全文获取类型
收费全文 | 390083篇 |
免费 | 21209篇 |
国内免费 | 15469篇 |
专业分类
耳鼻咽喉 | 3006篇 |
儿科学 | 8713篇 |
妇产科学 | 5923篇 |
基础医学 | 42324篇 |
口腔科学 | 5204篇 |
临床医学 | 42879篇 |
内科学 | 62946篇 |
皮肤病学 | 2857篇 |
神经病学 | 28334篇 |
特种医学 | 17017篇 |
外国民族医学 | 138篇 |
外科学 | 49958篇 |
综合类 | 37357篇 |
现状与发展 | 55篇 |
一般理论 | 19篇 |
预防医学 | 30892篇 |
眼科学 | 9390篇 |
药学 | 31833篇 |
195篇 | |
中国医学 | 12868篇 |
肿瘤学 | 34853篇 |
出版年
2024年 | 694篇 |
2023年 | 3561篇 |
2022年 | 9206篇 |
2021年 | 11542篇 |
2020年 | 8602篇 |
2019年 | 7552篇 |
2018年 | 29187篇 |
2017年 | 23898篇 |
2016年 | 25568篇 |
2015年 | 11106篇 |
2014年 | 13316篇 |
2013年 | 11406篇 |
2012年 | 22711篇 |
2011年 | 38349篇 |
2010年 | 28842篇 |
2009年 | 19416篇 |
2008年 | 30224篇 |
2007年 | 32410篇 |
2006年 | 11676篇 |
2005年 | 13394篇 |
2004年 | 10223篇 |
2003年 | 10808篇 |
2002年 | 7891篇 |
2001年 | 5189篇 |
2000年 | 5741篇 |
1999年 | 5836篇 |
1998年 | 3718篇 |
1997年 | 3693篇 |
1996年 | 2896篇 |
1995年 | 2704篇 |
1994年 | 2236篇 |
1993年 | 1432篇 |
1992年 | 1926篇 |
1991年 | 1677篇 |
1990年 | 1411篇 |
1989年 | 1164篇 |
1988年 | 1064篇 |
1987年 | 927篇 |
1986年 | 747篇 |
1985年 | 553篇 |
1984年 | 354篇 |
1983年 | 261篇 |
1982年 | 173篇 |
1981年 | 145篇 |
1980年 | 150篇 |
1979年 | 144篇 |
1975年 | 62篇 |
1974年 | 75篇 |
1938年 | 64篇 |
1932年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Seyed Mehdi BagheriMofidi Majid Pouladian Seyed Behnamedin Jameie Ali Abbaspour Tehrani-Fard 《Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine》2016,39(3):717-726
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation. 相似文献
3.
4.
5.
Shasha Yuan Fang Wang Yan Zhao Yun Liu 《The International journal of health planning and management》2020,35(1):e196-e209
Since the new round of health care reform in 2009, the vertical integration of hospitals and primary health institutions has become widely implemented in China as an efficient method for improving quality of primary care. This study aimed to answer the following questions: (a) What is the perceived quality of township health centres (THCs) under integration? (B) What differences could be observed among the three typical integration models, namely, private hospital-THC integration, public hospital-THC integration, and loose collaboration? Two rounds of cross-sectional surveys were conducted from November 2016 to June 2018. The Chinese version of the Primary Care Assessment Tool was used to evaluate perceived quality of sample THCs, and 1118 adult patients were interviewed in total. Multiple linear regressions were employed to compare the quality scores between two survey rounds and among different integration models after controlling for potential confounders. The results revealed that the quality of care significantly improved under private hospital-THC integration as observed by comparing two survey rounds, while no change or slight changes were observed in the other two models. The difference observed among the three models was that the perceived quality of THCs integrated with private hospitals was worse than that of THCs integrated with public hospitals and THCs under loose collaboration, while no significant difference was observed between public hospital-THC integration and loose collaboration. Increased attention should be given to highlighting the tight integration between hospitals and THCs and the different roles played by private and public hospitals in the current reform. 相似文献
6.
Unconditional Positivity-Preserving and Energy Stable Schemes for a Reduced Poisson-Nernst-Planck System 下载免费PDF全文
Hailiang Liu & Wumaier Maimaitiyiming 《Communications In Computational Physics》2020,27(5):1505-1529
The Poisson-Nernst-Planck (PNP) system is a widely accepted model for
simulation of ionic channels. In this paper, we design, analyze, and numerically validate a second order unconditional positivity-preserving scheme for solving a reduced
PNP system, which can well approximate the three dimensional ion channel problem.
Positivity of numerical solutions is proven to hold true independent of the size of time
steps and the choice of the Poisson solver. The scheme is easy to implement without
resorting to any iteration method. Several numerical examples further confirm the
positivity-preserving property, and demonstrate the accuracy, efficiency, and robustness of the proposed scheme, as well as the fast approach to steady states. 相似文献
7.
Jianhui Su Chaoyang Ma Chengxiang Liu Chuanzhong Gao Rongjing Nie 《International journal of food sciences and nutrition》2016,67(1):20-28
This study investigated the hypocholesterolaemic effects of bitter melon aqueous extracts (BMAE) in vitro, the inhibitory effects of BMAE on pancreatic cholesterol esterase (CEase) and incorporation of cholesterol into micelles were investigated. BMAE decreased the in vitro micellar solubility of cholesterol in a dose-dependent manner. The conformation of CEase was investigated by means of circular dichroism (CD) and fluorescence. The result revealed the decrease of α-helix contents, increase of β-sheet and exposure of aromatic amino acid residuals. The incorporation of cholesterol into micelles was inhibited by BMAE. A complex was observed by transmission electron microscopy (TEM), which indicated interaction between cholesterol and BMAE. The result revealed that BMAE can play a role in decreased intestinal cholesterol absorption via inhibition of CEase, and of micelle formation. 相似文献
8.
9.
10.