首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8591篇
  免费   449篇
  国内免费   221篇
耳鼻咽喉   74篇
儿科学   70篇
妇产科学   129篇
基础医学   2204篇
口腔科学   153篇
临床医学   408篇
内科学   1088篇
皮肤病学   97篇
神经病学   858篇
特种医学   99篇
外国民族医学   1篇
外科学   521篇
综合类   1157篇
预防医学   343篇
眼科学   127篇
药学   1310篇
中国医学   217篇
肿瘤学   405篇
  2023年   52篇
  2022年   118篇
  2021年   172篇
  2020年   163篇
  2019年   163篇
  2018年   169篇
  2017年   213篇
  2016年   209篇
  2015年   218篇
  2014年   479篇
  2013年   509篇
  2012年   446篇
  2011年   510篇
  2010年   372篇
  2009年   461篇
  2008年   503篇
  2007年   482篇
  2006年   431篇
  2005年   339篇
  2004年   306篇
  2003年   301篇
  2002年   188篇
  2001年   169篇
  2000年   183篇
  1999年   158篇
  1998年   156篇
  1997年   142篇
  1996年   149篇
  1995年   157篇
  1994年   143篇
  1993年   112篇
  1992年   84篇
  1991年   78篇
  1990年   79篇
  1989年   74篇
  1988年   96篇
  1987年   73篇
  1986年   67篇
  1985年   91篇
  1984年   78篇
  1983年   36篇
  1982年   49篇
  1981年   35篇
  1980年   49篇
  1979年   46篇
  1978年   26篇
  1977年   22篇
  1976年   22篇
  1975年   18篇
  1973年   19篇
排序方式: 共有9261条查询结果,搜索用时 31 毫秒
71.
Objective:Evolving evidence of anti-inflammatory effects is observed in patients with rheumatoid arthritis or ulcerative colitis following periodic adsorptive granulocyte and monocyte (GM) apheresis with a column containing cellulose acetate (CA) beads as apheresis carriers. This study was undertaken to obtain insights into mechanisms of anti-inflammatory actions of adsorptive GM apheresis with CA beads. Methods:In a series of in-vitro experiments, we investigated the effects of plasma proteins and the leucocytes 2 integrin (CD18) on granulocyte adsorption to CA beads. Results:Granulocyte adsorption to CA beads required plasma IgG, the complement C3 and was inhibited by an antibody to leucocytes CD18. Further, hepatocyte growth factor (HGF) and interleukin-1 receptor antagonist (IL-1ra) which have strong anti-inflammatory actions were released by granulocytes that adhered to CA beads. Conclusions:Plasma IgG, C3 derived complement activation fragments and leucocytes CD18 are involved in granulocyte adhesion to CA beads and hence the release of HGF and IL-1ra.Received 27 October 2003; returned for revision 16 December 2003; accepted by M. J. Parnham 8 January 2004  相似文献   
72.
73.
目的初步研究敲除Fm r1基因对动物生殖功能的影响。方法6~8周龄雌性Fm r1基因敲除小鼠24只,分为对照组、春季超排组和冬季超排组,每组8只,进行超排,用放射免疫分析法测定超排前后血清雌二醇(E2)、孕酮(P)、促黄体生成素(LH)和促卵泡生成素(FSH)含量,以及不同季节的超排卵数,并进行统计学处理和分析。结果超排后小鼠血清中P和LH含量明显增加[(24.43±13.33)比(1.60±0.46);(173.86±112.09)比(0.36±0.23),P<0.01]。与冬季(11.44±5.93)比较,春季(37.25±13.91)的超排卵数明显增加(P<0.01)。结论雌性Fm r1基因敲除小鼠的生殖系统功能没有明显异常。与正常小鼠一样,Frm 1基因敲除小鼠机体内P和LH的分泌随动物的生理发育时期而变化。其超排效果随季节而有显著不同。  相似文献   
74.
Problem:  We propose that the ability of estrogen exposure to increase the probability of a woman developing breast cancer may be related to decreased chemokine activity and suppression of immune surveillance in mammary tissue. The present study was conducted to determine whether estrogen could decrease monocyte bioactivity through alteration of chemokine receptor expression.
Method of study:  We examined the effect of estrogen and tamoxifen on the expression of the chemokine receptors CCR2 and CXCR3 on murine monocytes treated in culture and in vivo . Effects of estrogen on chemokine activation of monocytes were also evaluated.
Results:  Estrogen and tamoxifen significantly decreased expression of CCR2 and, to a lesser extent, CXCR3 on murine monocytes. Estrogen decreased chemotaxis of monocytes towards MCP-1/JE. The chemokines MCP-1/JE and MIP-1 α were unable to evoke increases in intracellular calcium in murine monocytes treated with estrogen, alone or in combination with tamoxifen.
Conclusions:  Our results show that estrogen suppresses the ability of monocytes to respond to certain chemokines, suggesting that estrogen exposure might decrease immune surveillance in tissues where the action of specific chemokines is involved.  相似文献   
75.
