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   21033篇
  免费   1492篇
  国内免费   425篇
耳鼻咽喉   87篇
儿科学   513篇
妇产科学   537篇
基础医学   3271篇
口腔科学   458篇
临床医学   1740篇
内科学   2793篇
皮肤病学   280篇
神经病学   1355篇
特种医学   715篇
外国民族医学   4篇
外科学   1534篇
综合类   2464篇
现状与发展   2篇
预防医学   1242篇
眼科学   156篇
药学   2597篇
  6篇
中国医学   924篇
肿瘤学   2272篇
  2024年   97篇
  2023年   252篇
  2022年   454篇
  2021年   571篇
  2020年   524篇
  2019年   625篇
  2018年   646篇
  2017年   604篇
  2016年   651篇
  2015年   689篇
  2014年   1202篇
  2013年   1423篇
  2012年   1084篇
  2011年   1403篇
  2010年   996篇
  2009年   1039篇
  2008年   966篇
  2007年   1035篇
  2006年   932篇
  2005年   820篇
  2004年   764篇
  2003年   633篇
  2002年   509篇
  2001年   474篇
  2000年   437篇
  1999年   363篇
  1998年   297篇
  1997年   311篇
  1996年   239篇
  1995年   243篇
  1994年   233篇
  1993年   189篇
  1992年   150篇
  1991年   134篇
  1990年   157篇
  1989年   102篇
  1988年   92篇
  1987年   97篇
  1986年   80篇
  1985年   165篇
  1984年   215篇
  1983年   106篇
  1982年   149篇
  1981年   136篇
  1980年   112篇
  1979年   102篇
  1978年   80篇
  1976年   72篇
  1974年   75篇
  1973年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Cognitive decline is one of the serious complications associated with diabetes mellitus (T2DM) of type-2. In this reported work, the effect of aqueous sukkari dates seed extract (ASSE) was evaluated in T2DM-induced rats. T2DM was induced using intraperitoneal injection of nicotinamide and streptozocin (STZ) administration. The diabetic rats were then treated orally with 200 mg/kg and 400 mg/kg of dates seed extract for 30 days and results were compared with metformin-treated groups. The memory functions were assessed using three maze models. Glucose and insulin levels in the blood and acetylcholine, acetylcholinesterase brain homogenates were estimated. The results showed a significant reduction in transfer latency (TL) (p < 0.001) during the elevated plus maze (EPM) test. The novel object recognition (NOR) test revealed a longer exploration time (p > 0.05) with novel objects and a higher discrimination index (p > 0.05). The Y-maze test also showed a significant increase in the number of entries to the novel arm (p > 0.05) and the total number of entries in the trial (p > 0.01) as well as in test (p > 0.05) sessions. Reduction in blood glucose (p > 0.05) and improvement in blood insulin (p > 0.05) levels were also noted. Improvement in ACh levels (p > 0.001) with 400 mg/kg of ASSE and reduction in AChE (p > 0.001) with both doses of ASSE were also observed in the brain homogenates. The results of ASSE were found comparable with the metformin-treated rats. The estimation of phytochemical constituents displayed a significant presence of phenolic content. Further, molecular modeling studies showed ellagic acid, catechin, and epicatechin as the potential molecule interacting with GSK-3β, α-amylase, and AChE and may be responsible for observed bioactivity. In conclusion, ASSE has the ability to alleviate T2DM-related cognitive impairments.  相似文献   
72.
血清CA125半衰期判定卵巢上皮性癌预后的价值   总被引:2,自引:0,他引:2  
目的 探讨血清CA125半衰期在卵巢上皮性癌中的预后价值。方法 回顾性分析30例卵巢上皮性癌患者在化疗过程中血清CA125半衰期值(t1/2)与生存时间的关系。结果 血清CA125半衰期值(t1/2)≤20天组的中位生存时间为36个月,t1/2〉20天组中完全缓解率为27.3%,两者存在极显著差异(p=0.001)。多因素生存分析表明:CA125半衰期和细胞分级、残余瘤灶大小均是独立的预后因素。结  相似文献   
73.
Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain.We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh?/? mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys).Significant amounts of GA and 3-OHGA were detected in Gcdh?/? aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh?/? aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh?/? aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh?/? aggregates at DIV 14 and after exposure to Lys at DIV 8.This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh?/? brain cells. We described for the first time a decrease of chemokines in Gcdh?/? culture media which might contribute to brain cell injury in GA-I.  相似文献   
74.
〔目的〕分析福建口岸白纹伊蚊、中华按蚊和骚扰阿蚊细胞色素C氧化酶亚基I(COI)基因序列,为建立蚊种分子鉴定方法奠定基础。〔方法〕扩增并测定在福建口岸采集的白纹伊蚊、中华按蚊和骚扰阿蚊COI基因序列,与GenBank中相应序列进行对比分析。〔结果〕三蚊种COI基因扩增片段长度约500bp,A+T含量为65.61%~68.73%。核苷酸同源性分析结果表明,同一蚊种COI基因同源性为98.1%~100%,三蚊种间基因同源性为84.4%~87.7%;COI部分基因系统进化关系显示,三蚊种COI分子鉴定与形态学鉴定结果一致,阿蚊属与伊蚊属聚类为库蚊亚科,按蚊亚科位于系统进化树另一分支。〔结论〕COI基因核苷酸序列分析可应用于福建国境口岸三蚊种的区分,弥补形态特征信息量不足等传统分类鉴定方法的缺点,为建立外来或新发现蚊种分子鉴定方法奠定基础。  相似文献   
75.
