全文获取类型
收费全文 | 9787篇 |
免费 | 562篇 |
国内免费 | 28篇 |
专业分类
10377篇 |
出版年
2024年 | 14篇 |
2023年 | 140篇 |
2022年 | 352篇 |
2021年 | 491篇 |
2020年 | 411篇 |
2019年 | 578篇 |
2018年 | 482篇 |
2017年 | 333篇 |
2016年 | 462篇 |
2015年 | 524篇 |
2014年 | 626篇 |
2013年 | 836篇 |
2012年 | 751篇 |
2011年 | 772篇 |
2010年 | 399篇 |
2009年 | 365篇 |
2008年 | 387篇 |
2007年 | 413篇 |
2006年 | 351篇 |
2005年 | 299篇 |
2004年 | 246篇 |
2003年 | 191篇 |
2002年 | 185篇 |
2001年 | 64篇 |
2000年 | 44篇 |
1999年 | 57篇 |
1998年 | 43篇 |
1997年 | 39篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 23篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 30篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1974年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Najafzadeh Mohammad Javad Dolatabadi Somayeh de Hoog Sybren Esfahani Mahmoud Karimizadeh Haghani Iman Aghili Seyed Reza Ghazvini Roshanak Daei Rezaei-Matehkolaei Ali Abastabar Mahdi Al-Hatmi Abdullah M. S. 《Mycopathologia》2020,185(3):515-525
Mycopathologia - Fungi of the genus Fusarium are well known as major plant pathogens but also cause a broad spectrum of human infections. Sixty-three clinical isolates, collected during... 相似文献
62.
Alireza Sharif Hamed Haddad Kashani Elahe Nasri Zahra Soleimani Mohammad Reza Sharif 《Probiotics and antimicrobial proteins》2017,9(4):380-385
Diarrhea is considered as an important cause of morbidity and mortality, even though one of the main reasons of death following diarrhea is initiated by dysentery. In recent years, the consumption of probiotics has been proposed for the treatment of infectious diarrhea. Despite most of the studies on probiotics have focused on acute watery diarrhea, few studies in the field of dysentery have found beneficial effects of probiotics. This study is a randomized double-blind clinical trial. The patients were randomly placed into control and case groups. In the intervention group, the patients received probiotics in the form of Kidilact® sachet, which contained high amounts of 7-strain friendly bacteria strains of Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus, Bifidobacterium infantis, Bifidobacterium breve, and Streptococcus thermophiles. On the other hand, the patients in the control group received placebo sachets on a daily basis for 5 days. It is notable that the treatment protocol of acute dysentery was done on both groups. The results of this study showed significant differences in the duration of blood in diarrhea between probiotic consumers (2.62 days) and the control group (3.16 days) (P value = 0.05). Additionally, significant differences in the average length of hospitalization in probiotic consumers (3.16 days) and control (3.66 days), (P value = 0.02) could be claimed that the consumption of probiotics is effective in reducing the duration of dysentery and diarrhea. The results of this study suggest that the use of probiotics can be effective in reducing the duration of blood in diarrhea. This study was also recorded in the Iran center of clinical trials registration database (IRCT2014060617985N1). 相似文献
63.
Somayeh Ghasemi Amir H. Khoshgoftarmanesh Hassan Hadadzadeh Mehran Jafari 《Journal of Plant Growth Regulation》2012,31(4):498-508
Supplying a sufficient amount of available iron (Fe) for plant growth in hydroponic nutrient solutions is a great challenge. The chelators commonly used to supply Fe in nutrient solutions have several disadvantages and may negatively affect plant growth. In this research study we have synthesized certain Fe-amino acid chelates, including Fe-arginine [Fe(Arg)2], Fe-glycine [Fe(Gly)2], and Fe-histidine [Fe(His)2], and evaluated their efficacy as an Fe source for two tomato cultivars (Lycopersicon esculentum Mill. cvs. ‘Rani’ and ‘Sarika’) grown in nutrient solution. Application of Fe-amino acid chelates significantly increased root and shoot dry matter yield of both tomato cultivars compared with Fe-EDTA. Tomato plants supplied with Fe-amino acid chelates also accumulated significantly higher levels of Fe, Zn, and N in their roots and shoots compared with those supplied with Fe-EDTA. In ‘Sarika’, the effect of Fe-amino acid chelates on shoot Fe content was in the order Fe(His)2?>?Fe(Gly)2?>?Fe(Arg)2. In ‘Rani’, the addition of all synthesized Fe-amino acid chelates significantly increased activity of ascorbate peroxidase (APX) in comparison with Fe-EDTA, whereas in ‘Sarika’, only Fe(His)2 increased shoot APX activity. The results obtained indicated that using Fe-amino acid chelates in the nutrient solution could supply a sufficient amount of Fe for plant uptake and also improve root and shoot growth of tomato plants, although this increase was cultivar-dependent. According to the results, Fe-amino acid chelates can be used as an alternative for Fe-EDTA to supply Fe in nutrient solutions. 相似文献
64.
65.
66.
