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   2384篇
  免费   181篇
  国内免费   19篇
耳鼻咽喉   8篇
儿科学   40篇
妇产科学   14篇
基础医学   313篇
口腔科学   121篇
临床医学   144篇
内科学   593篇
皮肤病学   18篇
神经病学   113篇
特种医学   158篇
外科学   255篇
综合类   34篇
预防医学   112篇
眼科学   25篇
药学   299篇
中国医学   7篇
肿瘤学   330篇
  2023年   19篇
  2022年   22篇
  2021年   50篇
  2020年   30篇
  2019年   49篇
  2018年   51篇
  2017年   55篇
  2016年   52篇
  2015年   52篇
  2014年   59篇
  2013年   80篇
  2012年   107篇
  2011年   125篇
  2010年   65篇
  2009年   58篇
  2008年   94篇
  2007年   112篇
  2006年   83篇
  2005年   85篇
  2004年   91篇
  2003年   76篇
  2002年   77篇
  2001年   92篇
  2000年   79篇
  1999年   83篇
  1998年   42篇
  1997年   55篇
  1996年   20篇
  1995年   19篇
  1994年   19篇
  1993年   17篇
  1992年   66篇
  1991年   69篇
  1990年   58篇
  1989年   48篇
  1988年   45篇
  1987年   43篇
  1986年   55篇
  1985年   62篇
  1984年   31篇
  1983年   25篇
  1982年   14篇
  1981年   9篇
  1979年   16篇
  1978年   12篇
  1977年   14篇
  1976年   9篇
  1974年   14篇
  1973年   11篇
  1968年   13篇
排序方式: 共有2584条查询结果,搜索用时 0 毫秒
51.
52.
53.
A 23-year-old man had an 8-day history of fatigue and dry cough and papulo-nodular reactions on his extensive tattoos. Chest radiography revealed several small granular shadows, and a transbronchial lung biopsy showed non-caseating epithelioid cell granuloma. A skin biopsy of the tattooed area showed histiocytic infiltrates with phagocytized tattoo pigment. Antibody tests for hepatitis C virus were positive. The patient was successfully treated with corticosteroid therapy, and after inflammation was suppressed, he received delayed anti-viral therapy. Sarcoidosis should be considered as a concurrent condition if papules are presented on the tattoos of patients with hepatitis C.  相似文献   
54.
Mak  Lung-Yi  Huang  Qi  Wong  Danny Ka-Ho  Stamm  Luisa  Cheung  Ka-Shing  Ko  Kwan-Lung  Yan  Ran  Ouyang  Lea  Fung  James  Seto  Wai-Kay  Yuen  Man-Fung 《Journal of gastroenterology》2021,56(5):479-488
Journal of Gastroenterology - We aimed to assess whether residual hepatitis B virus (HBV) viraemia is associated with HCC development. This is a case–control study of 104 patients [52 HCC and...  相似文献   
55.
超过60%的胃神经内分泌肿瘤(gastric neuroendocrine neoplasms,G-NENs)内镜下病变表现为多发病灶,可为息肉样隆起、黏膜下来源的肿瘤,或为丘疹、糜烂、溃疡性病灶,病变多局限于黏膜层或黏膜下层,病灶多数<10 mm,平均5 mm。1型G-NENs中,约22%病例内镜下并无任何肉眼可见的病灶,只有通过胃体、胃底的盲检,显微镜下才能发现病灶,即微小类癌。本例患者胃镜下并无任何肉眼可见的隆起型病灶,因一次随机活检,才得以发现病变。本文结合该例病变内镜下表现及其临床特征,以提升诊断G-NENs的经验。  相似文献   
56.
Insulin-like growth factors-I and -II (IGF-I and -II) are structurally related mitogenic polypeptides with potent growth promoting effects. These peptides and their corresponding IGF-I and -II receptors are selectively localized in the brain. To date, most of the effects of IGFs are believed to be mediated by IGF-I receptors whereas the significance of IGF-II receptor in mediating biological responses remains unclear. In the present study, we characterized the distribution of IGF-I and IGF-II receptor sites and investigated the effects of both factors on endogenous acetylcholine (ACh) release in adult rat hippocampus. [125I]IGF-I receptor binding sites are recognized by IGF-I> IGF-II> insulin, whereas [125I]IGF-II binding was competed potently by IGF-II> IGF-I but not by insulin. At the cellular level, IGF-I receptor sites were primarily noted in the molecular layer of the dentate gyrus and the CA2-CA3 subfields of the Ammon’s horn whereas IGF-II sites were localized predominantly in the pyramidal cell layer of the CA1-CA3 subfields and in the granular cell layer of the dentate gyrus. IGF-I (10−14–10−8 M) and des(1–3) IGF-I (10−10–10−8 M) were found to inhibit whereas IGF-II (10−14–10−8 M) potentiated K+-evoked ACh release from hippocampal slices. Tetrodotoxin altered the effects of IGF-I but not those of IGF-II suggesting that IGF-I acts indirectly via the release of other modulators whereas IGF-II acts directly on or in close proximity to the cholinergic terminals. The inhibitory effects of IGF-I were also observed in the frontal cortex but not in the striatum. In contrast, the stimulatory effects of IGF-II were evident both in the frontal cortex and striatum. Taken together, these results reveal the differential localization of IGF-I and IGF-II receptor sites in the hippocampal formation and the opposite role for these growth factors in the acute regulation of ACh release likely via two distinct mechanisms. Additionally, these data provide the first evidence for a direct role for IGF-II and its receptors in the regulation of transmitter release in the central nervous system.  相似文献   
57.
Changes in sodium-22 turnover and total body potassium (TBK) were studied during acute (within 2 weeks after clipping) and chronic (12-14 weeks after clipping) phases in two-kidney, one-clip (2k, 1c) hypertensive rabbits by using a whole body counter. Sodium-22 injected intravenously was eliminated more rapidly in hypertensive rabbits than in controls. The biological half-life (BHL) of sodium-22 was shorter in hypertensive rabbits during both acute (p less than 0.05) and chronic phases (p less than 0.001). A significant negative correlation was obtained between the BHL of sodium-22 and blood pressure (r = -0.588, p less than 0.05) in hypertensive rabbits. TBK decreased significantly at the chronic phase in hypertensive rabbits (p less than 0.05), while TBK showed no significant change in controls. Serum sodium and potassium did not change during the observation period. Increased plasma aldosterone concentration was observed during the acute phase in hypertensive rabbits. These results suggested that sodium retention was not a major factor in the acute and chronic phases of 2k, 1c hypertension in rabbits and that pressure natriuresis could explain, at least in part, the lack of sodium retention. Furthermore, there appears to be a derangement in the intracellular potassium metabolism which may be associated with the maintenance rather than the development of hypertension.  相似文献   
58.
Purpose

