全文获取类型
收费全文 | 19169篇 |
免费 | 1448篇 |
国内免费 | 1732篇 |
专业分类
22349篇 |
出版年
2024年 | 67篇 |
2023年 | 284篇 |
2022年 | 504篇 |
2021年 | 669篇 |
2020年 | 557篇 |
2019年 | 851篇 |
2018年 | 797篇 |
2017年 | 475篇 |
2016年 | 536篇 |
2015年 | 701篇 |
2014年 | 1285篇 |
2013年 | 1385篇 |
2012年 | 918篇 |
2011年 | 1261篇 |
2010年 | 929篇 |
2009年 | 988篇 |
2008年 | 988篇 |
2007年 | 1115篇 |
2006年 | 964篇 |
2005年 | 852篇 |
2004年 | 714篇 |
2003年 | 593篇 |
2002年 | 577篇 |
2001年 | 371篇 |
2000年 | 357篇 |
1999年 | 323篇 |
1998年 | 369篇 |
1997年 | 270篇 |
1996年 | 275篇 |
1995年 | 285篇 |
1994年 | 219篇 |
1993年 | 198篇 |
1992年 | 190篇 |
1991年 | 170篇 |
1990年 | 141篇 |
1989年 | 116篇 |
1988年 | 112篇 |
1987年 | 95篇 |
1986年 | 62篇 |
1985年 | 107篇 |
1984年 | 155篇 |
1983年 | 120篇 |
1982年 | 135篇 |
1981年 | 59篇 |
1980年 | 52篇 |
1979年 | 51篇 |
1978年 | 40篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
911.
912.
目的:观察结直肠癌组织中活化转录因子2(ATF2)和活化转录因子3(ATF3)的表达并分析其表达的临床病理意义。方法:收集结直肠癌病例,明确其病理诊断并收集临床资料,应用免疫组织化学SP法检测活化转录因子2和活化转录因子3蛋白的表达。结果:ATF2在癌旁肠组织、腺瘤、腺癌组的阳性表达率分别为38%,32%,64%,差异有统计学意义,其中癌旁肠组织、腺瘤分别与腺癌有显著性差异。ATF3在癌旁肠组织、腺瘤、腺癌组的阳性表达率分别为56%,44%,52%,差异无统计学意义。ATF2表达与浸润肠壁深度,淋巴结转移有关,而与肿块大小、部位、分化程度无关。ATF3表达与肿块直径、浸润肠壁深度,而与淋巴结转移、部位、分化程度无关。结论:ATF2与结直肠癌反生和发展有关,而ATF3与结直肠癌的恶性演进有关。 相似文献
913.
目的:探讨胃转流术后远端肠管黏膜的适应性变化及生长因子的表达情况。方法:将8周龄的Wistar大鼠随机分为对照组、假手术组和胃转流术组,术后8周取吻合口远端肠管行常规病理切片检查,测量肠黏膜厚度和绒毛高度,采用免疫荧光法检测肠粘膜中表皮生长因子(EGF)和胰岛素样生长因子-1(IGF—1)的表达。结果:胃转流术组黏膜厚度(672±39与500±31um,P〈0.01)和绒毛高度(445±19与342±15um,P〈0.01)均显著高于假手术组(P〈0.01),而对照组和假手术组间均无显著差异。与假手术组比较,胃转流术组肠粘膜中EGF和IGF-1的表达显著升高(P〈0.01),而对照组和假手术组间无显著差异。结论:胃转流术后远端肠管粘膜发生适应性增生,同时伴随着EGF和IGF—1表达水平的升高。 相似文献
914.
915.
916.
