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   3563篇
  免费   181篇
  国内免费   14篇
耳鼻咽喉   26篇
儿科学   41篇
妇产科学   89篇
基础医学   596篇
口腔科学   122篇
临床医学   271篇
内科学   778篇
皮肤病学   49篇
神经病学   231篇
特种医学   123篇
外科学   490篇
综合类   22篇
一般理论   1篇
预防医学   208篇
眼科学   52篇
药学   293篇
中国医学   15篇
肿瘤学   351篇
  2023年   14篇
  2022年   39篇
  2021年   69篇
  2020年   47篇
  2019年   63篇
  2018年   95篇
  2017年   55篇
  2016年   70篇
  2015年   79篇
  2014年   102篇
  2013年   143篇
  2012年   199篇
  2011年   176篇
  2010年   135篇
  2009年   93篇
  2008年   180篇
  2007年   194篇
  2006年   218篇
  2005年   155篇
  2004年   163篇
  2003年   146篇
  2002年   138篇
  2001年   100篇
  2000年   124篇
  1999年   106篇
  1998年   39篇
  1997年   42篇
  1996年   27篇
  1995年   18篇
  1994年   22篇
  1993年   16篇
  1992年   65篇
  1991年   59篇
  1990年   63篇
  1989年   70篇
  1988年   62篇
  1987年   61篇
  1986年   41篇
  1985年   45篇
  1984年   24篇
  1983年   16篇
  1982年   14篇
  1980年   13篇
  1979年   21篇
  1978年   12篇
  1977年   20篇
  1976年   10篇
  1975年   8篇
  1974年   21篇
  1967年   10篇
排序方式: 共有3758条查询结果,搜索用时 15 毫秒
41.
Previously, we identified the glycoprotein gO gene, UL74, as a hypervariable locus in the human cytomegalovirus (HCMV) genome [Virology 293 (2002) 281]. Here, we analyze gO from 50 isolates from congenitally infected newborns, transplant recipients, and HIV/AIDS patients from Italy, Australia, and UK. These are compared to four gO groups described from USA transplantation patients [J. Virol. 76 (2002) 10841]. Phylogenetic analyses identified seven genotypes. Divergence between genotypes was up to 55% and within 3%. Discrete linkage was shown between seven hypervariable gO and gN genotypes, but not with gB. This suggests interactions, while gN and gO are known to form complexes with distinct conserved glycoproteins gM, gH/gL, respectively, both are involved in fusogenic entry and exit. Codon-based maximum likelihood models showed evidence for sites of positive selection. Further analyses of disease relationships should take into account these newly defined gO/gN groups.  相似文献   
42.
Sotrel A  Dal Canto MC 《Human pathology》2000,31(10):1274-1298
Acquired immune deficiency syndrome (AIDS), caused by human immunodeficiency virus type 1 (HIV-1), has claimed more than 10 million lives over the past 15 years. There are approximately 30 million HIV-positive people worldwide, 89% of whom reside in sub-Saharan Africa and Asia. The intricate relationship between the virus and HIV-related human multisystem pathology prompted scientists to modify many previously established concepts about infectious diseases and immunology, and to test new ones. The results of this work helped resolve many, albeit not all, long-standing problems concerning HIV-1 immune escape, its cellular tropism, and pathogenesis of HIV-related immunosuppression and nervous system disease. The most impressive advances have been made in antiretroviral drug treatment of HIV infection, which has resulted in dramatically reducing AIDS-related mortality, morbidity, and perinatal transmission. However, considering the magnitude of the worldwide HIV-AIDS pandemic, prohibitive cost and unusually exacting nature of combination drug treatment, as well as the emergence of drug-resistant HIV mutants, the disease and virus remain formidable and unpredictable, particularly in the area of prevention and vaccine development. Here, we have reviewed the most pertinent recently published studies of various aspects of HIV/AIDS intended to answer the following questions: what have we learned and what remains to be determined regarding this unorthodox viral disorder?  相似文献   
43.
Dal Pra I  Freddi G  Minic J  Chiarini A  Armato U 《Biomaterials》2005,26(14):1987-1999
Biologically tolerated biomaterials are the focus of intense research. In this work, we examined the biocompatibility of three-dimensional (3D) nonwovens of sericin-deprived, Bombyx mori silk fibroin (SF) in beta-sheet form implanted into the subcutaneous tissue of C57BL6 mice, using sham-operated mice as controls. Both groups of mice similarly healed with no residual problem. Macroarray analysis showed that an early (day 3) transient expression of macrophage migration inhibitory factor (MIF) mRNA, but not of the mRNAs encoding for 22 additional proinflammatory cytokines, occurred solely at SF-grafted places, where no remarkable infiltration of macrophages or lymphocytes subsequently happened. Even an enduring moderate increase in total cytokeratins without epidermal hyperkeratosis and a transient (days 10-15) upsurge of vimentin occurred exclusively at SF-grafted sites, whose content of collagen type-I, after a delayed (day 15) rise, ultimately fell considerably under that proper of sham-operated places. By day 180, the interstices amid and surfaces of the SF chords, which had not been appreciably biodegraded, were crammed with a newly produced tissue histologically akin to a vascularized reticular connective tissue, while some macrophages but no lymphocytic infiltrates or fibrous capsules occurred in the adjoining tissues. Therefore, SF nonwovens may be excellent candidates for clinical applications since they both enjoy a long-lasting biocompatibility, inducing a quite mild foreign body response, but no fibrosis, and efficiently guide reticular connective tissue engineering.  相似文献   
44.
