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   19891篇
  免费   2141篇
  国内免费   1579篇
耳鼻咽喉   102篇
儿科学   237篇
妇产科学   150篇
基础医学   1943篇
口腔科学   371篇
临床医学   2496篇
内科学   2669篇
皮肤病学   220篇
神经病学   1093篇
特种医学   950篇
外国民族医学   6篇
外科学   2316篇
综合类   3888篇
现状与发展   3篇
一般理论   1篇
预防医学   1459篇
眼科学   487篇
药学   2224篇
  15篇
中国医学   1487篇
肿瘤学   1494篇
  2024年   76篇
  2023年   303篇
  2022年   745篇
  2021年   864篇
  2020年   738篇
  2019年   705篇
  2018年   661篇
  2017年   635篇
  2016年   659篇
  2015年   931篇
  2014年   1157篇
  2013年   1131篇
  2012年   1491篇
  2011年   1676篇
  2010年   1196篇
  2009年   1032篇
  2008年   1158篇
  2007年   1191篇
  2006年   994篇
  2005年   860篇
  2004年   810篇
  2003年   892篇
  2002年   847篇
  2001年   618篇
  2000年   498篇
  1999年   365篇
  1998年   236篇
  1997年   205篇
  1996年   168篇
  1995年   126篇
  1994年   103篇
  1993年   83篇
  1992年   76篇
  1991年   76篇
  1990年   68篇
  1989年   49篇
  1988年   46篇
  1987年   39篇
  1986年   32篇
  1985年   22篇
  1984年   16篇
  1983年   8篇
  1982年   6篇
  1979年   6篇
  1977年   2篇
  1976年   3篇
  1975年   1篇
  1972年   1篇
  1971年   3篇
  1932年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
目的 分析高度近视眼白内障手术效果。方法 高度近视合并白内障病例共191 例(279 只眼),行白内障术后3mo以上,随访视力、眼屈光度及并发症,计算测量误差及SRK-II公式误差。结果 术后矫正视力0 .5 者200 只眼,占71.7 % ;矫正视力< 0.1 者13 只眼,占4 .7 % - 眼轴越长,近视性眼底病变越重。术后发生视网膜脱离2 只眼(0 .7%) 。眼轴长度测量误差值平均为0.53mm ,SRK-II公式计算的平均绝对屈光误差值为1.12D。结论 高度近视眼白内障手术效果较一般人群差,且眼轴越长效果越差。  相似文献   
32.
Mercury vapor sorption by soil increased curvilinearly with the increase of soil moisture content until a maximum was reached. A further increase of moisture content caused a decline in mercury sorption. The percent moisture contents which gave maximal increase of203Hg vapor sorption in these soils coincide quite closely with their water-holding capacity values at 1/3 bar.Soil microorganisms may play a part in moist soil for the increase of elemental mercury vapor sorption and subsequent transformation to mercuric form.Mercury vapor diffused into both dry and moist soil columns and the diffusion profile can be described by an exponential function of the form, y=ae–bx, where a is the adsorption characteristics of the soil, b is the diffusivity coefficient and x is the depth of soil. The diffusivity coefficient for mercury vapor varied with the soil type and its moisture content.Supported in part by grant R-803948 from the U.S. Environmental Protection Agency. Technical Paper No. 5489, Oregon Agricultural Experiment Station.  相似文献   
33.
Biochemical and metabolic indicators were monitored in a group of volunteers suffering from a variety of chronic illnesses participating in a week's course on a special uncooked vegetable diet, known as "living food". Unmatched healthy controls ate the same diet cooked for 2 min in a microwave oven. After 1 week on the regimen, serum protein and urea contents decreased and alanine aminotransferase (ALAT) activity increased in both groups, although all within the normal range. Blood glucose increased in both groups to slightly above normal limits but total serum cholesterol dropped about 1 mmol/l from normal starting levels. Serum tocopherol and retinol increased only in the group eating the uncooked diet. In both groups urinary sodium dropped drastically without a significant change in potassium. Serum and urinary phenol and p-cresol diminished also significantly. It is concluded that this vegetable diet may be of some benefit in the short term but any longer-term use requires evaluation.  相似文献   
34.
