全文获取类型
收费全文 | 39065篇 |
免费 | 2988篇 |
国内免费 | 2930篇 |
专业分类
44983篇 |
出版年
2024年 | 97篇 |
2023年 | 517篇 |
2022年 | 1180篇 |
2021年 | 2164篇 |
2020年 | 1360篇 |
2019年 | 1716篇 |
2018年 | 1727篇 |
2017年 | 1182篇 |
2016年 | 1643篇 |
2015年 | 2401篇 |
2014年 | 2840篇 |
2013年 | 3077篇 |
2012年 | 3593篇 |
2011年 | 3170篇 |
2010年 | 1991篇 |
2009年 | 1620篇 |
2008年 | 1975篇 |
2007年 | 1726篇 |
2006年 | 1591篇 |
2005年 | 1285篇 |
2004年 | 1052篇 |
2003年 | 915篇 |
2002年 | 759篇 |
2001年 | 664篇 |
2000年 | 588篇 |
1999年 | 628篇 |
1998年 | 351篇 |
1997年 | 364篇 |
1996年 | 344篇 |
1995年 | 317篇 |
1994年 | 332篇 |
1993年 | 264篇 |
1992年 | 311篇 |
1991年 | 243篇 |
1990年 | 213篇 |
1989年 | 190篇 |
1988年 | 129篇 |
1987年 | 102篇 |
1986年 | 93篇 |
1985年 | 86篇 |
1984年 | 61篇 |
1983年 | 53篇 |
1982年 | 37篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1976年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
61.
Xiaokang Sun Jie Lv Fei Wang Chenyang Zhang Liangxiang Zhu Guangye Zhang Tongle Xu Zhenghui Luo Haoran Lin Xiaoping Ouyang Chunming Yang Chuluo Yang Gang Li Hanlin Hu 《Liver Transplantation》2024,14(3):2302731
Achieving high-performance in all-small-molecule organic solar cells (ASM-OSCs) significantly relies on precise nanoscale phase separation through domain size manipulation in the active layer. Nonetheless, for ASM-OSC systems, forging a clear connection between the tuning of domain size and the intricacies of phase separation proves to be a formidable challenge. This study investigates the intricate interplay between domain size adjustment and the creation of optimal phase separation morphology, crucial for ASM-OSCs’ performance. It is demonstrated that exceptional phase separation in ASM-OSCs’ active layer is achieved by meticulously controlling the continuity and uniformity of domains via re-packing process. A series of halogen-substituted solvents (Fluorobenzene, Chlorobenzene, Bromobenzene, and Iodobenzene) is adopted to tune the re-packing kinetics, the ASM-OSCs treated with CB exhibited an impressive 16.2% power conversion efficiency (PCE). The PCE enhancement can be attributed to the gradual crystallization process, promoting a smoothly interconnected and uniformly distributed domain size. This, in turn, leads to a favorable phase separation morphology, enhanced charge transfer, extended carrier lifetime, and consequently, reduced recombination of free charges. The findings emphasize the pivotal role of re-packing kinetics in achieving optimal phase separation in ASM-OSCs, offering valuable insights for designing high-performance ASM-OSCs fabrication strategies. 相似文献
62.
Zhongkai Hao Qi Chen Wenrui Dai Yinjuan Ren Yin Zhou Jinlin Yang Sijie Xie Yanbin Shen Jihong Wu Wei Chen Guo Qin Xu 《Liver Transplantation》2020,10(10)
Developing a titanium dioxide (TiO2)‐based anode with superior high‐rate capability and long‐term cycling stability is important for efficient energy storage. Herein, a simple one‐step approach for fabricating blue TiO2 nanoparticles with oxygen vacancies is reported. Oxygen vacancies can enlarge lattice spaces, lower charge transfer resistance, and provide more active sites in TiO2 lattices. As a result, this blue TiO2 electrode exhibits a highly reversible capacity of 50 mAh g?1 at 100 C (16 800 mA g?1) even after 10 000 cycles, which is attributable to the combination of surface capacitive process and remarkable diffusion‐controlled insertion revealed by the kinetic analysis. The strategy of employing oxygen‐deficient nanoparticles may be extended to the design of other robust semiconductor materials as electrodes for energy storage. 相似文献
63.
