全文获取类型
收费全文 | 166093篇 |
免费 | 4247篇 |
国内免费 | 1661篇 |
专业分类
耳鼻咽喉 | 1752篇 |
儿科学 | 6193篇 |
妇产科学 | 2680篇 |
基础医学 | 20571篇 |
口腔科学 | 4313篇 |
临床医学 | 11196篇 |
内科学 | 31844篇 |
皮肤病学 | 2881篇 |
神经病学 | 10395篇 |
特种医学 | 3477篇 |
外国民族医学 | 1篇 |
外科学 | 26116篇 |
综合类 | 9051篇 |
一般理论 | 4篇 |
预防医学 | 10111篇 |
眼科学 | 3286篇 |
药学 | 17242篇 |
9篇 | |
中国医学 | 6007篇 |
肿瘤学 | 4872篇 |
出版年
2022年 | 1298篇 |
2021年 | 2248篇 |
2020年 | 1051篇 |
2019年 | 12634篇 |
2018年 | 12365篇 |
2017年 | 5306篇 |
2016年 | 1230篇 |
2015年 | 1540篇 |
2014年 | 2294篇 |
2013年 | 4011篇 |
2012年 | 2430篇 |
2011年 | 2440篇 |
2010年 | 2118篇 |
2009年 | 2090篇 |
2008年 | 2559篇 |
2007年 | 3645篇 |
2006年 | 3936篇 |
2005年 | 3965篇 |
2004年 | 3521篇 |
2003年 | 3183篇 |
2002年 | 3111篇 |
2001年 | 3097篇 |
2000年 | 3282篇 |
1999年 | 2994篇 |
1998年 | 3166篇 |
1997年 | 2621篇 |
1996年 | 2473篇 |
1995年 | 2790篇 |
1994年 | 2725篇 |
1993年 | 2092篇 |
1992年 | 1736篇 |
1991年 | 1734篇 |
1990年 | 1464篇 |
1989年 | 1138篇 |
1988年 | 1191篇 |
1987年 | 1052篇 |
1986年 | 927篇 |
1985年 | 5501篇 |
1984年 | 7358篇 |
1983年 | 5882篇 |
1982年 | 6353篇 |
1981年 | 5776篇 |
1980年 | 4940篇 |
1979年 | 4989篇 |
1978年 | 4085篇 |
1977年 | 3067篇 |
1976年 | 3534篇 |
1975年 | 2744篇 |
1974年 | 2523篇 |
1973年 | 2234篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The sister chromatid exchange (SCE) incidence and growth kinetics have been studied by means of an in vitro bromodeoxyuridine (BrdU) chromosome labeling method in the bone marrow cells of 17 acute myeloblastic leukemia (AML) patients with only diploid cells at diagnosis, remission, and relapse of the disease. At diagnosis, the cells tended to exhibit a low SCE frequency as compared to that during remission. An increased SCE frequency was observed after chemotherapy during remission or relapse. At diagnosis and relapse, when leukemic blast cells predominated in the marrow, they were characterized by the predominance of cells that had undergone only one cell cycle after BrdU exposure. In contrast, the marrow cells during remission tended to resemble the control pattern of growth kinetics, with a predominance of cells undergoing second and third cell cycles in the presence of BrdU. These results suggest that the growth rate of leukemic and nonleukemic cells is different, and that chemotherapy can cause an increased SCE frequency in the marrow cells of AML patients irrespective of the state of the disease. 相似文献
992.
