全文获取类型
收费全文 | 45562篇 |
免费 | 2761篇 |
国内免费 | 259篇 |
专业分类
耳鼻咽喉 | 392篇 |
儿科学 | 1301篇 |
妇产科学 | 1215篇 |
基础医学 | 5966篇 |
口腔科学 | 960篇 |
临床医学 | 4529篇 |
内科学 | 9978篇 |
皮肤病学 | 898篇 |
神经病学 | 4872篇 |
特种医学 | 1520篇 |
外科学 | 6011篇 |
综合类 | 177篇 |
一般理论 | 19篇 |
预防医学 | 3367篇 |
眼科学 | 768篇 |
药学 | 2797篇 |
1篇 | |
中国医学 | 85篇 |
肿瘤学 | 3726篇 |
出版年
2024年 | 70篇 |
2023年 | 524篇 |
2022年 | 1007篇 |
2021年 | 1816篇 |
2020年 | 1059篇 |
2019年 | 1495篇 |
2018年 | 1706篇 |
2017年 | 1197篇 |
2016年 | 1344篇 |
2015年 | 1551篇 |
2014年 | 2132篇 |
2013年 | 2659篇 |
2012年 | 3936篇 |
2011年 | 3936篇 |
2010年 | 1993篇 |
2009年 | 1861篇 |
2008年 | 3135篇 |
2007年 | 3029篇 |
2006年 | 2724篇 |
2005年 | 2693篇 |
2004年 | 2263篇 |
2003年 | 2024篇 |
2002年 | 1783篇 |
2001年 | 240篇 |
2000年 | 183篇 |
1999年 | 248篇 |
1998年 | 305篇 |
1997年 | 227篇 |
1996年 | 201篇 |
1995年 | 182篇 |
1994年 | 156篇 |
1993年 | 130篇 |
1992年 | 95篇 |
1991年 | 94篇 |
1990年 | 80篇 |
1989年 | 51篇 |
1988年 | 50篇 |
1987年 | 46篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 43篇 |
1983年 | 25篇 |
1982年 | 43篇 |
1981年 | 25篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1975年 | 10篇 |
1972年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Cavalli E Mattasoglio A Pinciroli F Spaggiari P 《International journal of medical informatics》2004,73(3):297-303
In recent years, major and widely accepted information security understandings and achievements confirm that the problem is complex. They clarify that technologies are fundamental tools, but management processes have even bigger relevance, as also prestigious international magazines dossier clearly explained recently. Such a magazine attention outlines the wide impact that the subject has on watchful decision makers. ISO17799 is an emerging standard in information security. In principle there are no reasons for considering it not applicable to the health care sector. In practice, because of both the just conceptual level of the standard and the peculiarities of the health care data and institutions, a lot of analysis and design work need to be invested any time a health care institution decides to deal with the subject. CEN/ENV 12924 is another emerging standard certainly more on the spot of the health care. Nevertheless, it also asks for evident further investigation. The practical case of information security design, implementation, management, and auditing inside a multi-specialty provincial Italian hospital will be described. 相似文献
102.
Lipid abnormalities in HIV-infected patients are not correlated with lopinavir plasma concentrations
103.
Egger G Burda A Obernosterer A Mitterhammer H Kager G Jürgens G Hofer HP Fabjan JS Pilger E 《Inflammation》2001,25(2):129-135
The aim of the study was to demonstrate an activation of polymorpho-nuclear leukocytes (PMNs) in chronic progressive atherosclerosis (ATH). A group of patients with ATH, and a group of ATH patients under aspirin (ASA) therapy were compared with control persons without atherosclerotic alterations (healthy controls). Each group comprised 15 male age-matched subjects. The following inflammatory parameters related to PMN activities were measured: the polymorphonuclear leukocyte (PMN) blood count; blood PMN migration and reactive oxygen species release in vitro; the blood levels of PMN elastase, malondialdehyde, antibodies to oxidized LDL and soluble ICAM-1. In ATH patients, the PMN blood counts and the share of blood PMNs migrating upon platelet activating factor and leukotriene B4 stimulation were significnatly above the values of the healthy controls, while the other parameters were not significantly altered. ASA treatment attenuated the inflammatory response and reduced the differences between ATH and the healthy controls. It can be concluded that, in patients with chronic progressive atherosclerosis, PMNs are involved in the inflammatory process underlying the disease. 相似文献
104.
105.
