全文获取类型
收费全文 | 1880篇 |
免费 | 137篇 |
国内免费 | 63篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 94篇 |
妇产科学 | 19篇 |
基础医学 | 211篇 |
口腔科学 | 167篇 |
临床医学 | 150篇 |
内科学 | 413篇 |
皮肤病学 | 42篇 |
神经病学 | 92篇 |
特种医学 | 358篇 |
外科学 | 169篇 |
综合类 | 77篇 |
预防医学 | 88篇 |
眼科学 | 10篇 |
药学 | 121篇 |
中国医学 | 2篇 |
肿瘤学 | 64篇 |
出版年
2021年 | 16篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 18篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 33篇 |
2012年 | 30篇 |
2011年 | 47篇 |
2010年 | 29篇 |
2009年 | 38篇 |
2008年 | 48篇 |
2007年 | 85篇 |
2006年 | 49篇 |
2005年 | 63篇 |
2004年 | 41篇 |
2003年 | 46篇 |
2002年 | 39篇 |
2001年 | 58篇 |
2000年 | 46篇 |
1999年 | 51篇 |
1998年 | 67篇 |
1997年 | 76篇 |
1996年 | 71篇 |
1995年 | 68篇 |
1994年 | 47篇 |
1993年 | 57篇 |
1992年 | 49篇 |
1991年 | 55篇 |
1990年 | 44篇 |
1989年 | 78篇 |
1988年 | 65篇 |
1987年 | 70篇 |
1986年 | 53篇 |
1985年 | 66篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 36篇 |
1978年 | 19篇 |
1977年 | 26篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1974年 | 18篇 |
1973年 | 9篇 |
1972年 | 11篇 |
1970年 | 15篇 |
1967年 | 9篇 |
排序方式: 共有2080条查询结果,搜索用时 330 毫秒
21.
Low-artifact intravascular devices: MR imaging evaluation 总被引:2,自引:0,他引:2
Teitelbaum GP; Ortega HV; Vinitski S; Stern H; Tsuruda JS; Mitchell DG; Rifkin MD; Bradley WG Jr 《Radiology》1988,168(3):713-719
Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible. 相似文献
22.
23.
24.
25.
Gor DO Ding X Li Q Schreiber JR Dubinsky M Greenspan NS 《Infection and immunity》2002,70(10):5589-5595
Immunization of mice with pneumococcal surface adhesin A (PsaA) emulsified in complete Freund's adjuvant (CFA) provides protection against systemic infection with Streptococcus pneumoniae. Because the use of CFA is not acceptable in humans, we sought to develop alternative means of enhancing the immunogenicity of protein antigens of potential use in pneumococcal vaccines. We designed a series of genetic constructs in which coding sequences for PsaA were linked to sequences encoding either murine interleukin-2 (mIL-2), mIL-4, or two copies of an immunostimulatory nonapeptide derived from mIL-1beta. The PsaA-cytokine constructs were cloned and expressed in Escherichia coli. Mice immunized twice with PsaA-IL-2, or PsaA-IL-4 responded with PsaA-specific antibody production comparable in magnitude to that of mice primed with PsaA in CFA and boosted with PsaA in incomplete Freund's adjuvant (PsaA-Adj). Antibodies elicited by PsaA-Adj were predominantly of the immunoglobulin G1 (IgG1) subclass, while PsaA-IL-2 and PsaA-IL-4 elicited substantial amounts of IgG2a in addition to IgG1. Mice immunized with PsaA-Adj or PsaA-IL-4 were partially protected against intraperitoneal challenge with virulent S. pneumoniae (30% overall survival beyond 15 days postchallenge). Mice immunized with PsaA and no adjuvant or PsaA-IL-2 exhibited 0 or 5% survival rates, respectively, following challenge. In contrast, mice immunized twice with capsular polysaccharide were 100% protected. The modest levels of protection seen in mice immunized with PsaA and its more immunogenic derivatives may be explained in part by the relative inaccessibility of antibody to PsaA on the surface of encapsulated S. pneumoniae. 相似文献
26.
