全文获取类型
收费全文 | 7214篇 |
免费 | 564篇 |
国内免费 | 432篇 |
专业分类
8210篇 |
出版年
2024年 | 19篇 |
2023年 | 95篇 |
2022年 | 226篇 |
2021年 | 351篇 |
2020年 | 275篇 |
2019年 | 310篇 |
2018年 | 292篇 |
2017年 | 214篇 |
2016年 | 322篇 |
2015年 | 435篇 |
2014年 | 492篇 |
2013年 | 520篇 |
2012年 | 628篇 |
2011年 | 599篇 |
2010年 | 333篇 |
2009年 | 334篇 |
2008年 | 364篇 |
2007年 | 340篇 |
2006年 | 297篇 |
2005年 | 222篇 |
2004年 | 205篇 |
2003年 | 204篇 |
2002年 | 159篇 |
2001年 | 124篇 |
2000年 | 114篇 |
1999年 | 92篇 |
1998年 | 48篇 |
1997年 | 62篇 |
1996年 | 69篇 |
1995年 | 45篇 |
1994年 | 50篇 |
1993年 | 35篇 |
1992年 | 61篇 |
1991年 | 42篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 31篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有8210条查询结果,搜索用时 15 毫秒
71.
The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5–5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. 相似文献
72.
Reading is an important part of our daily life, and rapid responses to emotional words have received a great deal of research interest. Our study employed rapid serial visual presentation to detect the time course of emotional noun processing using event-related potentials. We performed a dual-task experiment, where subjects were required to judge whether a given number was odd or even, and the category into which each emotional noun fit. In terms of P1, we found that there was no negativity bias for emotional nouns. However, emotional nouns elicited larger amplitudes in the N170 component in the left hemisphere than did neutral nouns. This finding indicated that in later processing stages, emotional words can be discriminated from neutral words. Furthermore, positive, negative, and neutral words were different from each other in the late positive complex, indicating that in the third stage, even different emotions can be discerned. Thus, our results indicate that in a three-stage model the latter two stages are more stable and universal. 相似文献
73.
Guomiao Shen Chitra Upadhyay Jing Zhang Ruimin Pan Susan Zolla-Pazner Xiang-Peng Kong Catarina E. Hioe 《PloS one》2015,10(10)
HIV-1 envelope glycoproteins (Env) are the only viral antigens present on the virus surface and serve as the key targets for virus-neutralizing antibodies. However, HIV-1 deploys multiple strategies to shield the vulnerable sites on its Env from neutralizing antibodies. The V1V2 domain located at the apex of the HIV-1 Env spike is known to encompass highly variable loops, but V1V2 also contains immunogenic conserved elements recognized by cross-reactive antibodies. This study evaluates human monoclonal antibodies (mAbs) against V2 epitopes which overlap with the conserved integrin α4β7-binding LDV/I motif, designated as the V2i (integrin) epitopes. We postulate that the V2i Abs have weak or no neutralizing activities because the V2i epitopes are often occluded from antibody recognition. To gain insights into the mechanisms of the V2i occlusion, we evaluated three elements at the distal end of the V1V2 domain shown in the structure of V2i epitope complexed with mAb 830A to be important for antibody recognition of the V2i epitope. Amino-acid substitutions at position 179 that restore the LDV/I motif had minimal effects on virus sensitivity to neutralization by most V2i mAbs. However, a charge change at position 153 in the V1 region significantly increased sensitivity of subtype C virus ZM109 to most V2i mAbs. Separately, a disulfide bond introduced to stabilize the hypervariable region of V2 loop also enhanced virus neutralization by some V2i mAbs, but the effects varied depending on the virus. These data demonstrate that multiple elements within the V1V2 domain act independently and in a virus-dependent fashion to govern the antibody recognition and accessibility of V2i epitopes, suggesting the need for multi-pronged strategies to counter the escape and the shielding mechanisms obstructing the V2i Abs from neutralizing HIV-1. 相似文献
74.
Hypertension is an independent risk factor for the progression of chronic renal failure, and oxidative stress plays a critical role in hypertensive renal damage. Forkbox O1(FoxO1) signaling protects cells against oxidative stress and may be a useful target for treating oxidative stress-induced hypertension. Tongxinluo is a traditional Chinese medicine with cardioprotective and renoprotective functions. Therefore, this study aimed to determine the effects of Tongxinluo in hypertensive renal damage in spontaneously hypertensive rats(SHRs)and elucidate the possible involvement of oxidative stress and FoxO1 signaling in its molecular mechanisms. SHRs treated with Tongxinluo for 12 weeks showed a reduction in systolic blood pressure. In addition to increasing creatinine clearance, Tongxinluo decreased urinary albumin excretion, oxidative stress injury markers including malondialdehyde and protein carbonyls, and expression of nicotinamide adenine dinucleotide phosphate oxidase subunits and its activity in SHR kidneys. While decreasing phosphorylation of FoxO1, Tongxinluo also inhibited the phosphorylation of extracellular signal-regulated kinase1/2 and p38 and enhanced manganese superoxide dismutase and catalase activities in SHR kidneys. Furthermore, histology revealed attenuation of glomerulosclerosis and renal podocyte injury, while Tongxinluo decreased the expression of α-smooth muscle actin, extracellular matrixprotein, transforming growth factor β1 and small mothers against decapentaplegic homolog 3,and improved tubulointerstitial fibrosis in SHR kidneys. Finally, Tongxinluo inhibited inflammatory cell infiltration as well as expression of tumor necrosis factor-α and interleukin-6. In conclusion, Tongxinluo protected SHRs against hypertension-induced renal injury by exerting antioxidant, antifibrotic, and anti-inflammatory activities. Moreover, the underlying mechanisms of these effects may involve inhibition of oxidative stress and functional activation of FoxO1 signaling. 相似文献
75.
