全文获取类型
收费全文 | 106888篇 |
免费 | 7567篇 |
国内免费 | 202篇 |
专业分类
耳鼻咽喉 | 1223篇 |
儿科学 | 3004篇 |
妇产科学 | 2562篇 |
基础医学 | 16785篇 |
口腔科学 | 3112篇 |
临床医学 | 9826篇 |
内科学 | 22005篇 |
皮肤病学 | 1757篇 |
神经病学 | 10004篇 |
特种医学 | 4329篇 |
外国民族医学 | 55篇 |
外科学 | 14089篇 |
综合类 | 669篇 |
现状与发展 | 1篇 |
一般理论 | 129篇 |
预防医学 | 9381篇 |
眼科学 | 1872篇 |
药学 | 6737篇 |
中国医学 | 205篇 |
肿瘤学 | 6912篇 |
出版年
2022年 | 786篇 |
2021年 | 1639篇 |
2020年 | 1110篇 |
2019年 | 1620篇 |
2018年 | 1929篇 |
2017年 | 1508篇 |
2016年 | 1773篇 |
2015年 | 1988篇 |
2014年 | 2552篇 |
2013年 | 3902篇 |
2012年 | 5467篇 |
2011年 | 5563篇 |
2010年 | 3580篇 |
2009年 | 3280篇 |
2008年 | 4961篇 |
2007年 | 5170篇 |
2006年 | 5128篇 |
2005年 | 4850篇 |
2004年 | 4659篇 |
2003年 | 4353篇 |
2002年 | 4127篇 |
2001年 | 3624篇 |
2000年 | 3629篇 |
1999年 | 3294篇 |
1998年 | 1393篇 |
1997年 | 1209篇 |
1996年 | 1123篇 |
1995年 | 1037篇 |
1994年 | 916篇 |
1993年 | 949篇 |
1992年 | 2367篇 |
1991年 | 2240篇 |
1990年 | 2141篇 |
1989年 | 2064篇 |
1988年 | 1797篇 |
1987年 | 1693篇 |
1986年 | 1638篇 |
1985年 | 1505篇 |
1984年 | 1091篇 |
1983年 | 956篇 |
1982年 | 632篇 |
1981年 | 612篇 |
1980年 | 524篇 |
1979年 | 923篇 |
1978年 | 536篇 |
1977年 | 516篇 |
1975年 | 537篇 |
1974年 | 578篇 |
1973年 | 522篇 |
1972年 | 523篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Genotyping of clinical methicillin-susceptible Staphylococcus aureus isolates in a Dutch teaching hospital
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)
Van Dijk Y Wielders CL Fluit AC Paauw A Diepersloot RJ Mascini EM 《Journal of clinical microbiology》2002,40(2):663-665
Methicillin-susceptible Staphylococcus aureus isolates, recovered from 204 patients in our hospital in a 22-month period, were characterized by pulsed-field gel electrophoresis. Among the multiple S. aureus types six clonal lineages dominated, comprising isolates from 158 patients. Despite the limited genetic variation, cross-transmission was made plausible only sporadically. 相似文献
992.
Development, evaluation, and validation of an oligonucleotide probe hybridization assay to subtype human immunodeficiency virus type 1 circulating recombinant form CRF02_AG
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)
993.
Angiopoietin-1 causes reversible degradation of the portal microcirculation in mice: implications for treatment of liver disease
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ward NL Haninec AL Van Slyke P Sled JG Sturk C Henkelman RM Wanless IR Dumont DJ 《The American journal of pathology》2004,165(3):889-899
In many different liver diseases, such as cirrhosis, degradation of the microcirculation, including obliteration of small portal or hepatic veins contributes to disease-associated portal hypertension. The present study demonstrates the importance of angiogenesis in the establishment of arteriovenous shunts and the accompanying changes to the venous bed. One aspect of angiogenesis involves the branching of new vessels from pre-existing ones, and the molecular mechanisms controlling it are complex and involve a coordinated effort between specific endothelial growth factors and their receptors, including the angiopoietins. We modulated the hepatic vasculature in mice by conditionally expressing angiopoietin-1 in hepatocytes. In mice exposed to angiopoietin-1 during development, arterial sprouting, enlarged arteries, marked loss of portal vein radicles, hepatic vein dilation, and suggestion of arteriovenous shunting were observed. Most importantly, these phenotypic changes were completely reversed within 14 days of turning off transgene expression. Expression of excess angiopoietin-1 beginning in adulthood did not fully recapitulate the phenotype, but did result in enlarged vessels. Our findings suggest that controlling excessive angiogenesis during liver disease may promote the restoration of the portal vein circuit and aid in the resolution of disease-associated portal hypertension. 相似文献
994.
