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   27375篇
  免费   2322篇
  国内免费   2063篇
耳鼻咽喉   218篇
儿科学   254篇
妇产科学   243篇
基础医学   3178篇
口腔科学   424篇
临床医学   3598篇
内科学   3773篇
皮肤病学   173篇
神经病学   1363篇
特种医学   966篇
外国民族医学   19篇
外科学   3141篇
综合类   4649篇
现状与发展   5篇
一般理论   1篇
预防医学   1892篇
眼科学   676篇
药学   2934篇
  33篇
中国医学   1571篇
肿瘤学   2649篇
  2025年   2篇
  2024年   420篇
  2023年   591篇
  2022年   1167篇
  2021年   1342篇
  2020年   1122篇
  2019年   957篇
  2018年   925篇
  2017年   831篇
  2016年   822篇
  2015年   1207篇
  2014年   1470篇
  2013年   1286篇
  2012年   1806篇
  2011年   2042篇
  2010年   1316篇
  2009年   1048篇
  2008年   1360篇
  2007年   1446篇
  2006年   1339篇
  2005年   1360篇
  2004年   854篇
  2003年   955篇
  2002年   731篇
  2001年   619篇
  2000年   672篇
  1999年   788篇
  1998年   481篇
  1997年   480篇
  1996年   339篇
  1995年   319篇
  1994年   314篇
  1993年   169篇
  1992年   214篇
  1991年   180篇
  1990年   151篇
  1989年   152篇
  1988年   127篇
  1987年   103篇
  1986年   75篇
  1985年   82篇
  1984年   28篇
  1983年   17篇
  1982年   13篇
  1981年   11篇
  1980年   6篇
  1979年   19篇
  1974年   1篇
  1929年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
近年来随着新型降糖药的出现,糖尿病药物市场呈现快速增长趋势,目前仅次于肿瘤用药,居全球药品销售排行第二位.DPP-4抑制剂作为一种治疗糖尿病的较新型药物,目前主要用于2型糖尿病的治疗.该类产品凭借其耐受性及安全性较好、低血糖发生率低、可口服等优势,在国内外临床指南中逐步得到充分认可,治疗地位不断提升,逐渐成为降糖药物市场的主力之一.因此,DPP-4抑制剂国内市场方兴未艾,其进医保后将释放更大市场空间,也是各大国内药企研发抢仿的热点所在.本文建议国内企业在研发立项DPP-4抑制剂这类新药时,不应盲目跟从热点,还需关注其临床需求、新药安全性评价、剂型优化选择并结合企业自身情况等进行综合评估.  相似文献   
92.
To increase the durability and seismic resilience of coastal bridges, a hybrid reinforced concrete (HRC) bridge that incorporates both glass fiber-reinforced polymer (GFRP) bars and steel bars is proposed. The time-dependent seismic performance of the HRC bridge is comprehensively investigated at three levels, namely the material, bridge column and bridge structure levels. First, the decrease of tensile strength of GFRP bars over time is analyzed based on the Arrhenius theory, and corrosion initiation time and performance deterioration of steel bars are determined by Fick’s second law and an empirical formula. Second, an efficient finite element modeling method for aging HRC bridge columns is proposed. Simulation of the compression/tension behavior and the fracture failure of the GFRP bar is described. Hysteretic analysis is further conducted to investigate the time-dependent energy dissipation, ductility, residual displacement, bearing capacity and post-yield stiffness ratio. Meanwhile, comparisons of HRC bridge columns to reinforced concrete (RC) references are provided. Third, the seismic demand and damage evolution of deteriorated HRC bridge structures are investigated through dynamic time-history analysis. The results indicate that the corrosion-resistant GFRP bars contribute to improving the bearing capacity and to reducing the residual displacement of the HRC bridge. With an increase in service time, the seismic damage to the bridge column, abutment and expansion bearing increases, but the damage to fixed bearing decreases. Research results presented herein show that the HRC bridge is a promising alternative structure scheme in the marine environment.  相似文献   
93.
PRK术后角膜上皮下雾状混浊的相关因素分析   总被引:3,自引:0,他引:3  
为探讨准分子激光角膜切削术(photorefractivekeratectomy,PRK)后角膜上皮下雾状混浊(haze)的原因及影响因素,对PRK后6个月时屈光度在-1.00~-18.50D的316例(615只眼)近视眼的haze相关因素进行观察和比较。结果:PRK后6个月时haze发生率为44.7%,1级或以上haze为13.3%。haze的发生率及密度随屈光度增高而增加(P<0.0001),也随切削深度的增加而增加(P<0.0001),术前非接触眼压超过18mmHg者,haze的发生率和密度增加(P<0.005),男性较易发生haze(P=0.0001),与年龄呈负相关(P<0.05)。而角膜厚度、术前戴用接触镜及散光对haze的影响不显著。结论:高度近视(>-6.0D)和过深的切削(>80μm)是引起haze的主要原因。术前眼压偏高、年龄偏低对haze也有明显影响。对PRK治疗高度近视应持审  相似文献   
94.
95.
96.
