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   5132篇
  免费   392篇
  国内免费   100篇
耳鼻咽喉   76篇
儿科学   338篇
妇产科学   12篇
基础医学   2464篇
口腔科学   15篇
临床医学   226篇
内科学   513篇
皮肤病学   221篇
神经病学   38篇
特种医学   17篇
外科学   53篇
综合类   472篇
预防医学   240篇
眼科学   26篇
药学   567篇
  2篇
中国医学   262篇
肿瘤学   82篇
  2024年   20篇
  2023年   58篇
  2022年   85篇
  2021年   187篇
  2020年   136篇
  2019年   161篇
  2018年   144篇
  2017年   162篇
  2016年   182篇
  2015年   152篇
  2014年   247篇
  2013年   292篇
  2012年   248篇
  2011年   299篇
  2010年   200篇
  2009年   190篇
  2008年   210篇
  2007年   222篇
  2006年   203篇
  2005年   194篇
  2004年   169篇
  2003年   185篇
  2002年   151篇
  2001年   161篇
  2000年   150篇
  1999年   110篇
  1998年   111篇
  1997年   119篇
  1996年   112篇
  1995年   121篇
  1994年   89篇
  1993年   83篇
  1992年   72篇
  1991年   55篇
  1990年   46篇
  1989年   30篇
  1988年   33篇
  1987年   22篇
  1986年   22篇
  1985年   37篇
  1984年   21篇
  1983年   27篇
  1982年   26篇
  1981年   15篇
  1980年   6篇
  1979年   15篇
  1978年   9篇
  1977年   8篇
  1976年   11篇
  1974年   10篇
排序方式: 共有5624条查询结果,搜索用时 15 毫秒
61.
通过摇瓶培养考察转小鼠金属硫蛋白基因集胞藻6803及其野生藻的光合自养培养过程中碳源浓度、氮源浓度和光照度对这两种藻生长的影响。野生藻的最适生长碳源浓度(0.05-0.5g/L)比转基因藻的最适生长碳源浓度(0.02-0.05g/L)高。氮源浓度对转基因藻和野生藻的影响趋势相同。在0.3-4.5g/L范围内,随着氮源浓度的增高,藻体生长的最大细胞浓度降低。转基因藻生长的最佳光照度为1500lx,野  相似文献   
62.
Basophils produce interleukins (IL)-4 in response to various stimuli and may contribute to type 2 immune responses to various infections and allergens. We found that resting basophils freshly isolated from mice produce IL-4 in response to IL-3 but not to high-affinity Fc receptor (FcεRI) cross-linking (CL), yet both required the immunoreceptor tyrosine-based activation motif (ITAM) containing adaptor Fc receptor γ-chain (FcRγ), while basophils activated in vitro by IL-3 become responsive to FcεRI CL. Acquisition of responsiveness to FcεRI CL occurred upon infection with Trichinella spiralis or administration of superantigen. Because cultured basophils return to a quiescent state upon starvation with IL-3 with surface FcεRI levels unchanged, this acquisition is reversible and probably reflects intracellular events requiring protein synthesis. Interestingly, similar activation-associated acquisition was observed for responsiveness to other stimuli, including CD200R3 CL, which is known to signal via DAP-12, and the allergen protease papain. This acquisition of responsiveness to FcεRI CL was inhibited by Jak inhibitor. Thus, the IL-3 signal bifurcates downstream of Jak, into two distinct pathway, one leading to IL-4 production and the other to render basophils competent to respond to stimuli dependent on ITAM-containing adaptors DAP12 and FcRγ for IL-4 production.  相似文献   
63.
