全文获取类型
收费全文 | 761篇 |
免费 | 55篇 |
国内免费 | 3篇 |
出版年
2022年 | 14篇 |
2021年 | 23篇 |
2020年 | 13篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 19篇 |
2016年 | 34篇 |
2015年 | 46篇 |
2014年 | 39篇 |
2013年 | 59篇 |
2012年 | 65篇 |
2011年 | 38篇 |
2010年 | 28篇 |
2009年 | 34篇 |
2008年 | 36篇 |
2007年 | 43篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 23篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1960年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有819条查询结果,搜索用时 265 毫秒
21.
Calmodulin was purified from goat erythrocyte hemolysate using heat treatment and Sephadex G-100 gel filtration chromatography. The molecular weight and Stokes, radius of the purified calmodulin was determined. The goat erythrocyte calmodulin stimulated (Ca(2+)-Mg2+)-ATPase but not (Mg2+)-ATPase and (Na(+)-K(+)-Mg2+)-ATPase. The (Ca(2+)-Mg2+)-ATPase of the erythrocyte membrane derived from human, rat, rabbit and pig were significantly stimulated. 相似文献
22.
Primary structure of β-chain of pigeon is presented. It was determined by amino acid sequence analysis of intact β-chain and its peptides obtained by the enzymatic and chemical cleavage. Comparison of amino acid sequence of the chain with other available data shows β 14 Ile, β61 Lys, and β113 Ile as residues specific to pigeon. One important replacement at α1β1 contact is β55 Met→Ser. 相似文献
23.
A 106 kD protein was isolated from skeletal sarcoplasmic reticulum (SR) vesicles and shown to have the properties of SR Ca2+ release channels, including blockade by 5 nM ryanodine. In view of extensive reports that the ryanodine-receptor complex consists of four 565 kD junctional feet proteins (JFPs) and is the 'physiological' Ca2+ release channel, we prepared ryanodine-affinity columns to isolate its receptor site(s). Conditions known to maximize the association and dissociation of ryanodine to SR proteins were respectively used to link, then elute, the receptor(s) from ryanodine-affinity columns. The method purified a protein at about 100 kD from both rabbit skeletal and canine cardiac SR vesicles. The skeletal and cardiac proteins isolated by ryanodine-affinity chromatography were identified as the low molecular weight Ca2+ release channel through their antigenic reaction with an anti-106 kD monoclonal antibody. Upon reconstitution in planar bilayers, both skeletal and cardiac proteins revealed the presence of functional SR Ca2+ release channels. Surprisingly, ryanodine-affinity columns did not retain JFPs but purified 106 kD Ca2+ release channels which are a minor component (0.1-0.3%) of SR proteins. 相似文献
24.
25.
Single pulses of cytoplasmic calcium associated with phagocytosis of individual zymosan particles by macrophages 总被引:1,自引:0,他引:1
L C Meagher B S Moonga C Haslett C L Huang M Zaidi 《Biochemical and biophysical research communications》1991,177(1):460-465
We have measured cytosolic free calcium levels ([Ca++]i) in individual macrophages during the phagocytosis of single zymosan particles. We report here that the contact of a macrophage with zymosan results in a rapid transient elevation of [Ca++]i. Each [Ca++]i pulse is symmetrical lasting for up to 30 seconds. In contrast, macrophage spreading is associated with repetitive [Ca++]i spiking occurring in salvos of up to four smaller spikes, each lasting for between 8 and 18 seconds. These qualitative and kinetic differences might suggest that the role of [Ca++]i in phagocytosis is distinct from its role in spreading. 相似文献
26.
