全文获取类型
收费全文 | 3086篇 |
免费 | 272篇 |
国内免费 | 138篇 |
专业分类
3496篇 |
出版年
2023年 | 31篇 |
2022年 | 78篇 |
2021年 | 86篇 |
2020年 | 71篇 |
2019年 | 80篇 |
2018年 | 119篇 |
2017年 | 84篇 |
2016年 | 116篇 |
2015年 | 121篇 |
2014年 | 133篇 |
2013年 | 179篇 |
2012年 | 195篇 |
2011年 | 205篇 |
2010年 | 143篇 |
2009年 | 104篇 |
2008年 | 158篇 |
2007年 | 141篇 |
2006年 | 123篇 |
2005年 | 109篇 |
2004年 | 92篇 |
2003年 | 80篇 |
2002年 | 94篇 |
2001年 | 63篇 |
2000年 | 61篇 |
1999年 | 51篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1992年 | 46篇 |
1991年 | 43篇 |
1990年 | 40篇 |
1989年 | 33篇 |
1988年 | 28篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 30篇 |
1984年 | 24篇 |
1983年 | 24篇 |
1982年 | 20篇 |
1981年 | 33篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 34篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1975年 | 18篇 |
1974年 | 13篇 |
1973年 | 19篇 |
1969年 | 14篇 |
1968年 | 13篇 |
排序方式: 共有3496条查询结果,搜索用时 15 毫秒
91.
卡巴胆碱对缺血再灌注大鼠小肠组织髓过氧化物酶的影响 总被引:5,自引:0,他引:5
研究拟胆碱药卡巴胆碱对大鼠缺血再灌注损伤小肠组织髓过氧化物酶 (MPO)和丙二醛 (MDA)的影响及其与肠损伤相关指标变化的规律。Wistar大鼠被随机分为预防、治疗和对照三组。活杀后取小肠组织测MPO、MDA和肿瘤坏死因子 (TNF-α)含量。结果显示 ,治疗组及预防组MPO活性、MDA和TNF -α含量均明显低于对照组 ,治疗组与预防组之间差异不明显。提示卡巴胆碱可抑制致炎因子TNF -α的释放 ,减少中性粒细胞在肠组织的聚集 ,从而使小肠MPO活性降低 相似文献
92.
Sen U Sathnur PB Kundu S Givvimani S Coley DM Mishra PK Qipshidze N Tyagi N Metreveli N Tyagi SC 《American journal of physiology. Cell physiology》2012,303(1):C41-C51
Hydrogen sulfide (H(2)S) has recently been identified as a regulator of various physiological events, including vasodilation, angiogenesis, antiapoptotic, and cellular signaling. Endogenously, H(2)S is produced as a metabolite of homocysteine (Hcy) by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST). Although Hcy is recognized as vascular risk factor at an elevated level [hyperhomocysteinemia (HHcy)] and contributes to vascular injury leading to renovascular dysfunction, the exact mechanism is unclear. The goal of the current study was to investigate whether conversion of Hcy to H(2)S improves renovascular function. Ex vivo renal artery culture with CBS, CSE, and 3MST triple gene therapy generated more H(2)S in the presence of Hcy, and these arteries were more responsive to endothelial-dependent vasodilation compared with nontransfected arteries treated with high Hcy. Cross section of triple gene-delivered renal arteries immunostaining suggested increased expression of CD31 and VEGF and diminished expression of the antiangiogenic factor endostatin. In vitro endothelial cell culture demonstrated increased mitophagy during high levels of Hcy and was mitigated by triple gene delivery. Also, dephosphorylated Akt and phosphorylated FoxO3 in HHcy were reversed by H(2)S or triple gene delivery. Upregulated matrix metalloproteinases-13 and downregulated tissue inhibitor of metalloproteinase-1 in HHcy were normalized by overexpression of triple genes. Together, these results suggest that H(2)S plays a key role in renovasculopathy during HHcy and is mediated through Akt/FoxO3 pathways. We conclude that conversion of Hcy to H(2)S by CBS, CSE, or 3MST triple gene therapy improves renovascular function in HHcy. 相似文献
93.
