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   22645篇
  免费   1463篇
  国内免费   127篇
耳鼻咽喉   287篇
儿科学   465篇
妇产科学   438篇
基础医学   3211篇
口腔科学   463篇
临床医学   2024篇
内科学   5223篇
皮肤病学   302篇
神经病学   2262篇
特种医学   901篇
外科学   2918篇
综合类   217篇
一般理论   67篇
预防医学   1884篇
眼科学   891篇
药学   1283篇
中国医学   31篇
肿瘤学   1368篇
  2023年   83篇
  2022年   183篇
  2021年   426篇
  2020年   245篇
  2019年   357篇
  2018年   458篇
  2017年   345篇
  2016年   392篇
  2015年   441篇
  2014年   653篇
  2013年   884篇
  2012年   1359篇
  2011年   1507篇
  2010年   829篇
  2009年   791篇
  2008年   1352篇
  2007年   1424篇
  2006年   1264篇
  2005年   1357篇
  2004年   1209篇
  2003年   1147篇
  2002年   1137篇
  2001年   295篇
  2000年   271篇
  1999年   308篇
  1998年   244篇
  1997年   256篇
  1996年   204篇
  1995年   176篇
  1994年   133篇
  1993年   133篇
  1992年   193篇
  1991年   172篇
  1990年   179篇
  1989年   129篇
  1988年   141篇
  1987年   141篇
  1986年   149篇
  1985年   152篇
  1984年   160篇
  1983年   154篇
  1982年   151篇
  1981年   173篇
  1980年   145篇
  1979年   123篇
  1978年   107篇
  1977年   104篇
  1975年   112篇
  1974年   101篇
  1973年   120篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
PURPOSE: Torsion of the testis is a urologic emergency that requires early diagnosis and prompt surgical treatment for testicular survival. However, the early differential diagnosis of acute testicular torsion from epididymitis or orchitis is often difficult. The aim of this retrospective study was to evaluate and compare the value of Tc-99m pertechnetate radionuclide imaging and ultrasonography in the differentiation of acute testicular torsion and inflammatory testicular diseases. METHODS: Twenty patients (age range, 5 to 38 years) with possible acute testicular torsion from July 2000 to July 2001 were enrolled in this study. Ultrasonography was performed in all patients in the emergency room. Within 3 hours of ultrasonography, radionuclide imaging was also performed after intravenous injection of 5 to 15 mCi Tc-99m pertechnetate in the forearms. All of the patients with clinically suspected acute testicular torsion underwent surgery. The surgical findings and pathologic reports of these patients were reviewed and definite diagnoses were established. None of the other patients had surgery and were followed clinically for at least 1 month after ultrasonography and radionuclide imaging. RESULTS: Four patients with testicular torsion, 13 patients with inflammatory testicular disease, and three healthy persons had a final surgical and pathologic diagnosis or clinical follow-up, and all were accurately diagnosed by Tc-99m pertechnetate radionuclide imaging. In contrast, ultrasonography was less accurate in the diagnosis and differentiation of acute testicular torsion from inflammation. Only 1 of 4 patients with testicular torsion, 5 of 13 patients with inflammatory testicular disease, and 2 of 3 healthy persons were diagnosed by ultrasonography. CONCLUSIONS: The results indicate that Tc-99m pertechnetate radionuclide imaging is a more useful and accurate imaging method than ultrasonography in the detection and differentiation of acute testicular torsion from inflammatory testicular disease in patients with acute scrotal pain.  相似文献   
992.
Among the ways to deliver comparatively large amounts of boron to cells in vitro for boron neutron capture studies is the linkage of a boronated macromolecule such as polylysine to an antibody. In order to reduce interference with immunoreactivity, boronated polylysine (BPL) was linked to oligosaccharide moieties on the IgG molecule distant from the antibody combining sites. The resultant bioconjugate was chromatographically separated from free BPL and unconjugated antibody using a Sephacryl S300 column. The total measured boron per BPL-IgG conjugate, determined by direct current plasma atomic emission spectroscopy, was estimated to be approximately 6 x 10(3) atoms. This, together with molecular weight estimations, indicated conjugation of about 3 polylysines to each IgG molecule. Immunoreactivity of the conjugate was found to be the same as that of the unconjugated polyclonal antibody. This was based on its concentration dependent interference with immunometric reactions for an antigen (TSH), whereas heat inactivated or non-specific antibody had no such inhibitory effects. The results support the hypothesis that the binding affinity of the conjugate for antigen was preserved after its linkage to BPL under the conditions described. The methodology described in this report may have applicability for the preparation of boronated antibodies as delivery agents for BNCT.  相似文献   
993.
Multiple opportunistic infections and neoplasms have been described in the AIDS population over the past 20 years. Four cases of AIDS-related hepatic smooth muscle tumors (leiomyomas) have been described, and of these, three were in children. The fourth case was in a single patient with two hepatic lesions. We describe the imaging features of two adult cases with biopsy-proven hepatic leiomyomas. In one of the cases, the gadolinium-enhanced MRI findings are described, which have not previously been reported. Electronic Publication  相似文献   
994.
