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   4289篇
  免费   177篇
  国内免费   34篇
耳鼻咽喉   48篇
儿科学   62篇
妇产科学   13篇
基础医学   533篇
口腔科学   293篇
临床医学   236篇
内科学   1139篇
皮肤病学   54篇
神经病学   160篇
特种医学   310篇
外科学   610篇
综合类   35篇
一般理论   3篇
预防医学   57篇
眼科学   50篇
药学   207篇
中国医学   19篇
肿瘤学   671篇
  2023年   22篇
  2022年   39篇
  2021年   106篇
  2020年   68篇
  2019年   63篇
  2018年   94篇
  2017年   70篇
  2016年   101篇
  2015年   100篇
  2014年   131篇
  2013年   146篇
  2012年   273篇
  2011年   312篇
  2010年   192篇
  2009年   133篇
  2008年   255篇
  2007年   311篇
  2006年   264篇
  2005年   299篇
  2004年   298篇
  2003年   287篇
  2002年   254篇
  2001年   41篇
  2000年   37篇
  1999年   47篇
  1998年   50篇
  1997年   57篇
  1996年   54篇
  1995年   61篇
  1994年   39篇
  1993年   31篇
  1992年   24篇
  1991年   29篇
  1990年   32篇
  1989年   17篇
  1988年   33篇
  1987年   20篇
  1986年   12篇
  1985年   13篇
  1984年   10篇
  1983年   9篇
  1982年   9篇
  1981年   5篇
  1980年   14篇
  1978年   3篇
  1977年   8篇
  1975年   3篇
  1973年   4篇
  1970年   4篇
  1966年   3篇
排序方式: 共有4500条查询结果,搜索用时 15 毫秒
1.
2.
miRNA‐221 (miR‐221) is known to be abnormally expressed in many human cancers. The serum levels of miR‐221 have been reported as a tumor marker for malignant melanoma (MM). We hypothesized that the hair shaft miR‐221 levels may be increased in patients with MM. We therefore assessed the possibility that hair shaft miR‐221 levels could be a marker for MM. The hair shaft miR‐221 levels were significantly higher in patients with MM than controls. The rates of increased hair shaft miR‐221 levels above the cut‐off value were comparable to those of serum 5‐S‐CD, which is a tumor marker commonly used for MM. Measurements of the hair shaft miR‐221 levels could have potential clinical value in the detection of MM. This is the first report investigating the hair shaft levels of an miRNA in patients with MM. Our investigations offer new insight into the relationship between miR‐221 and MM, and may provide a new, non‐invasive way to screen for melanoma.  相似文献   
3.
Micro-shear bond strength of dual-cured resin cement to glass ceramics.   总被引:4,自引:0,他引:4  
OBJECTIVES: The aim of this study was to investigate the effects of sandblasting, etching, and a silane coupling agent on the ability of dual-cured resin cement to bond to glass ceramics designed for in indirect adhesive restoration. METHODS: A cast glass ceramic (Olympus Castable Ceramics) with a crystalline phase consisting of mica and beta-spondumene was selected as the substrate material. The glass surfaces, which were sandblasted, polished, or etched with phosphoric acid or hydrofluoric acid (HF), were bonded with a dual-cured resin cement (Panavia Fluoro Cement) using a dentin adhesive system (Clearfil SE Bond), both with and without a silane coupling agent. A micro-shear bond test was carried out to measure the bond strength of the resin cement to the glass surface. Each glass surface was bonded and tested using the shear test. In addition, surfaces with the bonding removed after the shear bond test, the adhesive interface between the glass and cement, and an etched glass surface without any bonding, were studied morphologically using scanning electron microscopy or field emission scanning electron microscopy. RESULTS: Usage of a silane coupling agent effectively raised the bond-strength values of resin cement (Fisher's PLSD, P<0.01). The effectiveness of using phosphoric acid etching to improve bonding was not clear (Fisher's PLSD, P>0.01). HF-etching for 30s seemed to over-etch the glass surface, resulting in adverse effects on bonding (Fisher's PLSD, P<0.01). SIGNIFICANCE: The micro-shear bond strength between Olympus Castable Ceramics and resin cement can be increased by the silane coupling agent used along with an acidic primer.  相似文献   
4.
Effects of human recombinant TNF on the tumor blood vessels and on the thrombus formation were investigated in relation to its mode of antitumor action against Meth-A sarcoma transplanted in BALB/c mice. The extent of the blood vessel lesion was evaluated by using transparent chamber placed in the mouse skin. Bleeding, hyperemia and congestion were observed at 1-2h, 4-6h and 24h after TNF (1 X 10(4)U/mouse) administration, respectively. In contrast, no histological changes in the normal blood vessels were observed microscopically following TNF injection. Thrombus formation was evoked in the tumor vessels 4h after TNF injection. However, when thrombus formation was prevented by heparin, no difference was observed among antitumor action of TNF against Meth-A fibrosarcoma necrotic response and the rate of complete cure. These results suggest that the direct effects of TNF causing lesions in the tumor blood vessels plays an important role in its antitumor action.  相似文献   
5.
Renal cell carcinoma (RCC) causes many kinds of symptoms such as hypercalcemia, hypertension, polycythemia and fever. Here we describe a rare case of RCC presenting with a persistent cough. After radical nephrectomy, the obstinate cough disappeared. When the tumor recurred locally, the cough also recurred. Furthermore, the cough disappeared completely again after the removal of the recurrent tumor. Although all the clinical findings suggested that the RCC caused the cough, we could not identify a specific humoral substance responsible for the cough.  相似文献   
6.
