首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5478篇
  免费   479篇
  国内免费   445篇
  6402篇
  2024年   12篇
  2023年   82篇
  2022年   191篇
  2021年   321篇
  2020年   206篇
  2019年   232篇
  2018年   261篇
  2017年   175篇
  2016年   207篇
  2015年   362篇
  2014年   355篇
  2013年   460篇
  2012年   515篇
  2011年   470篇
  2010年   251篇
  2009年   249篇
  2008年   281篇
  2007年   246篇
  2006年   188篇
  2005年   179篇
  2004年   136篇
  2003年   137篇
  2002年   107篇
  2001年   121篇
  2000年   85篇
  1999年   106篇
  1998年   60篇
  1997年   48篇
  1996年   38篇
  1995年   42篇
  1994年   35篇
  1993年   25篇
  1992年   41篇
  1991年   25篇
  1990年   26篇
  1989年   25篇
  1988年   19篇
  1987年   15篇
  1986年   20篇
  1985年   20篇
  1984年   7篇
  1983年   9篇
  1982年   8篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1971年   1篇
排序方式: 共有6402条查询结果,搜索用时 15 毫秒
211.
212.
Lipoprotein(a) [Lp(a)], a low-density lipoprotein-like particle, is recognized as an independent risk factor for atherosclerosis, cardiovascular diseases, and diabetic vascular diseases. Our recent studies revealed that the single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptors (PPARα/δ/γ) gene are involved in the regulation of lipid storage and metabolism. In order to investigate the relationships between the SNPs of PPARα/γ gene and plasma levels of Lp(a), 644 participants were randomly selected from Chinese Han population in the present study. As the results shown, Lp(a) was significantly associated with L162V (rs1800206) in PPARα. Compared with those subjects with widetype (LL), significantly higher Lp(a) concentration was determined in the individuals with mutant (LV + VV) (mean difference: 49.07 mg/l, 95 % CI 23.32–74.82 mg/l, p = 0.0002). Moreover, with generalized multifactor dimensionality reduction analysis, our present results indicated that there was a significant association between plasma Lp(a) level and gene–gene interaction among the polymorphisms rs1800206, rs135539 in PPARα and rs10865710, rs1805192, and rs4684847 in PPARγ. Therefore, our presented study indicated that PPARα/γ polymorphisms should be involved in the regulation of plasma Lp(a) in independently and/or in an interactive manner, suggesting that PPARα/γ gene may influence the risk of hypertension, cardiovascular diseases, and dyslipidemia by regulating Lp(a) level.  相似文献   
213.
Liu  Wen-Shen  Zheng  Hong-Xiang  Liu  Chang  Guo  Mei-Na  Zhu  Shi-Chen  Cao  Yue  Qiu  Rong-Liang  Morel  Jean Louis  van der Ent  Antony  Tang  Ye-Tao 《Plant and Soil》2021,461(1-2):565-578
Plant and Soil - Dicranopteris linearis is a rare earth element (REE), aluminium (Al) and silicon (Si) hyperaccumulator plant which occurs in southern China. To date, there have been no studies on...  相似文献   
214.
215.

Objective

This research aimed to investigate whether glutamate induced spiral ganglion neurons (SGNs) apoptosis through apoptosis inducing factor (AIF) pathway. And verify whether PD150606, a calpain inhibitor could prevent apoptosis by inhibiting cleaving and releasing AIF in mitochondrion.

Methods

SGNs of postnatal days 0-3 were harvested and cultured in dishes. 20 mM Glu, the caspase inhibitor Z-VAD-FMK and calpain inhibitor PD150606 were added into cultured dishes separately. We used optical microscope and immunofluoresence staining to observe cell morphology and AIF distribution, RT-PCR and Westernblot to analyse AIF and calpain expression in SGNs. TUNEL assay was used to test cell apoptosis.

Results

Cell morphology and nuclear translocation of AIF were altered in SGNs by 20 mM Glu treated in vitro. The axon of SGN shortened, more apoptosis SGN were observed and the expression of AIF and calpain were up-regulated in Glu-treated group than the normal one (P<0.05). The same experiments were conducted in 20 mM+PD150606 treated group and 20 mM+Z-VAD-FMK group. Obviously AIF were located from cytoplasm to the nuclear and the expressions of AIF and calpain were down-regulated by PD150606 (P<0.05). Positive cells in TUNEL staining decreased after PD150606 treating. However, Z-VAD-FMK had no influence on AIF, calpain expression or cell apoptosis.

