全文获取类型
收费全文 | 15423篇 |
免费 | 1022篇 |
国内免费 | 217篇 |
专业分类
耳鼻咽喉 | 220篇 |
儿科学 | 356篇 |
妇产科学 | 737篇 |
基础医学 | 1962篇 |
口腔科学 | 269篇 |
临床医学 | 1644篇 |
内科学 | 3273篇 |
皮肤病学 | 391篇 |
神经病学 | 940篇 |
特种医学 | 529篇 |
外科学 | 2330篇 |
综合类 | 432篇 |
现状与发展 | 2篇 |
一般理论 | 3篇 |
预防医学 | 764篇 |
眼科学 | 294篇 |
药学 | 1110篇 |
中国医学 | 104篇 |
肿瘤学 | 1302篇 |
出版年
2023年 | 79篇 |
2022年 | 240篇 |
2021年 | 435篇 |
2020年 | 222篇 |
2019年 | 330篇 |
2018年 | 426篇 |
2017年 | 292篇 |
2016年 | 300篇 |
2015年 | 464篇 |
2014年 | 593篇 |
2013年 | 741篇 |
2012年 | 1113篇 |
2011年 | 1099篇 |
2010年 | 713篇 |
2009年 | 593篇 |
2008年 | 884篇 |
2007年 | 920篇 |
2006年 | 816篇 |
2005年 | 823篇 |
2004年 | 709篇 |
2003年 | 584篇 |
2002年 | 546篇 |
2001年 | 480篇 |
2000年 | 416篇 |
1999年 | 354篇 |
1998年 | 144篇 |
1997年 | 120篇 |
1996年 | 108篇 |
1995年 | 80篇 |
1994年 | 88篇 |
1993年 | 49篇 |
1992年 | 181篇 |
1991年 | 174篇 |
1990年 | 152篇 |
1989年 | 129篇 |
1988年 | 114篇 |
1987年 | 126篇 |
1986年 | 108篇 |
1985年 | 88篇 |
1984年 | 79篇 |
1983年 | 58篇 |
1980年 | 40篇 |
1979年 | 59篇 |
1978年 | 53篇 |
1977年 | 54篇 |
1976年 | 41篇 |
1975年 | 39篇 |
1974年 | 47篇 |
1972年 | 59篇 |
1971年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Plurihormonal pituitary adenomas: immunostaining of all pituitary hormones is mandatory for correct classification 总被引:4,自引:0,他引:4
AIMS: We studied the clinicopathological characteristics of plurihormonal pituitary adenomas. METHODS AND RESULTS: The study material included 167 plurihormonal adenomas, which consisted of 31% of the surgically removed pituitary adenomas that we collected during a 12-year period. The mean age of patients with plurihormonal adenoma was 45.7 years (range 13-75 years). There were 86 men and 81 women. All tumours were fully classified by immunohistochemical staining for seven pituitary hormones or subunits. Thirty immunohistochemical subtypes of plurihormonal adenomas were recognized. Hormonal symptoms were present in 70% of patients, while serum hormonal levels were increased in 89% of patients. Most patients had symptoms related to only one of the hormones and only 7% of patients had symptoms related to two hormones. The most common hormonal symptom was acromegaly (50%); symptoms related to hyperprolactinaemia ranked second (20%). Double immunostaining of all the possible combinations of the hormones was performed in 30 selected tumours, and they all showed mixtures of hormones in individual adenoma cells in any hormonal combinations studied. The latter finding supported the view that plurihormonal adenomas are monomorphous adenomas. CONCLUSIONS: Plurihormonal adenomas are common pituitary adenomas. Immunohistochemical staining of all pituitary hormones is mandatory for correct classification. 相似文献
82.
Enzymatic characterization of 48 Aeromonas hydrophila complex isolates from various sources was determined with the API ZYM system (Analytab Products, Plainview, N.Y.). All isolates lacked valine and cystine aminopeptidases, chymotrypsin, alpha-mannosidase, alpha-fucosidase, alpha-galactosidase, and beta-glucuronidase but possessed caprylate esterase-lipase, leucine aminopeptidase, acid phosphatase, phosphoamidase, and N-acetyl-beta-glucosidase. Variability was found in the presence of alkaline phosphatase, butyrate esterase, myristate lipase, trypsin, beta-galactosidase, alpha-glucosidase, and beta-glucosidase. No significant differences were evident among the enzymatic profiles of isolates from various sources. 相似文献
83.
Peripheral blood lymphocytes from a patient (EP) with lymphosarcoma cell leukaemia reported previously, had been found capable of forming sheep erythrocyte rosettes, reacting with T cell-specific antiserum and carrying surface immunoglobulins (Ig), IgM and IgD. It was suggested that the surface Ig were generated by leukaemic T cells due to activation of genes controlling synthesis of surface Ig. We here present evidence that these lymphocytes also carry complement receptors of B cells as detected by bovine erythrocyte–anti-bovine serum–complement complexes and by complement-coated zymosan. This study firmly establishes the presence of dual surface markers for T and B cells on the same leukaemic lymphocytes. 相似文献
84.