The efficacy of live reovirus vaccines may be determined by challenge via the foot pad route 3 to 4 weeks after vaccination. Swelling and discoloration in the foot pad and shank are scored for a period of 14 days. The major disadvantages of this challenge model are the subjective judgement of gross foot pad and/or shank lesions, that it is very difficult to induce lesions in broilers, and that it causes animal suffering. Other reovirus challenge models are based on reisolation of the virus from different tissues or on scoring microscopic lesions in the tendons. Some disadvantages of these models are that they either cannot be used after vaccination with live reovirus because they cannot discriminate between vaccine and challenge virus or that the microscopic lesions scored need not necessarily be related to the challenge virus but may have been induced by other factors. Therefore, we have attempted to develop a reovirus challenge model that was an improvement on the existing ones, using isolation of reovirus from different organs followed by specific detection of the challenge virus with a monoclonal antibody that can discriminate between challenge and vaccine virus. The reovirus challenge model was examined in specific pathogen free (SPF) White Leghorn chickens and commercial broilers. In vivo studies were conducted to examine the efficacy of an attenuated reovirus vaccine in SPF White Leghorn chickens and commercial broilers with maternal immunity against reovirus. No challenge virus could be detected in any of the organs of the vaccinated chickens 3 and 10 days after challenge. In contrast, challenge virus could be isolated from the unvaccinated control group. At an increased challenge dose all unvaccinated challenge control birds were positive, while the vaccinated chickens were protected. It was shown that 1-day-old vaccination in the presence of maternal immunity was effective. It seemed that protection induced in broilers by the attenuated reovirus vaccine may not have been entirely humoral because in protected birds no antibodies against reovirus were detected by enzyme-linked immunosorbent at the time of challenge. Protection in these birds might therefore have been induced by cellular immunity. 相似文献
995.
Loidl CF Gavilanes AW Van Dijk EH Vreuls W Blokland A Vles JS Steinbusch HW Blanco CE 《Physiology & behavior》2000,68(3):263-269
Previous studies in rats have demonstrated that perinatal asphyxia (PA) produces long-term morphological alterations, particularly affecting hippocampus. neostriatum, and cerebral cortex. These changes were prevented by applying hypothermia during the asphyctic insult. Because these cerebral areas are involved in cognitive and motor functions, the aim of the present study was to determine whether periods of PA during normothermia or hypothermia produces long-term behavioral impairments in rats of both sexes. The cognitive and motor functions were studied using the spatial Morris water maze (MWM) task at 1.5 months, and the open field at 5 months, respectively. The present study revealed that female rats had a higher survival rate than males after PA in normothermic conditions (p < 0.014). and that hypothermia drastically prolonged the time of survival in both sexes (p < 0.001). There were no differences in learning and memory functions between groups or male and female rats when tested with MWM. Rats subjected to hypothermia treatment did not show differences in the MWM compared to controls. A lower locomotor activity in the open field test was only observed in male rats that suffered 15 and 20 min of PA in normothermia (p < 0.05). Hypothermia treatment prevented this hypoactivity. PA in females, even if severe, did not affect the motor activity. The data of both behavioral tests showed differences between sexes, i.e., the female rats learned the MWM task slower, and were more active in the open field. This work lends further support for the hypothesis that hypothermia can prevent mortality as well as long-term sequelae induced by PA. 相似文献
996.
