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   2151篇
  免费   113篇
  国内免费   22篇
耳鼻咽喉   3篇
儿科学   159篇
妇产科学   18篇
基础医学   242篇
口腔科学   105篇
临床医学   181篇
内科学   502篇
皮肤病学   56篇
神经病学   79篇
特种医学   482篇
外科学   193篇
综合类   30篇
预防医学   75篇
眼科学   18篇
药学   69篇
中国医学   4篇
肿瘤学   70篇
  2023年   7篇
  2022年   11篇
  2021年   19篇
  2020年   16篇
  2019年   30篇
  2018年   33篇
  2017年   19篇
  2016年   29篇
  2015年   40篇
  2014年   46篇
  2013年   79篇
  2012年   74篇
  2011年   51篇
  2010年   94篇
  2009年   70篇
  2008年   57篇
  2007年   58篇
  2006年   40篇
  2005年   34篇
  2004年   33篇
  2003年   37篇
  2002年   41篇
  2001年   33篇
  2000年   45篇
  1999年   48篇
  1998年   140篇
  1997年   118篇
  1996年   125篇
  1995年   92篇
  1994年   77篇
  1993年   85篇
  1992年   28篇
  1991年   23篇
  1990年   18篇
  1989年   63篇
  1988年   47篇
  1987年   52篇
  1986年   49篇
  1985年   49篇
  1984年   24篇
  1983年   33篇
  1982年   36篇
  1981年   20篇
  1980年   39篇
  1979年   22篇
  1978年   17篇
  1977年   20篇
  1976年   24篇
  1975年   26篇
  1971年   7篇
排序方式: 共有2286条查询结果,搜索用时 15 毫秒
991.
分子生物学,特别是重组DNA技术的出现,使我们对人类遗传病有了更深入的认识。这一领域的进展是极其迅速的,其中最明显的例子就是对X-连锁遗传病Duchenne肌营养不良症(DMD)的研究。用基因组探针检测携带者和产前诊断已经证明XJ1.1和pERT基因组探针,及侧翼探针如C7、754和99.6对于发现DMD携带者和产前诊断具有不可估量的价值。受累患儿血清CK水平是正常儿童的100~200倍,但用于检测携带者却不可靠,因为有1/3的肯定携带者的CK水平在正常范围。而应用RFLP进行的连锁分析具有很高的可信  相似文献   
992.
Vitamin D is an important factor in bone metabolism. Animal studies have shown a positive effect of vitamin D3 supplementation on fracture healing, but evidence from clinical trials is inconclusive. A randomized controlled trial was performed to assess the effects of vitamin D3 supplementation on fracture healing using HR-pQCT–based outcome parameters. Thirty-two postmenopausal women with a conservatively treated distal radius fracture were included within 2 weeks postfracture and randomized to a low-dose (N = 10) and a high-dose (N = 11) vitamin D intervention group receiving a 6-week bolus dose, equivalent to 700 and 1800 IU vitamin D3 supplementation per day, respectively, in addition to a control group (N = 11) receiving no supplementation. After the baseline visit 1–2 weeks postfracture, follow-up visits were scheduled at 3–4, 6–8, and 12 weeks postfracture. At each visit, HR-pQCT scans of the fractured radius were performed. Cortical and trabecular bone density and microarchitectural parameters and microfinite element analysis–derived torsion, compression, and bending stiffness were assessed. Additionally, serum markers of bone resorption (CTX) and bone formation (PINP) were measured. Baseline serum levels of 25OHD3 were <50 nmol/L in 33% of all participants and <75 nmol/L in 70%. Compared with the control group, high-dose vitamin D3 supplementation resulted in a decreased trabecular number (regression coefficient β: −0.22; p < 0.01) and lower compression stiffness (B: −3.63; p < 0.05, together with an increase in the bone resorption marker CTX (B: 0.062; p < 0.05). No statistically significant differences were observed between the control and low-dose intervention group. In conclusion, the bolus equivalent of 700 U/day vitamin D3 supplementation in a Western postmenopausal population does not improve distal radius fracture healing and an equivalent dose of 1800 IU/day may be detrimental in restoring bone stiffness during the first 12 weeks of fracture healing. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).  相似文献   
993.
