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   1195篇
  免费   85篇
  国内免费   59篇
耳鼻咽喉   3篇
儿科学   54篇
妇产科学   10篇
基础医学   90篇
口腔科学   14篇
临床医学   189篇
内科学   287篇
皮肤病学   18篇
神经病学   37篇
特种医学   231篇
外科学   117篇
综合类   48篇
预防医学   92篇
眼科学   21篇
药学   90篇
中国医学   3篇
肿瘤学   35篇
  2021年   19篇
  2020年   9篇
  2019年   6篇
  2018年   24篇
  2017年   10篇
  2016年   12篇
  2015年   20篇
  2014年   20篇
  2013年   42篇
  2012年   32篇
  2011年   38篇
  2010年   35篇
  2009年   30篇
  2008年   29篇
  2007年   67篇
  2006年   20篇
  2005年   25篇
  2004年   28篇
  2003年   27篇
  2002年   25篇
  2001年   33篇
  2000年   28篇
  1999年   26篇
  1998年   55篇
  1997年   43篇
  1996年   61篇
  1995年   48篇
  1994年   44篇
  1993年   54篇
  1992年   23篇
  1991年   17篇
  1990年   23篇
  1989年   33篇
  1988年   41篇
  1987年   44篇
  1986年   27篇
  1985年   35篇
  1984年   20篇
  1983年   14篇
  1982年   15篇
  1981年   27篇
  1980年   21篇
  1979年   10篇
  1978年   15篇
  1977年   17篇
  1976年   9篇
  1975年   10篇
  1973年   4篇
  1972年   3篇
  1966年   3篇
排序方式: 共有1339条查询结果,搜索用时 15 毫秒
51.
Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra.  相似文献   
52.
Mohandas  N; Lie-Injo  LE; Friedman  M; Mak  JW 《Blood》1984,63(6):1385-1392
A high frequency of nonhemolytic hereditary ovalocytosis in Malayan aborigines is thought to result from reduced susceptibility of affected individuals to malaria. Indeed, Kidson et al. recently showed that ovalocytes from Melanesians in Papua New Guinea are resistant to infection in culture by the malarial parasite Plasmodium falciparum. In order to determine if protection against parasitic invasion in these ovalocytes might be the result of some altered membrane material property in these unusual cells, we measured their membrane and cellular deformability characteristics using an ektacytometer . Ovalocytic red cells were found to be much less deformable in comparison to normal discoid red cells. Similar measurements on isolated membrane preparations revealed a marked reduction in ovalocytic membrane deformability. To produce equal deformation of ovalocytic and normal membranes, ovalocytes required an 8-10-fold increase in applied shear stress, indicating that their membrane was capable of deforming under sufficient stress. To test the possibility that this increased membrane rigidity might confer resistance to parasitic invasion, we performed an in vitro invasion assay using Plasmodium falciparum merozoites and Malayan ovalocytes of varying deformability from seven different donors. The level of infection of the ovalocytes ranged from 1% to 35% of that in control cells, and the extent of inhibition appeared to be closely related to the reduction in membrane deformability. Moreover, we were able to induce similar resistance to parasitic invasion in nonovalocytic normal red cells by increasing their membrane rigidity with graded exposure to a protein crosslinking agent. Our findings suggest that resistance to parasite invasion of Malayan ovalocytes is the result of a genetic mutation that causes increased membrane rigidity.  相似文献   
53.
54.

Background and purpose —

In orthopedic oncology, computer-assisted surgery (CAS) can be considered an alternative to fluoroscopy and direct measurement for orientation, planning, and margin control. However, only small case series reporting specific applications have been published. We therefore describe possible applications of CAS and report preliminary results in 130 procedures.

Patients and methods —

We conducted a retrospective cohort study of all oncological CAS procedures in a single institution from November 2006 to March 2013. Mean follow-up time was 32 months. We categorized and analyzed 130 procedures for clinical parameters. The categories were image-based intralesional treatment, image-based resection, image-based resection and reconstruction, and imageless resection and reconstruction.

