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   65441篇
  免费   3219篇
  国内免费   175篇
耳鼻咽喉   816篇
儿科学   2008篇
妇产科学   1480篇
基础医学   9386篇
口腔科学   1126篇
临床医学   5529篇
内科学   14125篇
皮肤病学   1365篇
神经病学   5861篇
特种医学   2186篇
外国民族医学   32篇
外科学   8622篇
综合类   191篇
一般理论   13篇
预防医学   5707篇
眼科学   1261篇
药学   4517篇
中国医学   153篇
肿瘤学   4457篇
  2023年   364篇
  2022年   360篇
  2021年   982篇
  2020年   622篇
  2019年   1007篇
  2018年   1694篇
  2017年   1281篇
  2016年   1348篇
  2015年   1571篇
  2014年   1681篇
  2013年   2578篇
  2012年   4053篇
  2011年   4170篇
  2010年   2128篇
  2009年   1697篇
  2008年   3523篇
  2007年   3803篇
  2006年   3484篇
  2005年   3585篇
  2004年   3506篇
  2003年   3238篇
  2002年   3144篇
  2001年   1707篇
  2000年   1803篇
  1999年   1483篇
  1998年   427篇
  1997年   341篇
  1996年   331篇
  1995年   286篇
  1992年   869篇
  1991年   790篇
  1990年   812篇
  1989年   781篇
  1988年   719篇
  1987年   683篇
  1986年   678篇
  1985年   634篇
  1984年   474篇
  1983年   394篇
  1982年   245篇
  1979年   402篇
  1978年   253篇
  1974年   317篇
  1973年   300篇
  1972年   319篇
  1971年   286篇
  1970年   252篇
  1969年   318篇
  1968年   276篇
  1967年   254篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Differences in exercise-induced muscle damage between males and females were studied in an animal model by measuring the serum activities of specific muscle enzymes (creatine kinase and aspartate aminotransferase). It was found that rats showed muscle damage, comparable to that observed in humans after long-term exercise: males were much more affected than females. For example, the CK activity in male rats immediately after exercise was 335% of the resting value, but remained unchanged in females. To test the hypothesis that oestrogens may protect the female muscle membrane, female rats were ovariectomized at different stages of sexual maturity and exercised. A clear effect of this hormonal manipulation was observed: operated animals showed post-exercise CK elevations, depending of the age at the time of ovariectomy. Rats, ovariectomized before reaching sexual maturity, showed more damage than those ovariectomized after reaching sexual maturity.  相似文献   
82.
83.
PURPOSE: In France, legislation mandates that the clinical diagnosis of brain death be confirmed by one paraclinical test before organ donation is allowed. That test may be either the electroencephalogram (EEG) or cerebral angiography. We report a case in which the clinical diagnosis of brain death was first confirmed by two EEGs performed according to the French guidelines, but ruled out by cerebral angiography. Considering that the EEG is no longer recommended to establish the diagnosis of brain death, we discuss the relevance of maintaining the EEG for brain death diagnosis in France. CLINICAL FINDINGS: A 58 yr-old man was admitted to the intensive care unit because of coma secondary to a massive subarachnoid hemorrhage with herniation below the falx shown by computed tomography. Clinical criteria of brain death were rapidly present. Two EEGs first confirmed the diagnosis but a four-vessel cerebral angiography was finally performed because the patient moved spontaneously. This cerebral angiography showed flow in the right internal carotid artery. A computed tomography performed the next day definitely confirmed the absence of brain death and organ donation did not occur. CONCLUSIONS: This case demonstrates the limitations of the EEG for this indication and suggests that angiography should be preferred. French legislation is probably maladjusted and would benefit by incorporating guidelines of other countries like Canada. International harmonization of criteria for brain death diagnosis would also be welcome.  相似文献   
84.
