首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3046篇
  免费   162篇
  国内免费   22篇
耳鼻咽喉   19篇
儿科学   63篇
妇产科学   13篇
基础医学   381篇
口腔科学   72篇
临床医学   192篇
内科学   716篇
皮肤病学   28篇
神经病学   376篇
特种医学   108篇
外科学   623篇
综合类   18篇
一般理论   1篇
预防医学   50篇
眼科学   16篇
药学   143篇
中国医学   2篇
肿瘤学   409篇
  2023年   33篇
  2022年   59篇
  2021年   116篇
  2020年   60篇
  2019年   60篇
  2018年   65篇
  2017年   61篇
  2016年   77篇
  2015年   77篇
  2014年   110篇
  2013年   120篇
  2012年   183篇
  2011年   196篇
  2010年   111篇
  2009年   101篇
  2008年   176篇
  2007年   190篇
  2006年   177篇
  2005年   192篇
  2004年   186篇
  2003年   142篇
  2002年   161篇
  2001年   50篇
  2000年   52篇
  1999年   49篇
  1998年   41篇
  1997年   45篇
  1996年   32篇
  1995年   21篇
  1994年   22篇
  1993年   14篇
  1992年   20篇
  1991年   19篇
  1990年   19篇
  1989年   22篇
  1988年   11篇
  1987年   13篇
  1986年   17篇
  1985年   14篇
  1984年   21篇
  1983年   18篇
  1982年   5篇
  1981年   11篇
  1979年   8篇
  1978年   5篇
  1977年   10篇
  1976年   6篇
  1973年   6篇
  1967年   4篇
  1966年   4篇
排序方式: 共有3230条查询结果,搜索用时 15 毫秒
71.
We examined the genomic status of the p16INK4A (inhibitor of cyclin-dependent kinase 4 A) and cyclin-dependent kinase 4 (CDK4) genes in 62 human hepatocellular carcinomas (HCCs), 5 cholangiocellular carcinomas and 6 cell lines derived from human liver cancers. Although no samples showed the homozygous deletion of the p16INK4A gene, we detected intragenic mutations of the p16INK4A gene in 3 HCCs and one HCC cell line, which led to an amino-acid substitution or a frameshift. In 2 HCC samples with mis-sense mutations of the p16INK4A gene, loss of heterozygosity on 9p22 was also detected, suggesting that the loss of function of p16 was induced during hepatocarcinogenesis. On the other hand, amplification or rearrangement of the CDK4 gene was not detected in any samples examined in this study. These results indicated that the mutations or deletions of the p16INK4A gene are not frequent, but may play a role in a sub-set of human HCC. © 1996 Wiley-Liss, Inc.  相似文献   
72.
A 57-year-old man without underlying diseases presented with fatigue, loss of appetite, and jaundice 1 week after receiving the first dose of the BNT162b2 mRNA coronavirus disease 2019 (COVID-19) vaccine and showed hemolytic anemia with fragmented erythrocytes and severe thrombocytopenia 2 weeks after receiving the vaccine. An a disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) activity level of <10% and ADAMTS13 inhibitor positivity confirmed the diagnosis of acquired thrombotic thrombocytopenic purpura (TTP). Combination therapy with plasma exchange, corticosteroid, and rituximab improved the clinical outcome. We herein report the first Japanese case of TTP possibly associated with vaccination. Physicians should be alert for this rare but life-threatening hematological complication following COVID-19 vaccination.  相似文献   
73.
A novel platinum nanoparticle catalyst closely located near the surface of titanium oxide, PtNP/TiO2, has been prepared. This catalyst has both the properties of a photocatalyst and a metal nanoparticle catalyst, and acquired environmentally friendly catalytic activity, which cannot be achieved by just one of these catalysts, to afford ethers from benzyl alcohols under the wavelength of 420 nm.

A novel platinum nanoparticle catalyst closely located near the surface of titanium oxide, PtNP/TiO2, has been prepared. It has catalytic activity to afford ethers from benzyl alcohols under the wavelength of 420 nm.

