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   88240篇
  免费   7295篇
  国内免费   3055篇
耳鼻咽喉   1036篇
儿科学   1551篇
妇产科学   2331篇
基础医学   9466篇
口腔科学   1566篇
临床医学   9934篇
内科学   13867篇
皮肤病学   1550篇
神经病学   4438篇
特种医学   3542篇
外国民族医学   6篇
外科学   10641篇
综合类   11351篇
现状与发展   12篇
一般理论   11篇
预防医学   6535篇
眼科学   1634篇
药学   8294篇
  49篇
中国医学   4277篇
肿瘤学   6499篇
  2024年   170篇
  2023年   757篇
  2022年   1805篇
  2021年   3086篇
  2020年   2117篇
  2019年   2072篇
  2018年   2519篇
  2017年   2230篇
  2016年   2040篇
  2015年   3298篇
  2014年   4222篇
  2013年   5106篇
  2012年   7224篇
  2011年   7234篇
  2010年   5146篇
  2009年   4584篇
  2008年   5573篇
  2007年   5454篇
  2006年   5061篇
  2005年   4438篇
  2004年   3756篇
  2003年   3472篇
  2002年   2860篇
  2001年   2305篇
  2000年   1969篇
  1999年   1467篇
  1998年   585篇
  1997年   487篇
  1996年   456篇
  1995年   411篇
  1994年   387篇
  1993年   267篇
  1992年   723篇
  1991年   595篇
  1990年   549篇
  1989年   496篇
  1988年   428篇
  1987年   432篇
  1986年   361篇
  1985年   298篇
  1984年   230篇
  1983年   195篇
  1982年   125篇
  1981年   124篇
  1980年   106篇
  1979年   209篇
  1978年   163篇
  1977年   106篇
  1976年   120篇
  1975年   106篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Summary This study evaluates healing fractures of the femoral neck in dogs by using standard radiography, intraosseous venography, India ink staining and histology.The 45 animals were divided into three groups, one of which was not treated, but in the other two the fracture was fixed with a screw or two Kirschner wires.Our results suggest that, when intraosseous venography was positive, India ink injection was also positive, and the late phase of fracture healing was reached.
Résumé Etude de la consolidation des fractures du col fémoral chez le chien à l'aide des radiographies standard, de la phlébographie osseuse, de la coloration par l'encre de Chine et de l'examen anatomopathologique. Les animaux ont été divisés en trois groupes, dans l'un la fracture n'a pas été traitée, dans les deux autres elle a été fixée soit par une vis, soit par deux broches de Kirschner. Les résultats tendent à montrer que lorsque la phlébographie est positive, la coloration par l'encre de Chine l'est également et que la phase ultime de la consolidation est atteinte.
  相似文献   
82.
【目的】探讨端粒酶作为脑膜瘤标志物 ,在肿瘤良恶性鉴别、恶性程度评估以及预后预测等方面的意义。【方法】利用TRAP ELISA方法定量检测 6 1例 (份 )肿瘤标本端粒酶的活性 (以ΔA =A4 50 -A690 表示 ) ,结合肿瘤的分类和患者的临床资料 ,分析端粒酶活性作为肿瘤良恶性及判断预后的标记物的可行性。另取正常脑组织标本 2 0例作为对照。【结果】 30例脑膜瘤中 ,2 9例脑膜瘤均未测到端粒酶活性 ;1例端粒酶阳性 (阳性率 3 3%) ,ΔA =0 2 37;全组ΔA平均值 =0 0 49。 15例恶性脑膜瘤中 14例呈端粒酶阳性 (93%) ,ΔA =1 2 37~ 2 5 16 ;1例端粒酶阴性 ,ΔA =0 0 76 ,全组ΔA平均值 =1 6 30。 16例复发性脑膜瘤端粒酶均阳性 (10 0 %) ,ΔA =1 0 34~ 1 4 78,平均 1 2 5 5。脑膜瘤和复发性脑膜瘤、脑膜瘤和恶性脑膜瘤的端粒酶的阳性率和酶活性表达强度方面差异明显 (P分别为 <0 0 0 1、<0 0 1和 <0 0 0 0 5、<0 0 1)。 2 0例正常脑组织中未检测到端粒酶活性。【结论】端粒酶活性的激活在恶性脑膜瘤和复发性脑膜瘤中是较常见的现象。端粒酶作为肿瘤标志物 ,在脑膜瘤的良恶性鉴别、恶性程度评估、预后预测等方面具有重要的意义。  相似文献   
83.
