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   16124篇
  免费   1468篇
  国内免费   944篇
耳鼻咽喉   147篇
儿科学   161篇
妇产科学   283篇
基础医学   2003篇
口腔科学   265篇
临床医学   2139篇
内科学   2600篇
皮肤病学   182篇
神经病学   842篇
特种医学   561篇
外国民族医学   5篇
外科学   1912篇
综合类   2134篇
现状与发展   1篇
一般理论   6篇
预防医学   1071篇
眼科学   484篇
药学   1645篇
  15篇
中国医学   742篇
肿瘤学   1338篇
  2024年   45篇
  2023年   242篇
  2022年   576篇
  2021年   792篇
  2020年   551篇
  2019年   550篇
  2018年   554篇
  2017年   502篇
  2016年   490篇
  2015年   713篇
  2014年   868篇
  2013年   813篇
  2012年   1163篇
  2011年   1166篇
  2010年   845篇
  2009年   656篇
  2008年   771篇
  2007年   786篇
  2006年   823篇
  2005年   762篇
  2004年   635篇
  2003年   610篇
  2002年   566篇
  2001年   446篇
  2000年   385篇
  1999年   392篇
  1998年   272篇
  1997年   240篇
  1996年   179篇
  1995年   181篇
  1994年   114篇
  1993年   97篇
  1992年   108篇
  1991年   93篇
  1990年   72篇
  1989年   69篇
  1988年   65篇
  1987年   62篇
  1986年   42篇
  1985年   42篇
  1984年   22篇
  1983年   14篇
  1981年   14篇
  1980年   12篇
  1979年   21篇
  1976年   10篇
  1974年   15篇
  1973年   13篇
  1972年   10篇
  1969年   11篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
ContextValerian extract capsule (VEC) is an effective Chinese patent medicine used for gastrointestinal (GI) diseases.ObjectiveTo investigate the detailed pharmacological activity for VEC clinical effects in GI diseases.Materials and methodsSprague-Dawley rats were divided into six groups: control, model, and drug-treated (VEC-L, VEC-M, VEC-H, and teprenone). Rats were orally administered VEC (124, 248, 496 mg/kg) and teprenone (21.43 mg/kg) for 3 consecutive days. After 1 h, the five groups (except the control group) were orally given ethanol (10 mL/kg) for 1 h or indomethacin (80 mg/kg) for 7 h. The spasmolytic activity of VEC (0.01–1 mg/mL) on ACh/BaCl2-induced New Zealand rabbit smooth muscle contraction was performed. The C57BL/6 mice carbon propelling test evaluated the effects of VEC (248–992 mg/kg) on intestinal motility in normal and neostigmine/adrenaline-induced mice.ResultsCompared with the model group, VEC treatment reduced the gastric lesion index and mucosal damage. Further experiments showed that the pathological ameliorative effect of VEC was accompanied by augmentation of the enzymatic antioxidant system and cytoprotective marker (COX-1, p < 0.01; PGI2 p < 0.05;), along with the alleviation of the levels of MPO (ethanol: 15.56 ± 0.82 vs. 12.15 ± 2.60, p < 0.01; indomethacin: 9.65 ± 3.06 vs. 6.36 ± 2.43, p < 0.05), MDA (ethanol: 1.66 ± 0.44 vs. 0.81 ± 0.58, p < 0.01; indomethacin: 1.71 ± 0.87 vs. 1.09 ± 0.43, p < 0.05), and inflammatory mediators. VEC decreased the high tone induced by ACh/BaCl2 and promoted intestinal transit in normal and neostigmine/adrenaline-induced mice.Discussion and conclusionsVEC showed a potential gastroprotective effect, suggesting that VEC is a promising phytomedicine for the treatment of GI diseases.  相似文献   
82.
The paper focused on an experimental study on the microstructural, mechanical, and wear characteristics of 15 wt.% alumina (Al2O3) particulates with an average particle size of 20 µm, reinforced in Al2014 alloy matrix composite as-cast and heat-treated samples. The metal matrix composite (MMC)samples were produced via a novel two-stage stir-casting technique. The fabricated composite samples were subjected to evaluate hardness, tensile strength, fatigue behavior and wear properties for both as cast and T6 heat-treated test samples. The Al2014 alloy and Al2014-15 wt.% Al2O3 MMCs were in solution for 1 h at a temperature of 525 °C, quenched instantly in cold water, and then artificially aged for 10 h at a temperature of 175 °C. SEM and X-ray diffraction analyses were used to investigate the microstructure and dispersion of the reinforced Al2O3 particles in the composite and the base alloy Al2014. The obtained results indicated that the hardness, tensile and fatigue strength and wear resistance increased when an amount of Al2O3 particles was added, compared to the as-cast Al2014 alloy and it was observed that after subjecting the same composite samples to heat treatment, there was further enhancement in the mechanical and wear properties in the Al2014 matrix alloy and Al2014-15 wt.% Al2O3 composite samples.  相似文献   
83.
Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt was investigated using a tensile test and finite element analysis (FEA). The microstructure of the as-received bolt consisted of a high proportion of α phase, some β phase, and a small amount of α′ phase formed via martensite phase transformation during the rammer process. The experimental force–displacement curves revealed an average yield load of 55.9 kN and a breaking load of 67.65 kN. The corresponding yield strength was calculated to be 0.9 GPa, which was smaller than the standard value of TC4. This was attributed to the preload-induced stress concentration on the thread surface, leading to obvious strain hardening, which can lead to crack initiation. The effect of preload was further confirmed by the fractographies in which the initial crack was observed on the thread surface. The fractographies suggested that hybrid fracture occurred on the tensile loaded bolt. The initial failure was brittle fracture on the thread surface, transforming into ductile fracture in the screw. The results can contribute to understanding the effect of preload on the load carry capacity of high-lock bolts and provide a strategy to design its assembly specification.  相似文献   
84.
扬琴是一种有着广泛的世界性和民族性的击弦乐器,于明代自国外传至中国。四百多年采扬琴在中国传统音乐文化环境的影响下,不断和民间音乐融合,并在一代代的扬琴艺人的探索和创新中,发展成了具有中国特色的民族乐器,成为世界扬琴三大体系之一的中国扬琴体系,同时形成了中国传统扬琴的四大流派。  相似文献   
85.
In this study, we aimed to determine whether a postnatal trans fat diet (TFD) could aggravate prenatal bisphenol A (BPA) exposure effects on offspring’s small intestine and adulthood obesity, due to the relatively sparse findings on how the interaction between these two variables interrupt the small intestinal cells. Twelve pregnant rats were administered with either unspiked drinking water (control; CTL) or BPA-spiked drinking water throughout pregnancy. Twelve weaned pups from each pregnancy group were then given either a normal diet (ND) or TFD from postnatal week (PNW) 3 until PNW14, divided into control offspring on normal diet (CTL-ND), BPA-exposed offspring on normal diet (BPA-ND), control offspring on trans fat diet (CTL-TFD), and BPA offspring on trans fat diet (BPA-TFD) groups. Body weight (BW), waist circumference, and food and water intake were measured weekly in offspring. At PNW14, small intestines were collected for global DNA methylation and histological analyses. Marked differences in BW were observed starting at PNW9 in BPA-TFD (389.5 ± 10.0 g; p < 0.05) relative to CTL-ND (339.0 ± 7.2 g), which persisted until PNW13 (505.0 ± 15.6 g). In contrast, water and food intake between offspring were significantly different (p < 0.01–0.05) at earlier ages only (PNW4–6 and PNW7–9, respectively). Furthermore, substantial differences in the general parameters of the intestinal structures were exclusive to ileum crypt length alone, whereby both BPA-ND (150.5 ± 5.1 μm; p < 0.001), and BPA-TFD (130.3 ± 9.9 μm; p < 0.05) were significantly longer than CTL-ND (96.8 ± 8.9 μm). Moreover, BPA-ND (2.898 ± 0.147%; p < 0.05) demonstrated global small intestinal hypermethylation when compared to CTL-ND and CTL-TFD (1.973 ± 0.232% and 1.913 ± 0.256%, respectively). Prenatal BPA exposure may significantly affect offspring’s physiological parameters and intestinal function. Additionally, our data suggest that there might be compensatory responses to postnatal TFD in the combined BPA prenatal group (BPA-TFD).  相似文献   
86.
目的:探讨枸杞多糖、黄芪多糖对家兔动脉粥样硬化(As)脂质过氧化及炎症反应的干预机制。方法:将48只雄性新西兰大白兔随机分为4组:正常组(12只),As模型组(12只),枸杞多糖(LBP)治疗组和黄芪多糖(APS)治疗组。10周后,测定各组空腹甘油三酯(TG)、总胆固醇(TCh)、高密度脂蛋白胆固醇(HDL-C)、一氧化氮(NO)、丙二醛(MDA)、C反应蛋白(CRP)、内皮素-1(ET-1)的含量以及超氧化物歧化酶(SOD)活性,并计算HDL-C/TCh,同时计算主动脉内膜粥样斑块面积。结果:模型组与正常组比较,TG、TCh、ET-1、NO、CRP、MDA明显升高(P<0.01),HDL-C/TCh、SOD活性明显下降(P<0.01),主动脉内膜粥样斑块面积较大;而LBP和APS治疗组与模型组比较,TG、ET-1、NO、CRP明显下降(P<0.01),HDL-C/TCh和SOD活性明显升高(P<0.01),主动脉内膜粥样斑块面积明显减少(P<0.01)。结论:枸杞多糖和黄芪多糖对动脉粥样硬化有明显的预防和治疗作用,机制可能与降低血脂、抗氧化、调节免疫等功能有关。  相似文献   
87.
