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   11126篇
  免费   488篇
  国内免费   84篇
耳鼻咽喉   57篇
儿科学   315篇
妇产科学   84篇
基础医学   1382篇
口腔科学   343篇
临床医学   625篇
内科学   2973篇
皮肤病学   434篇
神经病学   728篇
特种医学   444篇
外科学   1904篇
综合类   48篇
一般理论   1篇
预防医学   324篇
眼科学   297篇
药学   682篇
中国医学   18篇
肿瘤学   1039篇
  2023年   66篇
  2022年   152篇
  2021年   216篇
  2020年   120篇
  2019年   166篇
  2018年   201篇
  2017年   161篇
  2016年   187篇
  2015年   210篇
  2014年   260篇
  2013年   354篇
  2012年   558篇
  2011年   615篇
  2010年   347篇
  2009年   322篇
  2008年   578篇
  2007年   623篇
  2006年   578篇
  2005年   681篇
  2004年   656篇
  2003年   692篇
  2002年   712篇
  2001年   274篇
  2000年   271篇
  1999年   256篇
  1998年   178篇
  1997年   120篇
  1996年   134篇
  1995年   108篇
  1994年   104篇
  1993年   76篇
  1992年   136篇
  1991年   134篇
  1990年   139篇
  1989年   143篇
  1988年   120篇
  1987年   111篇
  1986年   96篇
  1985年   99篇
  1984年   93篇
  1983年   71篇
  1982年   34篇
  1981年   49篇
  1980年   47篇
  1979年   57篇
  1978年   45篇
  1977年   32篇
  1970年   31篇
  1968年   37篇
  1967年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A series of 1 beta-methylcarbapenem compounds, which have a 5'-substituted-N-methylpyrrolidin-3'-ylthio group as a C-2 side chain, have been prepared and their biological properties were investigated. Substitution with a methyl group on the nitrogen atom in the C-2 side chain effectively enhanced stability to renal dehydropeptidase-I as well as introduction of methylene spacer between the aminocarbonyl group and the pyrrolidine ring of the 5'-aminocarbonylpyrrolidin-3'-ylthio group.  相似文献   
32.
Phosphatidylserine is known to significantly accelerate the blood coagulation reaction. In a previous communication submitted for publication, we demonstrated that phosphatidylcholine, phosphatidylethanolamine and lysophosphatidylcholine showed effects on the blood coagulation reaction using the factor Xa-prothrombin reaction system, and discuss a new function of membrane phospholipids. The present study examined the role of phospholipids in the blood coagulation regulatory reaction (anticoagulation system), by studying the effects of phospholipids on the protein C/protein S reaction. We have established quantitative methods for measuring activated protein C activity and protein S activity, and used them to measure their activity after the addition of liposomes with different phospholipid compositions. We found that phosphatidylcholine inhibited activated protein C and protein S activities in a dose-dependent manner, as in the factor Xa-prothrombin reaction system. On the other hand, phosphatidylethanolamine and lysophosphatidylcholine showed no effect on activated protein C activity. Phosphatidylethanolamine inhibited and lysophosphatidylcholine accelerated coagulation activity in the factor Xa-prothrombin system, but such effects were not observed in the protein C/protein S reaction system. The coagulation and anticoagulation reactions are exquisitely balanced by thrombin, with a role both as a procoagulant and anticoagulant. Therefore, it is understandable that phosphatidylethanolamine and lysophosphatidylcholine show different effects in the factor Xa-prothrombin and protein C/protein S reaction systems. It appears that coagulation and anticoagulation reactions are co-ordinated and controlled by changes in phospholipid composition of the cellular membrane where the coagulation reaction takes place.  相似文献   
33.
34.
We report here the first described case of utilizing gadolinium-based contrast material as the contrast agent during a catheter intervention treatment for pulmonary artery stenosis. The patient, a male infant with complex heart disease associated with a right isomerism, had a history of severe allergic reaction to iodine-containing contrast agents. A combination of digital subtraction angiography and a gadolinium contrast agent, however, provided us with good-quality images both before and after balloon angioplasty without any associated complications. This method should therefore be considered as an alternative angiographic procedure in children with a high risk of iodine-related allergic complications.  相似文献   
35.
