全文获取类型
收费全文 | 9140篇 |
免费 | 687篇 |
国内免费 | 768篇 |
专业分类
10595篇 |
出版年
2024年 | 18篇 |
2023年 | 127篇 |
2022年 | 293篇 |
2021年 | 503篇 |
2020年 | 307篇 |
2019年 | 438篇 |
2018年 | 399篇 |
2017年 | 251篇 |
2016年 | 425篇 |
2015年 | 588篇 |
2014年 | 696篇 |
2013年 | 784篇 |
2012年 | 882篇 |
2011年 | 760篇 |
2010年 | 436篇 |
2009年 | 432篇 |
2008年 | 454篇 |
2007年 | 396篇 |
2006年 | 357篇 |
2005年 | 257篇 |
2004年 | 248篇 |
2003年 | 202篇 |
2002年 | 148篇 |
2001年 | 133篇 |
2000年 | 121篇 |
1999年 | 102篇 |
1998年 | 100篇 |
1997年 | 91篇 |
1996年 | 83篇 |
1995年 | 71篇 |
1994年 | 64篇 |
1993年 | 46篇 |
1992年 | 78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
21.
22.
Fragile X syndrome (FX), the most common heritable cause of mental retardation and autism, is a developmental disorder characterized by physical, cognitive, and behavioral deficits. FX results from a trinucleotide expansion mutation in the fmr1 gene that reduces levels of fragile X mental retardation protein (FMRP). Although research efforts have focused on FMRP's impact on mGluR signaling, how the loss of FMRP leads to the individual symptoms of FX is not known. Previous studies on human FX blood cells revealed alterations in the cyclic adenosine 3', 5'-monophosphate (cAMP) cascade. We tested the hypothesis that cAMP signaling is altered in the FX nervous system using three different model systems. Induced levels of cAMP in platelets and in brains of fmr1 knockout mice are substantially reduced. Cyclic AMP induction is also significantly reduced in human FX neural cells. Furthermore, cAMP production is decreased in the heads of FX Drosophila and this defect can be rescued by reintroduction of the dfmr gene. Our results indicate that a robust defect in cAMP production in FX is conserved across species and suggest that cAMP metabolism may serve as a useful biomarker in the human disease population. Reduced cAMP induction has implications for the underlying causes of FX and autism spectrum disorders. Pharmacological agents known to modulate the cAMP cascade may be therapeutic in FX patients and can be tested in these models, thus supplementing current efforts centered on mGluR signaling. 相似文献
23.
24.
ABSTRACT: OBJECTIVE: To study the clinico-pathological characteristics of Langerhans cell sarcoma (LCS) which involving epidermis. METHODS: A case of primary multifocal LCS was analyzed in histopathology and immunophenotype. RESULTS: A 41-year-old man with multifocal cutaneous LCS involving the inguina and waist was reported. Clinical and pathology data were available. Neoplastic cells with markedly malignant cytological features were observed. Tumor cells exhibited irregular shape with abundant and eosinophilic red staining cytoplasm; large, irregular-shaped, showing lobulated or dented nucleus and some cells with a longitudinal nuclear groove and prominent nucleoli. The tumor cells expressed CD1a, Langerin (CD207), S-100 protein, CD68 and vimentin, and did not express pan-T or B cell markers and epithelial markers. The patient died less than 1 year after diagnosis due to local recurrence and metastasis to the lung, despite the administration of local radiation and chemotherapy. CONCLUSIONS: LCS is a tumor with markedly malignant cytological features that originates from Langerhans cells. Primary multifocal neoplasms involving epidermis is even rare. Accurate diagnosis is based on the histopathological and immunohistochemical of the tumor cells.Virtual slideThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1182345104754765. 相似文献
25.
26.
microRNAs (miRNAs) have been revealed to participate in the pathological process of atherosclerosis (AS). However, the exact role of miR-338-3p, a target miRNA of BMP and activin membrane-bound inhibitor (BAMBI), and its possible molecular mechanism in AS remain unidentified. In this study, we found that BAMBI was significantly decreased, whereas miR-338-3p increased in patients with AS and oxidized low-density lipoprotein (ox-LDL)-induced HUVEC cells. Furthermore, overexpression of miR-338-3p significantly decreased cell viability and elevated cell apoptosis, whereas its inhibition significantly promoted cell viability and inhibited cell apoptosis in ox-LDL-induced HUVEC cells. Moreover, miR-338-3p overexpression increased TGF-β/Smad pathway activation in ox-LDL-induced HUVEC cells. A dual-luciferase reporter assay confirmed the direct interaction between miR-338-3p and the 3′-untranslated region of BAMBI messenger RNA. Furthermore, the suppression of BAMBI ameliorated the effect of miR-338-3p inhibition against ox-LDL-induced HUVEC cell injury. In conclusion, our study thus suggests that miR-338-3p promoted ox-LDL-induced HUVEC cell injury by targeting BAMBI and activating the TGF-β/Smad pathway, which may provide a novel and promising therapeutic target for AS. 相似文献
27.
