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   3255篇
  免费   346篇
  国内免费   60篇
耳鼻咽喉   112篇
儿科学   83篇
妇产科学   56篇
基础医学   409篇
口腔科学   59篇
临床医学   298篇
内科学   564篇
皮肤病学   68篇
神经病学   314篇
特种医学   205篇
外科学   383篇
综合类   69篇
预防医学   115篇
眼科学   60篇
药学   338篇
中国医学   47篇
肿瘤学   481篇
  2023年   11篇
  2022年   35篇
  2021年   61篇
  2020年   48篇
  2019年   117篇
  2018年   107篇
  2017年   105篇
  2016年   116篇
  2015年   112篇
  2014年   151篇
  2013年   170篇
  2012年   206篇
  2011年   195篇
  2010年   134篇
  2009年   127篇
  2008年   189篇
  2007年   207篇
  2006年   168篇
  2005年   179篇
  2004年   137篇
  2003年   139篇
  2002年   126篇
  2001年   78篇
  2000年   78篇
  1999年   70篇
  1998年   51篇
  1997年   49篇
  1996年   44篇
  1995年   36篇
  1994年   25篇
  1993年   28篇
  1992年   31篇
  1991年   28篇
  1990年   27篇
  1989年   33篇
  1988年   27篇
  1987年   24篇
  1986年   24篇
  1985年   22篇
  1984年   17篇
  1983年   12篇
  1982年   19篇
  1981年   13篇
  1980年   9篇
  1979年   9篇
  1977年   11篇
  1976年   13篇
  1975年   6篇
  1974年   5篇
  1973年   5篇
排序方式: 共有3661条查询结果,搜索用时 15 毫秒
61.
62.
The potential use of urinary nucleic acids as diagnostic markers in prostate cancer (PCa) was evaluated. Ninety-five urine samples and 234 prostate tissue samples from patients with PCa and benign prostatic hyperplasia (BPH) were analyzed. Micro-array analysis was used to identify candidate genes, which were verified by the two-gene expression ratio and validated in tissue mRNA and urinary nucleic acid cohorts. Real-time quantitative polymerase chain reaction (qPCR) was used to measure urinary nucleic acid levels and tissue mRNA expression. The TSPAN13-to-S100A9 ratio was selected to determine the diagnostic value of urinary nucleic acids in PCa (P = 0.037) and shown to be significantly higher in PCa than in BPH in the mRNA and nucleic acid cohort analyses (P < 0.001 and P = 0.013, respectively). Receiver operating characteristic (ROC) analysis showed that the area under the ROC curve was 0.898 and 0.676 in tissue mRNA cohort and urinary nucleic acid cohort, respectively. The TSPAN13-to-S100A9 ratio showed a strong potential as a diagnostic marker for PCa. The present results suggest that the analysis of urine supernatant can be used as a simple diagnostic method for PCa that can be adapted to the clinical setting in the future.  相似文献   
63.
64.
Background : How tissue patterns form in development and regeneration is a fundamental issue remaining to be fully understood. The integument often forms repetitive units in space (periodic patterning) and time (cyclic renewal), such as feathers and hairs. Integument patterns are visible and experimentally manipulatable, helping us reveal pattern formative processes. Variability is seen in regional phenotypic specificities and temporal cycling at different physiological stages. Results: Here we show some cellular/molecular bases revealed by analyzing integument patterns. (1) Localized cellular activity (proliferation, rearrangement, apoptosis, differentiation) transforms prototypic organ primordia into specific shapes. Combinatorial positioning of different localized activity zones generates diverse and complex organ forms. (2) Competitive equilibrium between activators and inhibitors regulates stem cells through cyclic quiescence and activation. Conclusions: Dynamic interactions between stem cells and their adjacent niche regulate regenerative behavior, modulated by multi‐layers of macro‐environmental factors (dermis, body hormone status, and external environment). Genomics studies may reveal how positional information of localized cellular activity is stored. In vivo skin imaging and lineage tracing unveils new insights into stem cell plasticity. Principles of self‐assembly obtained from the integumentary organ model can be applied to help restore damaged patterns during regenerative wound healing and for tissue engineering to rebuild tissues. Developmental Dynamics 244:905–920, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
65.

Background

Ultrasound guidance is increasingly being used for neurolytic procedures that have traditionally been done with electrical stimulation (e-stim) guidance alone. Ultrasound visualization with e-stim?guided neurolysis can potentially allow adjustments in injection protocols that will reduce the volume of neurolytic agent needed to achieve clinical improvement.