76.
Bong Jin Kim Kyung Seob Song Hyun-Hee Kong Hee-Jae Cha Meesun Ock 《The Korean journal of parasitology》2014,52(1):85-87
We encountered a patient with heavy Hymenolepis nana infection. The patient was a 44-year-old Korean man who had suffered from chronic hepatitis (type B) for 15 years. A large number of H. nana adult worms were found during colonoscopy that was performed as a part of routine health screening. The parasites were scattered throughout the colon, as well as in the terminal ileum, although the patient was immunocompetent. Based on this study, colonoscopy may be helpful for diagnosis of asymptomatic H. nana infections. 相似文献
77.
Anli Yang Fu Peng Lewei Zhu Xing Li Shunling Ou Zhongying Huang Song Wu Cheng Peng Peng Liu Yanan Kong 《Cell death & disease》2021,12(8)
Melatonin has been reported to have tumor-suppressive effects via comprehensive molecular mechanisms, and long non-coding RNAs (lncRNAs) may participate in this process. However, the mechanism by which melatonin affects the function of lncRNAs in triple-negative breast cancer (TNBC), the most aggressive subtype of breast cancer, is still unknown. Therefore, we aimed to investigate the differentially expressed mRNAs and lncRNAs in melatonin-treated TNBC cells and the interaction mechanisms. Microarray analyses were performed to identify differentially expressed mRNAs and lncRNAs in TNBC cell lines after melatonin treatment. To explore the functions and underlying mechanisms of the mRNAs and lncRNAs candidates, a series of in vitro experiments were conducted, including CCK-8, Transwell, colony formation, luciferase reporter gene, and RNA immunoprecipitation (RIP) assays, and mouse xenograft models were established. We found that after melatonin treatment, FUNDC1 and lnc049808 downregulated in TNBC cell lines. Knockdown of FUNDC1 and lnc049808 inhibited TNBC cell proliferation, invasion, and metastasis. Moreover, lnc049808 and FUNDC1 acted as competing endogenous RNAs (ceRNAs) for binding to miR-101. These findings indicated that melatonin inhibited TNBC progression through the lnc049808-FUNDC1 pathway and melatonin could be used as a potential therapeutic agent for TNBC.Subject terms: Breast cancer, Non-coding RNAs 相似文献
78.
Chen X Shang H Qiu X Fujiwara N Cui L Li XM Gao TM Kong J 《Neurochemical research》2012,37(4):835-845
Converging evidence indicates that SOD1 aggregation is a common feature of mutant SOD1-linked fALS, and seems to be directly
related to the gain-of-function toxic property. However, the mechanism inducing the aggregation is not understood. To study
the contribution of oxidative modification of cysteine residues in SOD1 aggregation, we systematically examined the redox
state of SOD1 cysteine residues in the G37R transgenic mouse model at different stages of the disease and under oxidative
stress induced by H2O2. Our data suggest that under normal circumstance, cysteine 111 residue in SOD1 is free; however, under oxidative stress,
it is prone to oxidative modification by providing the thiolate anion (S−). With the progression of the disease, increased
levels of oxidative insults facilitated the oxidation of thiol groups of cysteine residues; human mutant SOD1 could generate
an upper shift band in reducing SDS-PAGE, which turned out to be a Cys111-peroxidized SOD1 species. We also detected the formation
of SOD1 multimers at different stages of the disease, and found that accumulated oxidative stress facilitated the formation
of aggregates, which were not mediated by disulfide bond. This oxidative modification of cysteine 111 therefore promotes the
formation of disulfide bond-independent aggregation of SOD1. 相似文献
79.
Microarray technology is a useful tool for nucleic acid detection and has been widely used in biology and related research fields. However, the procedure is labor intensive and time consuming. Microfluidic chip-based microarrays save time with better performance, but the low spot density and probe number limit its applications. To develop high performance microarrays with high spot density within a microchannel, a method is reported here for preparing microarrays in a capillary by generating probe droplet arrays. The probes in droplets are immobilized onto the inner wall of the capillary to form a one-dimensional probe array, and then a sample solution is introduced to hybridize with the probe array. The effect of the capillary's inner diameter was evaluated to realize a high-density probe array. The processes of array generation and probe immobilization were studied to avoid possible cross contamination. The background from probe immobilization during the array generation and incubation was quantified to assure sensitivity. Multiple sample detection was also demonstrated within one capillary. The capillary based microarray assay had high spot density, easy fabrication, fast detection, high sensitivity and multiple sample capacity. 相似文献
80.
<正>生物多样性是怎么产生的?对于这个问题,不同的人会有不同的答案。生态学家也许会认为是群落和生态系统中各个组分(即物种)在数目、分布和功能上的变化造成的,群体遗传学家则可能会认为是物种在基因数目、等位基因频率以及核苷酸多态 相似文献