全文获取类型
收费全文 | 117391篇 |
免费 | 11281篇 |
国内免费 | 9099篇 |
专业分类
耳鼻咽喉 | 987篇 |
儿科学 | 1115篇 |
妇产科学 | 1160篇 |
基础医学 | 13927篇 |
口腔科学 | 1957篇 |
临床医学 | 15826篇 |
内科学 | 17636篇 |
皮肤病学 | 1214篇 |
神经病学 | 6236篇 |
特种医学 | 4440篇 |
外国民族医学 | 78篇 |
外科学 | 11973篇 |
综合类 | 20733篇 |
现状与发展 | 40篇 |
一般理论 | 6篇 |
预防医学 | 7919篇 |
眼科学 | 3347篇 |
药学 | 12238篇 |
95篇 | |
中国医学 | 7076篇 |
肿瘤学 | 9768篇 |
出版年
2024年 | 411篇 |
2023年 | 1973篇 |
2022年 | 4989篇 |
2021年 | 6338篇 |
2020年 | 4750篇 |
2019年 | 4014篇 |
2018年 | 4178篇 |
2017年 | 3716篇 |
2016年 | 3560篇 |
2015年 | 5443篇 |
2014年 | 6666篇 |
2013年 | 5855篇 |
2012年 | 8526篇 |
2011年 | 9411篇 |
2010年 | 5943篇 |
2009年 | 4700篇 |
2008年 | 6049篇 |
2007年 | 6004篇 |
2006年 | 5801篇 |
2005年 | 5868篇 |
2004年 | 3813篇 |
2003年 | 3499篇 |
2002年 | 3007篇 |
2001年 | 2670篇 |
2000年 | 2812篇 |
1999年 | 3010篇 |
1998年 | 2047篇 |
1997年 | 2060篇 |
1996年 | 1586篇 |
1995年 | 1499篇 |
1994年 | 1289篇 |
1993年 | 824篇 |
1992年 | 993篇 |
1991年 | 807篇 |
1990年 | 673篇 |
1989年 | 650篇 |
1988年 | 539篇 |
1987年 | 470篇 |
1986年 | 410篇 |
1985年 | 317篇 |
1984年 | 150篇 |
1983年 | 131篇 |
1982年 | 82篇 |
1981年 | 88篇 |
1980年 | 65篇 |
1979年 | 56篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
941.
Inverted repeats direct repair of adenovirus minichromosome ends 总被引:2,自引:0,他引:2
Adenovirus DNA initiates strand-displacement replication from origins located in identical inverted terminal repetitions (ITRs). Panhandle structures, formed by base pairing between ITRs on the displaced strands, have been proposed as replication intermediates for complementary strand synthesis. We have used a model system, which separates adenovirus replication origin sequences from those involved in panhandle formation, to study the length and sequence integrity of panhandles. By making a series of unidirectional deletion in the panhandle sequence, we show that 31 bp are necessary for panhandle formation. Removal of long stretches of 3'-unpaired nucleotides distal to the panhandle is extremely efficient. Our results argue for the formation of panhandles during adenovirus DNA replication and provide a mechanism for maintaining sequence identity between distantly located inverted repetitions. The size constraint may explain why the adenovirus ITRs are larger than the viral DNA replication origins. 相似文献
942.
Yin Xu Robert W McKenna Jeffrey E Doolittle Christa L Hladik Steven H Kroft 《Applied immunohistochemistry & molecular morphology》2005,13(2):116-123
The clinical and biologic relevance of the t(14;18) and features of germinal center (GC) differentiation in diffuse large B-cell lymphoma (DLBCL) remain controversial. The authors examined the association of t(14;18) with GC-associated markers and clinical features in 44 de novo DLBCLs (22 nodal and 22 primary extranodal). CD10, bcl-2, and bcl-6 were expressed in 50%, 62%, and 54% of cases respectively. There were no significant differences in expression of these markers between nodal and extranodal cases. Coexpression of CD10 and bcl-6 was seen in 12 of 41 cases, and was more frequent in nodal than extranodal DLBCL (9 of 21 vs. 3 of 20; P = 0.05). A CD10+/bcl-6+ phenotype was not significantly associated with bcl-2 expression, stage, complete remission rate, or survival. The t(14;18) was found in 7 of 44 (16%) cases (6 nodal, 1 extranodal; P = 0.09). It was associated with a CD10+/bcl-6+ phenotype (5 of 7 vs. 7 of 27; P = 0.015) and a trend toward more frequent bcl-6 expression (6 of 7 vs. 15 of 34; P = 0.09), but no association with bcl-2 expression, CD10, clinical stage, complete remission, or survival. Among nodal or high-stage (III-IV) DLBCL, cases with the t(14;18) showed a trend toward decreased survival (P = 0.12). 相似文献
943.
