全文获取类型
收费全文 | 9897篇 |
免费 | 741篇 |
国内免费 | 820篇 |
出版年
2024年 | 16篇 |
2023年 | 133篇 |
2022年 | 344篇 |
2021年 | 600篇 |
2020年 | 376篇 |
2019年 | 449篇 |
2018年 | 458篇 |
2017年 | 367篇 |
2016年 | 444篇 |
2015年 | 661篇 |
2014年 | 777篇 |
2013年 | 813篇 |
2012年 | 947篇 |
2011年 | 820篇 |
2010年 | 475篇 |
2009年 | 443篇 |
2008年 | 499篇 |
2007年 | 409篇 |
2006年 | 311篇 |
2005年 | 256篇 |
2004年 | 201篇 |
2003年 | 189篇 |
2002年 | 163篇 |
2001年 | 145篇 |
2000年 | 128篇 |
1999年 | 107篇 |
1998年 | 72篇 |
1997年 | 86篇 |
1996年 | 81篇 |
1995年 | 59篇 |
1994年 | 47篇 |
1993年 | 45篇 |
1992年 | 63篇 |
1991年 | 51篇 |
1990年 | 49篇 |
1989年 | 33篇 |
1988年 | 39篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1978年 | 11篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1971年 | 9篇 |
1967年 | 7篇 |
1966年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
Head kidney leukocytes isolated from Atlantic salmon fed either a diet based on fish oil (FO) or soy bean oil (VO) were used in order to evaluate if different lipid sources could contribute to cellular activation of the salmon innate immune system. A specific inhibitor of p38 MAPK, SB202190, was used to investigate the effect of lipopolysaccharide (LPS) signalling in the head kidney leukocytes. The results show that LPS up regulate IL-1β, TNF-α, Cox2 expression in leukocytes isolated from fish fed either diet. The p38 MAPK inhibitor, SB202190, reduced the LPS induced expression of these genes in both dietary groups. In LPS stimulated leukocytes isolated from VO fed fish, SB202190 showed a clear dose dependent inhibitory effect on IL-1β, TNF-α and Cox2 expression. This effect was also observed for Cox2 in leukocytes isolated from FO fed fish. Furthermore, there was a stronger mean induction of Cox2 in LPS stimulated leucocytes isolated from the VO-group compared to LPS stimulated leukocytes isolated from the FO-group. In both dietary groups, LPS stimulation of salmon head kidney leukocytes increased the induction of CD83, a dendrite cell marker, while the inhibitor reduced CD83 expression in the VO fed fish only. The inhibitor also clearly reduced hsp27 expression in VO fed fish. Indicating a p38 MAPK feedback loop, LPS significantly inhibited the expression of p38MAPK itself in both diets, while SB202190 increased p38MAPK expression especially in the VO diet group. hsp70 expression was not affected by any treatment or feed composition. There were also differences in p38MAPK protein phosphorylation comparing treatment groups but no obvious difference comparing the two dietary groups. The results indicate that dietary fatty acids have the ability to modify signalling through p38 MAPK which may have consequences for the fish's ability to handle infections and stress. Signalling through p38MAPK is ligand dependent and affects gene and protein expression differently. 相似文献
952.
Leina Zheng Wenwei Zhang Xingang Chen Jing Ma Weiwei Chen Zhigang Zhao Huqu Zhai Jianmin Wan 《Journal of Plant Biology》2011,54(5):321-328
Protein content (PC) and protein index (PI) play important roles in determining nutritional quality in rice (Oryza sativa L.). We used 71 lines derived from “Asominori/IR24” to analyze the developmental behavior of PC and PI through unconditional
and conditional QTL mapping methods. In all, 10 unconditional QTLs and 6 conditional QTLs for PC, and 11 unconditional QTLs
and 9 conditional QTLs for PI, were identified at four stages of grain filling. More were identified in the first three stages
than at the final stage. Temporal patterns of gene expression for PC and PI differed over time, with several QTLs being expressed
across two or three stages but many being expressed at only one stage. Some of these QTLs were closely linked with maturity
QTLs reported previously. Many QTLs for PC and PI were co-localized, supporting the significant correlation found between
PC and PI. Our results suggest that dynamic QTL mapping might be a valid means for revealing more genetic information about
protein accumulations during seed development. 相似文献
953.
