全文获取类型
收费全文 | 177827篇 |
免费 | 1157篇 |
国内免费 | 18篇 |
专业分类
耳鼻咽喉 | 1156篇 |
儿科学 | 6695篇 |
妇产科学 | 3052篇 |
基础医学 | 16753篇 |
口腔科学 | 1721篇 |
临床医学 | 12610篇 |
内科学 | 31169篇 |
皮肤病学 | 856篇 |
神经病学 | 16720篇 |
特种医学 | 9050篇 |
外科学 | 29133篇 |
综合类 | 2345篇 |
一般理论 | 6篇 |
预防医学 | 18245篇 |
眼科学 | 2786篇 |
药学 | 9613篇 |
中国医学 | 636篇 |
肿瘤学 | 16456篇 |
出版年
2023年 | 58篇 |
2021年 | 123篇 |
2020年 | 104篇 |
2019年 | 96篇 |
2018年 | 22016篇 |
2017年 | 17434篇 |
2016年 | 19583篇 |
2015年 | 966篇 |
2014年 | 877篇 |
2013年 | 905篇 |
2012年 | 7079篇 |
2011年 | 21161篇 |
2010年 | 18875篇 |
2009年 | 11604篇 |
2008年 | 19624篇 |
2007年 | 21803篇 |
2006年 | 638篇 |
2005年 | 2272篇 |
2004年 | 3445篇 |
2003年 | 4392篇 |
2002年 | 2545篇 |
2001年 | 366篇 |
2000年 | 475篇 |
1999年 | 228篇 |
1998年 | 213篇 |
1997年 | 220篇 |
1996年 | 100篇 |
1995年 | 113篇 |
1994年 | 103篇 |
1993年 | 68篇 |
1992年 | 67篇 |
1991年 | 118篇 |
1990年 | 151篇 |
1989年 | 112篇 |
1988年 | 78篇 |
1987年 | 74篇 |
1986年 | 54篇 |
1985年 | 62篇 |
1984年 | 34篇 |
1983年 | 43篇 |
1982年 | 46篇 |
1980年 | 46篇 |
1974年 | 26篇 |
1969年 | 29篇 |
1968年 | 25篇 |
1938年 | 61篇 |
1937年 | 27篇 |
1934年 | 30篇 |
1932年 | 56篇 |
1930年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
3.
4.
Li Bai Saeha Shin Richard T. Burnett Jeffrey C. Kwong Perry Hystad Aaron van Donkelaar Mark S. Goldberg Eric Lavigne Scott Weichenthal Randall V. Martin Ray Copes Alexander Kopp Hong Chen 《International journal of cancer. Journal international du cancer》2020,146(9):2450-2459
Lung and female breast cancers are highly prevalent worldwide. Although the association between exposure to ambient fine particulate matter (PM2.5) and lung cancer has been recognized, there is less evidence for associations with other common air pollutants such as nitrogen dioxide (NO2) and ozone (O3). Even less is known about potential associations between these pollutants and breast cancer. We conducted a population-based cohort study to investigate the associations of chronic exposure to PM2.5, NO2, O3 and redox-weighted average of NO2 and O3 (Ox) with incident lung and breast cancer, using the Ontario Population Health and Environment Cohort (ONPHEC), which includes all long-term residents aged 35–85 years who lived in Ontario, Canada, 2001–2015. Incident lung and breast cancers were ascertained using the Ontario Cancer Registry. Annual estimates of exposures were assigned to the residential postal codes of subjects for each year during follow-up. We used Cox proportional-hazards models adjusting for personal- and neighborhood-level covariates. Our cohorts for lung and breast cancer analyses included ~4.9 million individuals and ~2.5 million women, respectively. During follow-up, 100,146 incident cases of lung cancer and 91,146 incident cases of breast cancer were diagnosed. The fully adjusted analyses showed positive associations of lung cancer incidence with PM2.5 (hazard ratio [HR] = 1.02 [95% CI: 1.01–1.05] per 5.3 μg/m3) and NO2 (HR = 1.05 [95% CI: 1.03–1.07] per 14 ppb). No associations with lung cancer were observed for O3 or Ox. Relationships between PM2.5 and NO2 with lung cancer exhibited a sublinear shape. We did not find compelling evidence linking air pollution to breast cancer. 相似文献
5.
