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   27341篇
  免费   2006篇
  国内免费   84篇
耳鼻咽喉   351篇
儿科学   795篇
妇产科学   547篇
基础医学   3527篇
口腔科学   354篇
临床医学   2665篇
内科学   6003篇
皮肤病学   405篇
神经病学   2576篇
特种医学   1146篇
外科学   4775篇
综合类   277篇
现状与发展   1篇
一般理论   51篇
预防医学   2006篇
眼科学   412篇
药学   1336篇
中国医学   37篇
肿瘤学   2167篇
  2023年   308篇
  2022年   544篇
  2021年   1272篇
  2020年   675篇
  2019年   983篇
  2018年   1183篇
  2017年   816篇
  2016年   788篇
  2015年   958篇
  2014年   1314篇
  2013年   1587篇
  2012年   2346篇
  2011年   2284篇
  2010年   1240篇
  2009年   976篇
  2008年   1511篇
  2007年   1588篇
  2006年   1383篇
  2005年   1259篇
  2004年   1075篇
  2003年   906篇
  2002年   772篇
  2001年   183篇
  2000年   154篇
  1999年   180篇
  1998年   161篇
  1997年   134篇
  1996年   143篇
  1995年   115篇
  1994年   84篇
  1993年   89篇
  1992年   120篇
  1991年   120篇
  1990年   117篇
  1989年   126篇
  1988年   103篇
  1987年   108篇
  1986年   97篇
  1985年   98篇
  1984年   107篇
  1983年   88篇
  1982年   102篇
  1981年   80篇
  1980年   69篇
  1979年   86篇
  1978年   87篇
  1977年   49篇
  1975年   44篇
  1974年   46篇
  1973年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
ABSTRACT

A study was conducted to evaluate mucoadhesive property and immunomodulatory effect of phytogenic gums from Boswellia frereana, Boswellia carteri andCommiphora myrrha on intranasal Peste des petits ruminants (PPR) vaccination in goats and sheep in an ex-vivo and in-vivo situations. Plant gums were purified, dried and compressed into 500gm tablets. Modified shear stress measurement technique was used on freshly excised trachea and intestine tissues of goat to measure peak adhesion time. Forty eight animals (24 goats and 24 sheep) were divided into eight groups (of 3 goats and 3 sheep) and immunized intranasally with gum-vaccine combinations in two ratios (1:1, 1:2). Antibody against PPR virus was measured on day 14, 28, 42 and 56 post vaccination using H-based PPR bELISA. The peak adhesion time of the different gums was transient. PPR virus antibodies were detected in all immunized goats and sheep but not in unvaccinated control. The best percentage inhibition was recorded for Boswellia carteri-vaccine combination group at a ratio of 1:1. Administration of Boswellia carteri-PPR vaccine combination through intranasal or subcutaneous route, elicited similar antibody titre, implying that the intranasal route may be used as a non-invasive alternative delivery in PPR vaccination of small ruminants.  相似文献   
83.
The Texas Department of Criminal Justice (TDCJ) houses many subjects with acquired immunodeficiency syndrome (AIDS) who receive medical care in a comprehensive AIDS treatment center. In this case-control autopsy survey, we compared pathological outcomes of TDCJ inmates treated at the center (n = 155) with nonincarcerated patients who died during the same period (n = 155). Using multiple regression analysis and a proportional hazards model, survival time in the prisoners was equivalent to that in the controls. With few exceptions, the prevalences of opportunistic viral, fungal, protozoal, and bacterial infections contributing to mortality were equivalent between groups. Mycobacterium tuberculosis was isolated more frequently in the inmates, and M avium intracellulare was isolated less frequently (P < .0001). The inmates had a higher prevalence of bacterial infection of the central nervous system (CNS) (9.1% v 1.4%; P < .006); half of all CNS bacterial infections were caused by M tuberculosis. Inmates had significantly lower prevalences of vacuolar myelopathy (P < .006) and severe wasting disease (P < .0009). We conclude that survival of prison inmates with AIDS treated in a comprehensive AIDS treatment center was equivalent to that of nonincarcerated subjects with AIDS. Prevalences of certain complications of AIDS differed in the inmates, showing that the prison environment influenced some of the underlying causes of AIDS morbidity and mortality.  相似文献   
84.
In light of evidence of linkage of obesity to chromosome 2q31-q37, we hypothesized that the calpain-10 gene 'high-risk' haplotype combination for non-insulin-dependent diabetes mellitus (NIDDM) is involved in early onset obesity. We screened the NIDDM 'high-risk'-haplotype combination formed by the alleles 112 and 121 of the polymorphisms UCSNP-43, -19, and -63 in 166 families consisting of an extremely obese child or adolescent (mean BMI percentile: 99.3+/-1.38), one or more obese sibs (mean BMI percentile: 97.42+/-2.88), and both of their parents. Genotyping for three calpain-10 gene polymorphisms was performed by polymerase chain reaction (PCR) with (a) length polymorphism detection (UCSNP-19) or (b) allele-specific PCR (UCSNP-43 and -63). To allow for correct haplotype assignment all individuals were additionally genotyped for two microsatellite markers (D2S125 and D2S2338). We followed a hierarchical test procedure. As the first step, model-free linkage analysis was performed using maximum likelihood binomial statistics. The second stage consisted of a one-sided asymptotic pedigree disequilibrium test for the UCSNP-43 and on an exploratory level for the other SNP-markers and all haplotypes formed by the three SNPs. The final stage investigated the reported haplotype combination. We failed to detect an initial linkage of obesity to this region (LOD score <0.4). All subsequent exploratory analyses were negative. Our analysis of the relationship between the NIDDM 'high-risk' haplotype combination and extreme early onset obesity revealed no evidence for linkage and association.  相似文献   
85.
