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   16126篇
  免费   789篇
  国内免费   108篇
耳鼻咽喉   81篇
儿科学   207篇
妇产科学   159篇
基础医学   2092篇
口腔科学   358篇
临床医学   996篇
内科学   4198篇
皮肤病学   306篇
神经病学   1279篇
特种医学   800篇
外科学   2782篇
综合类   58篇
一般理论   1篇
预防医学   535篇
眼科学   219篇
药学   1096篇
中国医学   52篇
肿瘤学   1804篇
  2023年   108篇
  2022年   210篇
  2021年   400篇
  2020年   206篇
  2019年   280篇
  2018年   345篇
  2017年   316篇
  2016年   360篇
  2015年   382篇
  2014年   494篇
  2013年   578篇
  2012年   871篇
  2011年   1031篇
  2010年   588篇
  2009年   504篇
  2008年   845篇
  2007年   912篇
  2006年   953篇
  2005年   978篇
  2004年   923篇
  2003年   865篇
  2002年   930篇
  2001年   293篇
  2000年   261篇
  1999年   293篇
  1998年   247篇
  1997年   181篇
  1996年   205篇
  1995年   176篇
  1994年   141篇
  1993年   134篇
  1992年   231篇
  1991年   185篇
  1990年   166篇
  1989年   170篇
  1988年   133篇
  1987年   120篇
  1986年   118篇
  1985年   110篇
  1984年   81篇
  1983年   70篇
  1982年   53篇
  1981年   33篇
  1980年   42篇
  1979年   76篇
  1978年   39篇
  1977年   39篇
  1975年   37篇
  1974年   35篇
  1973年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
PURPOSE: The efficacy of external-beam radiation therapy (RT) was evaluated in the treatment of eyes with subfoveal or juxtafoveal choroidal neovascularization in age-related macular degeneration (ARMD). MATERIALS AND METHODS: Twenty-one eyes of 18 patients with occult or mixed-type ARMD received a total dose of 20 Gy of 6 MV X-rays in 10 fractions. The follow-up time was 24 months. Fifteen non-treated eyes of 13 patients who had been followed served as a control. RESULTS: In the RT group, visual acuity was improved in three eyes, maintained in 14 eyes, and worsened in four eyes. In the control group, it was not improved in any eyes, was maintained in six eyes, and worsened in nine eyes. The improved or maintained rate in visual acuity was 81% in the RT group and 40% in the control group (p=0.0342). In the RT group, fundoscopic and angiographic findings were improved in five eyes, unchanged in seven eyes, and worsened in nine eyes, while they were not improved in any eyes, unchanged in two eyes, and worsened in 13 eyes in the control group(p=0.0342). CONCLUSION: RT at a total dose of 20 Gy in 10 fractions is effective for ARMD for at least two years. RT may be effective treatment for occult or mixed-type ARMD compared with the classic type.  相似文献   
992.
OBJECTIVE: The purpose of our study was to compare the detectability of malignant hepatic tumors on ferumoxides-enhanced MRI using five gradient-recalled echo sequences at different TEs. MATERIALS AND METHODS: Ferumoxides-enhanced MRIs obtained in 31 patients with 50 malignant hepatic tumors (33 hepatocellular carcinomas, 17 metastases) were reviewed retrospectively by three independent offsite radiologists. T1-weighted gradient-recalled echo images with TEs of 1.4 and 4.2 msec; T2*-weighted gradient-recalled echo images with TEs of 6, 8, and 10 msec; and T2-weighted fast spin-echo images of livers were randomly reviewed on a segment-by-segment basis. Observer performance was tested using the McNemar test and receiver operating characteristic analysis for the clustered data. Lesion-to-liver contrast-to-noise ratio was also assessed. RESULTS: Mean lesion-to-liver contrast-to-noise ratios were negative and lower with gradient-recalled echo at 1.4 msec than with the other sequences. Sensitivity was higher (p < 0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (75-83%) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (46-48%), and was higher (p < 0.05) with gradient-recalled echo sequence at 8 msec (83%) than with gradient-recalled echo at 6 msec and fast spin-echo sequences (75-78%). Specificity was comparably high with all sequences (95-98%). The area under the receiver operating characteristic curve (A(z)) was greater (p < 0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (A(z) = 0.91-0.93) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (A(z) = 0.82-0.85). CONCLUSION: In the detection of malignant hepatic tumors, gradient-recalled echo sequences at 8 msec showed the highest sensitivity and had an A(z) value and lesion-to-liver contrast-to-noise ratio comparable with values from gradient-recalled echo sequences at 6 and 10 msec and fast spin-echo sequences.  相似文献   
993.