Hepatitis C virus core protein, in addition to being a component of the viral capsid, has a number of regulatory functions. Here we showed two bodies of evidence indicating that a fraction of the core protein species is a substrate of the ubiquitin (Ub)-proteasome pathway of targeted proteolysis. First, the core protein processing the C-terminal hydrophobic region is metabolically unstable, and incubation with a proteasome inhibitor led to a significant accumulation of the protein. Second, an in vivo ubiquitylation assay indicates conjugation of multi-Ub chain to the unstable core protein. In contrast, a stable form of core protein, p21, is also able to be ubiquitylated, but it links to a single or only a few Ub moiety. Therefore, processing event(s) at the C-terminal hydrophobic domain of HCV core protein may affect the ubiquitylation pathway, particularly the efficiency of the multi-Ub chain assembly, resulting in stable, matured core proteins.  相似文献   
45.
Linkage of epidemiological registries can provide cost-effective information on the associations between different diseases or exposures in the population under study and on completeness of surveillance system databases. We describe the program SALI (software for automated linkage in Italy) aimed at matching individual records from medium-sized registries (in the order of 100,000 records), where the desired outcome is to miss as few links as possible and, because of low link-likelihood (< 1%), a manual revision of matched pairs is feasible. SALI, developed in CA-Clipper language, uses registry files in dBase format. It requires only name, surname, and date of birth as key fields, and it allows for spelling errors in Italian or other Latin languages through a specific algorithm. Furthermore, a double-blind procedure ensures data confidentiality. The main linkage procedure is based on four stages, two automatic ones, and two where the operator can decide through specific windows whether to accept stage-selected matches. SALI takes into account possible errors in key fields thus reducing false negatives. It was used to solve the problem of linkage between AIDS and cancer registries in Italy. It can be used with every IBM-compatible computer system, assuring uniquely high portability.  相似文献   
46.
47.
In order to assess the suitability of cryopreserved neoplastic tissues for xenografting into nude (nu/nu) mice, we compared the take rate in 28 samples of pancreatic ductal carcinoma. Eleven fresh samples were implanted in nu/nu mice, and 17 were frozen in cryopreserving solution and implanted at a later time. All samples were examined for the presence of neoplastic tissue in cryostat sections. A total of 15 tumors grew in the animals; five from the freshly implanted samples and ten from those cryopreserved. Ten xenografted tumors were characterized for alterations in p53, K-ras, and p16 genes, which were found in six, eight, and nine cases, respectively. Our results demonstrate that the take rate for xenografting is comparable between cryopreserved and fresh tissue samples. The procedure allows for the exchange of tumor material between institutions and permits the establishment of centralized facilities for the storage of an array of different primary tumor samples suitable for the production of in vivo models of cancers.  相似文献   
48.
Occupational asthma caused by fish inhalation   总被引:1,自引:1,他引:1  
Occupational asthma (OA) due to fish inhalation, confirmed by specific bronchial challenge (SBC), has not been described as yet in medical literature, as far as we know. We describe two patients whose asthma was induced by occupational exposure to fish and confirmed by serial measurements of PEFR and SBC. Two fish-processing workers reported asthma symptoms related to their workplace. They were skin tested with fish extracts and their sera assayed for IgE antibodies to various fish species. Nonspecific bronchial reactivity was assessed by methacholine challenge. The occupational relationship was confirmed by PEFR monitoring in working and off-work periods. SBC with fish extracts was carried out to confirm the diagnosis of OA. Skin tests with raw and cooked plaice, salmon, hake, and tuna in patient 1 and anchovy, sardine, trout, salmon, Atlantic pomfret, and sole in patient 2 were positive. Specific IgE serum antibodies were found to salmon in patient 1 and to trout, anchovy, and salmon in patient 2. PEFR measurements differed significantly (P<0.001) between work and off-work periods for both patients. A bronchial challenge with methacholine was positive in patient 1. SBC with raw hake, salmon, plaice, and tuna extracts in patient 1 and raw salmon extract in patient 2 were all positive with an immediate response. SBC with Dermatophagoides pteronyssinus extract was entirely negative in both patients. In three asthmatic, non-fish-allergic controls, SBC with tuna, hake, salmon, and plaice were all negative. These results suggest that fish inhalation can elicit IgE-mediated occupational asthma.  相似文献   
49.
Recent studies of our newly developed synthetic collagen-like hexapeptide have shown that it enhances cultured cell adhesion and differentiation and improves the morphology of ex vivo skin. Consequently, we were interested in further investigating the effects of the collagen-like peptide on the skin. We performed different immunostaining studies on ex vivo human skin samples treated with the collagen-like peptide at 1% in time course studies. Our research also included comparative studies with vitamin C (often used as a positive control for enhancing collagen synthesis). The results showed that application of the collagen-like peptide to the skin enhanced synthesis of many extracellular matrix (ECM) molecules and that this effect was observed very early in some ECM molecules such as laminin 5, collagen 111, and collagen IV The expression of the other molecules was increased after different times of application of the collagen-like peptide. Interestingly, comparative studies with vitamin C showed that the synthesis response of some ECM molecules such as laminin 5, collagen 111 and collagen IV was more rapid after the administration of the collagen-like peptide than through vitamin C administration. Our results also revealed that after a longer treatment period, both active ingredients stimulated ECM molecule synthesis to a similar degree, with the exception of some molecules that remained superiorafterpeptide administration, such as collagen IV and beta 1 integrin. These histological studies demonstrate the remarkable and rapid effect of the collagen-like peptide on stimulating ECM molecule synthesis and suggest wide application for the peptide in antiaging and photoaging skin care products.  相似文献   
50.
Tumor cells from three uterine leiomyomas showing translocations involving 12q14-15 were transformed by transfection using the "early regions" of the SV40 genome. The cells had a higher proliferative capacity, were able to form colonies in soft agar, and showed an increased growth potential. Karyotype analyses of these transformed leiomyoma cells showed that the cells had retained the initial t(12;14) and t(12;15).  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