【目的】了解手术创伤对术后全身炎症反应综合征 (SIRS)的影响。【方法】搜集外科重症监护室 (SICU) 335例患者的术后资料 ,分析不同手术组SIRS发病率 ;手术时间、失血量与SIRS持续时间的关系 ;SIRS持续时间与术后并发症的关系。【结果】术后SIRS发病率为 75 8% ,大手术高达 92 4 % ;无并发症患者失血量与SIRS持续时间呈正相关 (r1=0 783,P<0 0 1) ,手术时间与SIRS持续时间呈正相关 (r2 =0 398,P <0 0 1) ;随着SIRS持续时间延长 ,并发症发病率显著增高 (P<0 0 5 )。【结论】术后SIRS发生、发展与手术创伤密切相关 ;监测SIRS进程有助于及早发现并发症  相似文献   
84.
目的 探讨腹腔镜下盆腔腹膜移植阴道成型术在妇科临床中的应用。方法使用特制的腹膜推进器行腹腔镜下盆腔腹膜移植阴道成型术。结果 术后成型的阴道上皮化良好,阴道无塌陷,性生活满意。结论 该术式损伤小、效果好、术后恢复快,是目前较理想的阴道成型方法。  相似文献   
85.
Serine hydroxymethyltransferase (SHMT) provides activated one-carbon units required for the biosynthesis of nucleotides, protein, and methyl group by converting serine and tetrahydrofolate to glycine and N(5),N(10)-methylenetetrahydrofolate. It is postulated that SHMT activity is associated with the development of methotrexate resistance and the in vivo activity of SHMT is regulated by the binding of N(5)-CHO-THF, the rescue agent in high-dose methotrexate chemotherapy. The aim of this study is to advance our understanding of the folate-mediated one-carbon metabolism in zebrafish by characterizing zebrafish mitochondrial SHMT. The cDNA encoding zebrafish mitochondrial SHMT was cloned, overexpressed in Escherichia coli, and purified with a three-step purification protocol. Similarities in structural, physical, and kinetic properties were revealed between the recombinant zebrafish mitochondrial SHMT and its mammalian orthologs. Surprisingly, leucovorin significantly inhibits the aldol cleavage of serine catalyzed by zebrafish cytosolic SHMT but inhibits to a lesser extent the reaction catalyzed by the mitochondrial isozyme. This is, to our knowledge, the first report on zebrafish mitochondrial folate enzyme as well as the differential inhibition of leucovorin on these two SHMT isoforms. Western blot analysis revealed tissue-specific distribution with the highest enrichment present in liver for both cytosolic and mitochondrial SHMTs. Intracellular localization was confirmed by confocal microscopy for both mitochondrial and cytosolic SHMTs. Unexpectedly, the cytosolic isoform was observed in both nucleus and cytosol. Together with the previous report on zebrafish cytosolic SHMT, we suggest that zSHMTs can be used in in vitro assays for folate-related investigation and antifolate drug discovery.  相似文献   
86.
87.
复杂主动脉病变的腔内血管外科治疗   总被引:3,自引:1,他引:2  
目的 探讨复杂主动脉病变的腔内血管外科治疗方法。方法 对21例合并有内脏动脉缺血等复杂的主动脉病变,双球管定位下经锁骨上动脉到股动脉交换导丝以确保真腔内植入带膜支架,对真腔完全被假腔压闭的患者采取真腔内加压推进以通过导丝,用超长带膜支架来封堵大破口治疗夹层合并巨大假性动脉瘤形成,对夹层合并腹主动脉瘤患者采取血管腔内技术联合开腹手术等方法。结果 术后内漏3例,其中2例7 d后停止,1例漏血持续存在。3例主动脉创伤术后完全康复,余18例复杂主动脉夹层术后即时造影示瘘口已被完整覆盖,假腔无血漏入,内脏动脉等恢复真腔供血。18例中6例合并肠管缺血,3例合并肾动脉缺血,3例肠管缺血、肾动脉缺血,2例腹主动脉真腔完全被假腔压迫,以及2例合并下肢缺血术后均逐渐恢复,无脏器及肢体缺血坏死发生。2例合并腹主动脉瘤夹层行支架型人工血管封闭夹层破口后行开腹手术切除腹主动脉瘤、人工血管置换。16例随访5~36个月,平均22.3月,1例内漏持续存在,但假腔未继续加大,其余患者存活良好。结论 对复杂的主动脉病变的治疗,通过对腔内血管外科技术进行改进,并适当结合传统手术方法,使某些过去被认为不能够治疗的复杂主动脉病变可得以成功治疗。  相似文献   
88.
