全文获取类型
收费全文 | 2069篇 |
免费 | 132篇 |
国内免费 | 6篇 |
专业分类
2207篇 |
出版年
2023年 | 34篇 |
2022年 | 77篇 |
2021年 | 97篇 |
2020年 | 77篇 |
2019年 | 106篇 |
2018年 | 88篇 |
2017年 | 78篇 |
2016年 | 88篇 |
2015年 | 103篇 |
2014年 | 114篇 |
2013年 | 177篇 |
2012年 | 132篇 |
2011年 | 152篇 |
2010年 | 98篇 |
2009年 | 86篇 |
2008年 | 74篇 |
2007年 | 73篇 |
2006年 | 57篇 |
2005年 | 50篇 |
2004年 | 51篇 |
2003年 | 40篇 |
2002年 | 36篇 |
2001年 | 7篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 6篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有2207条查询结果,搜索用时 15 毫秒
81.
Almasirad A Tabatabai SA Faizi M Kebriaeezadeh A Mehrabi N Dalvandi A Shafiee A 《Bioorganic & medicinal chemistry letters》2004,14(24):191-6059
A series of new 2-substituted-5-[2-(2-fluorophenoxy)phenyl]-1,3,4-oxadiazoles has been synthesized and screened for their anticonvulsant activities. Compound 3 shows considerable anticonvulsant activity both in PTZ and MES models. It seems that this effect is mediated by benzodiazepine receptors and other unknown mechanism, respectively. 相似文献
82.
Sayed WF 《Acta microbiologica et immunologica Hungarica》2011,58(2):93-103
Spores of four Frankia strains, the nitrogen-fixing actinomycete, were exposed to short wavelength UV-C radiation of 254 nm at 1 lux cm(2) (0.24 mw cm2 of energy) for 10 min. The used strains were HFP020203, UGL020604, UGL020602q and ORS021001. Exposure to UV was followed by reactivation with visible white light at 327.4 lux cm(2) for the same period of time. Spore germination percentage, spore protein content, and cell growth were damaged by this treatment. The lower and higher percentages of reduction in spore germination were 32 and 63% and, for the same strains, the recovery by white light was 7.2 and 37%. The lower percentages of UV damage and subsequent low recovery were recorded for strain ORS021001 that is considered more resistant to UV than the other strains. The higher percentages were recorded for strain HFP020203 that is more sensitive to UV but having more efficient repairing mechanisms. All the tested strains showed repairing activity induced by white light as indicated from the increase in their spore germination, protein content and almost restoring the normal shape of Frankia hyphae, after being damaged, as revealed by scanning electron microscope. This is the first evidence that photo-repairing systems are present in Frankia strains although there are variations in their response to both UV-C and photoreactivation by white light. 相似文献
83.
Alessio Cimmino Anna Andolfi Fabiana Avolio Abbas Ali Nurhayat Tabanca Ikhlas A. Khan Antonio Evidente 《化学与生物多样性》2013,10(12):2302-2302
84.
Sameni S Ghayumi MA Mortazavi G Faghih Z Kashef MA Ghaderi A 《Molecular biology reports》2009,36(5):1001-1005
Lung cancer is one of the leading causes of death from cancer. Both immune cells and tumor cells play a key role in lung cancer
immunity by secretion of cytokines and developing type-2 cell-mediated immune response. IL-13 is an immunoregulatory cytokine
affecting tumor immunosurveillance by deviation of immune response from Th1 to Th2. In the present study we sought to determine
the association of single nucleotide polymorphisms (SNPs) of IL-13 gene at positions +2044 (G/A) and −1055 (C/T) and lung cancer. One hundred forty one patients and 113 controls were recruited;
control group was subdivided into smoker and nonsmoker individuals for serum detection. Genotyping was carried out by PCR-RFLP
assay and IL-13 detection by ELISA method. No statistically significant difference was found in the frequency of genotypes,
alleles, and haplotypes at positions +2044 (G/A) and −1055 (C/T) of IL-13 gene between lung cancer patients and controls. Serum level of IL-13 was not detectable in both groups. The results of this
study reveal that although +2044 (G/A) and −1055 (C/T) SNPs in IL-13 are implicated in some pulmonary processes, they do not confer susceptibility to lung cancer in Iranian population. 相似文献
85.
86.
Alamtaj Samsami Dehaghani Khatere Shahriary Mohammad Amin Kashef Sirous Naeimi Mohammad Javad Fattahi Zahra Mojtahedi Abbas Ghaderi 《Molecular biology reports》2009,36(8):2393-2397
IL-18, initially defined as a potent inducer of IFN- γ production, is a systemic, multifunctional cytokine with both pro-cancerous
and anti-cancer activities. The contribution of the IL-18 promoter polymorphisms at positions −607 (C/A) and −137 (G/C) to
cancer development has been reported. We sought to examine IL-18 serum level and its polymorphisms in Iranian women with ovarian
cancer. Single nucleotide polymorphisms (SNPs) at positions −607 (C/A) and −137 (G/C) were analyzed by allele-specific polymerase
chain reaction in 85 women with ovarian cancer and 158 healthy controls. IL-18 serum level was determined using ELISA method.
