全文获取类型
收费全文 | 39815篇 |
免费 | 3297篇 |
国内免费 | 3774篇 |
出版年
2024年 | 35篇 |
2023年 | 420篇 |
2022年 | 570篇 |
2021年 | 1814篇 |
2020年 | 1419篇 |
2019年 | 1718篇 |
2018年 | 1592篇 |
2017年 | 1265篇 |
2016年 | 1660篇 |
2015年 | 2471篇 |
2014年 | 3009篇 |
2013年 | 3182篇 |
2012年 | 3772篇 |
2011年 | 3424篇 |
2010年 | 2214篇 |
2009年 | 1938篇 |
2008年 | 2429篇 |
2007年 | 2011篇 |
2006年 | 1874篇 |
2005年 | 1540篇 |
2004年 | 1476篇 |
2003年 | 1343篇 |
2002年 | 1195篇 |
2001年 | 733篇 |
2000年 | 597篇 |
1999年 | 518篇 |
1998年 | 412篇 |
1997年 | 313篇 |
1996年 | 291篇 |
1995年 | 279篇 |
1994年 | 208篇 |
1993年 | 178篇 |
1992年 | 195篇 |
1991年 | 155篇 |
1990年 | 127篇 |
1989年 | 100篇 |
1988年 | 73篇 |
1987年 | 74篇 |
1986年 | 53篇 |
1985年 | 51篇 |
1984年 | 23篇 |
1983年 | 30篇 |
1982年 | 22篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1967年 | 4篇 |
1965年 | 4篇 |
1962年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Mari Narusaka Yasuyuki Kubo Katsunori Hatakeyama Jun Imamura Hiroshi Ezura Yoshihiko Nanasato Yutaka Tabei Yoshitaka Takano Ken Shirasu Yoshihiro Narusaka 《PloS one》2013,8(2)
A major class of disease resistance (R) genes which encode nucleotide binding and leucine rich repeat (NB-LRR) proteins have been used in traditional breeding programs for crop protection. However, it has been difficult to functionally transfer NB-LRR-type R genes in taxonomically distinct families. Here we demonstrate that a pair of Arabidopsis (Brassicaceae) NB-LRR-type R genes, RPS4 and RRS1, properly function in two other Brassicaceae, Brassica rapa and Brassica napus, but also in two Solanaceae, Nicotiana benthamiana and tomato (Solanum lycopersicum). The solanaceous plants transformed with RPS4/RRS1 confer bacterial effector-specific immunity responses. Furthermore, RPS4 and RRS1, which confer resistance to a fungal pathogen Colletotrichum higginsianum in Brassicaceae, also protect against Colletotrichum orbiculare in cucumber (Cucurbitaceae). Importantly, RPS4/RRS1 transgenic plants show no autoimmune phenotypes, indicating that the NB-LRR proteins are tightly regulated. The successful transfer of two R genes at the family level implies that the downstream components of R genes are highly conserved. The functional interfamily transfer of R genes can be a powerful strategy for providing resistance to a broad range of pathogens. 相似文献
992.
Background
Total hip or knee arthroplasty is an elective procedure that is usually accompanied by substantial blood loss, which may lead to acute anemia. As a result, almost half of total joint arthroplasty patients receive allogeneic blood transfusions (ABT). Many studies have shown that post-operative auto-transfusion (PAT) significantly reduces the need for ABT, but other studies have questioned the efficacy of this method.Methods
The protocol for this trial and supporting CONSORT checklist are available as supporting information; see Checklist S1. To evaluate the efficacy of PAT, we conducted a Cochrane systematic review that combined all available data from randomized controlled trials. Data from the six included trials were pooled for analysis. We then calculated relative risks with 95% confidence intervals (CIs) for dichotomous outcomes and mean differences with 95% CIs for continuous outcomes.Findings and Conclusion
To our knowledge, this is the first meta-analysis to compare the clinical results between PAT and a control in joint replacement patients. This meta-analysis has proven that the use of a PAT reinfusion system reduced significantly the demand for ABT, the number of patients who require ABT and the cost of hospitalization after total knee and hip arthroplasty. This study, together with other previously published data, suggests that PAT drains are beneficial. Larger, sufficiently powered studies are necessary to evaluate the presumed reduction in the incidence of infection as well as DVT after joint arthroplasty with the use of PAT. 相似文献993.