H. S. Tan H. Collewijn J. Van der Steen 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1992,90(3):456-468
Summary 1. In the alert, pigmented rabbit, eye movements were recorded during optokinetic nystagmus (OKN) and during optokinetic afternystagmus (OKAN). These responses were elicited by steps in surround-velocity ranging from 5–110°/s during binocular as well as monocular viewing. 2. In the baseline condition, OKN showed an approximately linear build-up of eye velocity to a steady-state, followed by a linear decay of eye velocity during OKAN after the lights were turned off. Build-up during binocular viewing was characterized by a constant, maximum eye-acceleration (about 1°/s2) for stimulus velocities up to 60°/s. OKAN, instead, was characterized by a fixed duration (about 10 s) for stimulus velocities up to 20°/s. Steady-state eye velocity saturated at about 50°/s. 3. Monocular stimulation in the preferred (nasal) direction elicited a build-up that was on average twice as slow as during binocular stimulation. Steady-state velocity during monocular stimulation saturated at about 20°/s. OKAN was of equal duration as during binocular stimulation. In the non-preferred direction, a very irregular nystagmus was elicited without velocity build-up. The stronger response to binocular stimulation, compared to the responses under monocular viewing condition in either nasal and temporal direction suggests potentiation of the signals of either eye during binocular viewing. 4. OKN and OKAN were re-assessed after intra-floccular microinjection of the nonselective cholinergic agonist carbachol. In the binocular viewing condition, eye-acceleration during build-up was strongly enhanced from 1°/s2 before to 2.5°/s2 after injection. The saturation level of steady-state eye velocity was also increased, from 50°/s before to more than 60°/s after carbachol. The duration of OKAN, however, was shortened from 10 s before to 6 s after injection. The response to monocular stimulation in the preferred direction revealed similar changes. 5. The flocculus appears to be involved in the control of the dynamics of OKN in the rabbit. Cholinergic mechanisms affect the floccular control of the rate at which slow-phase velocity can be built up and the rate of decay of eye velocity during OKAN. Cholinergic stimulation of the flocculus enhances the dynamics of OKN, while velocity storage is shortened. 相似文献
997.
The process of recruitment of leukocytes at sites of inflammation involves direct cell-to-cell interactions between leukocytes and vascular endothelial cells (EC) mediated by various adhesion receptors on leukocytes and their inducible endothelial ligands. In this study we have examined the induction on EC of endothelial leukocyte adhesion molecule-1 (ELAM-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) upon their interaction with subpopulations of human T cells. When co-cultured with EC both resting CD4+ T and CD8+ T cells caused a modest increase in the expression of endothelial ICAM-1. Moreover, resting CD4+ but not CD8+ T cells induced expression of ELAM-1 and VCAM-1 on a small fraction of unstimulated EC. Prior activation with phorbol 12-myristate 13-acetate (PMA) significantly increased the ability of T cells to up-regulate endothelial ICAM-1 and also induced the expression of both ELAM-1 and VCAM-1. PMA-primed CD4+ T cells induced both VCAM-1 and ELAM-1 on EC more efficiently than CD8+ T cells. Furthermore, the ability to induce the expression of ELAM-1 and VCAM-1 was confined to the CD4+ CD45R0+ memory/primed subpopulation of T cells. This induction of various endothelial adhesion ligands could also be mediated by antigen-primed CD4+ T cell lines. The CD4+ T cell-mediated induction of adhesion ligands required direct intercellular contact with EC because neither cultures of EC and PMA-primed CD4+ T cells separated by a microporous membrane insert nor the conditioned medium of PMA-primed T cells induced expression of ELAM-1 and VCAM-1 on EC. Cyclosporin A significantly inhibited the activation of T cells with PMA but had no effect on the ability of PMA-primed T cells to up-regulate endothelial CAM. Thus, CD4+CD45R0+ T cells via as yet unknown mechanism can significantly enhance the expression of each of the three endothelial adhesion ligands and, thereby, may facilitate the process of recruitment of additional leukocytes to exacerbate inflammation. 相似文献
998.
