全文获取类型
收费全文 | 41346篇 |
免费 | 3387篇 |
国内免费 | 101篇 |
专业分类
耳鼻咽喉 | 452篇 |
儿科学 | 1226篇 |
妇产科学 | 1092篇 |
基础医学 | 6232篇 |
口腔科学 | 654篇 |
临床医学 | 5593篇 |
内科学 | 7348篇 |
皮肤病学 | 898篇 |
神经病学 | 4357篇 |
特种医学 | 985篇 |
外科学 | 3903篇 |
综合类 | 343篇 |
现状与发展 | 1篇 |
一般理论 | 35篇 |
预防医学 | 4617篇 |
眼科学 | 754篇 |
药学 | 2785篇 |
中国医学 | 53篇 |
肿瘤学 | 3506篇 |
出版年
2023年 | 277篇 |
2022年 | 406篇 |
2021年 | 979篇 |
2020年 | 669篇 |
2019年 | 1046篇 |
2018年 | 1219篇 |
2017年 | 959篇 |
2016年 | 1068篇 |
2015年 | 1115篇 |
2014年 | 1535篇 |
2013年 | 1972篇 |
2012年 | 3130篇 |
2011年 | 3159篇 |
2010年 | 1739篇 |
2009年 | 1585篇 |
2008年 | 2722篇 |
2007年 | 2819篇 |
2006年 | 2585篇 |
2005年 | 2673篇 |
2004年 | 2372篇 |
2003年 | 2220篇 |
2002年 | 2076篇 |
2001年 | 458篇 |
2000年 | 368篇 |
1999年 | 491篇 |
1998年 | 481篇 |
1997年 | 401篇 |
1996年 | 290篇 |
1995年 | 304篇 |
1994年 | 255篇 |
1993年 | 234篇 |
1992年 | 248篇 |
1991年 | 267篇 |
1990年 | 244篇 |
1989年 | 235篇 |
1988年 | 228篇 |
1987年 | 181篇 |
1986年 | 156篇 |
1985年 | 156篇 |
1984年 | 170篇 |
1983年 | 114篇 |
1982年 | 107篇 |
1981年 | 118篇 |
1980年 | 98篇 |
1979年 | 105篇 |
1978年 | 78篇 |
1977年 | 83篇 |
1976年 | 76篇 |
1975年 | 72篇 |
1974年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
201.
Changing smoking, drinking, and eating behaviour among pregnant women in Denmark. Evaluation of a health campaign in a local region 总被引:1,自引:0,他引:1
J Olsen G Frische A O Poulsen H Kirchheiner 《Scandinavian journal of social medicine》1989,17(4):277-280
Health behaviour during pregnancy was examined before and after a comprehensive health campaign targeted at pregnant women in Odense, Denmark. Furthermore, lifestyle habits were compared before and during the campaign with similar habits in Aalborg, Denmark. All 13,815 pregnant women (equal numbers from each city) were enrolled in the study, and 11,980 gave information on eating, drinking, and smoking habits during pregnancy. Data collection in both cities took place from April 1984 to April 1987. The campaign, which was entitled "Healthy Habits for Two", ran from April 1985 to April 1987 in the city of Odense only. No significant change in health behaviour in the Odense area was noted after the start of the campaign. 相似文献
202.
Summary Rat-liver microsomes and NADPH could reduce Adriamycin, epirubicin and daunorubicin to their free radical forms, which enhanced peroxidation of microsomal lipids less than 2-fold in air but 3- to 5-fold at a pO2 of 4 mm Hg. Mitoxantrone was not reduced by microsomes and had no effect on microsomal peroxidation. Daunorubicin caused more lipid peroxidation than similar concentrations of either Adriamycin or epirubicin, which were equally efficient. In each case peroxidation was iron-dependent and could be catalysed by ferritin. The antioxidants -carotene and -tocopherol inhibited lipid peroxidation at low or high pO2. The dose-for-dose difference in the cardiotoxicity of epirubicin compared with Adriamycin is not explained by its effect on microsomal lipid peroxidation. However, the lower incidence of cardiotoxicity with mitoxantrone may be a consequence of its inability to form free radical species and promote lipid peroxidation. 相似文献
203.
