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   288879篇
  免费   12379篇
  国内免费   8514篇
耳鼻咽喉   2106篇
儿科学   7811篇
妇产科学   4298篇
基础医学   29398篇
口腔科学   3938篇
临床医学   27804篇
内科学   47035篇
皮肤病学   1747篇
神经病学   22111篇
特种医学   13085篇
外国民族医学   70篇
外科学   39534篇
综合类   23398篇
现状与发展   38篇
一般理论   9篇
预防医学   25675篇
眼科学   5852篇
药学   21911篇
  122篇
中国医学   8142篇
肿瘤学   25688篇
  2024年   501篇
  2023年   2204篇
  2022年   5425篇
  2021年   6625篇
  2020年   5025篇
  2019年   4093篇
  2018年   25727篇
  2017年   21081篇
  2016年   22826篇
  2015年   6432篇
  2014年   7477篇
  2013年   6796篇
  2012年   15644篇
  2011年   30541篇
  2010年   24786篇
  2009年   16212篇
  2008年   25197篇
  2007年   27537篇
  2006年   6305篇
  2005年   7792篇
  2004年   6952篇
  2003年   7586篇
  2002年   5349篇
  2001年   2621篇
  2000年   2847篇
  1999年   2889篇
  1998年   2002篇
  1997年   1884篇
  1996年   1365篇
  1995年   1239篇
  1994年   1063篇
  1993年   718篇
  1992年   791篇
  1991年   722篇
  1990年   700篇
  1989年   563篇
  1988年   459篇
  1987年   407篇
  1986年   284篇
  1985年   236篇
  1984年   119篇
  1983年   99篇
  1982年   69篇
  1981年   51篇
  1980年   68篇
  1979年   34篇
  1938年   60篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Melatonin induces apoptosis in many different cancer cell lines, including colorectal cancer. However, the precise mechanisms involved remain largely unresolved. In this study, we provide evidence to reveal a new mechanism by which melatonin induces apoptosis of colorectal cancer LoVo cells. Melatonin at pharmacological concentrations significantly suppressed cell proliferation and induced apoptosis in a dose‐dependent manner. The observed apoptosis was accompanied by the melatonin‐induced dephosphorylation and nuclear import of histone deacetylase 4 (HDAC4). Pretreatment with a HDAC4‐specific siRNA effectively attenuated the melatonin‐induced apoptosis, indicating that nuclear localization of HDAC4 is required for melatonin‐induced apoptosis. Moreover, constitutively active Ca2+/calmodulin‐dependent protein kinase II alpha (CaMKIIα) abrogated the melatonin‐induced HDAC4 nuclear import and apoptosis of LoVo cells. Furthermore, melatonin decreased H3 acetylation on bcl‐2 promoter, leading to a reduction of bcl‐2 expression, whereas constitutively active CaMKIIα(T286D) or HDAC4‐specific siRNA abrogated the effect of melatonin. In conclusion, the present study provides evidence that melatonin‐induced apoptosis in colorectal cancer LoVo cells largely depends on the nuclear import of HDAC4 and subsequent H3 deacetylation via the inactivation of CaMKIIα.  相似文献   
62.
Contraceptive use is an important strategy for the prevention of unwanted pregnancy and avoidance of induced abortion. Of all the contraception methods, emergency contraceptive (EC) offers the last chance to achieve this. However, few studies have documented the use of EC among young people in Ghana. This study explored knowledge and usage of EC as well as the factors associated with it among University of Cape Coast students. Data were obtained on the knowledge and usage of ECs among University of Cape Coast students in 2013. Logistic regression analysis was used to investigate the association between students’ socio-demographic characteristics and EC knowledge and use. More male students (72 %) than females (59 %) were sexually active. Fifty-seven percent of the respondents had ever heard of EC and 36 % had ever used EC. Although males were more likely to be sexually active, females were more likely to have knowledge of EC use compared to males. The study underscores the need to increase awareness regarding EC among University students in order to offer them the opportunity that EC provides if other forms of contraceptives are missed.  相似文献   
63.
64.
Gastroesophageal reflux is the most common benign disorder of the esophagus and laparoscopic Nissen fundoplication has become the standard surgical treatment for its treatment. In our area, where the use of bougie calibration is debatable, postoperative dysphagia is encountered often after this surgery although it is usually not permanent. The aim of this study was to investigate the effect of using a soft silicone tube 39 F in diameter for esophageal calibration during laparoscopic Nissen fundoplication on the incidence of postoperative dysphagia. We divided cases scheduled to undergo laparoscopic Nissen fundoplication between January 2009 and November 2010 into two groups, each consisting 25 patients. Esophageal calibration with a 39 F silicone orogastric tube was used for the first group while there was no operative calibration in the second group. The surgical duration was recorded; the presence and severity of the postoperative dysphagia was calculated by using a dysphagia severity scoring system during the 1-year postoperative follow-up. The dysphagia severity scores were significantly lower in group 1 than group 2 on the postoperative second day and at the end of the first week and first month. We did not find a significant difference at the end of the 6-month and first year. There was also no significant difference regarding surgery duration. The use of a soft orogastric tube 39 F in diameter for esophagus calibration during laparoscopic Nissen fundoplication has significantly decreased the incidence of postoperative transient dysphagia without affecting the duration of surgery. Although dysphagia gradually resolves in the majority of patients, a safe and easy calibration method for its prevention is worth developing, and we believe that the use of our method in larger series could be beneficial.  相似文献   
65.
66.
Background: Previous genome-wide association study (GWAS) has revealed the association between MYP10 at 8p23 and MYP15 at 10q21.1 and high myopia (HM) in a French population. This study is managed to discover the connection between some single nucleotide polymorphism (located at MYP10 and MYP15) and Han Chinese HM.

