全文获取类型
收费全文 | 219954篇 |
免费 | 20735篇 |
国内免费 | 15439篇 |
专业分类
耳鼻咽喉 | 1905篇 |
儿科学 | 2193篇 |
妇产科学 | 2987篇 |
基础医学 | 26556篇 |
口腔科学 | 3688篇 |
临床医学 | 30899篇 |
内科学 | 32965篇 |
皮肤病学 | 2232篇 |
神经病学 | 12395篇 |
特种医学 | 8249篇 |
外国民族医学 | 138篇 |
外科学 | 21757篇 |
综合类 | 35540篇 |
现状与发展 | 55篇 |
一般理论 | 19篇 |
预防医学 | 13196篇 |
眼科学 | 6697篇 |
药学 | 22767篇 |
195篇 | |
中国医学 | 12425篇 |
肿瘤学 | 19270篇 |
出版年
2024年 | 698篇 |
2023年 | 3555篇 |
2022年 | 9191篇 |
2021年 | 11520篇 |
2020年 | 8608篇 |
2019年 | 7548篇 |
2018年 | 8047篇 |
2017年 | 7098篇 |
2016年 | 6664篇 |
2015年 | 10272篇 |
2014年 | 12576篇 |
2013年 | 10718篇 |
2012年 | 16029篇 |
2011年 | 17980篇 |
2010年 | 10532篇 |
2009年 | 8204篇 |
2008年 | 11134篇 |
2007年 | 11118篇 |
2006年 | 11258篇 |
2005年 | 11340篇 |
2004年 | 7026篇 |
2003年 | 6634篇 |
2002年 | 5521篇 |
2001年 | 4952篇 |
2000年 | 5368篇 |
1999年 | 5709篇 |
1998年 | 3535篇 |
1997年 | 3509篇 |
1996年 | 2832篇 |
1995年 | 2618篇 |
1994年 | 2156篇 |
1993年 | 1385篇 |
1992年 | 1893篇 |
1991年 | 1598篇 |
1990年 | 1297篇 |
1989年 | 1094篇 |
1988年 | 1028篇 |
1987年 | 891篇 |
1986年 | 728篇 |
1985年 | 526篇 |
1984年 | 336篇 |
1983年 | 242篇 |
1982年 | 150篇 |
1981年 | 145篇 |
1980年 | 111篇 |
1979年 | 142篇 |
1978年 | 49篇 |
1977年 | 53篇 |
1975年 | 57篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The objective of this study was to investigate the absorption behavior of chikusetsusaponin IVa (CHS‐IVa) in the rat intestine using single‐pass intestinal perfusion (SPIP) and to classify CHS‐IVa into the biopharmaceutics classification system (BCS). The equilibrium solubility of CHS‐IVa was determined by the shaker method. The absorption mechanism of CHS‐IVa in the intestine was studied by comparing the Peff of different concentrations of CHS‐IVa. The intestinal site dependence of CHS‐IVa absorption was studied by comparing the Peff of the same concentration of CHS‐IVa in different intestinal segments. The relationship between CHS‐IVa and intestinal efflux protein was studied by perfusion with an efflux protein inhibitor. The permeability of CHS‐IVa was investigated by comparing the Peff of CHS‐IVa and the reported value. The solubility of CHS‐IVa over the pH range 1.0–7.5 was 14.4 ± 0.29 to 16.9 ± 0.34 mg/ml. The Peff of CHS‐IVa in the duodenum was 1.76 × 10?3 to 2.00 × 10?3 cm/min. The Peff of CHS‐IVa in the jejunum was 1.26 × 10?3 to 1.39 × 10?3 cm/min. The Peff of CHS‐IVa in the ileum was 1.25 × 10?3 to 1.31 × 10?3 cm/min. The Peff of CHS‐IVa in the colon was 1.02 × 10?3 to 1.08 × 10?3 cm/min. There was no statistical difference of the Peff in the four segments at different CHS‐IVa concentrations. The Peff of CHS‐IVa (0.07, 0.7 and 7.0 mg/ml) were all notably smaller than the reported Peff (3.00 × 10?3 cm/min) in the jejunum. The Peff of CHS‐IVa was not influenced by verapamil (P‐gp inhibitor), indomethacin (MRP inhibitor) and pantoprazole (BCRP inhibitor). CHS‐IVa was classified as high solubility, low permeability and BCS III. The main absorptive tracts were the upper intestinal tracts and the rank order of intestinal permeability was duodenum > jejunum ≈ ileum > colon. The transport mechanism of CHS‐IVa in all intestinal segments might be primarily passive transport. CHS‐IVa was not a substrate of P‐gp, MRP and BCRP. 相似文献
82.
