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   3229篇
  免费   179篇
  国内免费   55篇
耳鼻咽喉   110篇
儿科学   15篇
妇产科学   45篇
基础医学   648篇
口腔科学   58篇
临床医学   301篇
内科学   801篇
皮肤病学   82篇
神经病学   229篇
特种医学   121篇
外科学   271篇
综合类   13篇
现状与发展   1篇
预防医学   117篇
眼科学   38篇
药学   315篇
中国医学   53篇
肿瘤学   245篇
  2023年   10篇
  2022年   79篇
  2021年   119篇
  2020年   54篇
  2019年   79篇
  2018年   109篇
  2017年   67篇
  2016年   99篇
  2015年   136篇
  2014年   146篇
  2013年   191篇
  2012年   304篇
  2011年   298篇
  2010年   199篇
  2009年   150篇
  2008年   229篇
  2007年   186篇
  2006年   167篇
  2005年   152篇
  2004年   132篇
  2003年   117篇
  2002年   98篇
  2001年   95篇
  2000年   67篇
  1999年   47篇
  1998年   17篇
  1997年   12篇
  1996年   7篇
  1995年   4篇
  1994年   9篇
  1993年   3篇
  1992年   9篇
  1991年   11篇
  1990年   12篇
  1989年   5篇
  1988年   8篇
  1987年   5篇
  1986年   4篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1973年   7篇
  1972年   2篇
  1969年   3篇
  1968年   4篇
排序方式: 共有3463条查询结果,搜索用时 11 毫秒
41.
Small cell carcinoma is usually seen in the lung, but rarely involves the gastrointestinal tract including biliary tract. A 65 year-old man was admitted because of obstructive jaundice. A smooth-surfaced round intraluminal mass with proximal bile duct dilatation was seen in the proximal common bile duct on endoscopic retrograde cholangiogram. Under the diagnosis of bile duct cancer, pylorus-preserving pancreatoduodenectomy was done. Pathology revealed a 2 cm sized small cell carcinoma in the proximal common bile duct and distal common hepatic duct. On immunohistochemical stain, the tumor cells were positive for neuroendocrine markers CD56 and synaptophysin. After surgery, the patient received 5 cycles of adjuvant chemotherapy with VIP (etoposide, ifosfamide, and cisplatin) regimen. However, the patient died of liver metastasis 12 months after the diagnosis. We report a case of extrapulmonary small cell carcinoma arising from the common bile duct.  相似文献   
42.
ObjectiveInterlaminar cervical epidural steroid injections (ICESIs) are commonly used to treat axial neck pain and cervical radicular pain. However, local anesthetics can spread to and block the phrenic nerve and upper segments of the thoracic spinal cord where the sympathetic innervation of the lungs emerges. Therefore, changes in lung function may occur following ICESIs.MethodsThe primary outcome measure was the pulmonary function test (PFT) result 30 minutes before and after ICESI with ropivacaine (0.1875% or 0.25%). The secondary outcome measure was the comparison of the pain scores and functional disability between the two concentrations of ropivacaine 4 weeks after the ICESIs.ResultsFifty patients were randomly assigned to either the R1 (0.1875% ropivacaine) or R2 (0.25% ropivacaine) group. No significant difference was observed between the pre-ICESI and 30-minute post-ICESI PFT results within each group, and no difference was observed between the two groups. After 4 weeks of treatment, both groups showed a significant decrease in pain scores and functional disability; however, no significant differences were observed between the two groups.ConclusionsThis study showed no significant change in lung function after ICESIs in either group and no local anesthetic concentration-based difference in the clinical efficacy of the ICESIs.  相似文献   
43.
BACKGROUND/AIMS: During the natural course of hepatitis B virus (HBV) infection, the long-term clinical and histological outcomes following spontaneous hepatitis B surface antigen (HBsAg) seroclearance remain unclear. METHODS: Between 1984 and 2003, 49 (9.5%) out of 432 inactive HBsAg carriers had no detectable level of circulating HBsAg. Fifteen of 49 patients had undergone paired peritoneoscopic liver biopsies. RESULTS: During a mean follow-up period of 19.6 months after HBsAg seroclearance, 5 of 49 (10.2%) patients were noted to have HCC. Liver cirrhosis (P=0.040), a history of perinatal infection (P=0.005) and long-standing duration (at least 30 years) of HBsAg positivity (P=0.002) were associated with a significantly higher risk of developing HCC. Despite HBsAg seroclearance, HBV DNA was detected in the liver tissues from all 15 patients who underwent paired liver biopsies. Necroinflammation was significantly ameliorated (P<0.0001). On the other hand, amelioration of the fibrosis score did not reach a statistically significant level (P=0.072). Interestingly, aggravation of liver fibrosis was evident in 2 patients (13.3%) including one who had rapidly progressed to overt cirrhosis. CONCLUSIONS: In patients with spontaneous HBsAg seroclearance, necroinflammation was markedly improved and liver fibrosis was unchanged or regressed despite occult HBV infection. However, HCC developed in a minority of cases.  相似文献   
44.