The influence of age on the regional arterial and venous effects of serotonin (5-HT) was investigated in 13 young (aged 22-31 years) and seven older (aged 50-69 years) healthy volunteers. Single-dose infusions of 5-HT (1, 10, and 80 ng/kg/min) and of the 5-HT2 receptor antagonist ritanserin (50, 150, and 500 ng/kg/min) were administered into the brachial artery. Subsequently, the relative arterial and venous effects of the highest dose of 5-HT were investigated. Forearm blood flow (FBF) and maximum venous outflow (MVO) were measured by venous occlusion plethysmography. Heart rate (HR) and intraarterial (i.a.) blood pressure were recorded semicontinuously. In both age groups, 5-HT induced an initial transient arterial dilation, followed by a persistent increase in FBF for the doses of 1 and 10 ng/kg/min and a relative small decrease in FBF for the highest dose. In both age groups, the highest dose of 5-HT induced a similar large reduction in MVO (p less than 0.05 for both). The reduction in MVO was attenuated by ritanserin (500 ng/kg/min, p less than 0.05 for both groups). In the younger subjects, this dose of ritanserin also unmasked an arterial dilator effect of the highest dose of 5-HT (p less than 0.05). The single infusions of ritanserin did not influence FBF significantly in either study group. No significant differences were observed between the age groups. These results show that in the forearm of healthy subjects arterial and venous vascular responses to 5-HT were not age-related. In the arterial vascular bed, 5-HT acted predominantly as a vasodilator; at high doses, mainly venous vasoconstriction was observed.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
89.
BACKGROUND AND PURPOSE: This study investigated the characteristics of intussusception in Taiwanese children of different age groups, including the incidence, length of hospitalization and hospital costs. METHODS: Children with a diagnosis of intussusception who were hospitalized from 1999 through 2001 were identified from a nationwide health insurance claims database. The incidence of intussusception was calculated by age, gender, and season. Length of hospitalization and hospital costs were also analyzed. RESULTS: A total of 6988 cases of intussusception were identified in Taiwan from 1999 to 2001. Among them, 4859 cases occurred in children below 15 years of age. The average incidence among children below age 15 years was 34.5 per 100,000, with a peak incidence of 118.8 per 100,000 observed among children younger than 24 months old. The highest incidence of intussusception in Taiwanese children occurred between 12 and 24 months of age. According to the data for patients below 15 years of age hospitalized for intussusception in year 2000, males were more likely to be affected than females (61.3% vs 38.7%). Intussusception-related hospitalizations were rare in infants in the first few months of life, increased in those 6 to 12 months old, and peaked among children 1 to 3 years old. Among the 952 patients with intussusception admitted to hospitals in 2000, 297 (31.2%) received surgery, incurring higher median medical costs (New Taiwan Dollars [NT dollars] 42,265 or US dollars 1234) and longer median hospital stay (6.2 days) than the 655 patients who did not require surgery (NT dollars 6290 or US dollars 185 for hospitalization of 2.4 days). CONCLUSIONS: The study found that the incidence of intussusception peaked in the second year of life in Taiwanese children. There was also a male predominance and lack of seasonal variation in incidence.  相似文献   
90.
Tumor metastasis to the pancreas is a rare but recognized cause of acute pancreatitis. Autopsy series have reported a 24-40% of pancreatic involvement in small cell lung cancer. However, only a very few cases of tumor-induced acute pancreatitis have been described. Budd-Chiari syndrome complicating lung cancer is a rarely reported condition. We report a 68-year-old woman with extensive small cell lung cancer with the unusual initial presentation of both acute pancreatitis and acute Budd-Chiari syndrome. This patient suffered from progressive epigastralgia for 3 weeks. Severe epigastralgia with radiation to back and progressive jaundice developed 2 days prior to admission. After admission, the liver enlarged rapidly and the ascites increased markedly. Chest roentgenogram showed a mass lesion over the left lower lung field. Poorly differentiated carcinoma cells were found in ascites and bone marrow. The patient died on the ninth day of hospitalization before chemotherapy was initiated. Prompt diagnosis of extensive-stage small cell lung cancer may allow early chemotherapy treatment which favorably influences recovery when the pancreatitis is mild. Although prolonged survival might have been expected had this patient recovered from pancreatitis and received chemotherapy, diagnosis was delayed due to difficulty in immunohistochemical diagnosis of the tumor and the unusual clinical presentation. The use of stains employing antibodies against neurofilament and neuron-specific enolase cell antigens is important for early diagnosis of poorly differentiated metastatic tumor 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