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   10654篇
  免费   33篇
  国内免费   9篇
耳鼻咽喉   64篇
儿科学   231篇
妇产科学   276篇
基础医学   1239篇
口腔科学   396篇
临床医学   905篇
内科学   1498篇
皮肤病学   179篇
神经病学   1267篇
特种医学   236篇
外科学   795篇
综合类   79篇
预防医学   682篇
眼科学   138篇
药学   1644篇
中国医学   27篇
肿瘤学   1040篇
  2024年   62篇
  2023年   791篇
  2022年   519篇
  2021年   826篇
  2020年   996篇
  2019年   1064篇
  2018年   1088篇
  2017年   718篇
  2016年   497篇
  2015年   423篇
  2014年   943篇
  2013年   1824篇
  2012年   231篇
  2011年   64篇
  2010年   80篇
  2009年   42篇
  2008年   35篇
  2007年   43篇
  2006年   15篇
  2005年   58篇
  2004年   35篇
  2003年   18篇
  2002年   13篇
  2001年   27篇
  2000年   20篇
  1999年   17篇
  1998年   10篇
  1997年   3篇
  1996年   3篇
  1995年   1篇
  1994年   5篇
  1993年   1篇
  1992年   3篇
  1990年   2篇
  1987年   1篇
  1985年   33篇
  1984年   36篇
  1983年   26篇
  1982年   29篇
  1981年   22篇
  1980年   17篇
  1979年   14篇
  1978年   10篇
  1977年   4篇
  1976年   10篇
  1975年   7篇
  1974年   8篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
Effective therapy lies in achieving a therapeutic amount of drug to the proper site in the body and then maintaining the desired drug concentration for a sufficient time interval to be clinically effective for treatment. The blood–brain barrier (BBB) hinders most drugs from entering the central nervous system (CNS) from the blood stream, leading to the difficulty of delivering drugs to the brain via the circulatory system for the treatment, diagnosis and prevention of brain diseases. Several brain drug delivery approaches have been developed, such as intracerebral and intracerebroventricular administration, intranasal delivery and blood-to-brain delivery, as a result of transient BBB disruption induced by biological, chemical or physical stimuli such as zonula occludens toxin, mannitol, magnetic heating and ultrasound, but these approaches showed disadvantages of being dangerous, high cost and unsuitability for most brain diseases and drugs. The strategy of vector-mediated blood-to-brain delivery, which involves improving BBB permeability of the drug–carrier conjugate, can minimize side effects, such as being submicrometre objects that behave as a whole unit in terms of their transport and properties, nanomaterials, are promising carrier vehicles for direct drug transport across the intact BBB as a result of their potential to enter the brain capillary endothelial cells by means of normal endocytosis and transcytosis due to their small size, as well as their possibility of being functionalized with multiple copies of the drug molecule of interest. This review provids a concise discussion of nano carriers for drug transport across the intact BBB, various forms of nanomaterials including inorganic/solid lipid/polymeric nanoparticles, nanoemulsions, quantum dots, nanogels, liposomes, micelles, dendrimers, polymersomes and exosomes are critically evaluated, their mechanisms for drug transport across the BBB are reviewed, and the future directions of this area are fully discussed.  相似文献   
33.
Polymeric micelles have been widely explored preclinically as suitable delivery systems for poorly soluble chemotherapeutic drugs in cancer therapy. The present study reported the development of cholesterol (Ch)-conjugated poly(D,L-Lactide) (PLA)-based polymeric micelles (mPEG–PLA-Ch) for effective encapsulation and delivery of curcumin (CUR) at the tumor site. Cholesterol conjugation dramatically affected the particle size and improved drug loading (DL) and encapsulation efficiency (EE). mPEG–PLA-Ch-CUR showed bigger hydrodynamic diameter (104.6?±?2.1?nm, and 169.3?±?1.52?nm for mPEG–PLA and mPEG–PLA-Ch, respectively) due to increased size of the hydrophobic core. The newly developed polymer exhibited low critical micelles concentration (CMC) (25?μg/mL) which is close to lipid-based polymer, PEG-phosphatidyl ethanolamine (12.5?μg/mL) compared to mPEG–PLA (50?μg/mL). mPEG–PLA-Ch micelles exhibited relatively higher EE (93.74?±?1.6%) and DL (11.86?±?0.8%) compared to mPEG–PLA micelles (EE 91.89?±?1.2% and DL 11.06?±?0.8%). mPEG–PLA-Ch micelles were internalized by the cancer cells effectively and exhibited higher cytotoxicity compared to free CUR in both, murine melanoma (B16F10) and human breast cancer (MDA-MB-231) cells. mPEG–PLA-Ch exhibited satisfactory hemocompatibility indicating their potential for systemic application. Further, mPEG–PLA-Ch-CUR demonstrated higher rate of reduction of tumor volume in B16F10-xenografted tumor-bearing mice compared to free CUR. At the end of 22 days, the tumor reduced to 1.87-fold (627.72?±?0.9?mm3 versus 1174.68?±?1.64?mm3) compared to the treatment with free CUR. In conclusion, the experimental data in vitro and in vivo indicated that the newly developed CUR-mPEG–PLA-Ch micelles may have promising applications in solid tumors.  相似文献   
34.
The mulberry tree (Morus alba) plays a key role in agriculture, and its different parts have been used as popular Traditional Chinese Medicines for thousands of years. There are 16 species belonging to the Morus genus. Among them, 11 species distribute in China, most of which have been used as the substitutes of M. alba in local provinces. This review summarizes the structural characters of polyphenols, the main components in Morus, including Diels–Alder-type adducts, flavonoids, 2-arylbenzofurans, and stilbenes, and also their related bioactivities in the last 10 years.  相似文献   
35.
《Drug discovery today》2022,27(5):1350-1366
The screening of compound–protein interactions (CPIs) is one of the most crucial steps in finding hit and lead compounds. Deep learning (DL) methods for CPI prediction can address intrinsic limitations of traditional HTS and virtual screening with the advantage of low cost and high efficiency. This review provides a comprehensive survey of DL-based CPI prediction. It first summarizes popular databases of small-molecule compounds, proteins and binding complexes. Then, it outlines classical representations of compounds and proteins in turn. After that, this review briefly introduces state-of-the-art DL-based models in terms of design paradigms and investigates their prediction performance. Finally, it indicates current challenges and trends toward better CPI prediction and sketches out crucial approaches toward practical applications.  相似文献   
36.
Context We report the first ever chemical/biochemical study on Crocus mathewii Kerndorff (Iridaceae) – a Turkish endemic angiosperm. This plant has never been explored for its phytochemistry and bioactivities.

