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   36275篇
  免费   2212篇
  国内免费   110篇
耳鼻咽喉   321篇
儿科学   1184篇
妇产科学   1014篇
基础医学   4947篇
口腔科学   616篇
临床医学   5926篇
内科学   6596篇
皮肤病学   598篇
神经病学   3445篇
特种医学   606篇
外科学   3139篇
综合类   403篇
一般理论   55篇
预防医学   4527篇
眼科学   468篇
药学   2120篇
中国医学   68篇
肿瘤学   2564篇
  2023年   198篇
  2022年   384篇
  2021年   776篇
  2020年   461篇
  2019年   781篇
  2018年   899篇
  2017年   622篇
  2016年   650篇
  2015年   835篇
  2014年   1174篇
  2013年   1784篇
  2012年   2654篇
  2011年   2807篇
  2010年   1532篇
  2009年   1289篇
  2008年   2541篇
  2007年   2547篇
  2006年   2566篇
  2005年   2389篇
  2004年   2308篇
  2003年   2186篇
  2002年   2042篇
  2001年   221篇
  2000年   154篇
  1999年   301篇
  1998年   413篇
  1997年   367篇
  1996年   328篇
  1995年   282篇
  1994年   271篇
  1993年   253篇
  1992年   171篇
  1991年   138篇
  1990年   133篇
  1989年   130篇
  1988年   106篇
  1987年   114篇
  1986年   90篇
  1985年   108篇
  1984年   155篇
  1983年   157篇
  1982年   194篇
  1981年   167篇
  1980年   159篇
  1979年   93篇
  1978年   74篇
  1977年   81篇
  1976年   60篇
  1975年   53篇
  1974年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The stimulation of human γδ T cells by mycobacteria occurs through recognition of four distinct nonpeptide phosphorylated antigens termed TUBag1–4. Among these latter, TUBag4 has already been biochemically characterized as a γ-X derivative of 5′-deoxythymidine triphosphate (Constant, P., Davodeau, F., Peyrat, M. A., Poquet, Y., Puzo, G., Bonneville, M. and Fournié, J.-J., Science 1994. 264: 267). However, despite chemical synthesis of weakly stimulatory nucleotide-containing analogs, these mycobacterial compounds remained the sole nucleotide-containing antigens actually isolated from natural sources. Here, we present the complete isolation of the TUBag3 antigen from Mycobacterium fortuitum and demonstrate that this nonpeptide molecule contains a 5′-UTP nucleotide moiety. On selected Vγ9/Vδ2 clones, T cell responses can be triggered with nanomolar concentrations of TUBag3. Like crude mycobacterial extracts, this purified nucleotide conjugate elicits a strong polyclonal response of γδ PBL from healthy donors. Furthermore, we present evidence that this compound is distinct from the recently synthesized γ-isopentenyl 5′-UTP, a nucleotide conjugate of isopentenyl pyrophosphate that was found to be stimulatory for human γδ T cells (Tanaka, Y., Morita, C. T., Tanaka, Y., Nieves, E., Brenner, M. B. and Bloom, B. R., Nature 1995. 375: 155). Since it appears that both mycobacterial nucleotide antigens are molecules structurally related to peculiar precursors of nucleic acid synthesis, we propose that TUBag-reactive T cells might be specifically devoted to surveillance of proliferating cells.  相似文献   
82.
The parents of 14 individuals with severe/profound mental disabilities were interviewed one and three years after their children graduated or aged out of high school. Two categories of information were sought concerning the adult adjustment of these individuals. General status variables included marital status, place of residence, agencies contacted concerning employment opportunities, financial resources, leisure activities, means of transportation, sources of help in resolving problems, and amount of postsecondary training. Employment variables included location of employment, wages, number of hours worked per week, and job benefits received. Results indicated that three years after exiting high school, all participants were very dependent upon others for housing, transportation, and financial assistance. Ten of the 14 individuals were employed 3 years after exiting high school, all in sheltered workshops.  相似文献   
83.
We report an infant with multiple congenital anomalies, including craniosynostosis, tetralogy of Fallot variant, and limb anomalies associated with a maternal deletion of 15q15-22.1. Only two other patients have been reported with a similar deletion, but the deletion was paternal in both cases. We review our patient's findings and compare them to previously reported individuals with similar 15q abnormalities. Our patient allows an expansion of phenotype associated with mid-15q deletions to include severe craniosynostosis, congenital heart disease, and limb anomalies. This will assist in prenatal counseling and predicting postnatal outcome for other affected individuals. The specific breakpoints in our patient and the other patients with similar deletions may also assist in determining a critical region for suture formation.  相似文献   
84.
The use of 2 monoclonal antibodies during double immunohistochemistry would enable the use of a greater variety of antibody combinations. Here, we demonstrate a simple, cost effective method of double indirect immunostaining of cultured cells using primary antibodies from the same species. This method uses microwaving of cell samples immediately after the application of the first secondary antibody, and significantly reduces the level of nonspecific staining. This technique does not elute the antibodies, nor raise the sample temperature above 37 degrees C.  相似文献   
85.