Summary The dose-related time course and occurrence of different seizure subtypes was examined in mice after i.c.v. administration of N-methyl-D-aspartate (NMDA), kainate (KA) or quisqualate (QA). At doses of 0.2 to 1 nmol, NMDA dose-dependently induced a single clonic-tonic seizure. Low doses (0.1 to 0.3 nmol) of KA induced only mild myoclonus and whole body clonus, which were dose-dependently replaced by short-delay clonic-tonic seizures at higher doses (0.4 to 1.2 nmol). In contrast, mice treated with 13 to 32 nmol of QA exhibited either mild myoclonus or whole body clonus as well as clonic-tonic seizures. Clonic-tonic seizures induced by NMDA or KA appeared at shorter latencies than those induced by QA, whereas whole body clonus induced by KA or QA appeared with long onset latencies. These results clearly show that i.c.v. administration of NMDA, KA and QA produces different patterns of seizures in mice. This study confirms that NMDA, KA and QA induce convulsions through different underlying mechanisms and suggests that different anatomical pathways are involved in these models.  相似文献   
76.
Summary The survival of grafts of dissociated allogeneic fetal neural dopamine (DA) rich tissue in the striatum has been studied after transplantation between inbred strains of mice differing at defined immunogenetical loci between donor and recipient. Six to 7 weeks and 15 weeks after grafting, surviving grafted DA neurons were found in the brains of all the recipients, albeit with a large variation in numbers, located either within the striatum or within the adjacent lateral ventricle. The mean number of surviving DA neurons did not differ between the syngeneic controls and the histoincompatible donor-host combinations, and there was no difference in survival between grafts that differed at single or multiple major histocompatibility complex (MHC) loci, and those that differed at multiple non-MHC loci. The amount of inflammatory cells in the graft area did not differ between the groups, and none of the animals showed massive infiltration of inflammatory cells. The in situ immunogenicity of the grafted neural tissue after intracerebral implantation was monitored by means of Simonsen's alloimmunization test, at 6–7 weeks after transplantation, which provides a sensitive measure primarily of the cellular immunological response. Most, but not all, graft recipients showed immunization with a Spleen Index (S.I.) close to that seen in recipients of an orthotopical skin graft of the same histoincompatibility combination. In contrast to the prolonged survival of the intracerebral neural transplants, none of the skin grafts survived longer than 3 weeks, thus demonstrating the immunologically privileged status of the brain. We conclude that intracerebrally grafted allogeneic neural tissue is capable of provoking a cellular immune response. Despite host immunization, however, the dissociated fetal neural allografts survived for at least 15 weeks without any overt signs of rejection, regardless of the donor-host combination used.  相似文献   
77.
本文用不同剂量的胰岛素、可地松、已烯雌酚,作用于妊娠开始至80小时的昆明小鼠,然后观察胚胎早期(植入前)和胚胎晚期(妊娠18天)的胚胎数量、发育时期及其与黄体数相比成活率的变化。实验表明,用较大剂量激素处理后,早期胚胎的上述各项指标,均表现出十分明显的抑制效果。当剂量逐渐降低后,仍表现出不同程度的抑制作用,只是逐渐趋于正常。所用各种激素对晚期胚胎的影响,表现在除部分死亡外,存活者的生长和发育一直落后。说明妊娠早期小鼠体内某些激素的水平,不仅直接影响早期,而且也影响晚期胚胎的发育。  相似文献   
78.
Immunocytochemical studies of postmortem human tissue have shown that the neurons at risk for degeneration in Alzheimer’s are marked by the ectopic expression of several cell cycle components. The current work investigates the roles that β-amyloid activated microglia might play in leading neurons to re-express cell cycle components. Stable cultures of E16.5 mouse cortical neurons were exposed to β-amyloid alone, microglial cells alone, or microglial cells activated by β-amyloid. Increased cell death was found in response to each of these treatments, however, only the amyloid activated microglial treatment increased the number of neurons that were positive for cell cycle markers such as PCNA or cyclin D and incorporation of BrdU. Double labeling with BrdU and TUNEL techniques verified that the ‘dividing’ neurons were dying, most likely through an apoptotic mechanism. The identity of the soluble factor(s) elaborated by the microglia remains unknown, but FGF2, a suspected neuronal mitogen, was ruled out. These results further support a model in which microglial activation by β-amyloid is a key event in the progression in Alzheimer’s disease.  相似文献   
79.
Sephadex beads were placed carefully in the uterus on days 2 and 3 and left for 6 to 8 h to absorb uterine secretion. The beads were then removed with volatile silicon oil and mounted on small pieces of nitrocellulose paper. Immuno-staining of these bead blots showed they contained the complement components C1q, C3, C4, and C5. We demonstrated that complement component C3 in the uterine secretion could be activated and deposited on model immune complexes, and also that antibody-coated erythrocytes were lysed in utero, that is, a membrane attack complex was produced. Thus, the mouse uterine secretion at the preimplantation stage contains a functionally active complement system.  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号