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   1423篇
  免费   73篇
  国内免费   5篇
耳鼻咽喉   2篇
儿科学   24篇
妇产科学   18篇
基础医学   180篇
口腔科学   18篇
临床医学   70篇
内科学   260篇
皮肤病学   44篇
神经病学   193篇
特种医学   59篇
外科学   125篇
综合类   4篇
预防医学   43篇
眼科学   25篇
药学   60篇
中国医学   3篇
肿瘤学   373篇
  2023年   4篇
  2022年   8篇
  2021年   27篇
  2020年   16篇
  2019年   23篇
  2018年   40篇
  2017年   27篇
  2016年   24篇
  2015年   18篇
  2014年   43篇
  2013年   55篇
  2012年   110篇
  2011年   90篇
  2010年   48篇
  2009年   54篇
  2008年   68篇
  2007年   96篇
  2006年   87篇
  2005年   90篇
  2004年   78篇
  2003年   86篇
  2002年   75篇
  2001年   18篇
  2000年   24篇
  1999年   29篇
  1998年   23篇
  1997年   17篇
  1996年   14篇
  1995年   8篇
  1994年   10篇
  1993年   14篇
  1992年   17篇
  1991年   12篇
  1990年   17篇
  1989年   9篇
  1988年   18篇
  1987年   16篇
  1986年   8篇
  1985年   11篇
  1984年   8篇
  1983年   9篇
  1981年   5篇
  1980年   9篇
  1979年   5篇
  1978年   6篇
  1976年   4篇
  1974年   3篇
  1972年   3篇
  1970年   3篇
  1969年   3篇
排序方式: 共有1501条查询结果,搜索用时 62 毫秒
1.
Neurosonography by advanced transvaginal sonography has revealed normal and abnormal intracranial morphology. Transvaginal 3D sonography demonstrates bony structures, multiplanar analysis of inside detailed morphology, tomographic ultrasound imaging in any cutting sections, 3D sonoangiography and volume calculation of ventricles and/or intracranial lesions. Longitudinal assessment of normal and abnormal CNS development is easy by serial scanning. However, the transvaginal approach has several limitations due to its observation by use of a high-frequency transducer from the fetal parietal region. Evaluation of the brainstem and posterior fossa, which are located far from the parietal ultrasound windows of the anterior fontanelle or sagittal suture, is sometimes hard by transvaginal sonography. Visualization of bilateral temporal areas is getting difficult with advanced gestational weeks because of bilateral acoustic shadows due to ossification of parietal bones. Demonstration of frontal/occipital areas is sometimes impossible in late pregnancy due to scan-angle limitation of the transvaginal transducer. From our experiences, the main difference between transvaginal 3D ultrasound and MRI is demonstration of the whole gyral and sulcal formation and brainstem in the late second and third trimesters. Although MRI is a useful modality which can compensate for pitfalls of transvaginal 3D ultrasound, 3D ultrasound is sometimes superior to MRI in detecting cysts in cyst and intracranial calcification. Transvaginal 3D ultrasound is much superior to MRI in detecting bony structures and angioarchitectonics and in volumetric assessment. Regarding objective and accurate prenatal diagnosis, any less-invasive modalities can be used. After considering each advantage and disadvantage of transvaginal 3D ultrasound and MR imaging, it is suggested to use the different technologies according to what is to be detected and evaluated.  相似文献   
2.
3.
Serum level of sex hormone-binding globulin (SHBG) was measured by immunoradiometric assay in fifty two breast cancer patients and twenty nine healthy female volunteers. The results are as follows: 1) Although the serum SHBG concentration showed no significant difference between the breast cancer group and the healthy control group, the serum SHBG concentration in postmenopause was significantly higher in the breast cancer group (63.8 +/- 31.2nmol/ml/ml; mean +/- S.D.) than in the healthy control group (40.1 +/- 15.4nmol/ml). 2) Subsequently in the postmenopausal breast cancer group, the serum SHBG concentration was significantly higher in the estrogen receptor (ER)-negative cancer group (97.8 +/- 12.7nmol/ml) than in the ER-positive cancer group (55.8 +/- 32.1nol/ml). 3) No significant relationships were showed between the serum SHBG concentration and obesity or serum estradiol concentration in postmenopausal patients. 4) The serum SHBG concentration showed significant decrease 3 months after radical operation for breast cancer in postmenopausal patients. These results suggest the possibility of the SHBG synthesis in breast cancer tissue.  相似文献   
4.
Brain metastasis in patients with superior sulcus tumors   总被引:2,自引:0,他引:2  
During a 20-year period, from 1963 to 1983, 68 patients were treated for carcinoma of the lung presenting in the superior sulcus. Their ages ranged from 41 to 79 years (median, 56 years). Thirty-six patients had squamous cell carcinoma, 13 had adenocarcinoma, 14 had large cell carcinoma, two had small cell carcinoma, and three had clinical diagnosis only. All tumors were considered to be inoperable or unresectable and were treated with external irradiation alone. The 3-year disease-free survival was 25%. Brain metastasis developed in 23 patients (34%); the brain was the first site of metastasis in 16 patients (24%), five of whom eventually developed other sites of metastasis. The cumulative probability of brain metastasis was 53% at 3 years. Brain metastases were seen in ten patients (28%) with squamous cell carcinoma, five patients (38%) with adenocarcinoma, seven patients (50%) with large cell carcinoma, and one patient without a histocytologic diagnosis. The proportion of patients younger than 60 years (19/41, 46%) who developed brain metastasis was significantly greater than that for patients 60 years or older (4/27, 15%) (P less than or equal to 0.01). Nine of 11 patients with metastasis only to the brain died as a consequence of the intracranial disease 1 to 13 months (median, 6 months) after the diagnosis of brain metastases. The other two patients received therapeutic irradiation to the entire brain and survived longer than 5 days after the whole-brain irradiation: one died at 62 months of intercurrent disease, and the other is alive and well 129 months after diagnosis. The high probability of brain metastasis from superior sulcus tumors, regardless of histopathologic type and the frequency with which the brain is the only site of clinical failure, suggest that systematic prophylactic cranial irradiation could reduce the morbidity and perhaps even contribute favorably to the survival of these patients.  相似文献   
5.