N. S. Hari Narayana Moorthy Sergio F. Sousa Maria J. Ramos Pedro A. Fernandes 《Medicinal chemistry research》2016,25(7):1340-1357
Farnesyltransferase (FTase) is one of the prenyltransferase family enzymes that catalyse the transfer of 15-membered isoprenoid (farnesyl) moiety to the cysteine of CAAX motif-containing proteins including Rho and Ras family of G proteins. Inhibitors of FTase act as drugs for cancer, malaria, progeria and other diseases. In the present investigation, we have developed two structure-based pharmacophore models from protein–ligand complex (3E33 and 3E37) obtained from the protein data bank. Molecular dynamics (MD) simulations were performed on the complexes, and different conformers of the same complex were generated. These conformers were undergone protein–ligand interaction fingerprint (PLIF) analysis, and the fingerprint bits have been used for structure-based pharmacophore model development. The PLIF results showed that Lys164, Tyr166, TrpB106 and TyrB361 are the major interacting residues in both the complexes. The RMSD and RMSF analyses on the MD-simulated systems showed that the absence of FPP in the complex 3E37 has significant effect in the conformational changes of the ligands. During this conformational change, some interactions between the protein and the ligands are lost, but regained after some simulations (after 2 ns). The structure-based pharmacophore models showed that the hydrophobic and acceptor contours are predominantly present in the models. The pharmacophore models were validated using reference compounds, which significantly identified as HITs with smaller RMSD values. The developed structure-based pharmacophore models are significant, and the methodology used in this study is novel from the existing methods (the original X-ray crystallographic coordination of the ligands is used for the model building). In our study, along with the original coordination of the ligand, different conformers of the same complex (protein–ligand) are used. It concluded that the developed methodology is significant for the virtual screening of novel molecules on different targets. 相似文献
6.
Valerie Iles 《Health care analysis》2016,24(2):105-118
This paper takes a somewhat slant perspective on flourishing and care in the context of suffering, death and dying, arguing that care in this context consists principally of ‘acts of work and courage that enable flourishing’. Starting with the perception that individuals, society and health care professionals have become dulled to death and the process of dying in Western advanced health systems, it suggests that for flourishing to occur, both of these aspects of life need to be faced more directly. The last days of life need to be ‘undulled’. Reflections upon the experiences of the author as carer and daughter in the face of her mother’s experience of death are used as basis for making suggestions about how care systems and professionals might better assist people in dealing with ‘the most grown up thing’ humans ever do, which is to die. 相似文献
7.
8.
Henry Havel Gregory Finch Pamela Strode Marc Wolfgang Stephen Zale Iulian Bobe Hagop Youssoufian Matthew Peterson Maggie Liu 《The AAPS journal》2016,18(6):1373-1378
Advancing nanomedicines from concept to clinic requires integration of new science with traditional pharmaceutical development. The medical and commercial success of nanomedicines is greatly facilitated when those charged with developing nanomedicines are cognizant of the unique opportunities and technical challenges that these products present. These individuals must also be knowledgeable about the processes of clinical and product development, including regulatory considerations, to maximize the odds for successful product registration. This article outlines these topics with a goal to accelerate the combination of academic innovation with collaborative industrial scientists who understand pharmaceutical development and regulatory approval requirements—only together can they realize the full potential of nanomedicines for patients. 相似文献
9.
10.
M. Alexandra Friedman Charlotte M. Niznik Janelle R. Bolden Lynn M. Yee 《Journal of community health》2016,41(2):354-358
While peer support has been investigated in multiple clinical contexts, its application to the postpartum setting is unknown. The aim was to assess acceptability of a postpartum peer support program for women with diabetes. Observational survey-based needs assessment of forty low-income women with diabetes, receiving care at a major medical institution. Mean age and gravidity were 30.7 years and 3.15 ± 1.67 respectively. 45 % expressed interest in a “buddy.” There was no significant difference between groups desiring and not desiring this program. A majority of respondents desired telephone, text messaging, and in-person contacts (79.2, 72.1, 83.8 %), with 72.5 % of patients desiring diabetes-related activities during clinic waiting time. Many women desire a postpartum diabetes reciprocal peer program for support outside of clinician visits. Patients are receptive to educational services during their wait and outside of clinic time, a potentially valuable opportunity to share important health information. 相似文献