Objective This study explores C. mathewii corm and aerial parts for the chemical and biological properties of hexane, ethyl acetate, methanol and water fractions of the extracts.

Material and methods Plant material (20 g) was extracted by methanol (250?mL?×?5, 3 days each) and fractioned into hexane, ethyl acetate, methanol and water. All fractions were subjected to β-carotene–linoleic acid, DPPH·, ABTS·+, CUPRAC, metal chelating and tyrosinase inhibition activities. Hexane fractions were submitted to GC–MS analysis.

Results Ethyl acetate fractions showed excellent IC50 values in DPPH· (aerial 36.21?±?0.76 and corm 33.87?±?0.02?mg/L) and ABTS·+ (aerial 33.01?±?0.79 and bulb 27.87?±?0.33?mg/L); higher than the IC50 of the standard α-tocopherol (DPPH 116.25?±?1.97; ABTS 52.64?±?0.37?mg/L), higher than BHA in DPPH (57.31?±?0.25?mg/L), but slightly lower in ABTS (19.86?±?2.73?mg/L). Methanol extract of aerial parts also showed higher activity than α-tocopherol in DPPH (85.56?±?11.51?mg/L) but slightly less (72.90?±?3.66?mg/L) than both the standards in ABTS. Linoleic (aerial 53.9%, corm 43.9%) and palmitic (aerial 22.2%, corm 18%) were found as the major fatty acids.

Discussion and conclusion Some fractions of C. mathewii showed higher antioxidant activities than the standards. There is a need to explore more about this plant.  相似文献   
37.
38.

Purpose

Transient elastography (TE) is routinely used for noninvasive staging of hepatic fibrosis. The objective of the present study was to investigate the role of TE (FibroScan) in determining changes in liver congestion in patients with Budd–Chiari syndrome (BCS) treated by endovascular interventions and determine the effects of pretreatment Meta-analysis of Histological Data in Viral Hepatitis (METAVIR) fibrosis score on posttreatment liver stiffness (LS).

