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   6022篇
  免费   505篇
  国内免费   12篇
耳鼻咽喉   45篇
儿科学   212篇
妇产科学   189篇
基础医学   794篇
口腔科学   101篇
临床医学   602篇
内科学   1408篇
皮肤病学   54篇
神经病学   493篇
特种医学   220篇
外国民族医学   1篇
外科学   938篇
综合类   100篇
一般理论   1篇
预防医学   475篇
眼科学   102篇
药学   313篇
中国医学   13篇
肿瘤学   478篇
  2021年   69篇
  2020年   41篇
  2019年   67篇
  2018年   91篇
  2017年   66篇
  2016年   80篇
  2015年   107篇
  2014年   118篇
  2013年   169篇
  2012年   275篇
  2011年   268篇
  2010年   163篇
  2009年   164篇
  2008年   254篇
  2007年   243篇
  2006年   259篇
  2005年   264篇
  2004年   250篇
  2003年   205篇
  2002年   224篇
  2001年   215篇
  2000年   179篇
  1999年   165篇
  1998年   72篇
  1997年   51篇
  1996年   61篇
  1995年   67篇
  1994年   55篇
  1992年   169篇
  1991年   163篇
  1990年   132篇
  1989年   142篇
  1988年   126篇
  1987年   149篇
  1986年   115篇
  1985年   110篇
  1984年   98篇
  1983年   74篇
  1982年   54篇
  1981年   42篇
  1979年   64篇
  1978年   55篇
  1977年   42篇
  1976年   50篇
  1975年   53篇
  1974年   59篇
  1973年   48篇
  1972年   41篇
  1971年   41篇
  1969年   41篇
排序方式: 共有6539条查询结果,搜索用时 15 毫秒
991.
D Moore  S Lichtman  J Lentz  D Stringer    P Sherman 《Gut》1986,27(10):1219-1222
Eosinophilic gastroenteritis most commonly involves the stomach and proximal small intestine with eosinophilic inflammation of either the mucosa, submucosa or serosa. The patient reported here had isolated eosinophilic colitis. The initial presentation with iron deficiency anaemia owing to occult gastrointestinal blood loss emphasises the need to evaluate the entire gastrointestinal tract in patients with eosinophilic gastroenteritis.  相似文献   
992.
Sixteen cine magnetic resonance imaging (MRI) studies were performed in 14 patients aged 1 week to 17 years (mean age, 46 months), who had coarctation of the aorta confirmed at angiography or surgery. Conventional echocardiographic-gated MRI was first performed in axial and rotated sagittal views and was used to identify the slice locations for cine MRI. Cine MRI was performed by gradient-recalled acquisition in steady state with a 30 degree flip angle, 12-msec echo time, 22-msec pulse repetition time, and a 128 x 256 acquisition matrix. Coarctation anatomy was extremely well defined in all but one patient who had vascular clips at the coarctation repair site. The smallest descending aortic flow diameter on cine MRI showed excellent agreement with angiography (r = 0.90). Lucent jets of high-velocity flow through the site of coarctation were imaged in eight patients, and jet length correlated well with the angiographic severity of coarctation (r = -0.81). Two patients were restudied after surgery, and they exhibited excellent repair and normal flow patterns. Cine MRI provides high-resolution imaging of coarctation anatomy with a dynamic spatial and temporal visualization of flow and with excellent detail of vascular anatomy and flow both proximal and distal to the coarctation.  相似文献   
993.
Summary An unusual case of a woman with primary biliary cirrhosis and cutaneous sarcoidosis is described. The factors that allow a specific diagnosis of each condition are presented and the literature pertaining to such complex and unusual cases is presented.This work was supported in part by a grant from the Gastroenterology Medical Research Foundation of Southwestern Pennsylvania.  相似文献   
994.
Because there is mounting evidence that localized intravascular coagulation may contribute to tissue injury following a variety of immunologic events, including immune complex diseases, fibrinogen catabolism was studied in patients with systemic lupus erythematosus to determine factors correlating with accelerated coagulation. 125I-fibrinogen half-life in controls was 90.1+/- 11 hours and the mean SLE half-life was 60.5 +/- 12. SLE patients in complete clinical remission had normal half-lives, but patients with symptomatic clinical disease, including renal disease, had significantly reduced fibrinogen survival. Accelerated fibrinogen consumption also correlated with positive tests for anti-DNA antibodies, but not with hypocomplementemia. These observations support the hypothesis that the coagulation system is activated in patients with immune complex diseases. Further studies are required to define the role, if any, that coagulation may play in causing tissue injury.  相似文献   
995.
