全文获取类型
收费全文 | 1320篇 |
免费 | 67篇 |
国内免费 | 113篇 |
专业分类
儿科学 | 69篇 |
妇产科学 | 10篇 |
基础医学 | 148篇 |
口腔科学 | 25篇 |
临床医学 | 159篇 |
内科学 | 335篇 |
皮肤病学 | 45篇 |
神经病学 | 39篇 |
特种医学 | 363篇 |
外国民族医学 | 1篇 |
外科学 | 47篇 |
综合类 | 40篇 |
预防医学 | 61篇 |
眼科学 | 12篇 |
药学 | 76篇 |
中国医学 | 1篇 |
肿瘤学 | 69篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 20篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 16篇 |
2013年 | 40篇 |
2012年 | 9篇 |
2011年 | 28篇 |
2010年 | 49篇 |
2009年 | 52篇 |
2008年 | 25篇 |
2007年 | 64篇 |
2006年 | 34篇 |
2005年 | 50篇 |
2004年 | 12篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 92篇 |
1997年 | 95篇 |
1996年 | 103篇 |
1995年 | 64篇 |
1994年 | 62篇 |
1993年 | 64篇 |
1992年 | 11篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 49篇 |
1988年 | 39篇 |
1987年 | 50篇 |
1986年 | 28篇 |
1985年 | 44篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 30篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 26篇 |
1975年 | 15篇 |
1970年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有1500条查询结果,搜索用时 15 毫秒
51.
In our initial immunochemical study of the red blood cell (RBC) membrane proteins targeted in 20 cases of warm-antibody autoimmune hemolytic anemia (AHA), RBC eluates of 6 patients mediated immunoprecipitation (IP) of both band 3 and glycophorin A (GPA). This dual IP pattern had previously been observed with murine monoclonal antibodies (MoAbs) against the high frequency blood group antigen, Wrb (Wright), suggesting that the Wrb epitope may depend on a band 3-GPA interaction. Earlier, anti-Wrb had been identified serologically as a prominent non-Rh specificity of AHA autoantibodies. In the present study, 6 autoantibody eluates immunoprecipitating band 3 and GPA from common Wr(b+) RBCs were retested, in parallel with murine anti-Wrb MoAbs, against very rare Wr(a+b-)En(a+)RBCs. One patient's autoantibodies were unreactive with the Wr(b-) RBCs by either IP or indirect antiglobulin test (IAT) and were judged to have "pure" anti- Wrb specificity. Two other patients' autoantibodies displayed both IP and serologic evidence for anti-Wrb as a major component in combination with one or more additional specificities. However, among 3 other patients whose autoantibodies coprecipitated band 3 and GPA, there was no reduction in IP or IAT reactivity with Wr(b-) RBCs in 2 and only slight reduction in the third. We conclude (1) that human anti-Wrb autoantibodies, like their murine monoclonal counterparts, coprecipitate band 3 and GPA from human RBCs; but (2) that not all antibodies with this IP behavior have anti-Wrb serologic specificity, as defined by this donor's Wr(b-) RBCs. The possibility of an additional (non-Wrb) RBC epitope dependent on a band 3-GPA interaction is raised. 相似文献
52.
