全文获取类型
收费全文 | 532篇 |
免费 | 45篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 29篇 |
2020年 | 10篇 |
2019年 | 34篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 37篇 |
2014年 | 42篇 |
2013年 | 36篇 |
2012年 | 29篇 |
2011年 | 36篇 |
2010年 | 22篇 |
2009年 | 20篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 10篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有577条查询结果,搜索用时 31 毫秒
81.
The incidence of candidemia and invasive candidiasis have increased markedly due to the increasing number of immunocompromised
patients. There are five major medically important species of Candida with their frequency of isolation in the diminishing order namely Candida albicans, Candida parapsilosis, Candida tropicalis, Candida glabrata and Candida krusei. In addition, there are numerous other species of Candida which differ in their genetic makeup, virulence properties, drug susceptibilities and sugar assimilation capabilities. In
this report, an unusual Candida species was isolated from the blood of two leukaemic patients. Conventional culture and biochemical tests identified the
Candida species as C. parapsilosis. Using fungal-specific oligonucleotide primers ITS1 and ITS4, we managed to amplify the ribosomal RNA gene and its internal
transcribed spacer region from the genomic DNA of these isolates. The PCR products were then purified and subjected to automated
DNA sequencing using BLAST and CLUSTAL sequence analysis identified these isolates to be Candida orthopsilosis. Candida orthopsilosis is a new species recently identified in 2005, being morphologically indistinguishable from C. parapsilosis and was previously classified as a subspecies of C. parapsilosis. This report highlights the importance of complementing traditional culture and biochemical-based identification methods
with DNA-based molecular assays such as PCR as the latter is more superior in terms of its discriminatory power and speed. 相似文献
82.
Adeleh Haghdoost Abdol Ahad Shadparvar Mohammad Taghi Beigi Nasiri Jamal Fayazi 《Small Ruminant Research》2008,80(1-3):91-94
A deterministic bio-economic model was used to estimate the economic values of different traits in Arabic sheep native to the Khuzestan province of Iran. In the studied system, variable costs accounted for about 98.5% of the total costs and among variable costs, feed costs had the highest proportion with 70.7%. Revenue sources included meat, wool, and manure, where meat was the most important one and formed 95.5% of total revenues. Economic value for a trait was estimated as the amount of change in the profit of system as its mean increased by one unit, while the means of other traits were constant. The most important trait in this system was litter size, followed by ewe survival, dressing percentage, and wool weight, respectively. Birth weight had a negative economic value but weight at older ages especially weaning weight and 12-month weight had positive economic values. The sensitivity of economic values of traits was investigated by changing feed and non-feed costs, meat and wool prices by ±10%. Results showed that economic values for dressing percentage and wool weight are not sensitive to change in costs. In addition, changes in marketing and management costs had no effect on the economic value for traits related to body weight in different ages. In general, the economic value for traits which showed sensitivity to the changes of costs, except ewe survival, decreased due to an increase in costs. The economic value for all traits, except birth and wool weight, changed because of a change in meat price. Increasing meat price meant a higher economic importance. Among different factors, meat price fluctuations had the most effect on the economic value of traits. 相似文献
83.
Isolated human neutrophils serve as a model for the in vitro study of host defensive processes as well as the cell biology and biochemistry of primary human cells. We demonstrate that
the requirements of the gelatinbased procedure for neutrophil isolation from whole blood induces the complete loss of secretory
vesicles from in vitro isolated populations, whereas isolation by a dextran-based methodology results in the preservation of this organelle. Following
density fractionation of cellular cavitates, examination of commonly employed plasma membrane marker activities yielded subcellular
localization patterns that were indistinguishable between dextran- or gelatin-isolated populations, indicating both populations
to be otherwise comparable in terms of the relative complexity and large-scale organization of plasma membranes. Given that
the cell surface upregulation of secretory vesicles is implicated as an initial requirement of neutrophil activation as well
as an intrinsic feature of neutrophil priming, we show that dextran and gelatin-isolated neutrophils may be considered to
occupy functionally nonactivated and primed cellular states, respectively. These differences in phenotype can be exploited
in specific ways. We suggest that the gelatin method has technical advantages with regard to the study of neutrophil plasma
membranes. In particular, results from this study indicate the gelatin method to be a reliable and effective preparatory technique
appropriate for tandem use with density fractionation procedures to achieve rapid isolation of plasma membranes that are uncontaminated
by secretory organelles. 相似文献
84.
85.