目的:建立高效液相色谱测定红药胶囊中6种成分三七皂苷R1、人参皂苷Rg1、人参皂苷Rb1、欧前胡素、异欧前胡素和羟基红花黄色素A的含量。方法:采用Waster XTerra C18色谱柱(250×4.6 mm,5μm),流动相为乙腈-0.1%磷酸水溶液,流速1.0 m L/min,检测波长为203 nm、300 nm和403 nm,柱温30℃。结果:三七皂苷R1、人参皂苷Rg1、人参皂苷Rb1、欧前胡素、异欧前胡素和羟基红花黄色素A的进样量分别在0.310~5.425μg(0.9997),0.404~7.070μg(0.9998),0.420~7.350μg(0.9997),0.008~0.140μg(0.9996),0.002~0.034μg(0.9996),0.012~0.217μg(0.9997)范围内与峰面积线性关系良好,平均加样回收率(n=6)分别为98.23%、99.15%、100.32%、99.91%,98.67%,99.27%。结论:含量测定方法可作为红药胶囊的质量控制的有效方法。  相似文献   
994.
Thrombocytopenia after liver transplantation   总被引:9,自引:0,他引:9  
BACKGROUND: Thrombocytopenia after orthotopic liver transplantation (OLT) is a well recognized and prevalent early postoperative complication. The etiology, as well as the effect of this phenomenon on transplant outcome, however, are vague. The aims of this study are to identify factors contributing to thrombocytopenia and to ascertain whether there is any correlation with early rejection and ultimate survival. METHODS: This study examines 541 OLTs (541 grafts in 494 patients) that were transplanted at the University of Miami during the 3-year period from June 1994 to September 1997. The patients with severe postoperative thrombocytopenia (nadir platelet count [PLT] < 20,000/mm3), as well as the whole group of patients, were analyzed. The preoperative PLT, intra-operative platelet transfusion requirements, cross-match, recipient and donor cytomegalovirus (CMV) status, infusion of donor bone marrow cells (DBMC), occurrence of early rejection episodes (in the first posttransplant month), and re-transplantation were factors examined for any association with thrombocytopenia. Total bilirubin (TB) and direct bilirubin (dB), hematocrit, white blood cell count (WBC), aspartate aminotransferase and alanine aminotransferase, determined on the day that platelets reached a nadir (nadir day), were also analyzed. RESULTS: In 90.9% of the cases, there was a 56.5%+/-23.5% fall in platelets in the immediate posttransplant period (first 2 weeks), but the mean PLT exceeded preoperative levels during the 3rd and 4th postoperative weeks. The nadir of the drop in the PLT most commonly occurred on posttransplant day 4. For preoperative PLT, platelet transfusions during the operation, re-transplantation, early rejection, cross-match, and recipient CMV status, there was significant statistical correlation with any degree of postoperative thrombocytopenia. Four of these factors, preoperative PLT, intra-operative platelet transfusions, re-transplantation, and early rejection, were found to be independently associated with thrombocytopenia in general. None of them was found to be independently correlated with severe thrombocytopenia. A statistically significant correlation between bilirubin and WBC on the nadir day and the degree of thrombocytopenia was observed. No correlation was found between infusion of DBMC or donor CMV serology and thrombocytopenia. Both the nadir PLT and the percentage of the platelet fall were independent predictive factors (p<0.01 and 0.005, respectively) of patient and graft survival. CONCLUSIONS: Thrombocytopenia in the immediate posttransplant period is correlated with low preoperative PLT, massive platelet transfusions, and re-transplantation. These factors reflect a poor preoperative condition. There is also a correlation with allograft dysfunction, rejection, and poorer patient and graft survival. A rise in the mean PLT after the 2nd postoperative week reflects proper graft function.  相似文献   
995.
前列腺癌中突变型p53蛋白的表达及意义   总被引:2,自引:2,他引:0  
殷金安  刘凡  刘荣福 《医学争鸣》1999,20(8):706-706
0 引言 p53蛋白是一个细胞周期相关蛋白,分为野生型(Wtp53)及突变型(Mtp53)两种. 虽然Mtp53蛋白已经丧失抑制细胞增殖的能力,但可能参与调节某些与细胞分化和增殖有关的基因表达. 我们采用组织抗原微波修复技术和免疫组织化学SABC法对前列腺癌(PC)标本中Mtp53蛋白进行检测,探讨PC的病因学、病理学分级、临床分期及其与预后的关系.  相似文献   
996.