This study intends to document and evaluate the first compiled experience in the treatment of both cutaneous and deep vascular lesions using the Nd:YAG laser. Thirty-eight patients were treated over a 5-year period from 1979 to 1984 using the Nd:YAG laser with FDA approval. Lesions included capillary, cavernous, combined capillary-cavernous hemangiomas, portwine stains, arteriovenous malformations, lymphangiomas, multiple telangiectasias, and one case of Klippel-Trenaunay-Webber syndrome. The number of treatments per patient ranged from one to four. Partial or complete resolution of these various lesions, as evidenced by a decrease in size, and/or normalization of pathologic cutaneous changes was noted in a majority of patients. While both the argon and CO2 lasers have been well studied in the treatment of cutaneous vascular lesions, this is the first compiled series reporting results using the Nd:YAG for such problems. The Nd:YAG laser represents an alternative modality in the treatment of cutaneous hemangiomas and introduces an efficacious method in the treatment of cavernous vascular lesions.  相似文献   
996.
Primary rat hepatocytes were transfected with simian virus 40 DNA and cultured in a chemically defined medium. Proliferating colonies developed after 2-3 weeks. Three cell lines were established by cloning albumin-secreting colonies, as identified by an immunooverlay assay. Two of the cell lines, ALB-6 and ALB-8, expressed all five liver-specific mRNAs studied, albumin, alpha-1-antitrypsin, fibrinogen, alpha-1-acid glycoprotein, and histidase. ALB-6 cells were nontumorigenic in nude mice while ALB-8 cells were weakly tumorigenic with only one of four injected nude mice developing a slowly growing tumor. Further transfection of ALB-6 and ALB-8 cells with an activated c-Ha-ras or N-ras oncogene resulted in strongly tumorigenic cells. The tumors induced by ras-transformed ALB-6 cells were moderately differentiated hepatocellular carcinomas. The tumors derived from ras-transformed ALB-8 cells were poorly differentiated, while the slowly growing tumors induced by untransfected or control DNA-transfected ALB-8 cells were well-differentiated trabecular hepatocellular carcinomas, suggesting histological dedifferentiation of cells following ras transformation. However, the synthetic capabilities of the cells were not lost in that the ras-transfected cultures and the tumors induced by ras-transformed cells retained the ability to synthesize the five liver-specific mRNAs. Thus we have developed an in vitro model of carcinogenesis in which, by sequential exposure to SV40 DNA and a ras oncogene, primary rat hepatocytes are transformed.  相似文献   
997.
BACKGROUND: The authors conducted this study to determine if proximal caries diagnoses made using bitewing radiographic images printed on photographic paper were comparable with diagnoses made using traditional radiographic film images. METHODS: The authors digitized 15 posterior bitewing radiographs that contained 74 carious and 127 sound unrestored proximal surfaces and printed them on photographic paper. Fourteen dentists evaluated the radiographs and two printed image formats (4 x 3 centimeters and 8 x 6 cm) for evidence of caries. The diagnostic accuracy and interobserver agreement for caries diagnoses obtained in the two printed image formats were compared with those for radiographic film images. RESULTS: Overall, the diagnostic accuracy of printed images did not differ significantly from radiographic film images for dentinal caries. However, for caries limited to the enamel surface, a decrease in sensitivity was noted in six of the 14 observers for the smaller print images, while no significant differences in the diagnoses of enamel caries were observed among any of the observers in the enlarged print format. CONCLUSION: This study provides evidence that printed images can be used to diagnose dental caries reliably. CLINICAL IMPLICATIONS: The results of this study indicate that the diagnostic information obtained by viewing printed images is equivalent to that obtained by viewing standard radiographs. Size of the printed image also may be important in caries diagnosis and care must be taken to print bitewing radiographic images at a size that optimizes interpretation. Other factors that must be considered are the type of printer, printer resolution, paper quality and type of ink used. With careful consideration of printing parameters, clinicians can be assured of diagnostic quality in printed images.  相似文献   
998.
