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   4747篇
  免费   309篇
  国内免费   35篇
耳鼻咽喉   82篇
儿科学   114篇
妇产科学   45篇
基础医学   567篇
口腔科学   121篇
临床医学   389篇
内科学   1340篇
皮肤病学   31篇
神经病学   322篇
特种医学   199篇
外科学   809篇
综合类   23篇
一般理论   1篇
预防医学   123篇
眼科学   154篇
药学   247篇
中国医学   3篇
肿瘤学   521篇
  2024年   11篇
  2023年   99篇
  2022年   177篇
  2021年   314篇
  2020年   152篇
  2019年   167篇
  2018年   191篇
  2017年   144篇
  2016年   178篇
  2015年   156篇
  2014年   174篇
  2013年   239篇
  2012年   369篇
  2011年   418篇
  2010年   201篇
  2009年   138篇
  2008年   236篇
  2007年   243篇
  2006年   203篇
  2005年   198篇
  2004年   169篇
  2003年   170篇
  2002年   160篇
  2001年   23篇
  2000年   31篇
  1999年   36篇
  1998年   32篇
  1997年   26篇
  1996年   26篇
  1995年   29篇
  1994年   30篇
  1993年   19篇
  1992年   36篇
  1991年   24篇
  1990年   26篇
  1989年   29篇
  1988年   17篇
  1987年   18篇
  1986年   21篇
  1985年   14篇
  1984年   16篇
  1983年   15篇
  1982年   11篇
  1981年   10篇
  1980年   10篇
  1978年   7篇
  1977年   6篇
  1976年   11篇
  1975年   12篇
  1974年   16篇
排序方式: 共有5091条查询结果,搜索用时 13 毫秒
201.
A 43-year-old woman was diagnosed as having stage IV follicular lymphoma. Phenotypically, the lymphoma cells were CD5(-), CD10(+), CD19(+), CD20(+), CD23(-), HLA-DR(+), and IgM-lambda(+). Conventional chromosomal analysis showed a three-way t(3;14;18)(q27;q32;q21) in the lymphoma cells, which was confirmed by spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). Immunohistochemistry revealed that both BCL2 and BCL6 proteins were expressed in the lymphoma cells, whereas only the BCL6 gene, and not the BCL2 gene, was rearranged by Southern blotting. The patient received combination chemotherapy and has been well for 3 years. This is the first reported case showing a three-way translocation involving 2 major lymphoma-specific abnormalities, 3q27 and t(14;18)(q32;q21).  相似文献   
202.
Turtles have a body plan unique among vertebrates in that their ribs have shifted topographically to a superficial layer of the body and the trunk muscles are greatly reduced. Identifying the developmental factors that cause this pattern would further our understanding of the evolutionary origin of the turtles. As the first step in addressing this question, we replaced newly developed epithelial somites of the chicken at the thoracic level with those of the Chinese soft-shelled turtle Pelodiscus sinensis (P. sinensis somites into a chicken host) and observed the developmental patterning of the grafted somites in the chimera. The P. sinensis somites differentiated normally in the chicken embryonic environment into sclerotomes and dermomyotomes, and the myotomes differentiated further into the epaxial and hypaxial muscles with histological morphology similar to that of normal P. sinensis embryos and not to that of the chicken. Epaxial dermis also arose from the graft. Skeletal components, however, did not differentiate from the P. sinensis sclerotome, except for small fragments of cartilage associated with the host centrum and neural arches. We conclude that chicken and P. sinensis share the developmental programs necessary for the early differentiation of somites and that turtle-specific traits in muscle patterning arise mainly through a cell-autonomous developmental process in the somites per se. However, the mechanism for turtle-specific cartilage patterning, including that of the ribs, is not supported by the chicken embryonic environment.  相似文献   
203.
Several multiple, large-scale, genetic studies on autoimmune-disease-associated SNPs have been reported recently: peptidylarginine deiminase type 4 (PADI4) in rheumatoid arthritis (RA); solute carrier family 22 members 4 and 5 (SLC22A4 and 5) in RA and Crohns disease (CD); programmed cell death 1 (PDCD1) in systemic lupus erythematosus (SLE), type 1 diabetes mellitus (T1D), and RA; and protein tyrosine phosphatase nonreceptor type 22 (PTPN22) in T1D, RA, and SLE. Because these reports on association were not always evaluated in multiple ethnic groups and because ethnic difference in allele frequency of the variants has been also reported, we investigated allele frequencies of nine SNPs in four autoimmune-disease-associated loci in Caucasian, African-descent, and Japanese populations. Although SNPs in PADI4 had similar allele frequency among three groups [maximal difference 11%; (P >0.05)], the other three loci revealed statistically significant allele frequency differences (maximal difference 39% (P <0.00001), 13% (P <0.00001), and 8% (P <0.00001) in SLC22A4, PDCD1, and PTPN22, respectively). Of note, three SNPs in the three loci that had allele frequency more than 8% in the Caucasian population were either not polymorphic at all or extremely rare in the Japanese population. Our data suggest that ethnic variations of polymorphisms should be evaluated in detail, and differences should be incorporated into investigations of susceptibility variants for common diseases.  相似文献   
204.