Shen ZY  Li EM  Lu SQ  Shen J  Cai YM  Wu YE  Zheng RM  Tan LJ  Xu LY 《Placenta》2008,29(11):956-961
The aim of this paper is to determine if autophagic cell death is associated with apoptosis and whether it participates in the process of term amniotic rupture. Forty pieces of fresh term amnions, including twenty from a position near the margin of the placentas and twenty from the margin of the naturally ruptured part of the placentas in term gestation were collected, respectively. The amnions were examined by scanning electron microscopy (SEM) and amniotic epithelial (AE) cells were examined by transmission electron microscopy (TEM). Autophagic and apoptotic cell death (PCD) were assayed by laser scanning confocal microscopy (LSCM) or flow cytometry using monodansylcadaverin (MDC) and propidium iodide (PI) stain. BCL(2) and BAX were examined by immunoblotting. Under SEM the amniotic epithelia appeared normal in the position near the placenta. They had an atrophied appearance in the margin of their natural broken parts. In the AE cells PCD was divided into three subtypes by TEM: autophagic cell death with positive stains of MDC and PI; apoptotic cell death; and the mixed type. Quantitative detection showed that there were more death cells, including autophagic and apoptotic, in the AE cells near the ruptured parts than near the placentas. An increased expression of BAX and a decreased expression of BCL(2) protein in the AE cells near the broken margin were observed. Apoptotic and autophagic cell death by the intrinsic pathway are the basic event in the AE cell and they are involved in the cause of membrane rupture of the human amnion in term gestation.  相似文献   
97.
Duan P  Cheng J  Lin M  Cai LL  Hu Z  Jin SX  Hu MP 《中华妇产科杂志》2008,43(4):272-275
OBJECTIVE: To study intermediate and long term efficacy of uterine arterial embolization (UAE) with sodium alginate microspheres (KMG) at diameters 500-00 microm in treatment of diffuse adenomyosis. METHODS: Totally 40 patients with standard diffuse adenomyosis were enrolled and treated with UAE. KMG at diameters 500-700 microm for vascular embolization were used to embolize the arteries. The degree of dysmenorrhea, amount of menorrhea and uterine volume, as well as the level of serum CA125, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) were investigated before and after UAE. RESULTS: The follow up rates were 100% (40/40), 100% (40/40), 80% (32/40), 68% (27/40), 58% (23/40) after uterine arterial UAE 12, 24, 36, 48 and 60 months respectively. The early, intermediate and long-term effective rates were 90% (36/40), 88% (28/32), 83% (19/23). The degree of dysmenorrhea, the amount of menorrhea and the uterine volume, as well as serum CA125 all decreased significantly 3 months after UAE at varying degrees (P < 0.05). Compared with other follow-up time, the degree of dysmenorrhea and the amount of menorrhea declined to their lowest point at 6 month after UAE (P < 0.01). Paralleled with the decrease of volume of uterine, serum CA125 also decreased significantly and reached the lowest level 12 months later compared with other follow-up times (P < 0.01). Even at the 12th month after UAE serum CA125 was not normal and FSH, LH and E2 did not change all the times after UAE, (P > 0.05). No recurrence was found during the 60 months after UAE. CONCLUSION: KMG used in UAE at diameters 500-700 microm has good intermediate and long term effectiveness in treatment of diffuse adenomyosis with no side effects.  相似文献   
98.
99.
This retrospective cohort study examines the relationship between changing pregnancy-smoking behaviors, from the first to the second pregnancy, on second-pregnancy rates of small for gestational age (SGA) neonates. Electronic birth records provided data on 5107 pregnant women who had two singleton births in Kansas City, MO, from 1994 to 2003. Pregnancy-smoking behavior was classified by smoking status (nonsmoker [NS] or smoker [SMK]) during the first (previous)/second (current) pregnancy: NS/NS, NS/SMK, SMK/SMK, and SMK/NS. The overall second-pregnancy SGA rate was 6.7% and varied with pregnancy-smoking behavior: 5.9%, NS/NS; 6.6%, SMK/NS; 12.5%, NS/SMK; and 12%, SMK/SMK; P < 0.001 Current pregnancy-smoking was associated with increased odds ratio (OR) of SGA; SMK/SMK (OR, 2.80; 95% confidence interval [CI], 2.00 to 3.93) versus NS/SMK (OR, 1.83; 95% CI, 1.19 to 2.82) versus SMK/NS (OR, 1.31; 95% CI, 0.65 to 2.65) versus NS/NS (OR, 1.00; 95% CI, reference). Being black (OR, 3.73; 95% CI, 2.91 to 4.79) and having medical risk factors (OR, 1.31; 95% CI, 1.09 to 1.74) also were significantly associated with a SGA neonate in second pregnancy. In conclusion, risk of delivering a SGA neonate in a current pregnancy is related to current rather than previous pregnancy-smoking. Therefore, antismoking socialization during pregnancy should focus on preventing and stopping current pregnancy-smoking, irrespective of past behavior.  相似文献   
100.
阿尔茨海默病(Alzheimer's disease,AD)属于常见的神经退行性疾病,以进行性认知功能减退为主要特征,至今病因未明,也没有治愈AD的有效方法.抗氧化剂可以清除体内自由基,有助于预防和治疗与氧化应激相关的疾病,现已在抗衰老以及肿瘤、心血管疾病的防治中广泛使用.近年来,国内外学者尝试用抗氧化剂防治AD,但其使用剂量不同于在防治其他疾病时的用量,可能会带来潜在的危险.抗氧化剂在防治AD中的疗效和安全性究竟怎样?近年来出现了越来越多的负面结果和讨论,因此有必要客观评价该类药物在AD中的临床效果和安全性.  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