Priming of CBA/J mice with different doses of antigen has aprofound effect on the ratio of IgE versus IgG antibodies appearingupon Immunization. Repeated injections of minute doses induceIgG and high titers of IgE antibodies. Large doses elicit ahigh IgG but a very low IgE antibody titer. In order to studythe modalities for activation and inactivation of IgE-producingB cells, an in vitro culture system was established in whichspleen cells from animals primed with keyhole limpet hemocyaninwere re-stliulated with antigen. In contrast to the expectationfrom the in vivo situation, spleen cells from animals Immunizedwith large doses of antigen and virtually lacking IgE antibodiesproduce high amounts of IgE antibodies upon re-stimulation invitro. The titers in spleen cell cultures from mice primed withminute doses remain proportional to the response measured asserum antibodies. In accordance with the induction of high amountsof IgE antibodies in spleen cell cultures from mice primed withlarge doses, the frequency of IgE antibody-secreting cells wasraised drastically, 1000-fold. The in vitro response is a trueanamnestic response. The sudden appearance in high frequencyof IgE antibody-forming cells among spleen cells isolated fromprimed mice which have high IgG but virtually no IgE antibodytiters is as yet unexplained and the origin of the B memorycells has not yet been traced. The answer might be crucial forour understanding of the down-regulation of the IgE Immune responses.  相似文献   
64.
The role of inhibitory receptor superfamily (IRS) members in the pathophysiology of atopy is still largely unexplored but the past year or so has brought at least three important advances in the understanding of IRS member function: first, several targets of an inositol-phosphatase-dependent inhibitory signaling pathway utilized by some IRS members were identified; second, there is accumulating evidence from murine models supporting the importance of inhibitory Fc gamma receptors in modulating immune-complex-mediated inflammation; third, the inhibitory signaling capability of several previously identified candidate IRS members--including several expressed on cell types implicated in atopy and allergic reactions--has been demonstrated.  相似文献   
65.
A 7-year-old child presented with a severe form of Takayasu's arteritis, with two consecutive episodes involving the right testis and then the left kidney 6 months later. The renal artery obstruction was accompanied by severe hypertension. An aortography showed a complete obstruction of the left renal artery and a narrowing of the right subclavian artery. Plasma renin activity was high. Serum immunoglobulins were within the normal range, except for an increase in IgE (880 /l). Despite 4 months', treatment with antihypertensive drugs, prednisone, cyclophosphamide, and anticoagulant, the blood pressure never returned to normal and the left renal function remained completely absent. A nephrectomy was performed which immediately normalized plasma renin activity and blood pressure. The child was subsequently treated with alternateday prednisone for 3 months, alternating with 3 months of cyclophosphamide or, later, azathioprine. Persantine (dipyridamole) and acetylsalicylic acid were administered continuously. The right radial pulse returned to normal within 2 years. An 8-year follow-up failed to detect any new episode of arteritis. The right kidney showed signs of compensatory hypertrophy. Finally, a recent arteriography demonstrated not only a normal right renal artery blood flow but almost total disappearance of the right subclavian artery obstruction. However, the IgE remained abnormally high (2,023 g/l).  相似文献   
66.
Over a period of 4 years, 88 infants with cow's milk protein intolerance (CMPI) were followed prospectively in order to evaluate the persistence of CMPI and its relationship between either serum IgE levels or RAST results for cow's milk. After exclusion of lactose intolerance, two positive cow's milk elimination challenge tests were considered diagnostic for CMPI. At the age of 1, 2, 3 and 4 years respectively, 85%, 78%, 49% and 33% of the children still were cow's milk intolerant. Initial serum values of IgE 10 kU/l indicated a late development of tolerance to cow' milk proteins. At the age of 4 years, 90% of infants with initial IgE levels <10 k U/l had become tolerant to cow's milk while this was the case for only 47% of infants with initial IgE levels 10 k U/l. Initial RAST results for cow's milk bore no obvious relationship to outcome.  相似文献   
67.
