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   11068篇
  免费   942篇
  国内免费   27篇
耳鼻咽喉   88篇
儿科学   370篇
妇产科学   177篇
基础医学   1696篇
口腔科学   337篇
临床医学   1208篇
内科学   2009篇
皮肤病学   230篇
神经病学   794篇
特种医学   394篇
外科学   1513篇
综合类   252篇
一般理论   4篇
预防医学   1031篇
眼科学   199篇
药学   664篇
中国医学   17篇
肿瘤学   1054篇
  2021年   152篇
  2020年   111篇
  2019年   143篇
  2018年   168篇
  2017年   139篇
  2016年   153篇
  2015年   167篇
  2014年   216篇
  2013年   398篇
  2012年   496篇
  2011年   537篇
  2010年   306篇
  2009年   283篇
  2008年   441篇
  2007年   526篇
  2006年   493篇
  2005年   462篇
  2004年   473篇
  2003年   426篇
  2002年   396篇
  2001年   303篇
  2000年   344篇
  1999年   297篇
  1998年   138篇
  1997年   130篇
  1996年   101篇
  1995年   108篇
  1994年   87篇
  1993年   103篇
  1992年   281篇
  1991年   261篇
  1990年   214篇
  1989年   232篇
  1988年   170篇
  1987年   204篇
  1986年   195篇
  1985年   211篇
  1984年   135篇
  1983年   136篇
  1982年   104篇
  1981年   87篇
  1980年   89篇
  1979年   135篇
  1978年   92篇
  1977年   95篇
  1976年   102篇
  1974年   90篇
  1973年   96篇
  1972年   96篇
  1971年   93篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Differential screening-selected gene aberrative in neuroblastoma (DAN) is a member of a cystine knot protein family that includes Cerberus and Gremlin. First isolated in a screen to identify genes down-regulated in transformed rat fibroblasts, DAN has subsequently been cloned in Xenopus, mouse, and human. Overexpression of DAN suppresses the transformed phenotype and retards the cell's entry into S phase. Biochemical analyses have demonstrated DAN's ability to bind bone morphogenetic proteins and antagonize their signaling activity. In this study, chick DAN was cloned and sequenced, revealing a conserved cystine knot region as well as an N-glycosylation site. A riboprobe was designed from the 3' chick DAN coding sequence and used for analysis of DAN in the developing chick embryo by in situ hybridization. Chick DAN was expressed beginning at stage 10 in the developing somites and the medial otic epithelium. Expression in the neural layer of the eye became apparent at stage 14. By stage 17, expression had expanded to the base of the hindbrain. Limb bud labeling began at stage 20, whereas expression in the branchial arches appeared at stage 25. Chick DAN expression generally corresponded to that of mouse DAN expression as shown by comparative in situ hybridization. However, chick DAN was found in the otic epithelium and notochord, whereas mouse DAN was restricted to the overlying otic ectomesenchyme and was absent from the notochord. This observation suggests that DAN may play different roles in chick and mouse otic and notochord development.  相似文献   
32.
OBJECTIVE: Exercise advice is the main treatment for symptom relief in the UK for patients with mild to moderate Intermittent Claudication (IC). Would a weekly exercise and motivation class for 6 months offer adjuvant benefit over written and verbal exercise advice alone? PATIENTS AND METHODS: Fifty-nine patients attending a regional vascular centre for whom IC was the main factor affecting mobility were randomised to either exercise advice alone (n=30) or exercise advice with a once a week 45 min supervised exercise/motivation class (n=29). The mean age was 68 years. Baseline and 6-month assessment included a Quality of Life Questionnaire--the Short-Form-36, the Charing Cross Symptom Specific Claudication Questionnaire (CCCQ) and treadmill walking distance (3.5 km/h 12%). RESULTS: At 6-month follow-up the supervised exercise group had improved their treadmill walking by 129% compared to 69% in the advice alone group (p=0.001). This significant improvement was maintained at the subsequent 9 and 12-month follow-up assessments. By the 9-month stage the advice only group CCCQ score had improved 16% from baseline, while the supervised exercise group had a significantly better 43% improvement in base line score (p<0.05). Self reported frequency of walks was higher in the exercise class group being significant for improvement in CCCQ score. CONCLUSION: A weekly, supervised exercise and motivation class for a 6-month period provides a significant improvement in patients' symptoms, quality of life, and distance walked compared with advice alone and this improvement continues after attendance at class has ceased.  相似文献   
33.
