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   30813篇
  免费   2076篇
  国内免费   427篇
耳鼻咽喉   453篇
儿科学   524篇
妇产科学   636篇
基础医学   4148篇
口腔科学   757篇
临床医学   2749篇
内科学   5465篇
皮肤病学   633篇
神经病学   2075篇
特种医学   1747篇
外科学   4654篇
综合类   1306篇
现状与发展   2篇
一般理论   10篇
预防医学   1624篇
眼科学   679篇
药学   2758篇
  3篇
中国医学   605篇
肿瘤学   2488篇
  2023年   196篇
  2022年   490篇
  2021年   874篇
  2020年   508篇
  2019年   730篇
  2018年   774篇
  2017年   678篇
  2016年   759篇
  2015年   1145篇
  2014年   1431篇
  2013年   1617篇
  2012年   2456篇
  2011年   2452篇
  2010年   1650篇
  2009年   1513篇
  2008年   1931篇
  2007年   1844篇
  2006年   1732篇
  2005年   1569篇
  2004年   1388篇
  2003年   1173篇
  2002年   1030篇
  2001年   845篇
  2000年   843篇
  1999年   622篇
  1998年   229篇
  1997年   212篇
  1996年   187篇
  1995年   156篇
  1994年   141篇
  1993年   112篇
  1992年   248篇
  1991年   185篇
  1990年   179篇
  1989年   168篇
  1988年   150篇
  1987年   107篇
  1986年   99篇
  1985年   75篇
  1984年   87篇
  1983年   52篇
  1982年   56篇
  1981年   49篇
  1980年   46篇
  1979年   56篇
  1978年   45篇
  1977年   50篇
  1972年   45篇
  1971年   43篇
  1970年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
腹部术后胃瘫综合征的诊治体会   总被引:4,自引:3,他引:1  
目的探讨腹部术后胃瘫的诊断及治疗.方法总结16例腹部术后胃瘫患者的临床资料进行回顾性分析.结果该组病例中男11例,女5例;年龄36~85岁,平均(60.50±15.76)岁.术前长期流出道梗阻、恶性肿瘤、胆道疾病、胰十二指肠切除术后,胃大部切除术后的病人发病率高.胃镜、X线口服造影及核素胃排空试验对术后胃瘫的诊断有价值,经保守治疗后胃肠动力一般在术后4周内恢复.结论该病是一种功能性疾病,一旦诊断成立,采取促动力药物在内的保守治疗是治疗的有效方法,不宜盲目手术.  相似文献   
32.
Here we report the finding of enzymatic activity that specifically cleaves DNA containing 8-hydroxyguanine (oh8Gua) residues in various mammalian cells. To detect this activity, we used a synthetic double-stranded DNA containing a single oh8Gua at a defined position as the substrate, and analyzed the products of enzymatic digestion by polyacrylamide gel electrophoresis. Two cleavage sites near the oh8Gua residue were detected with partially purified fractions from cow brain and rat liver, and also with preparations from all mammalian tissues examined. These results suggest that enzymatic activity for the removal of oh8Gua from DNA is widely distributed in mammalian cells.  相似文献   
33.
Reduction mammaplasty by central pedicle flap with short submammary scar   总被引:2,自引:0,他引:2  
Reduction mammaplasty was performed in 30 patients by combining the central pedicle flap method with the short submammary scar (3-S) technique to avoid the common drawbacks of currently popular dermoglandular procedures. Reduction was accomplished by using perforating vascular branches from the pectoralis major muscle and its fascia supplying the nipple and breast parenchyme instead of the subdermal plexus. The central vascular pedicle supplying the nipple-areola complex was preserved. Only the periphery of the breast parenchyme was resected circumferentially, with the exception of the inferolateral portion, so as not to injure the sensory nerve. The remaining breast parenchyme was preserved in an inverted cone shape. The nipple-areola complex was safely transposed with great freedom, and the amount of resection was accurately adjusted for symmetry. No cases of nipple-areola complex sensory change occurred postoperatively, and lactation is possible because of preservation of the lactiferous ducts. The length of postoperative scars was reduced by using the short submammary scar technique. We believe this combined method is ideal in patients requiring resections ranging from 200 to 600 g per breast with good skin elasticity and moderate degree of ptosis.Presented at the Sixth Asian Pacific Congress of the International Confederation for Plastic and Reconstructive Surgery, in Seoul, Korea, October 1993.  相似文献   
34.
Reports the case of a 60-year-old woman who underwent R2 total gastrectomy, and subsequent palliation of painful symptom recurrence via a membrane-covered metal stent. Received: 13 June 1996/Accepted: 31 July 1996  相似文献   
35.
36.