Conclusion

The AIF-related apoptosis pathway is involved in the process of Glu-induced SGN injury. Furthermore, the inhibition of calpain can prevent AIF from releasing the nuclear or inducing SGN apoptosis.  相似文献   
216.
Chromosome 9q34 has been extensively studied and mapped due to the presence of known disease genes, principally tuberous sclerosis 1 (TSC1), in this region. During the course of our mapping of this region we constructed a 555-kb contig beginning approximately 50 kb proximal to the dopamine-beta-hydroxylase (DBH) gene and extending, with one small deletion, distal to the D9S114 marker. The contig consists of 11 P1 clones, four PAC clones, one BAC clone and six cosmid clones and contains 27 new nonpolymorphic STSs. We have found the region to be unstable in P1, PAC and BAC cloning vehicles and have identified several deleted genomic clones. In addition, we have isolated and mapped the 3' portions of three putative genes located within or immediately distal to the DBH gene, including one large gene that runs on the opposite strand to DBH and utilizes portions of two DBH exons. The genomic clones of the contig, cDNAs and new STSs will be useful reagents for the further study and mapping of this region.  相似文献   
217.

Purpose

Dynamic visual acuity (DVA) is a relatively independent parameter for evaluating the ability to distinguish details of a moving target. The present study has been designed to discuss the extent to which age-related cataract impacts DVA in elderly individuals and to determine whether it could be restored after bilateral phacoemulsification combined with intraocular lens implantation surgery.

Methods

Twenty-six elderly cataract patients scheduled for binocular cataract surgery and 30 elderly volunteers without cataract were enrolled in the study. DVA at 15, 30, 60 and 90 degree per second (dps) was assessed, and velocity-dependent visual acuity decreases between consecutive speed levels were calculated.

Results

Compared with the control group, the patient group exhibited significantly worse DVA performance at all speed levels (p<0.001), and the decreases in velocity-dependent visual acuity were more serious in the patient group at the intervals of 0–15 dps (p<0.001), 15–30 dps (p = 0.007) and 30–60 dps (p = 0.008). Postoperatively, DVA performance at every speed level in the patient group clearly improved (p<0.001) and recovered to levels compatible to the control group. The decrease in visual acuity with increasing speed was less pronounced than during the preoperative phase (p0–15 dps = 0.001, p15–30 dps<0.001 and p30–60 dps = 0.001) and became similar to that of the control group. The postoperative visual benefit regarding DVA was more pronounced than the improvement in static visual acuity (p15 dps = 0.001 and p<0.001 at 30 dps, 60 dps and 90 dps).

Conclusions

The impact of age-related cataract on DVA was more severe than its effects on static visual acuity. After cataract surgery, not only static vision of the patients was restored markedly, but also the dynamic vision. DVA could be an important adjunct to the current evaluation system of functional vision, thereby meriting additional attention in clinical assessment.  相似文献   
218.
陈心岭  罗阳 《蛇志》2000,12(3):15-17
目的:观察降纤酶治疗高粘血症患者的临床疗效。方法用生理盐水250ml加降纤酶5u,体重超过65kg和10u,静脉滴注,每天1次,连用3天,第4天停用,第5天开始隔天静脉滴注降纤酶5u或者10u,总量60u。结果降纤酶能明显地降低高粘血症患者的血液粘度、纤维蛋白原、红细胞聚集指数、微循环滞留时间等,同时也能使患者原有临床症状和体征以及微循环得到明显改善,结论降纤酶是治疗高粘血症的有效药物。  相似文献   
219.
清香桂碱D和矮陀陀胺碱A,B的结构   总被引:9,自引:0,他引:9  
本文报道从国产清香桂(Sarcococca ruscifolta)和金丝矮陀陀(Pachysandra axillaria)植物中分得的三个胺碱型新甾体生物碱清香桂碱 D 和矮陀陀胺碱 A、B 的化学结构,并首次归属了它们的~(13)C NMR 数据。  相似文献   
220.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号