The cytokine interleukin-10 (IL-10) plays a pivotal regulatory role in tolerizing exogenous antigens. Experimental data indicate that low cellular availability of the vitamin D hormone 1,25-dihydroxyvitamin D [1,25(OH)2D] results in a down-regulation of IL-10 concentrations. The tissue production of an adequate amount of 1,25(OH)2D depends on a high circulating 25-hydroxyvitamin D (25-OHD) level. The present study was thus aimed at evaluating the associations between season of birth, vitamin D status, and the allergy risk markers IL-10 and total immunoglobulin (IgE) in newborns. Cord blood was obtained from 49 infants born during the summer half year (mid-April to mid-October, geographic latitude 51 degrees N) and from 47 infants born during the winter half year (mid-October to mid-April, geographic latitude of 51 degrees N). Serum levels of 25-OHD were 99% higher, and IL-10 levels were 43% higher in the summer half year compared with the winter half year (p < 0.001 and p = 0.018). Moreover, the ratio of IL-10 to total IgE was 124% higher in the summer half year compared with the winter half year (p = 0.039). Serum levels of 25-OHD were correlated with IL-10 levels (r = +0.22; p < 0.05). Mothers' age, gestational ages, birth weights and serum 1,25(OH)2D levels did not differ between study groups. We conclude that the low vitamin D status of infants born in winter may at least in part adversely affect biomarkers of allergy risk.  相似文献   
68.
作者介绍了高亲和力IgE受体介导I型超敏反应,其活化后的信号传导通路,及其相关的抑制性受体方面的研究进展,包括FcγRIIβ、PIR B、SIRPα、CD81及MAFA。对高亲和力IgE受体介导的信号通路和其相关的抑制性受体的研究将有可能发现对抗Ⅰ型超敏反应的新靶点,从而有助于过敏相关疾病的治疗。  相似文献   
69.
IgE介导的食物过敏诊断程序及临床评价   总被引:12,自引:3,他引:9  
目的 对IgE介导的食物过敏的诊断流程进行临床评价。探讨高效的食物过敏诊断程序。方法 0~6岁患儿88例,以支气管哮喘、过敏性鼻炎、特应性皮炎以及消化道症状为主要临床表现,进行食物过敏原皮肤点刺试验(skin prick test,SPT),皮肤试验阳性者检测血清特异性IgE(sIgE)、sIgE阳性者进一步进行双盲安慰剂食物激发试验(double-blind placebo-control food challenge,DBPCFC)证实诊断。sIsE阴性者通过DBPCFC建立或排除诊断。结果 88例患儿中SPT(+)者25例。其中SPT(+)sIgE(+)者16例,SPT(+)sIsE(-)者9例;前者经DBPCFC进一步证实为食物过敏的有14例;后者通过DBPCFC建立诊断的3例。排除诊断的6例,根据SPT(+)sIgE(+)或SPT(+)sIsE(-)诊断食物过敏的阳性预计值为87.5%.阴性预计值为77.8%。结论 皮肤点刺试验结合sIgE检测有较高的食物过敏确诊率,当前两者不一致时,需要通过DBPCFC建立诊断。  相似文献   
70.
天灸疗法治疗支气管哮喘的时效关系研究   总被引:3,自引:0,他引:3  
目的:对三伏天灸与日常天灸、“庚”日天灸与“辛”日天灸的疗效进行观察对比。方法:将162例支气管哮喘患者分为三伏组和日常组,以甘遂、白芥子、麻黄、细辛等药物各等分,上加0.3g麝香制成的1cm×1cm大小药膏在肺俞、定喘等穴位进行贴敷治疗。日常组每隔10d贴药1次,3次为1疗程;三伏组分别于初伏、中伏、末伏贴药治疗。1个疗程后观察疗效、血清IgE含量、淋巴细胞转换率、嗜酸性粒细胞计数的变化并对比。另将80例支气管哮喘患者分为“庚”日和“辛”日贴药组治疗并比较其疗效。结果:①三伏组与日常组治疗后的疗效及血清IgE含量、淋巴细胞转换率、嗜酸性粒细胞计数比较无显著性统计学差异(P>0.05)。②“庚”日天灸组与“辛”日天灸组疗效无显著性统计学差异(P>0.05)。结论:天灸疗法主要通过经穴及药物双重作用起效,适宜全年开展此项治疗。  相似文献   
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