首页 | 官方网站   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   18466篇
  免费   1716篇
  国内免费   815篇
医药卫生   20997篇
  2024年   26篇
  2023年   195篇
  2022年   245篇
  2021年   702篇
  2020年   521篇
  2019年   590篇
  2018年   595篇
  2017年   519篇
  2016年   564篇
  2015年   796篇
  2014年   1026篇
  2013年   988篇
  2012年   1402篇
  2011年   1486篇
  2010年   971篇
  2009年   764篇
  2008年   1035篇
  2007年   1048篇
  2006年   962篇
  2005年   995篇
  2004年   760篇
  2003年   824篇
  2002年   716篇
  2001年   566篇
  2000年   456篇
  1999年   350篇
  1998年   214篇
  1997年   174篇
  1996年   155篇
  1995年   133篇
  1994年   108篇
  1993年   75篇
  1992年   127篇
  1991年   134篇
  1990年   104篇
  1989年   99篇
  1988年   71篇
  1987年   67篇
  1986年   69篇
  1985年   55篇
  1984年   44篇
  1983年   30篇
  1982年   17篇
  1981年   18篇
  1980年   20篇
  1979年   29篇
  1978年   25篇
  1977年   19篇
  1976年   14篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
The Combined Aerobic and Resistance Exercise (CARE) Trial compared different types and doses of exercise performed during breast cancer chemotherapy. Here, we report the longer-term follow-up of patient-reported outcomes, health-related fitness and exercise behavior at 6, 12 and 24 months postintervention. A multicenter trial in Canada randomized 301 breast cancer patients initiating chemotherapy to thrice weekly, supervised exercise consisting of a standard dose of 25–30 min of aerobic exercise (STAN; n = 96), a higher dose of 50–60 min of aerobic exercise (HIGH; n = 101) or a combined dose of 50–60 min of aerobic and resistance exercise (COMB; n = 104) performed for the duration of chemotherapy (median of 17 weeks). Primary outcomes were patient-reported outcomes including quality of life, cancer-related symptoms and psychosocial outcomes. Secondary outcomes were objective health-related fitness (assessed at 12 months only) and self-reported exercise behavior. A total of 269 (89.4%) participants completed patient-reported outcomes at all three follow-up time points and 263 (87.4%) completed the health-related fitness assessment at 12-month follow-up. COMB was significantly superior to (i) STAN for sleep quality at 6-month follow-up (p = 0.027); (ii) HIGH for upper body muscular endurance at 12-month follow-up (p = 0.020); and (iii) HIGH for meeting the resistance exercise guideline at 6-month follow-up (p = 0.006). Moreover, self-reported meeting of the combined exercise guideline during follow-up was significantly associated with better patient-reported outcomes and health-related fitness. Performing combined exercise during and after breast cancer chemotherapy may result in better longer-term patient-reported outcomes and health-related fitness compared to performing aerobic exercise alone.  相似文献   
2.
3.
4.
5.
In China, colorectal cancer (CRC) ranked fourth and fifth in the highest incidence and mortality rates of all malignancies in 2018, respectively. Although these rates are below the world average, China placed first worldwide in the number of new CRC cases and CRC-related deaths because of its comparatively large population. This disease represents a threat to the health of population and incurs a heavy economic burden on the society and individuals. CRC has various risk factors, including age, sex, lifestyle, genetic factors, obesity, diabetes, gut microbiota status, and precancerous lesions. Furthermore, incidence and mortality rates of CRC are closely related to socioeconomic development levels, varying according to regional and population characteristics. Prevention is the main strategy to reduce incidence and mortality rates of CRC. This can be achieved through strategies stimulating lifestyle changes, healthy diet habits, and early screening for high-risk individuals. To reduce the burden of CRC, public health officials should promote prevention and management of modifiable risk factors through national policies. The rising incidence and mortality rates of CRC in China may be timely curbed by clarifying specific epidemiological characteristics, optimizing early screening strategies, and strictly implementing diagnosis and treatment guidelines. Thus, this study aimed to collect and report the current research status on epidemiology and risk factors of CRC in China.  相似文献   
6.
