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   1596篇
  免费   199篇
  国内免费   28篇
耳鼻咽喉   7篇
儿科学   144篇
妇产科学   24篇
基础医学   204篇
口腔科学   90篇
临床医学   176篇
内科学   330篇
皮肤病学   50篇
神经病学   33篇
特种医学   173篇
外科学   241篇
综合类   39篇
一般理论   1篇
预防医学   116篇
眼科学   40篇
药学   60篇
中国医学   2篇
肿瘤学   93篇
  2023年   15篇
  2022年   10篇
  2021年   13篇
  2020年   14篇
  2019年   10篇
  2018年   47篇
  2017年   54篇
  2016年   48篇
  2015年   67篇
  2014年   89篇
  2013年   115篇
  2012年   49篇
  2011年   30篇
  2010年   83篇
  2009年   96篇
  2008年   33篇
  2007年   51篇
  2006年   52篇
  2005年   28篇
  2004年   30篇
  2003年   14篇
  2002年   19篇
  2001年   16篇
  2000年   9篇
  1999年   25篇
  1998年   105篇
  1997年   88篇
  1996年   98篇
  1995年   66篇
  1994年   75篇
  1993年   41篇
  1992年   17篇
  1991年   22篇
  1990年   15篇
  1989年   36篇
  1988年   30篇
  1987年   32篇
  1986年   30篇
  1985年   26篇
  1984年   13篇
  1983年   9篇
  1982年   20篇
  1981年   15篇
  1980年   16篇
  1979年   5篇
  1978年   6篇
  1977年   9篇
  1976年   13篇
  1975年   9篇
  1968年   2篇
排序方式: 共有1823条查询结果,搜索用时 15 毫秒
991.
A series of 2,4-disubstituted thiazole derivatives bearing N-n-butyl or N-cyclohexylthioureido synthon at position 2 and N-substituted thiosemicarbazone moiety at position 4 have been synthesized and tested for antitumor activity using the National Cancer Institute's in-vitro-disease-oriented antitumor screen. All of the tested compounds showed antineoplastic activity at concentrations less than 100 μM. Compounds 7, 9, 15 and 17 in particular showed activity with GI50 (mean-graph midpoint) of 17.8, 8.5, 9.5 and 7.4 μM, respectively. The detailed syntheses, spectroscopic and biological data are discussed.  相似文献   
992.
993.
OBJECTIVE: To determine if there is a dosage effect associated with the length of pulmonary rehabilitation (PR).
METHODS: We used a battery of outcome measures to quantify the amount of change that was achieved from baseline to discharge in 286 patients completing a PR program in 1 of 12 institutions participating in PROAS. The programs were of varying durations. Paired t-tests indicated overall that while the pulmonary rehabilitation programs did not yield improvements in physiologic (FEV1, FVC, % predicted FEV1) outcomes, the patients did achieve significant improvements in symptomatic (Borg score), functional (6-minute walk), general healthrelated quality of life [SF-36 Health Survey (SF-36)], and disease-specific HRQL [Chronic Respiratory Disease Questionnaire (CRQ) variables.
RESULTS: Based on a series of stepwise multiple regressions using the amount of change in each outcome variable as the dependent variable and adjusting for the corresponding baseline value and 11 clinical and sociodemographic characteristics, the number of hours of education (HREDU, 13.5 hr ± 6.7), activities of daily living (HRADL, 2.2 hr ± 6.6), and psychosocial support (6.5 hr ± 5.6) both individually and collectively (42.4 hr ± 11.8) generally did not contribute to explaining the magnitude of change achieved by the patients. However, the number of hours of supervised exercise (HREX, 25.4 hr ± 9.2) did contribute to explaining increases in 5 of the 8 SF-36 domains: physical function (p = 0.027), physical role (p = 0.0002), health perceptions (p = 0.0167), vitality (p = 0.034), and social function (p = 0.0035).
CONCLUSION: These data suggest that outcomes specifically related to pulmonary diseases are not affected by a longer duration for this type of intervention, but that broader, population-based assessments may need an additional period of intervention, or elapsed time, to detect improvement.  相似文献   
994.
Tendons: high-field-strength, surface coil MR imaging   总被引:8,自引:0,他引:8  
Beltran  J; Noto  AM; Herman  LJ; Lubbers  LM 《Radiology》1987,162(3):735-740
High-resolution magnetic resonance (MR) images of the tendons of the hands, wrists, feet, and ankles of six healthy volunteers and six cadavers were obtained using receive-only surface coils and reduced-field-of-view imaging. Normal anatomy was identified and compared with gross anatomic sections of the six cadavers. Experimentally produced tears of the calcaneal (Achilles) tendon in domestic swine were identified on MR images. The hands and feet of 11 patients were examined, and a variety of pathologic lesions were identified, including acute posttraumatic rupture, acute tenosynovitis, chronic tendonitis, and postsurgical complications. MR imaging provides inherently greater soft-tissue contrast than any other currently available imaging modality. With the use of surface coils and reduced-field-of-view imaging to enhance spatial resolution, MR imaging has become a valuable tool for imaging tendons. Advantages over other available modalities include excellent depiction of anatomic detail, superior contrast resolution, and the potential for multiplanar imaging.  相似文献   
995.
Background: Pancreas dissociation is a critical initial component of the islet isolation procedure and introduces high variability based on factors including the enzyme type, specificity and potency. Product refinement and alterations to the application strategies have improved isolation outcomes over time; however, islet utilization from donor organs remains low. In this study we evaluate a low endotoxin-high activity grade neutral protease in clinical islet isolation.

