全文获取类型
收费全文 | 46310篇 |
免费 | 3899篇 |
国内免费 | 5010篇 |
专业分类
55219篇 |
出版年
2024年 | 143篇 |
2023年 | 734篇 |
2022年 | 1666篇 |
2021年 | 2661篇 |
2020年 | 1825篇 |
2019年 | 2223篇 |
2018年 | 2034篇 |
2017年 | 1501篇 |
2016年 | 2066篇 |
2015年 | 3055篇 |
2014年 | 3566篇 |
2013年 | 3898篇 |
2012年 | 4541篇 |
2011年 | 4032篇 |
2010年 | 2472篇 |
2009年 | 2215篇 |
2008年 | 2501篇 |
2007年 | 2111篇 |
2006年 | 1864篇 |
2005年 | 1520篇 |
2004年 | 1274篇 |
2003年 | 1098篇 |
2002年 | 919篇 |
2001年 | 742篇 |
2000年 | 644篇 |
1999年 | 644篇 |
1998年 | 354篇 |
1997年 | 352篇 |
1996年 | 357篇 |
1995年 | 347篇 |
1994年 | 292篇 |
1993年 | 207篇 |
1992年 | 309篇 |
1991年 | 218篇 |
1990年 | 172篇 |
1989年 | 170篇 |
1988年 | 100篇 |
1987年 | 97篇 |
1986年 | 67篇 |
1985年 | 79篇 |
1984年 | 37篇 |
1983年 | 40篇 |
1982年 | 27篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Guang-Jin Zhou Yue Zhang Jian Wang Jin-Hu Guo Jun Ni Zhao-Ming Zhong Li-Qun Wang Yong-Jun Dang Jian-Feng Dai Long Yu 《DNA sequence》2004,15(3):219-224
Present work reported the cloning and characterization of a human novel RNA binding gene Partner of NOB1 (PNO1), with a length of 1637bp and a putative open reading frame of 759 bp, isolated from human kidney. It is composed of seven exons and is localized on chromosome 2p14. Western blot showed that the molecular weight of PNO1 is about 35kDa. RT-PCR results in 16 human tissues indicated that PNO1 is expressed mainly in liver, lung, spleen and kidney, slightly in thymus, testis, ovary, respectively, but not in heart, brain, skeletal muscle, placenta, pancreas, prostate, small intestine, colon and peripheral blood leukocytes. GFP fusion expression in mammalian cells exhibited its localization in the nucleus, especially in nucleoli. Subcellular localization of thirteen GFP fusion PNO1 deletion proteins showed that the region of 92-230 aa is solely responsible for its nucleolar retention, and KH domain alone is not sufficient for nucleolar retention. The PNO1 family shows significant conservation in both eukaryotes and prokaryotes. 相似文献
102.
Zhou HL Yang HJ Li YM Wang Y Yan L Guo XL Ba YC Liu S Wang TH 《Neurochemical research》2008,33(5):927-937
Limited information is available regarding the role of endogenous Glial cell line-derived neurotrophic factor (GDNF) in the
spinal cord following transection injury. The present study investigated the possible role of GDNF in injured spinal cords
following transection injury (T9–T10) in adult rats. The locomotor function recovery of animals by the BBB (Basso, Beattie, Bresnahan) scale score showed that
hindlimb support and stepping function increased gradually from 7 days post operation (dpo) to 21 dpo. However, the locomotion
function in the hindlimbs decreased effectively in GDNF-antibody treated rats. GDNF immunoreactivty in neurons in the ventral
horn of the rostral stump was stained strongly at 3 and 7 dpo, and in the caudal stump at 14 dpo, while immunostaining in
astrocytes was also seen at all time-points after transection injury. Western blot showed that the level of GDNF protein underwent
a rapid decrease at 7 dpo in both stumps, and was followed by a partial recovery at a later time-point, when compared with
the sham-operated group. GDNF mRNA-positive signals were detected in neurons of the ventral horn, especially in lamina IX.
