全文获取类型
收费全文 | 340918篇 |
免费 | 10618篇 |
国内免费 | 425篇 |
专业分类
耳鼻咽喉 | 3369篇 |
儿科学 | 12104篇 |
妇产科学 | 6500篇 |
基础医学 | 39026篇 |
口腔科学 | 8965篇 |
临床医学 | 24350篇 |
内科学 | 68275篇 |
皮肤病学 | 4974篇 |
神经病学 | 30149篇 |
特种医学 | 13937篇 |
外国民族医学 | 26篇 |
外科学 | 48948篇 |
综合类 | 3666篇 |
现状与发展 | 1篇 |
一般理论 | 60篇 |
预防医学 | 35323篇 |
眼科学 | 5843篇 |
药学 | 19472篇 |
中国医学 | 1312篇 |
肿瘤学 | 25661篇 |
出版年
2023年 | 887篇 |
2022年 | 1942篇 |
2021年 | 3619篇 |
2020年 | 2429篇 |
2019年 | 3428篇 |
2018年 | 26129篇 |
2017年 | 20469篇 |
2016年 | 22330篇 |
2015年 | 4776篇 |
2014年 | 6138篇 |
2013年 | 7515篇 |
2012年 | 17341篇 |
2011年 | 31585篇 |
2010年 | 23994篇 |
2009年 | 16263篇 |
2008年 | 27557篇 |
2007年 | 30293篇 |
2006年 | 8986篇 |
2005年 | 10896篇 |
2004年 | 11576篇 |
2003年 | 11830篇 |
2002年 | 8033篇 |
2001年 | 5217篇 |
2000年 | 5369篇 |
1999年 | 4511篇 |
1998年 | 1739篇 |
1997年 | 1480篇 |
1996年 | 1355篇 |
1995年 | 1172篇 |
1994年 | 1167篇 |
1993年 | 1031篇 |
1992年 | 2693篇 |
1991年 | 2657篇 |
1990年 | 2465篇 |
1989年 | 2411篇 |
1988年 | 2163篇 |
1987年 | 1998篇 |
1986年 | 1854篇 |
1985年 | 1789篇 |
1984年 | 1276篇 |
1983年 | 1036篇 |
1982年 | 597篇 |
1981年 | 514篇 |
1980年 | 532篇 |
1979年 | 930篇 |
1978年 | 615篇 |
1975年 | 561篇 |
1974年 | 569篇 |
1973年 | 547篇 |
1970年 | 485篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
Selwyn Arlington Headley Nayara Emily Viana Mariana de Mello Zanim Michelazzo Ana Aparecida Correa Xavier Cícero Júlio Silva Costa Felipe Hideki Ogo de Pinho Marcelo Diniz dos Santos 《Transboundary and Emerging Diseases》2020,67(Z2):49-59
Neorickettsia helminthoeca (NH), the agent of salmon poisoning disease or canine neorickettiosis (CN), is a bacterial endosymbiont of the nematode Nanophyetus salmincola, and infections are spreading among specific fish‐eating mammalians. This article describes the pathologic and immunohistochemical findings associated with spontaneous NH‐induced infections in dogs from Southern Brazil. The principal pathologic findings were hypertrophy of Peyer patches and lymphadenopathy with lymphocytic proliferation, chronic interstitial pneumonia, and chronic enteritis associated with positive intralesional immunoreactivity to antigens of NH within macrophages and histiocytes. Positive immunoreactivity against canine parvovirus‐2 (CPV‐2) or/and canine distemper virus was not detected in the evaluated intestinal segments or in the samples from the cerebellum and lungs, respectively, from the dogs evaluated. These findings demonstrated that NH was involved in the enteric, pulmonary, and lymphoid lesions herein described, and provide additional information to confirm the occurrence of this bacterial endosymbiont within this geographical location. It is proposed that chronic pneumonia should be considered as a pathologic manifestation of NH‐induced infections. Additionally, our results show that the occurrences of CN seem to be underdiagnosed in Southern Brazil due to the confusion with the incidence of CPV‐2. 相似文献
2.
3.
4.
5.
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
6.
7.
8.
9.
10.
Dalton Luiz Schiessel Ricardo K. Yamazaki Marcelo Kryczyk Isabela Coelho de Castro Adriana A. Yamaguchi Danielle C. T. Pequito 《Nutrition and cancer》2016,68(8):1369-1380
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO. 相似文献