Ali Bagheri Seher Karaman Erkul Ali Asghar Maassoumi Mohammad Reza Rahiminejad Frank R. Blattner 《Nordic Journal of Botany》2015,33(5):532-539
As the result of surveying the relevant type specimens, together with macro‐ and micro‐morphological studies, chromosome counting and ITS sequencing, Astragalus trifoliastrum was found to be a species independent of A. laguriformis (with which it has peviously been synonymized). In contrast, A. wanensis, assumed to be a synonym of A. trifoliastrum, indeed appears to be identical with A. trifoliastrum. The diploid chromosome number of 2n = 16 is reported for the first time for A. trifoliastrum. 相似文献
67.
Mohsen Akbari Mohammad Hassan Fazaelipoor Ataollah Soltai Goharizi 《Biotechnology and Bioprocess Engineering》2011,16(2):407-412
Water super absorbents are low cross-linked hydrophilic polymers that absorb water in amounts up to several hundred times
their dry weight. In this study, the effect of adding these materials to the bed of a biofilter was investigated. Two equal
size biofilters were used for this purpose. One of the biofilters was packed with a mixture of perlite and a commercial polyacrylamide
based super absorbent (2.3% dry weight), and the other was packed with perlite to perform as a control. The biofilters were
inoculated with a bacterial culture that was able to grow on n-hexane as the sole source of carbon and energy. Both biofilters
removed up to 90% of the entering pollutants when using an inlet n-hexane concentration of 1 g/m3, and an air flow rate of 0.3 L/min (mass loading of 18.34 g/m3/h, and empty bed residence time of 3.27 min). The super absorbent had a positive effect on the performance of the biofilter.
While the difference in the performance of the biofilters was marginal when frequent moistening was applied, the difference
was considerable when moistening was less frequent. 相似文献
68.
Christian Hansen Nils Hüttebr?uker Wilko Wilkening Mohammad Ashfaq Helmut Ermert 《Biomedizinische Technik》2007,52(4):274-283
In clinical diagnostics, ultrasonographic contrast-agent imaging gives access to medical parameters such as perfusion and vascularization. In addition to the artifacts that are typical for ultrasonic imaging, e.g., speckle noise and depth-dependent sensitivity and resolution, contrast-agent imaging shows more pronounced depth dependence and may suffer from shadowing artifacts that arise from high attenuation of the ultrasound waves by the contrast agent at high concentrations. By imaging an object from different viewing angles in one 2D image plane and summing the images obtained (spatial compounding), image quality can be increased and artifacts can be suppressed. In the present study, we combined both techniques to overcome the limitations of contrast-agent imaging. We used a commercially available ultrasound scanner and a custom-made high-precision mechanical system to rotate the ultrasound transducer fully around the object under investigation. Using this set-up, ultrasound data were acquired in reflection mode to generate a 360 degrees compound scan of a flow-mimicking phantom supplied with contrast agent. 相似文献
69.
Feizabadi MM Aliahmadi A Mobasheri F Asgharzadeh A Asadi S Etemadi G 《Canadian journal of microbiology》2003,49(10):645-649
Conventional bacteriology techniques were used to identify enterococci isolates cultured from patients at different hospitals in Tehran during 2000-2001. The identification was confirmed using species-specific PCR targeting the D-alanyl-D-alanine ligase gene. A total of 59 isolates of Enterococcus faecalis were identified. The rates of resistance to different antibiotics were in the following order: penicillin 84%, ciprofloxacin 42%, high-level gentamicin 30%, nitrofurantoin 14%, imipenem 4%, and chloramphenicol 2%. Resistance to ampicillin was found to be rare among the Iranian isolates of E. faecalis. Multi-locus enzyme electrophoresis was then used to analyze the strains. Forty-five electrophoretic types were obtained when 10 enzyme loci were screened. Although the collection of bacterial isolates was limited in time and location, considerable heterogeneity was found. Analysis of strains for linkage disequilibrium demonstrated that the studied population is not clonal, since the index of association was not significantly different from zero (Ia = 0.0296). Enterococcus faecalis isolates recovered from patients in Tehran were genetically diverse and seemed to possess a high potential for genetic recombinations, though none were resistant to vancomycin. 相似文献
70.
Conclusion PEG-400, polysorbate 80, and 2 CDs (Trappsol HPB and Captisol) were used in an attempt to improve the aqueous solubility of
a model hydrophobic drug, progesterone. The aqueous solubility of progesterone improved significantly from 0.007 mg/mL by
the addition of PEG-400, CDs, and polysorbate 80. In systems containing various amounts of PEG-400 and 3% Trappsol HPB in
water (% wt/wt), the theoretical solubility was calculated by adding the solubilities in the individual systems. The observed
solubility values were up to 96% higher than the theoretical values. The effect of synergism was significant in 5% to 50%
PEG-400/water systems containing Trappsol HPB. Systems containing Captisol did not show such synergistic effects. In general,
the addition of polysorbate 80 to the PEG-400/water systems containing CDs affected synergism negatively. 相似文献