No regenerative fibers from corticospinal tract can be seen in the caudal segment near the injury site using BDA tracing technique.
No somatosensory evoked potentials (SEP) could be recorded throughout the experimental period as well. These findings suggested
that intrinsic GDNF in the spinal cord could play an essential role in neuroplasticity. The mechanism may be that GDNF is
involved in the regulation of local circuitry in transected spinal cords of adult rats. 相似文献
103.
Longitudinal studies often feature incomplete response and covariate data. Likelihood-based methods such as the expectation-maximization algorithm give consistent estimators for model parameters when data are missing at random (MAR) provided that the response model and the missing covariate model are correctly specified; however, we do not need to specify the missing data mechanism. An alternative method is the weighted estimating equation, which gives consistent estimators if the missing data and response models are correctly specified; however, we do not need to specify the distribution of the covariates that have missing values. In this article, we develop a doubly robust estimation method for longitudinal data with missing response and missing covariate when data are MAR. This method is appealing in that it can provide consistent estimators if either the missing data model or the missing covariate model is correctly specified. Simulation studies demonstrate that this method performs well in a variety of situations. 相似文献
104.
Although hydrogen peroxide (H2O2) and nitric oxide (NO) can act as an upstream signaling molecule to modulate the dynamic microtubule cytoskeleton during the defense responses to Verticillium dahliae (VD) toxins in Arabidopsis, it is not known the relationship between these two signaling molecules. Here, we show that VD-toxin-induced NO accumulation was dependent on prior H2O2 production, NO is downstream of H2O2 in the signaling process, and that H2O2 acted synergistically with NO to modulate the dynamic microtubule cytoskeleton responses to VD-toxins in Arabidopsis. 相似文献
105.
Yujie Yang Chengshi Huang Zuguo Ge Bengeng Zhou Guangju Su Chunling Liu Yongjun Fei 《Phyton》2022,91(1):129-148
Drought stress negatively impacts growth and physiological processes in plants. The foliar application of glycine betaine (GB) is an effective and low-cost approach to improve the drought tolerance of trees. This study examined the effect of exogenously applied GB on the cell membrane permeability, osmotic adjustment, and antioxidant enzyme activities of Phoebe hunanensis Hand.-Mazz under drought stress. Two levels (0 and 800 mL) of water irrigation were tested under different applied GB concentrations (0, 50, 100, and 200 mM). Drought stress decreased the relative water content by 58.5% while increased the electric conductivity, malondialdehyde, proline, soluble proteins, soluble sugars, and antioxidant enzyme activities (superoxide dismutase, catalase, peroxidase) by up to 62.9%, 42.4%, 87.0%, 19.1%, 60.5%, 68.3%, 71.7%, and 83.8%, respectively, on the 25th day. The foliar application of GB, especially at 100 mM, increased the relative water content of P. hunanensis leaves under drought stress. The concentration of GB from 50 to 100 mM effectively alleviated the improvement of cell membrane permeability and inhibited the accumulation of membrane lipid peroxidation products. Under drought stress, the concentrations of proline, soluble proteins, and soluble sugars in the leaves of P. hunanensis increased as the applied GB concentration was increased and the water stress time was prolonged. Exogenously applied GB decreased oxidative stress and improved antioxidant enzyme activities as compared with treatments without GB application. Furthermore, the physiological and biochemical indexes of P. hunanensis showed a certain dose effect on exogenous GB concentration. These results suggest that GB helps maintain the drought tolerance of P. hunanensis. 相似文献
106.