Pengfei Liu 《Remote sensing letters.》2019,10(7):659-668
This letter proposed a new and effective total generalized variation (TGV) induced spatial difference prior model for variational pansharpening problem, which aimed to estimate a high-resolution (HR) multispectral (MS) image from its low-resolution (LR) version and the corresponding HR panchromatic (Pan) image of the same earth scene. In addition to using the local spectral consistency constraint for spectral information preserving, this letter particularly exploited the spatial difference prior between the HR-MS and Pan images, and hence proposed a new TGV-induced spatial difference prior term for spatial information preserving. Then, an efficient optimization algorithm was designed for solving the proposed model under the fast iterative shrinkage-thresholding algorithm (FISTA) framework. Finally, the experimental results validated that the proposed method performed higher spatial and spectral qualities than various methods in both the subjective and objective aspects. 相似文献
83.
84.
85.
Xiaoxuan Liu Ameenat L. Solebo Livia Faes Sophie Beese Tasanee Braithwaite Matthew E. Round 《Ocular immunology and inflammation》2020,28(6):898-907
ABSTRACT
Purpose
New instrument-based techniques for anterior chamber (AC) cell counting can offer automation and objectivity above clinician assessment. This review aims to identify such instruments and its correlation with clinician estimates. 相似文献86.
This paper reviews the published literature on a group of developmental disorders of the retina and retinal pigment epithelium which result in focal abnormalities in one or both eyes. They are often asymptomatic, found on routine examination and are generally non-progressive. Some are associated with other systemic abnormalities.Subject terms: Retinal diseases, Eye abnormalities 相似文献
87.
88.
89.
S. Xing X. Zhang J. H. Liu X. Huang P. Zhou 《Clinical and experimental immunology》2019,195(1):121-131
Recent experimental strategies to reduce graft-versus-host disease (GVHD) have focused largely on modifying innate immunity. Toll-like receptor (TLR)-driven myeloid differentiation primary response 88 (MyD88)-dependent signalling pathways that initiate adaptive immune function are also critical for the pathogenesis of GVHD. This study aimed to delineate the role of host MyD88 in the development of acute GVHD following fully major histocompatibility complex-mismatched allogeneic bone marrow transplantation (BMT). When myeloablated BALB/c MyD88 knock-out recipients were transplanted with C57BL/6 (B6) donor cells, they developed significantly more severe GVHD than wild-type (WT) BALB/c hosts. The increased morbidity and mortality in MyD88–/– mice correlated with increased serum levels of lipopolysaccharide and elevated inflammatory cytokines in GVHD target organs. Additionally, MyD88 deficiency in BMT recipients led to increased donor T cell expansion and more donor CD11c+ cell intestinal infiltration with apoptotic cells but reduced proliferation of intestinal epithelial cells compared with that in WT BMT recipients. Decreased expression of tight junction mRNA in epithelial cells of MyD88–/– mice suggested that MyD88 contributes to intestinal integrity. Cox-2 expression in the GVHD-targeted organs of WT mice is increased upon GVHD induction, but this enhanced expression was obviously inhibited by MyD88 deficiency. The present findings demonstrate an unexpected role for host MyD88 in preventing GVHD after allogeneic BMT. 相似文献
90.
BackgroundArtificial insemination with the husband’s semen (AIH) is an economical and noninvasive method of infertility treatment. However, AIH’s pregnancy rate is much lower than in vitro fertilization (IVF) as its multiple and complex uncertainty factors. Semen quality has been one of the main factors which affect the pregnancy outcome of AIH.MethodsThe relevant parameters of 1,142 AIH cycles were retrospectively studied, including the general parameters and the semen quality parameters among clinical pregnancy, biochemical pregnancy, non-pregnancy group, age, infertility duration, infertility type, body mass index (BMI), cycle count, morphology in previously semen examination, and semen quality parameters on the day of AIH.ResultsThe statistically significant difference was only found on processed total non-forward and non-motile sperm count (N-TFMSC). The mean processed N-TFMSC in the biochemical pregnancy group was 6.37±4.27 million, significantly higher than the other two groups (vs. 4.40±3.15 million or vs. 4.48±3.60 million, P<0.05). The study was then divided into two groups according to processed N-TFMSC, Group 1 ≤5.0 million, and Group 2 >5.0 million. A statistical increase in biochemical pregnancy rate was observed when the processed N-TFMSC was >5.0 million (2.72% vs. 0.90%).ConclusionsProcessed N-TFMSC may be one of the independent factors on AIH’s outcome; it should be given equal attention the same as processed total forward motile sperm count (TFMSC). 相似文献