全文获取类型
收费全文 | 5015篇 |
免费 | 438篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 30篇 |
儿科学 | 163篇 |
妇产科学 | 108篇 |
基础医学 | 651篇 |
口腔科学 | 67篇 |
临床医学 | 586篇 |
内科学 | 921篇 |
皮肤病学 | 54篇 |
神经病学 | 461篇 |
特种医学 | 239篇 |
外科学 | 726篇 |
综合类 | 101篇 |
一般理论 | 4篇 |
预防医学 | 594篇 |
眼科学 | 71篇 |
药学 | 361篇 |
中国医学 | 4篇 |
肿瘤学 | 321篇 |
出版年
2021年 | 57篇 |
2020年 | 51篇 |
2019年 | 51篇 |
2018年 | 65篇 |
2017年 | 78篇 |
2016年 | 57篇 |
2015年 | 91篇 |
2014年 | 136篇 |
2013年 | 186篇 |
2012年 | 222篇 |
2011年 | 225篇 |
2010年 | 172篇 |
2009年 | 130篇 |
2008年 | 200篇 |
2007年 | 231篇 |
2006年 | 199篇 |
2005年 | 199篇 |
2004年 | 224篇 |
2003年 | 216篇 |
2002年 | 225篇 |
2001年 | 208篇 |
2000年 | 202篇 |
1999年 | 141篇 |
1998年 | 46篇 |
1997年 | 55篇 |
1996年 | 40篇 |
1995年 | 56篇 |
1994年 | 42篇 |
1993年 | 58篇 |
1992年 | 96篇 |
1991年 | 116篇 |
1990年 | 115篇 |
1989年 | 108篇 |
1988年 | 100篇 |
1987年 | 90篇 |
1986年 | 90篇 |
1985年 | 84篇 |
1984年 | 64篇 |
1983年 | 66篇 |
1982年 | 41篇 |
1980年 | 28篇 |
1979年 | 57篇 |
1978年 | 49篇 |
1977年 | 30篇 |
1975年 | 33篇 |
1974年 | 34篇 |
1973年 | 30篇 |
1972年 | 35篇 |
1971年 | 28篇 |
1970年 | 30篇 |
排序方式: 共有5462条查询结果,搜索用时 15 毫秒
61.
SUMMARY Ponto-geniculo-occipital (PGO) waves are spontaneously-occurring macropotential waveforms recorded in the pons, lateral geniculate body (LGB) and occipital cortex. PGO waves mark the onset and course of rapid eye movement sleep (REM). PGO-like waves can be recorded in several brain areas including the thalamic central lateral nucleus (CL). Alerting stimuli elicit PGO waves (PGOE ) from LGB and waves from CL (CLE ) in all behavioural states. We compared spontaneous activity in LGB and CL across behavioral states to examine the relationship of CL waves to PGO waves. Spontaneous waves in LGB and CL may occur concurrently or separately in all states. Although REM is marked by a high level of LGB PGO activity, CL waves are rare. Frequencies of CL and LGB waves are similar in non-REM (NREM) although the waves do not necessarily occur at the same time. These findings suggest that the widespread phasic activity recorded throughout the brain in sleep cannot be assumed to be a non-specific unitary phenomenon propagated from a single brainstem generator. 相似文献
62.
63.
Allen LA Achermann JC Pakarinen P Kotlar TJ Huhtaniemi IT Jameson JL Cheetham TD Ball SG 《Human reproduction (Oxford, England)》2003,18(2):251-256
BACKGROUND: Inactivating mutations of the FSH receptor (FSHR) are a rare cause of hypergonadotrophic hypogonadism in women. Only one patient with primary amenorrhoea due to an FSHR gene mutation has been reported outside of Finland, where the prevalence of Ala189Val mutations is particularly high. METHODS AND RESULTS: Here, we describe the clinical, molecular genetic and functional characteristics associated with a novel inactivating mutation in exon 10 of the FSHR gene identified in a patient who presented with primary amenorrhoea at 17 years of age. The C to G transversion found at nucleotide 1043 causes a Pro348Arg substitution in the extracellular region of the FSHR and results in a mutant FSHR that is completely inactive in functional studies and that does not bind FSH. The proband exhibits apparent homozygosity for this recessive mutation. Her father is heterozygous for the mutation while analysis of exon 10 of the FSHR gene from her mother revealed only wild-type sequence. Chromosome painting was used to exclude deletions or rearrangements of 2p, and microsatellite markers did not show paternal uniparental isodisomy for this region. These findings suggest that the proband is hemizygous, with an inherited or de-novo microdeletion, or alternatively a de-novo gene conversion, of the accompanying FSHR allele. CONCLUSIONS: This case confirms the importance of the FSHR in female pubertal development and reproduction, and supports a relationship between phenotype and function for FSHR mutations. 相似文献
64.
