全文获取类型
收费全文 | 2095篇 |
免费 | 163篇 |
国内免费 | 45篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 96篇 |
妇产科学 | 26篇 |
基础医学 | 157篇 |
口腔科学 | 42篇 |
临床医学 | 293篇 |
内科学 | 369篇 |
皮肤病学 | 44篇 |
神经病学 | 60篇 |
特种医学 | 289篇 |
外科学 | 307篇 |
综合类 | 205篇 |
预防医学 | 142篇 |
眼科学 | 16篇 |
药学 | 117篇 |
2篇 | |
中国医学 | 32篇 |
肿瘤学 | 90篇 |
出版年
2022年 | 30篇 |
2021年 | 32篇 |
2020年 | 30篇 |
2018年 | 22篇 |
2017年 | 23篇 |
2016年 | 18篇 |
2015年 | 33篇 |
2014年 | 49篇 |
2013年 | 76篇 |
2012年 | 79篇 |
2011年 | 88篇 |
2010年 | 93篇 |
2009年 | 104篇 |
2008年 | 71篇 |
2007年 | 82篇 |
2006年 | 84篇 |
2005年 | 55篇 |
2004年 | 53篇 |
2003年 | 54篇 |
2002年 | 48篇 |
2001年 | 38篇 |
2000年 | 29篇 |
1999年 | 31篇 |
1998年 | 83篇 |
1997年 | 75篇 |
1996年 | 72篇 |
1995年 | 67篇 |
1994年 | 44篇 |
1993年 | 51篇 |
1992年 | 17篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 30篇 |
1988年 | 47篇 |
1987年 | 43篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 21篇 |
1983年 | 26篇 |
1982年 | 19篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1977年 | 18篇 |
1963年 | 17篇 |
1959年 | 22篇 |
1958年 | 29篇 |
1957年 | 19篇 |
1956年 | 30篇 |
1955年 | 42篇 |
1954年 | 35篇 |
排序方式: 共有2303条查询结果,搜索用时 15 毫秒
81.
Oxidative metabolism of the human eosinophil 总被引:14,自引:1,他引:14
We have compared the oxidative metabolism of human eosinophils (80%-90% purity) to that of neutrophils. Hexose monophosphate (HMP) shunt activity of eosinophils was higher than that of neutrophils under either resting or phagocytizing conditions. Eosinophil HMP shunt activity also was stimulated by phorbol myristate acetate, a membrane- active agent. Eosinophils showed a marked incorporation of 125I into trichloroacetic acid-insoluble material under resting conditions, which increased markedly during phagocytosis. Eosinophils likewise showed a greater reduction of nitroblue tetrazolium dye during phagocytosis than did neutrophils. Measurement of other parameters of oxidative metabolism indicated that eosinophils generated superoxide anion following phagocytosis and also elicited a burst of chemiluminescence similar to that observed during phagocytosis by neutrophils. Measurement of NADPH oxidase activity demonstrated that this enzyme was 3-6 times more active in fractions isolated from eosinophils than in corresponding fractions isolated from neutrophils; this was observed over a range of substrate concentrations. The eosinophil enzyme sedimented differently than the neutrophil enzyme with differential centrifugation; neither showed sedimentation characteristics of peroxidase. These data indicate that eosinophils possess a similar, although in some ways more potent, oxidative burst than neutrophils and are consistent with a role for NADPH oxidase in the initiation of that burst. 相似文献
82.
Chronic granulocytic leukaemia (CGL) cells which contained a high concentration of unsaturated folate binding protein were incubated in suspension culture for a period of 5 h. Cell samples were periodically assayed for binder and these demonstrated active synthesis which was inhibited by puromycin, cyclo heximide, N-ethylmaleimide, and by incubation at 4 degrees C, but not by actinomycin D. Folate binding activity could also be demonstrated in the culture medium and this increased with the duration of incubation. This release of binder was inhibited by culturing the cells at 4 degrees C and by the addition of N-ethylmaleimide, but not by actinomycin D, puromycin, or cycloheximide. When the pre- and post-culture cell lysates were saturated with tritiated folic acid ([3H]PteGlu) and subjected to chromatography on DEAE-agrarose, approximately half of the bound folate eluted with 0.001 M phosphate buffer at pH 6.0 and the other half eluted with 0.2 M buffer at pH 7.2. The culture medium and plasma from this patient with CGL was well as serum from two normal subjects saturated with [3H]PteGlu and similarly chromatographed contained primarily the acidic binder and much less of the binder eluting with the low molarity buffer. Since a folate binding protein immunochemically similar to the binder in CGL cells has been identified in the serum of non-leukaemic subjects, these experiments suggest that the source of circulating folate binding protein may be the immature granulocyte. 相似文献
83.
