全文获取类型
收费全文 | 5993篇 |
免费 | 698篇 |
国内免费 | 385篇 |
出版年
2023年 | 35篇 |
2022年 | 98篇 |
2021年 | 172篇 |
2020年 | 154篇 |
2019年 | 194篇 |
2018年 | 204篇 |
2017年 | 166篇 |
2016年 | 224篇 |
2015年 | 326篇 |
2014年 | 345篇 |
2013年 | 366篇 |
2012年 | 507篇 |
2011年 | 445篇 |
2010年 | 306篇 |
2009年 | 301篇 |
2008年 | 355篇 |
2007年 | 323篇 |
2006年 | 275篇 |
2005年 | 295篇 |
2004年 | 301篇 |
2003年 | 285篇 |
2002年 | 282篇 |
2001年 | 185篇 |
2000年 | 124篇 |
1999年 | 123篇 |
1998年 | 67篇 |
1997年 | 55篇 |
1996年 | 35篇 |
1995年 | 29篇 |
1994年 | 40篇 |
1993年 | 26篇 |
1992年 | 39篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 14篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1981年 | 24篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1974年 | 18篇 |
1973年 | 16篇 |
1972年 | 14篇 |
1969年 | 15篇 |
1967年 | 11篇 |
1963年 | 12篇 |
排序方式: 共有7076条查询结果,搜索用时 15 毫秒
181.
Jinnan Wang Maobin Guan Kiyofumi Yamada Daniel S. Hippe William S. Kerwin Chun Yuan Peter B?rnert Xihai Zhao 《PloS one》2016,11(2)
Objectives
Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) technique was recently proposed for joint MRA and intraplaque hemorrhage (IPH) imaging. The purpose of this study is to validate SNAP’s MRA performance in patients with suspected intracranial artery disease.Methods
SNAP and time-of-flight (TOF) techniques with matched field of view and resolution were applied on 15 patients with suspected intracranial artery disease. Both techniques were evaluated based on their detection of luminal stenosis of bilateral middle cerebral arteries (MCA) and the delineation of smallest visible branches (SVB) of the MCA. Statistical analysis was conducted on the artery level.Results
The SNAP MRA was found to provide similar stenosis detection performance when compared with TOF (Cohen’s κ 0.79; 95% Confidence Interval: 0.56–0.99). For the SVB comparison, SNAP was found to provide significantly better small artery delineation than TOF (p = 0.017). Inter-reader reproducibility for both measurements on SNAP was over 0.7. SNAP also detected IPH lesions on 13% of the patients.Conclusions
The SNAP technique’s MRA performance was optimized and compared against TOF for intracranial artery atherosclerosis imaging and was found to provide comparable stenosis detection accuracy. Along with its IPH detection capability, SNAP holds the potential to become a first-line screening tool for high risk intracranial atherosclerosis disease evaluation. 相似文献182.
183.
Feng En Lo Po Jung Lu Min Kuang Tsai June Han Lee Christopher Wen Chi Pang Wen Jackson Pui Man Wai Chwen Keng Tsao Po Huang Chiang Shu Yu Lyu Ko Lu Ma Ying-Chen Chi Chu-Shiu Li Chwen-Chi Liu Xifeng Wu 《PloS one》2016,11(4)
ObjectiveTo assess the benefits of regular exercise in reducing harms associated with betel quid (BQ) chewing.MethodsThe study cohort, 419,378 individuals, participated in a medical screening program between 1994 and 2008, with 38,324 male and 1,495 female chewers, who consumed 5–15 quids of BQ a day. Physical activity of each individual, based on “MET-hour/week”, was classified as “inactive” or “active”, where activity started from a daily 15 minutes/day or more of brisk walking (≥3.75 MET-hour/week). Hazard ratios for mortality and remaining years in life expectancy were calculated.ResultsNearly one fifth (18.7%) of men, but only 0.7% of women were chewers. Chewers had a 10-fold increase in oral cancer risk; and a 2-3-fold increase in mortality from lung, esophagus and liver cancer, cardiovascular disease, and diabetes, with doubling of all-cause mortality. More than half of chewers were physically inactive (59%). Physical activity was beneficial for chewers, with a reduction of all-cause mortality by 19%. Inactive chewers had their lifespan shortened by 6.3 years, compared to non-chewers, but being active, chewers improved their health by gaining 2.5 years. The improvement, however, fell short of offsetting the harms from chewing.ConclusionsChewers had serious health consequences, but being physically active, chewers could mitigate some of these adverse effects, and extend life expectancy by 2.5 years and reduce mortality by one fifth. Encouraging exercise, in addition to quitting chewing, remains the best advice for 1.5 million chewers in Taiwan. 相似文献
184.