Dawson EA Shave R George K Whyte G Ball D Gaze D Collinson P 《European journal of applied physiology》2005,94(3):305-309
This study examined whether, in 16 male subjects, a continuous increase in heart rate (HR) during 4 h of ergometry cycling relates to cardiac fatigue or cardiomyocyte damage. Serum cardiac troponin T (cTnT) was determined and echocardiographic assessment was carried out prior to and after 2 h of exercise, within 15 min of completing exercise and after 24 h. Left ventricular contractile function (end-systolic blood pressure–volume relationship [SBP/ESV]) and diastolic filling (ratio of early to late peak left ventricular filling velocities [E:A]) were calculated. During exercise HR was 132±5 beats min–1 after 2 h and increased to 141±5 beats min–1 (mean ± SD; P<0.05), but there was no evidence of altered LV contractile function (SBP/ESV 39.0±5.1 mmHg cm–1 to 36.5±5.2 mmHg cm–1 and SBP/ESV was not correlated to maximal oxygen uptake (r2=0.363). In contrast, E:A decreased (1.82±0.32 to 1.48±0.30; P<0.05) and returned towards baseline after 24 h (1.78±0.28), and individual changes were correlated to maximal oxygen uptake (r2=0.61; P<0.05). Low levels of cTnT were detected in two subjects after 4 h of exercise that had normalised by 24 h of recovery. During prolonged exercise cardiovascular drift occurred with echocardiographic signs of a reduced diastolic function of the heart, especially in those subjects with a high maximal oxygen uptake. 相似文献
65.
W. Kong Chan Margaret M. Mole David A. Levison Richard Y Ball Qi-Long Lu Kirtika Patel Andrew M. Hanby 《The Journal of pathology》1995,177(3):241-246
The bcl-2 proto-oncogene, which inhibits programmed cell death (apoptosis), has recently been found to be cyclically expressed in human endometrium. In order to investigate its role in endometrial hyperlasia and neoplasia, bcl-2 expression was studied in 25 cases of endometrial carcinoma and 20 cases of endometrial hyperplasia (eight simple, two complex, and ten atypical hyperplasias). Uniform intense cytoplasmic bcl-2 expression was found in all cases of non-atypical hyperplasia, and less strong positivity in eight out of ten cases of atypical hyperplasia. In well-differentiated carcinomas, nine out of ten showed weak to moderate bcl-2 expression, whereas six out of seven poorly differentiated carcinomas were bcl-2-negative. Moderately differentiated tumours were an intermediate group, with six out of eight being positive. Widespread localization of bcl-2 protein to the chromosomes of dividing cells was also demonstrated, regardless of cytoplasmic bcl-2 expression, with rare staining of interphase nuclei. Our findings suggest a role for bcl-2 in the natural history of endometrial neoplasia and studies are needed to determine its usefulness as a prognostic marker. The finding of bcl-2 localization to chromosomes has important implications for its mode and site of action. 相似文献
66.
The insect nodavirus Flock house virus (FHV) has a small genome divided between two segments of positive-sense RNA, RNA1 and RNA2. RNA1 encodes the RNA-dependent RNA polymerase (RdRp) catalytic subunit and templates the synthesis of a subgenomic RNA (RNA3) that encodes two small nonstructural proteins. Replication of RNA2, which encodes a precursor to the viral capsid proteins, suppresses RNA3 synthesis. Here we report that RNA1 mutants deficient in RNA3 synthesis failed to support RNA2 replication. This effect was not caused by alterations in the RdRp catalytic subunit nor by a lack of the proteins encoded by RNA3. Furthermore, RNA3 supplied in trans from an exogenous source restored RNA2 replication. These data indicate that RNA3 transactivates the replication of RNA2, a novel property for a viral RNA. We propose that the RNA3 dependence of RNA2 replication serves to coordinate replication of the FHV genome segments. 相似文献
67.