Results —

Application to intralesional treatment showed 1 inadequate curettage and 1 (other) recurrence in 63 cases. Image-based resections in 42 cases showed 40 R0 margins; 16 in 17 pelvic resections. Image-based reconstruction facilitated graft creation with a mean reconstruction accuracy of 0.9 mm in one case. Imageless CAS was helpful in resection planning and length- and joint line reconstruction for tumor prostheses.

Interpretation —

CAS is a promising new development. Preliminary results show a high number of R0 resections and low short-term recurrence rates for curettage.Oncological surgical treatment can be considered to be a trade-off between margins and function, with margins being the most important factor to consider. Accuracy is needed to achieve an efficient but oncologically safe result. To assist in this, most procedures in bone tumor surgery require intraoperative imaging with fluoroscopy and/or measurements with rulers for anatomical orientation and margin control. The best examples of this are pelvic resections. Cartiaux et al. (2008) demonstrated that 4 experienced surgeons could achieve a 10-mm resection margin, with 5-mm tolerance, on pelvic sawbones in only half of the resections. The supportive imaging and measuring modalities have, however, remained more or less unchanged for many years. In a 2-dimensional (2D) workflow such as fluoroscopy, there is still the requirement for an accurate frame of reference based on anatomical landmarks for adequate 3-dimensional (3D) margin control.In recent years, the use of computer-assisted surgery (CAS) in orthopedic surgery has become more common as an alternative for intraoperative imaging and measurements, providing the necessary precision in bone tumor surgery. The technique that is mostly used in orthopedic oncology is image-based navigation. The patient’s own anatomy (MRI and/or CT) is entered into the system and used during surgery. This provides real-time, continuous, 3D imaging feedback and may lead to more precise margin control, better tissue preservation, and new approaches to reconstruction while remaining oncologically safe. Several publications have supported CAS as being a safe navigation platform for planning and performing resections (Wong et al. 2007, So et al. 2010, Cho et al. 2012). A recent publication describes lessons in the technological approach and offers comments on CAS workflow (Wong 2010). However, to date the largest case series have involved only 20 and 31 cases (Cheong and Letson 2011, Jeys et al. 2013). The reported use has mostly been limited to complex tumor resections (e.g. pelvic), and due to the novelty of the technique, applications, approaches, and set-up times differ greatly (Saidi 2012). Here we describe possible applications of CAS in bone tumor surgery (also outside of complex resections), consider their usefulness, and report preliminary results from 130 CAS procedures performed at a single institution.  相似文献   
55.
56.
目的:在前期微囊化基因工程细胞制备平台的基础上,构建分泌型人肿瘤坏死因子α的真核表达载体PSNAV2.0-TNFα重组质粒,并鉴定其蛋白的体外瞬时表达,为进一步利用该基因进行微囊化细胞移植治疗和改善疾病奠定基础。方法:实验于2006-06/2007-05在解放军总医院老年医学研究所细胞生物学实验室完成。①以含有人肿瘤坏死因子αcDNA序列的质粒为模板,通过PCR扩增获得人肿瘤坏死因子α基因片段;将其定向插入真核表达载体PSNAV2.0中,获得重组质粒PSNAV2.0-TNFα。采用SalⅠ和EcoRⅠ双酶切法、PCR法及插入片段序列测定法鉴定该质粒。②利用阳离子脂质体介导法,将其转染到人胚胎肾细胞HEK-293细胞中,构建可持续分泌人肿瘤坏死因子α的基因工程细胞,采用RT-PCR法和Western blot法检测转染细胞培养上清液中人肿瘤坏死因子蛋白的体外瞬时表达。结果:①通过SalⅠ和EcoRⅠ双酶切、PCR及测序鉴定证明:在HEK-293中插入片段正确。②采用RT-PCR和Western blot法检测表明HEK-293细胞培养上清中有人肿瘤坏死因子α蛋白,Mr17000。结论:成功构建了重组质粒PSNAV2.0-TNFα真核表达载体,转染HEK-293细胞后可有效分泌人肿瘤坏死因子α蛋白,并能分泌到细胞外。  相似文献   
