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   4492篇
  免费   351篇
  国内免费   523篇
  2024年   9篇
  2023年   48篇
  2022年   166篇
  2021年   276篇
  2020年   203篇
  2019年   235篇
  2018年   217篇
  2017年   168篇
  2016年   243篇
  2015年   316篇
  2014年   419篇
  2013年   364篇
  2012年   480篇
  2011年   435篇
  2010年   284篇
  2009年   241篇
  2008年   267篇
  2007年   219篇
  2006年   139篇
  2005年   139篇
  2004年   90篇
  2003年   82篇
  2002年   51篇
  2001年   39篇
  2000年   30篇
  1999年   20篇
  1998年   17篇
  1997年   11篇
  1996年   9篇
  1995年   8篇
  1994年   6篇
  1993年   3篇
  1992年   12篇
  1991年   9篇
  1990年   9篇
  1989年   11篇
  1988年   5篇
  1987年   8篇
  1986年   13篇
  1985年   11篇
  1984年   5篇
  1983年   8篇
  1982年   5篇
  1980年   8篇
  1978年   4篇
  1977年   3篇
  1974年   2篇
  1973年   3篇
  1972年   4篇
  1971年   2篇
排序方式: 共有5366条查询结果,搜索用时 15 毫秒
131.
增强型绿色荧光蛋白(EGFP)是生物领域常用的标记物. 本实验首先利用高碘酸法活化低分子肝素(LMWH),与EGFP连接得到LMWH EGFP.然后用Sephacryl S-200 HR对其进行初步分离,再用Sephadex G-10 HR进行脱盐纯化. 采用Sephacryl S 200 HR检测LMWH EGFP的纯度,为单一对称峰. 经检测,LMWH-EGFP具有良好的热稳定性和耐碱性. 通过荧光分光检测器检测LMWH-EGFP的λEx为488 nm,λEm为509 nm. 通过抗凝实验发现LMWH EGFP仍具有抗凝活性. 本实验建立了LWMH荧光标记的方法,为多糖的荧光标记提供了新的选择.  相似文献   
132.
目的:探讨化疗联合冷循环射频消融术治疗原发性肝癌的疗效及安全性。方法:108例原发性肝癌患者随机分为两组,均给予灌注化疗,每4周进行一次灌注化疗,对照组(n=54)进行3次,治疗组(n=54)只进行一次。治疗组给予冷循环射频消融术。评价生活质量Kamofsky评分,治疗前后检查患者的血、尿、便常规,肝肾功能(包括天冬氨酸转氨酶、丙氨酸转氨酶(AVr)、白蛋白(ALB)、总胆红素、肌酐及尿素氮等指标),甲胎蛋白(AFP),T细胞亚群和加强肝脏CT扫描。随访1年,经CT确定肝癌复发。结果:治疗组Kamofsky评分有效率为59.26%,对照组Kamofsky评分有效率为37.03%,两组Kamofsky评分有效率相比较,差异有统计学意义(P〈0.05)。两组治疗后症状变化相比较,除腹胀外其余各项指标差异均有统计学意义(P〈O.05)。治疗后两组相比较,ALT和AFP差异有统计学意义(P〈0.05)。治疗后两组T细胞亚群变化相比较,治疗组各项指标均变化显著(P〈0.05)。治疗后随访一年,治疗组复发率为22.22%;对照组复发率为53.70%。两组治疗一年后复发率相比较,差异有统计学意义(P〈0.05)。结论:化疗结合冷循环射频消融术治疗原发性肝癌疗效肯定,并发症及副作用小,复发率低。  相似文献   
133.
心血管疾病是现今导致病人发病和死亡的首要因素,很多因素在血管性疾病发病发展中起着重要作用,血栓形成是参与脑中风及急性冠状动脉综合症的首要因素。血栓素A2(TXA2)是一种强血小板活化因子,在糖尿病患者体内的合成显著增加,并通过作用于血栓素受体诱导血小板聚集,血管收缩,血栓形成参与糖尿病心血管并发症的发生发展。因此,以TXA2为靶点开发抗血栓类药物对心血管疾病起着预防及治疗作用。本文对TXA2介导的糖尿病血管并发症的发病机制,及以此为靶点开发的抗血栓药物进行综述,为糖尿病心血管并发症的治疗及新型低副作用抗血栓药物的研发提供新的靶点。  相似文献   
134.
目的:了解血培养(包括血液、无菌体液培养,下同)阳性标本中病原菌的分布及阳性报警时间,为临床及时明确病原菌和正确用药提供参考依据。方法:无菌条件下采集血培养标本注人相应的培养瓶,经仪器扫描后放入血培养仪进行检测,报警后及时进行菌种鉴定和药敏试验。结果:364例阳性报警标本中真阳性标本为176例,其中革兰阳性菌占61.7%,革兰阴性菌占35.0%,真菌占3.3%;188例为假阳性标本,其中革兰阳性菌占54%,革兰阴性菌占41.9%,真菌占4.0%;新生儿科的感染阳性率最高;不同种类病原菌的阳性报警时间多重叠;临床医生经验用药正确或根据药敏结果更换用药的百分比为78.2%。结论:本院引起血液、无菌体液感染的病原菌以革兰阳性细菌为主,病原菌种类较多,存在一定的污染;当新生儿有局部感染时要警惕脓毒血症;单独靠血培养仪报警时间来鉴定区分病原菌与污染菌不一定可靠,及时了解血培养结果及标准药敏结果可以辅助找出感染性疾病的病因,尽早正确合理的使用抗菌药物,从而优化抗菌治疗。  相似文献   
135.

