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   45345篇
  免费   4230篇
  国内免费   1708篇
耳鼻咽喉   300篇
儿科学   899篇
妇产科学   1351篇
基础医学   9673篇
口腔科学   1666篇
临床医学   3659篇
内科学   4772篇
皮肤病学   1243篇
神经病学   2839篇
特种医学   1073篇
外国民族医学   20篇
外科学   3135篇
综合类   6789篇
现状与发展   12篇
一般理论   13篇
预防医学   3379篇
眼科学   933篇
药学   5186篇
  19篇
中国医学   1052篇
肿瘤学   3270篇
  2024年   30篇
  2023年   477篇
  2022年   696篇
  2021年   1476篇
  2020年   1282篇
  2019年   1329篇
  2018年   1305篇
  2017年   1419篇
  2016年   1502篇
  2015年   1539篇
  2014年   2398篇
  2013年   3326篇
  2012年   2394篇
  2011年   2628篇
  2010年   2277篇
  2009年   2083篇
  2008年   2064篇
  2007年   2211篇
  2006年   2079篇
  2005年   1893篇
  2004年   1761篇
  2003年   1587篇
  2002年   1340篇
  2001年   1179篇
  2000年   1015篇
  1999年   901篇
  1998年   900篇
  1997年   842篇
  1996年   789篇
  1995年   750篇
  1994年   657篇
  1993年   612篇
  1992年   539篇
  1991年   495篇
  1990年   373篇
  1989年   382篇
  1988年   320篇
  1987年   240篇
  1986年   217篇
  1985年   384篇
  1984年   323篇
  1983年   224篇
  1982年   252篇
  1981年   201篇
  1980年   157篇
  1979年   100篇
  1978年   100篇
  1977年   63篇
  1976年   66篇
  1975年   33篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
目的:探讨活性氧(ROS)对人类精子线粒体tRNALeuUUR基因的氧化损伤。方法:采用Percoll梯度离心法筛选具有正常生理功能的精子,作为正常精子模型,并分为损伤组20例和对照组20例,分别加入次黄嘌呤-黄嘌呤氧化酶体系或不予处理,37℃有氧环境中孵育60min。分别提取精子DNA,以Fpg酶切损伤碱基并采用接头介导PCR(LM-PCR)检测线粒体tRNALeuUUR基因的氧化损伤。采用Rhodamine(Rh123)荧光探针标记精子,通过流式细胞仪检测线粒体膜电位,观察精子的功能。结果:与对照组相比,损伤组精子孵育后线粒体膜电位明显降低[(116.27±11.72)%vs(64.00±4.88)%,P<0.05]。Fpg酶切和LM-PCR显示精子线粒体tRNALeuUUR基因损伤。结论:ROS可能通过对精子线粒体tRNALeuUUR基因氧化损伤而影响精子功能(线粒体膜电位明显降低),从而引起不育。  相似文献   
32.
正常生育男性成熟精子mRNA的种类和特征   总被引:1,自引:0,他引:1  
目的:剖析具有正常生育能力男性成熟精子mRNA的种类和丰度。方法:健康并育有后代的成年男性10例,禁欲1周后取精液,上游法优化精子,Trizol试剂提取精子总RNA。混合所有总RNA进行基因表达系列分析(SAGE)。结果:所建SAGE文库共获877个克隆,测序得到21 052个标签,出现两次以上的独特性标签有2 712种。经与SAGEm ap数据库比对,19.7%的独特性标签没有基因匹配,代表新基因;其余能匹配的基因中,67%具有蛋白质结合或核酸结合能力,41%具有催化活性,13%与信号转导有关,与细胞运输、精子结构、转录调节相关者分别达到10%左右。结论:人成熟精子中存在数量庞大、种类繁多的mRNA。  相似文献   
33.