China R Mukherjee S Sen S Bose S Datta S Koley H Ghosh S Dhar P 《Microbiological research》2012,167(8):500-506
Polyphenolic extracts (PE) of edible flower of Sesbania grandiflora were tested to evaluate its antimicrobial effect against some common pathogenic bacteria and growth promoting property against probiotic organism Lactobacillus acidophilus. The antimicrobial activity of S. grandiflora flower PE against selected pathogens was evaluated using both in vitro and in situ methods. In vitro studies suggested that PE has inhibitory effect against Staphylococcus aureus, Shigella flexneri 2a, Salmonella Typhi, Escherichia coli and Vibrio cholerae. The gram-positive organism S. aureus was the most sensitive organism to PE and minimum inhibitory concentration (MIC) was found to be 0.013 mg/mL where as the MIC of PE against V. cholerae was the highest (0.25 mg/mL). On the other hand PE showed growth promoting effect on the common probiotic bacterium L. acidophilus. The major finding was that S. grandiflora PE induced a significant biomass increase of L. acidophilus grown in liquid culture media. PE showed reduction of S. aureus growth in food (fish) during storage at 10°C. High performance liquid chromatography analysis showed that rutin, a major flavonoid of the PE diminished in the culture medium MRS broth with the growth of L. acidophilus. 相似文献
94.
95.
目的:探讨颅内动脉瘤夹闭术、血管内栓塞术治疗颅内动脉瘤的疗效及安全性。方法:回顾性分析2016年9月-2019年1月接受手术治疗的76例颅内动脉瘤患者的临床资料,根据手术方式的不同分为接受颅内动脉瘤夹闭术治疗的A组40例和接受血管内栓塞术治疗的B组36例。对比两组患者的动脉瘤完全闭合率、住院费用及血清炎性因子[C反应蛋白(CRP)、白介素-1β(IL-1β)、白介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)]、脑氧饱和度水平及日常生活能力量表(ADL)评分值,记录并发症发生情况。结果:两组患者的动脉瘤完全闭合率比较差异无统计学意义(x~2=0.515,P=0.473)。A组患者的住院费用低于B组患者(t=17.732,P=0.000);A组患者术后血清中CRP、IL-1β、IL-6、TNF-α的水平高于B组(t=10.580、12.904、9.355、19.176,P均=0.000);A组患者术后脑氧饱和度水平低于B组(t=2.113,P=0.019),两组ADL评分值的差异无统计学意义(t=1.211,P=0.115);A组术中再破裂、脑血管痉挛发生率高于B组患者(x~2=4.817、5.383,P=0.028、0.020)。结论:颅内动脉瘤夹闭术应用于颅内动脉瘤患者,动脉瘤完全闭合率与血管内栓塞术无明显差异,住院费用更低,但对目标血管的刺激较大,可能存在术中再破裂、脑血管痉挛等风险。 相似文献
96.
Sen P Mukherjee S Bhaumik G Das P Ganguly S Choudhury N Raha S 《Mutation research》2003,529(1-2):87-94
Exposure of Chinese hamster V79 fibroblasts to mild and repetitive H2O2 doses in culture for 15 weeks produced no change in lipid peroxidation status, GSH/GSSG ratio and glutathione peroxidase activity of these cells (VST cells). In contrast, in VST cells catalase levels underwent a prominent increase which could be significantly inhibited and brought down to control levels after treatment with the catalase inhibitor 3-aminotriazole (3-AT). When control (VC) cells were exposed to UV radiation (UVC 5 J/m2) or H2O2 (7.5mM, 15 min), intracellular reactive oxygen species (ROS) levels rose prominently with significant activation of caspase-3. Marked nuclear fragmentation and lower cell viability were also noted in these cells. In contrast, VST cells demonstrated a significantly lower ROS level, an absence of nuclear fragmentation and an unchanged caspase-3 activity after exposure to UVC or H2O2. Cell viability was also significantly better preserved in VST cells than VC cells after UV or H2O2 exposures. Following 3-AT treatment of VST cells, UVC radiation or H2O2 brought about significantly higher elevations in intracellular ROS, increases in caspase-3 activity, significantly lowered cell viability and marked nuclear fragmentation, indicating the involvement of high catalase levels in the cytoprotective effects of repetitive stress. Therefore, upregulation of the antioxidant defense after repetitive oxidative stress imparted a superior ability to cope with subsequent acute stress and escape apoptotic death and loss of viability. 相似文献
97.