Peripheral blood mononuclear cells from five patients with essential thrombocythemia (ET) were cultured in vitro to evaluate restricted megakaryocytic (CFU-Meg), myeloid (CFU-GM), and erythroid (BFU-E) progenitor cell development. Varying concentrations of aplastic canine serum served as the source of megakaryocyte colony-stimulating activity, and cultured megakaryocyte ploidy distributions were determined by Feulgen staining and microfluorometry. Megakaryocyte colony growth was strikingly abnormal in all five patients evaluated. Four of the 5 had a marked expansion in the concentration of circulating CFU-Meg and 3 of 4 manifested abnormalities in cultured megakaryocyte colony size (2 unusually large and 1 small). Unstimulated megakaryocyte colony growth was substantially increased in three patients. However, the fraction of megakaryocyte progenitors in cell cycle was near or below normal in all instances. Endomitotic megakaryocyte development was disordered in each of the four ET patients in whom it was evaluable. In normal subjects, mean megakaryocyte ploidy values vary biphasically with aplastic canine serum concentration and peak at 13.2 N following 12 to 15 days of culture. In contrast, day 12 mean ploidy values in cultures from the ET patients remained low at all aplastic canine serum concentrations and reached a maximum averaging only 8.4 N. Three patients were evaluated serially at extended culture durations of up to 21 days. The cultured megakaryocyte ploidy was unchanged during this interval for two of the patients. For the third patient, ploidy increased steadily, reaching abnormally high ploidy values by day 21. Progenitor cell expansion was limited to the megakaryocyte line in three patients. However, two patients had substantial increases in CFU-GM, one of whom also had a marked increase in BFU-E. There was no significant unstimulated colony growth by either CFU-GM or BFU-E. These data indicate that ET is usually characterized by an expansion in the concentration of circulating CFU-Meg in vivo which manifest both disordered replication and endoreduplication in vitro. 相似文献
53.
Aurin tricarboxylic acid: a novel inhibitor of the association of von Willebrand factor and platelets 总被引:2,自引:1,他引:2
Shear stress activated platelets undergo aggregation in the presence of large or unusually large von Willebrand factor (vWF) multimers without the addition of ristocetin or any other exogenous chemical. This phenomenon may be analogous to the platelet aggregation that leads to thrombosis in the narrowed arteries and arterioles of patients with atherosclerosis or vasospasm. A triphenyl-methyl compound, aurin tricarboxylic acid (ATA), inhibits shear-induced, vWF-mediated platelet aggregation in platelet-rich plasma (PRP) in concentrations above 200 mumol/L and in buffer suspensions of washed platelets at a concentration of 0.1 mumol/L. In a concentration-dependent manner, ATA also inhibits ristocetin-induced, vWF-mediated platelet clumping in both fresh and formaldehyde-fixed platelet suspensions. This inhibition can be overcome by increasing the concentration of vWF, following the kinetics of first order competitive inhibition. ATA prevents the attachment to platelets of the largest vWF multimeric forms found in normal plasma and of the unusually large vWF multimers derived from endothelial cells. The rate of aggregation and degree of inhibition by ATA is not accounted for by the binding of ristocetin or calcium. Arachidonic acid- and adenosine diphosphate (ADP)-induced aggregation are not inhibited by ATA. Platelets incubated with ATA can be easily separated from the compound. However, ATA binds to large vWF multimeric forms and inhibits their ristocetin-induced interaction with platelet glycoprotein Ib. Because ATA also inhibits shear-induced, vWF-mediated platelet aggregation in vitro in the absence of ristocetin, it may be a useful prototype compound to impede the development of arterial thrombosis in vivo. 相似文献
54.
Pal L; Leykin L; Schifren JL; Isaacson KB; Chang YC; Nikruil N; Chen Z; Toth TL 《Human reproduction (Oxford, England)》1998,13(7):1837-1840
A case series of eight cycles of in-vitro fertilization (IVF) in five women
diagnosed with malignant disorders is presented. These patients chose to
defer definitive treatment for a chance for preservation of potential
fertility. The response of these patients to ovarian stimulation, and the
outcome, was compared with 17 IVF cycles in 12 age- matched patients with
isolated tubal infertility. An apparent adverse influence of malignant
disease on the quality and behaviour of oocytes was observed. Despite a
comparable total number of oocytes per cycle in the two groups, a
significantly reduced percentage of mature oocytes was retrieved per cycle
from patients with malignant diseases. The oocytes from patients with
malignant disorders were of a poorer quality and exhibited a significantly
impaired fertilization rate compared to the controls. We propose that
neoplastic processes, irrespective of the site or cell of origin, may have
a detrimental impact on the biology of oocytes, an effect akin to that seen
on spermatozoa in men with certain malignancies.
