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   9381篇
  免费   721篇
  国内免费   861篇
  2024年   17篇
  2023年   117篇
  2022年   287篇
  2021年   536篇
  2020年   324篇
  2019年   463篇
  2018年   412篇
  2017年   269篇
  2016年   458篇
  2015年   607篇
  2014年   721篇
  2013年   806篇
  2012年   912篇
  2011年   781篇
  2010年   446篇
  2009年   444篇
  2008年   471篇
  2007年   409篇
  2006年   379篇
  2005年   268篇
  2004年   260篇
  2003年   211篇
  2002年   158篇
  2001年   135篇
  2000年   122篇
  1999年   107篇
  1998年   104篇
  1997年   91篇
  1996年   83篇
  1995年   71篇
  1994年   64篇
  1993年   46篇
  1992年   79篇
  1991年   47篇
  1990年   33篇
  1989年   37篇
  1988年   22篇
  1987年   25篇
  1986年   25篇
  1985年   24篇
  1984年   11篇
  1983年   9篇
  1982年   10篇
  1981年   6篇
  1980年   5篇
  1979年   9篇
  1976年   4篇
  1973年   5篇
  1971年   4篇
  1968年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.

Background

A number of reports have indicated an association between thyroid diseases and primary Sjögren''s syndrome (pSS). However, fewer studies have investigated whether the presence of thyroid diseases is associated with increased risk of developing pSS. Thus, the aim of our study was to use a nationwide health claims database to explore the prevalence and risk of pSS in female patients with thyroid diseases.

Methods

From the Registry of Catastrophic Illness database in the National Health Insurance Research Database in Taiwan, we identified 389 female patients with a diagnosis of pSS from 2005 to 2010. We also obtained 1945 control subjects frequency-matched on sex, 10-year age interval, and year of index date from the Longitudinal Health Insurance Database (LHID2000). Both groups were retrospectively traced back to a period of eight years to obtain diagnosis of thyroid diseases prior to index date.

Results

A significantly higher risk of pSS was associated with the presence of thyroid diseases (adjusted odds ratio (AOR) = 2.1, 95% confidence interval (CI) = 1.6–2.9). Among the sub-categories of thyroid diseases, patients with thyroiditis (AOR = 3.6, 95% CI = 1.7–7.5), thyrotoxicosis (AOR = 2.5, 95% CI = 1.6–3.8), and unspecified hypothyroidism (AOR = 2.4, 95% CI = 1.2–4.6), and simple and unspecified goiter (AOR = 2.0, 95% CI = 1.3–3.3) were significantly associated with increased risk of pSS. The associations were generally stronger in the mid-forties to mid-sixties age group, except in patients with unspecified hypothyroidism.