Hypoperfusion in the posterior cingulate cortex is thought to be useful for the early diagnosis of dementia of Alzheimer type (DAT). In the present study, we compared the incidence of posterior cingulate hypoperfusion in patients with Alzheimer's disease (AD), patients with senile dementia of Alzheimer type (SDAT), and patients with other types of dementia, as evaluated by three-dimensional stereotactic surface projection (3D-SSP) imaging. The subjects were 20 AD patients, 20 SDAT patients, 13 frontotemporal dementia patients, and 3 other types of dementia patients. A SPECT study was performed 5 minutes after the injection of 740 MBq technetium-99m hexamethylpropylene amine oxime. 3D-SSP images were obtained with global normalization to perform the statistical analysis. The normal database of 3D-SSP consisted of 15 healthy volunteers. Hypoperfusion was considered to be significant when the Z-score was over 2.5. Posterior cingulate hypoperfusion was observed in 13 of 20 AD patients (65%), in 5 of 20 SDAT patients (25%), but in none of other type of dementia patients. Posterior cingulate hypoperfusion was considered to be a finding specific to DAT, and this finding was thought to be useful to diagnose DAT patients, especially for AD patients. However, it was considered to be difficult to diagnose early-stage SDAT patients.  相似文献   
994.
BACKGROUND: Though the outcome of resection for locally invasive pancreatic cancer is still poor, it has gradually improved in Japan, and the 5-year survival is now about 10%. However, the advantage of resection over radiochemotherapy has not yet been confirmed by a randomized trial. We conducted this study to compare surgical resection alone versus radiochemotherapy without resection for locally invasive pancreatic cancer using a multicenter randomized design. METHODS: Patients with pancreatic cancer who met our preoperative criteria for inclusion (pancreatic cancer invading the pancreatic capsule without involvement of the superior mesenteric artery or the common hepatic artery, or without distant metastasis) underwent laparotomy. Patients with operative findings consistent with our criteria were randomized into a radical resection group and a radiochemotherapy group (200 mg/m(2)/day of intravenous 5-fluorouracil and 5040 cGy of radiotherapy) without resection. The 2 groups were compared for mean survival, hazard ratio, 1-year survival, quality of life scores, and hematologic and blood chemical data. RESULTS: Twenty patients were assigned to the resection group and 22 to the radiochemotherapy group. There was 1 operative death. The surgical resection group had better results than the radiochemotherapy group as measured by 1-year survival (62% vs 32 %, P=.05), mean survival time (>17 vs 11 months, P < .03), and hazard ratio (0.46, P=.04). There were no differences in the quality of life score or laboratory data apart from increased diarrhea after surgical resection. CONCLUSIONS: Locally invasive pancreatic cancer without distant metastases and major arterial invasion appears to be best treated by surgical resection.  相似文献   
995.
A patient presented with a glomangioma that presented as an aneurysm of the superficial palmar arch. Throbbing pain, tenderness over the tumor, and cold intolerance were clinical features. Cold intolerance was the major problem. The pathologic diagnosis was glomangioma. Excision of the tumor provided a good result and there has been no recurrence.  相似文献   
996.
In three patients undergoing pheochromocytoma resection under propofol/fentanyl anesthesia, bispectral index (BIS) was monitored for assessment of hypnotic effect. In two patients, arterial blood concentrations of propofol were measured by high performance liquid chromatography (HPLC), and compared with those of the estimated blood concentrations. Until resection of the tumor, propofol was infused at a rate of 10 mg x kg(-1) x hr(-1). After resection of the tumor, propofol dosage was reduced to 3-6 mg x kg(-1) x hr(-1), keeping the BIS values around 60. Rapid infusion of fluid and norepinephrine was required to maintain blood pressure after removal of the tumor in two patients. In one patient, blood pressure was maintained well without rapid infusion of fluid or vasopressor. Arterial blood concentration of propofol after resection of the tumor was equal to the estimated blood concentration (3.04 vs 3.02 microg x ml(-1)) in a patient without rapid infusion of fluid. In a patient with rapid infusion of fluid, the arterial blood concentration was lower than the estimated blood concentration (2.59 vs 3.58 microg x ml(-1)). The anesthetic depth can not be estimated accurately by hemodynamic changes in the patients undergoing pheochromocytoma resection. BIS monitoring should be recommended for adjustment of propofol dosage after pheochromocytoma resection.  相似文献   
997.
The relief of intractable pain after spinal cord injury (SCI) is very difficult to obtain, even with dorsal root entry zone lesioning, spinal cord stimulation, and thalamic stimulation. Using bilateral motor cortex stimulation (MCS) the authors successfully treated a woman who experienced deafferentation pain 4 years after sustaining an SCI. To the authors' knowledge, this is the first report of bilateral MCS for pain relief after SCI. The success they achieved using this method indicates that MCS could be a new treatment option for deafferentation pain following SCI.  相似文献   
998.