Background

Fimasartan, a selective angiotensin II type 1 receptor blocker, was approved in Korea for the treatment of patients with mild to moderate hypertension.

Objective

The aim of this study was to evaluate the 24-hour blood pressure (BP) profiles before and after 8-week treatment with fimasartan and to compare them with those of valsartan.

Methods

A multicenter, randomized, double-blind, active-controlled, parallel-group study was conducted using ambulatory BP monitoring (ABPM). Korean patients with mild to moderate essential hypertension were enrolled and randomly received once-daily oral fimasartan 60 or 120 mg or valsartan 80 mg for 8 weeks. ABPM was performed before and after 8-week treatment, and clinic BP was also measured. Based on ABPM data, trough-to-peak ratio and smoothness index were derived. Tolerability was monitored throughout the study.

Results

Ninety-two patients were enrolled (mean [SD] age, 54.1 [8.2] years; weight, 67.9 [10.2] kg). After 8 weeks, 24-hour, daytime, and nighttime mean ambulatory systolic and diastolic BPs (SBP and DBP, respectively) were significantly decreased in all 3 treatment groups (range: SBP, –9.2 to –15.6 mm Hg; DBP, –5.0 to –10.7 mm Hg; P <0.0001–<0.05). The global trough-to-peak ratios of ambulatory DBP in the fimasartan groups were 0.74 (60 mg/d) and 0.81 (120 mg/d)—45.1% and 58.8% higher, respectively, than the ratio of 0.51 in the valsartan group. Fimasartan 60 mg/d was associated with 53.5% (SBP) and 68.3% (DBP) greater smoothness index scores compared with those with valsartan 80 mg/d (SBP, 1.52 vs. 0.99; DBP, 1.38 vs. 0.82). The decrease in clinic-measured DBP was significantly greater in the fimasartan 60-mg/d group compared with that in the valsartan 80-mg/d group (–14.0 vs –8.7 mm Hg; P = 0.0380). Fimasartan was well tolerated; headache was the most common adverse event.