Conclusions

The risk of pSS was significantly increased in female patients with thyroid diseases, particularly those in their mid-forties to mid-sixties. An increased awareness of the possibility of pSS in perimenopausal females with thyroid diseases is important to preserve their quality of life and to avoid comorbidity.  相似文献   
222.
Recent studies have demonstrated the possible function of miR-139-5p in tumorigenesis. However, the exact mechanism of miR-139-5p in cancer remains unclear. In this study, the association of miR-139-5p expression with esophageal squamous cell carcinoma (ESCC) was evaluated in 106 pairs of esophageal cancer and adjacent non-cancerous tissue from ESCC patients. The tumor suppressive features of miR-139-5p were measured by evaluating cell proliferation and cell cycle state, migratory activity and invasion capability, as well as apoptosis. Luciferase reporter assay and Western blot analysis were performed to determine the target gene regulated by miR-139-5p. The mRNA level of NR5A2, the target gene of miR-139-5p, was determined in ESCC patients. Results showed that reduced miR-139-5p level was associated with lymph node metastases of ESCC. MiR-139-5p was investigated to induce cell cycle arrest in the G0/G1 phase and to suppress the invasive capability of esophageal carcinoma cells by targeting the 3′UTR of oncogenic NR5A2. Cyclin E1 and MMP9 were confirmed to participate in cell cycle arrest and invasive suppression induced by NR5A2, respectively. Pearson correlation analysis further confirmed the significantly negative correlation between miR-139-5p and NR5A2 expression. The results suggest that miR-139-5p exerts a growth- and invasiveness-suppressing function in human ESCCs, which demonstrates that miR-139-5p is a potential biomarker for early diagnosis and prognosis and is a therapeutic target for ESCC.  相似文献   
223.
Using samples from eastern China (c. 25 – 41° N and 99 – 123° E) and from a common garden experiment, we investigate how Mg concentration varies with climate across multiple trophic levels. In soils, plant tissue (Oriental oak leaves and acorns), and a specialist acorn predator (the weevil Curculio davidi), Mg concentration increased significantly with different slopes from south to north, and generally decreased with both mean annual temperature (MAT) and precipitation (MAP). In addition, soil, leaf, acorn and weevil Mg showed different strengths of association and sensitivity with climatic factors, suggesting that distinct mechanisms may drive patterns of Mg variation at different trophic levels. Our findings provide a first step toward determining whether anticipated changes in temperature and precipitation due to climate change will have important consequences for the bioavailability and distribution of Mg in food chain.  相似文献   
224.
Plant-specific PIN-formed (PIN) efflux transporters for the plant hormone auxin are required for tissue-specific directional auxin transport and cellular auxin homeostasis. The Arabidopsis PIN protein family has been shown to play important roles in developmental processes such as embryogenesis, organogenesis, vascular tissue differentiation, root meristem patterning and tropic growth. Here we analyzed roles of the less characterised Arabidopsis PIN6 auxin transporter. PIN6 is auxin-inducible and is expressed during multiple auxin–regulated developmental processes. Loss of pin6 function interfered with primary root growth and lateral root development. Misexpression of PIN6 affected auxin transport and interfered with auxin homeostasis in other growth processes such as shoot apical dominance, lateral root primordia development, adventitious root formation, root hair outgrowth and root waving. These changes in auxin-regulated growth correlated with a reduction in total auxin transport as well as with an altered activity of DR5-GUS auxin response reporter. Overall, the data indicate that PIN6 regulates auxin homeostasis during plant development.  相似文献   
225.
Zhang  Lin  Tao  Ye  Zhao  Suya  Yin  Xiaoyan  Chen  Junmei  Wang  Miao  Cai  Yingfan  Niu  Qiuhong 《Plant and Soil》2020,454(1-2):395-409
Plant and Soil - [Aims] To reveal the molecular mechanism of endophytic bacteria in Verticillium wilt-resistant cottons and deeply understand the interaction between soil and plants. [Methods]...  相似文献   
226.
Bamboo is one of the fastest growing plants in the world, but their shoot buds develop very slowly. Information about the sugar storage and metabolism during the shoot growth is lacking. In the present study, we determined the activity of sucrose and starch metabolizing enzymes during the developmental period of Fargesia yunnanensis from shoot buds to the young culms that have achieved their full height. The soluble sugars and starch contents were also determined and analyzed in shoot buds and shoots at different developmental stages. The results showed that there were higher sucrose contents in shoot buds than shoots, which coincides with the sweeter taste of shoot buds. As the shoot buds sprouted out of the ground, the starch and sucrose were depleted sharply. Coupled with this, the activity of soluble acid invertase (SAI), cell wall-bound invertase (CWI), sucrose synthase at cleavage direction (SUSYC) and starch phosphorylase (STP) increased significantly in the rapidly elongating internodes. These enzymes dominated the rapid elongation of internodes. The activities of SAI, CWI, SUSYC and STP and adenosine diphosphate-glucose pyrophosphorylase were higher as compared to other enzymes in the shoot buds, but were far lower than those in the developing shoots. The slow growth of shoot buds was correlated with the low activity of these enzymes. These results complement our understanding of the physiological differences between shoot buds and elongating shoots and ascertain the physiological mechanism for the rapid growth of bamboo shoots.  相似文献   
227.
Recent studies have demonstrated that hydrogen sulfide (H2S) produced through the activity of l -cysteine desulfhydrase (DES1) is an important gaseous signaling molecule in plants that could participate in abscisic acid (ABA)-induced stomatal closure. However, the coupling of the DES1/H2S signaling pathways to guard cell movement has not been thoroughly elucidated. The results presented here provide genetic evidence for a physiologically relevant signaling pathway that governs guard cell in situ DES1/H2S function in stomatal closure. We discovered that ABA-activated DES1 produces H2S in guard cells. The impaired guard cell ABA phenotype of the des1 mutant can be fully complemented when DES1/H2S function has been specifically rescued in guard cells and epidermal cells, but not mesophyll cells. This research further characterized DES1/H2S function in the regulation of LONG HYPOCOTYL1 (HY1, a member of the heme oxygenase family) signaling. ABA-induced DES1 expression and H2S production are hyper-activated in the hy1 mutant, both of which can be fully abolished by the addition of H2S scavenger. Impaired guard cell ABA phenotype of des1/hy1 can be restored by H2S donors. Taken together, this research indicated that guard cell in situ DES1 function is involved in ABA-induced stomatal closure, which also acts as a pivotal hub in regulating HY1 signaling.  相似文献   
228.
Yin  Yulin  Zhang  Peijun  Liu  Jia  Wang  Nan  Shang  Xinchi  Zhang  Yilin  Li  Yuehong 《Biological trace element research》2020,194(2):552-559
Biological Trace Element Research - Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments on a global scale. Vitamin C was a widely used vitamin in aquaculture....  相似文献   
229.
The NAD-dependent deacetylase Sirtuin 1 (SIRT1) plays a vital role in leukemogenesis. Nicotinamide (NAM) is the principal NAD+ precursor and a noncompetitive inhibitor of SIRT1. In our study, we showed that NAM enhanced the sensitivity of chronic myeloid leukemia (CML) to doxorubicin (DOX) via SIRT1. We found that SIRT1 high expression in CML patients was associated with disease progression and drug resistance. Exogenous NAM efficiently repressed the deacetylation activity of SIRT1 and induced the apoptosis of DOX-resistant K562 cells (K562R) in a dose-dependent manner. Notably, the combination of NAM and DOX significantly inhibited tumor cell proliferation and induced cell apoptosis. The knockdown of SIRT1 in K562R cells enhanced NAM+DOX-induced apoptosis. SIRT1 rescue in K562R reduced the NAM+DOX-induced apoptosis. Mechanistically, the combinatory treatment significantly increased the cleavage of caspase-3 and PARP in K562R in vitro and in vivo. These results suggest the potential role of NAM in increasing the sensitivity of CML to DOX via the inhibition of SIRT1.  相似文献   
230.
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