Xiaoyu Yang Wei Xu Svetlana Dukleska Sabrina Benchaar Selina Mengisen Valentyn Antochshuk Jason Cheung Leslie Mann Zulfia Babadjanova Jason Rowand Rico Gunawan Alexander McCampbell Maribel Beaumont David Meininger Daisy Richardson Alexandre Ambrogelly 《MABS-AUSTIN》2013,5(5):787-794
Monoclonal antibodies constitute a robust class of therapeutic proteins. Their stability, resistance to stress conditions and high solubility have allowed the successful development and commercialization of over 40 antibody-based drugs. Although mAbs enjoy a relatively high probability of success compared with other therapeutic proteins, examples of projects that are suspended due to the instability of the molecule are not uncommon. Developability assessment studies have therefore been devised to identify early during process development problems associated with stability, solubility that is insufficient to meet expected dosing or sensitivity to stress. This set of experiments includes short-term stability studies at 2−8 þC, 25 þC and 40 þC, freeze-thaw studies, limited forced degradation studies and determination of the viscosity of high concentration samples. We present here three case studies reflecting three typical outcomes: (1) no major or unexpected degradation is found and the study results are used to inform early identification of degradation pathways and potential critical quality attributes within the Quality by Design framework defined by US Food and Drug Administration guidance documents; (2) identification of specific degradation pathway(s) that do not affect potency of the molecule, with subsequent definition of proper process control and formulation strategies; and (3) identification of degradation that affects potency, resulting in program termination and reallocation of resources. 相似文献
64.
Bo Cao Yanfeng Qi Yan Yang Xichun Liu Duo Xu Wei Guo Yang Zhan Zhenggang Xiong Allen Zhang Alun R. Wang Xueqi Fu Haitao Zhang Lijing Zhao Jingkai Gu Yan Dong 《PloS one》2014,9(11)
Castration-resistant progression of prostate cancer after androgen deprivation therapies remains the most critical challenge in the clinical management of prostate cancer. Resurgent androgen receptor (AR) activity is an established driver of castration-resistant progression, and upregulation of the full-length AR (AR-FL) and constitutively-active AR splice variants (AR-Vs) has been implicated to contribute to the resurgent AR activity. We reported previously that ginsenoside 20(S)-protopanaxadiol-aglycone (PPD) can reduce the abundance of both AR-FL and AR-Vs. In the present study, we further showed that the effect of PPD on AR expression and target genes was independent of androgen. PPD treatment resulted in a suppression of ligand-independent AR transactivation. Moreover, PPD delayed castration-resistant regrowth of LNCaP xenograft tumors after androgen deprivation and inhibited the growth of castration-resistant 22Rv1 xenograft tumors with endogenous expression of AR-FL and AR-Vs. This was accompanied by a decline in serum prostate-specific antigen levels as well as a decrease in AR levels and mitoses in the tumors. Notably, the 22Rv1 xenograft tumors were resistant to growth inhibition by the next-generation anti-androgen enzalutamide. The present study represents the first to show the preclinical efficacy of PPD in inhibiting castration-resistant progression and growth of prostate cancer. The findings provide a rationale for further developing PPD or its analogues for prostate cancer therapy. 相似文献
65.