Toxoplasma gondii is able to invade phagocytic cells of the monocyte-macrophage lineage and replicates within a parasitophorous vacuole. Since macrophages may activate specific T lymphocytes by presenting pathogen-derived antigens in association with molecules of the MHC, we investigated the in vitro expression of host cell molecules involved in antigen processing and presentation before and during infection of murine bone marrow-derived macrophages (BMM) with T. gondii. Fifty-one hours after addition of T. gondii tachyzoites at different parasite-to-host ratios, up-regulation of total MHC class II molecules by interferon-gamma (IFN-γ) was dose-dependently abrogated in up to 50% of macrophages compared with uninfected control cultures. Quantitative analyses by flow cytometry revealed that the IFN-γ-induced surface expression of class II antigens as well as the IFN-γ-induced up-regulation of class I molecules was significantly decreased in T. gondii-infected macrophage cultures compared with uninfected controls. However, the constitutive expression of MHC class I antigens was not altered after parasitic infection, and infected BMM remained clearly positive for these molecules. After infection of macrophages preactivated with IFN-γ for 48 h, T. gondii also actively down-regulated an already established expression of MHC class II molecules. Furthermore, kinetic analysis revealed that the reduction in intracellular and plasma membrane-bound class II molecules started ≈ 20 h after infection. While MHC class II antigens were most prominently reduced in parasite-positive host cells, culture supernatant from T. gondii-infected BMM cultures also significantly inhibited expression of these molecules in uninfected macrophages. However, down-regulation of MHC class II molecules was not mediated by an increased production of prostaglandin E2, IL-10, transforming growth factor-beta or nitric oxide by infected BMM compared with uninfected controls. Our data indicate that intracellular T. gondii interferes with the MHC class I and class II antigen presentation pathway of murine macrophages and this may be an important strategy for evasion from the host's immune response and for intracellular survival of the parasite. 相似文献
999.
Ken Dewitte Marc Claeys Emeline Van Craenenbroeck Koen Monsieurs Hein Heidbuchel Vicky Hoymans Tibor Stoop 《Pathophysiology》2019,26(1):53-59
Aims
We explored the effect of remote ischaemic conditioning (RIC) on endothelial function and on circulating mediators.Methods and results
In 20 healthy male volunteers (mean age 31?±?10 years), flow-mediated dilation (FMD) was measured before and after 20?min of arm ischaemia, followed by reperfusion. Remote ischaemic conditioning (RIC) was performed by applying 3 cycles of 5?min of ischaemia of the leg at the onset of index arm ischaemia. Each volunteer underwent the IR-induced vascular injury protocol with and without RIC in a crossover study design.In the control group, IR significantly reduced FMD (5.9?±?2.9% before IR vs. 2.2?±?3.7% after IR; p?<?0.001). This effect was significantly attenuated by performing RIC (FMD of 5.5?±?3.1% before IR vs. 4.0?±?3.4% % after IR; p for interaction?=?0.01). Serum levels of SOD and ADMA increased significantly whereas MCP-1 and VEGF levels decreased significantly.Only changes in SOD levels were significantly related to the degree of RIC induced protection (r²?=?0.34; p?=?0.018).Conclusion
RIC has protective effects against endothelial IR injury. Our biomarker study suggests that anti-oxidative stress mediators, such as SOD, seem to be more involved in the pathogenesis of RIC-induced protection in humans than angiogenesis factors or chemo-attractant cytokines. 相似文献1000.
Kudryavtseva NN Gerrits MA Alekseenko OV Van Ree JM 《Bulletin of experimental biology and medicine》2005,140(3):320-322
Chronic injections of cocaine (20 mg/kg daily for 10 days) increase activity and decrease anxiety in male C57Bl/6j mice in
comparison with animals chronically injected with normal saline. U-50,488H (κ-opioid receptor agonist; 2.5 mg/kg) produced
an anxiolytic effect in animals preinjected with normal saline and had no effect in animals chronically injected with cocaine.
Presumably, chronic activation of dopaminergic systems caused by cocaine injections is paralleled by desensitization of k-opioid
receptor system.
__________
Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 9, pp. 305–307, September, 2005 相似文献