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   6311篇
  免费   328篇
  国内免费   46篇
耳鼻咽喉   58篇
儿科学   204篇
妇产科学   84篇
基础医学   985篇
口腔科学   146篇
临床医学   452篇
内科学   1459篇
皮肤病学   149篇
神经病学   566篇
特种医学   195篇
外科学   549篇
综合类   37篇
一般理论   1篇
预防医学   236篇
眼科学   234篇
药学   561篇
中国医学   13篇
肿瘤学   756篇
  2023年   41篇
  2022年   89篇
  2021年   131篇
  2020年   82篇
  2019年   132篇
  2018年   155篇
  2017年   127篇
  2016年   163篇
  2015年   168篇
  2014年   188篇
  2013年   240篇
  2012年   333篇
  2011年   422篇
  2010年   240篇
  2009年   215篇
  2008年   406篇
  2007年   428篇
  2006年   363篇
  2005年   438篇
  2004年   417篇
  2003年   406篇
  2002年   331篇
  2001年   75篇
  2000年   60篇
  1999年   88篇
  1998年   79篇
  1997年   63篇
  1996年   75篇
  1995年   52篇
  1994年   47篇
  1993年   46篇
  1992年   62篇
  1991年   42篇
  1990年   42篇
  1989年   42篇
  1988年   39篇
  1987年   43篇
  1986年   26篇
  1985年   29篇
  1984年   26篇
  1983年   36篇
  1982年   21篇
  1981年   20篇
  1980年   16篇
  1979年   18篇
  1978年   13篇
  1977年   10篇
  1976年   12篇
  1974年   17篇
  1970年   10篇
排序方式: 共有6685条查询结果,搜索用时 15 毫秒
61.
62.
We report on a 6-year-old boy with de novo 46, XY, del(3)(q12q23) and bilateral blepharo-phimosis, ptosis, epicanthus inversus, in addition to multiple other anomalies. Since 4 previously reported cases of interstitial deletion of 3q involving 3q23 band are clinically similar, we propose this blepharophimosis sequence due to 3q23 deletion as a further “contiguous gene syndrome”.  相似文献   
63.
The pathogenesis of progressive bile duct loss in primary biliary cirrhosis remains unclear. In this study, the involvement of cellular senescence of biliary epithelial cells was examined in liver tissue samples from patients with primary biliary cirrhosis (n = 33), and compared with control diseased and normal livers (n = 83). In addition, cellular senescence was induced by oxidative stress in cultured mouse biliary epithelial cells. Biliary epithelial cells in small bile ducts in primary biliary cirrhosis, especially those in patients presenting with chronic non-suppurative cholangitis, frequently expressed senescence-associated beta-galactosidase, and senescence-associated p16(INK4) and p21(WAF1/CIP). In contrast, senescence-associated markers were rarely expressed in small bile ducts in control livers. The infiltration of myeloperoxidase-positive inflammatory cells into biliary epithelial cell layers was closely associated with the cellular senescence of biliary epithelial cells in early-stage PBC. Cellular senescence of cultured mouse biliary epithelial cells was induced by treatment with H2O2 via the p38MAPK-dependent pathway and nitric oxide-augmented H2O2-induced cellular senescence. Oxidative stress- and nitric oxide-mediated cellular senescence may be involved in bile duct lesions, which are followed by progressive bile duct loss in primary biliary cirrhosis.  相似文献   
64.
65.
66.
Human bone marrow-derived mesenchymal cells contain mesenchymal stem cells (MSCs), which are well known for their osteo/chondrogenic potential and can be used for bone reconstruction. This article reports the viability of cryopreserved human mesenchymal cells and a comparison of the osteogenic potential between noncryopreserved and cryopreserved human mesenchymal cells with MSC-like characteristics, derived from the bone marrow of 28 subjects. The viability of cryopreserved mesenchymal cells was approximately 90% regardless of the storage term (0.3 to 37 months). It is clear by fluorescence-activated cell sorter analysis that the cell surface antigens of both noncryopreserved and cryopreserved mesenchymal cells were negative for hematopoietic cell markers such as CD14, CD34, CD45, and HLA-DR but positive for mesenchymal characteristics such as CD29 and CD105. To monitor the osteogenic potential of the cells, such as alkaline phosphatase (ALP) activity and in vitro mineralization, a subculture was conducted in the presence of dexamethasone, ascorbic acid, and glycerophosphate. No difference in osteogenic potential was found between cells with or without cryopreservation treatment. In addition, cells undergoing long-term cryopreservation (about 3 years) maintained high osteogenic potential. In conclusion, cryopreserved as well as noncryopreserved human mesenchymal cells could be applied for bone regeneration in orthopedics.  相似文献   
67.
