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   128410篇
  免费   12381篇
  国内免费   6721篇
耳鼻咽喉   1028篇
儿科学   1983篇
妇产科学   1499篇
基础医学   31325篇
口腔科学   10595篇
临床医学   9300篇
内科学   17012篇
皮肤病学   2202篇
神经病学   9234篇
特种医学   2520篇
外国民族医学   27篇
外科学   10466篇
综合类   18411篇
现状与发展   32篇
一般理论   2篇
预防医学   3517篇
眼科学   3207篇
药学   11253篇
  26篇
中国医学   3534篇
肿瘤学   10339篇
  2024年   130篇
  2023年   1598篇
  2022年   2195篇
  2021年   4046篇
  2020年   3964篇
  2019年   3785篇
  2018年   3991篇
  2017年   4279篇
  2016年   4766篇
  2015年   5367篇
  2014年   8374篇
  2013年   10141篇
  2012年   7763篇
  2011年   9130篇
  2010年   7416篇
  2009年   7091篇
  2008年   7293篇
  2007年   7359篇
  2006年   6724篇
  2005年   5754篇
  2004年   4863篇
  2003年   4002篇
  2002年   3040篇
  2001年   2536篇
  2000年   2172篇
  1999年   1817篇
  1998年   1713篇
  1997年   1536篇
  1996年   1382篇
  1995年   1382篇
  1994年   1264篇
  1993年   1083篇
  1992年   901篇
  1991年   838篇
  1990年   729篇
  1989年   711篇
  1988年   617篇
  1987年   556篇
  1986年   493篇
  1985年   781篇
  1984年   674篇
  1983年   491篇
  1982年   619篇
  1981年   474篇
  1980年   424篇
  1979年   339篇
  1978年   247篇
  1977年   194篇
  1976年   188篇
  1975年   77篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
31.
目的:研究长柱重楼、滇重楼和南重楼的HPLC指纹图谱与其抗肝癌作用的谱效关系,为明确重楼抗肝癌作用的物质基础提供实验依据。方法:采用HPLC建立3种重楼提取物的指纹图谱,流动相乙腈(A)-水(B)梯度洗脱(0~10 min,20%A; 10~20 min,20%~25%A; 20~30 min,25%~30%A; 30~40 min,30%~35%A; 40~50 min,35%~40%A; 50~60 min,40%A; 60~75 min,40%~45%A; 75~80 min,45%~60%A),流速0. 9 m L·min~(-1),检测波长203 nm;利用噻唑蓝(MTT)比色法测定3种重楼提取物对肝癌HepG2细胞的增殖抑制作用,计算半数抑制浓度(IC_(50));运用聚类分析(HCA)和灰色关联度分析(GRA)研究3种重楼指纹图谱和抗肝癌作用的关系,找出对抗肝癌作用贡献较大的成分。结果:在3种重楼的HPLC指纹图谱中,确定其中11个色谱峰为共有峰。作用时间72 h时长柱重楼、滇重楼、南重楼的IC_(50)分别为148. 33,178. 87,208. 09 mg·L~(-1),其中长柱重楼的抗肝癌活性最强。灰色关联度结果显示,滇重楼共有峰中关联度较高的为1~10号峰,长柱重楼共有峰关联度较高的为1~7号峰,南重楼共有峰中关联度较高的为1~4,6~10,N1号峰,与IC_(50)关联度均0. 7。各重楼变量的聚类分析结果显示,可与IC_(50)聚为一类的色谱峰的关联度均 0. 7。结论:建立了3种重楼的HPLC指纹图谱,重复性良好。3种重楼中的1~4,6和7号色谱峰对抗肝癌药效贡献最大。  相似文献   
32.
33.
Gangliocytic paragangliomas are rare tumors that almost exclusively occur within the second portion of the duodenum. Although these tumors generally have a benign clinical course, they have the potential to recur or metastasize to regional lymph nodes. The case report presented here describes a 57-year-old female patient with melena, progressive asthenia, anemia, and a mass in the second-third portion of the duodenum that was treated by local excision. The patient was diagnosed with a friable bleeding tumor. The histologic analysis showed that the tumor was a 4 cm gangliocytic paraganglioma without a malignant cell pattern. In the absence of local invasion or distant metastasis, endoscopic resection represents a feasible, curative therapy. Although endoscopic polypectomy is currently considered the treatment of choice, it is not recommended if the size of the tumor is > 3 cm and/or there is active or recent bleeding. Patients diagnosed with a gangliocytic paraganglioma should be closely followed-up for possible local recurrence.  相似文献   
34.