The electrolysis of water by a heterogeneous metal oxide semiconductor (MOS) photocatalyst, called the Honda–Fujishima effect,1 received considerable attention because it enables the conversion of solar energy. As a result, photoreactions by heterogeneous photocatalysts based on MOS have been reported until now, including numerous practical applications such as carbon dioxide reduction2 and pollutant removal.3Research on photocatalytic reactions using visible light is progressing steadily. Among them, TiO2 has been extensively studied due to its high catalytic activity, low cost, non-toxicity, and long-term stability.4,5Titanium oxide has a very strong oxidizing power, but it does not have a strong reducing power.6 By using a transition metal such as platinum on titanium oxide as a support, its reducing power can be increased, and the amount of hydrogen generated in the electrolysis of water can be improved eight times compared to the case of titanium oxide alone.7Furthermore, when MOS contacts the metal, a potential barrier called Schottky barrier is formed at the interface. The basic characteristic of this Schottky barrier lies in the Schottky barrier height (Φ), which represents the difference between the CB of the MOS distorted by the contact with a metal and the Fermi level (EF) of the metal. Although it has been studied for almost half a century, how to determine the barrier is still not well understood. Due to the formation of the Schottky barrier height, the energy required to move the electrons from the valence band of MOS to the conductor changes from Eg to Φ, and the energy becomes smaller and it changes to a longer wavelength. As a result, a photoreaction with titanium oxide using light with a wavelength longer than 387 nm has also been reported (Scheme 1)8Open in a separate windowScheme 1Effect of sunlight exposure on aerobic oxidation of alcohols with the Pt/TiO2 catalysts.On the other hand, we have recently developed a sulfur-modified Au-supported Pd NP catalyst (SAPd) that is applicable in Suzuki–Miyaura coupling9a,9b and C–H functionalization9c (Scheme 2a). It was constructed by approximately 10 layers of self-assembled Pd(0) NPs (mean size: <5 nm) supported on a sulfur-modified Au surface. We speculated that the self-assembled Pd NPs, which were encapsulated in a sulfated p-xylene polymer matrix,9d were formed using in situ metal NP and nanospace simultaneous organization (PSSO), as illustrated in Scheme 2b: (i) the reduction of a high-valence metal source, (ii) growth of transition metal NPs, (iii) growth of a matrix with appropriately sized nanopores, and (iv) encapsulation of the metal NPs in these nanopores. To prepare SARu,10 SANi,11 SAFe(ii),12 and SAFe(0)13 (Scheme 2a), the PSSO method involves the in situ reduction of a noble metal precursor to produce in situ metal NPs.Open in a separate windowScheme 2(a) Preparation of SAPd, SARu, SANi, SAFe(II) and SAFe(0) by combining in situ PSSO with an organic reductant, (b) in situ metal nanoparticle and nanospace simultaneous organization (PSSO) method and the image of the SAPd structure and (c) the preparation of PtNP/TiO2.In this research project, we decided to create a novel metal NP catalyst having metal NPs near the surface of TiO2 by substituting the gold-supported SAPd for gold with a titanium oxide (TiO2) photocatalyst. Alternatively, by substituting the solid gold support for a photocatalyst, we thought that we could create a novel metal NPs catalyst with an unprecedented reactivity by combining the properties of both photocatalyst and metal nanoparticle catalyst (Scheme 2c).  相似文献   
74.
75.
Marinesco bodies (MBs) are spherical nuclear inclusions found in pigmented neurons of the substantia nigra. Although MBs are abundant in senescent brains, how they are related to aging processes remains unclear. Here, we performed a morphometric analysis of midbrain pigmented neurons to identify the possible influence of MBs on nuclear size. The transected area of the nucleus (nuclear area) was larger in the presence of MBs and was correlated with the area of MB (MB area) in all tested brains. The MB-associated nuclear enlargement was significant even after MB areas were subtracted from nuclear areas. Moreover, higher MB immunoreactivity of p62 was detected in the nucleoplasm of the enlarged MB-associated nuclei. This study on human brains is the first quantitative approach demonstrating MB-associated nuclear enlargement and progressive accumulation of small nucleoplasmic materials. Although cellular hypertrophy is usually considered to be an indication of the upregulation of cellular function, this might not always be the case. These findings suggest that an age-related decline of ubiquitin-proteasome and autophagy system activity and stagnation of undegradable materials are one of the candidate mechanisms to explain the age-related decline of neural activity in the substantia nigra.  相似文献   
76.
Multiple system atrophy (MSA) is an oligodendrogliopathy of presumably sporadic origin, characterized by prominent α‐synuclein inclusions with neuronal multisystem degeneration, although a few Mendelian pedigrees have been reported. Here we report two familial cases of MSA of unknown genetic background. One patient was diagnosed as a possible MSA‐C (cerebellar dysfuntion) case, and the other as clinically possible MSA‐P (parkinsonism), which turned out to be definite MSA, based on a detailed autopsy. The neuropathology showed extensive deposition of α‐synuclein in the glia as well as in the neurons located in the cerebral cortices and hippocampal systems, although neither multiplication of the SNCA gene or mutations in COQ2 gene were identified in the family concerned.  相似文献   
77.

Objective

Previous studies have demonstrated the relationship between ageing and oxidative stress. In this study, we examined the effects of topical application of a dentifrice containing anti-oxidative, anti-inflammatory, and anti-bacterial agents (Tomarina®) to the gingival surface on gingival collagen degradation in rats.

Design

Fischer 344 male rats (4 or 8 months old) were divided into two groups: experimental group and control group. Tomarina® (the experimental group) or control dentifrice (the control group) was applied 5 days per week for 2 months.

Results

In the control group, gingival collagen density decreased with ageing. In the experimental group, the collagen density did not change with ageing, and was greater than that in the control group at 10 months of age (p < 0.0083). In addition, the control group showed an increase in serum oxidative stress with ageing. The experimental group also showed increased serum oxidative stress, but the value was lower than the control group at 10 months of age (p < 0.0083). Furthermore, low expressions of protein oxidative damage in the periodontal tissue were observed in the experimental group, compared to the control group at 6 months and 10 months.

Conclusion

These findings indicate that Tomarina® might suppress the effects of ageing on gingival collagen degradation, by decreasing oxidative stress in the rat model.  相似文献   
78.
79.
80.
Intussusception is rare in adults and it is difficult to diagnose on admission. We present the case of a 43-year-old woman with the chief complaint of nausea and upper abdominal pain. Abdominal multidetector-row computed tomography showed ileo-ileal small bowel intussusception with an intraluminal soft tissue mass with attenuation numbers suggestive of a lipoma. The patient was treated with a laparoscopic-assisted extracorporeal partial resection of the small bowel including ileal lipoma, followed by a functional end-to-end anastomosis. Histologic diagnosis of the resected tumor, 2.4×2.0×2.0 cm, was an intestinal lipoma. This case serves as the basis of a review of small bowel intussusception in adults secondary to lipomas. It focuses on the utility of multidetector-row computed tomography and the cosmetic, physical, and economic benefits of laparoscopic surgery as well as the rarity of the disease.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号