Localization of SNARE proteins and secretory organelle proteins in astrocytes in vitro and in situ 总被引:1,自引:0,他引:1
Wilhelm A Volknandt W Langer D Nolte C Kettenmann H Zimmermann H 《Neuroscience research》2004,48(3):249-257
Astrocytes are capable of regulated release of messenger molecules. Astrocytes cultured from new born rodent brain express a variety of classical presynaptic proteins. We investigated the question whether the capability to express synaptic proteins in culture was a feature only of immature astrocytes, and whether these proteins were also expressed by astrocytes in situ. Experiments were performed with transgenic mice expressing the enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Using double fluorescence and astrocytes cultured from 1 to 16 day-old animals we show that the astrocytic expression of synaptic proteins in culture is invariant of the age of donor animals. Culturing can induce the astrocytic expression of specific synaptic proteins such as SV2, synaptophysin and SNAP-25. Astrocytes in brain sections of 1-16 day-old animals revealed a punctuate immunofluorescence for secretory carrier membrane protein (SCAMP), SNAP-23, synaptobrevin II, and cellubrevin, to a minor extent for SNAP-25 and synaptophysin, and none for SV2. Our results demonstrate that cultured astrocytes express synaptic proteins not present in situ. Nevertheless, astrocytic organelles in situ are equipped with molecules that could be involved in regulated exocytosis of messenger substances. 相似文献
204.
Macrophage response to peripheral nerve injury: the quantitative contribution of resident and hematogenous macrophages 总被引:6,自引:0,他引:6
Mueller M Leonhard C Wacker K Ringelstein EB Okabe M Hickey WF Kiefer R 《Laboratory investigation; a journal of technical methods and pathology》2003,83(2):175-185
Whereas local microglial cells of the CNS rapidly respond to injury, little is known about the functional role of resident macrophages of the peripheral nervous system in nerve pathology. Using bone marrow chimeric rats, we recently identified individual resident endoneurial macrophages that rapidly became activated after nerve injury. However, the extent of local macrophage activation and its quantitative contribution to the total macrophage response is unknown. We now have created chimeric mice by transplanting bone marrow from green fluorescent protein (GFP)-transgenic mice into irradiated wild-type mice, allowing easy differentiation and quantification of hematogenous and resident endoneurial macrophages. After sciatic nerve crush injury, both GFP(-) and GFP(+) resident macrophages, the latter having undergone physiological turnover from the blood before injury, rapidly underwent morphological alterations and increased in number. Proliferating GFP(-) and GFP(+) resident macrophages were abundant and peaked 3 days after injury. A major lesion-induced influx of hematogenous macrophages with a disproportionate increase of GFP(+) macrophages was not observed until Day 4. Throughout all time points examined, GFP(-) resident macrophages were strikingly frequent, reaching maximum numbers 9.5-fold above baseline. There was also a notable proportion of GFP(-) resident endoneurial macrophages phagocytosing myelin and expressing major histocompatibility complex class II. Our results demonstrate for the first time that the rapid response of resident endoneurial macrophages to nerve injury is quantitatively important and that local macrophages contribute significantly to the total endoneurial macrophage pool during Wallerian degeneration. 相似文献
205.
Olsen LH Mortensen K Martinussen T Larsson LI Baandrup U Pedersen HD 《Journal of comparative pathology》2003,129(2-3):120-130
Comparable pathological changes in the mitral valve have been described in dogs, pigs and human patients with myxomatous mitral valve disease (MMVD), i.e., primary mitral valve prolapse. The progressive myxomatous changes are probably a response to repeated impact on the leaflets, and endothelial stress or damage probably plays a central role in the pathogenesis. Little, however, is known about the vasoactive substances that mediate the subendothelial changes. The aim of this study was to investigate the expression of nitric oxide synthase (NOS) in canine mitral valve leaflets and to relate the findings to MMVD changes. The mitral valve was taken post mortem from 12 dogs (six males and six females) and a whole valve NADPH (the reduced form of nicotinamide-adenine dinucleotide phosphate) diaphorase (NADPH-d) reaction was performed. Macroscopical (semiquantitative) and microscopical (computer image analysis) evaluations of the staining due to NADPH-d activity were performed at four specific areas of the valve and related to microscopical signs of MMVD and gross signs of thickening or prolapse, or both. Macroscopically, the NADPH-d colour grade was correlated with the degree of MMVD (P=0.01). In addition, endothelial NADPH-d staining intensity was correlated with macroscopical signs of disease (P=0.004) as well as with collagen degeneration (P=0.008) and deposition of mucopolysaccharides (P=0.02). Age, gender and specific area of the valve did not seem to influence the NADPH-d activity. In conclusion, increased NADPH-d activity, suggesting increased NOS expression, was found in areas of the mitral valve with myxomatous changes. This indicates that nitric oxide (NO) may play a role in the pathogenesis of MMVD in dogs. 相似文献
206.
207.