This report describes two cases of pediatric small bowel transplant patients who developed diffuse adenovirus enterocolitis of their allografts. Based upon the presenting symptoms for this complication, in both patients a differential diagnosis of allograft rejection versus viral infection was clinically entertained. The clinical condition in both instances rapidly deteriorated and both patients died shortly after the development of the symptoms of fulminant septicemia. Autopsies were performed and histologic examination revealed extensive denudation of the gastrointestinal mucosa with edema and a marked acute and chronic inflammatory infiltrate involving the entire wall of the grafts. Numerous viral intranuclear and intracytoplasmic inclusions were evident and an immunohistochemical stain specific for adenovirus was strongly positive in the infected cells. In addition, while in the first case the adenovirus appeared confined to the GI tract, the second patient displayed numerous viral inclusions in the lung as well as within multiple liver abscesses. At this point, the incidence of adenovirus as a cause of gastroenteritis in small bowel transplant patients remains to be determined. We believe that the importance of recognizing this particular type of viral infection in this group of patients lies primarily in differentiating it from other viral organisms (e.g., CMV) that require a specific antiviral therapy. Moreover, an identification of this entity could help avoid a misdiagnosis of rejection which could lead to an unnecessary increase in immunosuppressive therapy and a possible exacerbation of the underlying condition.  相似文献   
997.
The administration of murine mAb specific for the CD3 epsilon subunit of the TCR complex (OKT3) has been demonstrated to engender in humans an anti-OKT3 idiotypic cascade. This study used murine-derived anti-OKT3 (Ab2) as a bioreagent to determine whether this Ab2 and polyclonal anti-(anti-OKT3) (Ab3) generated in some human kidney transplant patients are idiotypically connected. Two anti-OKT3 mAbs G-880 (IgG1) and M-12 (IgM) were derived by immunizing BALB/c mice with the OKT3-secreting hybridoma. The two mAbs exhibited specificity for OKT3 F(ab)'2 idiotypic determinants. Both mAbs were tested for their ability to inhibit OKT3 induced mitogenesis and to block FITC-OKT3 binding to cell surface CD3 epsilon chain. The M-12 mAb inhibited OKT3-induced mitogenesis and blocked (approximately 60%) the binding of OKT3 to peripheral blood (PBL) T-cell CD3 epsilon chain in flow cytometry. In contrast, the G-880 mAb did not inhibit mitogenesis and only weakly blocked OKT3 binding to CD3 epsilon chain (approximately 12%). Sera of kidney transplant recipients who received OKT3 antirejection therapy and who developed antiidiotypic anti-OKT3 antibodies could be divided into two subgroups exhibiting anti-OKT3 activity: (a) those who had similar specificity as M-12 and failed to enhance the M-12 inhibition of OKT3 binding to PBL T-cell CD3 epsilon chain when added as a third component (n = 3), and (b) those with anti-OKT3 antibodies with idiotype specificity dissimilar to M-12 and who were able to increase the (maximum 60%) inhibition obtained with M-12 in the OKT3 to T-cell CD3-binding assay (n = 4). From these observations, we conclude that M-12 had the characteristics of an Ab2 beta and G-880 that of an Ab2 alpha. Additionally, there was an idiotypic connectivity of mouse-derived M-12 anti-OKT3 (Ab2) and OKT3-engendered human polyclonal anti-(anti-OKT3) (Ab3), in that three of seven patients examined had human serum IgG antibodies that specifically recognized M-12 idiotypic determinants as demonstrated in ELISA.  相似文献   
998.
The present study is the first prospective randomized controlled trial of the effect of pentoxifylline on future fertility in infertile women with asymptomatic minimal or mild endometriosis. After completion of a basic infertility workup and laparoscopy, patients were entered into the study and randomly allocated to receive either a 12 month course of oral pentoxifylline (800 mg/day) (n = 30) or an oral placebo (n = 30). Those patients with other infertility factors were included in the study only if the factors were correctable and ultimately determined to be non-contributory. Life-table analysis was used to compare pregnancy rates between the two groups over a 12 month period that started immediately after laparoscopy. The 12 month actuarial overall pregnancy rates were 31 and 18.5% in the pentoxifylline and placebo groups respectively. However, this difference was not statistically significant by the chi(2)-test. Similarly, the Cox regression method showed no differences between the hazard of pregnancy in the two groups studied (odds ratio, 0.56; 95% confidence interval, 0.18-1.67). Therefore, there is no evidence from this study that immunomodulation with pentoxifylline aids fertility in those women with minimal or mild endometriosis. Further studies including more infertile patients with endometriosis are desirable in order to confirm our results.   相似文献   
999.
1000.
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