全文获取类型
收费全文 | 1850篇 |
免费 | 77篇 |
国内免费 | 50篇 |
出版年
2023年 | 23篇 |
2022年 | 35篇 |
2021年 | 50篇 |
2020年 | 52篇 |
2019年 | 50篇 |
2018年 | 69篇 |
2017年 | 49篇 |
2016年 | 63篇 |
2015年 | 77篇 |
2014年 | 166篇 |
2013年 | 123篇 |
2012年 | 91篇 |
2011年 | 120篇 |
2010年 | 85篇 |
2009年 | 87篇 |
2008年 | 102篇 |
2007年 | 70篇 |
2006年 | 85篇 |
2005年 | 77篇 |
2004年 | 78篇 |
2003年 | 46篇 |
2002年 | 39篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 24篇 |
1998年 | 25篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 16篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1966年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有1977条查询结果,搜索用时 453 毫秒
941.
942.
摘要 目的:探讨硫酸镁联合小剂量阿司匹林治疗子痫前期效果及子宫动脉血流、胎盘血管内皮生长因子(VEGF)、基质金属蛋白酶-9(MMP-9)表达影响研究。方法:选择2019年6月-2021年1月在我院接受治疗的125例子痫前期患者,采用随机数表法分为试验组(n=63)和对照组(n=62)。对照组给硫酸镁治疗,试验组在对照组的基础上联合小剂量阿司匹林治疗。比较两组临床疗效、子宫动脉血流、胎盘VEGF、MMP-9、血压水平变化情况及妊娠不良结局发生情况。结果:治疗后,两组总有效率比较差异显著(P<0.05);治疗前,试验组和对照组子宫动脉指标水平比较无显著差异;治疗后,试验组和对照组RI、PI及S/D水平均随着时间的推移而升高,且试验组均高于对照组,差异显著(P<0.05);治疗前,试验组和对照组胎盘VEGF、MMP-9水平比较无显著差异;治疗后,试验组和对照组胎盘VEGF、MMP-9水平均随着时间的推移而升高,且试验组均高于对照组,差异显著(P<0.05);治疗前,试验组和对照组血压水平比较无显著差异;治疗后,试验组和对照组血压水平均随着时间的推移而降低,且试验组均低于对照组,差异显著(P<0.05);试验组胎儿窘迫、宫缩乏力及新生儿窒息发生率均显著低于对照组,差异显著(P<0.05)。结论:在子痫前期中应用硫酸镁联合小剂量阿司匹林治疗疗效显著,可有效改善患者子宫动脉血流、胎盘VEGF、MMP-9水平。 相似文献
943.
摘要 目的:探血清铁蛋白(SF)及超氧化物歧化酶(sod)水平与2型糖尿病患者小纤维神经病变的关系。方法:选择2017年6月至2019年12月我院接诊的120例2型糖尿病患者,根据病变发生情况分为病变组67例,未发生病变53例作为对照组,分析血清铁蛋白(SF)及sod在其中的表达及其预测小纤维神经病变的价值。结果:病变组铁蛋白(SF)水平显著高于对照组,sod水平显著低于对照组,差异显著(P<0.05);ROC结果显示,铁蛋白(SF)预测2型糖尿病患者小纤维神经病变的AUC为0.924,95%CI为0.892~0.957,截断值为223.407 ng/mL ;sod预测2型糖尿病患者小纤维神经病变的AUC为0.96,95%CI为0.944~0.987,截断值为126.862 U/mL;联合预测2型糖尿病患者小纤维神经病变的AUC为0.993,95%CI为0.986~1.000,单独检测分别和联合检测曲线下面积比较均具有显著差异,联合检测的特异度、准确度分别为94.26%、95.16%。结论:在2型糖尿病小纤维神经病变患者中血清铁蛋白(SF)及sod的表达异常,对于疾病的进展有诊断意义,临床应给与关注。 相似文献
944.
《遗传学报》2021,48(7):571-581
Small cell lung cancer (SCLC) is the most aggressive lung cancer with high heterogeneity.Mouse SCLC cells derived from the Rb1~(L/L)/Trp53~(L/L)(RP) autochthonous mouse model grew as adhesion or suspension in cell culture,and the adhesion cells are defined as non-neuroendocrine (non-NE) SCLC cells.Here,we uncover the heterogenous subpopulations within the non-NE cells and referred to them as mesenchymallike (Mes) and epithelial-like (Epi) SCLC cells.The Mes cells have increased capability to form colonies in soft agar and harbored stronger metastatic capability in vivo when compared with the Epi cells.Gene Set Enrichment Analysis reveals that the transforming growth factor (TGF)-β signaling is enriched in the Mes cells.Importantly,inhibition of the TGF-β signaling through ectopic expression of dominant-negative Tgfbr2(Tgfbr2-DN) or treatment with Tgfbr1 inhibitor SD-208 consistently abrogates tumor metastasis in nude mouse allograft assays.Moreover,genetic deletion of Tgfbr2 or Smad4,the key components of the TGF-β signaling pathway,dramatically attenuates SCLC metastasis in the RP autochthonous mouse model.Collectively,our results uncover the high heterogeneity in non-NE SCLC cells and highlight an important role of TGF-β signaling in promoting SCLC metastasis. 相似文献
945.