57.
人羊膜间充质细胞具有分化成软骨及成骨细胞的潜能   总被引:1,自引:0,他引:1  
目的:人羊膜间充质细胞具有比骨髓间充质干细胞更强的扩增能力和免疫原性低等优势。建立体外适宜的诱导培养条件,观察人羊膜间充质细胞定向分化为软骨细胞和成骨细胞的能力。方法:实验于2005-09/2006-12在贵州省细胞工程重点实验室完成。①材料来源:经产妇知情同意,无菌采集健康足月分娩新生儿胎盘6份,实验经医院医学伦理委员会批准。②实验方法:采用机械法剥离羊膜组织,二步酶消化法分离收获人羊膜间充质细胞,按2.2×10~8L~(-1)密度接种,传至第1~2代用于诱导分化实验。向软骨细胞诱导分化时,人羊膜间充质细胞按3×10~8L~(-1)密度接种,诱导培养液为含体积分数0.01的胎牛血清、10 mg/L转化生长因β1、100 nmol/L地塞米松、50 mg/L抗坏血酸、1%培养基添加物。向成骨细胞诱导分化时,人羊膜间充质细胞按6×10~7L~(-1)密度接种,诱导培养液为含体积分数0.1的胎牛血清、100 nmol/L地塞米松、50 mg/L抗坏血酸、5 mmol/Lβ-甘油磷酸。③实验评估:原代细胞用流式细胞仪分析表型,免疫细胞化学染色进行波形蛋白表达鉴定。分别于体外诱导第7,14,21,28天采用免疫细胞化学法检测软骨特异性Ⅱ型胶原的表达,细胞化学法检测蛋白聚糖的表达,钙-钴法检测成骨细胞特异性碱性磷酸酶的表达,茜素红S检测钙盐沉积情况。结果:①免疫组化与表型特征:人羊膜间充质细胞高表达间充质干细胞表面标志CD29、CD44和间充质细胞标志波形蛋白。②向软骨细胞诱导分化:诱导14 d后,人羊膜间充质细胞由长梭型逐渐变为多角形,可检测到Ⅱ型胶原蛋白表达及软骨细胞特异性细胞外基质蛋白聚糖。③向成骨细胞诱导分化:诱导21 d后,可观察到人羊膜间充质细胞的胞浆内有碱性磷酸酶表达,且可见钙盐沉积。结论:人羊膜间充质细胞具有分化成软骨细胞和成骨细胞的特性,可作为骨及软骨组织工程种子细胞的新来源。  相似文献   
58.
INTRODUCTION: Acetaminophen (paracetamol) overdose (AOD) has recently emerged as the leading cause of acute liver failure (ALF) in the United States, with an incidence approaching that seen in the United Kingdom. We describe a new way to treat AOD ALF patients fulfilling King's College criteria for "super-urgent" liver transplantation. METHODS: Beginning in June 1998, we have been piloting a clinical program of subtotal hepatectomy and auxiliary orthotopic liver transplantation (ALT) for AOD ALF. Our technique is based on the following principles: (1) subtotal hepatectomy; (2) auxiliary transplantation of a whole liver graft; (3) gradual withdrawal of immunosuppression after recovery. Results were compared with patients who had undergone an orthotopic liver transplantation (OLT) for AOD ALF in the same period. Quality of life comparisons were made using the SF36 questionnaire. RESULTS: Thirteen patients underwent this procedure between June 1998 and March 2005. Median survival is 68 months (range, 0-102 m). Actual survival data show that 9 of 13 patients are alive (69%) compared with 7 of 13 OLT patients (54%). One ALT patient required a retransplantation with an OLT due to hepatic vein thrombosis, and immunosuppression is therefore maintained. The other 8 surviving ALT patients are off immunosuppression. These 8 ALT patients have normal liver function and have a better quality of life compared with the 7 surviving OLT patients. CONCLUSION: Our results with this new technique are encouraging: 69% actual survival, no long-term immunosuppression requirement, and improved quality of life in the 62% successful cases.  相似文献   
59.
Sentinel lymph node (SLN) biopsy has been shown to predict axillary metastases accurately in early stage breast cancer. Some patients with locally advanced breast cancer receive preoperative (neoadjuvant) chemotherapy, which may alter lymphatic drainage and lymph node structure. In this study, we examined the feasibility and accuracy of SLN mapping in these patients and whether serial sectioning and keratin immunohistochemical (IHC) staining would improve the identification of metastases in lymph nodes with chemotherapy-induced changes. Thirty-eight patients with stage II or III breast cancer treated with neoadjuvant chemotherapy were included. In all patients, SLN biopsy was attempted, and immediately afterward, axillary lymph node dissection was performed. If the result of the SLN biopsy was negative on initial hematoxylin and eosin-stained sections, all axillary nodes were examined with three additional hematoxylin and eosin sections