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   8912篇
  免费   701篇
  国内免费   845篇
  2024年   31篇
  2023年   153篇
  2022年   338篇
  2021年   596篇
  2020年   389篇
  2019年   434篇
  2018年   444篇
  2017年   330篇
  2016年   416篇
  2015年   589篇
  2014年   670篇
  2013年   693篇
  2012年   851篇
  2011年   744篇
  2010年   467篇
  2009年   396篇
  2008年   430篇
  2007年   374篇
  2006年   324篇
  2005年   267篇
  2004年   219篇
  2003年   185篇
  2002年   156篇
  2001年   106篇
  2000年   115篇
  1999年   113篇
  1998年   87篇
  1997年   85篇
  1996年   56篇
  1995年   59篇
  1994年   73篇
  1993年   36篇
  1992年   39篇
  1991年   35篇
  1990年   26篇
  1989年   32篇
  1988年   18篇
  1987年   15篇
  1986年   11篇
  1985年   21篇
  1984年   7篇
  1983年   8篇
  1982年   7篇
  1981年   1篇
  1980年   4篇
  1979年   4篇
  1978年   2篇
  1975年   1篇
  1950年   1篇
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
211.

Background

Testing for HIV infection and entry to care are the first steps in the continuum of care that benefit individual health and may reduce onward transmission of HIV. We determined the percentage of people with HIV who were diagnosed late and the percentage linked into care overall and by demographic and risk characteristics by country.

Methods

Data were analyzed from national HIV surveillance systems. Six countries, where available, provided data on two late diagnosis indicators (AIDS diagnosis within 3 months of HIV diagnosis, and AIDS diagnosis within 12 months before HIV diagnosis) and linkage to care (≥1 CD4 or viral load test result within 3 months of HIV diagnosis) for people diagnosed with HIV in 2009 or 2010 (most recent year data were available).

Principal Findings

The percentage of people presenting with late stage disease at HIV diagnosis varied by country, overall with a range from 28.7% (United States) to 8.8% (Canada), and by transmission categories. The percentage of people diagnosed with AIDS who had their initial HIV diagnosis within 12 months before AIDS diagnosis varied little among countries, except the percentages were somewhat lower in Spain and the United States. Overall, the majority of people diagnosed with HIV were linked to HIV care within 3 months of diagnosis (more than 70%), but varied by age and transmission category.

Conclusions

Differences in patterns of late presentation at HIV diagnosis among countries may reflect differences in screening practices by providers, public health agencies, and people with HIV. The percentage of people who received assessments of immune status and viral load within 3 months of diagnosis was generally high.  相似文献   
212.
洋河酒窖泥细菌群落结构与菌株产酸能力分析   总被引:3,自引:3,他引:0  
【背景】窖泥微生物的种类及其代谢产物类型是影响浓香型白酒发酵过程中丁酸和己酸等白酒中主要有机酸合成的影响因素之一。【目的】揭示浓香型白酒不同窖龄窖泥细菌群落结构,研究厌氧细菌产酸性能,阐明窖泥细菌与白酒中有机酸合成的相关性。【方法】通过Illumina HiSeq高通量测序,基于16S rRNA基因序列分析不同窖龄窖泥细菌的组成。分离获得厌氧细菌,通过比较菌株产丁酸和己酸能力来分析窖泥的微生物代谢特性。【结果】洋河酒窖泥细菌主要分布于梭菌纲(Clostridia)、拟杆菌纲(Bacteroidia)、互营养菌纲(Synergistia)和芽孢杆菌纲(Bacilli)。20年窖龄的窖泥中氢孢菌属(Hydrogenispora)和瘤胃梭菌属(Ruminiclostridium)丰度显著增加。窖泥细菌间相关性分析表明,瘤胃梭菌属(Ruminiclostridium)为窖泥中影响最大的核心微生物,很多微生物与梭菌属(Clostridium)菌株之间多为相互促进关系。通过传统可培养方法共分离得到梭菌目(Clostridiales)的20株厌氧菌。其中梭菌属(Clostridium)菌株产酸能力高于其他菌属,酪丁酸梭菌(Clostridium tyrobutyricum)和丁酸梭菌(Clostridium butyricum)产丁酸和己酸的能力最强。产丁酸能力最高的菌主要分离自5年和20年窖龄窖泥,产己酸能力最高的菌分离自20年窖龄窖泥。【结论】解析了浓香型白酒不同窖龄窖泥的细菌组成,并对菌株产丁酸和己酸的能力进行了比较,为揭示窖泥微生物功能及其对白酒风味物质合成的影响奠定了相关的研究基础。  相似文献   
213.
214.
Tian  Jing  Branfireun  Brian A.  Lindo  Zoë 《Plant and Soil》2020,455(1-2):53-64
Plant and Soil - Global change is shown to significantly affect the C storage function of peatlands; however, a majority of previous research is focused on a single environmental stressor such as...  相似文献   
215.
Wang  Y.  Tian  T.  Li  X.  Tang  L.  Li  Y.  Wang  H.  Zhang  J.  Zhang  L.  Zhang  X. 《Microbiology》2020,89(1):122-128
Microbiology - An aerobic, gram-negative-staining, motile and rod-shaped bacterium, designated strain 3-BNT, was isolated from sewage sediment collected from Baiyangdian, located in Xiongan New...  相似文献   
216.
Li  Bingxin  Li  Wanyan  Tian  Yunbo  Guo  Sixuan  Qian  Long  Xu  Danning  Cao  Nan 《Biological trace element research》2020,193(2):508-516
Biological Trace Element Research - Selenium (Se) has been well recognized as an immune-enhancing agent with antioxidant and anti-tumor properties. The commonly used chemotherapy drug,...  相似文献   
217.
218.
Aberrant expression of the tripartite motif containing 59 (TRIM59) has been reported to participate in the development and progression of various human cancers. However, its expression pattern and cellular roles in pancreatic cancer (PC) remains unclear. In our study, we found that TRIM59 expression was significantly increased in PC tissues and was positively correlated with several malignant behaviors and poor overall survival of PC patients based on bioinformatics analysis and immunohistochemistry staining. Functionally, small interfering RNA–mediated TRIM59 depletion inhibited cell proliferation and migration in vitro, while TRIM59 overexpression promoted cell proliferation and migration in vitro and drove tumor growth and liver metastasis in vivo. Mechanically, TRIM59 was found to enhance glycolysis through activating the PI3K/AKT/mTOR pathway, ultimately contributing to PC progression. Taken together, our results demonstrate that TRIM59 may be a potential predictor for PC and promotes PC progression via the PI3K/AKT/mTOR-glycolysis signaling pathway, which establishes the rationale for targeting the TRIM59-related pathways to treat PC.  相似文献   
219.
Wu  Yanyan  Tian  Qinglan  Huang  Weihua  Liu  Jieyun  Xia  Xiuzhong  Yang  Xinghai  Mou  Haifei 《Molecular biology reports》2020,47(4):2951-2962
Molecular Biology Reports - Passion fruit (Passiflora edulis), an important tropical and subtropical fruit, has a high edible and medicinal value. Stem rot disease is one of the most important...  相似文献   
220.
Lu  Haotian  Shi  Chunying  Wang  Shuang  Yang  Chaochao  Wan  Xueqi  Luo  Yunzhe  Tian  Le  Li  Ling 《Molecular biology reports》2020,47(10):7831-7842
Molecular Biology Reports - Non-SMC condensin I complex subunit H (NCAPH) is a structural component of chromosomes during mitosis, which up-regulates in various cancers. However, the role of NCAPH...  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