185.
186.
A new concept of multiple redox semi‐solid‐liquid (MRSSL) flow battery that takes advantage of active materials in both liquid and solid phases, is proposed and demonstrated. Liquid lithium iodide (LiI) electrolyte and solid sulfur/carbon (S/C) composite, forming LiI‐S/C MRSSL catholyte, are employed to demonstrate this concept. Record volumetric capacity (550 Ah L?1catholyte) is achieved using highly concentrated and synergistic multiple redox reactions of LiI and sulfur. The liquid LiI electrolyte is found to increase the reversible volumetric capacity of the catholyte, improve the electrochemical utilization of the S/C composite, and reduce the viscosity of catholyte. A continuous flow test is demonstrated and the influence of the flow rate on the flow battery performance is discussed. The MRSSL flow battery concept transforms inactive component into bi‐functional active species and creates synergistic interactions between multiple redox couples, offering a new direction and wide‐open opportunities to develop high‐energy‐density flow batteries. 相似文献
187.
Self‐Assembled BiFeO3‐ε‐Fe2O3 Vertical Heteroepitaxy for Visible Light Photoelectrochemistry 下载免费PDF全文
Le Thi Quynh Chien Nguyen Van Yugandhar Bitla Jhih‐Wei Chen Thi Hien Do Wen‐Yen Tzeng Sheng‐Chieh Liao Kai‐An Tsai Yi‐Chun Chen Chun‐Lin Wu Chih‐Huang Lai Chih‐Wei Luo Yung‐Jung Hsu Ying‐Hao Chu 《Liver Transplantation》2016,6(18)
Self‐assembled vertical heterostructure with a high interface‐to‐volume ratio offers tremendous opportunities to realize intriguing properties and advanced modulation of functionalities. Here, a heterostructure composed of two visible‐light photocatalysts, BiFeO3 (BFO) and ε‐Fe2O3 (ε‐FO), is designed to investigate its photoelectrochemical performance. The structural characterization of the BFO‐FO heterostructures confirms the phase separation with BFO nanopillars embedded in the ε‐FO matrix. The investigation of band structure of the heterojunction suggests the assistance of photoexcited carrier separation, leading to an enhanced photoelectrochemical performance. The insights into the charge separation are further revealed by means of ultrafast dynamics and electrochemical impedance spectroscopies. This work shows a delicate design of the self‐assembled vertical heteroepitaxy by taking advantage of the intimate contact between two phases that can lead to a tunable charge interaction, providing a new configuration for the optimization of photoelectrochemical cell. 相似文献
188.
189.
Skin aging caused by intrinsic or extrinsic processes characterized with functional proteomics 下载免费PDF全文
Jia‐You Fang Pei‐Wen Wang Chun‐Hsun Huang Mu‐Hong Chen Yun‐Ru Wu Tai‐Long Pan 《Proteomics》2016,16(20):2718-2731
The skin provides protection against environmental stress. However, intrinsic and extrinsic aging causes significant alteration to skin structure and components, which subsequently impairs molecular characteristics and biochemical processes. Here, we have conducted an immunohistological investigation and established the proteome profiles on nude mice skin to verify the specific responses during aging caused by different factors. Our results showed that UVB‐elicited aging results in upregulation of proliferating cell nuclear antigen and strong oxidative damage in DNA, whereas chronological aging abolished epidermal cell growth and increased the expression of caspase‐14, as well as protein carbonylation. Network analysis indicated that the programmed skin aging activated the ubiquitin system and triggered obvious downregulation of 14‐3‐3 sigma, which might accelerate the loss of cell growth capacity. On the other hand, UVB stimulation enhanced inflammation and the risk of skin carcinogenesis. Collectively, functional proteomics could provide large‐scale investigation of the potent proteins and molecules that play important roles in skin subjected to both intrinsic and extrinsic aging. 相似文献
190.