This article presents first systematical procedure results on traditional usage of wild, edible, vitaminous, and aromatic plants in the nutrition of human population in Bosnia and Herzegovina (W. Balkan peninsula; SE Europe). By method of an ethnobotanical interview, which comprised of over 250 persons, whose average age was 55, and by research on edible wild flora all around Bosnia and Herzegovina that extended over many years, detected were 308 plants belonging to 73 plant families that are being used in nutrition and diet of indigenous population. Edible wild plants are used as delicious vegetables, fruits, peer and spices, in either fresh, raw, or dried condition. Plants are being used for the making of cooked food (33%), fresh salads (19%), mush and bread (17%), or as fresh, wild fruits and drinks (13%) or as spices and ethno-pharmacological potions (10%). The majority of identified, wild edible plants may satisfy the daily human need for elementary nutrition material, particularly those of vitamins C and A, and for some minerals, according to the regulations of World Health Organization (WHO).  相似文献   
34.
目的 观察重组人白介素-1受体拮抗剂(rhIL-1Ra)的毒性靶器官及毒性的严重程度.方法 32只成年恒河猴分为rhIL-1Ra 2mg/(kg·d)(n=6)、10mg/(kg·d)(n=6)和50mg/(kg·d)(n=6)连续给药90天组,10mg/(kg·d)(n=4)连续给药30天组,正常对照组(n=5)和溶剂对照组(n=5).rhIL-1Ra为皮下注射给药,每日1次.观察指标包括一般药物反应、尿八项、心电图、眼底检查、外周血细胞计数及白细胞分类、凝血时间、血清生化、外周血T细胞亚群和猴抗rhIL-1Ra抗体测定、脏器重量和脏器系数、常规病理组织学检查.结果 给药后30天各给药组动物血清非特异性抗体明显升高.rhIL-1Ra 2mg/(kg·d)组其他检测指标均未见明显地改变.rhIL-1Ra 10mg/(kg·d)组给药后90天肾小球毛细血管基底膜明显增厚,但此剂量给药时间为30天时未见任何异常.rhIL-1Ra 50mg/(kg·d)组肾小球及肾小管中蛋白性液体量多,小球毛细血管基底膜增厚更为严重,且停药30天后基底膜增厚程度仍未见明显减轻或改善.结论 rhIL-1Ra的主要毒性靶器官为肾脏,2mg/(kg·d)为安全剂量,10mg/(kg·d)给药30天时为安全剂量,给药90天为恒河猴中毒性剂量,而50mg/(kg·d)为明显的毒性反应剂量,可产生难以恢复的肾脏纤维化.  相似文献   
35.
Cidofovir is an acyclic nucleoside phosphonate with broad-spectrum activity against DNA viruses, including human papilloma virus (HPV). However, data on the efficacy of cidofovir in an immunosuppressive setting remain contradictory. We report for the first time on the promotion of the healing of recalcitrant warts in a patient with myelodysplastic syndrome with intravenous cidofovir treatment.  相似文献   
36.
We report the case of a patient with a 13-year history of pemphigus vulgaris (PV) treated with immunosuppressive agents, prednisone and mycophenolate mofetil who had developed lesions of Kaposi's sarcoma (KS) on a sole plaque of PV that had been previously treated with intralesional injections of steroids. The lesions were surgically removed and polymerase chain reaction (PCR) demonstrated human herpesvirus-8 (HHV-8) DNA. There were neither recurrences nor later dissemination of KS following gradual decrease of the immunosuppressive therapy. We suggest that the treatment with intralesional steroids may have influenced the local reactivation of a latent infection of the virus, determining the appearance of this localized KS.  相似文献   
37.
Abstract: The adsorptive characteristics of 5 dialysis membranes for recombinant human erythropoietin (EPO) were studied in vitro in a closed circuit system. For 120 min, EPO added with bovine serum was significantly adsorbed by polymethylmetacrylate (PMMA) and polyacry–lonitrile (PAN) membranes but not by Cuprophan, ethylene vinyl alcohol (EVAL), or polysulfone (PS) membranes. In addition the EPO adsorptive rate, as well as that of β2–microglobulin (β2–MG), was greater with a PMMA membrane than with a PAN membrane. EPO was not detected in the ultrafiltrate at 15 min with 5 membranes. These results indicate that EPO was eliminated by membrane adsorption only with some dialysis membranes.  相似文献   
38.
