全文获取类型
收费全文 | 908篇 |
免费 | 29篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 32篇 |
2021年 | 52篇 |
2020年 | 15篇 |
2019年 | 27篇 |
2018年 | 28篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 43篇 |
2014年 | 48篇 |
2013年 | 68篇 |
2012年 | 77篇 |
2011年 | 62篇 |
2010年 | 37篇 |
2009年 | 18篇 |
2008年 | 29篇 |
2007年 | 48篇 |
2006年 | 30篇 |
2005年 | 33篇 |
2004年 | 32篇 |
2003年 | 29篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1981年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有938条查询结果,搜索用时 78 毫秒
121.
The centrifugation on discontinued Percoll gradient is a technique of sperm preparation, which has enabled better success of in-vitro fertilization. In this work, we have analysed the movements of spermatozoa separated in different Percoll fractions after 4 hours of incubation at 37°C and under 5% of CO2. These measures are made by computer assisted videomicrography (Cell Soft). From this study, we notice that the more the Percoll concentration increases, the greater is the curvilinear velocity, the linearity and the lateral amplitude of the head. The 100% and 90% Percoll fractions help to get spermatozoa with good movement features, indicating the use of this technique in medically assisted procreation. 相似文献
122.
Although diethylcarbamazine citrate (DEC) is successful drug in eliminating human filariasis, yet, its mode of action is still debatable. Herein, the effect of DEC to treat albino rats infected with the animal filarial parasite Setaria equina was tested. Microfilarial (mf) counts and sections from liver, lung, kidney as well as spleen were investigated at different time points after treatment by light microscopy. After 45 and 300 min of treatment, a significant decrease in blood mf was observed accompanied by adherence of degenerated mf to both kupffer cells and leukocyte in liver sections. In lung sections, loss of sheath was observed at 45 min, while degeneration was observed at later time points. In kidney sections, more mf counts and less matrix were observed in the glomeruli at all time points after treatment. Degenerated mf were observed in spleen sections only at, late time point, 480 min after treatment. In conclusion, one of the possible mechanisms by which DEC reduces blood microfilarial count is trapping larvae in organs and killing them through cellular adherence. 相似文献
123.
124.
Functional responses of the wolf spider, Pardosa pseudoannulata (Boesenberg et Strand) attacking the rice brown planthopper, Nilaparvata lugens (Stål.), and the mirid predator Cyrtorhinus lividipennis Reuter were both those of Holling Type II. The attack rate was higher and handling time lower for C. lividipennis. However, when caged with the two prey, the wolf spider showed a significant preference for N. lugens at a lower prey proportion. Proportions of prey attacked were significantly different from the expected ratios of prey available as well as from the predicted preferences derived from the functional response parameters. As proportions of N. lugens attacked changed from greater to less than expected as the proportions of N. lugens available increased, a “reverse switch” behaviour seems to be evident. 相似文献
125.
A R Saad D P Stephens L A Bennett N Charkoudian W A Kosiba J M Johnson 《Journal of applied physiology》2001,91(6):2487-2492
The distribution of the reflex effects of isometric exercise on cutaneous vasomotor and sudomotor function is not clear. We examined the effects of isometric exercise by different muscle masses on skin blood flow (SkBF) and sweat rate (SR) in nonglabrous skin and in glabrous skin. The latter contains arteriovenous anastomoses (AVAs), which cause large fluctuations in SkBF. SkBF was measured by laser-Doppler flowmetry (LDF) and reported as cutaneous vascular conductance (CVC; LDF/mean arterial pressure). SR was measured by capacitance hygrometry. LDF and SR were measured at the sole, palm, forearm, and ventral leg during separate bouts of isometric handgrip (IHG) and isometric leg extension (ILE). CVC and its standard deviation decreased significantly during IHG and ILE in the palm and sole (P < 0.05) but not in the forearm or leg (P > 0.05). Only palmar SR increased significantly during IHG and ILE (P < 0.05). We conclude that the major reflex influences of isometric exercise on the skin include AVAs and palmar sweat glands and that this is true for both arm and leg exercise. 相似文献
126.
C R Jacobs B R Davis C J Rieger J J Francis M Saad D P Fyhrie 《Journal of biomechanics》1999,32(11):1159-1164
The apparent properties of cancellous bone are determined by a combination of both hard tissue properties and microstructural organization. A method is desired to extract the underlying hard tissue properties from simple mechanical tests, free from the complications of microstructure. It has been suggested that microCT voxel-based large-scale finite element models could be employed to accomplish this goal (van Rietbergen et al., 1995, Journal of Biomechanics, 28, 69-81). This approach has recently been implemented and it is becoming increasingly popular as finite element models increase in size and sophistication (Fyhrie et al., 1997, Proceedings of the 43rd Annual Meeting of the Orthopaedic Research Society, San Francisco, CA, p. 815; van Rietbergen et al., 1997, Proceedings of the 43rd Annual Meeting of the Orthopaedic Research Society, San Francisco, CA, p. 62). However, no direct quantitative measurements of the accuracy of this method applied to porous structures such as cancellous bone have been made. This project demonstrates the feasibility of this approach by quantifying its best-case accuracy in determining the trabecular hard tissue modulus of analogues fabricated of a material with known material properties determined independently by direct testing. In addition we were able to assess the impact of mesh size and boundary conditions on accuracy. We found that the assumption of a frictionless boundary condition in the parallel plate compression loading configuration was a significant source of error that could be overcome with the use of rigid end-caps similar to those used by Keaveny et al. (1997 Journal of Orthopaedic Research, 15(1), 101-110). In conclusion, we found that this approach is an effective method for determining the average trabecular hard tissue properties of human cancellous bone with an expected practical accuracy level better than 5%. 相似文献
127.