Objective

To examine alcohol use and subsequent HIV risky behaviors among a sample of predominately ethnic minority people living with HIV/AIDS (PLWHA) in a rural community in Yunnan Province, China.

Method

A cross-sectional study with a face-to-face questionnaire interview was conducted among eligible participants.

Results

In total, 455 (94.4%) out of 482 eligible HIV patients participated in the study. Of them, 82.6% were ethnic minorities; 15.4% were never married; 96.5% were sexually experienced; 55.4% had used drugs, 67% were receiving antiretroviral therapy (ART). Over 65% were ever drinkers; of whom 61.5% were current drinkers. Among current drinkers, 32.4% drank daily and 41.2% were hazardous drinkers. Chinese white wine was the preferred choice. Higher level of alcohol use among drinkers in the preceding month was positively associated with being males (OR = 2.76, 95%CI: 1.03–7.43), ethnic minorities (OR Jingpo = 2.21, 95%CI: 1.06–4.59; OR other minorities = 3.20, 95%CI: 1.34–7.62), higher education (OR1–6 = 1.98, 95%CI: 0.99–3.96; OR≥7 = 2.35, 95%CI: 1.09–5.06) and being ART-naive (OR = 2.69, 95%CI: 1.67–4.32). About 39% of ever drinkers reported having engaged in sex after drinking since HIV diagnosis. Those who were younger than 46 years (OR16–25 = 7.77, 95%CI: 1.22–49.60, OR26–35 = 2.79, 95%CI: 1.06–7.35, OR36–45 = 2.96, 95%CI: 1.57–7.58), hazardous drinkers (OR = 1.99, 95%CI: 1.00–3.97) and drug users (OR = 3.01, 95%CI: 1.19–7.58) were more likely to have had sex after drinking. Approximately 56% of drug users had used drugs after drinking.

Conclusions

High prevalence of alcohol use and subsequent risky behaviors including sexual engagement and drug use among HIV patients in rural Yunnan require tremendous and integrated efforts for prevention and control of alcohol and drug abuse and HIV spreading.  相似文献   
136.

Background

This study aimed to assess whether Chinese men who have sex with men (MSM) had a significantly elevated prevalence of psychiatric disorders compared to urban males in China.

Methods

807 MSM were recruited using a respondent-driven sampling (RDS) method in urban area of northeast China. Psychiatric disorders were assessed employing the Composite International Diagnostic Interview (CIDI. Version 1.0) according to the criteria of the DSM-III-R.

Results

Chinese MSM had a significantly elevated standardized prevalence ratios (SPR) for lifetime prevalence of any disorder (SPR = 2.8; 95%CI: 2.5–3.2), mood disorder (SPR = 3.0; 95%CI: 2.3–3.7), anxiety disorder (SPR = 5.5; 95% CI: 4.6–6.5), alcohol use disorder (SPR = 2.4, 95%CI: 2.0–2.8), and combination of disorders (SPR = 4.2; 95%CI: 3.4–5.1).

Conclusions

Chinese MSM had significantly elevated prevalence and comorbidity of psychiatric disorders. RDS is a suitable sampling method for psychiatric epidemiological survey in MSM population.  相似文献   
137.

