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   4755篇
  免费   242篇
  国内免费   56篇
耳鼻咽喉   70篇
儿科学   89篇
妇产科学   94篇
基础医学   634篇
口腔科学   116篇
临床医学   444篇
内科学   807篇
皮肤病学   153篇
神经病学   331篇
特种医学   281篇
外科学   585篇
综合类   57篇
一般理论   3篇
预防医学   250篇
眼科学   68篇
药学   586篇
中国医学   111篇
肿瘤学   374篇
  2023年   32篇
  2022年   114篇
  2021年   183篇
  2020年   92篇
  2019年   119篇
  2018年   144篇
  2017年   105篇
  2016年   142篇
  2015年   200篇
  2014年   262篇
  2013年   285篇
  2012年   390篇
  2011年   405篇
  2010年   232篇
  2009年   174篇
  2008年   272篇
  2007年   262篇
  2006年   235篇
  2005年   199篇
  2004年   166篇
  2003年   146篇
  2002年   111篇
  2001年   101篇
  2000年   83篇
  1999年   86篇
  1998年   58篇
  1997年   46篇
  1996年   38篇
  1995年   24篇
  1994年   28篇
  1993年   17篇
  1992年   35篇
  1991年   31篇
  1990年   30篇
  1989年   29篇
  1988年   18篇
  1987年   16篇
  1986年   11篇
  1985年   20篇
  1983年   7篇
  1981年   9篇
  1979年   7篇
  1977年   5篇
  1975年   5篇
  1974年   8篇
  1972年   5篇
  1971年   8篇
  1969年   6篇
  1968年   14篇
  1967年   5篇
排序方式: 共有5053条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: This study evaluates several tumor-related markers to examine the expression pattern of markers according to the invasiveness and histopathologic differentiation of squamous cell carcinoma and basal cell carcinoma. METHODS: Ninety-four cases of squamous cell carcinoma and 108 cases of basal cell carcinoma using tissue array in order to determine correlations between the expression of Ki-67, p53, EGFR, CD44v6, MMP-1 and MMP-3, invasiveness and histologic differentiation. In order to determine invasiveness, we measured the depth of invasion in resected tissues. RESULTS: The depth of invasion showed a correlation with CD44v6 expression of tumor cell in both squamous cell carcinoma and basal cell carcinoma (P = 0.009, P = 0.036, respectively) and with the MMP-1 expression of stromal cell in squamous cell carcinoma (P = 0.010). The differentiation of squamous cell carcinoma was correlated with Ki-67 index. The loss of palisading arrangement in basal cell carcinoma was correlated with the MMP-1 expression of stromal cells (P = 0.045). CONCLUSIONS: CD44v6 and MMP-1, expressed in tumor cells and stromal cells respectively, are significant markers associated with the invasiveness of tumors in squamous cell carcinoma and basal cell carcinoma of the skin and that it will be helpful to evaluate the invasiveness by measuring the expression of these markers.  相似文献   
992.
The specificity and dose dependence of the synergistic effects of soybean intake with iodine deficiency on the induction of thyroid proliferation were investigated in female F344 rats. In the first experiment, rats were divided into 6 groups, each consisting of 5 annuals, and fed a basal diet containing 20% gluten, an iodine-deficient basal diet alone or an iodine-deficient diet containing 0.2%, 1.0%, 5.0% or 25% defatted soybean for 5 weeks. Soybean feeding synergistically induced thyroid hyperplasias with iodine deficiency only at the 25% dose. In the second experiment, rats were also divided into 6 groups, each consisting of 5 animals, and fed a basal diet, a diet containing 20% defatted soybean, 0.025% Sulfadimethoxine (SDM), 20% defatted soybean+0.025% SDM, 0.05% phenobarbital (PB) or 20% defatted soybean+0.05% PB for 5 weeks. The SDM treatments significantly (P<0.05-0.01) increased the thyroid weights, but this increase rate was less prominent in the SDM+soybean group than in the SDM alone group. The PB treatment was also associated with a tendency for increase in thyroid weight, but again this was smaller in the PB+soybean group than in the PB alone group. Although the SDM or PB treatments reduced the serum triiodothyronine and thyroxine levels and consequently increased the serum thyroid-stimulating hormone (TSH) levels, the soybean feeding did not affect or rather attenuated these changes. Our results clearly indicate that soybean feeding does not synergistically enhance the effects of SDM or PB on the rat thyroid. Thus it can be concluded that soybean intake specifically interacts with iodine deficiency in induction of thyroid proliferative lesions in rats, only at high doses.  相似文献   
993.
Inflammation is a frequent radiation-induced reaction following therapeutic irradiation. Treatment of human umbilical endothelial cells (HUVEC) with gamma-irradiation (gammaIR) induces the expression of adhesion proteins such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Since the upregulation of these proteins on endothelial cell surface has been known to be associated with inflammation, interfering with the expression of adhesion molecules is an important therapeutic target. In the present study, we demonstrate that high mannuronic acid-containing alginate (HMA) inhibits gammaIR induced expression of ICAM-1, VCAM-1, and E-selectin on HUVEC in a dose dependent manner. HMA also inhibited gammaIR induced production of Nitric oxide (NO). These data suggest that HMA has therapeutic potential for the treatment of various inflammatory disorder associated with an increase of endothelial leukocyte adhesion molecules.  相似文献   
994.
Kim YH  Jang SH  Chang Y  Byun WM  Son S  Ahn SH 《Neuroreport》2003,14(10):1329-1332
This fMRI study was undertaken to test whether the pathophysiological mechanism of mirror movements in hemiparetic stroke patients involves activation of the unaffected motor cortex. We studied 16 control subjects and 51 stroke patients. fMRI was performed at 1.5 T using a finger flexion-extension movement paradigm. The incidence of bilateral primary sensorimotor cortex activation was significantly increased during movements of the affected hand of stroke patients who showed mirror movements. Moreover, the incidence of bilateral primary sensorimotor cortex activation increased with the severity of mirror movements and primary sensorimotor cortex was activated bilaterally in all patients who showed sustained mirror movements. We conclude that the motor cortex activation on the non-stroke side is associated with mirror movements and is correlated with the severity of mirror movements. It seems that the pathophysiological mechanism of sustained mirror movements in stroke patients involves the unaffected motor cortex.  相似文献   
995.