孙灵芬 《中国微生态学杂志》2007,19(2):190-192
目的检测妊娠高血压综合征患者血清中瘦素、TNF-α的水平,并探讨其与妊高征发病的关系。方法用放射免疫法测定35例妊高征患者外周血中瘦素及TNF-α的水平,并以21例正常晚期妊娠妇女(正常妊娠组)作比较。结果(1)妊高征组血清瘦素水平为(32.9±11.5)ng/ml,明显高于正常妊娠组的(18.9±3.0)ng/ml,P<0.05;轻度妊高征组血清瘦素水平为(22.0±4.8)ng/ml,与正常妊娠组比较,差异无显著性,P>0.05;中、重度妊高征组血清瘦素水平分别为(31.1±5.2)、(41.8±10.9)ng/ml,与轻度妊高征组及正常妊娠组比较,差异有显著性,P均<0.05;轻、中、重妊高征组之间血清瘦素水平差异有显著性(P均<0.05)。(2)妊高征组血清TNF-α水平为(22.7±11.5)fmol/ml,明显高于正常妊娠组的(9.2±2.1)fmol/ml,P<0.05,轻度妊高征组血清TNF-α水平为(11.5±4.1)fmol/ml,与正常妊娠组比较,差异无显著性,P>0.05;中、重度妊高征组血清TNF-α水平分别为(19.5±7.4)、(32.9±8.3)fmol/ml,与轻度妊高征组及正常妊娠组比较,差异有显著性(P均<0.05);轻、中、重妊高征组之间血清TNF-α水平差异有显著性(P均<0.05)。(3)妊高征组血清瘦素水平与TNF-α水平呈正相关(分别为r=0.56,P<0.01)。结论妊高征患者血清TNF-α水平增高可能是导致血清瘦素水平升高的原因之一。 相似文献
917.
Immunohistochemical analysis of formalin-fixed paraffin-embedded tissues can be challenging due to potential modifications
of protein structure by exposure to formalin. Heat-induced antigen retrieval techniques can reverse reactions between formalin
and proteins that block antibody recognition. Interactions between antibodies and antigens are further enhanced by microwave
irradiation, which has simplified immunohistochemical staining protocols. In this report, we modify a technique for antigen
retrieval and immunofluorescent staining of formalin-fixed paraffin-embedded tissues by showing that it works well with several
antibodies and buffers. This microwave-assisted method for antigen retrieval and immunofluorescent staining eliminates the
need for blocking reagents and extended washes, which greatly simplifies the protocol allowing one to complete the analysis
in less than 3 h. 相似文献
918.
Neurotrophins are usually viewed as secreted proteins that control long-term survival and differentiation of neurons. However,
recent studies have established that among the most important functions of neurotrophins is their capacity to regulate synaptic
functions and plasticity. When altering synaptic function, neurotrophins are able to produce two types of outcomes, an immediate
effect on synaptic transmission and long-term control of synaptic structure and function. The first effect occurs within seconds
or minutes after the neurotrophic factor has been applied and usually involves acute modification of synaptic transmission.
The second effect takes hours and days, as protein synthesis is required to complete the structural changes. Neurotrophins
and their receptors are expressed within the neuromuscular system, making these agents ideal candidates for the short-and
long-term regulation of skeletal muscle function. For instance, neurotrophins can alter neuromuscular function acutely, by
modulating the amount of neurotransmitter released with each nerve impulse, or chronically, by changing postsynaptic properties
or the content and size of synaptic vesicles. It is obvious that the effects of neurotrophins depend on the specific neurotrophin
involved (four neurotrophins have been found in mammals; these are nerve growth factor, brain-derived neurotrophic factor,
and neurotrophins-3 and-4) and on the specific synapse being studied. Growing evidence highlights the role of neurotrophins
in the development and function of neuromuscular synapses. This review will examine the role of neurotrophins in the regulation
of neuromuscular transmission.
Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 327–337, July–October, 2007. 相似文献
919.
920.
Lv K Guo Y Zhang Y Wang K Jia Y Sun S 《Biochemical and biophysical research communications》2008,374(1):101-105
The biological mechanism of a recent discovered association of type 2 diabetes with the ACAA-insertion/deletion polymorphism at the 3′UTR of the IGF2R gene has remained unclear. A very recently emerging novel polymorphic control layer by microRNAs (miRNAs) makes it possible to elucidate this issue. In this study, a prediction by web tools MicroInspector and miRanda demonstrated that DNA sequence polymorphism (DSPs) ACAA-insertion/deletion in IGF2R 3′UTR is located within the hsa-miR-657 and hsa-miR-453 binding sites. And luciferase reporter assay revealed that hsa-miR-657 acts directly at the 3′UTR of the IGF2R. Furthermore, ACAA-deletion exerted a further repression compared with ACAA-insertion, indicating that hsa-miR-657 regulates IGF2R gene expression in a polymorphic control manner. Importantly, we also demonstrated that hsa-miR-657 can translationally regulate the IGF2R expression levels in Hep G2 cells. Thus, our findings testify the possibility that the ACAA-insertion/deletion polymorphism may result in the change of IGF2R expression levels at least in part by hsa-miR-657-mediated regulation, contributing to the elucidation for the pathogenesis of type 2 diabetes and raise the possibility that miRNAs or in combination with functional DNA sequence polymorphism may be valuable in the treatment of human type 2 diabetes. 相似文献