全文获取类型
收费全文 | 10987篇 |
免费 | 999篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 82篇 |
儿科学 | 277篇 |
妇产科学 | 281篇 |
基础医学 | 1597篇 |
口腔科学 | 278篇 |
临床医学 | 1272篇 |
内科学 | 2517篇 |
皮肤病学 | 96篇 |
神经病学 | 835篇 |
特种医学 | 514篇 |
外科学 | 1299篇 |
综合类 | 191篇 |
一般理论 | 6篇 |
预防医学 | 1323篇 |
眼科学 | 108篇 |
药学 | 752篇 |
中国医学 | 4篇 |
肿瘤学 | 583篇 |
出版年
2021年 | 155篇 |
2020年 | 94篇 |
2019年 | 144篇 |
2018年 | 163篇 |
2017年 | 107篇 |
2016年 | 157篇 |
2015年 | 158篇 |
2014年 | 270篇 |
2013年 | 343篇 |
2012年 | 462篇 |
2011年 | 538篇 |
2010年 | 321篇 |
2009年 | 275篇 |
2008年 | 513篇 |
2007年 | 479篇 |
2006年 | 475篇 |
2005年 | 447篇 |
2004年 | 379篇 |
2003年 | 355篇 |
2002年 | 348篇 |
2001年 | 332篇 |
2000年 | 323篇 |
1999年 | 301篇 |
1998年 | 157篇 |
1997年 | 135篇 |
1996年 | 144篇 |
1995年 | 120篇 |
1994年 | 85篇 |
1993年 | 92篇 |
1992年 | 272篇 |
1991年 | 253篇 |
1990年 | 253篇 |
1989年 | 237篇 |
1988年 | 238篇 |
1987年 | 204篇 |
1986年 | 228篇 |
1985年 | 205篇 |
1984年 | 192篇 |
1983年 | 182篇 |
1982年 | 131篇 |
1981年 | 106篇 |
1980年 | 92篇 |
1979年 | 158篇 |
1978年 | 126篇 |
1977年 | 111篇 |
1976年 | 94篇 |
1974年 | 110篇 |
1973年 | 105篇 |
1972年 | 88篇 |
1968年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
L S Wicker R C Boltz V Matt E A Nichols L B Peterson N H Sigal 《European journal of immunology》1990,20(10):2277-2283
The effects of the immunosuppressants cyclosporin A (CsA), FK506 and rapamycin have been compared using murine B cells activated with a variety of mitogens. FK506 is a macrolide antibiotic that has been recently shown to inhibit T cell activation by a mechanism that appears similar to that of CsA. Rapamycin is a macrolide structurally related to FK506 whose mechanism of T cell suppression appears to be distinct from that of FK506 and CsA. While CsA and FK506 were found to preferentially inhibit B cell activation caused by stimuli which induce a rise in intracellular calcium, rapamycin partially inhibited activation by all stimuli tested, including those which are not associated with a calcium flux. All three compounds were found to inhibit cell cycle progression within the G1 phase; however, the rapamycin-sensitive event within G1 was completed earlier than the G1 events inhibited by CsA and FK506. In addition, inhibition of anti-IgM-activated B cells with CsA and FK506, but not with rapamycin, resulted in cell death. These data suggest that although CsA, FK506 and rapamycin are all inhibitors of B cell activation, the inhibitory activity of rapamycin can be clearly distinguished from that of CsA and FK506. Although the suppressive effects of CsA and FK506 on B cell proliferation were nearly identical in this study, their biological activities were distinguishable since FK506, but not CsA, could antagonize rapamycin-mediated suppression. 相似文献
103.