Selecting binding and complement-mediated lysis of human hepatoma cells (PLC/PRF/5) in culture by monoclonal antibodies to hepatitis B surface antigen.
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
D Shouval J R Wands V R Zurawski Jr K J Isselbacher D A Shafritz 《Proceedings of the National Academy of Sciences of the United States of America》1982,79(2):650-654
High-affinity 125I-labelled monoclonal antibodies to hepatitis B virus surface antigen (HBsAg) bind to human hepatocellular carcinoma cell line, PLC/PRF/5, which synthesizes and secretes HBsAg. These monoclonal antibodies of the IgG1, IgG2a, and IgM isotypes are directed against different antigenic determinants on HBsAg and, in the presence of complement, both anti-HBs IgG2a and IgM, but not anti-HBs IgG1, lyse PLC/PRF/5 cells in culture. Although there is a low level of anti-HBs binding (especially with anti-HBs IgM) to human hepatoma cell lines which do not synthesize HBsAg (SK-Hep 1 and Mahlavu cells), this interaction does not lead to complement-mediated cell lysis and is thought to be nonspecific. Minimal binding of 125I-labeled anti-influenza HA antigen IgM binding to PLC/PRF/5 cells was also detected, but this likewise did not lead to complement-mediated cell lysis. These results indicate that a human hepatocellular carcinoma cell line, persistently infected with hepatitis B virus, can be recognized and lysed by monoclonal antibodies directed against specific determinants of HBsAg. Monoclonal antibodies to this viral envelope protein may prove to be useful immunodiagnostic and immunotherapeutic agents when such viral epitopes are expressed on the surface of infected cells. 相似文献
84.
Research on hepatic stem cells has entered a new era of controversy, excitement, and great expectations. Although adult liver stem cells have not yet been isolated, an enormous repopulating capacity of transplanted mature hepatocytes under conditions of continuous liver injury has been discovered. Stem/progenitor cells from fetal liver have been successfully isolated and transplanted, repopulating up to 10% of normal liver. However, progenitor cell lines from adult and embryonic liver have not shown significant repopulating activity. Intensive research on embryonic stem cells has revealed the first promising attempts to use these cells as a source of hepatic progenitors. Conditions for their differentiation in vitro, isolation of purified hepatic progenitor cells, and liver repopulation are currently being evaluated. Multilineage adult progenitor cells of mesenchymal origin from bone marrow, muscle, and brain may turn out to be the long-sought primitive potential stem cells remaining in adult tissues. 相似文献
85.
6q deletions define distinct clinico-pathologic subsets of non- Hodgkin's lymphoma 总被引:11,自引:1,他引:11
Offit K; Parsa NZ; Gaidano G; Filippa DA; Louie D; Pan D; Jhanwar SC; Dalla- Favera R; Chaganti RS 《Blood》1993,82(7):2157-2162
Commonly observed in lymphoid neoplasms, deletions of 6q have been correlated with histologic and clinical subsets of non-Hodgkin's lymphoma (NHL). Our recent analysis of loss of heterozygosity of 6q loci in NHL showed two regions of minimal molecular deletion (RMD), an RMD1 at 6q25-27 and an RMD2 at 6q21-23. To establish correlations between these RMDs and regions of minimal cytogenetic deletions (RCDs) on 6q, and to define associations between RCDs and clinico-pathologic features, we have analyzed chromosome 6 abnormalities in 459 consecutively ascertained, karyotypically abnormal cases of NHL. Among these, 126 (27.5%) cases had structural abnormalities of chromosome 6, of which 94 were deletions. Analysis of these deletions identified three RCDs. An RCD1 encompassing 6q25-27 was seen in 45 intermediate- grade NHL. An RCD2 at 6q21 was observed in 11 high-grade NHL, 9 of which were of the immunoblastic subtype. An RCD3 at 6q23 was noted in 18 low-grade NHL lacking a t(14;18) translocation. Of these 18 cases, 12 were small lymphocytic NHL and, in 2 of these, del(6q) was the sole karyotypic abnormality. In 20 cases of low-grade NHL with t(14;18), the deletions spanned both RCD1 and RCD3. These data suggested the presence of at least 3 tumor suppressor genes on 6q within RCD1, RCD2, and RCD3; they also showed associations between RCDs in 6q and subsets of NHL, including a specific association between a group of well-differentiated lymphoid neoplasms and RCD3. The apparent heterogeneity of breakpoints when all NHLs are considered together explains the inability of previous studies to reliably establish correlations between recurring 6q deletions and histologic and clinical features of NHL. 相似文献
86.
