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   1756篇
  免费   99篇
  国内免费   31篇
耳鼻咽喉   17篇
儿科学   12篇
妇产科学   26篇
基础医学   216篇
口腔科学   26篇
临床医学   151篇
内科学   469篇
皮肤病学   96篇
神经病学   124篇
特种医学   56篇
外科学   255篇
综合类   6篇
一般理论   1篇
预防医学   71篇
眼科学   48篇
药学   133篇
中国医学   5篇
肿瘤学   174篇
  2023年   8篇
  2022年   18篇
  2021年   36篇
  2020年   28篇
  2019年   25篇
  2018年   41篇
  2017年   31篇
  2016年   56篇
  2015年   59篇
  2014年   50篇
  2013年   95篇
  2012年   144篇
  2011年   115篇
  2010年   75篇
  2009年   62篇
  2008年   129篇
  2007年   134篇
  2006年   148篇
  2005年   127篇
  2004年   100篇
  2003年   106篇
  2002年   96篇
  2001年   12篇
  2000年   3篇
  1999年   8篇
  1998年   20篇
  1997年   12篇
  1996年   16篇
  1995年   15篇
  1994年   16篇
  1993年   5篇
  1992年   13篇
  1991年   4篇
  1990年   6篇
  1989年   8篇
  1988年   8篇
  1987年   6篇
  1986年   6篇
  1985年   8篇
  1984年   8篇
  1983年   4篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1977年   2篇
  1938年   1篇
  1936年   1篇
  1912年   1篇
  1909年   2篇
  1908年   1篇
排序方式: 共有1886条查询结果,搜索用时 31 毫秒
91.
92.
The congenital cystic dilatation of the liver and bile ducts (CDB) is a very uncommon disease. It often appears in females and most frequently in paediatric patients. Its etiopathogenesis is not yet completely defined. Its evolution includes, together with several complications, the malignant transformation. The Authors present the outcomes of their experience based on a series of 5 patients observed from 1991 till today. Apart from the rarity of this disease, their series is so interesting because 4 out of 5 are adult patients and the fifth one is over 15. In addition, differentiating from the literature trend, the group included only male patients. Are also discussed the most important aspects referring to nosology, epidemiology, etiopathogenesis, clinical pattern and its evolution of CDB, looking over a wide review too. The Authors extensively examine the diagnostic problems; owing to that the patients were observed in the period 1991-1999 it is necessary to clarify that some imaging methods, i.e. CSTscan and the bile duct MNR, were not yet introduced. The surgical treatment has been investigated as well, developed during its historical evolution until nowadays and our solutions for the 5 cases have been presented and discussed. In their series the Authors haven't ever observed during hospitalisation a malignant transformation.  相似文献   
93.
BACKGROUND: Clinical depression has been increasingly recognized as an independent risk factor for adverse cardiovascular events, but the biological mechanisms of this association remain unclear. Recent evidence for renin system dysregulation in patients with depression led us to hypothesize that aldosterone--a well-recognized contributor to vascular injury--could be increased in depressed patients. The present study was designed, therefore, to be a cross-sectional investigation of plasma renin and aldosterone levels in depressed patients as compared with healthy controls with no history of psychiatric illness. METHODS: A total of 65 depressed patients and 65 age- and gender-matched control subjects were enrolled. Following a fixed sodium and potassium diet, venous blood samples were obtained at 9:00 a.m. to avoid the influence of circadian rhythms. RESULTS: Although there were no significant differences in plasma level of renin among subjects with depression and controls (7.9 +/- 5.8 vs. 6.4 +/- 4.3 pg/mL, respectively; p=0.10), depressed subjects exhibited greater mean aldosterone levels as compared with control subjects (157.2 +/- 67.5 vs. 125.7 +/- 38.1 pg/mL, respectively; p=0.0014). After adjusting for potential confounders, multivariate logistic regression analysis showed that subjects with depression had 2.77 times higher odds of elevated aldosterone levels compared with healthy control subjects (95% confidence interval, 1.30-5.92, p=0.008). CONCLUSIONS: Our present findings support the hypothesis that hyperaldosteronism could be a common feature among depressed patients, thereby suggesting that increased aldosterone levels may act as a mediator in the pathway linking depression to unfavorable vascular events.  相似文献   
94.