994.
Yu-Jue Wang Wen Liu Chi Chen Li-Meng Yan Jun Song Kun-Yuan Guo Gang Wang Qing-Hong Wu Wei-Wang Gu 《PloS one》2013,8(3)
Background
The radiation-induced energy metabolism dysfunction related to injury and radiation doses is largely elusive. The purpose of this study is to investigate the early response of energy metabolism in small intestinal tissue and its correlation with pathologic lesion after total body X-ray irradiation (TBI) in Tibet minipigs.Methods and Results
30 Tibet minipigs were assigned into 6 groups including 5 experimental groups and one control group with 6 animals each group. The minipigs in these experimental groups were subjected to a TBI of 2, 5, 8, 11, and 14 Gy, respectively. Small intestine tissues were collected at 24 h following X-ray exposure and analyzed by histology and high performance liquid chromatography (HPLC). DNA contents in this tissue were also examined. Irradiation causes pathologic lesions and mitochondrial abnormalities. The Deoxyribonucleic acid (DNA) content-corrected and uncorrected adenosine-triphosphate (ATP) and total adenine nucleotides (TAN) were significantly reduced in a dose-dependent manner by 2–8 Gy exposure, and no further reduction was observed over 8 Gy.Conclusion
TBI induced injury is highly dependent on the irradiation dosage in small intestine and inversely correlates with the energy metabolism, with its reduction potentially indicating the severity of injury. 相似文献995.
Hepatocellular carcinoma is one of the most common malignant neoplasms in the world and is the main cause of death in patients with liver cirrhosis. Surgical intervention is not suitable for majority of hepatocellular carcinoma. Investigation of the effective targeting to the tumor cells is essential for both primary tumors and metastases. Tumor specific cytotoxic T lymphocytes (CTL) have been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern of CTL carrying the lentiviral vectors with the characteristic of adenoviral E1 gene under the control of the cell activation-dependent CD40 ligand promoter (Lenti/hCD40L/E1AB). Following transduction with adenoviral vectors containing chimeric type 5 and type 35 fiber proteins (Ad5/35-TRAIL), these CTLs produced infectious virus when exposed to HepG2 cells. We assessed the therapeutic ability of CTLs using MTT, Western blot and colony formation assay. The novel CTL harboring Lenti/hCD40L/E1AB and Ad5/35-TRAIL caused proliferation inhibition and significant apoptosis in hepatocellular carcinoma cell lines. Thus, the novel CTL may be useful for the development of gene therapy approaches to hepatocellular carcinoma. 相似文献
996.
People can implicitly learn a connection between linguistic forms and meanings, for example between specific determiners (e.g. this, that…) and the type of nouns to which they apply. Li et al (2013) recently found that transfer of form-meaning connections from a concrete domain (height) to an abstract domain (power) was achieved in a metaphor-consistent way without awareness, showing that unconscious knowledge can be abstract and flexibly deployed. The current study aims to determine whether people transfer knowledge of form-meaning connections not only from a concrete domain to an abstract one, but also vice versa, consistent with metaphor representation being bi-directional. With a similar paradigm as used by Li et al, participants learnt form- meaning connections of different domains (concrete vs. abstract) and then were tested on two kinds of generalizations (same and different domain generalization). As predicted, transfer of form-meaning connections occurred bidirectionally when structural knowledge was unconscious. Moreover, the present study also revealed that more transfer occurred between metaphorically related domains when judgment knowledge was conscious (intuition) rather than unconscious (guess). Conscious and unconscious judgment knowledge may have different functional properties. 相似文献
997.