87.
Prevalence of Candida spp., xerostomia,and hyposalivation in oral lichen planus – A controlled study
Objective
To determine the frequency of Candida spp., xerostomia, and salivary flow rate (SFR) in three different groups: patients with OLP (OLP group), patients with oral mucosal lesions other than OLP (non‐OLP group), and subjects without oral mucosal lesions (control group).Material and methods
Xerostomia as well as SFR was investigated in the three groups. Samples for isolation of Candida spp. were collected from OLP lesions (38 patients), non‐OLP lesions (28 patients), and healthy subjects (32 subjects).Results
There was no statistically significant difference regarding the frequency of xerostomia and hyposalivation among the three groups (P > 0.05). A higher prevalence for colonization by Candida spp. was found in the healthy subject as compared to that of patients with OLP (P = 0.03) and non‐OLP (P = 0.02) groups. Low SFR was not a factor for colonization by Candida spp.Conclusions
Xerostomia and hyposalivation occur with similar frequency in subjects with and without oral lesions; also, the presence of oral lesions does not increase the susceptibility to colonization by Candida spp. It seems that any study implicating Candida spp. in the malignant transformation of oral lesions should be carried out mostly on a biochemical basis, that is, by testing the capability of Candida spp. to produce carcinogenic enzyme. 相似文献88.
目的研究B超引导下臂丛神经阻滞麻醉的临床效果及安全性。方法将本院行上肢手术的90例患者随机分为对照组(n=48)和B超引导组(n=42)。对照组以盲探的方法行臂丛神经阻滞麻醉,B超引导组在B型超声仪引导下行臂丛神经阻滞麻醉。比较两组的麻醉效果。结果B超引导组感觉阻滞起效时间、麻醉药物使用剂量均优于对照组,但麻醉操作时间长于对照组(P<0.05)。B超引导组不同臂丛神经的感觉阻滞完善率均高于对照组,并发症总发生率低于对照组(P<0.05)。结论与盲探法相比,B超引导下行臂丛神经阻滞麻醉的麻醉操作时间虽然有所延长,然而麻醉效果佳,能够缩短感觉阻滞起效时间、减少麻醉药物用量,且安全性好。 相似文献
89.
鼻内镜下咽鼓管置管术治疗分泌性中耳炎 总被引:13,自引:3,他引:10
目的探索有效治疗分泌性中耳炎的方法。方法将分泌性中耳炎患者63例(78耳)随机分成两组:实验组:在鼻内镜下,对31例(38耳)分泌性中耳炎患者行咽鼓管置管术,留管并反复注药治疗;对照组:对32例(40耳)患者使用传统的鼓膜切开置管术治疗,术后随访6~9个月,比较两组疗效。结果实验组治愈16耳,占42.1%,好转18耳,占47.4%,总有效率89.5%:对照组:治愈8耳,占20.0%,好转21耳,占52.5%,总有效率72.5%。治疗后两组差异有显著性(P〈0.05)。结论在鼻内镜下行咽鼓管置管术是在直视下操作,通过咽鼓管的自然通道插入导管,不仅避免了损伤鼓膜,也避免了咽鼓管吹张的重复操作,为临床治疗分泌性中耳炎提供了一个良好途径。 相似文献
90.
目的 研究基因组芯片检测大黄抑制鼠疫耶尔森菌分子机制的方法 .方法 使用的鼠疫耶尔森菌全基因组芯片包含4005条鼠疫耶尔森菌基囚.应用液体稀释法测定大黄对鼠疫耶尔森菌的最小抑菌浓度(MIC),基因芯片表达谱实验中,大黄作用鼠疫耶尔森菌的浓度为10×MIC,作用时间为30 min,提取并纯化鼠疫耶尔森菌总RNA,反转录合成cDNA,用Cy3,Cy5染料标记后,与鼠疫耶尔森菌全基因组芯片杂交,通过芯片扫描仪获得表达谱分析结果 .应用实时定量PCR技术对芯片结果 进行验证.结果 大黄对鼠疫耶尔森菌的MIC为0.02500 kg/L.获得了大黄作用鼠疫耶尔森菌的基因芯片表达谱.大黄作用鼠疫菌的明显差异表达基凶共有498个,上渊基闪358个,下凋基因140个.结论 应用鼠疫耶尔森菌全基因组DNA芯片可以进行大黄抑制鼠疫耶尔森菌的分子作用机制研究. 相似文献