Objective

To investigate the effect of long zona dissection (LZD) compared with partial zona dissection (PZD) using ICSI pipettes for mechanical assisted hatching (AH) in vitrified-thawed blastocyst transfers.

Design

Prospective study.

Setting

University IVF clinic.

Patient(s)

A total of 120 women ≦ 38 years old undergone vitrified-thawed blastocyst transfers with LZD or PZD.

Intervention(s)

The culture of all pronucleate embryos to the blastocyst stage and the selection of blastocysts ≧ grade 3BB (Gardner and Schoolcraft score), followed by vitrified-thawed blastocyst transfers with LZD (n = 60) or with PZD (n = 60)

Main outcome measure(s)

Complete hatching rates, implantation rates, pregnancy rates.

Result(s)

At 5 h after thawing, complete hatching rates of blastocysts were significantly higher in LZD group compared with PZD group, 52.4 % vs. 31.8 % (P = 0.001). Implantation and clinical pregnancy rates were significantly higher in LZD group compared with PZD group, 40.9 % vs. 25.7 % and 63.0 % vs. 40.0 %, respectively (P = 0.010, P = 0.011).

Conclusion(s)

LZD using ICSI pipettes for mechanical AH improves significantly complete hatching, implantation and pregnancy rates in vitrified-thawed blastocyst transfers.  相似文献   
996.
Glucagon-like peptide-1 (GLP-1) is the main member of the incretin family and stimulates insulin secretion by binding with its specific receptor on pancreatic β-cells. In addition, GLP-1 exerts broad beneficial effects on the glucose regulation by suppressing food intake and delaying stomach emptying. Now, long acting GLP-1 analogs including exenatide and liraglutide have been approved for the treatment of diabetes mellitus type 2, however long-term injection can limit their use for these chronic patients. In this report, the authors provide a review on the development of non-peptide GLP-1 receptor agonists and introduce a novel agonist DA-15864.  相似文献   
997.
BACKGROUND/AIMS: Carcinogenesis is characterized by the abnormal regulation of cell cycle. The abnormal expression of the regulators of cell cycle may be related to the prognosis. Since the clinical significance of the expression of the three proteins in colorectal carcinomas is still controversial, we evaluated the prognostic value of the expression of cyclin E, p27 and mutant p53 in stage II colorectal cancer. METHODS: The expression levels of cyclin E, p27 and mutant p53 proteins in 41 patients with stage II colorectal carcinomas were analyzed by immunohistochemistry. RESULTS: In the univariate analysis, the level of CEA at diagnosis was associated with disease relapse. In the multivariate analysis, the clinicopathological variables such as age, gender, site of primary tumor, tumor size, state of tumor differentiation and preoperative plasma CEA level were not associated with disease relapse. When Kaplan-Meier survival curves were constructed to determine the prognosis, cyclin E, p27 and mutant p53 expressions did not predict poor prognosis. CONCLUSIONS: Our results suggested that the expression of cyclin E, p27 and mutant p53 proteins did not predict the clinical outcome in the stage II colorectal carcinomas.  相似文献   
998.