Although single-photon absorptiometry (SPA) has been the predominant tool used to assess bone mineral density (BMD) in the forearm, the development of dual-energy x-ray absorptiometry (DEXA) provides the benefits of greater source stability, reduced scanning time, and improved image resolution compared to SPA. In the present study we used the DEXA bone densitometer (Hologic, Inc., Waltham, MA) to (1) measure BMD in the one-third radius and ultradistal radius; (2) examine the reproducibility of these BMD measurements; and (3) compare the BMD at the one-third radius with SPA (SP2, Lunar Corp., Madison, WI). In 65 normal women (ages 22-74 years) we examined changes in the forearm DEXA BMD with age, revealing significant quadratic regression equations. The reproducibility of DEXA BMD (mean +/- SEM) in 7 normal subjects aged 22-50 years is 0.85 +/- 0.16% for the predominantly cortical one-third radius site and 0.97 +/- 0.15% for the more trabecular ultradistal site. The regression relationship between DEXA and SPA of the one-third radius in 26 subjects (ages 22-68 years) is DEXA BMD = 0.105 + 0.826 (SPA BMD); R = 0.97, R2 = 0.94, p less than 0.0001. Bone densitometry of the forearm using DEXA may be performed relatively rapidly, providing reproducibility and image resolution that are generally superior to those observed with SPA.  相似文献   
37.
Acquired cystic disease has been documented to complicate most forms of chronic renal damage; it has only infrequently been described in transplanted kidneys. Five patients with noncystic ESRD and chronically rejected transplants in which acquired cystic disease arose are reported. The diagnosis of acquired cystic disease was established in examination of transplant nephrectomies from four patients and a core biopsy from the fifth. The allografts were in place from 44 to 80 months; three patients were treated with hemodialysis before the diagnosis of acquired cystic disease, whereas two received peritoneal dialysis. Three of the four patients evaluated had cysts in the native kidneys. Although papillary hyperplasia of lining epithelium was evident in four specimens, only one kidney was the site of neoplasms in the form of multiple small tubular adenomas. No malignant neoplasms were noted in this study or in the few similar previous ones; however, it is possible that chronically rejected transplanted kidneys may harbor neoplasms with the same malignant potential as those in acquired cystic disease in native kidneys.  相似文献   
38.
Effects of posts on dentin stress distribution in pulpless teeth.   总被引:5,自引:0,他引:5  
A finite element analysis was carried out to study the roles of posts in reducing dentin stress in pulpless teeth. Two-dimensional plane strain models of the midlabiolingual section of a human maxillary central incisor were first analyzed. The results showed that the gold alloy post reduced maximal dentin stress by as much as 30%. However, the integrity of the dentin was compromised and the effects of the post were likely to be exaggerated in such models. In an effort to correct for these problems, plane stress models with side plates and axisymmetric models were analyzed. Posts were found to reduce maximal dentin stress by only 3% to 8% when the teeth were subjected to masticatory and traumatic loadings in these latter models. Although posts reduced maximal dentin stress by as much as 20% when the teeth were loaded vertically, teeth such as incisors and canines normally are not subjected to vertical loadings. Thus the reinforcement effects of posts seem to be doubtful in these teeth.  相似文献   
39.
We examine the relationship between ethnicity and income as determinants of mammography use over a span of four years as a means of assessing community intervention impacts. The sample consisted of 1,447 women older than 34 years, living in Hawaii, who participated in the Behavioral Risk Factor Surveillance System (BRFSS). The percentage of women in the sample reporting a screening mammogram within the past two years was 31.4% in 1987, 54.1% in 1989, and 51.6% in 1990. Women of Hawaiian ancestry had the lowest percentage of mammogram use in the past two years (38.7%), while Japanese women had the highest percentage (49.8%). Results of logistic regression analysis indicate a significant increase in mammography use from 1987 to 1989 and no difference from 1989 to 1990. Findings also showed an association between age, income, and ethnicity with use in the past two years. Greater age, higher income, and Japanese origin, compared to Hawaiian, were all independently associated with increased odds of having had a mammogram in the past two years. We discuss results in terms of program evaluation and future research implications for community health surveys.  相似文献   
40.
The present study is a quantitative analysis of the unmyelinated fiber population in the fasciculus gracilis of the second cervical segment of cat and monkey. We find that unmyelinated fibers represent 13.7% of the total fiber population in this pathway in the cat and 18.9% in the monkey (Macaca fascicularis). The existence of such large numbers of these axons suggests that there may be a sizeable ascending fine primary afferent pathway in the fasciculus gracilis in cat and monkey whose destination is presumably the dorsal column nuclei. These findings are of interest in regard to classic ideas that the afferent fibers in the dorsal columns are large myelinated fibers that convey fine discriminative information to the dorsal column nuclei.  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