It has been suggested that the cytoplasmic amino-terminal tail of invariant chain (Ii) contains a sorting signal that directs trafficking of the major histocompatibility complex (MHC) class II: Ii oligomeric complex to endocytic compartments. This model is based, in part, on the observation that in the absence of MHC class II molecules, Ii is detectable in lysosomal structures, a phenotype that is dependent on an intact NH2 terminus. However, the route by which Ii gains access to endosomal compartments in the absence of class II molecules remains uncertain. Here we report a mechanism that localizes Ii in lysosomal compartments independently of class II. We show that murine Ii can be detected by immunofluorescence within late endocytic compartments of stably transfected Ltk? mouse fibroblasts. Immunochemical studies indicate that degradation of Ii in these cells is sensitive to the lysosomotropic agent ammonium chloride, yet the majority of Ii that undergoes this apparent lysosomal degradation is sensitive to the enzyme endoglycosidase H. This finding suggests that Ii may reach the lysosomal compartment by a route that bypasses the Golgi complex. Consistent with this possibility, we found that in contrast to Ii which is complexed to class II molecules, transport of free Ii to lysosomes is prevented by 3-methyladenine, an inhibitor of the autophagic pathway of protein degradation, a process which involves direct transport from the endoplasmic reticulum to lysosomes. These data suggest the route of transport that leads to endosomal localization of Ii in the absence of class II is distinct from that taken when expressed with class II. This forces a re-evaluation of the concept that the cytosolic tail of Ii contains a dominant Golgi-to-endosomal sorting signal. 相似文献
106.
Taylor Rachel R.; Egan Andrea; McGuinness David; Jepson Annette; Adair Richard; Drakely Chris; Riley Eleanor 《International immunology》1996,8(6):905-915
Malaria infection induces the production of serum antibodiesto a variety of malaria antigens but the prevalence of antibodiesto any particular antigen ins typically mucb less than 100%.It has been assumed that non-responsiveness to defined antigensin malaria immune subjects is due to HLA mediated restricutionof the Immune response. In this study we have investigated therole of HLA and non-HLA genes in the antibody response to twomerozoite surface antigens (MSP1 and MSP2) and a sexual stageantigen (Pfs260/230) opf P{lasmodium falcpartum, and concludethat host genotype is not a major determinant of responsiveness.Although antibody levels vary in accordance with seasonal variationsin malaria transmission in semi-immune children, antibiody levelsremain stable in clncall immine adults. 相似文献
107.
Ricciardolo FL Caramori G Ito K Capelli A Brun P Abatangelo G Papi A Chung KF Adcock I Barnes PJ Donner CF Rossi A Di Stefano A 《The Journal of allergy and clinical immunology》2005,116(5):1028-1035
BACKGROUND: Reactive nitrogen species, formed via the reaction of nitric oxide (NO) with superoxide anion and via (myelo)peroxidase-dependent oxidation of NO(2)(-), have potent proinflammatory and oxidizing actions. Reactive nitrogen species formation and nitrosative stress are potentially involved in chronic obstructive pulmonary disease (COPD) pathogenesis. OBJECTIVES: To investigate the expression of markers of nitrosative stress, including nitrotyrosine (NT), inducible NO synthase (iNOS), endothelial NO synthase (eNOS), myeloperoxidase (MPO), and xanthine oxidase (XO) in bronchial biopsies and bronchoalveolar lavage from patients with mild to severe stable COPD compared with control groups (smokers with normal lung function and nonsmokers). METHODS: The expression of NT, iNOS, eNOS, MPO and XO in the bronchial mucosa and bronchoalveolar lavage of patients was measured by using immunohistochemistry, Western blotting, and ELISA and correlated with the inflammatory cell profile. RESULTS: Patients with severe COPD in stable phase had higher numbers of NT(+) and MPO(+) cells in their bronchial submucosa compared with mild/moderate COPD, smokers with normal lung function, and nonsmokers (P < .01). iNOS(+) and eNOS(+) but not XO(+) cells were significantly increased in smokers with COPD or normal lung function compared with nonsmokers (P < .05 and P < .01, respectively). In patients with COPD, the number of MPO(+) cells was significantly correlated with the number of neutrophils (r = +0.61; P < .0025) in the bronchial submucosa. Furthermore, the number of NT(+) and MPO(+) cells was negatively correlated with postbronchodilator FEV(1). CONCLUSION: These data suggest that nitrosative stress, mainly mediated by MPO and neutrophilic inflammation, may contribute to the pathogenesis of severe COPD. 相似文献
108.