The relationship between chronic lymphocytic thyroiditis (CLT) and papillary thyroid carcinoma (PTC) is a subject of controversy. Some investigators suggest a causal relationship, whereas others regard the two as only a coincidental occurrence. An additional complicating factor is the presence of atypical nuclei frequently found within lymphoid infiltrates in CLT, which resemble those in PTC. The finding of the RET-PTC translocations in CLT has been reported by two independent groups of investigators, suggesting that the areas of nuclear atypia in CLT are neoplastic rather than reactive. In the present study, we report additional molecular findings that support the hypothesis that the atypical nuclear changes in CLT may be preneoplastic or neoplastic. We microdissected small areas with atypical nuclei in glands with CLT and observed loss-of-heterozygosity mutations of tumor suppressor genes. These genetic mutations are evidence of clonal preneoplastic or neoplastic changes in the follicular cells of CLT. The clinical malignant potential of these minute foci is likely to be very small but remains to be determined.  相似文献   
86.
Partial trisomy 22: A recognizable syndrome   总被引:3,自引:0,他引:3  
A patient identified as being a partial trisomy 22 mosaic is presented. The presence of a translocation t(4;22) (pter;q12) is noted in the mother, sister and maternal aunt. Comparison is made with nine other reported cases of partial trisomy 22 confirmed by parental translocation. These suggest a definite syndrome, including mental retardation, congenital heart disease, skeletal anomalies, anti-mongoloid slant of the palpebral fissures, preauricular skin tags and low-set ears.  相似文献   
87.
The immune response after streptococcal infections of the skin and of the joints was studied in an experimental animal model. Hamsters were challenged intradermally or intra-articularly with different streptococcal serotypes, and antibodies for streptolysin O (ASO), deoxyribonuclease B (anti-deoxyribonuclease B), and group A carbohydrate (anti-group A CHO) were determined. After a single injection at either site, 7 of 48 animals (14%) developed group A-CHO antibodies; however, none of the animals developed detectable levels of ASO or anti-deoxyribonuclease B. After repeated infections of the skin or joint, anti-deoxyribonuclease B antibodies were detectable in 13% (4 of 30) and 30% (5 of 17) of the animals, respectively. Elevations of ASO occurred after repeated joint infections in 4 of 16 animals (25%), whereas none of 30 hamsters repeatedly infected intradermally developed antibodies against streptolysin O. For all three antibodies tested, elevated levels were more frequently noted after repeated joint infections than after repeated skin infections with the same streptococcal serotype. These data, similar to ones previously noted in human impetigo, indicate that ASO responses are feeble after streptococcal skin infections and that the site of infection per se, rather than the infecting strain, appears to be responsible for this poor response.  相似文献   
88.
1. 2,4-dinitrophenol, 2,4-dinitrophenetole, 2,4-dinitronaphthol, 4,6-dinitro-o-cresol, and to a lesser extent picric acid, produced an increase in bile flow and a rise in body temperature in the anaesthetized dog. The total biliary bromsulphalein (BSP) excretion in unit time was either slightly reduced, increased or remained at its pre-injection level.2. Picramic acid, the nitrochlorophenols and 2,4-dinitrobenzaldehyde caused a moderate increase in bile flow without an effect on the temperature of the animal.3. The three mononitrophenols, the five remaining isomeric dinitrophenols, isopicramic acid, the aminonitrophenols, phenol, 2,4-dinitroanisole, 2,4-dinitrobenzoic acid, 2,4-dinitrobenzene sulphonic acid, 2,4-dinitroresorcinol and 4-nitracatechol had little effect on bile secretion or body temperature.4. It thus appears that, in order for a compound of this type to have a pronounced effect on bile secretion, it is necessary to have nitro groups in positions 2 and 4 of the benzene ring, and a free or potential hydroxyl group.  相似文献   
89.
A 22-year-old man with previous radiation treatment for childhood astrocytoma underwent resection of a right parietooccipital lesion. Histopathology revealed a malignant neoplasm with areas of astrocytic and primitive neuroectodermal components. To resolve the relationship and cellular origin, representative tissue was microdissected from several targets, obtaining a balanced mixture of each element. Nonneoplastic brain parenchyma was separately microdissected to determine polymorphic marker informativeness and to serve as an internal negative control. Despite the relatively small quantity of tissue removed for each microdissection target, sufficient material was available for reliable, balanced, polymerase chain reaction-format genotyping encompassing a panel of tumor suppressor genes and genetic loci associated with these forms of neoplasia. The findings revealed distinct discordant genotypic profiles for each of the neoplastic components. The efficacy of the approach used for molecular analysis of this complex neoplasm and the implication of the genotypic findings are discussed.  相似文献   
90.
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