Since previous studies showed that calcium uptake by synaptosomes from rodents declines with aging [30], the subsynaptosomal distribution of calcium was determined with the disruption method of Scott et al. [37]. Calcium uptake by the mitochondrial (digitonin-resistant) and non-mitochondrial (digitonin-labile) compartments, as well as total uptake, were determined at 2, 5 and 10 min. After a 10 min incubation under resting conditions (5 mM-KCl), total calcium uptake decreased at 10 months (−14.6%) and 30 months (−33.0%) of age; mitochondrial calcium uptake increased by 10 months (+11.2%) but declined by 30 months (−17.5%); the nonmitochondrial calcium compartment declined at 10 (−34.7%) and 30 (−43.4%) months when compared to the 3 month old control. With potassium depolarization (31 mM-KCl), total calcium uptake declined from 100% (3 months) to 73.8% (10 months) or 53.0% (30 months); mitochondrial calcium uptake declined from 100% (3 months) to 85.6% (10 months) or 68.4% (30 months); non-mitochondrial calcium uptake decreased at 10 (−34.3%) and 30 (−57.7%) months of age when compared to 3 months (100%). The deficits in calcium homeostasis are not due to changes in synaptosomal volumes or to diminished membrane potentials, as assessed by tetraphenylphosphonium ion accumulation. 3,4-Diaminopyridine partially reversed the alterations in total, mitochondrial and non-mitochondrial calcium uptake by synaptosomes from aged mice. 相似文献
208.
Michael Schirner Frank Herzberg Roland Schmidt Michael Streit Michael Schoning Michael Hummel Christine Kaufmann Eckhard Thiel Ernst-Dieter Kreuser 《Clinical & experimental metastasis》1997,16(5):427-435
The integrin 51 seems to be the most relevant receptor of tumor cells for binding to fibronectin. Although numerous studies suggest a role of tumor cell fibronectin interaction in tumor metastasis, differential integrin expression on tumor cells has, however, not been correlated with metastatic capabilities. We addressed this question by transfection of the integrin 51 cDNA into HT-29 human colon carcinoma cells which led to de novo expression of functional integrin 51. Similar to other reports, expression of the integrin 51 in HT-29 tumor cells exerted an inhibitory action on cell proliferation as indicated in our study by formation of fewer colonies in soft agar. The tumor growth inhibitory property of the integrin 51 was also shown by reduction of subcutaneous xenograft growth in nude mice to approximately 50% of that of control transfectants. For the first time, we found that several clones of integrin 5 subunit transfectants displayed dramatically reduced formation of lung colonies and cutaneous metastasis after intravenous injec-tion into nude mice. While most animals inoculated with control transfectant cells formed macroscopically visible lung colonies ranging from 12.6 ± 2.6 to 22.0 ± 6.6 (mean colony number ± SEM), mice inoculated with HT-29 cell clones expressing the integrin a5b1 were almost completely free of lung colonies (ranging from 0.0 ± 0 to 0.2 ± 0.1). Our results imply that integrin 51 expression inhibits circulating tumor cells in pursuing late steps of the metastatic process as represented by the artificial metastasis (lung colonisation) model. © Rapid Science Ltd. 相似文献
209.
It has been suggested that spectroscopic analysis of the aqueous humor of the eye could be used to indirectly predict blood glucose levels in diabetics noninvasively. We have been investigating this potential using Raman spectroscopy in combination with partial least squares (PLS) analysis. We have determined that glucose at clinically relevant concentrations can be accurately predicted in human aqueous humor in vitro using a PLS model based on artificial aqueous humor. We have further determined that with proper instrument design, the light energy necessary to achieve clinically acceptable prediction of glucose does not damage the retinas of rabbits and can be delivered at powers below internationally acceptable safety limits. Herein we summarize our current results and address our strategies to improve instrument design. 相似文献
210.
Djarmati A Hedrich K Svetel M Schäfer N Juric V Vukosavic S Hering R Riess O Romac S Klein C Kostic V 《Human mutation》2004,23(5):525
Mutations in the Parkin (PARK2) and the DJ1 (PARK7) gene cause early-onset Parkinson disease (EOPD). We tested 75 Serbian EOPD patients for mutations in both genes by conventional mutational screening (SSCP/dHPLC/sequencing) to detect small sequence alterations and by gene dosage studies (quantitative PCR) to reveal deletions or multiplications of one or more exons. A compound heterozygous Parkin mutation (exon deletion and point mutation; [c.836_972del]+[c.1411C>T]; +1 is first nucleotide of GenBank AB009973.1) was identified in a patient who showed a relatively benign course after a disease onset at 41 years. Another case had a heterozygous exon deletion in DJ1 ([c.253_322del]+[?]) and presented with an age at onset of 45 years and a rapid disease course. In conclusion, Parkin mutations are surprisingly rare in our Serbian EOPD sample, suggesting that the mutation rate depends on the ethnic origin of the patients. Although DJ1 mutations appear to be rare, we confirm their role in EOPD and demonstrate the importance of gene dosage studies. 相似文献