Dipankar Sen 《Phytochemistry》1975,14(7):1505-1506
For measurement of cytochrome c oxidase activity in intact plant mitochondria the optimum concentration of K-Pi buffer and pH in the reaction was found to be 75 mM and 7.4 respectively. The suitable concentration of K-Pi buffer for suspending and storing mitochondria, however, was found to be 20 mM or lower. These requirements applied equally well for mitochondria from wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), maize (Zea mays L.), and snap bean (Phaseolus vulgaris L.). 相似文献
98.
Isolation and protein pattern of eye lens fiber junctions 总被引:13,自引:0,他引:13
99.
目的:克隆水牛白细胞分化抗原14(buffalo cluster of differentiation antigen14,bCD14)基因,表达bCD14蛋白,并进行Western Blot鉴定.方法:采用RT-PCR方法从水牛外周血白细胞中扩增bCD14基因,构建重组质粒pET28a-bCD14,转化入E coli BL21,IPTG诱导表达,对表达蛋白进行可溶性分析及Western blot鉴定.结果:bCD14基因含有一个1 122bp的开放阅读框,编码373个氨基酸;与印度水牛、挪威大鼠和人CD14的cDNA序列同源性分别为97.95%、68.78%、78.60%,氨基酸同源性分别为96.78%、61.27%、72.34%;主要以包涵体形式表达,表达蛋白经Western Blot鉴定,得到了一条约46 kD的特异性条带.结论:该文成功克隆了bCD14基因,表达了bCD14蛋白,为进一步揭示水牛抵抗革兰氏阴性菌感染的免疫机制奠定了基础. 相似文献
100.
The objective of this study was to determine the prevalence, mutual associations, clinical manifestations, and diagnoses associated
with serum autoantibodies, as detected using recently available immunoassays, in patients with autoimmune myositis (AIM).
Sera and clinical data were collected from 100 patients with AIM followed longitudinally. Sera were screened cross-sectionally
for 21 autoantibodies by multiplex addressable laser bead immunoassay, line blot immunoassay, immunoprecipitation of in vitro translated recombinant protein, protein A assisted immunoprecipitation, and enzyme-linked immunosorbent assay. Diagnoses
were determined using the Bohan and Peter classification as well as recently proposed classifications. Relationships between
autoantibodies and clinical manifestations were analyzed by multiple logistic regression. One or more autoantibodies encompassing
19 specificities were present in 80% of the patients. The most common autoantibodies were anti-Ro52 (30% of patients), anti-Ku
(23%), anti-synthetases (22%), anti-U1RNP (15%), and anti-fibrillarin (14%). In the presence of autoantibodies to Ku, synthetases,
U1RNP, fibrillarin, PM-Scl, or scleroderma autoantigens, at least one more autoantibody was detected in the majority of sera
and at least two more autoantibodies in over one-third of sera. The largest number of concurrent autoantibodies was six autoantibodies.
Overall, 44 distinct combinations of autoantibodies were counted. Most autoantibodies were unrestricted to any AIM diagnostic
category. Distinct clinical syndromes and therapeutic responses were associated with anti-Jo-1, anti-fibrillarin, anti-U1RNP,
anti-Ro, anti-Ro52, and autoantibodies to scleroderma autoantigens. We conclude that a significant proportion of AIM patients
are characterized by complex associations of autoantibodies. Certain myositis autoantibodies are markers for distinct overlap
syndromes and predict therapeutic outcomes. The ultimate clinical features, disease course, and response to therapy in a given
AIM patient may be linked to the particular set of associated autoantibodies. These results provide a rationale for patient
profiling and its application to therapeutics, because it cannot be assumed that the B-cell response is the same even in the
majority of patients in a given diagnostic category. 相似文献