Diagnosis of Epstein-Barr virus infection in hairy leukoplakia by using nucleic acid hybridization and noninvasive techniques.
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Y G De Souza U K Freese D Greenspan J S Greenspan 《Journal of clinical microbiology》1990,28(12):2775-2778
The presence of Epstein-Barr virus (EBV) DNA in the epithelial cells of oral hairy leukoplakia is the confirming criterion in the diagnosis of this lesion, which occurs mainly in persons infected by the human immunodeficiency virus. Because hairy leukoplakia often presages the development of the acquired immune deficiency syndrome, it is important that suspicious lesions be accurately diagnosed. Commonly, biopsy tissue is removed for detection of EBV DNA by in situ hybridization, but biopsy is contraindicated in some patients. This study evaluated filter and cytospin in situ hybridization, two noninvasive techniques that examine epithelial cells swabbed from the surfaces of the lesions, for their sensitivity in detecting EBV DNA. As compared with tissue in situ hybridization, the filter and cytospin techniques had sensitivities of 100 and 92%, respectively. We conclude that these two noninvasive techniques can provide the clinician with an accurate alternative to biopsy whenever this human immunodeficiency virus-associated lesion is suspected. 相似文献
27.
28.
Induction of HLA-DR expression on thyroid follicular cells by cytomegalovirus infection in vitro. Evidence for a dual mechanism of induction. 总被引:1,自引:1,他引:1
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)
Cytomegalovirus (CMV) infection of primary cultures established from human thyroid nodular and normal (paranodular) tissues resulted in induction of human leukocyte antigen (HLA) DR expression on thyroid follicular cells (TFC), as detected by cell-surface immunofluorescence staining with monoclonal antibodies (MAb). Two distinct modalities of induction were observed. The first type occurred in cultures of normal tissue obtained from CMV-seropositive but not seronegative donors, was detected on 30% to 50% of the TFCs, even though the vast majority of these cells failed to show any morphologic or antigenic evidence of individual CMV infection, and was associated with production of gamma-interferon (gamma-IFN) in vitro. The induced molecules displayed the characteristic DR polypeptide profile on immunoprecipitation and electrophoretic analysis. These results demonstrate that CMV infection of normal thyroid cultures may induce DR expression on TFCs in the absence of pre-existing lymphoid infiltrates and suggest that the induction is the result of an in vitro response to CMV by previously sensitized immunocompetent cells present in these primary cultures. Such a response, associated with the release of gamma-IFN, would induce DR expression on neighboring uninfected cells. The second mode of induction occurred in all CMV-infected cultures, regardless of their tissue origin (nodular or normal) or the serologic status of the donors. Up to 50% of infected TFCs at a late stage of infection, having fully developed CMV antigen-positive intranuclear inclusions, also displayed the cell-surface DR-related determinant recognized by one of the four anti-DR MAbs used. This induction was restricted to TFCs, while CMV-infected fibroblastoid cells present in the monolayers were invariably negative. Induction by CMV of major histocompatibility class II antigens on human epithelial cells may have significant implications in the development of normal immune responses against local viral infection, the enhancement of alloimmune rejection of grafted organs, and the generation of organ-specific autoimmune responses. 相似文献
29.
30.
Neurofibromatosis 2 (NF2) is an inherited cancer syndrome resulting from
mutations in the NF2 tumor suppressor gene. Analysis of NF2 mutations has
revealed some general genotype-phenotype correlations. Severe disease has
been associated with mutations that produce a premature termination while
more mild disease has been associated with missense mutations. Here, we
provide experimental proof for these genotype-phenotype correlations by
demonstrating that nonsense mutations fail to produce stable merlin protein
while missense mutations result in the generation of merlin proteins
defective in negative growth regulation. This inability to suppress cell
growth may result from defects in the function of merlin at several levels,
including failure to form an intramolecular complex. Based on these
findings, we propose a model for merlin growth suppression that provides a
framework for analyzing NF2 patient mutations and merlin function.
相似文献