Qian Y Du YH Tang YB Lv XF Liu J Zhou JG Guan YY 《Apoptosis : an international journal on programmed cell death》2011,16(5):468-477
ClC-3 Cl− channel plays an important role in cell volume regulation and cell cycle. In vascular smooth muscle cells, we have found
that ClC-3 was involved in ET-1 induced cell proliferation. The present study was designed to further investigate the role
of ClC-3 Cl− channel in H2O2-induced apoptosis and its underlying mechanisms in rat basilar arterial smooth muscle cell (BASMCs). By using ClC-3 cDNA
and small interference RNA (siRNA) transfection strategy, it was found that overexpression of ClC-3 significantly decreased
the apoptotic rate of H2O2-treated BASMCs and increased the cell viability, whereas silencing of ClC-3 with siRNA produced opposite effects and increased
the apoptotic rate. ClC-3 overexpression decreased cytochrome C release and caspase-3 activation, and increased both the stability
of mitochondrial membrane potential and the ratio of Bcl-2/Bax, whereas silencing of ClC-3 produced opposite effect. Furthermore,
we demonstrated that overexpression of ClC-3 attenuated, whereas silencing of ClC-3 facilitated, the degradation of LaminA,
one of the structural matrix proteins, in BASMCs. Our data suggest that ClC-3 Cl− channel can modulate H2O2-induced apoptosis in BASMCs via the intrinsic, mitochondrial pathway. 相似文献
954.
Severe acute pancreatitis (SAP) is a common disease with a poor prognosis. Heart failure is one cause of SAP patient death.
Intermedin (IMD) is a potent endogenous cardio-protective substance. Administration of exogenous IMD showed beneficial effects
in cardiovascular diseases. The aim of this study was to investigate the myocardial damage in SAP and to determine the therapeutic
potential of IMD for SAP. Using an SAP rat model, we examined endogenous IMD expression following SAP induction, and determined
the effect of IMD on myocardial function, histological morphology, apoptosis-related gene expression, and prognosis. Our results
indicated that the cardiac function and histological structure were significantly disrupted in SAP rats. Infusion of exogenous
IMD significantly preserved cardiac function and ameliorated myocardial damage. Terminal deoxynucleotidyl transferase-mediated
dUTP nick end labeling (TUNEL) revealed that myocardial apoptosis was extensively present in SAP rats, and IMD infusion led
to increased expression of the prosurvival factor Bcl-2, but decreased pro-apoptotic factors Bax and caspase-3. In addition,
IMD infusion also reversed the change of IMD receptor systems in SAP rat heart tissue. Furthermore, we found that IMD infusion
greatly decreased mortality of SAP rats. In conclusion, administration of SAP produced therapeutic effects in SAP through
modulating apoptotic and pro-survival gene expression, inhibiting myocardial apoptosis, preserving cardiac function, and a
useful therapeutic agent for SAP, and provides us an insight for a clinical trial of IMD for treating human severe acute pancreatitis. 相似文献
955.
For alpine plant species, patterns of resource allocation to functional floral traits for pollinator attraction can be highly significant in adaptation to low pollinator abundance and consequent pollen limitation. Increased pollination can be achieved either through a larger floral display or production of more pollen rewards. In this study, variation in resource allocation to different components for pollinator attraction was studied along an altitudinal gradient in Trollius ranunculoides, an obligate self‐incompatible out‐crosser of the Qinghai–Tibet Plateau. We compared resource allocation to conspicuous yellow sepals (which mainly provide visual attraction) and degenerate petals (which provide the major nectar reward) between populations at four altitudes. Furthermore, we investigated the contribution of sepals and petals to pollinator attraction and female reproductive success in an experiment with sepal or petal removal at sites at different altitudes. At the level of single flowers, resource allocation increased to sepals but decreased to petals with increasing altitude. Consistent with these results, sepals contributed much more to visitation rate and seed set than petals, as confirmed in the sepal or petal removal experiment. Sepals and petals contributed to female reproductive success by ensuring visitation rate rather than visitation duration. To alleviate increasing pollen limitation with increasing altitude, resource allocation patterns of T. ranunculoides altered to favour development of sepals rather than petals. This strategy may improve pollination and reproductive success through visual attraction (sepal) rather than nectar reward (petal) over a gradient of decreasing pollinator abundance. 相似文献
956.
Li Z Zhou M Zhang Z Ren L Du L Zhang B Xu H Xin Z 《Functional & integrative genomics》2011,11(1):63-70
Fusarium head blight (scab), primarily caused by Fusarium graminearum, is a devastating disease of wheat (Triticum aestivum L.) worldwide. Wheat sharp eyespot, mainly caused by Rhizoctonia cerealis, is one of the major diseases of wheat in China. The defensin RsAFP2, a small cyteine-rich antifungal protein from radish
(Raphanus sativus), was shown to inhibit growth in vitro of agronomically important fungal pathogens, such as F. graminearum and R. cerealis. The RsAFP2 gene was transformed into Chinese wheat variety Yangmai 12 via biolistic bombardment to assess the effectiveness of the defensin
in protecting wheat from the fungal pathogens in multiple locations and years. The genomic PCR and Southern blot analyses
indicated that RsAFP2 was integrated into the genomes of the transgenic wheat lines and heritable. RT-PCR and Western blot proved that the RsAFP2 was expressed in these transgenic wheat lines. Disease tests showed that four RsAFP2 transgenic lines (RA1–RA4) displayed enhanced resistance to F. graminearum compared to the untransformed Yangmai 12 and the null-segregated plants. Assays on Q-RT-PCR and disease severity showed that
the express level of RsAFP2 was associated with the enhanced resistance degree. Two of these transgenic lines (RA1 and RA2) also exhibited enhanced resistance
to R. cerealis. These results indicated that the expression of RsAFP2 conferred increased resistance to F. graminearum and R. cerealis in transgenic wheat. 相似文献
957.