Conclusion

Once-daily fimasartan effectively maintained a BP-reduction profile over the full 24-hour dosing interval; this profile was comparable to or slightly better than that of once-daily valsartan. Fimasartan was well tolerated; headache was the most common adverse event. ClinicalTrials.gov identifier: NCT00922441.  相似文献   
45.
We designed this study to assess the effectiveness of prealbumin as an indicator of growth as well as a nutritional marker in neonates.Between March 2017 and June 2019, we measured serum prealbumin concentrations of 80 neonates in neonatal intensive care unit at birth, postnatal day 14 and 28, and classified them into 3 groups (early preterm, late preterm, and term infants). And we examined correlation among prealbumin levels, nutritional intake, and anthropometric measurements (weight, length, and head circumference) in neonates.Prealbumin measured on the 14th postnatal day in early preterm infants showed significant correlations with the length, weight, and head circumference z-scores. Prealbumin levels increased with time in the late preterm and term groups. At birth, prealbumin levels were the lowest in late preterm babies, implying that they are nutritionally deficient and need nutritional support. At postnatal day 28, the prealbumin levels of many preterm infants did not reach those seen in term babies at birth, suggesting the presence of extrauterine growth restriction.Prealbumin can be considered as an indicator of sufficient growth in early preterm infants.  相似文献   
46.
Tetrahydrobiopterin (BH4) is an essential cofactor in NO synthesis by endothelial nitric oxide synthase (eNOS) enzymes. It has been previously suggested that reduced intrahepatic BH4 results in a decrease in intrahepatic NO and contributes to increased hepatic vascular resistance and portal pressure in animal models of cirrhosis. The main aim of the present study was to evaluate the relationship between BH4 and portal hypertension (PHT). One hundred ninety-three consecutive patients with chronic liver disease were included in the study. Liver biopsy, measurement of BH4 and hepatic venous pressure gradient (HVPG) were performed. Hepatic fibrosis was classified using the Laennec fibrosis scoring system. BH4 levels were determined in homogenized liver tissues of patients using a high performance liquid chromatography (HPLC) system. Statistical analysis was performed to evaluate the relationship between BH4 and HVPG, grade of hepatic fibrosis, clinical stage of cirrhosis, Child-Pugh class. A positive relationship between HVPG and hepatic fibrosis grade, clinical stage of cirrhosis and Child-Pugh class was observed. However, the BH4 level showed no significant correlation with HVPG or clinical features of cirrhosis. BH4 concentration in liver tissue has little relation to the severity of portal hypertension in patients with chronic liver disease.

Graphical Abstract

相似文献   
47.
Structural reorganization in white matter (WM) after stroke is a potential contributor to substitute or to newly establish the functional field on the injured brain in nature. Diffusion tensor imaging (DTI) is an imaging modality that can be used to evaluate damage and recovery within the brain. This method of imaging allows for in vivo assessment of the restricted movements of water molecules in WM and provides a detailed look at structural connectivity in the brain. For longitudinal DTI studies after a stroke, the conventional region of interest method and voxel‐based analysis are highly dependent on the user‐hypothesis and parameter settings for implementation. In contrast, tract‐based spatial statistics (TBSS) allows for reliable voxel‐wise analysis via the projection of diffusion‐derived parameters onto an alignment‐invariant WM skeleton. In this study, spatiotemporal WM changes were examined with DTI‐derived parameters (fractional anisotropy, FA; mean diffusivity, MD; axial diffusivity, DA; radial diffusivity, RD) using TBSS 2 h to 6 weeks after experimental focal ischemic stroke in rats (N = 6). FA values remained unchanged 2–4 h after the stroke, followed by a continuous decrease in the ipsilesional hemisphere from 24 h to 2 weeks post‐stroke and gradual recovery from the ipsilesional corpus callosum to the external capsule until 6 weeks post‐stroke. In particular, the fibers in these areas were extended toward the striatum of the ischemic boundary region at 6 weeks on tractography. The alterations of the other parameters in the ipsilesional hemisphere showed patterns of a decrease at the early stage, a subsequent pseudo‐normalization of MD and DA, a rapid reduction of RD, and a progressive increase in MD, DA and RD with a decreased extent in the injured area at later stages. The findings of this study may reflect the ongoing processes on tissue damage and spontaneous recovery after stroke.  相似文献   
48.
Combined radiotherapy and chemotherapy have represented major advance in the therapeutic management of cancer therapy. Anthracycline antineoplastic agents are limited by a high incidence of severe and usually irreversible cardiac toxicity, the cause of which remains controversial. When the primary cardiomyocytes isolated from neonatal rats were preirradiated by γ-ray, the cells were highly resistant to adriamycin-induced apoptosis. This study shows that irradiation inhibited apoptosis by enhancing Bcl-2, attenuating Bax induction, and preventing collapse of mitochondrial membrane potential (ΔΨ), cytochrome c release into cytoplasm and caspase-3, -6 and -9 activations.

