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   42560篇
  免费   4351篇
  国内免费   3041篇
耳鼻咽喉   300篇
儿科学   687篇
妇产科学   593篇
基础医学   4847篇
口腔科学   699篇
临床医学   5726篇
内科学   6551篇
皮肤病学   442篇
神经病学   2279篇
特种医学   1390篇
外国民族医学   24篇
外科学   4250篇
综合类   7211篇
现状与发展   12篇
一般理论   3篇
预防医学   3280篇
眼科学   962篇
药学   4572篇
  47篇
中国医学   2580篇
肿瘤学   3497篇
  2024年   188篇
  2023年   781篇
  2022年   1886篇
  2021年   2415篇
  2020年   1843篇
  2019年   1557篇
  2018年   1590篇
  2017年   1536篇
  2016年   1397篇
  2015年   2032篇
  2014年   2432篇
  2013年   2330篇
  2012年   3315篇
  2011年   3637篇
  2010年   2216篇
  2009年   1817篇
  2008年   2304篇
  2007年   2107篇
  2006年   2041篇
  2005年   1930篇
  2004年   1406篇
  2003年   1280篇
  2002年   1121篇
  2001年   913篇
  2000年   879篇
  1999年   949篇
  1998年   545篇
  1997年   541篇
  1996年   402篇
  1995年   355篇
  1994年   287篇
  1993年   210篇
  1992年   279篇
  1991年   222篇
  1990年   191篇
  1989年   192篇
  1988年   161篇
  1987年   141篇
  1986年   127篇
  1985年   112篇
  1984年   52篇
  1983年   37篇
  1982年   22篇
  1981年   20篇
  1980年   19篇
  1979年   20篇
  1978年   13篇
  1974年   10篇
  1971年   10篇
  1970年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
本文简介海南岛的自然地理、啮齿动物地理区划和社会经济(包括人口数、性别年龄分布、人工植被、耕作习惯等)与钩端螺旋体病发生或流行有关的自然因素.扼要报告自1958─1991年以来各年度该病的发病率与病死率,比较了50─90年代总的发病态势是低→高→低,并略作了分析。  相似文献   
102.
103.
Interactions of LDL and modified LDL with mesangial cells and matrix.   总被引:7,自引:0,他引:7  
Hyperlipidemia may play a role in the progression of diabetic and other renal diseases. Low density lipoprotein (LDL) and other proteins including extracellular matrix components undergo nonenzymatic glycation in vivo. We examined the effects of glycation of LDL as occurs in diabetes (4 to 8%) on binding and uptake by mesangial cells and their proliferation. The glycation of LDL (g-LDL) significantly decreased its binding and uptake by mesangial cells by 15 to 20%, indicating that glycated LDL binds to the LDL receptor, but with lower affinity than LDL. Both LDL and g-LDL modestly stimulated [3H] thymidine incorporation into mesangial cells at 5 to 10 micrograms/ml. Native, oxidized (Ox-LDL) and glycated LDL all bound to the extracellular matrix generated by rat mesangial cells in culture. The binding of LDL, Ox-LDL and g-LDL to mesangial matrix was two to four times higher than to mesangial cells. Binding of LDL and g-LDL was significantly higher to glycolaldehyde modified matrix, which serves as an in vitro model for nonenzymatic glycation end-product cross-linking of matrix which occurs in long-standing diabetes. Based on these findings, we propose that glycation of LDL decreases its binding and uptake by the LDL receptor of mesangial cells and may slow its catabolism. Furthermore, LDL bound to extracellular mesangial matrix can undergo oxidation and generate cytotoxic LDL components. This process may be further enhanced by advanced glycation of the mesangial matrix in diabetes, contributing to glomerular pathology.  相似文献   
104.
介绍营养补充品中刺激剂的毛细管气相色谱和气相色谱质谱联用检测方法.试样采用碱提,液-液分配提取,以HP-5毛细管柱为分离柱,用氮磷检测器测定.实验结果表明:该方法操作简便,分析速度快,结果可靠.添加平均回收率为75.4%~143.1%,相对标准偏差为0.27%~5.5%,检出限为5~40μg/L.  相似文献   
105.
OBJECTIVE: To observe the morphological changes of Balb/C mouse embryonic stem cells following directed differentiation into pancreatic islet-like cell clusters (PICC) in vitro using atomic force microscope (AFM). METHODS: Balb/C mouse embryonic stem cells were first cultured into embryonic bodies (EBs) and allowed to differentiate spontaneously for 4 days. The cells were then transferred to gelatin-coated dishes for the EBs to attach and spread on the tissue culture plates, in the course of which a series of cell growth factors such as basic fibroblast growth factor (bFGF), insulin-like growth factor 1 (IGF-1) and nicotinamide were added into the culture medium at specific time points to induce directed differentiation of the stem cells into PICC. Immunocytochemistry was employed to detect the cells positive for insulin and glucagon, which were observed with AFM. RESULTS: The embryonic stem cells developed into cell clusters of different sizes, in which the cells were tightly arranged. Islet B cells were numerous in the center of clusters and darkly stained, but fewer in the peripherals with lighter stains. Islet A cells expressing glucagon were relatively fewer in the cell clusters, found mainly in the peripherals. Scanning of the insulin-positive clusters by AFM revealed large quantity of tissue fibers resembling nerve fibers that formed a reticular structure in disorderly arrangement. Numerous round granules were observed in the cytoplasm of almost identical sizes ranging from 0.5 to 1.0 mum in diameter. CONCLUSION: The cell clusters obtained by directed differentiation are mature in both morphology and function with also well organized structures.  相似文献   
106.