Weren A Bonnekoh B Schraven B Gollnick H Ambach A 《Journal of immunological methods》2004,289(1-2):17-26
CD8(hi+) cytotoxic T lymphocytes (CTL) are major players in immune defense. In addition, they contribute to the maintenance of immune homeostasis. We now describe a hitherto unavailable, but simple assay to determine ex vivo lytic granule-based cytotoxic functions of human CD8(hi+) CTL subgroups in a clinical setting, under target cell free conditions. Ficoll-isolated peripheral blood lymphocytes from 17 healthy volunteers were stimulated either by phorbol 12-myristate 13-acetate (PMA) in combination with ionomycin or by antibody mediated crosslinking of the CD3 molecule on the T cell surface. Using perforin as a marker for lytic granules, the reduction of CTL granules over time intervals up to 120 min was quantified by FACScan flow cytometry. The kinetics of perforin reduction were compared to the kinetics of NA-CBZ-L-lysine-thiobenzyl ester hydrochloride (BLT)-esterase release and of CD63 upregulation. The reduction in the perforin(+) portion of CD8(hi+) CTLs was correlated inversely with BLT-esterase release and CD63 upregulation. At 30 and 120 min after PMA/ionomycin stimulation, 55 +/- 14% and 42 +/- 14%, respectively, of CD8(hi+) CTLs still stained perforin(+) (time point 0 min = 100%). Perforin-granule release induced by CD3-crosslinking occurred as fast within 30 min (55 +/- 17%), but over the 120 min time interval it was not as complete when compared to PMA/ionomycin-stimulated perforin-reduction. Thus, the combination of an established degranulation assay with the power of immuno flow cytometry allows one to investigate the cytotoxic capability of CTL-subtypes and the kinetics of perforin-granule release. In addition, the assay may prove useful in the elucidation of intracellular signaling cascades governing the perforin-granule release process. 相似文献
109.
Mammalian transforming growth factor beta1 activated after ingestion by Anopheles stephensi modulates mosquito immunity 下载免费PDF全文
Luckhart S Crampton AL Zamora R Lieber MJ Dos Santos PC Peterson TM Emmith N Lim J Wink DA Vodovotz Y 《Infection and immunity》2003,71(6):3000-3009
During the process of bloodfeeding by Anopheles stephensi, mammalian latent transforming growth factor beta1 (TGF-beta1) is ingested and activated rapidly in the mosquito midgut. Activation may involve heme and nitric oxide (NO), agents released in the midgut during blood digestion and catalysis of L-arginine oxidation by A. stephensi NO synthase (AsNOS). Active TGF-beta1 persists in the mosquito midgut to extended times postingestion and is recognized by mosquito cells as a cytokine. In a manner analogous to the regulation of vertebrate inducible NO synthase and malaria parasite (Plasmodium) infection in mammals by TGF-beta1, TGF-beta1 regulates AsNOS expression and Plasmodium development in A. stephensi. Together, these observations indicate that, through conserved immunological cross talk, mammalian and mosquito immune systems interface with each other to influence the cycle of Plasmodium development. 相似文献
110.
Martínez G Ropero C Funes A Flores E Blotta C Landa AI Gargiulo PA 《Physiology & behavior》2002,76(2):219-224
Effect of blocking N-methyl-D-aspartic acid (NMDA) and non-NMDA-glutamatergic receptors on performance in the plus-maze was studied in male rats bilaterally cannulated into the nucleus accumbens (Acc). Rats were divided into seven groups that received either 1 microl injections of saline, (+/-)2-amino-7-phosphonoheptanoic acid (AP-7, 0.2, 0.5, or 1 microg) or 2,3 dioxo-6-nitro-1,2,3,4,tetrahydrobenzo-(f)quinoxaline-7-sulphonamide disodium (NBQX, 0.2, 0.5, or 1 microg) 15 min before testing. Time spent in open arm, time per entry, end arrivals, open, closed, and total arm entries, relationship between open-, closed-, and total arm entries, rearing, face-, head-, and body grooming, and number of fecal boli were recorded. Time spent in the open arm increased under AP-7 (0.5 and 1 microg; P<.01) and NBQX (1 microg; P<.05) treatment, whereas time per entry was increased only with AP-7 (1 microg; P<.05). Open arm entries were increased by the intermediate doses of AP-7 (0.5 microg; P<.01) and NBQX (0.5 microg; P<.05); end arrivals were increased by the intermediate dose of AP-7 (0.5 microg/1 microl, P<.05). The frequency of rearing, grooming, and closed arm entries was not affected by the treatment. We conclude that NMDA and non-NMDA-glutamatergic blockade in the Acc lead to a behavioral disinhibition of cortical influences with the median doses, but that at higher doses the blockers have an anxiolytic-like effect. 相似文献