Isolation and characterization of recombinant Escherichia coli clones secreting a 24-kilodalton antigen of Treponema pallidum. 总被引:3,自引:3,他引:3
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Escherichia coli clones containing Treponema pallidum DNA in the pUC8 vector and secreting a 24-kilodalton antigen of T. pallidum have been isolated. Both syphilitic human and syphilis-immune rabbit sera reacted with the recombinant p24 antigen, indicating that an equivalent protein in T. pallidum is capable of eliciting antibody responses during natural infections. The p24 antigen of T. pallidum was identified by using two-dimensional gel electrophoresis and immunoblotting with monospecific anti-p24 serum. We tentatively concluded that this cloned antigen is a secreted protein or a labile or minor component of T. pallidum because (i) p24 was secreted by the recombinant E. coli cells; (ii) recombinant p24 in E. coli cells was processed into several smaller species with molecular masses ranging from 12 to 20 kilodaltons, which correlate well with the masses of secreted antigens described by others; and (iii) p24 protein appeared to be highly antigenic during natural infections, but only a very small amount of this antigen was associated with or retained by the purified organisms. The possible role of the p24 protein in determining the growth characteristics of T. pallidum is suggested by the ability of recombinant p24 to induce growth changes in E. coli cells. All E. coli colonies expressing the p24 polypeptide exhibited a flat and rough colony morphology and a filamentous growth pattern that were different from those of other E. coli cells. The DNA sequence coding for the p24 polypeptide is located on a 1.7-kilobase-pair BamHI fragment of the T. pallidum genomic DNA and is absent in the nonpathogenic Treponema phagedenis DNA. However, any possible relationship between the p24 antigen and the virulence of T. pallidum remains to be determined. In preliminary studies, rabbits immunized with the purified p24 were not protected from the infection with live T. pallidum organisms. 相似文献
85.
The syndrome of ectrodactyly, ectodermal dysplasia and cleft lip and palate: report of a family demonstrating a dominant inheritance pattern 总被引:1,自引:0,他引:1
The syndrome of ectrodactyly, ectodermal dysplasia and cleft lip and palate (EEC syndrome) is described in a mother and 3 of her 4 children. Autosomal dominant inheritance was suggested in this family. However, genetic heterogeneity may exist in this syndrome. The significance of associated finClings, incluCling carcinoma of the cervix uteri, lacrimal duct stenosis and urinary tract strictures in patients with ectodermal dysplasia is considered. 相似文献
86.
Specific and nonspecific immune factors in dental plaque fluid and saliva from young and old populations. 总被引:6,自引:11,他引:6
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M F Cole S D Hsu B J Baum W H Bowen L I Sierra M Aquirre G Gillespie 《Infection and immunity》1981,31(3):998-1002
Separate samples of supragingival dental plaque overtly free of blood were centrifuged to obtain the free fluid phase (plaque fluid). Bound protein was eluted from the plaque bacteria and matrix by washing the plaque with a low-pH buffer. The plaque fluid, low pH eluate, and whole saliva were assayed for immunoglobulins A, G, and M, the third component of complement, lysozyme, lactoferrin, and lactoperoxidase. Concentrations of total protein and albumin were also determined. Antibody reactive with specific plaque bacteria was detected by indirect immunofluorescent microscopy. Specific and nonspecific immune proteins were present in plaque fluid from adult subjects at significantly greater concentrations than in their saliva, which suggests that these proteins are concentrated in dental plaque. The results indicate that both saliva and gingival exudate contribute to the immunological proteins found in the free fluid phase of dental plaque. The observation that immunoglobulin A antibody reactive with plaque bacteria could be detected in plaque fluid suggests that a wide variety of immunological reactions may occur in the dental plaque. These potential interactions between host, plaque bacteria, and their products could serve to influence the plaque flora and its ability to induce disease. 相似文献
87.