A 75-year-old man had been admitted to another hospital because of left abdominal pain, and was given a diagnosis of left hydronephrosis and acute pancreatitis. After a JJ stent insertion and medication, he was transferred to our hospital for further examinations. US and EUS revealed a chronic pancreatitis-like pattern and multicystic lesion in the pancreas head and body. At that time enhanced CT findings showed an extrapancreatic low density area to be inflammatory change, extending from the pancreas body to the left crus of the diaphragm and posteriorly the spreading from the left crus of the diaphragm via the left urinary duct into the left iliopsoas muscle, in which MRI revealed partial high intensity. ERCP and MRCP showed focal irregular narrowing of the pancreatic duct of unknown cause, and we decided that an internal pancreatic fistula due to pancreatitis had induced left ureteral obstruction, caused by a protein plug or alcohol. Follow-up 6 months later showed that extrapancreatic spreading of the low density area had markedly regressed without any change in the ureteral obstruction.  相似文献   
7.
Elevation of plasma thioredoxin levels in HIV-infected individuals   总被引:3,自引:0,他引:3  
Thioredoxin (Trx), a ubiquitous protein intimately involvedin redox and protein disulfide reductions, has been shown tobe released from cells and to have cytokine-like activities.In addition, Trx has been implicated in the redox regulationof immunological responses and shown to be deficient in tissuesfrom AIDS patients. In studies presented here, plasma Trx levelswere measured by ELISA in plasma samples from HIV-infected individuals(n = 136) and HIV-negative controls (n = 47). To account forthe release of Trx into plasma due to hemolysis, the Trx measurementswere corrected according to the level of hemoglobin in the plasmasample. Data presented show that, in contrast to tissue Trxlevels, corrected plasma Trx levels are significantly higherin HIV-infected individuals than in controls (P < 0.0001).Furthermore, {small tilde}25% of the HIV-infected individualsstudied have plasma Trx levels greater than the highest levelfound in controls (37 ng/ml). Detailed multiparameter FACS analysisof peripheral blood mononuclear cells (PBMC) from the infectedindividuals demonstrates that those with higher plasma Trx levels(37 ng/ml or greater) tend to have lower overall CD4 counts.In addition, increases in plasma Trx levels correlate with decreasesin monochlorobimane staining (indicative of lower intracellularglutathione levels in PBMC) and with changes in surface antigenexpression (CD62L, CD38 and CD20) that occur in the later stagesof HIV infection. These correlations suggest that elevationof plasma Trx levels may be an important component of advancedHIV disease, perhaps related to the oxidative stress that oftenoccurs at this stage.  相似文献   
8.
The reductive retention of62Cu-PTSM was comparatively studied in the brain and Ehrlich ascites tumor cells by electron spin resonance spectrometry and nonradioactive Cu-PTSM. In the brain, only the mitochondrial fraction showed the ability to reduce Cu-PTSM, and the other subcellular fractions did not. In contrast, the cytosolic fraction of Ehrlich ascites tumor cells was the specific site of Cu-PTSM reduction. It was therefore considered that the retention of Cu-PTSM in the brain is closely related to mitochondrial reduction, most probably involving the mitochondrial electron transport system.  相似文献   
9.
Zhenxuanyin [symbol: see text] is composed of pure Chinese medicinal herbs, such as gastrodia tuber, poria cocos, ligusticum wallichii etc. 4-verssel occlusion (4VO) model rats were reperfused after 30 minutes' complete occlusion, and Zhenxuanyin was administered 3 times a day. 24 hours later, 123I-IMP uptake in the brain was evaluated as an index of cerebral blood flow (CBF). The results show that Zhenxuanyin (0.03 g/kg, 0.3 g/kg, 1 g/kg, or 3 g/kg a day) can greatly improve the blood flow in the main cerebral regions, and 0.3 g/kg can increase cerebral blood flow (CBF) to the normal level.  相似文献   
10.
Background To determine the effect of an adrenergic and a cholinergic antagonist on the diameter of the lumen of the nasolacrimal drainage system. Methods The asymptomatic side of 38 patients (29 women, nine men) with unilateral stenosis/obstruction of the nasolacrimal drainage system was studied. The tear meniscus height (TMH) of the asymptomatic side was normal, and the lacrimal drainage system was patent as revealed by dacryocystography. The nasolacrimal drainage system of the asymptomatic side was infused with 100 μl of 0.01% bunazosin hydrochloride, a selective α-1 adrenergic antagonist, or 100 μl of 0.4% tropicamide, a muscarinic and cholinergic antagonist. Dacryocystography was performed to determine the diameter of the lumen of the nasolacrimal drainage system before and after the antagonists. Results Bunazosin reduced the diameter of the lumen significantly, and the changes were more marked in the nasolacrimal duct (NLD), especially the middle and the lower regions. The diameter of the lumen of the lacrimal sac was not changed significantly. In contrast, tropicamide did not cause any significant change in the diameter of the lumen of the nasolacrimal drainage system. Conclusions The alterations of the size of the lumen of the nasolacrimal drainage system, especially the NLD, by an adrenergic antagonist suggest that the lumen diameter is under continuous sympathetic tone, and the parasympathetic tone is weak. This study has not received any financial support.  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