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   11085篇
  免费   560篇
  国内免费   46篇
耳鼻咽喉   185篇
儿科学   290篇
妇产科学   234篇
基础医学   1803篇
口腔科学   125篇
临床医学   817篇
内科学   1880篇
皮肤病学   274篇
神经病学   1356篇
特种医学   540篇
外国民族医学   9篇
外科学   1855篇
综合类   28篇
一般理论   3篇
预防医学   351篇
眼科学   323篇
药学   754篇
中国医学   21篇
肿瘤学   843篇
  2023年   58篇
  2022年   80篇
  2021年   172篇
  2020年   132篇
  2019年   181篇
  2018年   206篇
  2017年   168篇
  2016年   258篇
  2015年   281篇
  2014年   315篇
  2013年   424篇
  2012年   660篇
  2011年   653篇
  2010年   413篇
  2009年   357篇
  2008年   596篇
  2007年   622篇
  2006年   606篇
  2005年   616篇
  2004年   604篇
  2003年   568篇
  2002年   465篇
  2001年   293篇
  2000年   297篇
  1999年   237篇
  1998年   95篇
  1997年   64篇
  1996年   84篇
  1995年   63篇
  1994年   65篇
  1993年   64篇
  1992年   132篇
  1991年   144篇
  1990年   139篇
  1989年   125篇
  1988年   105篇
  1987年   78篇
  1986年   82篇
  1985年   102篇
  1984年   83篇
  1983年   72篇
  1982年   47篇
  1979年   60篇
  1977年   53篇
  1974年   43篇
  1973年   46篇
  1972年   43篇
  1971年   48篇
  1970年   39篇
  1967年   38篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Summary This study investigates the action of intravenous PGE1 on myocardial reperfusion injury and the possible involvement of antineutrophil activities. Cats were subjected to 3 h of temporary ligation of the left anterior descending coronary artery, followed by 2 h of reperfusion. Animals were treated with PGE1 (5 g/kg x min) or vehicle (saline solution), starting 0.5 h after coronary artery occlusion. Vehicle-treated cats exhibited a significant loss of cardiac creatine phosphokinase specific activity at 5 h, accompanied by a significant ischemia-induced rise in the ST segment of the ECG and development of a Q wave after starting reperfusion. All of these alterations were largely prevented by PGE1 treatment. PGE1 exerted some blood-pressurelowering activity at 5 h (P > 0.05) but did not reduce myocardial contractile force and oxygen consumption. PGE1 modestly antagonized ischemia-induced formation of platelet aggregates. However, PGE1 prevented the rise in peripheral white blood cell count during ischemia and reperfusion and inhibited the generation of reactive oxygen species (myeloperoxidase assay) from zymosan-stimulated whole blood ex vivo. The ratio of generation of reactive oxygen species/white blood count remained unchanged. It is concluded that PGE1 protects the ischemic myocardium from acute reperfusion injury and that this effect involves an action of the compound on neutrophils, probably by improved myocardial tissue preservation, resulting in reduced formation of chemotactic products and, consequently, less local neutrophil accumulation and release of noxious metabolites.Parts of these results have been presented to the 29th Spring meeting of the Deutsche Gesellschaft für Pharmakologie und Toxikologie, Mainz, 1988 Send offprint requests to K. Schrör at the above address  相似文献   
52.
The effectiveness of an H1 +H2-prophylaxis against perioperative acute pseudoallergic reactions in which histamine is involved, and against postoperative complications the incidence of which may be increased by these reactions, was the central problem of a randomized trial in 162 aged patients during elective conventional cholecystectomy. As main endpoint it was planned to use the systemic histamine release reaction, as it already had been defined for the conscious and anaesthetized human subject. However, it had to be reassessed and redefined for the intraoperative period after improvement of the plasma histamine assay and new findings about stress-induced histamine release and the kinetics of histamine release during certain phases of operation.Intraoperative release is, at present, defined solely as an increase of plasma histamine values after a particular action (phase of operation). It includes criteria concerning plasma histamine changes either in comparison to the base value before surgery or to the preceding value before the last surgical action. Histamine elevations must exceed the last value by more than 3 standard deviations of the analytical error (i.e. 200% if value <0.25 ng/ml=" and=" 40%=" above).=" basic=" requirements=" for=" the=" histamine=" assay=" (quality=" control),=" correct=" sample=" taking=" and=" appropriate=" preparation=" have=" to=" be=" fulfilled=" over=" the=" whole=" trial=" period.=" when=" these=" criteria=" were=" applied=" to=" the=" 162=" patients=" an=" overall=" incidence=" of=" histamine=" release=" during=" cholecystectomy=" of=" 55.6%=" was=" found=" with=" 9.7–20%=" during=" an=" individual=" phase=" of=" operation.=" the=" data=" of=" this=" study,=" performed=" under=" routine=" conditions,=" with=" a=" sufficient=" number=" of=" patients=" with=" elevated=" risk=" and=" event=" controlled=" plasma=" histamine=" values,=" lead=" to=" a=" better=" understanding=" of=" intraoperative=" histamine=" release,=" its=" incidence=" and=">  相似文献   
53.