AIMS: To describe the course of reported musculoskeletal pain in the temporomandibular region and other signs and symptoms of temporomandibular disorders (TMD) as well as psychological distress over the course of pregnancy and 1 year postpartum. METHODS: Women with musculoskeletal orofacial pain (n = 19) and pain-free comparison subjects (n = 16) in the first trimester of pregnancy were selected through records review from the population of a large health maintenance organization. Subjects completed a self-administered questionnaire assessing pain, depression, and somatic symptoms; provided a sample of whole unstimulated saliva; and underwent a standardized clinical examination during the third, sixth, and ninth months of pregnancy and 1 year postpartum. RESULTS: At baseline (third month of pregnancy), 16 of the 19 patients with musculoskeletal orofacial pain met criteria for an RDC/TMD diagnosis. Reported musculoskeletal orofacial pain diminished significantly during the second or third trimester of pregnancy and increased again postpartum. Measures of mandibular opening increased over pregnancy in both cases and comparison subjects and remained high postpartum. Depression and somatic symptoms changed little over the course of pregnancy but were substantially lowered at 1 year postpartum for both groups. As expected, subjects with pain had higher levels of palpation pain, diminished mandibular range of motion, and higher levels of psychological distress compared to subjects without orofacial pain. CONCLUSION: Musculoskeletal orofacial pain and related symptoms appear to improve over the course of pregnancy. This improvement occurs in the presence of increased joint laxity and is not paralleled by improvements in psychological distress. Thus, it was concluded that the improvement in pain is most likely associated with the dramatic hormonal changes occurring during pregnancy.  相似文献   
999.
This study of 133 patients with localized prostate cancer (Stages A2 to C), treated by external beam radiation therapy (XRT), was undertaken for two reasons: (1) to investigate the usefulness of pretreatment serum prostate-specific antigen (PSA) levels in evaluating patients before XRT; and (2) to investigate post-XRT changes in PSA values and their likely clinical significance. It was found that pretreatment PSA values in patients with localized disease exhibit wide patient to patient variability with a greater than 100-fold difference between the lowest and highest values. Although mean PSA values were significantly higher in Stage C disease (51 patients; mean PSA, 17.3 ng/ml) than in Stage A2 disease (31 patients; mean PSA, 9.0 ng/ml), Stage B1 disease (23 patients; mean PSA, 9.1 ng/ml), or Stage B2 disease (28 patients; mean PSA, 10.6 ng/ml), individual values were of virtually no help in assigning individual patients to a clinical stage. PSA levels did not correlate with grade. After XRT, PSA values fell significantly and dramatically in virtually all patients (98%) by 3 months follow-up. Mean PSA fell from 12.5 to 2.6 ng/ml, and median PSA fell from 6.6 to 1.9 ng/ml. In most patients, PSA continued to fall up to 12 months after XRT and then stabilized at 21 months. Although PSA values fell dramatically after XRT, PSA was detectable in the serum of all patients. PSA values tended to transiently and mildly elevate during XRT. In a small proportion of patients, rising PSA values were observed after 6 months. The full significance of this requires further follow-up, of four such patients, one has relapsed. PSA is a more sensitive marker of prostatic radiation than prostatic acid phosphatase.  相似文献   
1000.
The influence of local control on metastatic dissemination was analyzed in 601 patients with clinically staged A2 to C prostate cancer treated by high-energy external beam radiation therapy who did not undergo hormonal manipulation before disease progression. Median follow-up for surviving patients was 7.7 years. Ninety-three patients had locally recurrent disease. The actuarial incidence of metastases in these patients (70% at 13 years) was significantly higher than in the 508 patients without local failure (40% at 13 years, P less than 0.001). High stage, high grade, prior transurethral resection, elevated acid phosphatase, disease fixation to the pelvic sidewall, and failure to perform a baseline bone scan correlated positively with the occurrence of metastases. However, except for a slight excess of Stage C, none of the metastatic predictors were more common in patients who failed locally than in those who did not. The Stage C preponderance does not account for the difference in incidence of metastases between the two groups, in as much as metastases were significantly more common in Stage C when disease recurred locally than when it did not. Thus, local control of prostate cancer does decrease the likelihood of metastatic disease. Moreover, patients with local control experienced a significantly better disease-specific survival than patients who failed locally.  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