Expansions of trinucleotide or hexanucleotide repeats lead to several neurodegenerative disorders, including Huntington disease [caused by expanded CAG repeats (CAGr) in the HTT gene], and amyotrophic lateral sclerosis [ALS, possibly caused by expanded GGGGCC repeats (G4C2r) in the C9ORF72 gene], of which the molecular mechanisms remain unclear. Here, we demonstrated that lowering the Drosophila homologue of tau protein (dtau) significantly rescued in vivo neurodegeneration, motor performance impairments, and the shortened life-span in Drosophila expressing expanded CAGr or expanded G4C2r. Expression of human tau (htau4R) restored the disease-related phenotypes that had been mitigated by the loss of dtau, suggesting an evolutionarily-conserved role of tau in neurodegeneration. We further revealed that G4C2r expression increased tau accumulation by inhibiting autophagosome–lysosome fusion, possibly due to lowering the level of BAG3, a regulator of autophagy and tau. Taken together, our results reveal a novel mechanism by which expanded G4C2r causes neurodegeneration via an evolutionarily-conserved mechanism. Our findings provide novel autophagy-related mechanistic insights into C9ORF72-ALS and possible entry points to disease treatment.Electronic supplementary materialThe online version of this article (10.1007/s12264-020-00518-2) contains supplementary material, which is available to authorized users.  相似文献   
7.
Pulmonary hypertension of the newborn (PHN) constitutes a critical condition with severe cardiovascular and neurological consequences. One of its main causes is hypoxia during gestation, and thus, it is a public health concern in populations living above 2500 m. Although some mechanisms are recognized, the pathophysiological facts that lead to PHN are not fully understood, which explains the lack of an effective treatment. Oxidative stress is one of the proposed mechanisms inducing pulmonary vascular dysfunction and PHN. Therefore, we assessed whether melatonin, a potent antioxidant, improves pulmonary vascular function. Twelve newborn sheep were gestated, born, and raised at 3600 meters. At 3 days old, lambs were catheterized and daily cardiovascular measurements were recorded. Lambs were divided into two groups, one received daily vehicle as control and another received daily melatonin (1 mg/kg/d), for 8 days. At 11 days old, lung tissue and small pulmonary arteries (SPA) were collected. Melatonin decreased pulmonary pressure and resistance for the first 3 days of treatment. Further, melatonin significantly improved the vasodilator function of SPA, enhancing the endothelial‐ and muscular‐dependent pathways. This was associated with an enhanced nitric oxide‐dependent and nitric oxide independent vasodilator components and with increased nitric oxide bioavailability in lung tissue. Further, melatonin reduced the pulmonary oxidative stress markers and increased enzymatic and nonenzymatic antioxidant capacity. Finally, these effects were associated with an increase of lumen diameter and a mild decrease in the wall of the pulmonary arteries. These outcomes support the use of melatonin as an adjuvant in the treatment for PHN.  相似文献   
8.