Abnormal intragastric distribution of food (IDF) and a phasic contractility in the proximal stomach have been related to dyspeptic symptoms. Thus, the behaviour of the stomach and the proximal region, in particular, continues to attract attention and demand for reliable and comfortable techniques. The aims of this study were to employ AC Biosusceptometry (ACB) and scintigraphy to evaluate IDF and gastric motor activity in humans. Fifteen healthy volunteers ingested 60 mL of yogurt containing 2 mCi of 99mTc and 4 g of ferrite. Each volunteer had gastric motility and IDF evaluated twice on separate days; on one occasion by ACB and another by scintigraphy. Digital signal processing was performed in MatLab (Mathworks Inc., Natick, MA, USA). Results were expressed as mean +/- SD. Similar results of distal accumulation time (P < 0.001) were obtained for scintigraphy (6.93 +/- 3.25 min) and for ACB (7.04 +/- 3.65 min). Fast Fourier Transform revealed two dominant frequencies (P > 0.9). Besides the well-know frequency of 3 cpm, our results showed identical frequencies in proximal stomach recordings (P < 0.001) for scintigraphic (1.01 +/- 0.01 cpm) and ACB (0.98 +/- 0.06 cpm). In summary, our data showed that scintigraphy and ACB are promising techniques to evaluate several aspects of gastric motility. Moreover, ACB is non-invasive, radiation-free and deserves the same importance as conventional methods for this kind of analysis.  相似文献   
85.
Introduction Vertebral deformities are a common consequence of osteoporosis and are known to decrease quality of life. The Qualeffo–41 is a quality-of-life questionnaire especially developed for measuring quality of life in patients with vertebral deformities. It consists of 41 questions arranged in five domains: pain, physical function, social function, general health perception, and mental function. The objectives of this study were: (1) to develop a shorter version of the Qualeffo–41 by removing redundant questions; and (2) to investigate the scale characteristics, reliability, and validity of this shorter version. Methods The study was performed using data from the Qualeffo validation study and the Multiple Outcomes of Raloxifene Evaluation (MORE) study. The analyses were performed in patients with vertebral deformities (n=579). Factor analysis on polychoric correlations and an item response theory (IRT) model, i.e., the generalized partial credit model (GPCM), were used to create a shorter version of Qualeffo–41. Using GPCM, scoring weights were computed for all items. Results Three items were removed from the data set because of too many missing values. Factor analysis identified three instead of five domains: (1) pain, (2) physical function, and (3) mental function. Five items had factor loadings <0.4 and were not included in the GPCM. After excluding several items, the domains pain (four items), physical function (18 items), and mental function (nine items) showed a good, reasonable, and excellent fit, respectively. This indicates that the mental function domain and the pain domain are more unidimensional than the physical function domain. All three domains showed a very high correlation (r ≥0.95) with the corresponding domains of the Qualeffo–41. Conclusions Qualeffo–31 was developed, consisting of three domains with a reasonable to excellent fit to the GPCM. Although the fit to the GPCM supports the construct validity of the Qualeffo–31, validation in a new study should be performed before using it in practice.  相似文献   
86.
Gallbladder sludge and acute pancreatitis induced by acute hepatitis A.   总被引:1,自引:0,他引:1  
In this case report, a young woman with gallbladder sludge and acute pancreatitis due to acute hepatitis A (HAV) is presented. She was admitted to our hospital with abnormal hepatic enzymes. Five days prior to her admission, an initial abdominal ultrasound was performed at another hospital and revealed no abnormality, while her serum aspartate aminotransferase (AST) level was at the upper limit of normal (ULN) x 8. A second ultrasound was performed at our hospital and revealed a gallbladder wall thickness (9.3 mm), gallbladder sludge in the gallbladder lumen, pancreatic edema, ascites, and hepatomegaly while AST was at the ULN x 50. Magnetic resonance imaging and magnetic resonance cholangiopancreatography revealed imaging features of an acute stage of pancreatitis and gallbladder wall thickness with coexisting sludge in the gallbladder lumen. HAV infection was diagnosed by the detection of immunoglobulin M against HAV in the serum. The patient underwent two repeated abdominal ultrasound examinations on the 5th (AST was at the ULN x 3) and the 20th days (AST was at the normal) after her discharge, and both revealed normal findings. In our case, we observed reversible changes in the hepatobiliary and pancreatic system which was related to the severity of hepatic necro-inflammation. HAV-associated pancreatitis may be due to the formation of biliary sludge during the acute phase of the viral illness, but this association needs further investigation.  相似文献   
87.