No significant association was found between the allele, genotype, and haplotype distributions of the SNPs and ovarian cancer.
Mean IL-18 serum level was significantly higher in patients than in controls (P = 0.008). Comparing IL-18 serum levels with genotypes at positions −607 and −137 revealed no significant difference. No association
was also found between IL-18 levels and the disease stage. In conclusion, our results indicate that IL-18 promoter polymorphisms
at positions −607 (C/A) and −137 (G/C) appear not to confer susceptibility to ovarian cancer in Iranian population; however,
IL-18 serum level increases in ovarian cancer patients. 相似文献
87.
Zohaib Abbas Fariha Arooj Ihsan Elahi Zaheer Muhammad Rizwan Muhammad Ahsan Riaz 《International journal of phytoremediation》2019,21(13):1356-1367
AbstractIn the present study, the effectiveness of water hyacinth and water lettuce was tested for the phytoremediation of landfill leachate for the period of 15?days. Fifteen plastic containers were used in experimental setup where aquatic plants were fitted as a floating bed with the help of thermo-pole sheet. It was observed that both plants significantly (p?<?0.05/p?<?0.01/p?<?0.001) reduce the physicochemical parameters pH, TDS, BOD, COD and heavy metals like Zn, Pb, Fe, Cu and Ni from landfill leachate. Maximum reduction in these parameters was obtained at 50% and 75% landfill leachate treatment and their removal rate gradually increased from day 3 to day 15 of the experiment. The maximum removal rate for heavy metals such as for Zn (80–90%), Fe (83–87%) and Pb (76–84%) was attained by Eichhornia crassipes and Pistia stratiotes. Value of bioconcentration and translocation factor was less than 1 which indicates the low transport of heavy metals from roots to the above-ground parts of the plants. Both these plants accumulate heavy metals inside their body without showing much reduction in growth and showing tolerance to all the present metals. Therefore, results obtained from the study suggest that these aquatic plants are suitable candidate for the removal of pollution load from landfill leachate. 相似文献
88.
Addition of either abscisic acid (ABA) or kinetin at 10−6 M to salinized media (20–120mM NaCl) induced remarkable effects on growth ofPhaseolus vulgaris plants. Whereas ABA inhibited the plant growth and the rate of transpiration, kinetin induced stimulation of both parameters.
Moreover, ABA increased proline and phosphorus concentrations in the salinized plants whilst kinetin decreased them.
ABA induced stimulation of the transport of K, Ca and Cl from root to shoot, accumulation of K, Na and Cl in root cells and
inhibits the transport of Na and accumulation of Ca. Kinetin appeared to inhibit the transport and accumulation of Na and
Cl, transport of K, and stimulates the accumulation of K and Ca as well as the transport of Ca. The highest influence of both
ABA and kinetin was mostly observed when these hormones were used in combination with the highest concentration of NaCl (120
mM) in the medium. 相似文献
89.
Liang Chengcheng Raza Sayed Haidar Abbas Naqvi Muhammad Abuzar Raza Feng Yanrong Khan Rajwali Mohammedsaleh Zuhair M. Shater Abdullah F. Al-ahmadi Bassam M. Saleh Fayez M. Bilal Muhammad Ahsan Zan Linsen 《Biochemical genetics》2022,60(2):543-557
Biochemical Genetics - The Long non-coding RNA (lncRNA) expression profile data of ten samples including human Mesenchymal Stem Cell (MSC) adipogenic differentiation 0, 3, and 6 days from... 相似文献
90.
Farshad Shadanloo Mohammad Hasan Najafi Sayed Morteza Hosseini Mehdi Hajian Mohsen Forouzanfar Kamran Ghaedi Parvaneh Abedi Somaye Ostadhosseini Laleh Hosseini Morad‐Pasha Eskandari‐Nasab Mohammad Hossein Nasr Esfahani 《Molecular reproduction and development》2010,77(10):868-875
In relation to the growing recent interest in the establishment of sperm‐mediated gene transfer (SMGT) technology as a convenient and effective method for the simple production of transgenic animals, in this study the possibility of using SMGT to produce transgenic caprine embryos was investigated for the first time. Buck sperm were directly incubated with different concentrations (0–500 ng) of pcDNA/his/Lac‐Z plasmid and used for IVF or ICSI. Sperm used for ICSI were categorized into motile or live‐immotile group before being injected into oocytes. In a separate experiment, dead sperm prepared by repeated freezing/thawing were used for DNA‐incubation before ICSI. Sham injection was carried out by intracytoplasmic injection of approximately the same volume of media containing different doses of DNA using an ICSI needle. Transgene expression and transmission were detected by X‐Gal staining and PCR analysis of developed embryos, respectively. A reasonable blastocyst rate was observed in all the groups. Only embryos in the sham group were negative for transgene transmission. Transgene expression was completely dependent on the delivery technique and status of sperm, and was only observed in the live‐immotile and dead ICSI groups. The results of this study showed that the technique (IVF vs. ICSI vs. sham injection), sperm status (motile vs. live‐immotile vs. dead) and to some extent DNA concentration affect embryo development, transgene transmission and expression. Mol. Reprod. Dev. 77:868–875, 2010. © 2010 Wiley‐Liss, Inc. 相似文献