In addition, the preirradiation stimulated the activity of manganese-superoxide dismutase (Mn-SOD) and the expression of Mn-SOD mRNA and protein. Adriamycin decreased Mn-SOD activity but did not change the activity of copper/zinc (Cu/Zn)-SOD under either pre- or nonirradiated condition. Phosphothioate-linked antisense against Mn-SOD, which specifically knocked down the activity of Mn-SOD but not that of Cu/Zn-SOD, reversed irradiation-induced protective effect in adriamycin-exposed cardiomyocytes. These data suggest that the irradiation-induced expression of Mn-SOD plays an important role in irradiation-mediated protection in adriamycin-exposed rat ventricular cardiomyocytes.  相似文献   
49.
Pulmonary damage by Vibrio vulnificus cytolysin.   总被引:6,自引:0,他引:6       下载免费PDF全文
Vibrio vulnificus is an estuarine bacterium that causes septicemia and serious wound infection. Cytolysin produced by V. vulnificus has been incriminated as one of the important virulence determinants of bacterial infection. Cytolysin (8 hemolytic units) given intravenously to mice via their tail veins caused severe hemoconcentration and lethality. Cytolysin treatment greatly increased pulmonary wet weight and vascular permeability as measured by (125)I-labeled albumin leakage without affecting those factors of other organs significantly. Blood neutrophils were markedly decreased in number after cytolysin injection, with a concomitant increase in the level of pulmonary myeloperoxidase activity, indicating that cytolysin-induced neutropenia might be due to pulmonary sequestration of neutrophils. By microscopic examination, severe perivascular edema and neutrophil infiltration were evident in lung tissues. These results suggest that increased vascular permeability and neutrophil sequestration in the lungs are important factors in lethal activity by cytolysin.  相似文献   
50.
Kattel K  Park JY  Xu W  Kim HG  Lee EJ  Bony BA  Heo WC  Jin S  Baeck JS  Chang Y  Kim TJ  Bae JE  Chae KS  Lee GH 《Biomaterials》2012,33(11):3254-3261
We report here paramagnetic dysprosium nanomaterial-based T(2) MRI contrast agents. A large r(2) and a negligible r(1) is an ideal condition for T(2) MR imaging. At this condition, protons are strongly and nearly exclusively induced for T(2) MR imaging. The dysprosium nanomaterials fairly satisfy this because they are found to possess a decent r(2) but a negligible r(1) arising from L + S state 4f-electrons in Dy(III) ion ((6)H(15/2)). Their r(2) will also further increase with increasing applied field because of unsaturated magnetization at room temperature. Therefore, MR imaging and various physical properties of the synthesized d-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles (d(avg) = 3.2 nm) and dysprosium hydroxide nanorods (20 × 300 nm) are investigated. These include hydrodynamic diameters, magnetic properties, MR relaxivities, cytotoxicities, and 3 tesla in vivo T(2) MR images. Here, MR imaging properties of dysprosium hydroxide nanorods have not been reported so far. These two samples show r(2)s of 65.04 and 181.57 s(-1)mM(-1), respectively, with negligible r(1)s at 1.5 tesla and at room temperature, no in vitro cytotoxicity up to 100 μM Dy, and clear negative contrast enhancements in 3 tesla in vivo T(2) MR images of a mouse liver, which will be even more improved at higher MR fields. Therefore, d-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles with renal excretion can be a potential candidate as a sensitive T(2) MRI contrast agent at MR field greater than 3 tesla.  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