Five diammine-Pt(II) or Pt(IV) coordination compounds, namely cis-diammine-dichloro-platinum (II) "cis-DDP", transdihydroxy-cis-diammine-dichloro-platinum (IV) "trans-ODDP", and derived substitution products of lactic acid (racemates or L-forms) with diminished toxicity in comparison to cis-DDP have been tested against mouse leukemia P388, and partly on melanoma B16 for antineoplastic activity. The results have been compared with those obtained with the clinical approved cis-DDP. They were not in every way equal to the antitumor efficiency of cis-DDP. Improved physicochemical properties as well as favorable differences of side effects in contrast to cis-DDP, could be decisive for the potential value of these substances.  相似文献   
54.
The present study addressed auditory processing in 8-11-year-old children with developmental dyslexia by means of event-related brain potentials (ERP). Cortical sound reception was evaluated by recording N250 responses to syllables and tones and cortical sound discrimination by analyzing the mismatch negativity (MMN) to syllable and tone changes. We found that both cortical sound reception and sound discrimination were impaired in dyslexic children. The analysis of the data obtained from two dyslexic subgroups, Dyslexics-1 being impaired in non-word reading (or both non-word and frequent word reading) and Dyslexics-2 in frequent word reading but not in non-word reading, revealed that the MMN was specifically diminished in the latter group whereas it was normal-like in Dyslexics-1. However, no differences were found between these subgroups in sound reception as indicated by the responses elicited by the standard stimuli. These results show that different diagnostic subgroups of dyslexics have different patterns of auditory processing deficits as suggested by similarly impaired sound reception in both dyslexic groups and the sound-discrimination impairment specific to one of the groups.  相似文献   
55.
CD97 expression is related closely to the dedifferentiation and tumor stage in thyroid carcinomas. We systematically examined the role of CD97 and its closest relative, EMR2, in normal and malignant gastric, esophageal, and pancreatic tissue. The normal tissues were EMR2-, whereas CD97 was expressed slightly in the parietal cells of gastric mucosa and in exocrine pancreatic cells. Interestingly, intralobular and interlobular pancreatic ducts were CD97+. All tumors were EMR2-. CD97 was expressed by 44 of 50 gastric, 14 of 18 pancreatic, and 10 of 13 esophageal carcinomas. Of the 44 gastric cancers, 27 showed disseminated or scattered tumor cells at the invasion front with stronger CD97 expression than tumor cells located in solid tumor formations. There was no correlation between CD97 levels in the tumors or soluble CD97 in the serum samples and the clinicopathologic features of the patients. Taken together, significant numbers of gastric, esophageal, and pancreatic carcinomas are CD97+, whereas its homolog, EMR2, does not have any role in such tumors.  相似文献   
56.
Thomas CL  Leh V  Lederer C  Maule AJ 《Virology》2003,306(1):33-41
All of the protein products of Turnip crinkle virus (TCV; Tombusviridae, Carmovirus) were tested for their ability to suppress RNA silencing of a reporter gene after transient expression in Agrobacterium-infiltrated Nicotiana benthamiana leaves. Only the capsid protein, P38, showed suppression activity, although this was not obvious when P38 was expressed as part of a TCV infection of the same tissues. When P38 was expressed from a PVX vector, symptoms with enhanced severity that correlated with increased PVX RNA accumulation were observed. This contradiction between ectopic expression of P38 and TCV infection could be accounted for if the active determinant of suppressor activity within P38 was sequestered within the capsid protein structure. The N-terminal 25 amino acids were shown to be important for this activity. This region forms part of the unexposed R-domain that interacts with the RNA within the virus particle. This observation throws light on some of the complex biology exhibited by TCV.  相似文献   
57.
58.
59.
We present a novel methodology to determine the phase of single-nucleotide polymorphisms (SNPs) on a chromosome, which we term clone-based systematic haplotyping (CSH). The CSH procedure is based on separating the allelic chromosomes of a diploid genome by fosmid/cosmid cloning, and subsequent SNP typing of 96 clone pools, each representing approximately 10% of the genome. The pools are screened by PCR for the sequence of interest, followed by SNP typing on the PCR products using the GOOD assay. We demonstrate that by CSH, the haplotype of SNPs separated by more than 50 kilobases can definitely be assigned. We propose this method as being suitable for constructing maps of ancestral haplotypes, analysis of complex diseases, and for diagnosis of rare defects in which the molecular haplotype is crucial. In addition, by amplifying the initial DNA by many orders of magnitude, the original DNA resource is effectively immortalized, enabling the haplotyping of hundreds of thousands of SNPs per individual.  相似文献   
60.
A method is described based on crossed immunoelectrophoresis of a complex antigen mixture in agarose gel followed by incubation of the gel with the monoclonal antibody. The bound monoclonal antibody is detected by the use of a secondary enzyme-labelled antibody.Using this technique we have been able to identify the precipitate arc in crossed immunoelectrophoresis of major histocompatibility complex (MHC) class I molecules in a mixture of all detergent solubilized cell membrane molecules by means of a monoclonal antibody, the specificity of which was known independently to be against MHC class I molecules. In other experiments using the same technique we demonstrated the reaction of a monoclonal antibody specific for chicken Ig light chains.  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