Chunyun Liu Yanhua Li Jiezhong Yu Ling Feng Shaowei Hou Yueting Liu Mingfang Guo Yong Xie Jian Meng Haifei Zhang Baoguo Xiao Cungen Ma 《PloS one》2013,8(2)
We observed the therapeutic effect of Fasudil and explored its mechanisms in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Fasudil, a selective Rho kinase (ROCK) inhibitor, was injected intraperitoneally at 40 mg/kg/d in early and late stages of EAE induction. Fasudil ameliorated the clinical severity of EAE at different stages, and decreased the expression of ROCK-II in spleen, accompanied by an improvement in demyelination and inhibition of inflammatory cells. Fasudil mainly inhibited CD4+IL-17+ T cells in early treatment, but also elevated CD4+IL-10+ regulatory T cells and IL-10 production in late treatment. The treatment of Fasudil shifted inflammatory M1 to anti-inflammatory M2 macrophages in both early and late treatment, being shown by inhibiting CD16/32, iNOS, IL-12, TLR4 and CD40 and increasing CD206, Arg-1, IL-10 and CD14 in spleen. By using Western blot and immunohistochemistry, iNOS and Arg-1, as two most specific markers for M1 and M2, was inhibited or induced in splenic macrophages and spinal cords of EAE mice treated with Fasudil. In vitro experiments also indicate that Fasudil shifts M1 to M2 phenotype, which does not require the participation or auxiliary of other cells. The polarization of M2 macrophages was associated with the decrease of inflammatory cytokine IL-1β, TNF-α and MCP-1. These results demonstrate that Fasudil has therapeutic potential in EAE possibly through inducing the polarization of M2 macrophages and inhibiting inflammatory responses. 相似文献
998.
Myeloperoxidase (MPO) functions as a key molecular component of the host defense system against diverse pathogens. We have previously reported that increased MPO levels and activity is a distinguishing feature of rotenone-exposed glial cells, and that either overactivation or deficiency of MPO leads to pathological conditions in the brain. Here, we provide that modulation of MPO levels in glia by resveratrol confers protective effects on rotenone-induced neurotoxicity. We show that resveratrol significantly reduced MPO levels but did not trigger abnormal nitric oxide (NO) production in microglia and astrocytes. Resveratrol-induced down-regulation of MPO, in the absence of an associated overproduction of NO, markedly attenuated rotenone-triggered inflammatory responses including phagocytic activity and reactive oxygen species production in primary microglia and astrocytes. In addition, impaired responses of primary mixed glia from Mpo
−/− mice to rotenone were relieved by treatment with resveratrol. We further show that rotenone-induced neuronal injury, particularly dopaminergic cell death, was attenuated by resveratrol in neuron-glia co-cultures, but not in neurons cultured alone. Similar regulatory effects of resveratrol on MPO levels were observed in microglia treated with MPP+, another Parkinson’s disease-linked neurotoxin, supporting the beneficial effects of resveratrol on the brain. Collectively, our findings provide that resveratrol influences glial responses to rotenone by regulating both MPO and NO, and thus protects against rotenone-induced neuronal injury. 相似文献
999.
Background and Objective
Emerging evidence indicates that common functional polymorphisms in the estrogen receptor 1 (ESR1) gene may have an impact on an individual’s susceptibility to endometrial cancer, but individually published results are inconclusive. The aim of this meta-analysis is to derive a more precise estimation of the associations between eight polymorphisms in the ESR1 gene and endometrial cancer risk.Methods
A literature search of PubMed, Embase, Web of Science and China Biology Medicine (CBM) databases was conducted on publications published before November 1st, 2012. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Statistical analyses were performed using the STATA 12.0 software.Results
Thirteen case-control studies were included with a total of 7,649 endometrial cancer cases and 16,855 healthy controls. When all the eligible studies were pooled into the meta-analysis, the results indicated that PvuII (C>T) polymorphism was associated with an increased risk of endometrial cancer, especially among Caucasian populations. There were also significant associations between rs3020314 (C>T) polymorphism and an increased risk of endometrial cancer. Furthermore, rs2234670 (S/L) polymorphism may decrease the risk of endometrial cancer. However, no statistically significant associations were found in XbaI (A>G), Codon 325 (C>G), Codon 243 (C>T), VNTR (S/L) and rs2046210 (G>A) polymorphisms.Conclusion
The current meta-analysis suggests that PvuII (C>T) and rs3020314 (C>T) polymorphisms may be risk factors for endometrial cancer, especially among Caucasian populations. 相似文献1000.
The present study investigated whether emotional conflict and emotional conflict adaptation could be triggered by unconscious emotional information as assessed in a backward-masked affective priming task. Participants were instructed to identify the valence of a face (e.g., happy or sad) preceded by a masked happy or sad face. The results of two experiments revealed the emotional conflict effect but no emotional conflict adaptation effect. This demonstrates that emotional conflict can be triggered by unconsciously presented emotional information, but participants may not adjust their subsequent performance trial-by trial to reduce this conflict. 相似文献