Purpose

It is generally accepted that postoperative chemotherapy does not affect the serum alpha-fetoprotein (AFP) level. The authors report on 3 patients who supposedly showed chemotherapy-related changes in their AFP levels after operation.

Methods

This study included 3 patients with hepatoblastoma (1 case of PRETEXT III and 2 cases of PRETEXT IV).

Results

One patient with PRETEXT III underwent a complete tumor resection, and the postoperative AFP level decreased until it reached the normal range. However, he consistently exhibited a transient, 2- to 3-fold increase in the AFP after each course of chemotherapy for 3 courses. The chemotherapy regimen had to be stopped because of drug-induced encephalopathy, but he has been followed up for 5 years without any evidence of recurrence, and his AFP level has also remained stable and in the normal range. Two patients with PRETEXT IV, who underwent a curative tumor resection, also showed similar chemotherapy-related changes in AFP levels. Both of these cases were observed only after the administration of routine postoperative chemotherapy instead of administering further high-dose chemotherapy. The AFP level remained stable for 17 months and 7 months after the cessation of chemotherapy in 2 cases, respectively.

Conclusions

Regarding the postoperative chemotherapy of hepatoblastoma, we have to pay close attention to both the AFP status during chemotherapy as well as the absolute AFP level.  相似文献   
999.
Jito J  Nakasu Y  Nakasu S  Hatsuda N  Matsuda M 《Neurologia medico-chirurgica》2004,44(2):55-60; discussion 60
Tissue plasminogen activator (tPA) levels were investigated in the cisternal fluid of patients with subarachnoid hemorrhage treated with single intracisternal injection of recombinant tPA during radical surgery for ruptured aneurysms. Seven patients received different doses of tPA: two of 400 microg/ml, three of 500 microg/ml, one of 700 microg/ml, and one of 800 microg/ml in a total amount of 20 ml distilled water at pH 7. Cerebrospinal fluid samples were taken directly from the cisternal fluid at 15-minute incubation after injection, immediately after irrigation during surgery, and by lumbar tap 2 days after surgery. Cisternal tPA levels decreased to about 60% of the mean injected doses after 15-minute incubation. Simple linear regression analysis showed these tPA levels after incubation correlated with the initial doses. After copious irrigation with Ringer solution at pH 8, tPA levels decreased rapidly without correlation with the initial doses. After spinal drainage for 2 days, tPA levels further decreased by an order of 10(-4) to 10(-6) from the initial dose. These values were still greater than normal controls. The final values of tPA levels were not related to the initial dose. None of the patients suffered from systemic or wound complications. Cisternal tPA injection with increased doses and irrigation may be beneficial for the selective rapid removal of blood clots with controllable safety.  相似文献   
1000.
Glomus tumor of the lateral aspect of the knee joint   总被引:1,自引:0,他引:1  
Background We report a rare case of glomus tumor that occurred in the lateral joint of the knee. A 54yearold man was referred to us with a 3year history of lateral pain in the left knee and the diagnosis of lateral meniscus injury. Physical examination revealed a small trigger point localized just on the lateral joint space. Magnetic resonance imaging (MRI) showed a very small round mass in the subcutaneous tissue at the level of the lateral joint space.Treatment Excisional biopsy was performed, and the histology was characteristic of a glomus tumor. The patient was asymptomatic immediately after the operation. At the 3-year followup after the operation, no recurrence was seen.No benefits in any form have been received or will be received from any commercial party related directly of indirectly to the subject of this article. No funds were received in support of this study.  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