全文获取类型
收费全文 | 742篇 |
免费 | 36篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 69篇 |
妇产科学 | 13篇 |
基础医学 | 116篇 |
口腔科学 | 10篇 |
临床医学 | 60篇 |
内科学 | 207篇 |
皮肤病学 | 30篇 |
神经病学 | 16篇 |
特种医学 | 132篇 |
外科学 | 49篇 |
综合类 | 11篇 |
预防医学 | 16篇 |
眼科学 | 3篇 |
药学 | 25篇 |
1篇 | |
中国医学 | 6篇 |
肿瘤学 | 22篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 28篇 |
2011年 | 20篇 |
2010年 | 33篇 |
2009年 | 39篇 |
2008年 | 24篇 |
2007年 | 32篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 25篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 29篇 |
1997年 | 27篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 36篇 |
1993年 | 19篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 22篇 |
1988年 | 30篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有788条查询结果,搜索用时 139 毫秒
11.
SE Andrew 《Clinical genetics》2003,64(4):293-296
12.
13.
The role of Toll-like receptors and Nod proteins in bacterial infection 总被引:22,自引:0,他引:22
Our understanding of innate immunity in mammals has greatly expanded following the discovery of the family of membrane-bound receptors, called the Toll-like receptors (TLRs). More recently, the nucleotide-binding oligomerisation domain (Nod) molecules, Nod1 and Nod2, which are cytoplasmic surveillance proteins, have also been shown to be involved in the innate immune response. These two classes of detection molecules, classified as "pattern recognition receptors" (PRRs), detect microbial ligands in order to initiate a defense response to fight infectious disease. These microbial ligands or "pathogen-associated molecular patterns" (PAMPs), detected by TLRs and Nods are often structural components of the microorganism that are not subject to much variation. These include such factors as lipopolysaccharide (LPS) and peptidoglycan from the cell walls of bacteria. In order to understand the role of TLRs and Nod proteins in infectious disease in vivo it is important to define the site of interaction between PRRs and PAMPS. Additionally, the challenge of mice deficient in the various PRRs in natural infection models will help to decipher the contribution of these molecules not only in the innate immune response against pathogen infection but also how these proteins may instruct the adaptive immune response in order to have a tailored immune response against a particular microbe. 相似文献
14.
Debelenko LV; Brambilla E; Agarwal SK; Swalwell JI; Kester MB; Lubensky IA; Zhuang Z; Guru SC; Manickam P; Olufemi SE; Chandrasekharappa SC; Crabtree JS; Kim YS; Heppner C; Burns AL; Spiegel AM; Marx SJ; Liotta LA; Collins FS; Travis WD; Emmert-Buck MR 《Human molecular genetics》1997,6(13):2285-2290
Lung carcinoids occur sporadically and rarely in association with multiple
endocrine neoplasia type 1 (MEN1). There are no well defined genetic
abnormalities known to occur in these tumors. We studied 11 sporadic lung
carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene
on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy
fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was
studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene
were inactivated. All four tumors showed the presence of a MEN1 gene
mutation and loss of the other allele. Observed mutations included a 1 bp
insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide
substitution affecting a donor splice site. Each mutation predicts
truncation or potentially complete loss of menin. The remaining seven
tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH.
The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a
complex germline MEN1 gene mutation. The data implicate the MEN1 gene in
the pathogenesis of sporadic lung carcinoids, representing the first
defined genetic alteration in these tumors.
相似文献
15.
A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms, and risk of colorectal adenoma 总被引:8,自引:2,他引:8
Chen J; Giovannucci E; Hankinson SE; Ma J; Willett WC; Spiegelman D; Kelsey KT; Hunter DJ 《Carcinogenesis》1998,19(12):2129-2132
We examined the relationship between a functional polymorphism (667C--
>T, ala-->val) of the methylenetetrahydrofolate reductase gene
(MTHFR) and the risk of colorectal adenomas in the prospective Nurses'
Health Study. Among 257 incident polyp cases and 713 controls, the MTHFR
val/val polymorphism [relative risk (RR) = 1.35, 95% confidence interval
(CI) 0.84-2.17] was not significantly associated with risk of adenomas.