Background
Several case-control studies have been performed to examine the association of genetic variants in lysyl oxidase (LOX) with keratoconus. However, the results remained inconclusive and great heterogeneity might exist across populations.Method
A comprehensive literature search for studies that published up to June 25, 2015 was performed. Summary odds ratios (OR) and 95% confidence intervals (CI) of each single nucleotide polymorphism (SNP) were estimated with fixed effects model when I 2<50% in the test for heterogeneity or random effects model when I 2>50%. Publication bias was evaluated using funnel plots and Egger’s test.Results
A total of four studies including 1,467 keratoconus cases and 4,490 controls were involved in this meta-analysis. SNPs rs2956540 and rs10519694 showed significant association with keratoconus, with ORs of 0.71 (95% CI: 0.63–0.80, P = 1.43E-08) and 0.77 (95% CI: 0.61–0.97, P = 0.026), respectively. In contrast, our study lacked sufficient evidences to support the association of rs1800449/rs2288393 with keratoconus across populations.Conclusion
This meta-analysis suggested that two LOX variants, rs2956540 and rs10519694, may affect individual susceptibility to keratoconus, while distinct heterogeneity existed within this locus. Larger-scale and multi-ethnic genetic studies on keratoconus are required to further validate the results. 相似文献66.
67.
68.
心绞痛的痛觉产生机制 总被引:2,自引:0,他引:2
心绞痛是心肌细胞缺血缺氧的信号。损伤的心肌细胞释放致痛物质腺苷、H 、K ,并激活激肽系统产生缓激肽,刺激感觉神经末稍产生神经冲动,经交感、迷走神经进入中枢神经系统,沿内脏感觉传导通路到达大脑皮层形成痛觉。如果缺血程度较轻或疼痛传导通路异常,病人可发生无痛性心肌缺血。 相似文献
69.
Ping Xu Yangxi Zheng Jiujiang Liao Mingyu Hu Yike Yang Baozhen Zhang Mark D. Kilby Huijia Fu Yamin Liu Fumei Zhang Liling Xiong Xiyao Liu Huili Jin Yue Wu Jiayu Huang Tingli Han Li Wen Rufei Gao Yong Fu Xiujun Fan Hongbo Qi Philip N. Baker Chao Tong 《Cell proliferation》2023,56(2)
Pre‐eclampsia (PE) is deemed an ischemia‐induced metabolic disorder of the placenta due to defective invasion of trophoblasts during placentation; thus, the driving role of metabolism in PE pathogenesis is largely ignored. Since trophoblasts undergo substantial glycolysis, this study aimed to investigate its function and regulatory mechanism by AMPK in PE development. Metabolomics analysis of PE placentas was performed by gas chromatography–mass spectrometry (GC–MS). Trophoblast‐specific AMPKα1‐deficient mouse placentas were generated to assess morphology. A mouse PE model was established by Reduced Uterine Perfusion Pressure, and placental AMPK was modulated by nanoparticle‐delivered A769662. Trophoblast glucose uptake was measured by 2‐NBDG and 2‐deoxy‐d‐[3H] glucose uptake assays. Cellular metabolism was investigated by the Seahorse assay and GC–MS.PE complicated trophoblasts are associated with AMPK hyperactivation due not to energy deficiency. Thereafter, AMPK activation during placentation exacerbated PE manifestations but alleviated cell death in the placenta. AMPK activation in trophoblasts contributed to GLUT3 translocation and subsequent glucose metabolism, which were redirected into gluconeogenesis, resulting in deposition of glycogen and accumulation of phosphoenolpyruvate; the latter enhanced viability but compromised trophoblast invasion. However, ablation of AMPK in the mouse placenta resulted in decreased glycogen deposition and structural malformation. These data reveal a novel homeostasis between invasiveness and viability in trophoblasts, which is mechanistically relevant for switching between the ‘go’ and ‘grow’ cellular programs.Pre‐eclampsia (PE) is associated with trophoblast AMPK hyperactivation, presumably due to LKB1 phosphorylation, and glucose uptake is consequently increased via trafficking of GLUT3 from the cytosol to the plasma membrane. Such translocation enhances glycolytic flux and redirects glucose metabolic intermediates into gluconeogenesis, resulting in PEP accumulation, which not only benefits cell survival but also suppresses invasion by repressing MMPs, and thus in turn modulates switching between the ‘go’ and ‘grow’ cellular programs. 相似文献
70.