Mechanical properties of dilated human ascending aorta 总被引:3,自引:0,他引:3
Okamoto RJ Wagenseil JE DeLong WR Peterson SJ Kouchoukos NT Sundt TM 《Annals of biomedical engineering》2002,30(5):624-635
Dilation of the ascending aorta, associated with Marfan Syndrome, bicuspid aortic valve, or advanced age, may lead to aortic dissection and rupture. Mathematical models can be used to assess the relative importance of increased wall stresses and decreased strength in these mechanical failures. To obtain needed inputs for such models, mechanical properties of dilated human ascending aorta were measured in vitro. Specimens for opening angle, biaxial elastic, and uniaxial circumferential strength tests were cut from excised tissue obtained from 54 patients (age 18–81 years) undergoing elective aortic graft replacement surgery. Opening angle was significantly greater in patients older than 50 years (262°±76°, n=21) compared to younger patients (202°±70°, n=13 All biaxial elastic specimens n=40 exhibited nonlinear stress-strain behavior. Rapid increases in circumferential and axial stresses occurred at lower strains in the older patient group than in the younger. Mean strength was significantly lower in older patients (1.35±0.37 MPa, n=14) than younger (2.04 ± 0.46 MPa, n=11, age <50 years). These changes in mechanical properties suggest that age may influence the risk of aortic dissection or rupture of dilated ascending aorta. © 2002 Biomedical Engineering Society.
PAC2002: 8719Rr, 8719Hh 相似文献
104.
105.
Few studies have characterized or compared the pathologic features of bone marrow involvement by extranodal (EMZL), splenic (SMZL), and nodal marginal zone lymphoma (NMZL). We evaluated 45 bone marrow biopsy specimens from 39 patients with marginal zone lymphomas. As previously reported, bone marrow involvement was frequent (100%) in patients with SMZL. We also identified lymphoma involving bone marrow in 11 (44%) of 25 patients with EMZL and 1 of 2 patients with NMZL. The patterns of infiltration were mixed in all groups; however, the extent of involvement was greater in SMZL than in EMZL. In addition, germinal centers were present in bone marrow biopsy specimens involved by lymphoma in 4 patients with SMZL. Intrasinusoidal infiltration was common (10/12 [83%]) and prominent in patients with bone marrow involvement by SMZL, but was not invariably present. Intrasinusoidal infiltration of the bone marrow also was not specific for SMZL since similar infiltrates, although subtle, also were found in patients with other small B-cell lymphoproliferative disorders, including 6 (55%) of 11 patients whose bone marrow samples were infiltrated by EMZL. 相似文献
106.
Annika?E?StenbergEmail author Lisskulla?Sylvén Carl?GM?Magnusson Malou?Hultcrantz 《Journal of negative results in biomedicine》2004,3(1):6
Disturbances in the immune system has been described in Turner syndrome, with an association to low levels of IgG and IgM
and decreased levels of T- and B-lymphocytes. Also different autoimmune diseases have been connected to Turner syndrome (45,
X), thyroiditis being the most common. 相似文献
107.
E G Levine S Juneja D Arthur O M Garson J L Machnicki G Frizzera P Ironside I Cooper D D Hurd B A Peterson 《Genes, chromosomes & cancer》1990,1(4):270-280
The examination of sequential karyotypes in hematologic disorders has demonstrated that karyotypic changes are often associated with concurrent changes in clinical behavior. Acquired abnormalities that recur among different patients may also suggest genomic areas important to tumor progression. We therefore examined sequential karyotypes in 21 patients with non-Hodgkin lymphoma (NHL). Sixteen of the 21 karyotypes demonstrated changes, including the majority of 6 small lymphocytic, 11 follicular, and 4 intermediate and high-grade diffuse lymphomas. The t(14;18)(q32;q21) occurred in ten initial karyotypes was retained in all cases. The band most frequently affected by newly acquired abnormalities was 14q32 (n = 5); chromosomes 1 and 2 (n = 5, each), and the 17p arm (n = 4) were also commonly affected. The acquired deletion of all or part of 17p appeared to be associated with a poor prognosis. Histologic transformation and karyotypic change did not correlate. This study of sequential karyotypes in NHL 1) confirms the primary importance of the t(14;18), 2) suggests that the 14q32 band is involved frequently in both primary and secondary cytogenetic events, and 3) suggests other genomic regions of potential significance to progression. 相似文献
108.