目的:探讨新生血管特异性结合肽GX1二聚体对胃癌新生血管生成的影响。方法:化学合成GX1二聚体、GX1单体、对照肽二聚体,CCK-8实验、管状结构形成实验、迁移实验研究GX1二聚体对胃癌血管内皮细胞(co-HUVEC)增殖、微管形成、迁移能力的影响,流式细胞学技术分析其对细胞周期分布和凋亡的影响。结果:CCK-8结果显示,GX1二聚体与对照肽二聚体及PBS对照组相比,100~200 μmol/L可抑制co-HUVEC增殖,具有统计学差异(P<0.05),并呈剂量依赖性,GX1二聚体较单体抑制作用增强,并有统计学差异(P<0.05)。管状结构形成实验、细胞损伤迁移实验结果显示,与对照肽二聚体及对照组PBS 相比,GX1二聚体及GX1单体,均可抑制胃癌内皮细胞管状结构的形成及迁移,且二聚体抑制作用强于单体;对照肽二聚体仅有轻微的抑制胃癌内皮细胞管状结构的形成及迁移。流式细胞术分析显示,与对照肽二聚体及PBS对照组相比,GX1二聚体及GX1单体均可诱导细胞凋亡(P<0.05),且GX1二聚体的诱导作用强于GX1单体(P<0.05),而对细胞周期分布则无明显影响。结论:GX1二聚体和GX1单体均可抑制胃癌新生血管内皮细胞增殖、微管形成、迁移能力及诱导凋亡,且GX1二聚体较GX1单体作用增强。GX1二聚体有望代替单体成为胃癌新生血管靶向治疗小肽类药物。  相似文献   
9.
Rifamycins (rifampin, rifabutin, and rifapentine) play an essential role in the treatment of mycobacterial and some nonmycobacterial infections. They also induce the activity of various drug transporting and metabolizing enzymes, which can impact the concentrations and efficacy of substrates. Many anticoagulant and antiplatelet (AC/AP) agents are substrates of these enzymes and have narrow therapeutic indices, leading to risks of thrombosis or bleeding when coadministered with rifamycins. The objective of this systematic review was to evaluate the effects on AC/AP pharmacokinetics, laboratory markers, and clinical safety and efficacy of combined use with rifamycins. A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidance was performed. The PubMed, Embase, and Web of Science databases were queried for English-language reports on combination use of rifamycins and AC/AP agents from database inception through August 2021. The 29 studies identified examined warfarin (n = 17), direct oral anticoagulants (DOACs) (n = 8), and antiplatelet agents (n = 4) combined with rifampin (n = 28) or rifabutin (n = 1). Eleven studies were case reports or small case series; 14 reported on pharmacokinetic or laboratory markers in healthy volunteers. Rifampin-warfarin combinations led to reductions in warfarin area under the curve (AUC) of 15%–74%, with variability by warfarin isomer and study. Warfarin dose increases of up to 3–5 times prerifampin doses were required to maintain coagulation parameters in the therapeutic range. DOAC AUCs were decreased by 20%–67%, with variability by individual agent and with rifampin versus rifabutin. The active metabolite of clopidogrel increased substantially with rifampin coadministration, whereas prasugrel was largely unaffected and ticagrelor saw decreases. Our review suggests most combinations of AC/AP agents and rifampin are problematic. Further studies are required to determine whether rifabutin or rifapentine could be safe alternatives for coadministration with AC/AP drugs.  相似文献   
10.
薄层色谱鉴别在历版《中国药典》中的应用经历了从无到有、从少到多的过程;而薄层扫描含量测定在最近几版《中国药典》中的应用比例逐渐降低。随着对中药质量标准体系要求的进一步提高,薄层色谱法的不足之处陆续显现,如仪器普及率低、设备并不简单、结果重复性和稳定性较差、鉴别速度及准确性不及高效液相色谱法、展开剂毒性大等,逐渐不合时宜。在制定中药质量标准时,研究者不应该墨守成规,薄层色谱鉴别也不应该是雷打不动的定性鉴别必备选项。高效液相色谱法具备完全取代薄层色谱法的可行性,薄层色谱法可作为高效液相色谱法的补充。为充分降低检测成本、缩短检测周期、提高鉴别效率,笔者建议中药质量标准体系应该大幅减少薄层色谱鉴别方法的应用,增加高效液相特征图谱鉴定,尽量做到“一个条件,一张图谱”;除非确有必要,《中国药典》等国家质量标准体系应将薄层色谱鉴别作为推荐方法,而非强制标准。  相似文献   
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-23

京公网安备 11010802026262号