Slaastad H Wu W Goullart L Kanderova V Tjønnfjord G Stuchly J Kalina T Holm A Lund-Johansen F 《Proteomics》2011,11(23):4578-4582
Antibody array analysis of complex samples requires capture reagents with exceptional specificity. The frequency of antibodies with label-based detection may be as low as 5%. Here, however, we show that as many as 25% of commercially available antibodies are useful when biotinylated cellular proteins are fractionated by size exclusion chromatography (SEC) first. A microsphere multiplex with 1725 antibodies to cellular proteins was added to 24 SEC fractions, labelled with streptavidin and analyzed by flow cytometry (microsphere-based affinity proteomics, MAP) The SEC-MAP approach resolved different targets captured by each antibody as reactivity peaks across the separation range of the SEC column (10-670kDa). Complex reactivity profiles demonstrated that most antibodies bound more than one target. However, specific binding was readily detected as reactivity peaks common for different antibodies to the same protein. We optimized sample preparation and found that amine-reactive biotin rarely inhibited antibody binding when the biotin to lysine ratio was kept below 1:1 during labelling. Moreover, several epitopes that were inaccessible to antibodies in native proteins were unmasked after heat denaturation with 0.1% of SDS. The SEC-MAP format should allow researchers to build multiplexed assays with antibodies purchased for use in e.g. Western blotting. 相似文献
958.
Prlainović NZ Knežević-Jugović ZD Mijin DZ Bezbradica DI 《Bioprocess and biosystems engineering》2011,34(7):803-810
The objective of this paper was the investigation of a suitable Sepabeads? support and method for immobilization of lipase from Candida rugosa. Three different supports were used, two with amino groups, (Sepabeads? EC-EA and Sepabeads? EC-HA), differing in spacer length (two and six carbons, respectively) and one with epoxy group (Sepabeads? EC-EP). Lipase immobilization was carried out by two conventional methods (via epoxy groups and via glutaraldehyde), and
with periodate method for modification of lipase. The results of activity assays showed that lipase retained 94.8% or 87.6%
of activity after immobilization via epoxy groups or with periodate method, respectively, while glutaraldehyde method was
inferior with only 12.7% of retention. The immobilization of lipase, previously modified by periodate oxidation, via amino
groups has proven to be more efficient than direct immobilization of lipase via epoxy groups. In such a way immobilized enzyme
exhibited higher activity at high reaction temperatures and higher thermal stability. 相似文献
959.
Zhe Weng Yang Su Da‐Wei Wang Feng Li Jinhong Du Hui‐Ming Cheng 《Liver Transplantation》2011,1(5):917-922
A simple and scalable method to fabricate graphene‐cellulose paper (GCP) membranes is reported; these membranes exhibit great advantages as freestanding and binder‐free electrodes for flexible supercapacitors. The GCP electrode consists of a unique three‐dimensional interwoven structure of graphene nanosheets and cellulose fibers and has excellent mechanical flexibility, good specific capacitance and power performance, and excellent cyclic stability. The electrical conductivity of the GCP membrane shows high stability with a decrease of only 6% after being bent 1000 times. This flexible GCP electrode has a high capacitance per geometric area of 81 mF cm?2, which is equivalent to a gravimetric capacitance of 120 F g?1 of graphene, and retains >99% capacitance over 5000 cycles. Several types of flexible GCP‐based polymer supercapacitors with various architectures are assembled to meet the power‐energy requirements of typical flexible or printable electronics. Under highly flexible conditions, the supercapacitors show a high capacitance per geometric area of 46 mF cm?2 for the complete devices. All the results demonstrate that polymer supercapacitors made using GCP membranes are versatile and may be used for flexible and portable micropower devices. 相似文献
960.
Tang TT Zhu ZF Wang J Zhang WC Tu X Xiao H Du XL Xia JH Dong NG Su W Xia N Yan XX Nie SF Liu J Zhou SF Yao R Xie JJ Jevallee H Wang X Liao MY Shi GP Fu M Liao YH Cheng X 《PloS one》2011,6(9):e24272