Sumaira Naz Muhammad Zahoor Muhammad Naveed Umar Fatmah S. AlQahtany Yousif M. Elnahas Riaz Ullah 《Saudi Journal of Biological Sciences》2020,27(12):3267-3273
The 2-picolylamine is a simplest analogue of the alkaloid that has secondary and tertiary nitrogen function in its cyclic structure like that of alkaloids that can be derivatized to a number of biologically active compounds. In connection to our previous work, in the present work, three thiourea derivatives (I = 1,3-bis(2-benzyl-3-phenyl-1-(pyridine-2-yl) propyl) thiourea, II = 1,3-bis (pyridin-2-ylmethyl) thiourea, and III = 1-(2-benzyl-3-phenyl-1-(pyridine-2-yl) propyl)-3-phenylthiourea) were synthesized using 2-picolylamine template which is a readily available synthetic analogue of naturally occurring alkaloid. The biological effect of the synthesized derivatives were monitored on the activity of glucose-6-phosphatase in Swiss albino mice (21-days). The derivatives were also tested for their potential toxicity in a 28-days sub-chronic toxicity studies by assessing their effects on different parameters like hematological, serum biochemistry and liver histology. The therapeutic effect of the safe derivative (I) was examined in streptozotocin-induced diabetic mice as well. The derivatives showed inhibition of the enzyme activity from good to an excellent degree. Compound I had the highest inhibition with 21.42 ± 5.113 mg of the released phosphate as compared to that of the positive control group (84.55 ± 3.213 mg). Only I turned out to be safe for use in animals without exerting any toxic or lethal effects on any of the assessed parameters in the used animal model. Compound I efficiently reversed the effects like hyperglycemia, hyperlipidemia and weight loss in the test animals. Out of these three-tested compounds, I was found safe to be use as therapeutic agent in diabetes complications. However, further toxicological studies in other animal models are needed as well. 相似文献
27.
Muhammad Shahid Muhammad Tariq Javed Kashif Tanwir Muhammad Sohail Akram Syeda Khola Tazeen Muhammad Hamzah Saleem Sajid Masood Sadia Mujtaba Hassan Javed Chaudhary 《Physiology and Molecular Biology of Plants》2020,26(12):2417
Cadmium (Cd) is highly toxic metal for plant metabolic processes even in low concentration due to its longer half-life and non-biodegradable nature. The current study was designed to assess the bioremediation potential of a Cd-tolerant phytobeneficial bacterial strain Bacillus sp. SDA-4, isolated, characterized and identified from Chakera wastewater reservoir, Faisalabad, Pakistan, together with spinach (as a test plant) under different Cd regimes. Spinach plants were grown with and without Bacillus sp. SDA-4 inoculation in pots filled with 0, 5 or 10 mg kg−1 CdCl2-spiked soil. Without Bacillus sp. SDA-4 inoculation, spinach plants exhibited reduction in biomass accumulation, antioxidative enzymes and nutrient retention. However, plants inoculated with Bacillus sp. SDA-4 revealed significantly augmented growth, biomass accumulation and efficiency of antioxidative machinery with concomitant reduction in proline and MDA contents under Cd stress. Furthermore, application of Bacillus sp. SDA-4 assisted the Cd-stressed plants to sustain optimal levels of essential nutrients (N, P, K, Ca and Mg). It was inferred that the characterized Cd-tolerant PGPR strain, Bacillus sp. SDA-4 has a potential to reduce Cd uptake and lipid peroxidation which in turn maintained the optimum balance of nutrients and augmented the growth of Cd-stressed spinach. Analysis of bioconcentration factor (BCF) and translocation factor (TF) revealed that Bacillus sp. SDA-4 inoculation with spinach sequestered Cd in rhizospheric zone. Research outcomes are important for understanding morpho-physio-biochemical attributes of spinach-Bacillus sp. SDA-4 synergy which might provide efficient strategies to decrease Cd retention in edible plants and/or bioremediation of Cd polluted soil colloids. 相似文献
28.
