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   72389篇
  免费   6953篇
  国内免费   4603篇
耳鼻咽喉   682篇
儿科学   958篇
妇产科学   788篇
基础医学   7499篇
口腔科学   1333篇
临床医学   8258篇
内科学   10077篇
皮肤病学   821篇
神经病学   3620篇
特种医学   2724篇
外国民族医学   20篇
外科学   8468篇
综合类   13528篇
现状与发展   13篇
一般理论   7篇
预防医学   5579篇
眼科学   1582篇
药学   7674篇
  71篇
中国医学   4696篇
肿瘤学   5547篇
  2024年   213篇
  2023年   859篇
  2022年   2078篇
  2021年   2974篇
  2020年   2350篇
  2019年   2041篇
  2018年   2156篇
  2017年   2179篇
  2016年   2080篇
  2015年   3035篇
  2014年   3725篇
  2013年   3966篇
  2012年   5508篇
  2011年   6022篇
  2010年   4635篇
  2009年   3948篇
  2008年   4453篇
  2007年   4320篇
  2006年   4159篇
  2005年   3625篇
  2004年   3219篇
  2003年   3238篇
  2002年   2938篇
  2001年   2153篇
  2000年   1610篇
  1999年   1201篇
  1998年   743篇
  1997年   677篇
  1996年   511篇
  1995年   475篇
  1994年   383篇
  1993年   274篇
  1992年   277篇
  1991年   269篇
  1990年   207篇
  1989年   180篇
  1988年   167篇
  1987年   141篇
  1986年   118篇
  1985年   131篇
  1984年   74篇
  1983年   43篇
  1980年   34篇
  1979年   53篇
  1978年   34篇
  1976年   37篇
  1975年   39篇
  1974年   54篇
  1973年   39篇
  1971年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
癌基因c-fos、c-jun蛋白在鳞状细胞癌皮损中的表达及意义   总被引:3,自引:0,他引:3  
目的 探讨癌基因c fos、c jun的表达与皮肤鳞癌发生和发展的关系。 方法 采用免疫组化法对 6 0例皮肤鳞癌的c fos、c jun的表达情况进行检测 ,并与正常皮肤组织进行对照。 结果 c fos、c jun在正常皮肤组织不表达 ,在皮肤鳞癌中的表达阳性率分别为 6 1.7%和 4 8.3% ,其表达水平与癌组织的分化程度有关 (P <0 .0 5 ) ,肿瘤的分化程度越高其表达水平越高。 结论 c fos、c jun的表达水平可作为判定皮肤鳞癌分化的指标。  相似文献   
52.
A 12-year-old girl with a history of fast myopia progression underwent advanced orthokeratology (ortho-k) treatment and suffered from recurrent lens binding and central corneal staining. The problem could not be fixed by lens fenestration and refitting with a less aggressive lens (three-zone ortho-k) design. After refitting with a lower target advanced ortho-k lens, these complications were no longer occurring, and the amount of power reduction was greater than expected considering the target designed for the refitted lenses. During the following 15 months of ortho-k lens wear, there was no clinically significant change to her refractive error. The patient and her parents were happy with the outcome, although the refractive error was not totally eliminated and she still needed to wear spectacles for clear vision. Possible etiologies of the complications are discussed.  相似文献   
53.
Efficacy of minor analgesics in primary dysmenorrhoea: a systematic review   总被引:1,自引:0,他引:1  
Objective To quantify the efficacy and safety of naproxen, ibuprofen, mefenamic acid, aspirin and acetaminophen (paracetamol) in the treatment of primary dysmenorrhoea through a systemic overview of randomised controlled trials.
Methods MEDLINE, EMBASE and the Science Citation Index were searched for randomised controlled trials. Efficacy was assessed by measurement of pain relief, requirement for rescue analgesics, restriction of daily life and absence from work or school. The rate ratios of side effects were used to assess safety.
Results Fifty-six trials describing 55 comparisons of analgesics with placebo and 12 direct comparisons with other analgesics met our inclusion criteria. Women taking naproxen were over three times more likely to have at least moderate pain relief than those taking placebo. Ibuprofen, mefenamic acid and aspirin were also superior to placebo but acetaminophen was not. The requirement for rescue analgesics, restriction of daily life and absence from work or school were less frequent with naproxen and ibuprofen than placebo but not with aspirin or acetaminophen. Direct comparisons did not show any difference between naproxen and ibuprofen. Side effects occurred more frequently only with naproxen when compared with placebo.
Conclusion Naproxen, ibuprofen, mefenamic acid and aspirin are all effective in primary dysmenorrhoea. Ibuprofen appears to have the most favourable risk-benefit ratio. Acetaminophen appears to be less effective than nonsteroidal anti-inflammatory drugs, but there was only one trial meeting our inclusion criteria and further studies are required.  相似文献   
54.
55.
