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   2148428篇
  免费   148323篇
  国内免费   3984篇
耳鼻咽喉   31531篇
儿科学   68032篇
妇产科学   60462篇
基础医学   303318篇
口腔科学   63007篇
临床医学   188014篇
内科学   409944篇
皮肤病学   48803篇
神经病学   168438篇
特种医学   84366篇
外国民族医学   595篇
外科学   327511篇
综合类   48596篇
现状与发展   7篇
一般理论   678篇
预防医学   153300篇
眼科学   51414篇
药学   165787篇
  10篇
中国医学   5063篇
肿瘤学   121859篇
  2018年   20819篇
  2016年   18625篇
  2015年   20770篇
  2014年   28858篇
  2013年   43217篇
  2012年   57707篇
  2011年   61152篇
  2010年   36135篇
  2009年   34445篇
  2008年   57566篇
  2007年   62363篇
  2006年   63178篇
  2005年   60606篇
  2004年   58617篇
  2003年   56439篇
  2002年   55086篇
  2001年   104512篇
  2000年   107299篇
  1999年   90256篇
  1998年   24079篇
  1997年   21637篇
  1996年   21144篇
  1995年   19874篇
  1994年   18441篇
  1993年   17351篇
  1992年   69490篇
  1991年   67138篇
  1990年   65993篇
  1989年   64038篇
  1988年   59064篇
  1987年   57919篇
  1986年   55222篇
  1985年   52337篇
  1984年   38916篇
  1983年   33059篇
  1982年   19310篇
  1981年   17404篇
  1979年   36700篇
  1978年   25786篇
  1977年   22628篇
  1976年   20327篇
  1975年   23065篇
  1974年   27240篇
  1973年   26566篇
  1972年   25289篇
  1971年   23678篇
  1970年   22196篇
  1969年   21354篇
  1968年   19698篇
  1967年   17648篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
62.
63.
64.
65.
66.
BACKGROUND: Three dimensional skin equivalents are widely used in dermatopharmacological and toxicological studies and as autologous transplants in wound healing. In pharmacology, there is tremendous need for monitoring the response of engineered skin equivalents to external treatment. Transplantation of skin equivalents for wound healing requires careful verification of their quality prior to transplantation. Optical coherence tomography (OCT) is a non-contact, non-destructive imaging technique for living tissues offering the potential to fulfill these needs. This work presents an analysis of OCT for high-resolution monitoring of skin equivalents at different stages during the culture process. METHODS: We developed a high-resolution OCT imaging setup based on a commercially available OCT system. A broadband femtosecond laser light source replaces the original superluminescence diode. Tomograms of living skin equivalents were recorded with an axial resolution of 3 mum and correlated with histology and immunofluorescence images. Comparison with standard low-resolution OCT is presented to emphasize the advantages of high-resolution OCT for this application. RESULTS: OCT is particularly able to distinguish between different layers of skin equivalents including stratum corneum, epidermal and dermal layer as well as the basement membrane zone. The high-resolution OCT scans correlate closely with two key benchmarks, histology and immunofluorescence imaging. CONCLUSIONS: This study clearly demonstrates the benefits of high-resolution OCT for identifying living tissue structure and morphology. Compared with the current gold standard histology, OCT offers non-destructive tissue imaging, enabling high-resolution evaluation of living tissue morphology and structure as it evolves.  相似文献   
67.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  相似文献   
68.
69.
We report the case of a 38-year-old woman who presented with chronic lower abdominal pain. Her past medical history included a splenectomy due to abdominal trauma. Ultrasound examination revealed four pelvic tumors which, upon laparotomy, were found to be the result of splenosis. Approximately 100 cases of splenosis have been reported but only a minority of them have been published in the gynecological literature. Our case indicates that those involved in pelvic scanning (even of asymptomatic women) and/or treating those complaining of lower abdominal pain or presenting with pelvic tumors should be aware of splenosis as a possible diagnosis.  相似文献   
70.
Although surgical lung resection could improve prognosis in some patients with multidrug-resistant tuberculosis (MDR-TB), there are no reports on the optimal candidates for this surgery. The aim of the present study was to elucidate the prognostic factors for surgery in patients with MDR-TB. Patients who underwent lung resection for the treatment of MDR-TB between March 1993 and December 2004 were included in the present study. Treatment failure was defined as greater than or equal to two of the five cultures recorded in the final 12 months of treatment being positive, any one of the final three cultures being positive, or the patient having died during treatment. The variables that affected treatment outcomes were identified through univariate and multivariate logistic regression analysis. In total, 79 patients with MDR-TB were included in the present study. The treatment outcomes of 22 (27.8%) patients were classified as failure. A body mass index <18.5 kg x m(-2), primary resistance, resistance to ofloxacin and the presence of a cavitary lesion beyond the range of the surgical resection were associated with treatment failure. Low body mass index, primary resistance, resistance to ofloxacin and cavitary lesions beyond the range of resection are possible poor prognostic factors for surgical lung resection in multidrug-resistant tuberculosis patients.  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