JWH-424, (8-bromo-1-naphthyl)(1-pentyl-1H-indol-3-yl)methanone, is a synthetic cannabinoid, which is a brominated analogue of JWH-018, one of the best-known synthetic cannabinoids. Despite the structural similarity to JWH-018, little is known about JWH-424 including its metabolism. The aim of the study was to compare human liver microsomes (HLM) and the fungus Cunninghamella elegans as the metabolism catalysts for JWH-424 to better understand the characteristic actions of the fungus in the synthetic cannabinoid metabolism.

Methods

JWH-424 was incubated with HLM for 1 h and Cunninghamella elegans for up to 72 h. The HLM incubation mixtures were diluted with methanol and fungal incubation mixtures were extracted with dichloromethane and reconstituted in methanol before analyses by liquid chromatography–high-resolution mass spectrometry (LC-HRMS).

Results

HLM incubation resulted in production of ten metabolites through dihydrodiol formation, hydroxylation, and/or ipso substitution of the bromine with a hydroxy group. Fungal incubation led to production of 23 metabolites through carboxylation, dihydrodiol formation, hydroxylation, ketone formation, glucosidation and/or sulfation.

Conclusions

Generally, HLM models give good predictions of human metabolites and structural analogues are metabolised in a similar fashion. However, major hydroxy metabolites produced by HLM were those hydroxylated at naphthalene instead of pentyl moiety, the major site of hydroxylation for JWH-018. Fungal metabolites, on the other hand, had undergone hydroxylation mainly at pentyl moiety. The metabolic disagreement suggests the necessity to verify the human metabolites in authentic urine samples, while H9 and H10 (hydroxynaphthalene), H8 (ipso substitution), F22 (hydroxypentyl), and F17 (dihydroxypentyl) are recommended for monitoring of JWH-424 in urinalysis.

  相似文献   
59.
Urinary bile acids from 20 patients treated with chenodeoxycholate, 18 treated with ursodeoxycholate, 15 treated with rifampicin and 8 patients with advanced cirrhosis were analyzed by gas-liquid chromatography and gas-liquid chromatography-mass spectrometry. Occurrence rates and amounts of three so-called unusual trihydroxy bile acids, hyocholate, ursocholate and omega-muricholate, were increased in patients treated with chenodeoxycholate, ursodeoxycholate or rifampicin and decreased in cirrhotic patients as compared with those in untreated healthy adults. These data suggest that chenodeoxycholate and ursodeoxycholate are hydroxylated to produce unusual trihydroxy bile acids in bile acid-loaded humans and that this metabolism may be related to the induction of hepatic microsomal enzymes by rifampicin. In contrast, the hydroxylation of chenodeoxycholate and ursodeoxycholate may be impaired by severe hepatic damage. Because the urine is a secretory pathway for internal bile acids, the occurrence of unusual trihydroxy bile acids in the urine may be used as an indicator of hepatic ability to metabolize "hydrophobic" dihydroxy bile acids to their secretory forms.  相似文献   
60.
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