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   10105篇
  免费   737篇
  国内免费   366篇
耳鼻咽喉   53篇
儿科学   157篇
妇产科学   66篇
基础医学   860篇
口腔科学   130篇
临床医学   487篇
内科学   1222篇
皮肤病学   174篇
神经病学   363篇
特种医学   159篇
外国民族医学   2篇
外科学   1651篇
综合类   1168篇
现状与发展   1篇
预防医学   291篇
眼科学   107篇
药学   2830篇
  1篇
中国医学   1009篇
肿瘤学   477篇
  2023年   80篇
  2022年   119篇
  2021年   356篇
  2020年   250篇
  2019年   386篇
  2018年   406篇
  2017年   316篇
  2016年   258篇
  2015年   287篇
  2014年   790篇
  2013年   589篇
  2012年   548篇
  2011年   712篇
  2010年   548篇
  2009年   533篇
  2008年   502篇
  2007年   608篇
  2006年   503篇
  2005年   468篇
  2004年   392篇
  2003年   378篇
  2002年   286篇
  2001年   234篇
  2000年   182篇
  1999年   154篇
  1998年   119篇
  1997年   117篇
  1996年   88篇
  1995年   71篇
  1994年   66篇
  1993年   69篇
  1992年   54篇
  1991年   56篇
  1990年   47篇
  1989年   30篇
  1988年   30篇
  1987年   25篇
  1986年   26篇
  1985年   53篇
  1984年   56篇
  1983年   41篇
  1982年   54篇
  1981年   36篇
  1980年   46篇
  1979年   50篇
  1978年   28篇
  1977年   35篇
  1976年   38篇
  1975年   28篇
  1974年   22篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Purpose. Poorly compressible crystals of acebutolol hydrochloride were agglomerated by the spherical crystallization technique with a two-solvent system to improve the compressibility for direct tabletting. The mechanism of improvements in static compression behaviors and tablettabilities of the spherically agglomerated crystals were investigated. Methods. The improvement of static compression behaviors of the agglomerated crystals was determined by measuring the stress relaxations and elastic recoveries of compressed powder of original and agglomerated crystals. The improved tablettability of agglomerated crystals was evaluated by the pressure transmission ratio upon compression, the ejection pressure for releasing the tablet from the die and the tablet strength, i.e., tensile strength required for breaking. Results. The higher relaxation pressure and the lower elastic recovery of the agglomerated crystals than of the original crystals were found. The pressure transmission ratio data showed that the friction pressures of the two crystals were similar during the compression period. The ejection pressure of the agglomerated crystals was lower than that of the original crystals. The tensile strength of the tablet of agglomerated crystals was greater than that of the original crystals. Conclusions. The compressibility and tablettability of the spherically agglomerated crystals prepared by the spherical crystallization technique were much improved due to their increased plastic property and reduced adhesive property compared to the original crystals.  相似文献   
42.
目的:探讨原发性高血压(EH)患者血浆中肾上腺髓质素前体N端20肽(PAMP)与左室肥厚的相互关系。方法:观察62例EH患者血浆PAMP的变化以及与左室重量指数之间的关系。结果:经超声心动图检查显示,62例EH患者中伴左室肥厚者42例,无左室肥厚患者20例。EH伴左室肥厚患者血浆PAMP浓度较无左室肥厚患者明显增高(65·8±12·0)∶(60·8±9·0)ng/L,P<0·05。结论:EH患者血浆PAMP的升高可能为机体的代偿反应,有助于改善患者的预后。  相似文献   
43.
Itiswell knownthatimmune inflammatorymechanism playsanimportantroleinpsoriasis .Therelationshipbetweenchemokine ,receptorsandpsori asishasbeenconfirmed[1] .CCchemokineligand 2 0(CCL2 0 )isanewmemberinthefamilyof β chemokineandalsotheonlyligandofCCchemoki…  相似文献   
44.