Materials and Methods: The use of a non-collagenolytic enzyme, either thermolysin or high active neutral protease, was randomized in clinical islet isolations to evaluate efficacy. Additionally a retrospective comparison to neutral protease NB was conducted.

Results:The thermolysin group had lower trapped islet population and increased purity and post-culture islet mass in comparison to high active grade neutral protease. Comparison of neutral protease NB GMP grade to high active neutral protease displayed no measurable difference in islet mass or viability and transplantation outcomes at 1 mo post-transplant were favorable for both groups.

Conclusions: High activity neutral protease can generate clinical grade islets and may prove beneficial to islet function and viability based on a reduced endotoxin load but dosing of neutral protease requires ongoing optimization.  相似文献   
996.
997.

Background

Chronic lung diseases such as asthma, COPD and pulmonary fibrosis are characterized by abnormal extracellular matrix (ECM) turnover. TGF-β is a key mediator stimulating ECM production by recruiting and activating lung fibroblasts and initiating their differentiation process into more active myofibroblasts. Glycogen synthase kinase-3 (GSK-3) regulates various intracellular signalling pathways; its role in TGF-β1-induced myofibroblast differentiation is currently largely unknown.

Purpose

To determine the contribution of GSK-3 signalling in TGF-β1-induced myofibroblast differentiation.

Experimental Approach

We used MRC5 human lung fibroblasts and primary pulmonary fibroblasts of individuals with and without COPD. Protein and mRNA expression were determined by immunoblotting and RT-PCR analysis respectively.

Results

Stimulation of MRC5 and primary human lung fibroblasts with TGF-β1 resulted in time- and dose-dependent increases of α-sm-actin and fibronectin expression, indicative of myofibroblast differentiation. Pharmacological inhibition of GSK-3 by SB216763 dose-dependently attenuated TGF-β1-induced expression of these myofibroblasts markers. Moreover, silencing of GSK-3 by siRNA or pharmacological inhibition by CT/CHIR99021 fully inhibited the TGF-β1-induced expression of α-sm-actin and fibronectin. The effect of GSK-3 inhibition on α-sm-actin expression was similar in fibroblasts from individuals with and without COPD. Neither smad, NF-κB nor ERK1/2 were involved in the inhibitory actions of GSK-3 inhibition by SB126763 on myofibroblast differentiation. Rather, SB216763 increased the phosphorylation of CREB, which in its phosphorylated form acts as a functional antagonist of TGF-β/smad signalling.

Conclusion and Implication

We demonstrate that GSK-3 signalling regulates TGF-β1-induced myofibroblast differentiation by regulating CREB phosphorylation. GSK-3 may constitute a useful target for treatment of chronic lung diseases.  相似文献   
998.
CD40‐soluble CD40 ligand (sCD40L) interactions might constitute an important mediator for vascular inflammation that initiates diabetic microangiopathy. Little is known about the relation between sCD40L and glycemic control. Therefore, this study aimed to evaluate sCD40L levels in patients with type 1 diabetes and its relation to microvascular complications and metabolic control. Sixty patients with type 1 diabetes were compared with 30 healthy control subjects. Detailed medical history, thorough clinical examination, and laboratory assessment of high‐sensitivity C‐reactive protein, glycemic control, and the presence of microvascular complications were performed. Measurement of serum sCD40L levels was done using enzyme‐linked immunosorbent assay. Patients were divided into two groups according to the presence of microvascular complications. Serum sCD40L levels were significantly elevated in patients with type 1 diabetes in both groups compared with healthy controls (p < 0.001). Patients with microvascular complications had higher serum sCD40L concentrations than non‐complicated cases (median, 13 000 vs. 450 pg/mL; p < 0.001). Serum sCD40L cutoff value of 530 pg/mL was able to differentiate complicated from non‐complicated cases (p < 0.001). Patients with microalbuminuria or peripheral neuropathy showed higher levels of sCD40L when compared with patients without these complications (p < 0.05). Serum sCD40L levels were positively correlated with hemoglobin A1c and urinary albumin excretion (p < 0.001). We suggest that serum sCD40L levels are elevated in type 1 diabetes, particularly in patients with microvascular complications and a significant correlation with glycemic control exists. Therefore, measurement of serum sCD40L levels in poorly controlled patients would help to identify those at high risk of developing microvascular complications.  相似文献   
999.
1000.
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