Caidong Liu Hongling Chen Tong Sun Haibo Wang Baoan Chen Xuerong Wang 《Translational oncology》2021,14(5)
Circulating cancer cells (CTCs) can serve as a non-invasive liquid biopsy and provide opportunities for early cancer diagnosis and evaluation. However, the value of CTCs for diagnosis or prognosis of small pulmonary nodules (SPNs) is unclear. Fifty-three patients diagnosed with SPNs with a diameter less than 30 mm by CT examination were enrolled in the study. The CTC numbers, CT examination features, serum tumor marker concentrations, and histopathological characteristics were analyzed. Centromere probe 8 (CEP8) was used as a marker for CTC identification. The CTC numbers were significantly different in patients with malignant and benign SPNs and with early (0/Ⅰa) and advanced (Ⅰb/Ⅱ/Ⅲ) lung cancer stages. ROC analysis showed that the CTC numbers was effective on malignant SNP diagnosis. The combined use of CTCs and the density features of the nodules determined by CT further improved the overall screening, the diagnostic effectiveness for malignant SNPs, and determination of the pTNM (≤Ia vs.>Ia) stage. The CT morphology revealed that large, single, and solid SPNs were associated with significant CTC numbers and the CTC numbers were correlated with malignant histopathology. Using CEP8 as a marker resulted in detection of more CTC numbers in 22 patient samples triple stained for CEP8, EpCAM, and CKs. The CTCs determined by CEP8-positive staining could serve as potential screening and diagnostic markers for malignant SPNs. 相似文献
946.
RNA polymerase II carboxyl-terminal domain (pol II CTD) phosphatases are a newly emerging family of phosphatases that are members of DXDX (T/V). The subfamily includes Small CTD phosphatases, like SCP1, SCP2, SCP3, TIMM50, HSPC129 and UBLCP. Extensive study of SCP1 has elicited the diversified roles of the small C terminal domain phosphatase. The SCP1 plays a vital role in various biological activities, like neuronal gene silencing and preferential Ser5 dephosphorylation, acts as a cardiac hypertrophy inducer with the help of its intronic miRNAs, and has shown a key role in cell cycle regulation. This short review offers an explanation of the mechanism of action of small CTD phosphatases, in different biological activities and metabolic processes. [BMB Reports 2014; 47(4): 192-196] 相似文献
947.
Expression and purification of a small heat shock protein from the plant pathogen Xylella fastidiosa 总被引:2,自引:0,他引:2
Azzoni AR Tada SF Rosselli LK Paula DP Catani CF Sabino AA Barbosa JA Guimarães BG Eberlin MN Medrano FJ Souza AP 《Protein expression and purification》2004,33(2):297-303
The small heat shock proteins (smHSPs) belong to a family of proteins that function as molecular chaperones by preventing protein aggregation and are also known to contain a conserved region termed alpha-crystallin domain. Here, we report the expression, purification, and partial characterization of a novel smHSP (HSP17.9) from the phytopathogen Xylella fastidiosa, causal agent of the citrus variegated chlorosis (CVC). The gene was cloned into a pET32-Xa/LIC vector to over-express the protein coupled with fusion tags in Escherichia coli BL21(DE3). The expressed HSP17.9 was purified by immobilized metal affinity chromatography (IMAC) and had its identity determined by mass spectrometry (MALDI-TOF). The correct folding of the purified recombinant protein was verified by circular dichroism spectroscopy. Finally, the HSP17.9 protein also proved to efficiently prevent induced aggregation of insulin, strongly indicating a chaperone-like activity. 相似文献
948.
Gillette WK Esposito D Taylor TE Hopkins RF Bagni RK Hartley JL 《Protein expression and purification》2011,76(2):238-247
Purifying proteins from recombinant sources is often difficult, time-consuming, and costly. We have recently instituted a series of improvements in our protein purification pipeline that allows much more accurate choice of expression host and conditions and purification protocols. The key elements are parallel cloning, small scale parallel expression and lysate preparation, and small scale parallel protein purification. Compared to analyzing expression data only, results from multiple small scale protein purifications predict success at scale-up with greatly improved reliability. Using these new procedures we purified eight of nine proteins from xenotropic murine leukemia virus-related virus (XMRV) on the first attempt at large scale. 相似文献
949.
目的:研究ADE模型下小约化体积膜泡的形状。方法:应用数值计算方法中的打靶法,运用Mathematica 7.0软件进行编程。结果:在ADE模型下,计算得到了一系列小约化体积的膜泡的形状,解决了已往小约化体积区域内不存在稳定膜泡的问题。结论:研究表明,在ADE模型下通过适当的边界条件把黏附双层区域的接触势能考虑进去,数值计算结果与实验上的非常相似。 相似文献
950.
The island rule states that small mammals isolated on islands have the evolutionary tendency to become larger, while large
mammals tend to become smaller. However, the underlying mechanisms and life history consequences of these insular shifts in
body size still remain speculative. The aim of this study was to investigate whether an arboreal mammal, the edible dormouse
(Glis glis), showed shifts in body size when inhabiting isolated forest fragments. We analysed a data set of 541 individuals captured
between 2005 and 2010 in four different forest fragments and one continuous forest, which served as a reference area. Sex,
age, body mass, and size of all individuals were known. We used linear mixed-effect models to investigate whether individuals
differed in their body size and mass between forest fragments and continuous forest. Our study revealed that edible dormice
inhabiting forest fragments were significantly larger and heavier than individuals in the continuous forest, in accordance
with patterns described by the island rule for small mammals. Because edible dormice frequently use nest boxes to rest during
the day and to rear offspring, the life history strategies of this rodent can be easily investigated under evolutionary relevant
conditions in the field. Thus the edible dormouse represents an excellent model organism for studying the mechanisms underlying
shifts in body size as a response to habitat fragmentation and to investigate the consequences of these shifts on their life
history strategies. 相似文献