and one keratin IHC stain. SLNs were identified in 31 (82%) of 38 patients. The SLN accurately predicted axillary status in 28 (90%) of 31 patients (three false negatives). On examination of the original hematoxylin and eosin-stained sections, 20 patients were found to have tumor-free SLNs. With the additional sections, 4 (20%) of these 20 patients were found to have occult lymph node metastases. These metastatic foci were seen on the hematoxylin and eosin staining and keratin IHC staining. Our findings indicate that lymph node mapping in patients with breast cancer treated with neoadjuvant chemotherapy can identify the SLN, and SLN biopsy in this group accurately predicts axillary nodal status in most patients. Furthermore, serial sectioning and IHC staining aid in the identification of occult micrometastases in lymph nodes with chemotherapy-induced changes.  相似文献   
60.
OBJECTIVE: To determine the incidence and prognostic significance of documented eradication of breast cancer axillary lymph node (ALN) metastases after neoadjuvant chemotherapy. SUMMARY BACKGROUND DATA: Neoadjuvant chemotherapy is the standard of care for patients with locally advanced breast cancer and is being evaluated in patients with earlier-stage operable disease. METHODS: One hundred ninety-one patients with locally advanced breast cancer and cytologically documented ALN metastases were treated in two prospective trials of doxorubicin-based neoadjuvant chemotherapy. Patients had breast surgery with level I and II axillary dissection followed by additional chemotherapy and radiation treatment. Nodal sections from 43 patients who were originally identified as having negative ALNs at surgery were reevaluated and histologically confirmed to be without metastases. An additional 1112 sections from these lymph node blocks were obtained; half were stained with an anticytokeratin antibody cocktail and analyzed. Survival was calculated using the Kaplan-Meier method. RESULTS: Of 191 patients with positive ALNs at diagnosis, 23% (43 patients) were converted to a negative axillary nodal status on histologic examination (median number of nodes removed = 16). Of the 43 patients with complete axillary conversion, 26% (n = 11) had N1 disease and 74% (n = 32) had N2 disease. On univariate analysis, patients with complete versus incomplete histologic axillary conversion were more likely to have initial estrogen-receptor-negative tumors, smaller primary tumors, and a complete pathologic response in the primary tumor. The 5-year disease-free survival rates were 87% in patients with preoperative eradication of axillary metastases and 51% for patients with residual nodal disease after neoadjuvant chemotherapy. Of the 39 patients with complete histologic conversion for whom nodal blocks were available, occult nodal metastases were found in additional nodal sections in 4 patients (10%). At a median follow-up of 61 months, the 5-year disease-free survival rates were 87% in patients without occult nodal metastases and 75% in patients with occult nodal metastases. CONCLUSIONS: Neoadjuvant chemotherapy can completely clear the axilla of microscopic disease before surgery, and occult metastases are found in only 10% of patients with a histologically negative axilla. The results of this study have implications for the potential use of sentinel lymph node biopsy as an alternative to axillary dissection in patients treated with neoadjuvant chemotherapy.  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