六味地黄汤含药血清对海马神经元突触活动的影响   总被引:3,自引:1,他引:3  
目的:研究六味地黄汤益智作用的机理。方法:应用血清药理学和电生理方法,观察六味地黄汤含药血清对原代培养大鼠海马神经元自发突触活动的影响。结果:含药血清作用48h可明显增加海马神经元自发动作电流(spontaneous action cur-rent,sAC)和微小兴奋性突触后电流(miniature excitatory post aynaptic currenl,mEPSC)的产生频率,但并不影响mEPSC的幅度。结论:六味地黄汤可作用于突触前位点对海马神经元突触活动产生调节作用,该作用可能是其调节海马神经元的兴奋性进而发挥益智作用的机制之一。  相似文献   
35.
"乳癌术后方"对乳腺癌患者生活质量影响的临床研究   总被引:5,自引:0,他引:5  
为评价“乳癌术后方”对 35 8例乳腺癌患者生活质量的影响。采用欧洲癌症治疗研究组织生活质量核心量表E ORTCQLQ -C30 ,对 35 8例乳腺癌患者运用“乳癌术后方”治疗前后分别进行问卷调查 ,并设对照组 96例。结果“乳癌术后方”治疗 6个月 ,临床症状明显改善 ,与对照组比较 ,P <0 0 5 ;患者生理功能、情感功能、认识功能等都有不同程度的提高 ;生活质量总评价各项治疗前后有明显改变 ,与对照组比较 ,P <0 0 5。提示该方能明显提高乳腺癌患者的生活质量 ,有很好的临床应用价值。  相似文献   
36.
PURPOSE: For cancer patients receiving cytotoxic chemotherapy, hepatitis B virus (HBV) reactivation is a well described complication resulting in varying degrees of liver damage. The objectives of this study were to assess the efficacy of the antiviral agent lamivudine in reducing the incidence of HBV reactivation and diminishing morbidity and mortality of cancer patients with chronic HBV infection during chemotherapy. PATIENTS AND METHODS: Two groups were compared in this nonrandomized study. The prophylactic lamivudine group consisted of 65 patients in a phase II study who were treated with lamivudine before and until 8 weeks after discontinuing chemotherapy. The historical controls consisted of 193 consecutive patients who underwent chemotherapy without prophylactic lamivudine. Significant prognosticators for the development of HBV reactivation were determined based on data from the controls. Potential confounding factors were identified between the two groups. The outcomes were compared. RESULTS: In the controls, lymphoma and anthracycline usage were factors identified to be associated with reactivation. The two groups were comparable in most baseline characteristics, although in the prophylactic lamivudine group, there were significantly more patients with lymphoma and receiving anthracyclines. In the prophylactic lamivudine group, there was significantly less HBV reactivation (4.6% v 24.4% in the controls; P <.001), fewer incidences of hepatitis (17.5% v 44.6%; P <.0001) that were less severe (4.8% v 18.7%; P =.0005), and less disruption of chemotherapy (15.4% v 34.6%; P =.0029). The reduction in overall mortality was not statistically different. CONCLUSION: Prophylactic lamivudine significantly reduced the incidence of HBV reactivation and the overall morbidity of cancer patients undergoing chemotherapy.  相似文献   
37.
消瘀散消肿止痛作用的实验观察   总被引:2,自引:2,他引:2  
消瘀散在临床运用中有较好的消肿止痛之功效.为了证实其药理作用,作者用大白鼠建立急性软组织损伤和血肿的实验模型,使用消疾散进行治疗。观察结果表明该药能够有效抑制创伤性无菌性炎症反应,促进血肿吸收,提高实验动物的痛阈值;而且药效随作用时间的延长而逐渐增加。实验结果为该药的消肿止痛作用提供了科学依据。  相似文献   
38.
