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   7661篇
  免费   560篇
  国内免费   202篇
耳鼻咽喉   566篇
儿科学   40篇
妇产科学   667篇
基础医学   692篇
口腔科学   496篇
临床医学   682篇
内科学   1235篇
皮肤病学   19篇
神经病学   88篇
特种医学   237篇
外科学   807篇
综合类   1128篇
现状与发展   1篇
预防医学   281篇
眼科学   849篇
药学   306篇
  4篇
中国医学   144篇
肿瘤学   181篇
  2024年   26篇
  2023年   132篇
  2022年   202篇
  2021年   369篇
  2020年   336篇
  2019年   268篇
  2018年   287篇
  2017年   330篇
  2016年   322篇
  2015年   269篇
  2014年   588篇
  2013年   579篇
  2012年   450篇
  2011年   485篇
  2010年   383篇
  2009年   336篇
  2008年   297篇
  2007年   356篇
  2006年   310篇
  2005年   311篇
  2004年   234篇
  2003年   238篇
  2002年   208篇
  2001年   187篇
  2000年   133篇
  1999年   120篇
  1998年   80篇
  1997年   75篇
  1996年   76篇
  1995年   74篇
  1994年   40篇
  1993年   36篇
  1992年   36篇
  1991年   26篇
  1990年   28篇
  1989年   31篇
  1988年   17篇
  1987年   20篇
  1986年   24篇
  1985年   24篇
  1984年   15篇
  1983年   9篇
  1982年   14篇
  1981年   8篇
  1980年   11篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   4篇
  1974年   3篇
排序方式: 共有8423条查询结果,搜索用时 15 毫秒
81.
Endometrial receptivity and implantation are important topics in reproductive sciences. No evidence was found to support sperm involvement in endometrial receptivity and its associated factors. This study aimed to explore the effect of the normal human spermatozoa–endometrium cell interaction in regulating genes in the endometrial receptivity pathway. Semen samples were collected from a healthy and fertile man; then, they were incubated with endometrial cells for 24 hr and considered as the sperm group. A group was cultured without spermatozoa and considered as a control group. About 24 hr later, cells were collected from the bottom of the culture dish. The expressions of the VEGF, FGF2, HBEGF, LIFR, EGF, LIF, MUC1, HOXA10, CSF and PGR genes were evaluated in the two groups. Statistical analysis was performed using an independent sample test. Compared with the control group, in the sperm group, the mRNA levels of PGR (p = .0451), VEGF (p = .0101), HBEGF (p = .0163), EFG (p = .0339), FGF2 (p = .012), LIF (p = .0324), LIFR (p = .0321) and HOXA10 (p = .0098) were significantly upregulated. The results showed that there is a need for the interaction between spermatozoa and endometrium for implantation and can be used for preparing uterine in in vitro fertilisation cycles.  相似文献   
82.
In this study, we sought to determine whether sperm DNA fragmentation (DFI%) and high DNA stainability (HDS%) evaluated by sperm chromatin structure assay (SCSA) predict recurrent implantation failure (RIF) or pregnancy rate. A retrospective study was performed of consecutive cycles of ICSI treatment from 2009 to 2018. A total of 386 couples that underwent 1,216 frozen embryo transfer (FET) cycles were analysed. Mean female and male age was 34 ± 3.6 years and 37.3 ± 6.6 years, respectively, and a median total motile sperm count (TMSC) was 43.5 [9.9–105.5] million. Overall median DFI% and HDS% was 12 [7.1–18.9] and 9.6 [6.5–14.4] respectively. On multivariable analysis, DFI% and HDS% were not associated with RIF (DFI%: OR = 1.01, 95% CI: 0.98–1.04, p = .414; HDS%: OR = 0.97, 95% CI: 0.94–1.01, p = .107) or IVF success, defined as clinical pregnancy (DFI%: OR = 1.00, 95% CI: 0.99–1.01, p = .641; HDS%: OR = 1.01, 95% CI: 0.99–1.02, p = .565). We found that neither DFI% or HDS%, as assessed by SCSA, were predictive of RIF or pregnancy rate. This finding suggests that sperm DNA fragmentation does not predict RIF or pregnancy rate.  相似文献   
83.