Effect of toxic cations on copper rhizotoxicity in wheat seedlings   总被引:2,自引:0,他引:2  
Copper pollution may occur in acidic soils where the low pH leads to release of Al and Mn in soil solution, which could interact with Cu toxicity. Very little information exists regarding the influence of toxic cations on the phytotoxicity of Cu. In this study, we tested the hypothesis that phytotoxicity of Cu2+ may be overestimated in acidic soils due to synergism between Al or Mn and Cu toxicity. Rhizotoxicity of Al, Mn, and Cu to wheat seedlings was studied in well-defined nutrient solutions, with these elements present singly or in combination. Toxicity was expressed on a solution metal-activity basis, with metal activities calculated using GEOCHEM-PC and verified using Donnan dialysis. Of the three ions, Cu2+ was the most rhizotoxic, with activities of Cu2+, Al3+, and Mn2+ resulting in a 25% reduction in root elongation of 0.12, 1.26, and 211 microM, respectively. Although there was no interaction between Mn2+ and Cu2+ toxicity, Cu2+ was significantly less toxic on a relative basis in the presence of Al3+. Thus, critical thresholds for soil solution Cu2+ activity determined in acidic soils will be underprotective compared to soils that contain low concentrations of soluble Al (e.g., limed or nonacidic soils).  相似文献   
95.
96.
BACKGROUND: The development of MALDI Imaging Mass Spectrometry is a promising technique in the investigation of biological molecular repertoire. We have pursued an analytical assessment of this technique in its application to proteome analysis. METHODS: A specific statistical method of analysis has been developed to enable data processing in the absence of internal standards, by defining similarity scores. RESULTS: The investigated linear mode MALDI-TOF set-up allows to obtain data variations comprised within the 30% of variation when assaying tissues samples from the same animal, while the 60% of variation was highlighted in the inter-mice series assaying syngenic animals. CONCLUSIONS: This analytical assessment represents the first step of a process that should validate the utilisation of this technique in the clinical practice.  相似文献   
97.
Mutations of the GNE gene are responsible for autosomal recessive hereditary inclusion-body myopathy (HIBM). In this study we searched for the presence of any significant abnormality of alpha-dystroglycan (alpha-DG), a highly glycosylated component of the dystrophin-glycoprotein complex, in 5 HIBM patients which were previously clinically and genetically characterized. Immunocytochemical and immunoblot analysis showed that alpha-DG extracted from muscle biopsies was normally expressed and displayed its typical molecular mass. Immunoblot analysis on the wheat germ lectin-enriched glycoprotein fraction of muscles and primary myotubes showed a reduced amount of alpha-DG in 4 out of 5 HIBM patients, compared to normal and other diseased muscles. However, such altered lectin-binding behaviour, possibly reflecting a partial hyposialylation of alpha-DG, did not affect the laminin binding properties of alpha-DG. Therefore, the subtle changes within the alpha-DG glycosylation pattern, detected in HIBM muscles, likely do not play a key pathogenic role in this disorder.  相似文献   
98.
Recombinant human nerve growth factor (rhNGF) is regarded as the most promising therapy for neurodegeneration of the central and peripheral nervous systems as well as for several other pathological conditions involving the immune system. However, rhNGF is not commercially available as a drug. In this work, we provide data about the production on a laboratory scale of large amounts of a rhNGF that was shown to possess in vivo biochemical, morphological, and pharmacological effects that are comparable with the murine NGF (mNGF), with no apparent side effects, such as allodynia. Our rhNGF was produced by using conventional recombinant DNA technologies combined with a biotechnological approach for high-density culture of mammalian cells, which yielded a production of approximately 21.5 +/- 2.9 mg/liter recombinant protein. The rhNGF-producing cells were thoroughly characterized, and the purified rhNGF was shown to possess a specific activity comparable with that of the 2.5S mNGF by means of biochemical, immunological, and morphological in vitro studies. This work describes the production on a laboratory scale of high levels of a rhNGF with in vitro and, more important, in vivo biological activity equivalent to the native murine protein.  相似文献   
99.
100.
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