We present here a rare case of left-side catamenial pneumothorax, in which endometrial tissue pleura was found on the visceral pleura histologically. A chest roentogenogram confirmed the left pneumothorax, but did not reveal bullae or any associated anomalies, in a 41-year-old woman with three documented episodes of left-side pneumothorax occurring every menstruation. Video-assisted thoracoscopic surgery revealed not only tiny holes in the diaphragm, but also a scattered small brown spots on the visceral pleura. Histological examination of the lung sections revealed the existence of endometrial tissue on the visceral pleura with disrupted pleural elastic fibers. Our case suggests that cyclic erosion of the visceral pleura by the implanted endometrial tissue caused air leakage from the lung, in addition to the most accepted concept that air is aspirated into the thoracic cavity via the abdomen through the acquired fenestration of the diaphragm.  相似文献   
36.
Langerhans cell histiocytosis is currently regarded as a reactive proliferative process of Langerhans cells rather than a malignancy. The disease is characterized by Langerhans cell infiltration of skin, lung, bone and other organs. We report a 74-year-old man with Langerhans cell histiocytosis who had generalized hemorrhagic and crusted papules. He also had diabetes insipidus. Because he did not have any severe constitutional symptoms or failure of vital organs, we applied topical PUVA treatment to his skin lesions, which responded well to the therapy. Diabetes insipidus, however, remained, in spite of X ray radiotherapy for the pituiary lesion.  相似文献   
37.
38.
Abstract: Two autopsied female sibling cases of sudanophilic leukodystrophy are reported. Case A and case B were the second and third of seven siblings, and a sister and a brother died from severe progressive neurological disease with similar symptoms. Consanguineous marriages were noted in the family of both cases through the past three generations. Case A gradually developed intellectual deterioration and tetraplegia at the age of 29, progressed to akinetic mutism within one year and thereafter survived for 14 years. Neuropathologically, a severe atrophy and degeneration were noted in the white matter of the whole cerebrum, sparing the subcortical U-fibers. Myelin and axons were severely damaged with peripheral astrocytic gliosis. Case B developed similar clinical symptoms at the age of 20 and survived for 7 years in the state of akinetic mutism. Similar postmortem findings as those of case A were found in the white matter of the cerebrum with formation of sudanophilic breakdown products and with thick fibrillary gliosis. The pyramidal tract was completely degenerated. There was no accumulation of abnormal lipid in the brains of both cases.  相似文献   
39.
1. The effects of sarafotoxin S6c (S6c), a selective endothelin ETB receptor agonist, on renal haemodynamics and urine formation were examined in anaesthetized dogs. 2. Intrarenal arterial infusion of S6c at a rate of 1 or 5 ng/kg per min produced a transient increase in renal blood flow (RBF), with no change in systemic blood pressure and heart rate; RBF then decreased gradually to below the basal value. There were significant and dose-dependent increases in urine flow and free water clearance and decreases in urine osmolality during S6c infusion, whereas urinary excretion of sodium and glomerular filtration rate (GFR) remained unchanged. Simultaneously, S6c administration elicited a marked increase in urinary excretion of nitric oxide (NO) metabolites, N02? and N03? (UNO*V). 3. In dogs simultaneously administered S6c (5 ng/kg per min) and iVG-nitro-L-arginine (NOARG; 40 (jig/kg per min), a NO synthase inhibitor, the renal vasodilator effect of S6c was abolished and marked reductions in RBF and GFR were observed. The S6c-induced diuretic action was not affected by NOARG. In the presence of NOARG, there was a small amount of UNOxV at the basal level and the administration of S6c did not increase UNOxV. 4. These results suggest that an intrarenal arterial infusion of S6c enhances the production of NO in the kidney and that this enhancement contributes to the peptide-induced renal vasodilation. In contrast, it is unlikely that S6c-induced water diuresis is related to NO production stimulated by this peptide.  相似文献   
40.
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