Objective

This study compared e-stim only to e-stim with ultrasound guidance in phenol neurolysis of the musculocutaneous nerve (MCN) for elbow flexor spasticity. We also evaluated the ultrasound appearance of the MCN in this population.

Design

Retrospective review.

Setting

University hospital outpatient clinic.

Participants

Adults (N = 167) receiving phenol neurolysis to the MCN for treatment of elbow flexor spasticity between 1997 and 2014 and adult control subjects.

Methods

For each phenol injection of the MCN, the method of guidance, volume of phenol injected, technical success, improved range of motion at the elbow postinjection, adverse effects, reason for termination of injections, and details of concomitant botulinum toxin injection were recorded. The ultrasound appearance of the MCN, including nerve cross-sectional area and shape, were recorded and compared between groups.

Main Outcome Measures

The volume of phenol injected and MCN cross-sectional area and shape as demonstrated by ultrasound.

Results

The addition of ultrasound to e-stim?guided phenol neurolysis was associated with lower doses of phenol when compared to e-stim guidance alone (2.31 mL versus 3.69 mL, P < .001). With subsequent injections, the dose of phenol increased with e-stim guidance (P < .001), but not with e-stim and ultrasound guidance (P = .95). Both methods of guidance had high technical success, improved ROM at elbow postinjection, and low rates of adverse events. In comparing the ultrasound appearance of the MCN in patients with spasticity to that of normal controls, there was no difference in the cross-sectional area of the nerve, but there was more variability in shape.

Conclusions

Combined e-stim and ultrasound guidance during phenol neurolysis to the MCN allows a smaller volume of phenol to be used for equal effect, both at initial and repeat injection. The MCN shape was more variable in individuals with spasticity; this should be recognized so as to successfully locate the nerve to perform neurolysis.

Level of Evidence

IV  相似文献   
66.
67.

Background

Atrial fibrillation (AF) is the most common sustained arrhythmia, and pulmonary veins (PVs) play a critical role in triggering AF. Angiotensin (Ang)‐(1‐7) regulates calcium (Ca2+) homoeostasis and also plays a critical role in cardiovascular pathophysiology. However, the role of Ang‐(1‐7) in PV arrhythmogenesis remains unclear.

Materials and methods

Conventional microelectrodes, whole‐cell patch‐clamp and the fluo‐3 fluorimetric ratio technique were used to record ionic currents and intracellular Ca2+ in isolated rabbit PV preparations and in single isolated PV cardiomyocytes, before and after administration of Ang‐(1‐7).

Results

Ang (1‐7) concentration dependently (0.1, 1, 10 and 100 nmol/L) decreased PV spontaneous electrical activity. Ang‐(1‐7) (100 nmol/L) decreased the late sodium (Na+), L‐type Ca2+ and Na+‐Ca2+ exchanger currents, but did not affect the voltage‐dependent Na+ current in PV cardiomyocytes. In addition, Ang‐(1‐7) decreased intracellular Ca2+ transient and sarcoplasmic reticulum Ca2+ content in PV cardiomyocytes. A779 (a Mas receptor blocker, 3 μmol/L), L‐NAME (a NO synthesis inhibitor, 100 μmol/L) or wortmannin (a specific PI3K inhibitor, 10 nmol/L) attenuated the effects of Ang‐(1‐7) (100 nmol/L) on PV spontaneous electric activity.

Conclusion

Ang‐(1‐7) regulates PV electrophysiological characteristics and Ca2+ homoeostasis via Mas/PI3K/eNOS signalling pathway.  相似文献   
68.
We herein demonstrate n-i-p-type planar heterojunction perovskite solar cells employing spin-coated ZnO nanoparticles modified with various alkali metal carbonates including Li2CO3, Na2CO3, K2CO3 and Cs2CO3, which can tune the energy band structure of ZnO ETLs. Since these metal carbonates doped on ZnO ETLs lead to deeper conduction bands in the ZnO ETLs, electrons are easily transported from the perovskite active layer to the cathode electrode. The power conversion efficiency of about 27% is improved due to the incorporation of alkali carbonates in ETLs. As alternatives to TiO2 and n-type metal oxides, electron transport materials consisting of doped ZnO nanoparticles are viable ETLs for efficient n-i-p planar heterojunction solar cells, and they can be used on flexible substrates via roll-to-roll processing.

Planar formamidinium perovskite solar cells have been fabricated with an alkali carbonate-doped zinc oxide layer.  相似文献   
69.
70.
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