A new syndrome is described in a patient with advanced renal insufficiency. This consists of severe and persistent hypotension causing weakness but associated with a clear mental status. Also present is evidence for decreased vascular reactivity. The hypotension was not orthostatic. The hypotension was associated with a circulating vasodepressor substance having the characteristics of medullipin I. The medullipin appears to have been derived from the remaining right kidney. Hypotension existed despite the presence of major prohypertensive mechanisms, including an endstage kidney, hyperreninemia and hyperaldosteronemia. It is likely that hypotension due to hypermedullipinemia is an entity occurring in the human being.  相似文献   
45.
It has been extensively proved that electro-acupuncture elicit analgesia in bothextensive areas and local region via supraspinal structures and spinal cord.The present investigationwas to study the role of P_1-purinergic receptors in the spinal mechanisms of weak electroacupuncture-induced analgesia.Leg withdrawal latency(LWL)to noxious radiant heat focused on the ankle regionwas used to assess the effects of acupuncture and that of P_1-purinergic(adenosine)receptor antago-nists,theophylline and caffeine on the electro-acupuncture(EA)analgesia.EA prolonged the LWLby 16.7%±20.3%,with an after-effect lasting about 15 min.Both theophylline and caffeineblocked the EA-induced prolongation of LWL in a dose-dependent manner at the doses of 1.6-16 mg/kg.These results suggest that P_1-purinegic receptor is involved in the spinal mechanisms of weak EAproduced analgesia in the rat.  相似文献   
46.
AIM: The aim of this pilot study was an investigation on photodynamic therapy (PDT) whether it is a good alternative for treating periungual and subungual warts of the hands. STUDY DESIGN: Twenty patients (mean age: 30.5 years) with a total of 40 periungual and subungual warts were treated with PDT. A photosensitizer, 20%delta-aminolevulinic acid was applied on the warts. After a mean incubation time of 4.6 h (SD: 1.2), the warts were irradiated with the VersaLight for 5-30 min (15.2 +/- 4.3 min). RESULTS: After a mean of 4.5 treatments a mean clearance of 100% was achieved in 90% of the patients. One patient (5%) showed a clearance of 50% and another showed no improvement. The subungual or periungual location of the wart had no influence on the number of treatments or end result (P > 0.05). There were two recurrences during the mean follow-up period of 5.9 months (SD: 7.6). Besides mainly pain and hyperpigmentation, most treatments had no side-effects. CONCLUSION: PDT can offer a good alternative for treating periungual warts of the hands. Larger studies are indicated.  相似文献   
47.
目的:研究急性脊髓损伤合并内毒素攻击时小鼠脊髓组织中锌脂蛋白A20的表达规律.方法:将健康昆明种小白鼠225只(雌雄不拘,体重18~24g)随机分为4组:正常对照组(N组,n=9),单纯尾静脉注射生理盐水0.1ml;脊髓损伤组(A组,n=72),按改良Allen's法制作T10-T11节段脊髓损伤模型;内毒素组(B组,n=72),不进行脊髓损伤只行尾静脉注射内毒素(5mg/kg)0.1ml;脊髓损伤合并内毒素注射组(C组,n=72),制作脊髓损伤模型后再行尾静脉注射内毒素(5mg/kg)0.1ml.A、B、C组分别于处理后0.5、1、2、4、8、12、24、48h,N组于处理后48h,取T10~T11节段脊髓组织.以HE染色观察脊髓损伤程度.以免疫组化(IHC)、逆转录-聚合酶链式反应(RT-PCR)技术分别检测脊髓组织中A20蛋白及mRNA表达.结果:HE染色显示N组和B组各时相点脊髓组织无明显变化;A组打击后0.5h即出现染色质凝聚,染色变深,细胞核偏位、核固缩等现象,神经细胞肿胀,可见片状出血,炎性细胞浸润;至打击8h后可见到核仁消失、核碎裂、核溶解,鬼影细胞现象;C组较A组脊髓损伤更为明显,8h除可见核固缩、碎裂、溶解外,还可见到细胞自溶、空泡形成,并随损伤时间的延长而逐渐加重.IHC显示N组未见A20蛋白阳性表达,A、B组未见或仅有少量A20蛋白阳性表达,C组2h时少量表达,8h表达达高峰.RT-PCR示N组A20 mRNA呈微量表达;A组与N组比较表达升高,与B、C组比较表达高峰延迟,且在12~24h表达高于B、C组;B组在注射内毒素后0.5h,锌脂蛋白A20 mRNA较N组升高明显,1~2h为A20 mRNA表达的高峰期;C组锌脂蛋白A20 mRNA表达最明显,表达高峰在1~8h.结论:在脊髓损伤的早期就出现神经细胞变性死亡的进行性加重,同时伴有锌脂蛋白A20表达增高,合并内毒素注射时尤其明显,锌脂蛋白A20可能对于渊控脊髓损伤的炎症反应具有重要意义.  相似文献   
48.
