全文获取类型
收费全文 | 7735篇 |
免费 | 678篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 146篇 |
儿科学 | 247篇 |
妇产科学 | 166篇 |
基础医学 | 926篇 |
口腔科学 | 198篇 |
临床医学 | 818篇 |
内科学 | 1361篇 |
皮肤病学 | 73篇 |
神经病学 | 921篇 |
特种医学 | 232篇 |
外科学 | 1445篇 |
综合类 | 112篇 |
一般理论 | 6篇 |
预防医学 | 715篇 |
眼科学 | 129篇 |
药学 | 465篇 |
中国医学 | 14篇 |
肿瘤学 | 453篇 |
出版年
2023年 | 80篇 |
2022年 | 139篇 |
2021年 | 324篇 |
2020年 | 172篇 |
2019年 | 256篇 |
2018年 | 262篇 |
2017年 | 216篇 |
2016年 | 228篇 |
2015年 | 247篇 |
2014年 | 318篇 |
2013年 | 346篇 |
2012年 | 552篇 |
2011年 | 539篇 |
2010年 | 299篇 |
2009年 | 242篇 |
2008年 | 393篇 |
2007年 | 376篇 |
2006年 | 387篇 |
2005年 | 332篇 |
2004年 | 307篇 |
2003年 | 264篇 |
2002年 | 221篇 |
2001年 | 150篇 |
2000年 | 136篇 |
1999年 | 117篇 |
1998年 | 61篇 |
1997年 | 48篇 |
1996年 | 65篇 |
1995年 | 54篇 |
1994年 | 41篇 |
1993年 | 40篇 |
1992年 | 104篇 |
1991年 | 98篇 |
1990年 | 90篇 |
1989年 | 64篇 |
1988年 | 69篇 |
1987年 | 93篇 |
1986年 | 53篇 |
1985年 | 57篇 |
1984年 | 48篇 |
1983年 | 48篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1979年 | 42篇 |
1978年 | 34篇 |
1976年 | 23篇 |
1974年 | 24篇 |
1973年 | 28篇 |
1970年 | 24篇 |
1968年 | 25篇 |
排序方式: 共有8427条查询结果,搜索用时 15 毫秒
61.
62.
Philip Cheng Melynda D Casement David A Kalmbach Andrea Cuamatzi Castelan Christopher L Drake 《Sleep》2021,44(4)
Study ObjectivesStressful life events contribute to insomnia, psychosocial functioning, and illness. Though individuals with a history of insomnia may be especially vulnerable during stressful life events, risk may be mitigated by prior intervention. This study evaluated the effect of prior digital cognitive-behavioral therapy for insomnia (dCBT-I) versus sleep education on health resilience during the COVID-19 pandemic.MethodsCOVID impact, insomnia, general- and COVID-related stress, depression, and global health were assessed in April 2020 in adults with a history of insomnia who completed a randomized controlled trial of dCBT-I (n = 102) versus sleep education control (n = 106) in 2016–2017. Regression analyses were used to evaluate the effect of intervention conditions on subsequent stress and health during the pandemic.ResultsInsomnia symptoms were significantly associated with COVID-19 related disruptions, and those who previously received dCBT-I reported less insomnia symptoms, less general stress and COVID-related cognitive intrusions, less depression, and better global health than those who received sleep education. Moreover, the odds for resurgent insomnia was 51% lower in the dCBT-I versus control condition. Similarly, odds of moderate to severe depression during COVID-19 was 57% lower in the dCBT-I condition.ConclusionsThose who received dCBT-I had increased health resilience during the COVID-19 pandemic in adults with a history of insomnia and ongoing mild to moderate mental health symptoms. These data provide evidence that dCBT-I is a powerful tool to promote mental and physical health during stressors, including the COVID-19 pandemic.Clinical Trial Registration NCT02988375相似文献
63.
64.
Dendritic cells pulsed with a recombinant chlamydial major outer membrane protein antigen elicit a CD4(+) type 2 rather than type 1 immune response that is not protective 总被引:3,自引:0,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)
Chlamydia trachomatis is an obligate intracellular bacterium that infects the oculogenital mucosae. C. trachomatis infection of the eye causes trachoma, the leading cause of preventable blindness. Infections of the genital mucosae are a leading cause of sexually transmitted diseases. A vaccine to prevent chlamydial infection is needed but has proven difficult to produce by using conventional vaccination approaches. Potent immunity to vaginal rechallenge in a murine model of chlamydial genital infection has been achieved only by infection or by immunization with dendritic cells (DC) pulsed ex vivo with whole inactivated organisms. Immunity generated by infection or ex vivo antigen-pulsed DC correlates with a chlamydia-specific interleukin 12 (IL-12)-dependent CD4(+) Th1 immune response. Because of the potent antichlamydial immunizing properties of DC, we hypothesized that DC could be a powerful vehicle for the delivery of individual chlamydial antigens that are thought to be targets for more conventional vaccine approaches. Here, we investigated the recombinant chlamydial major outer membrane protein (rMOMP) as a target antigen. The results demonstrate that DC pulsed with rMOMP secrete IL-12 and stimulate infection-sensitized CD4(+) T cells to proliferate and secrete gamma interferon. These immunological properties implied that rMOMP-pulsed DC would be potent inducers of MOMP-specific CD4(+) Th1 immunity in vivo; however, we observed the opposite result. DC pulsed ex vivo with rMOMP and adoptively transferred to naive mice generated a Th2 rather than a Th1 anti-MOMP immune response, and immunized mice were not protected following infectious challenge. We conclude from these studies that the immunological properties of ex vivo pulsed DC are not necessarily predictive of the immune response generated in vivo following adoptive transfer. These findings suggest that the nature of the antigen used to pulse DC ex vivo influences the Th1-Th2 balance of the immune response in vivo. 相似文献
65.