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) of the human motor cortex produce a silent period (SP) following motor evoked potentials (MEPs). The early part of the SP can be explained by decreased alpha motor neuron excitability, whereas the late part is presumably due to suprasegmental mechanisms. In order to determine the level of the suprasegmental contribution to the generation of SPs, we recorded excitatory and inhibitory responses to TMS, TES, and percutaneous electrical brainstem stimulation (PBS) in the voluntarily activated first dorsal interosseous muscle of the hand. Stimulus intensities were set so that PBS and TES induced MEPs with areas equal to or larger than those of MEPs obtained with TMS. This procedure revealed that SPs were 49% and 83% shorter with TES and PBS, respectively, than with TMS. As TMS is more effective than TES or PBS in activating cortical interneurons, these findings support the idea that a significant component of the SP arises from intracortical mechanisms.  相似文献   
39.
目的 通过测定生长激素缺乏症 (GHD)患儿用国产重组人生长激素 (recom bined hum angrowth horm one,rh GH)治疗时血清生长激素抗体 (GH- Ab)水平及其结合特性 ,探讨 rh GH的免疫原性及其对疗效的影响。方法 对 6 1例 (男 49例 ,女 12例 ) GHD患儿用国产 rh GH治疗 ,每晚睡前皮下注射 rh GH 0 .1IU /kg共6个月 ;用放射免疫法测定治疗期间患儿血清 GH- Ab水平和滴度 ,并计算抗体结合容量、亲和常数 (Ka)。结果 48%患儿 (2 9/6 1)用药后 3个月血清 GH - Ab呈阳性至试验结束时仍未消失 ,其中 2 0例抗体为弱阳性 (结合率 <10 % ) ,9例呈强阳性 (结合率 >15 % ) ;5 2 %患儿 (32 /6 1)治疗期间抗体为阴性 ;血清 GH- Ab的结合容量、Ka及滴度均为低水平 ,分别为 (0 .1~ 4.8) pmol/L、(1.7× 10 7~ 6 .5× 10 8) L /mol和 1∶ 4~ 1∶ 8。GH- Ab阳性患儿治疗后的身高、身高增长速率及身高落后于正常 SD值的变化与同期阴性者比较无统计学差异 (P>0 .0 5 )。结论 本试验所用国产 rh GH对 GHD患儿身高增长具有确切的促进作用 ,其免疫原性所导致产生的 GH - Ab未对患儿体格线性增长产生负性影响  相似文献   
40.
Ultraviolet radiation B (UVB) on the skin induces erythema, inflammation and modifications of the immune system. These changes have been reported after excessive short-term or long-term exposure to broad spectrum UVB. In this study, we examined the effects of local repetitive UVB irradiation of 311 nm wavelength on the skin of seven young volunteers. Skin biopsies were taken before and after UVB irradiation, and we immunohistochemically analyzed the expression of CD1a and HLA-DR antigens of Langerhans cells (LC), the possible infiltration of dermis/epidermis by CD11b macrophages, the modifications or the induction of intercellular adhesion molecule-1 (ICAM-1), E-selectin and vascular cell adhesion molecule-1 (VCAM-1) involved in the binding of leukocytes to the endothelial surface and the development of perivascular infiltrates of LFA-1+ mononuclear cells. We also determined the expression of substance P receptors (SPR) using biotinylated substance P (SPB). Exposure of UVB 311 nm induced a drastic reduction of CD1a+ cells and a moderate increase of HLA-DR+ dendritic cells in the epidermis without infiltration by CD11b macrophages. An increase of the binding of SPB to upper layer epidermal cells was noted in five of seven biopsies. In the dermis, vessel-associated ICAM-1 expression increased and an induction of E-selectin occurred on nearly 20 to 40% of endothelial cells, but VCAM-1 expression remained undetectable. The percentage of LFA-1+ cells did not change significantly after irradiation. These observations may be compatible with a selective role of UVB 311 nm on the skin immune response.  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