Bini TB Gao S Xu X Wang S Ramakrishna S Leong KW 《Journal of biomedical materials research. Part A》2004,68(2):286-295
Tiny tubes with fiber architecture were developed by a novel method of fabrication upon introducing some modification to the microbraiding technique, to function as nerve guide conduit and the feasibility of in vivo nerve regeneration was investigated through several of these conduits. Poly(L-lactide-co-glycolide) (10:90) polymer fibers being biocompatible and biodegradable were used for the fabrication of the conduits. The microbraided nerve guide conduits (MNGCs) were characterized using scanning electron microscopy to study the surface morphology and fiber arrangement. Degradation tests were performed and the micrographs of the conduit showed that the degradation of the conduit is by fiber breakage indicating bulk hydrolysis of the polymer. Biological performances of the conduits were examined in the rat sciatic nerve model with a 12-mm gap. After implantation of the MNGC to the right sciatic nerve of the rat, there was no inflammatory response. One week after implantation, a thin tissue capsule was formed on the outer surface of the conduit, indicating good biological response of the conduit. Fibrin matrix cable formation was seen inside the MNGC after 1 week implantation. One month after implantation, 9 of 10 rats showed successful nerve regeneration. None of the implanted tubes showed tube breakage. The MNGCs were flexible, permeable, and showed no swelling apart from its other advantages. Thus, these new poly(L-lactide-co-glycolide) microbraided conduits can be effective aids for nerve regeneration and repair and may lead to clinical applications. 相似文献
944.
Cerebral ischemia causes an excess release of glutamate, which can injure neurons. The striatum is one of the important regions vulnerable to hypoxia and ischemia. Using push–pull perfusion technique, we investigated the regulatory role of γ-aminobutyric acid (GABA) and its receptors in modifying the amount of glutamate in rat striatum with ischemia. Perfusion with exogenous GABA (1 mM) inhibited cerebral ischemia-induced glutamate release by as much as 47%. We further characterized relative roles of subtype receptors of GABA on glutamate release by using pharmacological tools. While baclofen (500 μM), a GABAB receptor agonist, suppressed ischemia-induced glutamate release by 52%, GABAB receptor antagonist saclofen (500 μM) failed to produce a significant increase of glutamate release. The GABAA receptor agonist muscimol (500 μM) also reduced by 38% the release of glutamate induced by cerebral ischemia but the GABAA receptor antagonist bicuculline (500 μM) had very little effect. The present study demonstrates that the excessive release of glutamate or the overly activated glutamate receptor, triggered by cerebral ischemia, can be down-regulated by exogenous GABA or by increased activity of GABA receptors, especially the presynaptic GABAB receptors, which might be one of the important mechanisms to protect against striatum neuronal damage from over stimulation by excessive glutamate during ischemia. 相似文献
945.
946.
Todd S Xu J Millar BC Moore JE Crowe M Raoult D Harrison T Hill C Douglas J 《British journal of biomedical science》2004,61(4):190-193
Members of the genus Bartonella are increasingly recognised as a cause of culture-negative endocarditis, particularly in those patients with underlying risk factors (e.g., homelessness and alcoholism (B. quintana) or valvulopathy and cat ownership (B. henselae). The aortic and mitral-valves are most commonly involved. Here, a case is reported of culture-negative right-sided endocarditis, without any of the above risk factors, due to Bartonella sp. in a 69-year-old man who presented with acute renal failure. The diagnosis was made using a broad-range 16S rRNA polymerase chain reaction (PCR) technique and direct automated sequencing on a peripheral blood sample, which was subsequently confirmed serologically. A review of the literature on Bartonella endocarditis is also presented. Molecular laboratory methods using peripheral blood or blood cultures may be very useful in the diagnosis of causal agents in culture-negative endocarditis and add further support to the recently inclusion of molecular (PCR) diagnosis, as a major Duke's criterion, for the diagnosis of infective endocarditis. 相似文献
947.