刘志红 《中国妇幼保健》2009,24(33):4741-4742
目的:探讨检测血清CA125对上皮性卵巢癌的临床价值。方法:复习84例上皮性卵巢癌患者手术前后血清CA125水平,并结合临床病理相关资料进行分析。结果:术前血清CA125在浆液性癌和内膜样癌中明显高于黏液性癌(P<0.01),晚期明显高于早期(P<0.05),生存期大于5年者明显低于生存期小于5年者(P<0.01);术后复发者血清CA125水平明显高于未复发者(P<0.01),CA125半衰期>20天的复发率显著高于≤20天者(P<0.01)。结论:上皮性卵巢癌患者术前测定血清CA125水平可初步判断组织学类型、肿瘤分期并可预测患者生存期;术后监测血清CA125水平可及时发现复发者。  相似文献   
76.
Concrete tanks, in coke wastewater treatment plants, are exposed to aggressive wastewater with high ammonium and chloride content, deteriorating the concrete binder. Due to this, toxic compounds may migrate to the environment. The results of the experimental work presented confirmed the changes in the phase, microstructure and concentration of chlorides caused by the penetration of NH4Cl into the hardened cement paste in dry conditions. Geochemical modeling of the interactions between the aggressive solution, the cement stone matrix and the pore water was performed in order to track the destruction process effects. The results are useful for condition assessment of the structures operating under occasional immersion.  相似文献   
77.
Prenatal stress is considered as an early epigenetic factor able to induce long-lasting alterations in brain structures and functions. It is still unclear whether prenatal stress can induce long-lasting modifications in the hypothalamo-pituitary-adrenal axis. To test this possibility the effects of restraint stress in pregnant rats during the third week of gestation were investigated in the functional properties of the hypothalamo-pituitary-adrenal axis and hippocampal type I and type II corticosteroid receptors in the male offspring at 3, 21 and 90 days of age. Plasma corticosterone was significantly elevated in prenatally-stressed rats at 3 and 21 days after exposure to novelty. At 90 days of age, prenatally-stressed rats showed a longer duration of corticosterone secretion after exposure to novelty. No change was observed for type I and type II receptor densities 3 days after birth, but both receptor subtypes were decreased in the hippocampus of prenatally-stressed offspring at 21 and 90 days of life. These findings suggest that prenatal stress produces long term changes in the hypothalamo-pituitary-adrenal axis in the offspring.  相似文献   
78.
Summary An autopsy case of a 37-year-old woman with acute porphyria is reported. The patient began to complain of severe menstrual pains, and later developed serious peripheral neuropathy and various autonomic nervous symptoms.The autopsy revealed a marked loss and degeneration of axons and myelin sheaths in the peripheral nervous system (PNS), and prominent central chromatolysis of the spinal anterior horn cells. The predominant process of the peripheral neuropathy appeared to be axonal degeneration.Biochemical analysis showed a marked increase of delta-aminolevulinic acid (ALA), porphobilinogen, uroporphyrin, and coproporphyrin in the urine, and an increase of coproporphyrin and protoporphyrin in the stools and blood. In the analysis of the enzymatic activities of the liver and bone narrow, the activity of ALA synthetase (ALA-S) was markedly increased, and the activities of both uroporphyrinogen I synthetase (URO-S) and ferrochelatase were decreased. It was characteristic in this case that the enzymatic abnormalities found in both acute intermittent porphyria (AIP) and variegate porphyria (VP) coexisted.Biochemical analysis of the sciatic nerve showed an increase of ALA-S activity and a decrease of both URO-S and ALA dehydrase activities. This was the first report that indicated the presence of abnormal activities of the heme biosynthetic enzymes in the peripheral nerves of porphyric patients. The possibility was discussed that these enzymatic abnormalities of the heme biosynthesis in the peripheral nerve itself might be strongly related to the pathogenesis of the porphyric neuropathy.  相似文献   
79.
Purpose  The aim of this study was to assess the variation of probe rotation angles for detecting a single needle using sagittal images of transrectal ultrasonography (TRUS). Materials and methods  A phantom study was performed. One needle was inserted through each of 10 holes of the template, and variations in the probe rotation angles for detecting the needle were measured. Results  The mean variation of probe rotation for detecting a single needle was 17.0° (range 4°–25°). Slightly broader variation was seen for the needle in holes farther away from the probe. Conclusion  Probe rotation angles for detecting a single needle displayed considerable variation. Seed locations recognized on sagittal imaging by TRUS are thus indeterminate, and real-time dose calculations using TRUS for 125I seed implantation should be used with care.  相似文献   
80.
Lymphovascular invasion is considered to be a high-risk pathological feature after radical resection of gastric cancer, but the relationship between lymphovascular invasion and the prognosis of stage I gastric cancer is still controversial. Therefore, we used meta-analysis to systematically evaluate the relationship between lymphovascular invasion and the prognosis of stage I gastric cancer. Up to September 2, 2021, the databases of PubMed, EMBASE, Cochrane Library, CNKI, and Wanfang were searched. According to the inclusion and exclusion criteria, 2 researchers independently completed the screening of literature, extraction of data, and quality evaluation. Meta-analysis was performed using RevMan 5.4 software merged with HR and 95%CI. A total of 7508 patients with stage I gastric cancer were included in 9 studies, and the positive rate of lymphovascular invasion was 17%. Lymphovascular invasion was significantly associated with shorter overall survival (OS) (univariate: HR = 4.05, 95%CI: 1.91–8.58; multivariate: HR = 2.10, 95%CI: 1.37–3.22) and relapse-free survival (RFS) (univariate: HR = 4.79, 95%CI: 2.30–9.99; multiple: HR = 2.17, 95%CI: 1.56–3.00). This study indicates that lymphovascular invasion is an independent risk factor affecting the prognosis of patients with stage I gastric cancer, and can be used as a reference index for postoperative adjuvant therapy.  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