Human melanoma progression in skin reconstructs : biological significance of bFGF 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Meier F Nesbit M Hsu MY Martin B Van Belle P Elder DE Schaumburg-Lever G Garbe C Walz TM Donatien P Crombleholme TM Herlyn M 《The American journal of pathology》2000,156(1):193-200
Human skin reconstructs are three-dimensional in vitro models consisting of epidermal keratinocytes plated onto fibroblast-contracted collagen gels. Cells in skin reconstructs more closely recapitulate the in situ phenotype than do cells in monolayer culture. Normal melanocytes in skin reconstructs remained singly distributed at the basement membrane which separated the epidermis from the dermis. Cell lines derived from biologically early primary melanomas of the radial growth phase proliferated in the epidermis and the basement membrane was left intact. Growth and migration of the radial growth phase melanoma cells in the dermal reconstruct and tumorigenicity in vivo were only observed when cells were transduced with the basic fibroblast growth factor gene, a major autocrine growth stimulator for melanomas. Primary melanoma cell lines representing the more advanced stage vertical growth phase invaded the dermis in reconstructs and only an irregular basement membrane was formed. Metastatic melanoma cells rapidly proliferated and aggressively invaded deep into the dermis, with each cell line showing typical invasion and growth characteristics. Our results demonstrate that the growth patterns of melanoma cells in skin reconstructs closely correspond to those in situ and that basic fibroblast growth factor is critical for progression. 相似文献
88.
An indirect immunoperoxidase (IP) slide test was evaluated for the laboratory identification of Bacteroides fragilis. Antigen-antibody complexes were detected with goat anti-rabbit immunoglobulin G-peroxidase conjugate with 3-amino-9-ethyl-carbazole as the peroxidase substrate. Ninety-one percent of 44 B. fragilis strains tested were IP positive (3+ to 4+ reactions) with greater than or equal to 1:160 dilutions of rabbit antiserum produced against whole cells of B. fragilis ATCC 23745. The antiserum was species specific. No cross-reactions were observed with 35 Bacteroides strains of other species or with a variety of facultative or aerobic gram-negative bacilli. Four B. fragilis strains were IP negative. One of these (VPI 2393) was the deoxyribonucleic acid (DNA) homology group II reference strain. The other three were clinical isolates. IP-negative and representative IP-positive strains were tested for DNA homology with the type strains for DNA homology groups I and II (VPI 2553 and VPI 2393). Two of the three clinical isolates were classified as DNA homology group II, and the remaining strain was classified as a group I. Capsular material known to be unique to B. fragilis was common to both DNA homology groups as indicated by reactions with purified anticapsular antiserum. The IP technique provides a suitable alternative to fluorescent microscopy for the rapid immunological identification of B. fragilis. 相似文献
89.
Bacteria or their products may cause chronic inflammation and subsequent bone loss. This inflammation and bone loss may be associated with significant morbidity in chronic otitis media, periodontitis, endodontic lesions, and loosening of orthopedic implants caused by lipopolysaccharide (LPS)-contaminated implant particles. Currently, it is not clear how bacteria or endotoxin-induced bone resorption occurs and what cell types are involved. Here we report that Porphyromonas gingivalis, a periodontal pathogen, and Escherichia coli LPS induce osteoclastic cell formation from murine leukocytes in the absence of osteoblasts. In contrast, stimulation with parathyroid hormone had no effect. These multinucleated, tartrate-resistant acid phosphatase-positive cells were positive for receptor activator of NF-kappaB (RANK), the receptor for osteoprotegerin ligand (OPGL), also known as RANK ligand (RANKL). Blocking antibodies demonstrated that their formation was dependent upon expression of OPGL and, to a lesser extent, on tumor necrosis factor alpha. Mononuclear cells represented a significant source of OPGL production. In vivo, P. gingivalis injection stimulated OPGL expression in both mononuclear leukocytes and osteoblastic cells. Thus, these findings describe a pathway by which bacteria could enhance osteolysis independently of osteoblasts and suggest that the mix of cells that participate in inflammatory and physiologic bone resorption may be different. This may give insight into new targets of therapeutic intervention. 相似文献
90.
Reibman J Hsu Y Chen LC Kumar A Su WC Choy W Talbot A Gordon T 《American journal of respiratory cell and molecular biology》2002,27(4):455-462
Environmental pollutants, including ambient particulate matter (PM), increase respiratory morbidity. Studies of model PM particles, including residual oil fly ash and freshly generated diesel exhaust particles, have demonstrated that PM affects inflammatory airway responses. Neither of these particles completely represents ambient PM, and therefore questions remain about ambient particulates. We hypothesized that ambient PM of different size fractions collected from an urban environment (New York City air), would activate primary culture human bronchial epithelial cells (HBECs). Because of the importance of granulocyte-macrophage colony-stimulating factor (GM-CSF) on inflammatory and immunomodulatory processes, we focused our studies on this cytokine. We demonstrated that the smallest size fraction (ultrafine/fine; < 0.18 micro m) of ambient PM (11 micro g/cm(2)), upregulated GM-CSF production (2-fold increase). The absence of effect of carbon particles of similar size, and the day-to-day variation in response, suggested that the chemical composition, but not the particle itself, was necessary for GM-CSF induction. Activation of the extracellular signal-regulated kinase and the p38 mitogen-activated protein kinase was associated with, and necessary for, GM-CSF release. These studies serve to corroborate and extend those on model particles. Moreover, they emphasize the role of the smallest size ambient particles in airway epithelial cell responses. 相似文献