Breast cancer detected by mass screening using physical examination alone   总被引:4,自引:0,他引:4  
In Tokushima prefecture, mass screening for breast cancer has been conducted using physical examination alone since 1970. Breast cancer was detected in 116 of 111,571 screened women up until 1984. The detection rate was 0.08 per cent in total examinees, 0.13 per cent in initial examinees, and 0.04 per cent in subsequent examinees. The patients with breast cancer were divided into three groups, i.e., 62 cases detected at initial screening, 28 cases detected at subsequent screenings, and 26 interval cancer cases. 510 patients with breast cancer in the outpatient clinic were serving as controls. The stage classification and nodal involvement were significantly different between the mass screening group and the control group, but not significantly different among the three groups. The interval cases were detected at an early stage. The survival rates were not significantly different between the three groups and the control group. Efforts should be doubled to educate women about the proper method of breast self-examination in order to promote the early detection of breast cancer.  相似文献   
6.
The effects of simultaneous increases in dietary phosphorus (P) and magnesium (Mg) concentrations while maintaining a constant P:Mg ratio on nephrocalcinosis and kidney function in female rats was investigated. Female Wistar rats were fed a control diet (3.12 g P, 0.51 g Mg per kg diet) or a diet having either 3 times the control P and Mg concentrations (3-fold diet; 9.25 g P and 1.42 g Mg per kg diet) or 5 times the control concentrations (5-fold diet; 14.97 g P and 2.37 g Mg per kg diet) for 21 d. The three experimental diets all had same P:Mg molar ratios (control diet; 4.81, 3-fold diet; 5.11, 5-fold diet; 4.96). The 3-fold diet had no significant influence on kidney calcium (Ca), Mg or P concentrations. However, kidney Ca, Mg and P concentrations were significantly higher in rats fed the 5-fold diet than in rats fed the control or 3-fold diets. No significant differences in creatinine clearance were observed among the three groups. Urinary albumin and beta 2-microglobulin excretion were higher in rats fed the 5-fold diet than in rats fed the control or 3-fold diets, while the 3-fold diet had no significant influence on the urinary albumin and beta 2-microglobulin excretion. These results suggest that absolute concentrations of dietary P and Mg are important factors with regard to the development of nephrocalcinosis and diminished kidney function.  相似文献   
7.
8.
OBJECTIVE: Repetitive paired-pulse transcranial magnetic stimulation (TMS) at I-wave periodicity has been shown to induce a motor-evoked potential (MEP) facilitation. We hypothesized that a greater enhancement of motor cortical excitability is provoked by increasing the number of pulses per train beyond those by paired-pulse stimulation (PPS). METHODS: We explored motor cortical excitability changes induced by repetitive application of trains of four monophasic magnetic pulses (quadro-pulse stimulation: QPS) at 1.5-ms intervals, repeated every 5s over the motor cortex projecting to the hand muscles. The aftereffects of QPS were evaluated with MEPs to a single-pulse TMS, motor threshold (MT), and responses to brain-stem stimulation. These effects were compared to those after PPS. To evaluate the QPS safety, we also studied the spread of excitation and after discharge using surface electromyograms (EMGs) of hand and arm muscles. RESULTS: Sizes of MEPs from the hand muscle were enhanced for longer than 75min after QPS; they reverted to the baseline at 90min. Responses to brain-stem stimulation from the hand muscle and cortical MEPs from the forearm muscle were unchanged after QPS over the hand motor area. MT was unaffected by QPS. No spreads of excitation were detected after QPS. The appearance rate of after discharges during QPS was not different from that during sham stimulation. CONCLUSIONS: Results show that QPS can safely induce long-lasting, topographically specific enhancement of motor cortical excitability. SIGNIFICANCE: QPS is more effective than PPS for inducing motor cortical plasticity.  相似文献   
9.
A 75-year-old man was admitted to our hospital with dysesthesia of the right lip, dysphagia and gait disturbance. He presented with right Wallenberg syndrome and brain MR image showed a fresh infarction in the right lateral medulla. Therapy with heparin and ozagrel sodium was started. For a time his symptom improved a little, but after 8 days he developed re-infarction, thrombocytopenia and DIC, while being treated with heparin for cerebral infarction. Heparin was discontinued, and these symptoms improved quickly. The clinical course and the positive anti-platelet factor 4-heparin complex antibody suggested that these symptoms were caused by heparin-induced thrombocytopenia (HIT). HIT should be included as a differential diagnosis for progression of ischemic stroke under heparin therapy.  相似文献   
10.
For almost 20 years, the neutralizing-epitope site specific for influenza B virus Victoria group isolates was conserved at the "tip" of the hemagglutinin molecule; however, it was not detected in half of the isolates from the 2002-2003 epidemic in Japan. Amino acid substitutions (D164E or N165K) were observed at the "tip", and the epitope was altered. The viral antigenicities were affected, and human antibodies did not substantially inhibit the hemagglutination in the hemagglutination inhibition tests. It is suspected that such variants will be important in future epidemics.  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