Abstract: Background: The laryngeal mask airway (LMA) can be used in general anaesthesia without neuromuscular block. The laryngeal tube (LT) is a new airway device with similar airway features as LMA. LT is provided with a distal cuff to prevent regurgitation. In this study we compared the LMA and LT concerning patient and user aspects. Methods: Sixty patients with ASA (American Society of Anestesiologists) score 1–2 scheduled for minor surgery were randomized to be ventilated either through LMA or LT. After insertion, the number of insertion attempts, and “positioning” and “airway-assessment” was evaluated. The patients reported on “sore throat” after 30 and 60 minutes and the day after anaesthesia. Results: Gender and mean age were equal in both groups. The first insertion attempt was successful in 25 of 28 patients randomised to LMA and in 23 of 27 patients randomised to LT. LMA was evaluated to be easier in “positioning” whereas no difference in “sore throat” was reported. Conclusion: We found no difference between the LMA and the LT in terms user and patient friendliness and safety.  相似文献   
88.
Objects Genetic syndromes associated with ependymoma are uncommon, with the exception of NF2. We describe two cases of ependymoma presenting with Klinefelter’s Syndrome (KS) as co-morbid condition. Materials and methods The first patient was diagnosed for KS during pregnancy; he also presented a thyroid agenesis and a deficit of methyltetrahydrofolate reductase (MTHFR); at 30 months of age he was operated on for a grade II ependymoma of IV ventricle; after a multiple-stage surgery, he underwent oral chemotherapy and stereotactic radiotherapy, but after 15 months he presented a local recurrence and died. The second patient was diagnosed for KS at the age of 16 months; at 10 years of age, due to back pain, he underwent an MRI, which showed a cauda equine tumor. He underwent surgery and radiotherapy. Histology was of mixopapillary ependymoma. Conclusion In a review of literature, various neoplasms have been described in association with KS. To our knowledge, these are the first two cases reported of ependymoma associated to KS. A retrospective study of 44 monoinstitutional ependymoma cases demonstrated association with genetic syndromes in 22%.  相似文献   
89.
Females are disproportionately affected by constipation, which is often aggravated during pregnancy. Bowel function also changes during the luteal phase of the menstrual cycle. The aim was to compare the effects of acute administration of female sex steroids on gastric emptying, small bowel transit and colonic transit in healthy postmenopausal subjects. A second aim was to determine whether withdrawal of the hormones was associated with a change in transit. Forty-nine postmenopausal females were randomized to receive for 7 days 400 mg day(-1) micronized progesterone, 0.2 mg day(-1) oestradiol, combination of the two, or placebo. Treatment groups were balanced on age. Participants underwent whole gut transit measurement by scintigraphy using a 99m-labeled technetium-egg meal and 111-labeled indium-charcoal via a delayed-release capsule. Transit measurement was repeated after withdrawal of the study medications. The primary endpoints were ascending colon (AC) emptying half-life time (t1/2) and colonic geometric centre (GC) at 24 h. Secondary analysis variables were GC at 4 and 48 h, gastric emptying t1/2 and colonic filling at 6 h. There was a significant overall effect of progesterone on colonic transit with shorter AC emptying t1/2 and significantly greater colonic GC at 48 h. No transit endpoints were altered by oestradiol or combined hormonal treatment relative to placebo. Oestradiol and progesterone resulted in looser stool consistency. Withdrawal of the hormone supplement was not associated with significant alteration in transit. Micronized progesterone does not retard colonic transit in postmenopausal females.  相似文献   
90.
Cytogenetic abnormalities are rarely found in patients with juvenile chronic myelogenous leukemia (JCML). In patients with chromosomal abnormalities, chromosomes 7 and 8 are usually involved. A case of JCML with 47 XXX and a 46 XX karyotype is described and the literature is reviewed. To our knowledge, this is the first case ever to have been reported.  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