Materials and Methods

Twenty-five patients undergoing endovascular procedures for treatment of BCS underwent TE immediately before and within 24 hours after the procedure. Fifteen patients available for 3-month follow-up were again subjected to TE. Mean LS values before and after intervention were compared in 12 of these patients for whom METAVIR scores were available. Pressure gradient changes across the stenosed hepatic veins/inferior vena cava were measured during the procedure. Statistical analysis of these data was performed by Wilcoxon signed-rank test, Mann–Whitney U test, and Pearson product–moment correlation coefficient.

Results

Significant differences were found between mean LS measurements before and within 24 hours after intervention (Z-score = 4.372) and between the mean values obtained before and 3 months after treatment (Z-score = 3.408). Mean changes in LS values after intervention in patients with METAVIR fibrosis scores ≤ 2 and > 2 were not significant. There was no correlation between changes in pressure gradients and the degree of LS.

Conclusions

TE is a useful tool to assess the reduction in hepatic congestion in patients with BCS undergoing endovascular interventions.  相似文献   
39.
Backgrounds: Defect in kidney is one major reason of hypertension. The study aimed ao uncovering the regulatory mechanisms of miRNAs and the targets in hypertensive kidney.

Methods: Gene expression profile of GSE28345 and miRNA expression profile of GSE28283 were downloaded from GEO database. After data preprocessing, differently expressed genes (DEGs) and miRNAs (DE-miRs) were identified using limma package. Then targets of miRNAs were predicted according to information in relevant databases. Function and pathway enrichment analyses were performed for DEGs using DAVID software. Furthermore, protein–protein interaction (PPI) networks were constructed for up- and down-regulated genes, respectively, using the Cytoscape. Additionally, for down-regulated DEGs, the integrated regulatory network was established combining PPI network with the miRNA–mRNA interactions.

Results: As a result, 285 DEGs were identified, including 177 up-regulated and 108 down-regulated genes. Combined with the predicted targets of miRNAs, 22 up-regulated DE-miRs were identified. In the integrated network for down-regulated DEGs, three crucial nodes were identified as ASPN, COL12A1, and SCN2A. ASPN was predicted as target of miR-21 and miR-374b, and COL12A1 was the target of miR-30e, miR-21, and miR-195, while SCN2A was the target of miR-30e, miR-374b, and miR-195. Notably, COL12A1 and ASPN were linked with each other in the network.

Conclusion: Three crucial genes were identified in hypertensive kidney, such as COL12A1, ASPN, and SCN2A. ASPN might co-function with COL12A1, and they both might be the targets of miR-21. SCN2A might be a novel target of miR-30e and miR-374b. However, more experiments are needed to validate these results.  相似文献   

40.

Objective

To determine conditional recurrence-free survival (RFS) and progression-free survival (PFS) and improve decision-making toward surveillance protocols and scheduling. Furthermore, evaluating the evolution of predictors for disease recurrence over time, because TaG1 non–muscle-invasive bladder cancer harbors a risk of disease recurrence and progression.

Material and methods

The retrospective multicenter design study includes 1,245 TaG1 bladder cancer patients with median follow-up of 62.7 (interquartile range: 34.3–91.1) months. Conditional RFS and PFS estimates were calculated using the Kaplan-Meier method. Multivariable Cox regression model was calculated proportional for the prediction of recurrence and progression (covariables: age, tumor size, multiple tumors, prior recurrence, and immediate postoperative instillation of chemotherapy).

Results

After 3 months without event, the conditional RFS and PFS (to ≥pT2) rates for 5 additional years without event were 57.5% and 93.4%, respectively. Given a 1-, 2-, 3-, and 5-year survival, the conditional RFS rates for 5 additional years without event improved by +9.8 (67.3%), +5.2 (72.5%), +6.5 (79.0%), +2.0 (81.0%), and +1.0% (82.0%), respectively. In contrast, the 5-year conditional PFS rates were more or less stable with 94.3% after 1 year to 94.1% after 5 years. Multivariable analyses showed decreasing impact of risk parameters on RFS estimates over time. Based on these findings, we suggest a risk stratification to individualize follow-up for intermediate risk TaG1. Main limitation was the retrospective design.

Conclusions

Conditional-survival analyses demonstrates that the patient risk profile changes over time. RFS rates rise with increasing survival whereas PFS rates were stable. The impact of prognostic features decreases over time. Our findings can be used for patient counseling and planning of personalized follow-up.  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