Man Liu Hongxia Zhang Lu Zhang Xin Liu Simin Zhou Xiaoyi Wang Weilong Zhong Jie Zhang Bangmao Wang Jingwen Zhao Lu Zhou 《International journal of biological sciences》2022,18(1):199
Autoimmune hepatitis (AIH) is an immune-mediated chronic inflammatory liver disease, and its pathogenesis is not fully understood. Our previous study discovered that receptor interacting protein kinase 3 (RIP3) is correlated with serum transaminase levels in AIH patients. However, its role and underlying mechanism in AIH are poorly understood. Here, we detected the increased expression and activation of RIP3 in livers of patients and animal models with AIH. The inhibition of RIP3 kinase by GSK872 prevented concanavalin A (ConA)-induced immune-mediated hepatitis (IMH) by reduced hepatic proinflammatory cytokines and immune cells including Th17 cells and macrophages. Further experiments revealed that RIP3 inhibition resulted in an increase in CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs) with immunoregulatory properties in the liver, spleen, and peripheral blood. Moreover, the depletion of Gr-1+ MDSCs abrogated the protective effect and immune suppression function of GSK872 in ConA-induced IMH. Altogether, our data demonstrate that RIP3 blockade prevents ConA-induced IMH through promoting MDSCs infiltration. Inhibition of RIP3 kinase may be a novel therapeutic avenue for AIH treatment. 相似文献
107.
Long-term use of antibiotics has engendered a large number of resistant pathogens, which pose a serious threat to human health. Here, we investigated the mechanism of fusaricidin antibacterial activity toward Bacillus subtilis and characterized the pathways responsible for drug resistance. We found that σw, an extracytoplasmic function sigma factor, plays an important role in the resistance to fusaricidins during the initial 5 minutes of drug addition. Approximately 18 genes were induced more than 3-fold, of which 66.7% are known to be regulated by σw. Over the following 3 h, fusaricidins induced 194 genes more than three-fold, and most were associated with classes of antibiotic-responsive stimulons. Moreover, the fusaricidin treatment increased the catabolism of fatty and amino acids but strongly repressed glucose decomposition and gluconeogenesis. In summary, our data provide insight into the mechanism of fusaricidin activity, on which we based our suggested strategies for the development of novel antibiotic agents. 相似文献
108.
MAPping Kinase Regulation of ICE1 in Freezing Tolerance 总被引:1,自引:0,他引:1
109.
ABSTRACT: Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft-tissue sarcoma, which primarily occurs deep in the extremities, especially in skeletal muscle, or tendon. EMC of the pleura has been described, however, no case of primary EMC arising from lung has been previously reported. We describe herein, a 51-year-old Asian female initially manifested with signs of severe anemia who presented with a lung mass unrelated to pleura that was morphologically typical EMC, with strong immunoreactivity for vimentin and NSE. Two weeks after resection, the anemia was cured. The patient continued with follow-up, without sign of abnormality 32 months after operation.Virtual slidesThe virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2882199847396682. 相似文献
110.
Zhou Z Sun D Yang A Dong Y Chen Z Wang X Guan X Jiang B Wang B 《Fish & shellfish immunology》2011,31(4):540-547
The complement system has been discovered in invertebrates and vertebrates, and plays a crucial role in the innate defense against common pathogens. As a central component in the complement system, complement component 3 (C3) is an intermediary between innate and adaptive immune system. In this study, a new isoform of C3 in the sea cucumber Apostichopus japonicus, termed AjC3-2 was identified. Its open reading frame (ORF) is 5085?bp and encodes for 1695 amino acids with a putative signal peptide of 20 amino acid residues. The mature protein molecular weight of AjC3-2 was 187.72?kDa. It has a conserved thioester site and a linker R(689)RRR(692) where AjC3-2 is splitted into β and α chain during posttranslational modification. The expression patterns of two distinct sea cucumber C3 genes, AjC3-2 and AjC3, were similar. During the different development stages from unfertilized egg to juvenile of the sea cucumber, the highest expression levels of AjC3-2 and AjC3 genes were both found in late auricularia. In the adult, the highest expression of these two genes was observed in the coelomocytes and followed by the body wall. AjC3-2 and AjC3 genes expression increased significantly at 6?h after the LPS challenge. These results indicated that these two C3 genes play a pivotal role in immune responses to the bacterial infection in sea cucumber. 相似文献