Diabetes mellitus is associated with increased risk of erectile dysfunction. Penile prosthesis implantation is an efficient therapeutic option for erectile dysfunction, but not without risk, as infection remains a prominent concern. This study investigates diabetes mellitus as a risk factor for penile prosthesis implantation infection and the relationship between haemoglobinA1c levels and infection rates. All diabetic patients with erectile dysfunction who underwent penile prosthesis implantation surgery between January 2012 and November 2019 at Hamad Medical Corporation, Qatar, were included in this retrospective observational study. A total of 599 diabetic patients with erectile dysfunction had penile prosthesis implantation. Mean age was 59.69 ± 31.19. Penile prosthesis implantation infection rate was 0.83% (5/599), while the mean haemoglobinA1c level was 7.58 ± 1.45 mmol/l (range: 4.1–12.6). A comparison between diabetic patients with penile prosthesis implantation infection and those without infection revealed no significant difference in the level of haemoglobinA1c between the two groups with mean haemoglobinA1c in patients with infected implants 7.14 and 7.59 for noninfected (p = 0.491). Limitations include retrospective single-centre design and low-infection rates reducing sample number. Penile prosthesis implantation infection rate in a large series of diabetic patients was low with no significant association between haemoglobinA1c level and penile prosthesis implantation infection observed.  相似文献   
84.
田甜  景慧  荆莉 《护理学杂志》2021,36(12):26-30
目的 分析与提取颈动脉支架植入术后患者发生谵妄的危险因素,为针对性干预提供参考.方法 统计350例颈动脉狭窄支架植入术后患者谵妄发生率,行单因素和多因素分析获得术后患者谵妄相关危险因素,基此构建列线图预测模型,采用校正曲线和ROC曲线评估其准确度和区分度.结果 60例术后发生谵妄,发生率17.14%;高龄、术前NIHSS评分和术前焦虑是术后发生谵妄的独立危险因素(均P<0.05);由3项独立危险因素构建的谵妄风险列线图预测模型,预测曲线和观察曲线基本吻合,AUC=0.888.结论 颈动脉支架植入术后患者谵妄发生率较高;高龄、术前焦虑及脑卒中倾向是术后患者发生谵妄的危险因素;构建的列线图预测模型具有较好的准确度和区分度,可提高筛选效能.  相似文献   
85.
目的 探讨山羊颈椎次全切除减压非融合后生物力学特性.方法 选取成年雄性山羊6只造模(模型组),术前行颈椎X线检查,排除骨性结构异常,并测量节段性Cobb角(SCA)和颈椎Cobb角(CCA)于C4行颈椎次全切除术,并植入可动人工颈椎(ACV).术后行颈椎正侧位X线检查,再次测量SCA和CCA.术后6个月处死山羊,并以6只正常山羊作为对照组.取新鲜颈椎标本,采用MTS生物材料测试机和NDI Optotrak Certus光电子三维运动捕捉系统测量C2/C3、C3/C4、C4/C5、C2/C5节段的活动度(ROM).结果 模型组山羊术前SCA和CCA分别为10.8°±0.9°和21.8°±0.5°,植入ACV后SCA和CCA分别为10.7°±0.9°和21.5°±1.5°,2组手术前后SCA和CCA差异均无统计学意义(P>0.05).术后6个月,模型组与对照组山羊新鲜颈椎标本C2/C3、C3/C4、C4/C5、C2/C5的ROM测量结果显示,C2/C3左侧曲、C3/C4右侧曲和右旋、C4/C5前屈和左旋、C2/C5右旋组间比较差异有统计学意义(P<0.05),其他方向ROM组间比较差异均无统计学意义(P>0.05).结论 ACV能在椎体次全切除术后重建山羊颈椎高度且对相应节段的脊髓无损伤,但在某些方向上ROM不足或偏大,仍需进一步改进.  相似文献   
86.