N-(3,4-Dimethoxycinnamoyl) anthranilic acid (N-5') is an inhibitor of IgE-mediated histamine release from mast cells. To elucidate inhibition mechanism, effects of N-5' were examined under various conditions using peritoneal exudate cells and isolated mast cells of rats. N-5' inhibited histamine release induced by antigen, ionophore A23187, ATP, dextran and phospholipase A2. But the release induced by compound 48/80 or ionophore X537A was not inhibited. Influx of Ca++ into mast cells and ATP consumption were inhibited. Based on these results, it is presumed that N-5' interferes with the energy-requiring system and/or Ca++ influx resulting in the inhibition of histamine release.  相似文献   
68.
OBJECTIVE: Saliva secretion is mediated by cAMP and the calcium signaling pathway in salivary acinar cells. The PKA signaling pathway plays an important role in protein secretion through the activation of cAMP, in fluid secretion through the elevation of intracellular calcium and in the activation of cAMP response element-binding protein (CREB), which is involved in these signaling cascades. In this study, we investigated whether the activation of CREB plays a part in the salivary secretion in mice. METHODS: We examined CREB activation by assessing phosphorylation at the serine-133 position using Western blotting. RESULTS: Carbachol (a muscarinic acetylcholine agonist) and isoproterenol (a beta-adrenergic agonist) markedly activated CREB in parotid acinar cells. Carbachol and isoproterenol-induced CREB phosphorylation was blocked by atropine (a muscarinic acetylcholine antagonist) and propranolol (a beta-adrenergic antagonist), respectively. The PKA inhibitor H89 inhibited CREB activation, but the PLC inhibitor U73122 did not. Moreover, carbachol- and isoproterenol-stimulated amylase secretion from parotid acinar cells was inhibited by H89 and adenoviral dominant-negative CREB. CONCLUSION: These results indicate that the muscarinic and beta-adrenergic activation of CREB was mediated through the PKA pathway and that CREB is involved in protein secretion from parotid acinar cells.  相似文献   
69.
The effect of prednisolone on the substance P (SP)-induced vascular permeability increase in male ddY, WBB6 F1–+/+ (control) and WBB6 F1-W/Wv (no mast cell in skin or internal organs) mice was investigated. 1) SP (1–10 000 pg/site) increased vascular permeability in ddY, WBB6 F1–+/+ and WBB6 F1-W/Wv mice ears. 2) SP (100 pg/site)-induced vascular permeability was inhibited by prednisolone (10 mg/kg) administered intraperitoneally 3 to 12 hours prior to the elicitation of the reaction in ddY mice. When dexamethasone at a dose of 1 mg/kg was administered intraperitoneally 2 to 24 hours prior to the elicitation of the reaction, significant inhibition was observed. When prednisolone was administered intraperitoneally 8 hours prior to the elicitation of the reaction, the SP-induced capillary permeability increase in both ddY and WBB6 F1-W/Wv mice was clearly inhibited by the drug at doses of 5 and 10 mg/kg. 3) Diphenhydramine (1 and 10 mg/kg) inhibited SP-induced vascular reaction in ddY mice but not in WBB6 F1-W/Wv mice. 4) Atropine (10 mg/kg) inhibited SP-induced vascular reaction in both ddY and WBB6 F1-W/Wv mice. But acetylcholine did not cause an increase of vascular permeability in ddY and WBB6 F1-W/Wv mice ears. 5) Prednisolone (5 mg/kg) inhibited histamine- and serotonin-induced vascular permeability in ddY and WBB6 F1-W/Wv mice ears. 6) Prednisolone (5 and 10 mg/kg) inhibited the SP-induced histamine release from ddY mice peritoneal mast cells. These results suggest that the vascular effect of SP is mediated by both mast cell dependent (release of histamine from mast cells) and mast cell independent mechanisms. Prednisolone inhibits the SP-induced vascular permeability mediated by both mechanisms in mice.  相似文献   
70.
In this report, we provide evidence using a serial bone marrow transplantation (BMT) protocol that intra-bone marrow (IBM)-BMT (IBM-BMT) can efficiently reconstitute the hemopoietic system with cells of donor origin, in contrast to conventional intravenous (IV)-BMT (IV-BMT). Furthermore, the hematolymphoid system of secondary recipients that had received bone marrow cells (BMCs) from primary recipients treated with IBM-BMT recovered earlier than that of the secondary recipients of BMCs from primary recipients treated with IV-BMT. This was the case when the Lin-/c-kit+ progenitor cells of the secondary and tertiary recipients were examined. These findings indicate that IBM-BMT can facilitate the development of not only cells of various lineages but also the effective generation and, more importantly, the maintenance of the progenitor cells. Furthermore, we show that IBM-BMT can reconstitute the dendritic cell (DC) subsets (myeloid and lymphoid DCs), which are critical for the initiation of both adaptive and innate immune responses. The frequency of both myeloid and lymphoid DC subsets was approximately equal to that of normal age-matched untreated controls and, after second and third BMT, this ratio was close to that observed in the normal controls. However, the lymphoid DCs were clearly reduced in the secondary and tertiary recipients of BMCs from mice that had received IV-BMT. Therefore, the development of DC subsets is also normally maintained in the IBM-BMT group.  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