OBJECTIVE: To compare the diagnostic accuracy of integrated 18F-fluorodeoxyglucose PET/CT with ultrasonography (US) and contrast enhanced CT (CECT) alone in the initial evaluation of cervical lymph node levels of patients with papillary thyroid carcinoma. PATIENTS AND MEASUREMENTS: From July 2004 to March 2005, 26 consecutive patients with papillary thyroid carcinoma, confirmed by aspiration cytology analysis, underwent US, CECT and PET/CT. The sensitivity, specificity and diagnostic accuracy of the US, CECT and PET/CT studies for the final status of 312 cervical node levels (levels I-V: 260, level VI: 52) were compared by employing a generalized estimating equation test. The final status of cervical node levels was determined by the surgical pathology and follow-up data. RESULTS: At all lymph node levels (levels I-VI), PET/CT showed a sensitivity of 30.4%, a specificity of 96.2% and a diagnostic accuracy of 86.9%. The corresponding values for US and CECT were 41.3%, 97.4%, 89.1% (US) and 34.8%, 96.2%, 87.2% (CECT). Considering only the lateral cervical node group (levels I-V), PET/CT showed a sensitivity of 50.0%, a specificity of 97.0% and a diagnostic accuracy of 92.3%. The corresponding values for US and CECT were 53.9%, 97.9%, 93.5% (US) and 42.3%, 96.6%, 91.2% (CECT). The diagnostic results for US, CECT and PET/CT upon initial evaluation of the cervical lymph nodes did not differ significantly on a level-by-level basis. CONCLUSION: Our preliminary results suggest that integrated PET/CT does not provide any additional benefit when compared to US and CECT for the initial evaluation of cervical node levels in patients with papillary thyroid carcinoma.  相似文献   
999.
Hemoglobinopathies have a protective role in malaria that appears to be related to alterations in red blood cell (RBC) properties. Thalassemic RBCs infected with Plasmodium falciparum showed greatly reduced cytoadherence and rosetting properties as well as impaired growth and multiplication. A significant decrease in the levels of falciparum antigens associated with the membrane of infected beta-thalassemic RBCs was observed at trophozoite/schizont stage, but not young ring stage. This reduction was shown when a cytoadherence inhibitory monoclonal antibody, but not a noninhibitory pooled immune serum, was used. These observations suggest that protection against malaria in thalassemia is caused by both reduced parasitemias and altered adherence properties of the infected thalassemic RBCs that promote enhanced clearance of the parasite from the circulation.  相似文献   
1000.
Ahn CB  Son KH  Lee JJ  Choi J  Song SJ  Jung JS  Lee SH  Son HS  Sun K 《Artificial organs》2011,35(11):1123-1126
Blood viscosity during operation of ventricular assist device (VAD) can be changed by various conditions such as anemia. It is known generally that the blood viscosity can affect vascular resistance and lead to change of blood flow. In this study, the effect of fluid viscosity variation on hemodynamic energy was evaluated with a pulsatile blood pump in a mock system. Six solutions were used for experiments, which were composed of water and glycerin and had different viscosities of 2, 2.5, 3, 3.5, 4, and 4.5 cP. The hemodynamic energy at the outlet cannula was measured. Experimental results showed that mean pressure was increased in accordance with the viscosity increase. When the viscosity increased, the mean pressure was also increased. However, the flow was decreased according to the viscosity increase. Energy equivalent pressure value was increased according to the viscosity-induced pressure rise; however, surplus hemodynamic energy value did not show any apparent changing trend. The hemodynamic energy made by the pulsatile VAD was affected by the viscosity of the circulating fluid.  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