目的 观察胰岛素样生长因子结合蛋白-1对人血管内皮细胞的影响及其对胰岛素样生长因子的调节作用。方法 MTT比色法观察IGFBP-1及与IGF-1预混后对脐静脉内皮细胞(ECV304细胞株)生长影响。结果 IGFBP-1对内皮细胞ECV304的生长具有抑制作用且与剂量成正比;预混后各组IGF-1促细胞生长作用明显被抑制。结论 IGFBP-1既可以直接也可以通过调节IGF-1抑制血管内皮细胞生长。  相似文献   
107.
1972年出土的<武威汉代医简>第9、10两简有"五(疒夅)"及"石(疒夅)"、"血(疒夅)"、"膏(疒夅)"、"泔(疒夅)"的记载.就其病名与症状的描述而言,颇似当今的淋证.本文就两简中的"(疒夅)"、"泔(疒夅)"、"五(疒夅)"进行探讨,认为"(疒夅)"是多义字,有罢病、淋证等含义.同时又是"癃"的省写,故"(疒夅)"字即"癃"字,属"淋证"."泔(疒夅)",为米泔汁样小便,伴小便频数涩痛的症状,类似于当今临床"白浊"的部分表现."五(疒夅)"中的第五淋尚难以确定.  相似文献   
108.
目的 回顾性总结32例直肠癌根治会阴部造口术后二期股薄肌移植肛门成形术的治疗效果。方法 采用Williams 5级评分法对重建前后肛门功能进行评价。结果 二期股薄肌移植肛门成形术前,32例患者肛门功能均在4级以上[4级28.4%(9/32),5级71.6%(23/32)],二期股薄肌移植肛门成形术后肛门功能明显好转。结论 二期股薄肌移植肛门成形术是直肠癌根治会阴部造口术后有效的肛门重建手段。  相似文献   
109.
Objective To compare the clinical efficacy of postoperative intraperitoneal chemotherapy combined with systemic chemotherapy to systemic chemotherapy alone for serosa-involved colorectal cancer. Methods According to the criteria of serosa-involving in colorectal cancer, 332 cases were divided into 2 groups prospectively without randomization. Study group (n=166) was treated with intraperitoneal chemotherapy combined with systemic chemotherapy, and control group (n=166) with systemic chemotherapy alone. Incidence of local recurrence, peritoneal metastasis, hepatic metastasis, other distant metastasis and 3-year, 5-year overall survival (OS) rate of two groups were compared. Results 3-year and 5-year OS rates of stage Ⅱ B in study group were similar to those in control group (χ2=0.612,P=0.434). The above rates of stage Ⅲ in study group were higher than those in control group (χ2=3.989,P=0.046). Either the study group or the control group, the 3-year and 5-year OS rates of patients undergone laparoscopic surgery or open surgery were similar (P=0.839, P=0.172). Incidences of local recurrence, peritoneal metastasis and hepatic metastasis in study group were 1.9%, 3.8% and 3.8% respetively, lower than those in control group (8.2%,9.5% and 10.1%,P<0.05). Distant metastasis rate in study group was similar to that in control group. In study group, intraperitoneal chemotherapy regimen with Oxaliplatin had lower rates of peritoneal metastasis and hepatic metastasis as compared to that with Cisplatin (0.9% vs 8.8% ,P=0.019), while the incidences of local recurrence and other distant metastasis were similar. Conclusions Postoperative intraperitoneal chemotherapy combined with systemic chemotherapy improves 3-year and 5-year overall survival rates in patients with stage Ⅲ serosa-involved colorectal cancer, and decreases local recurrence, peritoneal metastasis and liver metastasis rate, especially when intraperitoneal chemotherapy regimen contains Oxaliphtin. Comparing with open surgery, laparoscopic surgery dose not improve 3-year and S-year overall survival rates in patients receiving combined chemotherapy or systemic chemotherapy alone.  相似文献   
110.
Amniotic fluid mesenchymal stem cells have the ability to secrete neurotrophic factors that are able to promote neuron survival in vitro. The purpose of this study was to evaluate the effects of neurotrophic factors secreted by rat amniotic fluid mesenchymal stem cells on regeneration of sciatic nerve after crush injury. Fifty Sprague-Dawley rats weighing 250-300 g were used. The left sciatic nerve was crushed with a vessel clamp. Rat amniotic fluid mesenchymal stem cells embedded in fibrin glue were delivered to the injured nerve. Enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry were used to detect neurotrophic factors secreted by the amniotic fluid mesenchymal stem cells. Nerve regeneration was assessed by motor function, electrophysiology, histology, and immunocytochemistry studies. Positive CD29/44, and negative CD11b/45, as well as high levels of expression of brain-derived neurotrophic factor, glia cell line-derived neurotrophic factor, ciliary neurotrophic factor (CNTF), nerve growth factor, and neurotrophin-3 (NT-3) were demonstrated in amniotic fluid mesenchymal stem cells. Motor function recovery, the compound muscle action potential, and nerve conduction latency showed significant improvement in rats treated with amniotic fluid mesenchymal stem cells. ELISA measurement in retrieved nerves displayed statistically significant elevation of CNTF and NT-3. The immunocytochemical studies demonstrated positive staining for NT-3 and CNTF in transplanted cells. The histology and immunocytochemistry studies revealed less fibrosis and a high level of expression of S-100 and glial fibrillary acid protein at the crush site. Rat amniotic fluid mesenchymal stem cells may facilitate regeneration in the sciatic nerve after crush injury. The increased nerve regeneration found in this study may be due to the neurotrophic factors secreted by amniotic fluid mesenchymal stem cells.  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