目的:观察N-(4-羟苯基)维甲酰胺(4-HPR)联合γ-射线对人膀胱移行细胞癌的生长抑制和诱导凋亡作用,分析两者之间是否存在协同作用.方法:应用四甲基偶氮蓝比色(MTT)法检测4-HPR对膀胱癌细胞株T24的细胞毒性作用、半数抑瘤率及起效浓度和时间.应用流式细胞仪检测4-HPR、γ-射线及两者联合应用时对T24细胞生长抑制作用.结果:2.5μmol/L、5μmol/L、10μmol/L的4-HPR作用T24细胞5天的凋亡率分别为6.2%、28.0%和26.0%,死亡率分别为0.3%、12.5%和26.7%.联合作用组细胞分别加入2.5μmol/L、5μmol/L的4-HPR,100cgy的γ-射线照射一次,3天后T24细胞的凋亡率分别为20.0%、26.0%,细胞的死亡率均在5.0%以下.5天后T24细胞的凋亡率分别为38.0%、35.0%,而细胞的死亡率分别为12.4%、21.1%.结论:小剂量的4-HPR可以诱导T24细胞凋亡,大剂量的4-HPR主要导致T24细胞死亡.小剂量的4-HPR联合小剂量的γ-射线对T24细胞凋亡有明显的协同作用.  相似文献   
39.
Genetically engineered mice are increasingly important in stroke research. The strains on which these constructs are built are known to have inherent differential sensitivities to ischemic insults. This has been largely attributed to differences in vascular anatomy. This study compared the outcome from forebrain ischemia in two common murine background strains using two different types of ischemic insult. C57Bl/6 and SV129 mice were subjected to two vessel (bilateral carotid) occlusion (2VO) or 2VO plus systemic hypotension (2VO+Hypo; mean arterial pressure=30+/-2 mmHg) for 10-20 min. Ventilation and pericranial temperature were controlled. Cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Histologic damage in forebrain structures was measured 3 days post-ischemia. During 2VO+Hypo, the EEG became isoelectric in all animals. During 2VO alone, EEG isoelectricity occurred in 73% of C57Bl/6 and 50% of SV129 mice. Forebrain CBF was reduced to a similar extent in both strains. Greater CBF variability was seen with 2VO alone versus 2VO+Hypo. CBF was less in the 2VO+Hypo model. SV129 mice had wider posterior communicating but smaller basilar artery diameters. With or without hypotension, SV129 mice had markedly less severe histologic damage than C57Bl/6 mice. A time-dependent increase in histologic damage was demonstrated in the 2VO+Hypo model but not with 2VO alone. The 2VO and 2VO+Hypo models produced similar magnitudes of histologic injury in C57Bl/6 mice subjected to 10-min ischemia. SV129 mice were resistant to ischemia in either model. The 2VO+Hypo model produced a more uniform severity of ischemia as defined by CBF and EEG examination. Despite this, the murine strain had a substantially greater impact on histologic outcome than did cerebrovascular anatomy or the type of model used to produce the ischemic insult.  相似文献   
40.
Birthdates of the neurons that comprise the layers of the mature visual cortex in the wallaby (Macropus eugenii) have been determined with the aid of tritiated thymidine autoradiography. The laminar positions of cells, identified by their birthdates, have then been followed at early stages during development and compared with previously published data on the distribution of thalamocortical afferents and corticothalamic projecting cells (Sheng et al. [1991] J. Comp. Neurol. 307:17-38). Neurons are born in a deep to superficial sequence typical of other mammals. The loosely packed zone of cells, which develops at the base of the thin compact zone of cells at the superficial margin of the cortical plate early in development, was identified as being part of the cortical plate. Afferents did not wait below this zone but grew into the developing cortical layers immediately after the cells that form these layers began accumulating in the loosely packed zone, starting with layer 6 on postnatal day 22 (P22). The genesis of layer 4 did not begin until P32, and these cells reached the superficial cortical plate at P54 and entered the loosely packed zone by P65. Cells of layers 5 and 6 formed the initial projection to the thalamus. Despite the protracted development of the wallaby and the large discrepancy between the time of thalamic ingrowth and genesis of layer 4, there was no extended waiting period for afferents in the subplate.  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