P C Arck M Rose K Hertwig E Hagen M Hildebrandt B F Klapp 《Human reproduction (Oxford, England)》2001,16(7):1505-1511
BACKGROUND: Stress is thought to be abortogenic and psycho-neuro-immunological pathways have been suggested to be involved in triggering miscarriages. From experiments in pregnant mice exposed to stress some insights into the underlying mechanisms have been gained, delineating immunological imbalances as a cause of pregnancy failure. In order to test the validity of the conclusions drawn from murine experiments and the role of stress in human pregnancy loss, the following study was performed. METHODS: We used an established perceived stress questionnaire and measured the stress score of women with a confirmed diagnosis of first trimester spontaneous abortion (n = 94). Decidual tissue was investigated by immunohistochemistry and in-situ hybridization to detect the presence and distribution of immunocompetent decidual cells [CD56(+) natural killer (NK) cells, CD8(+)and CD3(+) T cells, tryptase(+) mast cells (MCT(+)) and tumour necrosis factor (TNF)-alpha(+) cells]. The patient cohort was divided into women experiencing low or high levels of stress. RESULTS: In the decidua of women with high stress scores we observed significantly higher numbers of MCT(+), CD8(+) T cells and TNF-alpha(+) cells per mm(2) tissue (P < or = 0.05). No significant differences between individuals with lower or higher stress scores could be observed with respect to decidual CD56(+) NK and CD3(+) T cells. CONCLUSIONS: Using a questionnaire to score perceived stress in humans may be a valid approach to assess non-biased stress scores. Stress-triggered abortion in humans, identified by a questionnaire, can be linked to immunological imbalances. 相似文献
993.
994.
Content of Autoantibodies to Bradykinin and β-Amyloid1-42 as a Criterion for Biochemical Differences between Alzheimer's Dementias 总被引:2,自引:0,他引:2
Myagkova MA Gavrilova SI Lermontova NN Kalyn YB Selezneva ND Zharikov GA Kolykhalov IV Abramenko TV Serkova TP Bachurin SO 《Bulletin of experimental biology and medicine》2003,136(1):49-52
We measured serum content of autoantibodies to -amyloid protein A1-42, its neurotoxic fragment A25-35, vasopressin, bradykinin, thrombin, antithrombin III, 2-macroglobulin, and angiotensin II in patients with various forms of Alzheimer's dementias, including presenile and senile dementias of the Alzheimer type. The ratio of antibradykinin and anti-A1-42 autoantibody contents differed by 39% in these patients. Our results can be used for the development of a new biochemical method for differential diagnostics of dementias of the Alzheimer type. 相似文献
995.
IL-1 is required for allergen-specific Th2 cell activation and the development of airway hypersensitivity response 总被引:1,自引:0,他引:1
Nakae S Komiyama Y Yokoyama H Nambu A Umeda M Iwase M Homma I Sudo K Horai R Asano M Iwakura Y 《International immunology》2003,15(4):483-490
IL-1 is a pro-inflammatory cytokine consisted of two molecular species, IL-1alpha and IL-1beta, and the IL-1 receptor antagonist (IL-1Ra) is a natural inhibitor of both molecules. Although it is suggested that IL-1 potentiates immune responses mediated by T(h)2 cells, the role of IL-1 in asthma still remains unclear. In this study, we demonstrate that the ovalbumin (OVA)-induced airway hypersensitivity response (AHR) in IL-1alpha/beta-deficient (IL-1alpha/beta(-/-)) mice was significantly reduced from the levels seen in wild-type mice, whereas the responses seen in IL-1Ra(-/-) mice were profoundly exacerbated, suggesting that IL-1 is required for T(h)2 cell activation during AHR. OVA-specific T cell proliferation, IL-4 and IL-5 production by T cells, and IgG1 and IgE production by B cells in IL-1alpha/beta(-/-) mice were markedly reduced compared with these responses in wild-type mice; such responses were enhanced in IL-1Ra(-/-) mice. Using IL-1alpha(-/-) and IL-1beta(-/-) mice, we determined that both IL-1alpha and IL-1beta are involved in this reaction. Both IgG1 and IgE levels were reduced in IL-1beta(-/-) mice, while only IgE levels were affected in IL-1alpha(-/-) mice, indicating a functional difference between IL-1alpha and IL-1beta. These observations indicate that IL-1 plays important roles in the development of AHR. 相似文献
996.
