25 children with complicated appendicitis, 13 in the laparoscopic group and 12 in the open appendectomy group, were analyzed. Children, their parents, and research nurses were blinded to which procedure had been performed and remained blinded until the control visit 7 days after the operation. All 25 children completed a 30-day follow-up. Results: There were no differences in terms of patients' age, sex, weight, height, and appendiceal histology between the 2 groups. All laparoscopic procedures were completed without conversion. The mean ([plusmn]SD) operating time was 63 ([plusmn]31) minutes in the laparoscopic group and 37 ([plusmn]18) minutes in the open appendectomy group (mean difference 26 minutes, 95% CI 5 to 47 minutes, P = .02). There were 2 major complications in the laparoscopic group in children with appendiceal masses. One child had an entero-cutaneous fistula of the residual appendiceal tip that needed open reoperation. Another child had a pelvic abscess that resolved with antibiotic treatment. Superficial wound infections were encountered in 2 patients in the open appendectomy group. Conclusions: Laparoscopic appendectomy is an alternative to open procedure in children with complicated appendicitis. Good surgical judgement is necessary in patients with an established appendiceal abscess. J Pediatr Surg 37:1317-1320.  相似文献   
84.
Several studies have revealed that undergraduate medical education does not adequately prepare students for their work as physicians. There have been attempts to solve this problem in curriculum reforms in medical faculties. In this article, Finnish physicians' opinions on their undergraduate medical education are analysed. In 1988, a postal questionnaire was mailed to 2632 physicians registered during 1977-86, and altogether 1745 questionnaires were returned (66.3%). A follow-up study was done in 1998, and a questionnaire was sent to 2529 physicians who graduated between 1987 and 1996; 1822 questionnaires were returned (73.1%). Half of the respondents considered undergraduate education to correspond well with the requisite diagnostic skills and hospital doctors' work in general. In older and more traditional medical faculties (Helsinki, Oulu and Turku) education in primary healthcare work was considered insufficient. Also, more than 80% of the respondents felt they received too little teaching in administrative work. They reported that both traditional and younger, community-oriented faculties (Kuopio and Tampere) had considerably improved their education, especially in primary healthcare, during the 10-year follow-up. However, there were still clear differences between the education in the respective types of faculty as evaluated by their graduates. There is still room for improvements in undergraduate medical education, the better to meet the real needs of practising physicians in different fields of health care.  相似文献   
85.
To study neural correlates of category-specific processing, we measured relative cerebral blood flow changes by PET (oxygen-15) in young healthy subjects while they produced exemplars of animals or artefacts to written subcategory prompts. In comparison to a baseline (word reading), production of animal names elicited increased rCBF in the right inferior temporal region. This fits to recent lesion data on semantic impairment with animals, as well as imaging data on object recognition and semantic retrieval. In our study, it may represent an involvement of visual imagery in generation of animal names. In contrast, production of artefact names elicited increased rCBF in frontoparietal regions previously related to attention and mental effort.  相似文献   
86.
OBJECTIVE: Atypical neuroleptics seem to be more beneficial than typical ones with respect to long-term neuropsychological functioning. Thus, most studies focus on the long-term effects of neuroleptics. We were interested in whether atypical neuroleptic treatment is also superior to typical drugs over relatively short periods of time. METHODS: We studied 20 schizophrenic patients [10 males, mean age 35.5 years, mean Brief Psychiatric Rating Scale (BPRS) score at entry 58.9] admitted to our hospital with acute psychotic exacerbation. Nine of them were treated with typical and 11 with atypical neuroleptics. In addition, 14 healthy drug-free subjects (6 males, mean age 31.2 years) were enrolled in the study and compared to the patients. As neuropsychological tools, a divided attention test, the Vienna reaction time test, the Benton visual retention test, digit span and a Multiple Choice Word Fluency Test (MWT-B) were used during the first week after admission, within the third week and before discharge (approximately 3 months). RESULTS: Patients scored significantly worse than healthy controls on nearly all tests (except Vienna reaction time). Clinical ratings [BPRS and Positive and Negative Symptom Scale for Schizophrenia (PANSS)] improved markedly (p < 0.01), without a significant difference between typical and atypical medication. Clinical improvement (PANSS total score) correlated with less mistakes on the Benton test (r = 0.762, p = 0.017) and an improvement on the divided attention task (r = 0.705, p = 0.034). Neuropsychological functioning (explicit memory, p < 0.01; divided attention, p < 0.05) moderately improved for both groups under treatment but without a significant difference between atypical and typical antipsychotic drugs. CONCLUSIONS: Over short periods of time (3 months), neuropsychological disturbances in schizophrenia seem to be moderately responsive to both typical and atypical neuroleptics.  相似文献   
87.