Hesam Addin Akbari Amine Ghram Mohammad Yoosefi Ross Arena Carl J Lavie Hamdi Chtourou Helmi Ben Saad Karim Chamari 《Biology of sport / Institute of Sport》2021,38(4):729
Intermittent fasting (IF) has recently gained popularity, and has been used for centuries in many religious practices. The Ramadan fasting is a mandatory form of IF practiced by millions of healthy adult Muslims globally for a whole lunar month every year. In Islam, the “Sunna” also encourages Muslims to practice IF all along the year (e.g.; two days a week). The 2019-Coronavirus disease (COVID-19) pandemic in the context of Ramadan has raised the question whether fasting is safe practice during the COVID-19 pandemic health crisis, and what would be the healthy lifestyle behaviors while fasting that would minimize the risk of infection. As COVID-19 lacks a specific therapy, IF and physical activity could help promote human immunity and be part of holistic preventive strategy against COVID-19. In this commentary, the authors focus on this dilemma and provide recommendations to the fasting communities for safely practicing physical activity in time of COVID-19 pandemic. 相似文献
128.
Mohamed T. El-Saadony Ahmed M. Saad Taha F. Taha Azhar A. Najjar Nidal M. Zabermawi Maha M. Nader Synan F. AbuQamar Khaled A. El-Tarabily Ali Salama 《Saudi Journal of Biological Sciences》2021,28(12):6782-6794
The current study was performed to develop a simple, safe, and cost-effective technique for the biosynthesis of selenium nanoparticles (SeNPs) from lactic acid bacteria (LAB) isolated from human breast milk with antifungal activity against animal pathogenic fungi. The LAB was selected based on their speed of transforming sodium selenite (Na2SeO3) to SeNPs. Out of the four identified LAB isolates, only one strain produced dark red color within 32 h of incubation, indicating that this isolate was the fastest in transforming Na2SeO3 to SeNPs; and was chosen for the biosynthesis of LAB-SeNPs. The superior isolate was further identified as Lactobacillus paracasei HM1 (MW390875) based on matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and phylogenetic tree analysis of 16S rRNA sequence alignments. The optimum experimental conditions for the biosynthesis of SeNPs by L. paracasei HM1 were found to be pH (6.0), temperature (35˚C), Na2SeO3 (4.0 mM), reaction time (32 h), and agitation speed (160 rpm). The ultraviolet absorbance of L. paracasei-SeNPs was detected at 300 nm, and the transmission electron microscopy (TEM) captured a diameter range between 3.0 and 50.0 nm. The energy-dispersive X-ray spectroscopy (EDX) and the Fourier-transform infrared spectroscopy (FTIR) provided a clear image of the active groups associated with the stability of L. paracasei-SeNPs. The size of L. paracasei-SeNPs using dynamic light scattering technique was 56.91 ± 1.8 nm, and zeta potential value was −20.1 ± 0.6 mV in one peak. The data also revealed that L. paracasei-SeNPs effectively inhibited the growth of Candida and Fusarium species, and this was further confirmed by scanning electron microscopy (SEM). The current study concluded that the SeNPs obtained from L. paracasei HM1 could be used to prepare biological antifungal formulations effective against major animal pathogenic fungi. The antifungal activity of the biologically synthesized SeNPs using L. paracasei HM1 outperforms the chemically produced SeNPs. In vivo studies showing the antagonistic effect of SeNPs on pathogenic fungi are underway to demonstrate the potential of a therapeutic agent to treat animals against major infectious fungal diseases. 相似文献
129.
Chemical Diversity and Antimicrobial Activity of Volatile Compounds from Zanthoxylum zanthoxyloides Lam. according to Compound Classes,Plant Organs and Senegalese Sample Locations
下载免费PDF全文
![点击此处可从《化学与生物多样性》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yoro Tine Abdoulaye Diop William Diatta Jean‐Marie Desjobert Cheikh Saad Bouh Boye Jean Costa Alassane Wélé Julien Paolini 《化学与生物多样性》2017,14(1)
The chemical diversity of Zanthoxylum zanthoxyloides growing wild in Senegal was studied according to volatile compound classes, plant organs and sample locations. The composition of fruit essential oil was investigated using an original targeted approach based on the combination of gas chromatography (GC) and liquid chromatography (LC) both coupled with mass spectrometry (MS). The volatile composition of Z. zanthoxyloides fruits exhibited relative high amounts of hydrocarbon monoterpenes (24.3 – 55.8%) and non‐terpenic oxygenated compounds (34.5 – 63.1%). The main components were (E)‐β‐ocimene (12.1 – 39%), octyl acetate (11.6 – 21.8%) and decanol (9.7 – 15.4%). The GC and GC/MS profiling of fruit essential oils showed a chemical variability according to geographical locations of plant material. The LC/MS/MS analysis of fruit oils allowed the detection of seven coumarins in trace content. The chemical composition of fruit essential oils was compared with volatile fractions of leaves and barks (root and trunk) from the same plant station. Hexadecanoic acid, germacrene D and decanal were identified as the major constituents of leaves whereas the barks (root and trunk) were dominated by pellitorine (85.8% and 57%, respectively), an atypic linear compound with amide group. The fruit essential oil exhibited interesting antimicrobial activities against Staphylococcus aureus and Candida albicans, particularly the alcohol fraction of the oil. 相似文献
130.