Ball SA Nich C Rounsaville BJ Eagan D Carroll KM 《Journal of consulting and clinical psychology》2004,72(4):698-711
The concurrent and predictive validity of 2 different methods of Millon Clinical Multiaxial Inventory-III subtyping (protocol sorting, cluster analysis) was evaluated in 125 recently detoxified opioid-dependent outpatients in a 12-week randomized clinical trial. Participants received naltrexone and relapse prevention group counseling and were assigned to 1 of 3 intervention conditions: (a) no-incentive vouchers, (b) incentive vouchers alone, or (c) incentive vouchers plus relationship counseling. Affective disturbance was the most common Axis I protocol-sorted subtype (66%), antisocial-narcissistic was the most common Axis II subtype (46%), and cluster analysis suggested that a 2-cluster solution (high vs. low psychiatric severity) was optimal. Predictive validity analyses indicated less symptom improvement for the higher problem subtypes, and patient treatment matching analyses indicated that some subtypes had better outcomes in the no-incentive voucher conditions. 相似文献
68.
Nitric oxide, synthesized by reactive microglia and astrocytes has been implicated in promoting neuronal degeneration observed in many diseases and insults of the central nervous system. We have recently shown that inducible nitric oxide synthase is expressed by retinal glial cells following optic nerve transection and that inhibition of nitric oxide synthesis enhances the survival of injured retinal ganglion cells. Anti-inflammatory cytokines including interleukin-10 (IL-10), interleukin-4 (IL-4), and transforming growth factor-beta (TGF-beta) have been shown to prevent inducible nitric oxide synthase expression, and inhibit nitric oxide synthesis by microglia and astrocytes in culture. In the present study, we examined the effects of adenoviral mediated gene transfer of anti-inflammatory cytokines on the survival of axotomized retinal ganglion cells. Intraocular administration of adenoviral vectors encoding interleukin-10 (Ad.IL-10) and interleukin-4 (Ad.IL-4) enhanced the survival of axotomized retinal ganglion cells at 14 days after axotomy. Adenoviral vectors encoding TGF-beta (Ad.TGF-beta) had no effect on retinal ganglion cell survival. Separate animals were pretreated by injection of Ad.IL-10 or Ad.IL-4 into the superior colliculus (s.c.), the major target of ganglion cells, 7 days prior to axotomy. S.c. administration of Ad.IL-10 or Ad.IL-4 significantly increased ganglion cell survival compared with intraocular injection. IL-10 and IL-4 gene transfer also reduced the density of infiltrating ED1 positive monocytes in the nerve fiber layer at 14 days postaxotomy. Ad.TGF-beta increased the density of ED1 positive monocytes infiltrating the nerve fiber layer after axotomy. Vectors encoding IL-10 or IL-4 also decreased nitrotyrosine immunoreactivity in the inner retina at 7 days postaxotomy, suggesting that these cytokines protect retinal ganglion cells from peroxynitrite formation that results from nitric oxide synthesis by activated glial cells. The present study has implications for the treatment of CNS injury and diseases that involve reactive microglia and astrocytes. Our results suggest that interleukin-10 and interleukin-4 may help prevent neurodegeneration caused by the activation of glial cells after CNS injury. 相似文献
69.
Restricted usage of VH and V kappa genes by murine monoclonal antibodies against 3-fucosyllactosamine 总被引:4,自引:0,他引:4
We are studying the structure and regulation of murine antibodies against the 3-fucosyllactosamine antigenic determinant. Analysis of the sequences of seven BALB/c IgM, kappa monoclonal antibodies (mAb), obtained from four fusions, indicates that these antibodies exhibit restriction in their usage of VH and VL genes. Based on a combination of mRNA sequences and Southern filter hybridization data, all seven light chains are encoded by V kappa 24B and J kappa 1 gene segments. Complete mRNA sequences of the heavy chains revealed that all seven mAb are encoded by VH441, six antibodies are encoded by JH4 and one uses a JH3 gene segment. The VH441 gene segment and all seven mAb contain a potential glycosylation site at Asn 58 in complementarity-determining region (CDR)2. In contrast to the similarity of the VH regions, the heavy chain CDR3 segments exhibit considerable heterogeneity. They are encoded by three D segments, they vary in length from 7-9 amino acids and display differences in their deduced amino acid sequences. The VH441 gene segment also encodes antibodies against four other carbohydrate antigens, levan, galactan, dextran and galactosyl globoside. The use of a single gene segment to encode antibodies against five different antigens suggests that the domain encoded by VH441 might be particularly well adapted for forming sites that bind carbohydrate determinants. Glycosylation of CDR2 might contribute to the unique properties of this VH domain. 相似文献
70.