IntroductionBone Cement Implantation Syndrome (BCIS) is a lethal condition with complex physiological changes after the insertion of Methyl Methacrylate (MMA) cement during intraoperative arthroplasty. Despite the etiology and the pathophysiology of BCIS has not been fully understood, several mechanisms have been discovered. Some clinical manifestations of BCIS are hypotension, hypoxemia, a decrease of consciousness, arrhythmia, pulmonary hypertension, and cardiac arrest.Presentation of caseA 67 years old woman underwent cemented hemiarthroplasty operation due to intertrochanteric fracture in her right femur. The hemodynamic was stable before and during operation, but suddenly the patient went into cardiac arrest as the cement inserted. Immediate resuscitation was performed successfully and stable hemodynamic was achieved.DiscussionSeveral risk factors including underlying cardiovascular disease, advanced age, osteoporosis (enlarged porous cavities increase the risk of emboli generation), fracture type, metastatic bone disease, femoral canal diameter of more than 21 mm, previously non-instrumented femoral canal, and patent foramen ovale (paradoxical embolus). Some studies have shown usage of H1 and H2 antagonists, methylprednisolone, inotropes, vasopressor, and some alterations in surgical technique, can prevent the progression of the BCIS. Communication between the orthopaedic surgeon and anesthesiologist and high-quality cardiopulmonary resuscitation (CPR) will become a good basis in treating BCIS.ConclusionPreoperative optimization by increasing oxygen inspiration concentration, usage of inotropes and vasopressor, and avoiding intravascular volume depletion during operation is essential in cemented arthroplasty procedure. Both orthopaedic surgeon and anesthesiologist should recognize the clinical presentation of BCIS and well-prepared for the management of BCIS including any supportive measures.  相似文献   
87.
88.
Embryo transfer (ET) is the last stage of extracorporal fertilization during which the embryo is placed in the uterine cavity with a medium-filled catheter 2–3 days after in vitro fertilization. While fertilization in the laboratory occurs at very high rates (>:90%), the overall success of the procedure (i.e., take home baby) is still very low (<25%) and assumed to be mainly due to implantation failure. A computational model was developed to simulate ET within the uterine cavity by a fluid-filled catheter inserted into a two-dimensional channel with oscillating walls. The results showed that the speed at which the embryos are injected from the catheter dominates the procedure and controls the velocity of their transport within the uterine cavity. ET at excessively high injection speeds may lead to ectopic pregnancies, while uterine peristalsis affects transverse dispersion only during injection at low injection speeds. The presence of the catheter within the uterus does not affect flow patterns downstream of its tip. The potential risks to implantation failure due to mechanical factors involved in the ET processes are discussed. © 2003 Biomedical Engineering Society. PAC2003: 8719-j, 8710+e  相似文献   
89.
目的观察pSVPoMcat微基因修饰雪旺细胞(SC)移植对损伤脊髓功能恢复的影响. 方法采用切割法制备脊髓半横断损伤模型(T8平面),实验动物随机植入pSVPoMcat微基因的 SC组(A组)、SC组(B组)和明胶海绵组(C组),每组10只.用皮层体感诱发电位(CSEP) 及图像分析方法比较各组间诱发电位潜伏期、波幅,再生轴突计数.同时,行电镜观察及联合行为(CBS)记分. 结果 A,B两组潜伏期和波幅呈恢复趋势,且A组已接近正常,与CBS结果一致.再生轴突计数A组为388±163,B组为109±16(P<0.01),与电镜观察一致. 结论 pSVPoMcat微基因修饰SC移植对脊髓损伤(SCI)后的神经功能恢复有明显的促进作用.  相似文献   
90.
:【目的】明确尸食性蝇类卵的形态 ,以便于在医学和法医学中的应用。【方法】用扫描电镜机观察杭州地区 4种尸食性蝇类卵的形态。【结果】丝光绿蝇、大头金蝇、巨尾阿丽蝇和厩腐蝇卵的超微结构形态各异 ,卵的大小、表面形态、中区、孵出线、卵孔和垂柱皆为重要的鉴别特征。【结论】通过卵壳超微结构可区分常见尸食性蝇类。  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