全文获取类型
收费全文 | 7458篇 |
免费 | 440篇 |
国内免费 | 21篇 |
专业分类
7919篇 |
出版年
2024年 | 11篇 |
2023年 | 97篇 |
2022年 | 265篇 |
2021年 | 377篇 |
2020年 | 346篇 |
2019年 | 495篇 |
2018年 | 391篇 |
2017年 | 280篇 |
2016年 | 373篇 |
2015年 | 403篇 |
2014年 | 494篇 |
2013年 | 632篇 |
2012年 | 588篇 |
2011年 | 599篇 |
2010年 | 316篇 |
2009年 | 266篇 |
2008年 | 316篇 |
2007年 | 302篇 |
2006年 | 266篇 |
2005年 | 221篇 |
2004年 | 169篇 |
2003年 | 117篇 |
2002年 | 106篇 |
2001年 | 37篇 |
2000年 | 27篇 |
1999年 | 36篇 |
1998年 | 23篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 24篇 |
1992年 | 13篇 |
1991年 | 35篇 |
1990年 | 15篇 |
1989年 | 23篇 |
1988年 | 9篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1978年 | 7篇 |
1976年 | 7篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有7919条查询结果,搜索用时 15 毫秒
51.
52.
Uday Veer Singh Amar Abhishek Monika Bhaskar Neeraj Tandan Nasreen Ghazi Ansari Netra Pal Singh 《Bioinformation》2015,11(3):138-144
In this study, distribution of metal accumulation and their biological changes of Indian mustard plants (Brassica nigra L.) grown in
soil irrigated with different concentration of rayon grade paper effluent (RGPE, 25%, 50%, 75%, 100%, v/v) were studied. A
pronounced effect was recorded at 50% (v/v) RGPE on germination of seeds, amylase activity and other growth parameters in
Indian mustard plants. An increase in the chlorophyll and protein contents was also recorded at <50% (v/v) RGPE followed by a
decrease at higher concentrations of RGPE (>75%). A significant increase lipid peroxidation was recorded, which was evidenced by
the increased malondialdehyde (MDA) content in shoot, leaves and seeds in tested plant at all the concentrations of RGPE. This
Indian mustard plants (Brassica nigra L.) are well adapted for tolerance of significant amount of heavy metals due to increased level
of antioxidants (cysteine and ascorbic acid) in root shoot and leaves of treated plants at all concentration of RGPE. Moreover, it is
also important that RGPE should be treated to bring down the metal concentration well within the prescribed limit prior to use in
agricultural soil for ferti-irrigation. 相似文献
53.
54.
Megan C. McDonald Mohammad Razavi Timothy L. Friesen Patrick C. Brunner Bruce A. McDonald 《Fungal genetics and biology : FG & B》2012,49(11):882-895
The origin of the fungal wheat pathogen Phaeosphaeria nodorum remains unclear despite earlier intensive global population genetic and phylogeographical studies. We sequenced 1683 bp distributed across three loci in 355 globally distributed Phaeosphaeria isolates, including 74 collected in Iran near the center of origin of wheat. We identified nine phylogenetically distinct clades, including two previously unknown species tentatively named P1 and P2 collected in Iran. Coalescent analysis indicates that P1 and P2 are sister species of P. nodorum and the other Phaeosphaeria species identified in our analysis. Two species, P. nodorum and P. avenaria f. sp. tritici 1 (Pat1), comprised ~85% of the sampled isolates, making them the dominant wheat-infecting pathogens within the species complex. We designed a PCR-RFLP assay to distinguish P. nodorum from Pat1. Approximately 4% of P. nodorum and Pat1 isolates showed evidence of hybridization. Measures of private allelic richness at SSR and sequence loci suggest that the center of origin of P. nodorum coincides with its host in the Fertile Crescent. We hypothesize that the origin of this species complex is also in the Fertile Crescent, with four species out of nine found exclusively in the Iranian collections. 相似文献
55.