Calum Brown Dave Murray-Rust Jasper van Vliet Shah Jamal Alam Peter H. Verburg Mark D. Rounsevell 《PloS one》2014,9(12)
The globalisation of trade affects land use, food production and environments around the world. In principle, globalisation can maximise productivity and efficiency if competition prompts specialisation on the basis of productive capacity. In reality, however, such specialisation is often constrained by practical or political barriers, including those intended to ensure national or regional food security. These are likely to produce globally sub-optimal distributions of land uses. Both outcomes are subject to the responses of individual land managers to economic and environmental stimuli, and these responses are known to be variable and often (economically) irrational. We investigate the consequences of stylised food security policies and globalisation of agricultural markets on land use patterns under a variety of modelled forms of land manager behaviour, including variation in production levels, tenacity, land use intensity and multi-functionality. We find that a system entirely dedicated to regional food security is inferior to an entirely globalised system in terms of overall production levels, but that several forms of behaviour limit the difference between the two, and that variations in land use intensity and functionality can substantially increase the provision of food and other ecosystem services in both cases. We also find emergent behaviour that results in the abandonment of productive land, the slowing of rates of land use change and the fragmentation or, conversely, concentration of land uses following changes in demand levels. 相似文献
86.
Jamal T. Manassah 《Plasmonics (Norwell, Mass.)》2016,11(4):995-1002
I compute the transmission coefficient as function of the incident light frequency for a system consisting of a dielectric slab doped with silver nano-spheres sandwiched between two silver parallel plates. Then, I analyze the details of the transmission spectrum identifying the coupled plasmons from the two (doped dielectric and plates) subsystems which dominate the system’s dynamics. 相似文献
87.
Khuram Shahzad Abdul Hai Nadeem Kizilbash Jawaria Ambreen Jamal Alruwaili 《Bioinformation》2013,9(9):471-476
DNA γ is approximately half of the size of Begomovirus DNA. It encodes a γC1 gene that is conserved in position and size. This
gene has the capacity to encode a 13 to 14 kDa protein comprising 118 amino acid residues. It has been shown earlier that γC1
protein is necessary for inducing symptoms of cotton leaf curl disease. The structure for γC1 (CLCuDγ01-Pakistan) is still
unknown. Therefore, a model of γC1 (CLCuDγ01-Pakistan) was developed using DoBo and I-TASSER servers followed by
validation by PROCHECK and VERIFY 3D servers. The developed model provides an insight in a role for this multifunctional
protein in causing Cotton Leaf Curl Disease (CLCuD). A possible function of this protein might be the suppression of RNAsilencing
in cotton plants. 相似文献
88.
89.
Atahar Husein Azfar Jamal Mohammad Zulfazal Ahmed Mohammad Arish Rahat Ali Shams Tabrez Fayyaz Rasool Abdur Rub 《Journal of cellular biochemistry》2018,119(9):7844-7854
Leishmania is a protozoan parasite that resides and replicates in macrophages and causes leishmaniasis. The parasite alters the signaling cascade in host macrophages and evades the host machinery. Small G‐proteins are GTPases, grouped in 5 different families that play a crucial role in the regulation of cell proliferation, cell survival, apoptosis, intracellular trafficking, and transport. In particular, the Ras family of small G‐proteins has been identified to play a significant role in the cellular functions mentioned before. Here, we studied the differential expression of the most important small G‐proteins during Leishmania infection. We found major changes in the expression of different isoforms of Ras, mainly in N‐Ras. We observed that Leishmania donovani infection led to enhanced N‐Ras expression, whereas it inhibited K‐Ras and H‐Ras expression. Furthermore, an active N‐Ras pull‐down assay showed enhanced N‐Ras activity. L donovani infection also increased extracellular signal–regulated kinase 1/2 phosphorylation and simultaneously decreased p38 phosphorylation. In contrast, pharmacological inhibition of Ras led to reduction in the phosphorylation of extracellular signal–regulated kinase 1/2 and enhanced the phosphorylation of p38 in Leishmania‐infected cells, which could lead to increased interleukin‐12 expression and decreased interleukin‐10 expression. Indeed, farnesylthiosalicyclic acid (a Ras inhibitor), when used at the effective level in L donovani–infected macrophages, reduced amastigotes in the host macrophages. Thus, upregulated N‐Ras expression during L donovani infection could be a novel immune evasion strategy of Leishmania and would be a potential target for antileishmanial immunotherapy. 相似文献