Inborn errors of metabolism discovered in Asian department of pediatrics and mental retardation research center 总被引:6,自引:0,他引:6
Zhang C Xu K Dave UP Wang Y Matsumoto I 《Journal of chromatography. B, Biomedical sciences and applications》2000,746(1):41-49
To heighten the effectiveness of chemical diagnosis for inborn errors of metabolism (IEM) using urease pretreatment and GC-MS analysis, a sample collection and transportation method was contrived. The resulting "filter paper set" allows simple urine collection and transportation, and enables anyone from anywhere to receive the GC-MS analysis without the limitations of place or time. Using filter paper sets, high-risk screening of undiagnosed children or mentally retarded children with unknown cause was conducted in cooperation with hospitals and universities in several Asian countries. During 8 months 203 patients from China and India were analyzed and 20 cases of IEM were chemically diagnosed. These diagnoses greatly contributed to the treatment of children with intractable diseases who lived in Asian countries where analytical techniques and facilities for IEM were not sufficient. 相似文献
948.
The role of IL-10 in the regulation of ocular autoimmune disease was
studied in experimental autoimmune uveoretinitis (EAU) elicited in mice by
immunization with the retinal antigen interphotoreceptor retinoid binding
protein. IL-10-deficient mice were susceptible to EAU, indicating that
pathogenesis can occur without presence of IL-10. Treatment of normal mice
with IL-10 for 5 days after uveitogenic immunization ameliorated subsequent
EAU scores, and down-regulated antigen-specific production of tumor
necrosis factor-alpha and IFN- gamma. A concomitant treatment with IL-4
further reduced disease, and resulted in emergence of antigen-specific IL-4
and IL-10 production, as well as in enhancement of the IgG1 antibody
isotype. IL-4 by itself was not protective. Only IL-10, but not IL-4, was
able to inhibit the function of differentiated uveitogenic T cells in
culture. Expression of mRNA for Th1 and Th2 cytokines in the eye during the
course of EAU showed that while a Th1 pattern predominated early, IL-10
mRNA expression coincided with down-regulation of the Th1 response and
resolution of EAU. Systemic neutralization of IL-10 during the expression
phase of EAU resulted in elevated disease scores. Our results suggest that
endogenous IL-10 limits expression of EAU and may play a role in the
natural resolution of disease. The data further suggest that exogenous
IL-10 may be useful in therapeutic control of autoimmune uveitis. While
IL-10 by itself is sufficient to suppress Th1 effector development and
function, a concomitant administration of IL-4 is required to shift the
autoimmune response towards a non-pathogenic Th2 pathway.
相似文献
949.
应用制霉菌素穿孔全细胞电压钳技术.在急性分离的大鼠骶髓后连合核(SDCN)神经元上,研究抑制性氨基酸诱导的反应的电生理学和药理学特性。当钳制电压为-40mV时,γ-氨基丁酸(GABA)、甘氨酸(Gly)和牛磺酸(Tau)均诱导产生内向电流。它们的EC50值分别是GABA5.2×10-5M,Gly4.0×10-5M及Tau1.6×10-4M。其Hill系数分别为GABA1.21,Gly1.27和Tau1.23。所有这些电流均在膜电位为-1.8mV左右时翻转。此外.Tau和Gly反应问还存在很强的交叉脱敏。结果提示,GABAA,Gly和Tau作为递质,通过受体Cl-通道复合体.在调节SDCN社经元伤害性传递中可能有重要作用。 相似文献
950.
本文采用放射性同位素标记的方法研究了嵌段聚醚型聚氨酯在纯纤维蛋白原溶液中和稀释血浆中的表面纤维蛋白原吸附性规律,考察了聚醚型聚氨酯的特性粘数及溶液体系中的NaCl浓度对材料表面纤维蛋白原吸附性的影响,结果表明,随着聚合物特性粘数的增大,材料表面的纤维蛋白原吸附量呈降低的趋势;溶液体系中盐浓度的降低导致纤维蛋白原凝固性增强,在纯纤维蛋白原溶液中,材料表面纤维蛋白原的吸附量相应增多,而在稀释血浆中,纤维蛋白原的吸附量相应减少,在达到最低值后又有上升的趋向,表明纤维蛋白原在材料表面的吸附还受血浆中其它大分子的影响。 相似文献