全文获取类型
收费全文 | 615篇 |
免费 | 38篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 31篇 |
妇产科学 | 17篇 |
基础医学 | 72篇 |
口腔科学 | 16篇 |
临床医学 | 67篇 |
内科学 | 99篇 |
皮肤病学 | 23篇 |
神经病学 | 8篇 |
特种医学 | 177篇 |
外科学 | 41篇 |
综合类 | 37篇 |
预防医学 | 12篇 |
眼科学 | 8篇 |
药学 | 19篇 |
中国医学 | 1篇 |
肿瘤学 | 27篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 14篇 |
2014年 | 7篇 |
2013年 | 16篇 |
2012年 | 13篇 |
2011年 | 18篇 |
2010年 | 24篇 |
2009年 | 16篇 |
2008年 | 24篇 |
2007年 | 17篇 |
2006年 | 23篇 |
2005年 | 26篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 20篇 |
1997年 | 39篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 5篇 |
排序方式: 共有657条查询结果,搜索用时 15 毫秒
11.
12.
Kliks S Contag CH Corliss H Learn G Rodrigo A Wara D Mullins JI Levy JA 《AIDS research and human retroviruses》2000,16(13):1223-1233
Our previous studies have indicated that HIV transmission from infected mothers to infants occurs with viruses showing rapid kinetics of replication, and either resistance to maternal neutralizing antibodies or sensitivity to enhancing antibodies. The genotypic patterns that result in these and other phenotypic viral characteristics may provide clues to the selection pressures exerted during this mode of transmission. For this reason, DNA sequences of the envelope gene (env) were determined for viral isolates obtained from seropositive women who were mothers of either infected or uninfected infants. Sequences of viruses isolated early in life from the infected newborns were also determined, such that diversity both within isolates and between maternal and infant isolates could be assessed. Among isolates obtained from mothers of uninfected infants, the V3 region of env demonstrated a higher degree of heterogeneity than those from mothers of infected infants. Similar to the viruses obtained from the mothers of infected infants, the infant-derived viral sequences were relatively homogeneous. Finally, the reactivity of maternal plasma with infant-derived HIV isolates, whether via neutralizing or enhancing antibodies, appeared to predict the distribution of viral sequences in the infant isolates. These data suggest that selective pressure on HIV-1 during transmission or growth in the infected infant may be mediated by biologic and/or immunologic processes. 相似文献
13.
Contractile proteins participate in release of erythroid growth regulators from mononuclear cells 总被引:1,自引:0,他引:1
We have investigated the role of contractile proteins of circulating mononuclear cells in generation of membrane-associated, erythroid growth regulatory molecules. Lymphocytes and monocytes were incubated under serum-free conditions without and with cytochalasin B, cytochalasin D, or colchicine, and effects on positive and negative erythropoietic activities were determined in cell membranes and in surface membrane vesicle-rich pellets and supernatants of dialyzed medium conditioned by the cells. In serum-free cultures of human bone marrow, plasma membranes and exfoliated membrane-derived vesicles from cytochalasin-treated lymphocytes lost their capacity to support the formation of erythroid bursts, while monocyte membrane-associated inhibitory activity was abolished by preincubation with cytochalasin. In contrast, membrane-associated activities of colchicine-treated cells were unaffected. Cytochalasin-induced alterations of membrane regulatory molecules were observed in a dose-dependent fashion over a wide range of concentrations (1 to 100 micrograms/mL) tested. However, the capacity of membrane vesicle-free supernatants of medium conditioned by lymphocytes or monocytes was unaffected by cytochalasins, regardless of drug concentration used. Lysates of cytochalasin B-treated cells inhibited the activity of deoxyribonuclease I to a greater degree than did lysates of untreated cells, suggesting that the relative amount of monomeric actin is increased in the cytoplasm of treated cells. Furthermore, results of experiments with D-glucose and with cytochalasin D suggest that cytochalasin effects are independent of alterations in glucose metabolism. The data indicate that expression of plasma membrane- associated regulators is sensitive to agents that block polymerization of actin. They raise the possibility that changes in distribution of actin between unpolymerized and filamentous pools may influence the organization and/or function of mononuclear cell surface-associated erythroid regulatory molecules. 相似文献
14.