相似文献
55.
56.
Erythropoietin can promote erythroid progenitor survival by repressing apoptosis through Bcl-XL and Bcl-2 总被引:15,自引:9,他引:15
Erythropoietin (Epo), the hormone that is the principal regulator of red blood cell production, interacts with high-affinity receptors on the surface of erythroid progenitor cells and maintains their survival. Epo has been shown to promote cell viability by repressing apoptosis; however, the molecular mechanism involved is unclear. In the present studies we have examined whether Epo acts as a survival factor through the regulation of the bcl-2 family of apoptosis-regulatory genes. We addressed this issue in HCD-57, a murine erythroid progenitor cell line that requires Epo for proliferation and survival. When HCD-57 cells were cultured in the absence of Epo, Bcl-2 and Bcl-XL but not Bax were downregulated, and the cells underwent apoptotic cell death. HCD-57 cells infected with a retroviral vector encoding human Bcl-XL or Bcl-2 rapidly stopped proliferating but remained viable in the absence of Epo. Furthermore, endogenous levels of bcl-2 and bcl-XL were downregulated after Epo withdrawal in HCD-57 cells that remained viable through ectopic expression of human Bcl-XL, further indicating that Epo specifically maintains the expression of bcl-2 and bcl-XL. We also show that HCD-57 rescued from apoptosis by ectopic expression of Bcl-XL can undergo erythroid differentiation in the absence of Epo, demonstrating that a survival signal but not Epo itself is necessary for erythroid differentiation of HCD-57 progenitor cells. Thus, we propose a model whereby Epo functions as a survival factor by repressing apoptosis through Bcl-XL and Bcl-2 during proliferation and differentiation of erythroid progenitors. 相似文献
57.
58.
AMP-18,一种新发现的胃黏膜保护因子 总被引:3,自引:0,他引:3
AMP-18是一种新发现的由胃腺体上皮细胞合成的小分子蛋白质,独特表达于胃黏膜,机体其他部位少见,胃癌组织中表达缺失.AMP-18 由185个氨基酸组成,除去N端信号肽(20个氨基酸)后大小约18 ku,第54-150个氨基酸组成高度保守的结构域(BRICHOS区域)承担主要的生理功能.AMP-18由胃腺体上皮细胞以胞吐的方式分泌到胃黏液中,他的合成和分泌与个体生长发育有关,并受福斯高林、吲哚美辛、地塞米松等药物的影响.目前发现 AMP-18的生理功能主要有促进胃黏膜上皮细胞的有丝分裂,促进细胞的迁徙,促胃肠黏膜损伤的修复,保持胃肠黏膜的完整等. 相似文献
59.
Dongari-Bagtzoglou AI; Warren WD; Berton MT; Ebersole JL 《International immunology》1997,9(9):1233-1241
CD40, a member of the tumor necrosis factor-alpha receptor family, is
constitutively expressed by cells of hematopoietic and non- hematopoietic
origin, including fibroblasts. Signaling through this receptor molecule
regulates inflammatory cytokine secretion by many cell types. Based on the
recently described cytokine secretory heterogeneity of fibroblast cell
subsets, we hypothesized that secretion of inflammatory cytokines by
gingival fibroblast cultures may be dictated by the existence of
differential proportions of cytokine- secreting subpopulations which
express high levels of CD40. After examining a large number of gingival
fibroblast (GF) cultures we find that the frequency of IL-6- and
IL-8-secreting cells mirrors the frequency of cells expressing high levels
of CD40 in these cultures. In addition, we demonstrate a direct functional
relationship between CD40 expression and IL-6 or IL-8 secretion by showing
that ligation of this molecule on GF, and CD40+ fibroblast subsets in
particular, up- regulates secretion of these cytokines in vitro.
相似文献
60.