Jabir Thajudeen Jesmi Yousuf Vipindas Puthiya Veetil Sherin Varghese Arvind Singh Mohamed Hatha Abdulla 《World journal of microbiology & biotechnology》2017,33(2):41
Microorganisms play a significant role in biogeochemical cycles, especially in the benthic and pelagic ecosystems. Role of environmental parameters in regulating the diversity, distribution and physiology of these microorganisms in tropical marine environment is not well understood. In this study, we have identified dinitrogen (N2) fixing bacterial communities in the sediments by constructing clone libraries of nitrogenase (nifH) gene from four different stations in the Cochin estuary, along the southeastern Arabian Sea. N2 fixing bacterial clones revealed that over 20 putative diazotrophs belong to alpha-, beta-, gamma-, delta- and epsilon- proteobacteria and firmicutes. Predominant genera among these were Bradyrhizobium sp. (α-proteobacteria), Dechloromonas sp. (β-proteobacteria); Azotobactor sp., Teredinibacter sp., Methylobacter sp., Rheinheimera sp. and Marinobacterium sp. (γ-proteobacteria); Desulfobacter sp., Desulfobulbus sp. and Desulfovibrio sp. (δ -proteobacteria); Arcobacter sp. and Sulfurospirillum sp. (ε-proteobacteria). Nostoc sp. was solely identified among the cyanobacterial phylotype. Nitrogen fixing Sulfate reducing bacteria (SRBs) such as Desulfobulbus sp., Desulfovibrio sp., Desulfuromonas sp., Desulfosporosinus sp., Desulfobacter sp., were also observed in the study. Most of the bacterial nifH sequences revealed that the identities of N2 fixing bacteria were less than 95% similar to that available in the GenBank database, which suggested that the sequences were of novel N2 fixing microorganisms. Shannon-Weiner diversity index of nifH gene ranged from 2.95 to 3.61, indicating an inflated diversity of N2 fixing bacteria. Canonical correspondence analysis (CCA) implied positive correlation among nifH diversity, N2 fixation rate and other environmental variables. 相似文献
56.
A field experiment was conducted to determine the seasonal patterns of arbuscular mycorrhiza (AM) in a dryland winter wheat
(Triticum aestivum L.) system and to determine wheat growth and P uptake responses to inoculation with mycorrhizal fungus. Broadcast-incorporated
treatments included (1) no inoculation with mycorrhizal fungus, with and without P fertilizer, and (2) mycorrhizal fungal
inoculation at a rate of 5000 spores of Glomus intraradices (Schenck and Smith), per 30 cm in each row, with and without fertilizer P. Winter wheat was seeded within a day after treatments
were imposed, and roots were sampled at five growth stages to quantify AM. Shoot samples were also taken for determination
of dry matter, grain yield and yield components, and N and P uptake. No AM infection was evident during the fall months following
seeding, which was characterized by low soil temperature, while during the spring, the AM increased gradually. Increases in
wheat grain yields by enhanced AM were of similar magnitude to the response obtained from P fertilization. However, responses
differed at intermediate growth stages. At the tillering stage, P uptake was mainly increased by P fertilization but not by
fungal inoculation. At harvest, enhanced AM increased P uptake regardless of whether or not fertilizer P was added. The AM
symbiosis increased with rising soil temperatures in the spring, in time to enhance late-season P accumulation and grain production.
Accepted: 15 July 1998 相似文献
57.
58.
Naderi Gharehgheshlagh Soheila Fatemi Mohammad Javad Jamili Shahla Nourani Mohammad Reza Sharifi Ali Mohammad Saberi Mohsen Amini Naser Ganji Fatemeh 《International journal of peptide research and therapeutics》2021,27(1):317-328
International Journal of Peptide Research and Therapeutics - Natural compounds extracted from marine organisms consisting of biological active materials like collagen provide a major source of... 相似文献
59.
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
60.
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