用鲜花循环式动态顶空技术采集红厚壳鲜花的香气成分,TCT-GC-MS联用技术分析鉴定。4-羟基-2-丁酮,双烯酮,1、2-环氧-2-甲基丁烷,1、2-环氧-3-甲基丁烷,2-乙基戊烷,3-己醇,甲基环戊烷,2-丁醇等24个成分被检测出,占总离子流出峰面积的90.28%。并对结果进行了分析讨论。 相似文献
28.
29.
Hai-Long Wang Tie-E Zhang Li-Tian Yin Min Pang Li Guan Hong-Li Liu Jian-Hong Zhang Xiao-Li Meng Ji-Zhong Bai Guo-Ping Zheng Guo-Rong Yin 《PloS one》2014,9(9)
Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects a variety of mammals, including humans. An effective vaccine for this parasite is therefore needed. In this study, RH strain T. gondii rhoptry protein 17 was expressed in bacteria as a fusion with glutathione S-transferase (GST) and the recombinant proteins (rTgROP17) were purified via GST-affinity chromatography. BALB/c mice were nasally immunised with rTgROP17, and induction of immune responses and protection against chronic and lethal T. gondii infections were investigated. The results revealed that mice immunised with rTgROP17 produced high levels of specific anti-rTgROP17 IgGs and a mixed IgG1/IgG2a response of IgG2a predominance. The systemic immune response was associated with increased production of Th1 (IFN-γand IL-2) and Th2 (IL-4) cytokines, and enhanced lymphoproliferation (stimulation index, SI) in the mice immunised with rTgROP17. Strong mucosal immune responses with increased secretion of TgROP17-specific secretory IgA (SIgA) in nasal, vaginal and intestinal washes were also observed in these mice. The vaccinated mice displayed apparent protection against chronic RH strain infection as evidenced by their lower liver and brain parasite burdens (59.17% and 49.08%, respectively) than those of the controls. The vaccinated mice also exhibited significant protection against lethal infection of the virulent RH strain (survival increased by 50%) compared to the controls. Our data demonstrate that rTgROP17 can trigger strong systemic and mucosal immune responses against T. gondii and that ROP17 is a promising candidate vaccine for toxoplasmosis. 相似文献
30.
Friederike Cuello Manu Shankar-Hari Ursula Mayr Xiaoke Yin Melanie Marshall Gonca Suna Peter Willeit Sarah R. Langley Tamani Jayawardhana Tanja Zeller Marius Terblanche Ajay M. Shah Manuel Mayr 《Molecular & cellular proteomics : MCP》2014,13(10):2545-2557
In an endotoxaemic mouse model of sepsis, a tissue-based proteomics approach for biomarker discovery identified long pentraxin 3 (PTX3) as the lead candidate for inflamed myocardium. When the redox-sensitive oligomerization state of PTX3 was further investigated, PTX3 accumulated as an octamer as a result of disulfide-bond formation in heart, kidney, and lung—common organ dysfunctions seen in patients with sepsis. Oligomeric moieties of PTX3 were also detectable in circulation. The oligomerization state of PTX3 was quantified over the first 11 days in critically ill adult patients with sepsis. On admission day, there was no difference in the oligomerization state of PTX3 between survivors and non-survivors. From day 2 onward, the conversion of octameric to monomeric PTX3 was consistently associated with a greater survival after 28 days of follow-up. For example, by day 2 post-admission, octameric PTX3 was barely detectable in survivors, but it still constituted more than half of the total PTX3 in non-survivors (p < 0.001). Monomeric PTX3 was inversely associated with cardiac damage markers NT-proBNP and high-sensitivity troponin I and T. Relative to the conventional measurements of total PTX3 or NT-proBNP, the oligomerization of PTX3 was a superior predictor of disease outcome.Severe sepsis is a common acute illness in intensive care units (ICUs)1 and is associated with high mortality rates and chronic morbidity. When it is associated with hypotension (termed septic shock), the mortality rate is very high (50% to 80%). Cardiovascular dysfunction during sepsis is multifactorial and often associated with minimal loss of myocardial tissue, but with the release of myocardial-specific markers such as troponins. A key unmet clinical need is the availability of a biomarker that predicts myocardial dysfunction early, monitors response to treatment, and thus identifies a cohort of patients at higher risk of septic shock to aid in targeted interventions and improve outcome (1).In the present study, we used proteomics for biomarker discovery. Over the past decade, the field of proteomics has made impressive progress. Plasma and serum, however, are the most complex proteomes of the human body (2), and less abundant proteins tend to be missed in untargeted proteomics analyses of body fluids (3). Thus, we pursued an alternative strategy: the application of proteomics to diseased tissue (4), in which the potential biomarkers are less dilute and have a less uncertain cellular origin (5–7). We employed a solubility-based protein-subfractionation methodology to analyze inflammatory proteins that are retained with sepsis tissue. This innovative proteomics approach shall reveal inflammatory molecules that reside and persist within inflamed tissue. We hypothesized that proteins that accumulate in the susceptible tissues are more likely to be biomarker candidates for organ dysfunction than proteins that just circulate in plasma or serum. We then validated our proteomics findings in the preclinical model using samples from sepsis patients admitted to ICUs. 相似文献