PURPOSE: To report the long-term outcome of patients with lifestyle-limiting claudication after percutaneous transluminal angioplasty (PTA) of the femoropopliteal arteries. MATERIALS AND METHODS: Between 1989 and 1992, 173 consecutive claudicant patients (mean age, 65 years; age range, 41-90 years) underwent PTA in 218 limbs; all interventions included femoral and/or popliteal arterial segments, and additional iliac (n = 27) and infrapopliteal (n = 11) arterial lesions were also treated. Patients were followed up for 7-10 years. Altogether, 37 (17%) limbs were classified as Fontaine class 2A, and 181 (83%) were class 2B. Average length of the primary lesion was 5.2 cm. Reinterventions were analyzed. Patency rates and patient survival were assessed by means of life table analysis. Cox-Mantel tests and Cox proportional hazards models were used to define associated independent determinants. Development of chronic critical ischemia (CCI) and its determinants was assessed by using the Pearson chi(2) test and multiple logistic regression analysis. RESULTS: The primary and secondary patencies (+/- standard error of the estimate), respectively, were 46% +/- 3 and 63% +/- 3 at 1 year, 25% +/- 3 and 41% +/- 4 at 5 years, and 14% +/- 3 and 22% +/- 4 at 10 years. One-third (71 of 218) of the limbs required repeat interventions, including surgical revascularization in 35 limbs. Fourteen (6.4%) limbs developed CCI, resulting in a 0.8% incidence per year. In multivariate analysis, poor postinterventional peripheral runoff was an indicator of increased risk of CCI development (P =.03). CONCLUSION: Although the long-term patency rates of PTA of the femoropopliteal arteries in claudicant patients were poor, the acceptable number of reinterventions and the low frequency of development of CCI imply the long-term benefits achievable with this treatment.  相似文献   
88.
BACKGROUND: Epidural analgesia provides outstanding pain relief after surgery, but it is also associated with numerous adverse effects. In order to improve postoperative pain management in children we determined whether the use of epinephrine added to epidural sufentanil-ropivacaine infusion reduced drug requirements, the intensity and duration of postoperative pain and the incidence and severity of adverse effects. METHODS: A prospective, randomized, double blind, parallel group study design was used in 61 children. The children were given continuous epidural sufentanil-ropivacaine infusion either with (n=32) or without (n=29) epinephrine for postoperative analgesia. Intravenous ketoprofen, a non-steroid anti-inflammatory drug, was used for all children, and epidural ropivacaine was used for rescue analgesia. The drug consumption, intensity of pain at rest and during activity, and all adverse effects were recorded. RESULTS: : The need for sufentanil (P=0.001) and ropivacaine (P=0.006) was significantly lower in the with-epinephrine group than in the without-epinephrine group. The mean duration of epidural infusion (62 h) was similar in both groups. Four children in the without-epinephrine group were noticed to have a low oxygen saturation (SpO2<90%), and in one child a low respiratory rate (8 breaths min-1). The incidence of pruritus was higher in the without-epinephrine group (P=0.026). CONCLUSION: Both infusions provided effective pain relief, and epinephrine as an adjuvant to continuous epidural sufentanil-ropivacaine infusion seems to be useful in children.  相似文献   
89.
Sixteen patients with dislocated ankle fractures fixed between 1988 and 1991 with self-reinforced poly(L-lactide; SR-PLLA) screws and/or rods were followed up after 8.6 to 11.7 years (mean 9.6 years) at the Department of Orthopaedics and Traumatology, Helsinki University Central Hospital. In all patients accurate reduction of the fractures was retained and uneventful bony union was achieved. Good or excellent long-term functional results were observed in 15 out of 16 patients. One patient had post-traumatic osteoarthritis. In 5 patients, a late tissue reaction was observed over an extruding screw head with mild symptoms, which led to removal of small palpable masses. There were two superficial wound infections, one after a primary operation and one caused by a late tissue reaction after an operation. The correct operative technique, where all extruding extraosseous SR-PLLA material should be removed during the primary operation, should be followed.  相似文献   
90.
Eosinophils are considered essential in the pathogenesis of allergy. Reduced eosinophil apoptosis is considered to be a key element in the formation of eosinophilia in allergic conditions. Antihistamines are widely used in the treatment of allergic disorders, but their effects on eosinophil apoptosis are poorly understood. The histamine H1-receptor antagonist, ketotifen, is available orally and as eye drops for the treatment of allergic symptoms. The aim of our study was to investigate the possible effect of ketotifen on constitutive eosinophil apoptosis and on interleukin (IL)-5-mediated eosinophil survival. Isolated peripheral blood eosinophils were cultured with or without the survival-prolonging cytokine IL-5 and ketotifen. Apoptosis was assessed by measuring the relative DNA content and by morphological analysis. Ketotifen was found to reverse eosinophil survival induced by interleukin-5. However, the flow cytometry histogram of DNA in propidium iodide-stained cells was not typical to apoptosis. Morphological analysis of the eosinophils by bright-field microscopy suggested that the effect of ketotifen was due to the induction of primary necrosis rather than apoptosis. Histological assessment of eosinophil ultrastructure by transmission electron microscopy confirmed signs of advanced necrosis. In summary, our results suggest that at clinically relevant drug concentrations, ketotifen induces primary necrosis in IL-5-treated human eosinophils.  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