995.
BACKGROUND: Supraomohyoid neck dissection (SOHND) is generally considered an adequate staging procedure in selected patients with squamous cell carcinoma (SCC) of the lip and oral cavity, with clinically negative nodes in the neck that are at increased risk for occult metastatic disease. The potential role of SOHND as a therapeutic surgical procedure for cervical metastasis limited to level I is controversial. METHODS: A series of 44 patients with clinical cervical lymph node metastases at level I from SCC of the lower lip is reported to evaluate the results of a treatment protocol consisting of therapeutic SOHND on indication followed by radiotherapy. RESULTS: Regional recurrences were observed in four (9%) patients. All recurrences developed within the SOHND dissected area only. CONCLUSIONS: A therapeutic SOHND, on indication followed by radiotherapy, can be an oncologically sound and effective procedure in the management of regional lymph node metastases at level I from SCC of the lower lip.  相似文献   
996.
Omental free flap reconstruction in complex head and neck deformities   总被引:3,自引:0,他引:3  
BACKGROUND: Microvascular free flaps continue to revolutionize coverage options in head and neck reconstruction. This article reviews our 25-year experience with omental free tissue transfers. METHODS: All patients who underwent free omental transfer to the head and neck region were reviewed. RESULTS: Fifty-five patients were included with omental transfers to the scalp (25%), craniofacial (62%), and neck (13%) region. Indications were tumor resections, burn wound, hemifacial atrophy, trauma, and moyamoya disease. Average follow-up was 3.1 years (range, 2 months-13 years). Donor site morbidities included abdominal wound infection, gastric outlet obstruction, and postoperative bleeding. Recipient site morbidities included partial flap loss in four patients (7%) total flap loss in two patients (3.6%), and three hematomas. CONCLUSIONS: The omental free flap has acceptable abdominal morbidity and provides sufficient soft tissue coverage with a 96.4% survival. The thickness \and versatility of omentum provide sufficient contour molding for craniofacial reconstruction. It is an attractive alternative for reconstruction of large scalp defects and badly irradiated tissue.  相似文献   
997.
BACKGROUND: Syphilitic involvement of the nervous system can present in many different ways. We report a patient who presented with rapidly evolving paraparesis secondary to syphilitic meningomyelitis. METHODS: Case report. FINDINGS: Cerebrospinal fluid (CSF) studies confirmed the diagnosis of neurosyphilis. Spinal magnetic resonance imaging (MRI) studies were indicative of leptomeningeal and thoracic spinal cord disease. Treatment with IV penicillin resulted in marked clinical, radiologic, and CSF improvement. MRI imaging provided documentation of spinal cord involvement and was useful in monitoring recovery. This patient's progressive neurologic improvement was monitored for 2 years and documented by periodic Functional Independence Measure scores. CONCLUSION: Recognition of this unusual complication of secondary neurosyphilis is important, because it is a treatable cause of paraparesis with potential for good recovery.  相似文献   
998.
999.
Neuronavigation, today a routine method in neurosurgery, has not yet been systematically assessed in direct comparison with conventional microsurgical techniques. The aim of the present study was the direct comparison of the impact of neuronavigation on glioblastoma surgery regarding time consumption, extent of tumor removal and survival. For each of 52 patients operated for primary glioblastoma with neuronavigation, a patient operated on without navigation was matched. Completeness of tumor resection, including volumetric analysis, was examined by early post-operative MRI. Operating and survival times were obtained for all patients. At a rate of 86.5%, surgeons' opinions about neuronavigation were positive. Operating times were identical in the two groups, while preparation times were 30.4 min longer with navigation. Radiological radicality was achieved in 31% of navigation cases vs. 19% in conventional operations. The absolute and relative residual tumor volumes were significantly lower with neuronavigation. Radical tumor resection was associated with a highly significant prolongation in survival (median 18.3 vs. 10.3 months, p < 0.0001). Survival was longer in patients operated on using neuronavigation (median 13.4 vs. 11.1 months). Neuronavigation increases radicality in glioblastoma resection without prolonging operating time. Regarding the problem of brain shift, neuronavigation should be optimized by intraoperative real-time imaging.  相似文献   
1000.
In all, 19 research subjects, with current histories of frequent cocaine use, were exposed to cocaine-related cues to elicit drug craving. We measured the change of occupancy of dopamine at D2-like receptors with positron emission tomography (PET) and inferred a change of intrasynaptic dopamine (endogenous dopamine release), based on the displacement of radiotracer [(11)C]raclopride. Receptor occupancy by dopamine increased significantly in putamen of participants who reported cue-elicited craving compared to those who did not. Further, the intensity of craving was positively correlated with the increase in dopamine receptor occupancy in the putamen. These results provide direct evidence that occupancy of dopamine receptors in human dorsal striatum increased in proportion to subjective craving, presumably because of increased release of intrasynaptic dopamine.  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