Takebumi Onda Drake Laface Gottfried Baier Thomas Brunner Nakayuki Honma Toshifumi Mikayama Amnon Altman Douglas R. Green 《Molecular immunology》1995,32(17-18)
The process of T cell recognition involves a complex set of interactions between the various components of the TCR/MHC/peptide trimolecular complex. We have developed a system for exploring the specific binding interactions contributed by the constituent subunits of TCR complexes for components of their ligands. We utilized an M13 phage display system, designed for multivalent receptor display, to explore specific binding interactions between various TCRα chains and specific antigen in the absence of MHC. The multivalent TCR-phage display system was sensitive enough to reveal some TCRα chains capable of binding directly to antigen with the same fine specificity shown by the MHC-restricted T cells from which the α chains were derived. Cross-specificity analysis using two antigen-binding TCRα chains derived from T cells with different polypeptide antigen specificities confirmed the fidelity of this binding. In mixtures of antigen-binding and non-binding TCRα-displaying phage, specific selection was achieved at a starting frequency of 1/1000, suggesting that this system can be employed for selection and analysis of TCR-displaying phage libraries. While the binding specificities exhibited by these TCRs are unusual, they provide a novel perspective from which to study the specific binding interactions that constitute TCR antigen binding. 相似文献
66.
The speed with which insulin alters hepatocyte ultrastructure and glycogen levels in insulin-deficient rats has been studied. Insulin deficiency was induced with alloxan, followed by insulin treatment with regular and NPH insulin. Rats were killed at various times after the insulin injection, blood samples were obtained, plasma glucose levels were determined, and liver samples were prepared for electron microscopy and glycogen determinations. Plasma glucose levels in insulin-deficient rats declined to normal values by 4 hours post insulin, returning to insulin-deficient levels by 8 hours post insulin. Hepatic glycogen was considerably reduced in the insulin-deficient rats. By 1 hour post insulin hepatic glycogen increased, reached maximal levels by 8 hours, then declined to insulin-deficient levels by 36 hours. The ultrastructural appearance of both centrilobular and periportal hepatocytes from insulin-deficient rats showed abundant vesicular smooth endoplasmic reticulum (SER), decreased rough endoplasmic reticulum (RER), and enlarged RER intracisternal spaces. One-half hour post insulin, centrilobular hepatocytes were unchanged. In periportal hepatocytes, however, vesicular SER was no longer visible, the RER intracisternal spaces appeared normal, and the amount of RER had increased. By 1 hour post insulin the centrilobular hepatocytes showed similar ultrastructural changes. These changes became more pronounced in the next few hours and remained through 24 hours. By 36 hours both centrilobular and periportal hepatocytes appeared similar to those in the insulin-deficient rat. These results demonstrate the rapid and lobular-specific effects insulin has on the hepatocyte. 相似文献
67.
Development of a radioimmunoassay for Escherichia coli heat-stable enterotoxin: comparison with the suckling mouse bioassay. 总被引:11,自引:9,他引:11
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 strains which produce heat-stable enterotoxin (ST) are usually identified by demonstrating the production of ST. At present, ST can be detected only by bioassay methods. Recently, we purified E. coli ST, which enabled us to develop a radioimmunoassay for ST. Radioiodination of ST was performed by the lactoperoxidase method, which resulted in a high specific activity and retained the biological activity of St. Anti-ST antisera were raised in goats by injecting the goats with pure ST coupled to bovine immunoglobin G. Antibody titers ranged from 1:8,000 to 1:40,000. Using these reagents, we examined assay conditions thoroughly and found that a 14- to 18-h incubation at 4 degrees C in sodium acetate buffer with an ionic strength of 120 mM (pH 6.2) gave maximal sensitivity and reproducibility. Free ST was separated from antibody-bound ST by dextran-coated charcoal. This radioimmunoassay accurately and reproducibly measured ST in the range from 50 to 500 pg of ST per tube and could quantitate ST accurately in complex bacteriological media. This assay was specific for STa, measured human and porcine STa equally well, and did not cross-react with STb, with several other enterotoxins, or with various gastrointestinal peptides. Intact disulfide bridges in the ST molecule were required for immunoreactive activity. 相似文献
68.
Inhibition of Bacteroides fragilis on blood agar plates and reversal of inhibition by added hemin. 总被引:2,自引:0,他引:2
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)
T D Wilkins S L Chalgren F Jimenez-Ulate C R Drake Jr J L Johnson 《Journal of clinical microbiology》1976,3(3):359-363
Bacteroides fragilis strains formed much smaller colonies on most types of blood agar plates than they did on the same media without blood. Blood inhibited strains of B. fragilis subsp. distasonis the most and B. fragilis subsp. fragilis the least. The inhibition could be eliminated by adding hemin to the blood agar. The inhibitory component of the blood was inside the erythrocytes and appeared to be the hemin-free globin of hemoglobin. 相似文献
69.
Comparison of chlorhexidine and tincture of iodine for skin antisepsis in preparation for blood sample collection
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)
Rates of contamination of blood cultures obtained when skin was prepared with iodine tincture versus chlorhexidine were compared. For iodine tincture, the contamination rate was 2.7%; for chlorhexidine, it was 3.1%. The 0.41% difference is not statistically significant. Chlorhexidine has comparable effectiveness and is safer, cheaper, and preferred by staff, so it is an alternative to iodine tincture. 相似文献
70.
Aim—To determine whether the fluorescent in situ hybridisation technique (FISH) using a total human DNA genomic probe can be used to enumerate semen leucocytes. 相似文献