火把花根片对哮喘豚鼠气道炎症抑制作用的实验研究   总被引:3,自引:0,他引:3  
目的 研究火把花根片对哮喘豚鼠气道炎症的作用。方法 建立哮喘豚鼠动物模型。豚鼠17只随机分为2组,即对照组(8只)和火把花根组(9只)。测定支气管肺泡灌洗液(BAIF)细胞总数、嗜酸性粒细胞、淋巴细胞、中性粒细胞数量及蛋白浓度,图像分析软件测定气道壁厚度及腺体厚度。结果 火把花根组BAIF细胞总数、嗜酸性较细胞为主的炎性细胞数量及蛋白浓度均低于对照组(P<0.01),图像分析表明火把花根组气道壁厚度及腺体厚度均较对照组减低(P<0.01)。结论 火把花根片可抑制哮喘豚鼠的气道慢性炎症,对支气管哮喘有治疗作用。  相似文献   
49.
Introduction Postoperative treatment for colorectal cancer depends on tumor stage as defined by the International Union Against Cancer (UICC). Adjuvant chemotherapy is not recommended in patients without lymph node involvement (UICC stages I and II). As many as 20–30% of these patients, however, will develop recurrence. Aims and objectives We conducted this study to determine the presence of disseminated tumor cells in the lymph nodes by quantitative real-time polymerase chain reaction (QRT-PCR) for cytokeratin 20 (CK20) in an attempt to provide supplementary information compared to histopathological findings. Materials and methods Using a standard QRT-PCR assay, we examined primary tumors and 391 lymph nodes from 31 patients with completely resected colorectal cancer. Results Of the 31 primary tumors, 29 were positive for CK20 by QRT-PCR. Discussion An examination of the lymph nodes from the 29 patients with CK20-positive primary tumors revealed that 35 (92.1% sensitivity) of the 38 histopathologically positive lymph nodes and 54 (16.7%) of the 324 histopathologically negative lymph nodes were positive by molecular analysis. CK20 expression was detected in 10 (100%) of 10 patients with a histopathologically positive lymph node status (pN1). In 9 (47.4%) of 19 patients with negative histopathological results (pN0), we detected a CK20 mRNA signal in at least one lymph node. Whereas eight patients with histopathologically negative lymph nodes could be upstaged on the basis of the molecular findings, no patient would be downstaged. Conclusion Our results suggest that QRT-PCR for CK20 is a useful tool for the quantitative detection of micrometastases in the regional lymph nodes. We introduce a standardized procedure that integrates a molecular diagnostic technique in the clinical staging.  相似文献   
50.
Deletions of chromosome 20q are associated with myeloid malignancies and have been previously shown to arise in a multipotent progenitor of both myeloid and B cells. However, B-cell differentiation from the abnormal progenitor was impaired. The CD40 antigen is a surface glycoprotein which is expressed in B cells and haemopoietic stem cells and is important for B-cell growth and development. Following the recent mapping of CD40 to chromosome 20q we sought to determine its position relative to 20q deletions. Analysis of lymphoblastoid cell lines carrying 20q deletions placed CD40 within a 19–21 cM interval which is almost coincidental with the common deleted region defined by previous analysis of patient samples. Our results raise the possibility that genetic alteration of this locus may contribute to the pathogenesis of myeloid disorders associated with 20q deletions.  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