Kadereit S Junge GR Kleen T Kozik MM Kaminski BA Daum-Woods K Fu P Tary-Lehmann M Laughlin MJ 《Journal of clinical immunology》2003,23(6):485-497
Regulation of nuclear factor of activated T cells-c2 (NFATc2) gene expression is not clearly defined. We previously reported reduced NFATc2 protein expression in cord blood T lymphocytes. Here we show that NFATc2 expression in T cells is dependent in part on the presence of IFN-gamma during primary stimulation, as blocking of IFN-gamma blunted NFATc2 protein and mRNA upregulation. Conversely, addition of exogenous IFN-gamma during stimulation resulted in increased expression of NFATc2 in cord blood T lymphocytes. This correlated with rescue of deficient IFN-gamma expression by cord blood T cells. Rescue of IFN-gamma expression in cord blood T cells was dependent on the presence of antigen-presenting cells, as addition of IFN-gamma during stimulation of purified cord blood T cells did not result in an increase of IFN-gamma expression, and depletion of monocytes ablated the rescue of IFN-gamma expression. Our results point to impaired function in the antigen-presenting cell population of cord blood, playing a role in the hyporesponsiveness of T cells. 相似文献
997.
A simple numerical simulation of AIDS patient detoxification by a hypothetical extracorporeal device for the removal of viruses, infected white cells, and syncytia has been designed. The mathematical model accounts for healthy blood white cells attacking and destroying the viruses, while at the same time the viruses attack and infect certain white cells. The infected white cells serve as a site for viral growth; eventually the cells lyse, releasing a large number of viruses into the blood stream. The healthy white cells and infected white cells combine to form syncytia, where the virus multiplies, and finally the syncytium ruptures releasing all the virus. This model can be used to predict concentrations over a specified period for the patient. This is a mathematical model to be used as a research and design tool only. 相似文献
998.
Kimihiro Komori Guifa Chen Hikaru Suzuki 《Pflügers Archiv : European journal of physiology》1989,413(4):359-364
In isolated buccal segment of the rabbit facial vein, electrical responses produced by perivascular nerve stimulation and exogenously applied noradrenaline (NA) were recorded from the smooth muscle cells using microelectrode. Perivascular nerve stimulation hyperpolarized the smooth muscle cell membrane. The hyperpolarization was converted to depolarization after application of the -adrenoceptor antagonist, propranolol, and the depolarization was blocked by
2 antagonists, yohimbine. These responses elicited by nerve stimulation were blocked by tetrodotoxin or guanethidine, but not by atropine. Exogenously applied NA mimicked the responses elicited by nerve stimulation. The amplitude of the -adrenoceptor-mediated hyperpolarization was increased in low potassium solution, decreased in high potassium solution, but unaltered by low sodium or low chloride solution, i.e., the hyperpolarization may be generated by an increase in potassium conductance of the membrane. An involvement of the apamin-sensitive (Ca-dependent) potassium channel or sodium-potassium ATPase in the hyperpolarization was ruled out. 相似文献
999.
虎杖4号与多巴胺、654-2治疗大鼠失血性休克疗效比较 总被引:7,自引:2,他引:7
使用大鼠复制重度失血性休克模型后,分别用盐水、多巴胺、654-2及虎杖4号结晶给予治疗。结果:虎杖4号治疗组大鼠的平均存活时间明显长于其余三组,存活率亦有提高,给药后,三级动脉、静脉的口径恢复正常。提示:虎杖4号可以改善微循环;治疗大鼠失血性休克的疗效优于多巴胺及654-2。 相似文献
1000.
中药蜈蚣对小鼠胚胎发育的影响 总被引:2,自引:0,他引:2
孕鼠161只随机分组,在孕期第7-11天给实验组分别以500mg/(kg.d)(蜈蚣1组)及1000mg/(kg.d)(蜈蚣2组)的中药蜈蚣煎剂灌胃,至孕期18天记录各组孕鼠和胎鼠的发育情况。结果表明:蜈蚣1,2两组致畸作用明显,死胎,吸收胎比例升高;蜈蚣2组胎鼠和孕鼠的体重均下降,堕胎作用显著,与对照组比较,差异均有非常显著意义(P<0.01)。 相似文献