小鼠卵细胞质内显微注入单精子受精的实验研究   总被引:8,自引:0,他引:8  
杨益寿  熊素芳  龙文  李鸣  夏明珠  汪昌介 《解剖学报》1998,29(4):441-445,I011
为了探讨提高小鼠卵细胞质内单精子注入受精率的方法,选取鼠龄12-14周的健康昆明白小鼠作为精子和卵子的供体,受用ICSI技术,以受精后二细胞卵裂的形成率为指标,了解不同采卵时间,不同微注射针参数及不同培养液对细胞质单精子注入的影响。结果表明,hCG注射后18-19h采卵,用针尖内径为4-5μm,斜面角度为35-40度的微注射针进行ICSI操作受精后卵子置CZB中培养可获得较多的2细胞胚,卵裂率明显  相似文献   
56.
Microanatomical compartments of the human spleen are yet under evaluation as most of the present information comes from experiments on animals with different anatomical structures. Immune staining of stromal and blood-born cells by cell surface antigens facilitates the differentiation of functional microanatomical compartmentalization of immune organs, including the spleen. Twenty-two specimens from healthy adult subjects with the average age of 35.6 +/- 13.8 (Range 17 to 58) years were included in this study. Monoclonal antibodies used in this study were supplied from the 5th, 6th and 7th International Workshops and Conferences on Human Leukocyte Differentiation Antigens. Tetraspan antigens presented a rather unique staining pattern in the human spleen, suggesting special roles for each (CD9, CD53, CD63, CD151 and CD231) in certain locations. Sinus lining cells presented a distinctive antigenic profile, sharing both endothelial cell (CD31, CD36, CD54, CD62P, CD102, CD105, CD106 and CD146) and macrophage lineage characteristics. The sheathed capillaries were not restricted to the perifollicular zone alone. Extracellular matrix receptors (CD49 a, CD49 b, CD49 c, CD49 e, CD49f, CD29 and CD44) stained the penicillary arterioles and vascular smooth muscle. These molecules were also found on the vascular endothelium. Leukocyte antigens (CD11a, CD11b, CD22, CD43, CD45, CD45RB, CD45RO and CD50) were mainly expressed in the white and red pulp of the spleen at different intensities, excluding the penicillary arterioles. Activation antigens (CD26, CD71 and CD98) presented a diffuse and broad staining pattern. In conclusion, microanatomical compartmentalization, microcirculation and function of the human spleen were evaluated using a wide panel of monoclonal antibodies.  相似文献   
57.
视盘血管炎——关于混合型的研讨   总被引:2,自引:0,他引:2  
对60例(63眼)视盘血管炎的临床分型进行了探讨,结果表明,除分为Ⅰ、Ⅱ两型外,尚存在混合型,当视盘睫状血管炎性病变波及中央静脉,或两个血管系统同时受炎症侵犯时,即可再现混合型的临床表现,视盘明显水肿,视网膜静脉迂张,散在渗出,出血,动脉狭细。眼底荧光血管造影可见视盘荧光早期充盈明显迟缓,后期渗漏面积〉2.0PD,视网膜循环时间延长,混合型兼有Ⅰ,Ⅱ两型的临床特征,应作为一个独立类型存在,同时观察  相似文献   
58.
The purpose of our study was to determine whether clonidine exerts its centrally mediated hypotensive action at three sites that influence arterial pressure located in the medulla, specifically associated with the intermediate area of the ventrolateral medulla. The "intermediate area" lies approximately 1.5 mm caudal to the border of the trapezoid body (caudal border) and 4 mm lateral to the midline. One of the sites that influence arterial pressure lies in the nucleus reticularis rostroventrolateralis. The second site lies in close proximity to the rostral part of the nucleus reticularis lateralis (rLRN) and also near the A1 area. The third site lies in the most rostral area and medial to the nucleus reticularis rostroventrolateralis, that is in the nucleus paragigantocellularis lateralis. Unilateral microinjections of 0.22 and 0.43 nmol of clonidine into the rLRN produced dose-dependent decreases in arterial pressure. The 0.43 nmol dose of clonidine had no effect when unilaterally or bilaterally microinjected into either the nucleus reticularis rostroventrolateralis or into the nucleus paragigantocellularis lateralis. Microinjection of the alpha-2 adrenoceptor antagonist, idazoxan (16.6 nmol), unilaterally into rLRN had no effect per se, but prevented the hypotensive effect of a subsequent microinjection of clonidine. Similarly, bilateral microinjection of idazoxan into rLRN counteracted the hypotensive effect of i.v. administered clonidine. These data indicate that clonidine acts at alpha-2 adrenoceptors in the rLRN to produce hypotension.  相似文献   
59.
宫颈粘液过氧化物酶在月经周期中的变化规律   总被引:3,自引:1,他引:2  
本文对29例月经周期正常妇女的宫颈粘液过氧化物酶进行了30个周期的研究。在月经周期不同时间测定宫颈粘液过氧化物酶(CMPx)活性及血清促黄体生成素(LH)、雌二醇(E_2)和孕酮(P)。结果表明:在排卵前三天酶活性明显下降,至排卵后一天开始上升。卵泡期,酶活性与E_2呈负相关(r=-0.67);黄体期,酶活性与P呈正相关(r=0.79)。本研究提示:1.CMPx在排卵周期具有特定的变化规律,其变化受体内激素水平影响,可作为预告排卵的指标。2.如简化测定方法,可为自然避孕提供新途径。  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