A case of pulmonary infection caused by Trichosporon beigelii is reported. The infection occurred in a neutropenic patient with acute lymphoblastic leukemia. His chest radiograph showed a 6-cm pulmonary infiltrate in the right midzone and an apical infiltrate on the left. Repeated cultures of bronchoalveolar lavage grew budding yeast that was identified as T beigelii on the basis of morphological, cultural, and biochemical characteristics. He responded to amphotericin-B therapy. Systemic infections caused by this yeast are rare and its causal relationship in localized lung disease has been reported only seven times previously.  相似文献   
34.
This paper presents the results of recent ethnomycological exploration in southern Thailand. Field observations, interviews and collection of fungi specimens were carried out primarily on two islands, Koh Samui and Koh Pha-ngan, situated in the western region of the Gulf of Siam. Some fieldwork was also conducted in the northern Thai province of Chiang Dao and in the southern Thai province of Surat Thani. During five separate excursions (1989-90), observations were made of occurrence, harvesting, use, and marketing of psychoactive fungi by local Thai natives (males and females, adults and children), foreign tourists, and German immigrants. The first records of psychoactive Psilocybe subcubensis and Copelandia dung fungi in Thailand are presented in this paper. These fungi exhibited intense bluing reactions when handled, indicating the presence of psilocybin and/or psilocin. Seven collections of Psilocybe cubensis (Earle) Singer and/or Psilocybe subcubensis Guzman and four collections of Copelandia sp. were harvested and sun-dried for herbarium deposit. These fungi are cultivated or occur spontaneously, often appearing in the decomposed manure of domesticated water buffalo (Bubalus bubalis) and at least three different species of cattle (Bos indicus, B. guarus, and B. sundaicus). The psychoactive fungi are cultivated in clandestine plots, both indoors and outdoors, in the uplands and villages on Koh Samui by both Thai natives and some foreigners. The sale of psychoactive fungi directly to tourists and to resort restaurants for use in edible food items such as omelettes and soups is discussed in detail. The preparation and sale of mushroom omelettes adulterated with artificial hallucinogens in some restaurants is also discussed. In addition, the marketing of items such as hand painted T-shirts, post cards, and posters bearing mushroom related motifs in Thailand is described.  相似文献   
35.
36.
37.
One of the most common errors in model surgery for orthognathic surgery is in the mounting of the models on the articulator. This study assessed the ability of one type of face-bow to transfer the maxillary model to the articulator. Twenty-five consecutive mountings were evaluated by calculating the angle made between the maxillary occlusal plane on the cephalogram and comparing it with the maxillary occlusal plane angle on the articulator. An accurate face-bow transfer should transfer this angle, making the two similar. It was found that a significant difference between the maxillary occlusal plane angle on the cephalogram and the articulator was found in the average case. The implications of such errors and a technique to avoid them are presented.  相似文献   
38.
It was proposed that differences between paranoid and nonparanoid schizophrenics in the processing of affective information may reflect underlying differences in their schema for emotion-laden information. Performances of 14 paranoid schizophrenics, 13 nonparanoid schizophrenics, and 15 matched controls were compared on a facial affect judgment task, and a matched control task comprising geometric figures largely devoid of emotional information. Subjects were required to rate friendliness, select an emotion label, and subsequently to remember the stimuli. Nonparanoids were deficient in overall labeling of facial affect, suggesting a weak cognitive schema for emotional information. The paranoids were particularly more accurate than the nonparanoids at labeling the negative facial affects, suggesting well-developed negative emotional aspects in their cognitive schema. Unexpectedly, nonparanoids relative to paranoids displayed a greater memory deficit in the recognition of geometric figures than in the recognition of faces. The nonparanoid deficit suggests these subjects may have poorly organized schema for remembering less structured nonverbal information. The findings support the idea of fundamental cognitive processing differences between paranoid and nonparanoid schizophrenia.  相似文献   
39.
40.
Hospitalized neonates are commonly colonized soon after birth with Staphylococcus aureus. The majority of neonates do not develop infectious sequelae; however, premature neonates appear to be more susceptible to serious infections, such as pneumonia. We report a case of an extremely low birth weight infant who developed necrotizing pneumonia due to methicillin-resistant Staphylococcal aureus (MRSA). The MRSA isolate from this neonate is identical to the strains that have been causing primarily community-associated skin and soft tissue infections. The severe course of this patient may be attributed to the presence of the Panton-Valentine leukocidin gene, a well-known virulence factor leading to soft tissue and pulmonary infections.  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