109.
J W Peterson S S Saini W D Dickey G R Klimpel J S Bomalaski M A Clark X J Xu A K Chopra 《Infection and immunity》1996,64(6):2137-2143
The mechanism of cholera toxin (CT)-stimulated arachidonate metabolism was evaluated. CT caused rapid in vitro synthesis of prostaglandin E2 (PGE2) in murine smooth muscle-like cells (BC3H1), reaching maximal levels within 3 to 4 min. In comparison, cyclic AMP (cAMP) levels were unchanged, and addition of dibutyryl cAMP did not affect PGE2 synthesis. CT-induced PGE2 synthesis was prevented by actinomycin D or cycloheximide, indicating a need for de novo protein synthesis. Northern blot analysis of total RNA from BC3H1 cells revealed that exposure to CT resulted in an increase in abundance of mRNA encoding phospholipase A2 (PLA2)-activating protein (PLAP). PLAP is a regulatory protein that increases the enzymatic activity of cellular PLA(2), which in turn causes increased hydrolysis of arachidonate from membrane phospholipids. Furthermore, CT evoked the accumulation of PLAP mRNA in J774 (murine monocyte/macrophage) and Caco-2 (human intestinal epithelial) cells in vitro, but the responses were more delayed than that of BC3H1 cells. A protein band of approximately 35 kDa, which corresponded to the size of PLAP, was observed in sodium dodecyl sulfate extracts of Caco-2 cells by Western blot (immunoblot) analysis using affinity-purified antibodies to PLAP synthetic peptides. Synthesis of PLAP protein was increased after 2 h of exposure to CT. Exposure of mouse intestinal loops to either CT or live Salmonella typhimurium for 3 h increased mucosal PLAP mRNA levels. The role of PLAP in CT-induced PGE2 synthesis provides an attractive explanation for the reported suppression of CT-induced intestinal secretion by inhibitors of protein synthesis. 相似文献
110.
A point mutation in the 5' splice site of the dystrophin gene first intron responsible for X-linked dilated cardiomyopathy 总被引:3,自引:4,他引:3
Milasin J; Muntoni F; Severini GM; Bartoloni L; Vatta M; Krajinovic M; Mateddu A; Angelini C; Camerini F; Falaschi A; Mestroni L; Giacca M 《Human molecular genetics》1996,5(1):73-79
X-linked dilated cardiomyopathy (XLDC) is a familial heart disease
presenting in young males as a rapidly progressive congestive heart
failure, without clinical signs of skeletal myopathy. This condition has
recently been linked to the dystrophin gene in some families and deletions
encompassing the genomic region coding for the first muscle exon have been
detected. In order to identify the defect responsible for this disease at
the molecular level and to understand the reasons for the selective heart
involvement, a family with a severe form of XLDC was studied. In the
affected members, no deletions of the dystrophin gene were observed.
Analysis of the muscle promoter, first exon and intron regions revealed the
presence of a single point mutation at the first exon-intron boundary,
inactivating the universally conserved 5' splice site consensus sequence of
the first intron. This mutation introduced a new restriction site for MseI,
which cosegregates with the disease in the analyzed family. Expression of
the major dystrophin mRNA isoforms (from the muscle-, brain- and Purkinje
cell-promoters) was completely abolished in the myocardium, while the
brain- and Purkinje cell- (but not the muscle-) isoforms were detectable in
the skeletal muscle. Immunocytochemical studies with anti- dystrophin
antibodies showed that the protein was reduced in quantity but normally
distributed in the skeletal muscle, while it was undetectable in the
cardiac muscle. These findings indicate that expression of the muscle
dystrophin isoform is critical for myocardial function and suggest that
selective heart involvement in dystrophin- linked dilated cardiomyopathy is
related to the absence, in the heart, of a compensatory expression of
dystrophin from alternative promoters.
相似文献