Methods and Results: This case-control association study contained 1673 samples, including 869 ophthalmic patients and 804 controls. Twelve tag SNPs have been selected from the MYP10 and MYP15 loci and genotyped by SNaPshot method. Among 12 SNPs, rs4840437 and rs6989782 in TNKS gene were found significant association with HM. Carriers of rs4840437G allele and rs4840437GG genotype created a low risk of high myopia (P = .036, OR = 0.81, 95%CI = 0.71–0.93; P = .016, OR = 0.73, 95%CI = 0.56–0.96; respectively). Carriers of rs6989782T allele and rs6989782TT+CT genotype also had a decreased risk of high myopia (P = .048, OR = 0.82, 95%CI = 0.71–0.94; P = .006, OR = 0.74, 95%CI = 0.59–0.92; respectively). Other 10 SNPs displaced nonsignificant association with HM. Additionally, the risk haplotype AC and the protective haplotype GT, generated by two SNPs in TNKS, were considerably more likely to be association with HM (for AC, P = .002 and OR = 1.26; for GT, P = .027 and OR = 0.84).

Conclusions: Our results demonstrated that some heritable variants in the TNKS gene are associated with HM in the Han population. The possible functions of TNKS in the development and pathogenesis of hereditary high myopia still require further researches to identify.  相似文献   

67.
68.
目的探讨聪耳通窍汤联合耳针治疗老年神经性耳鸣患者的近远期疗效。方法选取耳鼻喉科门诊收治的老年神经性耳鸣患者136例,按随机数字表法分组,对照组68例予以耳针治疗,研究组68例在对照组基础上予以聪耳通窍汤治疗。检测比较两组间近、远期临床疗效、甲襞微循环指标、血液流变学指标以及不良反应发生率。结果治疗后,对照组总有效率为67.64%(46/68)低于研究组总有效率83.82%(57/68),具有统计学意义(P<0.05);随访6个月后,对照组总有效率64.71%(44/68)低于研究组总有效率89.71%(61/68),具有统计学意义(P<0.05);与对照组比较,研究组治疗后甲襞微循环襻周积分、管襻积分、流态积分及总积分较低,治疗后血浆黏度、高切全血黏度、低切全血黏度及红细胞压积较低,差异具有统计学意义(P<0.05);治疗中出现的不良反应为恶心、腹胀、针刺部位疼痛,两组间不良反应发生率无统计学差异(P>0.05)。结论聪耳通窍汤联合耳针治疗老年神经性耳鸣患者的近远期疗效均较好,能明显改善患者微循环状态及血液流变学指标,减轻内耳循环障碍,具有较高安全性。  相似文献   
69.
70.
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