African Americans appear less likely than caucasians to undergo surgery for gastroesophageal reflux disease (GERD). When they do, they appear to have higher conversion and complication rates. Nevertheless, satisfaction with surgery is similar to caucasians. BACKGROUND: There is little information comparing the prevalence and treatment of GERD in various ethnic populations. The purpose of this study was to examine the variations in outcomes between caucasians and African Americans undergoing antireflux surgery. METHODS: The records of all patients who underwent antireflux surgery for GERD or paraesophageal hernia by a single surgeon from January 1997 through December 2001 were reviewed for preoperative and postoperative symptoms, complications, and postoperative satisfaction with surgery. RESULTS: Of the 204 procedures performed, 198 patients were either African American (24) or caucasian (174). Of the 18 African Americans undergoing laparoscopic antireflux surgery (LARS), five were converted to open and four had grade-1 or -2 complications. Of the 160 caucasians undergoing LARS, 27 were converted, and 17 had grade-1, -2, or -3 complications. African-American females had a heavier weight (222 lbs. versus 175 lbs., p<0.05) and conversion rate (55% versus 18%, p<0.05), compared to caucasian females. Satisfaction rates for African Americans were 88%, compared to 82% for caucasians. CONCLUSION: This study demonstrated significant differences between conversion rates in African Americans and caucasians with respects to frequency of surgery for GERD and conversion rates for LARS. Nevertheless, African Americans appear more satisfied with their surgical outcome. Further research is needed to determine whether African Americans truly have a lower incidence of GERD or if bias exists in referral patterns or cultural attitudes.  相似文献   
86.
Linkage disequilibrium patterns of the human genome across populations   总被引:7,自引:0,他引:7  
We studied the patterns of linkage disequilibrium (LD) in the human genome among three populations: African Americans, Caucasians and Ashkenazi Jews. These three populations represent admixed, outbred and isolated populations, respectively. The study examined defined chromosomal regions across the whole genome. We found that SNP allele frequencies are highly correlated between Ashkenazi Jews and Caucasians and somewhat distinct in African Americans. In addition, Ashkenazi Jews have a modest increase in LD compared with Caucasians, and both have greater LD than African Americans. The three populations differed more significantly with regard to haplotype heterogeneity. We found, as expected, that Ashkenazi Jews display the greatest extent of homogeneity and African Americans the greatest extent of heterogeneity. We found that most of the variance in LD can be attributed to the difference between regions and markers rather than to that between different population types. The average recombination rates estimated by low-resolution genetic maps can only explain a small fraction of the variance between regions. We found that LD (in terms of r(2)) decreases as a function of distance even within the so-called 'haplotype blocks'. This has significant consequences when using LD mapping for the genetic dissection of complex traits, as higher density SNP maps will be required to scan the genome.  相似文献   
87.
Using tumor necrosis factor receptor type 2 (TNFR2)-deficient mice and generating bone marrow chimeras which express TNFR2 on either hematopoietic or nonhematopoietic cells, we demonstrated the requirement for TNFR2 expression on tissue cells to induce lethal cerebral malaria. Thus, TNFR2 on the brain vasculature mediates tumor necrosis factor-induced neurovascular lesions in experimental cerebral malaria.  相似文献   
88.
89.
We have previously shown that intranasal infection of mice with mouse hepatitis virus (MHV) strain UAB (MHV-UAB) increases their resistance to Salmonella typhimurium injected intravenously 6 days later. To study how salmonella resistance was induced, BALB/cAnNCr mice were infected with salmonella strains carrying specific genetic alterations. One set of studies compared the effect of MHV infection on subsequent salmonella infections with AroA- (avirulent) and Aro+ (virulent) salmonellae. Unlike its effect on Aro+ salmonellae, MHV failed to reduce the number of AroA- salmonellae recovered from mice. Because AroA- S. typhimurium shows almost no growth in vivo, this failure indicated that the effect of MHV on salmonella resistance required growth of the infecting salmonellae. In other studies, the effect of MHV infection on both growth and killing were monitored simultaneously in mice with growing salmonellae carrying a single copy of the temperature-sensitive pHSG422 plasmid, which is unable to replicate in vivo. MHV infection reduced salmonella growth but caused no increase in salmonella killing. MHV infection of mice given wild-type salmonellae also resulted in no increase in salmonella killing 4 h after salmonella challenge. These studies demonstrate that MHV-UAB infection increases host resistance to salmonellae by enhancing suppression of bacterial growth instead of by increasing the amount of salmonella killing.  相似文献   
90.
Structural abnormalities are found in the astrocytes of the dentate nuclei of animals after portacaval shunting (PCS). These changes are also found in man in association with portal-systemic encephalopathy. To investigate the relationship between portal-systemic shunting and hepatocellular dysfunction in the pathogenesis of these changes, PCS and protacaval transposition (PCT) were performed in rats. PCT diverts portal blood into the systemic circulation, but retains normal total hepatic blood flow by perfusion with systemic venous blood. Liver function and mass are better preserved than after PCS. Abnormal glial cells were found in 4.03% of animals following sham operation, 13.45% following PCT, and 19.09% following PCS. Both experimental groups differed significantly from control animals, and the number of abnormal cells was significantly higher after PCS than after PCT. These findings are in keeping with the hypothesis that hepatocellular dysfunction plays an important role in addition to portal-systemic shunting in the aetiology of the structural changes in the brain associated with hepatic encephalopathy.  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