Visualizing pneumococcal infections in the lungs of live mice using bioluminescent Streptococcus pneumoniae transformed with a novel gram-positive lux transposon 下载免费PDF全文
Francis KP Yu J Bellinger-Kawahara C Joh D Hawkinson MJ Xiao G Purchio TF Caparon MG Lipsitch M Contag PR 《Infection and immunity》2001,69(5):3350-3358
Animal studies with Streptococcus pneumoniae have provided valuable models for drug development. In order to monitor long-term pneumococcal infections noninvasively in living mice, a novel gram-positive lux transposon cassette, Tn4001 luxABCDE Km(r), that allows random integration of lux genes onto the bacterial chromosome was constructed. The cassette was designed so that the luxABCDE and kanamycin resistance genes were linked to form a single promoterless operon. Bioluminescence and kanamycin resistance only occur in a bacterial cell if this operon has transposed downstream of a promoter on the bacterium's chromosome. S. pneumoniae D39 was transformed with plasmid pAUL-A Tn4001 luxABCDE Km(r), and a number of highly bioluminescent colonies were recovered. Genomic DNA from the brightest D39 strain was used to transform a number of clinical S. pneumoniae isolates, and several of these strains were tested in animal models, including a pneumococcal lung infection model. Strong bioluminescent signals were seen in the lungs of the animals containing these pneumococci, allowing the course and antibiotic treatment of the infections to be readily monitored in real time in the living animals. Recovery of the bacteria from the animals showed that the bioluminescent signal corresponded to the number of CFU and that the lux construct was highly stable even after several days in vivo. We believe that this lux transposon will greatly expand the ability to evaluate drug efficacy against gram-positive bacteria in living animals using bioluminescence. 相似文献
15.
16.
Squamous cell carcinoma of the nail bed is a relatively uncommon tumour that may be diagnosed only after considerable delay. The first case presented is a 79-year-old man with a history of discomfort and discoloration affecting the right thumbnail of 3 years duration. The second case is a 70-year-old man who presented with a recurrent, offensive discharge from beneath the left thumbnail of 40 years duration. Clinical examination of the affected digits revealed minor nail abnormalities. The presence of tumour was fully apparent only after removal of the nail plate and inspection and biopsy of the nail bed. The cases demonstrate that subungual squamous cell carcinoma may present with prolonged symptoms and a deceptively benign appearance. The importance of consideration of the possibility of malignancy, removal of the nail plate for inspection of the nail bed and appropriate biopsy is emphasized. 相似文献
17.
Cytogenetic and histologic correlations in malignant lymphoma 总被引:9,自引:0,他引:9
Koduru PR; Filippa DA; Richardson ME; Jhanwar SC; Chaganti SR; Koziner B; Clarkson BD; Lieberman PH; Chaganti RS 《Blood》1987,69(1):97-102
Although a number of studies have indicated correlations between histologic subtypes of tumors and certain nonrandom chromosome changes, cytogenetic studies of lymphoma are in an early stage compared to those of leukemia. No comprehensive analysis of available data has so far been attempted in the literature either. Here we present an analysis of chromosome changes and their correlation with subtypes of lymphoma studied by conventional histology and cell surface markers, as observed in two sets of data: a group of 65 karyotypically abnormal tumors sequentially ascertained and studied by us during the period January 1, 1984 to April 30, 1985, and a larger data set derived by combining our data with those from two published series from the University of Minnesota that are comparable to our data. These combined data, which comprise the largest data set on the cytogenetics of lymphomas assembled so far, enabled a comprehensive analysis of correlation between chromosome change and tumor histology and the patterns of chromosome instability in these tumors. We found several significant associations, some previously described and others now recognized, between nonrandom chromosome gains, breaks, translocations, and deletions and histologic subtypes of tumors that characterize lymphomas. The data indicate that finding of chromosome breaks at certain sites (eg, 8q24, 14q32, 18q21) is of diagnostic value in dealing with cases of unusual lymphoma. Furthermore, nonrandom chromosome breakage exhibited three distinct patterns that reflected three levels of etiologically relevant genetic change. 相似文献
18.
19.
The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation. 相似文献
20.
Jacqueline AM Smith DL Patil OT Daniels Y-S Ding J-D Gallezot S Henry KHS Kim S Kshirsagar WJ Martin GP Obedencio E Stangeland PR Tsuruda W Williams RE Carson ST Patil 《The international journal of neuropsychopharmacology / official scientific journal of the Collegium Internationale Neuropsychopharmacologicum (CINP)》2015,18(2)