Hepatocytes in vivo have a potential for liver regeneration, but it has been very difficult to reconstruct hepatic organoids in vitro. Recent studies have shown that small hepatocytes (SHs) can reconstruct hepatic organoids including functional bile canaliculi (BC). In the present study we analyzed the movement of BC formed in the hepatic organoids, focusing on the coordination of contraction and dilation among cells and the mechanism producing the coordination. Hepatic cells, including SHs, were isolated from an adult rat liver and cultured. Time-lapse images of BC movements were taken and analyzed in cells treated with or without cytochalasin B (CB). Time-lapse images revealed that all BC, regardless of region contracted in a coordinated manner. Actin filaments were observed along the BC even after the BC networks treated with CB dilated markedly. Microinjection of dye was also carried out to investigate the flow thorough BC. Secreted fluorescein from the injected cell flowed along BC, and gap junctional protein connexin 32 was expressed along BC networks, suggesting cell-to-cell communication. Thus, groups of hepatocytes in the hepatic organoids act in a coordinated manner through intercellular communication.  相似文献   
205.
Immunoglobulin G (IgG) antibodies to Epstein-Barr virus (EBV) nuclear antigens 2 and 1 (EBNA-2 and EBNA-1, respectively) were studied using sera from healthy individuals of a population with a high incidence of asymptomatic primary EBV infections during infancy or childhood in Japan. Two CHO-K1 cell lines expressing EBNA-2 and EBNA-1 were used for anticomplement and indirect immunofluorescence assays. The positivity rate for EBNA-2 IgG rose in the 1- to 2-year age group, increased and remained at a plateau ( approximately 45%) between 3 and 29 years of age (3- to 4-, 5- to 9-, 10- to 14-, and 15- to 29-year age groups), and then reached 98% by age 40 (>/== 40-year age group). Both seropositivity for EBNA-1 and seropositivity for EBNAs in Raji cells (EBNA/Raji) were detected in the 1- to 2-year age group, remained high, and finally reached 100% by age 40. The geometric mean titer (GMT) of EBNA-2 IgG reached a plateau in the 5- to 9- and 10- to 14-year-old groups and remained elevated in the older age groups (15 to 29 and >/== 40 years). The GMT of EBNA-1 IgGs increased to a plateau in the 1- to 2-year-old group and remained unchanged in the older age groups. The GMT of EBNA/Raji IgGs also reached a plateau in the 1- to 2-year-old group, remained level throughout the 3- to 14-year age groups, and decreased in the 15- to 29-year-olds. EBNA-2 IgGs emerged earlier than EBNA-1 IgGs in 8 of 10 patients with infectious mononucleosis, who were between 1 and 27 years old, and declined with time in three of eight cases. These results suggest that EBNA-2 IgG antibodies evoked in young children by asymptomatic primary EBV infections remain elevated throughout life, probably because of reactivation of latent and/or exogenous EBV superinfection.  相似文献   
206.
A deficiency of citrin, which is encoded by the SLC25A13 gene, causes both adult-onset type II citrullinemia (CTLN2) and neonatal intrahepatic cholestasis (NICCD). We analyzed 16 patients with NICCD to clarify the clinical features of the disease. Severe intrahepatic cholestasis with fatty liver was the most common symptom, but the accompanying clinical features were variable, namely; suspected cases of neonatal hepatitis or biliary atresia, positive results from newborn screening, tyrosinemia, failure to thrive, hemolytic anemia, bleeding tendencies and ketotic hypoglycemia. Laboratory data showed elevated serum bile acid levels, hypoproteinemia, low levels of vitamin K-dependent coagulation factors, and hypergalactosemia. Hypercitrullinemia was detected in 11 out of 15 patients examined. Most of the patients were given a lactose-free and/or medium chain triglycerides-enriched formula and lipid-soluble vitamins. The prognosis of the 16 patients is going fairy well at present, but we should observe these patients carefully to see if they manifest any symptom of CTLN2 in the future.  相似文献   
207.
Magnetic carriers with efficient loading, delivery, and release of drugs are required for magnetically guided drug delivery system (DDS) as the potential cancer therapy. The present article describes the fabrication of porous FePt capsules approximately 340 nm in diameter with large pores of 20 nm in an ultrathin shell of 10 nm and demonstrates their application to a magnetically guided DDS in vitro. An aqueous anti-cancer drug is easily introduced in the hollow space of the capsules without external stimuli and released to cancer cells on cue through the magnetic shell composed of an ordered-alloy FePt network structure, which exhibits superparamagnetic features at approximately body temperature. The drug-loaded magnetic capsules coated with a lipid membrane are efficiently guided to the cancer cells within 15 min using a NdFeB magnet (0.2 T), and more than 70% of the cancer cells are destroyed.  相似文献   
208.
209.
To assess whether adiponectin gene (ADIPOQ) polymorphism is associated with intrauterine fetal growth and cord blood adiponectin, we investigated eight single-nucleotide polymorphisms (SNPs; rs182052, rs710445, rs16861205, rs12495941, rs1501299, rs3774261, rs2082940 and rs266729) in ADIPOQ and birth weight and cord blood adiponectin in 526 healthy neonates. We found that the neonates carrying the G allele of rs266729 had a significantly greater birth weight s.d. score than those homozygous for the C allele (CC: -0.06±0.75 versus CG: 0.20±0.64 versus GG: 0.07±0.78; P=1.65 × 10(-3), adjusted P=9.90 × 10(-3)). However, this difference was not significant after adjustment for cord blood adiponectin (P=0.04, adjusted P=0.26). The rs266729 SNP was strongly associated with cord blood adiponectin; neonates with rs266729 GG had the highest adiponectin (CC: 34.1±20.2 versus CG: 44.3±26.1 versus GG: 54.1±36.7?μg?ml(-1), P=2.80 × 10(-9), adjusted P=1.68 × 10(-8)). This association remained after adjustment for birth weight s.d. score (P=6.63 × 10(-8), adjusted P=3.98 × 10(-7)). Our results suggest that the influence of the rs266729 SNP in ADIPOQ on birth weight may be dependent on circulating adiponectin.  相似文献   
210.
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