This lack of association was observed for both small (RR = 1.36, 95% CI
0.76-2.45) and large (RR = 1.32, 95% CI 0.66-2.66) adenomas. Furthermore,
there was no significant interaction between this polymorphism and
consumption of either folate, methionine or alcohol. We also examined the
relationship of a newly identified polymorphism (asp919gly) of the
methionine synthase gene (MS) with the risk of colorectal adenomas in the
same population. The MS gly/gly polymorphism was also not significantly
associated with risk of colorectal adenomas (RR = 0.66, 95% CI 0.26-1.70).
These results, which need to be confirmed in other studies, suggest that
the MTHFR val/val polymorphism, which has been previously inversely
associated with risk of colorectal cancer, plays a role only in a late
stage (adenoma-- >carcinoma) of colorectal tumorigenesis, and/or may
protect against malignant transformation in the subset of benign adenomas,
which may progress to malignancy.
相似文献
16.
17.
18.
Transforming growth factor beta (TGF-beta) is a bifunctional regulator of the growth of myeloid progenitors and is here demonstrated to directly inhibit the growth of primitive erythroid progenitors by 95% to 100% regardless of the cytokines stimulating growth. Autocrine TGF- beta production of primitive hematopoietic progenitors has previously been reported. In the present study, a neutralizing TGF-beta antibody (anti-TGF-beta) added to serum-containing cultures, resulted in a 3-, 4- , and 25-fold increase in burst-forming unit erythroid (BFU-E) colony formation in response to interleukin-4 (IL-4) plus erythropoietin (Epo), SCF plus Epo, and IL-11 plus Epo, respectively. The growth of BFU-E progenitors has been suggested to require a burst-promoting activity in addition to Epo. Accordingly, we observed no BFU-E colony formation in serum-containing cultures in response to Epo alone. In contrast, 50 BFU-E colonies were formed when anti-TGF-beta was included in the culture. In serum-free cultures, Epo also stimulated BFU-E colony formation in the absence of other cytokines, whereas anti-TGF- beta had no effect on the number of colonies formed. Quantitation of TGF-beta 1 in serum by an enzyme-linked immunosorbent assay method showed predominantly the presence of precursor (latent) TGF-beta 1, but also showed active TGF-beta 1 at a concentration sufficient to potently inhibit erythroid colony formation. Thus, neutralization of active TGF- beta 1 in serum shows that Epo alone is sufficient to stimulate the growth of murine BFU-E progenitors. 相似文献
19.
Fluorescent in vivo tracking of hematopoietic cells. Part I. Technical considerations 总被引:3,自引:1,他引:3
We report a new technology for in vivo tracking of hematopoietic cells, using fluorescent lipophilic probes. Because the probe is irreversibly bound in the lipids of the cell membrane; substantial numbers of dye molecules can be incorporated per cell and thus substantial signal to noise can be achieved. Although this technology can be used for all hematopoietic cells, these first findings are reported on red blood cells (RBCs) owing to the importance of the membrane to RBC function and integrity. We demonstrated that labeling 10% of the RBCs of a rabbit and reinjecting them into the animal makes possible the tracking of these cells at various times after injection. Furthermore, the labeling appears not to affect in vivo cell lifetime or cellular volume changes in response to hypotonic shock. The single cell fluorescence intensity of the labeled RBCs remains relatively constant for 60 days, and an immune response appears not to be generated against labeled cells. That labeled RBCs have lifetime kinetics in vivo, as shown in other studies, indicates that the membranes are functioning normally and are unaltered by the labeling technology. The technology we present is also applicable to white blood cells, bone marrow, and platelets. 相似文献
20.
Melatonin effects on sleep, mood, and cognition in elderly with mild cognitive impairment 总被引:3,自引:1,他引:3
Abstract: The effects of immediate-release melatonin on circadian rest-activity profiles, cognition, and mood were investigated in ten elderly individuals with self-reported sleep-wake disturbances. Melatonin (6 mg), administered 2 hr before habitual bedtime, enhanced the rest-activity rhythm and improved sleep quality as observed in a reduction in sleep onset latency and in the number of transitions from sleep to wakefulness. However, total sleep time was not significantly increased nor was wake within sleep significantly reduced. The ability to remember previously learned items improved along with a significant reduction in depressed moods. No side effects or contraindications were reported by any of our participants during the 10 day trials. These data suggest that melatonin can safely improve some aspects of sleep, memory, and mood in the elderly in short-term use. 相似文献