BackgroundTo study the influence of pathological responses (PR) after transcatheter arterial chemoembolization (TACE) on incidences of microvascular invasion (MVI) and early recurrence in hepatocellular carcinoma (HCC) patients.MethodsBetween 2013 to 2015, consecutive HCC patients who underwent liver resection with “curative” intent at three hospitals were enrolled in this study. Patients with different areas of PR after preoperative TACE were compared with those without preoperative TACE on the incidences of MVI, early recurrence rates and patterns of recurrence before and after propensity score matching (PSM).ResultsOf 1,970 patients, 737 patients who received preoperative TACE were divided into three groups according to the areas of PR: ≥90% (n=226), 60–90% (n=447), and <60% (n=64). PR ≥90% was an independent protective factor of incidences of MVI [odds ratio (OR), 0.144; 95% confidence interval (CI), 0.082–0.245, P<0.001) and early recurrence (HR, 0.742; 95% CI, 0.561–0.963, P=0.032); while PR<60% was an independent risk factor of incidences of MVI (OR, 6.076; 95% CI, 3.004–11.728, P<0.001) and early recurrence (HR, 1.428; 95% CI, 1.095–1.929; P=0.009). Furthermore, patients with PR <60% were significantly more likely to develop multiple intrahepatic recurrences involving multiple hepatic segments when compared with patients without preoperative TACE.ConclusionsThis study indicated the area of PR after TACE was closely associated with the incidences of MVI and early tumor recurrence. Patients with PR <60% were at significantly higher risks of having more MVI, early and multiple tumor recurrences  相似文献   
88.
Dendritic cells (DCs) play a critical role in controlling T helper 2 (Th2) cell-dependent diseases, but the signaling mechanism that triggers this function is not fully understood. We showed that p38α activity in DCs was decreased upon HDM stimulation and dynamically regulated by both extrinsic signals and Th2-instructive cytokines. p38α-specific deletion in cDC1s but not in cDC2s or macrophages promoted Th2 responses under HDM stimulation. Further study showed that p38α in cDC1s regulated Th2-cell differentiation by modulating the MK2−c-FOS−IL-12 axis. Importantly, crosstalk between p38α-dependent DCs and Th2 cells occurred during the sensitization phase, not the effector phase, and was conserved between mice and humans. Our results identify p38α signaling as a central pathway in DCs that integrates allergic and parasitic instructive signals with Th2-instructive cytokines from the microenvironment to regulate Th2-cell differentiation and function, and this finding may offer a novel strategy for the treatment of allergic diseases and parasitic infection.  相似文献   
89.
杨琳  赵蕾  徐超  毕涛  慈维苹  万瑾 《疑难病杂志》2021,(4):383-385,390
回顾性分析2018年1月—2020年8月首都医科大学附属北京安贞医院风湿免疫科治疗的白塞综合征患者20例的临床及影像学检查资料.20例患者中,男4例,女16例,平均年龄41.2岁,平均病程17.0年.超声、CT及MR检查发现心血管系统受累13例,主要表现为主动脉瓣脱垂并重度关闭不全,主动脉瘤、主动脉假性动脉瘤、主动脉溃...  相似文献   
90.
目的 :建立青藤碱的透皮吸收研究方法 ,比较青藤碱渗透小鼠皮肤、裸鼠皮肤、家兔皮肤、大鼠皮肤、猪耳皮肤及人体皮肤的透皮吸收行为。方法 :青藤碱的含量测定采用HPLC法 ,计算透皮速率常数J,比较青藤碱渗透上述 6种实验皮肤的透皮速率常数。结果 :青藤碱透过 6种皮肤的透皮速率常数分别为 46 6 7± 16 35、40 34± 8 40、17 6 0± 9 46、2 3 71± 8 79、44 5 6± 11 2 7、38 33± 13 81。结论 :青藤碱对 6种皮肤的渗透性 ,以裸鼠及猪耳皮肤的透皮速率常数与人体皮肤较为接近。  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