Objective

Voluntary counseling and testing (VCT) plays an important integral role in response to the HIV/AIDS epidemic. However, VCT service has not been effectively utilized among rural migrants, a high risk group in China. In this study, we developed a community based intervention to examine if community mobilization with comprehensive VCT is more effective than current HIV preventions with routine VCT service in promoting VCT acceptability among rural migrants in Shanghai, China.

Methods

A comprehensive intervention with community mobilization and comprehensive VCT services including community-based VCT and mobile VCT was implemented during 2007–2009. Three communities in Minhang District of Shanghai were randomly selected and were designed to receive community mobilization and comprehensive VCT, traditional VCT and none intervention, respectively. After 24 months intervention, effects were evaluated by comparing outcome indicators between the baseline (2,690 participants) and follow-up surveys (1,850 participants).

Findings

A substantial increase in VCT acceptance was observed among community mobilization group (94.9% vs. 88.5%, P<0.001), whereas the reverse effect was seen in the traditional VCT group (86.1% vs. 94.6%, P<0.001) and control group (69.0% vs. 91.7%, P<0.001). Rural migrants from community mobilization group were more likely to accept VCT (OR = 2.91, 95% CI 1.69–4.97). Rural migrants from community mobilization group also showed significant increase in HIV/AIDS knowledge, positive attitude towards HIV positive individuals and condom use.

Conclusion

Community mobilization with comprehensive VCT has significant impact on promotion of VCT acceptance and utilization among rural migrants in Shanghai. These findings provide evidence to support community mobilization as a suitable strategy for VCT promotion among rural migrants in Shanghai, China.  相似文献   
138.
Mesenchymal stem cells (MSCs) reside in almost all of the body tissues, where they undergo self-renewal and multi-lineage differentiation. MSCs derived from different tissues share many similarities but also show some differences in term of biological properties. We aim to search for significant differences among various sources of MSCs and to explore their implications in physiopathology and clinical translation. We compared the phenotype and biological properties among different MSCs isolated from human term placental chorionic villi (CV), umbilical cord (UC), adult bone marrow (BM) and adipose (AD). We found that CD106 (VCAM-1) was expressed highest on the CV-MSCs, moderately on BM-MSCs, lightly on UC-MSCs and absent on AD-MSCs. CV-MSCs also showed unique immune-associated gene expression and immunomodulation. We thus separated CD106+cells and CD106cells from CV-MSCs and compared their biological activities. Both two subpopulations were capable of osteogenic and adipogenic differentiation while CD106+CV-MSCs were more effective to modulate T helper subsets but possessed decreased colony formation capacity. In addition, CD106+CV-MSCs expressed more cytokines than CD106CV-MSCs. These data demonstrate that CD106 identifies a subpopulation of CV-MSCs with unique immunoregulatory activity and reveal a previously unrecognized mechanism underlying immunomodulation of MSCs.  相似文献   
139.
140.
In this study, we describe a novel porcine parechovirus-like virus (tentatively named PLV-CHN) from healthy piglets in China using 454 high-throughput sequencing. The complete genome of the virus comprises 6832 bp, encoding a predicted polyprotein of 2132 amino acids that is most similar to Ljungan virus (32% identity). A similar virus that belongs to a novel Picornaviridae genus, named swine pasivirus 1 (SPaV-1), was reported during the preparation of this paper. Sequence analysis revealed that PLV-CHN and SPaV1 shared 82% nucleotide identity and 89% amino acid identity. Further genomic and phylogenetic analyses suggested that both SPaV1 and PLV-CHN shared similar genomic characteristics and belong to the same novel Picornaviridae genus. A total of 36 (20.0%) fecal samples from 180 healthy piglets were positive for PLV-CHN by RT-PCR, while no fecal samples from 100 healthy children and 100 children with diarrhea, and no cerebrospinal fluid samples from 196 children with suspected viral encephalitis, was positive for the virus. However, Western blot and enzyme-linked immunosorbent assays using recombinant PLV-CHN VP1 polypeptide as an antigen showed a high seroprevalence of 63.5% in the healthy population. When grouped by age, the antibody-positivity rates showed that the majority of children under 12 years of age have been infected by the virus. It was suggested that PLV-CHN, SPaV1, or an as-yet-uncharacterized virus can infect humans early in life. Thus, investigation of the role of this novel virus is vital.  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