Background

Refractory acute myeloid leukemia (AML) includes AML includes failure of disease to respond to standard induction chemotherapy, relapse within 6 months after first CR, and 2 or more relapses. The outcome of these patients is usually very poor; only a small proportion can be rescued by allogenic hematopoietic stem-cell transplantation (allo-HSCT). The aim of this study was to evaluate the efficacy and feasibility of allo-HSCT in patients with refractory AML.

Patients and Methods

We retrospectively analyzed the clinical outcome of 91 patients who were diagnosed with treatment-refractory AML at Hacettepe University Hospital between January 2002 and June 2018. Patients' disease status included refractory AML, defined as failure to respond to standard induction chemotherapy and relapse within 6 months after first complete remission.

Results

The median follow-up was 12 months (range, 0.5-184 months) for the entire group. Kaplan-Meier estimates of the 3-year overall survival for patients who underwent allo-HSCT and patients who received only salvage chemotherapy were 67% and 12%, respectively. Additionally, the Kaplan-Meier estimates of 5-year overall survival for patients who underwent allo-HSCT and patients who received only salvage chemotherapy were 44% and 4%, respectively (P < .001). Complete remission was obtained in 25 patients (83.3%) who underwent allo-HSCT; however, the disease of only 3 patients (3.8%) exhibited complete response after salvage chemotherapy.