Shazmeen Aslam Irfan Khan Fatima Jameel Midhat Batool Zaidi Asmat Salim 《World journal of stem cells》2020,12(12):1652-1666
BACKGROUNDImpaired wound healing can be associated with different pathological states. Burn wounds are the most common and detrimental injuries and remain a major health issue worldwide. Mesenchymal stem cells (MSCs) possess the ability to regenerate tissues by secreting factors involved in promoting cell migration, proliferation and differentiation, while suppressing immune reactions. Preconditioning of MSCs with small molecules having cytoprotective properties can enhance the potential of these cells for their use in cell-based therapeutics.AIMTo enhance the therapeutic potential of MSCs by preconditioning them with isorhamnetin for second degree burn wounds in rats.METHODSHuman umbilical cord MSCs (hU-MSCs) were isolated and characterized by surface markers, CD105, vimentin and CD90. For preconditioning, hU-MSCs were treated with isorhamnetin after selection of the optimized concentration (5 µmol/L) by cytotoxicity analysis. The migration potential of these MSCs was analyzed by the in vitro scratch assay. The healing potential of normal, and preconditioned hU-MSCs was compared by transplanting these MSCs in a rat model of a second degree burn wound. Normal, and preconditioned MSCs (IH + MSCs) were transplanted after 72 h of burn injury and observed for 2 wk. Histological and gene expression analyses were performed on day 7 and 14 after cell transplantation to determine complete wound healing.RESULTSThe scratch assay analysis showed a significant reduction in the scratch area in the case of IH + MSCs compared to the normal untreated MSCs at 24 h, while complete closure of the scratch area was observed at 48 h. Histological analysis showed reduced inflammation, completely remodeled epidermis and dermis without scar formation and regeneration of hair follicles in the group that received IH + MSCs. Gene expression analysis was time dependent and more pronounced in the case of IH + MSCs. Interleukin (IL)-1β, IL-6 and Bcl-2 associated X genes showed significant downregulation, while transforming growth factor β, vascular endothelial growth factor, Bcl-2 and matrix metallopeptidase 9 showed significant upregulation compared to the burn wound, showing increased angiogenesis and reduced inflammation and apoptosis.CONCLUSIONPreconditioning of hU-MSCs with isorhamnetin decreases wound progression by reducing inflammation, and improving tissue architecture and wound healing. The study outcome is expected to lead to an improved cell-based therapeutic approach for burn wounds. 相似文献
29.
Zahoor Ahmad Ejaz Ahmad Waraich Muhammad Zia ur Rehman Muhammad Ashar Ayub Muhammad Usman Hesham Alharby Atif Bamagoos Celaleddin Barutçular Muhammad Ali Raza Fatih Çiğ Ayman El Sabagh 《Phyton》2021,90(2):503-514
Water is essential for the growth period of crops; however, water unavailability badly affects the growth and physiological attributes of crops, which considerably reduced the yield and yield components in crops. Therefore, a pot
experiment was conducted to investigate the effect of foliar phosphorus (P) on morphological, gas exchange, biochemical traits, and phosphorus use efficiency (PUE) of maize (Zea mays L.) hybrids grown under normal as well as water
deficit situations at the Department of Agronomy, University of Agriculture Faisalabad, Pakistan in 2014. Two different
treatments (control and P @ 8 kg ha−1
) and four hybrids (Hycorn, 31P41, 65625, and 32B33) of maize were tested by
using a randomized complete block design (RCBD) with three replications. Results showed that the water stress caused
a remarkable decline in total soluble protein (9.7%), photosynthetic rate (9.4%) and transpiration rate (13.4%), stomatal
conductance (10.2%), and internal CO2 rate (20.4%) comparative to well-watered control. An increase of 37.1%, 36.8%,
and 24.5% were recorded for proline, total soluble sugar, and total free amino acid, respectively. However, foliar P
application minimized the negative impact of drought by improving plant growth, physio-biochemical attributes,
and PUE in maize plants under water stress conditions. Among the hybrids tested, the hybrid 6525 performed better
both under stress and non-stress conditions. These outcomes confirmed that the exogenous application of P improved
drought stress tolerance by modulating growth, physio-biochemical attributes, and PUE of maize hybrids. 相似文献
30.