Conclusion

Allo-HSCT is still the best-known treatment option with curative potential in patients with treatment-refractory AML. Therefore, all efforts should be made in an attempt to find a suitable matched donor in order to perform allo-HSCT.  相似文献   
35.
Cis-diamminedichloridoplatinum(II)(CDDP)-based combination chemotherapy is frequently used in gastrointestinal cancer. The synergistic mechanism of all-trans retinoic acid (ATRA), cisplatin (CDDP) and 5-fluorouracil (5-FU) in combination remains unclear. Despite their potent antitumor properties, resistance to CDDP and 5-FU develops frequently in tumors. To clarify this mechanism, we determined the sensitivity to each drug and their combination in two gastrointestinal cancer stem cells (CSCs) subpopulation.Here, we report the identification and separation of CD44+ cells from human gastric carcinoma (AGS) and human esophageal squamous cell carcinoma (KYSE-30) cancer cell lines by magnetic activated cell sorting (MACS). We allowed the CD44± cells to grow 6 days at a subtoxic concentration of ATRA and then treated with different concentration of CDDP and 5-FU for 24 h. The cytotoxicity was examined by cell proliferation MTT assay. Additionally, AO/EB staining was used for detection of apoptotic cells. In order to determine whether the growth inhibition was also associated with changes in cell cycle distribution, cell cycle analysis was performed using flow cytometry.Low concentration of ATRA (1 μM, 6days) followed by 5-FU and CDDP was found to be more effective than either drugs alone, thus resulting in synergistic cytotoxicity in Kyse-30 and AGSCD44± cells. Furthermore, there was an indication that the combination of ATRA with 5FU and CDDP caused an increase in cell cycle arrest in G2/M and G0/G1.We conclude that low concentration of ATRA enhances the cytotoxicity of CDDP and 5FU by facilitating apoptosis and cell cycle arrest in gastrointestinal CSCs and provide a rational basis for the design of novel, well-tolerated CDDP- and 5FU-based chemotherapy in human gastrointestinal carcinoma.  相似文献   
36.
2型糖尿病及骨质疏松已成为我国最主要的慢性代谢性疾病。2型糖尿病常伴有血脂紊乱,常表现为低密度脂蛋白升高,而越来越多的研究表明血脂通过不同的方式影响骨代谢,其机制可能是通过抑制骨髓间充质干细胞成骨分化,通过RANK/RNAKL/OPG信号通路及炎症反应调节破骨细胞等方式调节骨代谢。  相似文献   
37.
Neural crest stem cells (NCSCs), a population of multipotent cells that migrate extensively and give rise to diverse derivatives, including peripheral and enteric neurons and glia, craniofacial cartilage and bone, melanocytes and smooth muscle, have great potential for regenerative medicine. Non-human primates provide optimal models for the development of stem cell therapies. Here, we describe the first derivation of NCSCs from cynomolgus monkey embryonic stem cells (CmESCs) at the neural rosette stage. CmESC-derived neurospheres replated on polyornithine/laminin-coated dishes migrated onto the substrate and showed characteristic expression of NCSC markers, including Sox10, AP2α, Slug, Nestin, p75, and HNK1. CmNCSCs were capable of propagating in an undifferentiated state in vitro as adherent or suspension cultures, and could be subsequently induced to differentiate towards peripheral nervous system lineages (peripheral sympathetic neurons, sensory neurons, and Schwann cells) and mesenchymal lineages (osteoblasts, adipocytes, chondrocytes, and smooth muscle cells). CmNCSCs transplanted into developing chick embryos or fetal brains of cynomolgus macaques survived, migrated, and differentiated into progeny consistent with a neural crest identity. Our studies demonstrate that CmNCSCs offer a new tool for investigating neural crest development and neural crest-associated human disease and suggest that this non-human primate model may facilitate tissue engineering and regenerative medicine efforts.  相似文献   
38.
目的:探讨超高CD34+采集的动员方案后序贯二次自体造血干细胞移植治疗难治性霍奇金淋巴瘤的疗效和安全性。方法:对1例经过多疗程一线、二线、新药、免疫等均难治的霍奇金淋巴瘤患者,予以IA+C方案化疗+G-CSF动员干细胞后采集出超高水平CD34+细胞,之后行自体造血干细胞移植,移植后获得完全缓解,再予序贯第二次自体造血干细胞移植进行巩固治疗。结果:总计输注单个核细胞数13.67×108/kg,CD34+细胞48.68×106/kg,第一次自体造血干细胞移植术后第7天造血功能恢复,复查全身PET-CT提示获得完全缓解,第二次自体造血干细胞移植术后第8天造血功能恢复,两次自体造血干细胞移植相关并发症均在可控范围内。结论:超高CD34+细胞采集的IA+C方案化疗+G-CSF动员可以让患者有机会进行多次自体造血干细胞移植,是临床动员的创新方案。对于难治性霍奇金淋巴瘤,序贯二次自体造血干细胞移植可达到更深层次缓解,且安全性较高,延长患者无疾病生存期及总生存期,为难治性霍奇金淋巴瘤治疗提供更多临床依据。  相似文献   
39.
40.
The aim of this paper is to present a method to produce macroporous thin membranes made of poly (ethyl acrylate-co-hydroxyethyl acrylate) copolymer network with varying cross-linking density for cell transplantation and prosthesis fabrication. The manufacture process is based on template techniques and anisotropic pore collapse. Pore collapse was produced by swelling the membrane in acetone and subsequently drying and changing the solvent by water to produce 100 microns thick porous membranes. These very thin membranes are porous enough to hold cells to be transplanted to the organism or to be colonized by ingrowth from neighboring tissues in the organism, and they present sufficient tearing stress to be sutured with surgical thread. The obtained pore morphology was observed by Scanning Electron Microscope, and confocal laser microscopy. Mechanical properties were characterized by stress–strain experiments in tension and tearing strength measurements. Morphology and mechanical properties were related to the different initial thickness of the scaffold and the cross-linking density of the polymer network. Seeding efficiency and proliferation of mesenchymal stem cells inside the pore structure were determined at 2 h, 1, 7, 14 and 21 days from seeding.  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