全文获取类型
收费全文 | 1185篇 |
免费 | 56篇 |
国内免费 | 3篇 |
出版年
2022年 | 21篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 27篇 |
2018年 | 32篇 |
2017年 | 35篇 |
2016年 | 38篇 |
2015年 | 46篇 |
2014年 | 64篇 |
2013年 | 84篇 |
2012年 | 87篇 |
2011年 | 65篇 |
2010年 | 53篇 |
2009年 | 34篇 |
2008年 | 49篇 |
2007年 | 44篇 |
2006年 | 54篇 |
2005年 | 41篇 |
2004年 | 17篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 24篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 11篇 |
排序方式: 共有1244条查询结果,搜索用时 15 毫秒
81.
82.
83.
Riyaz Mohamed K. K. Dharmappa Shaista Tarannum N. M. Jameel S. A. Kannum H. S. Ashrafulla Lokanath Rai Cletus JMD’ Souza M. A. Shekhar Bannikuppe S. Vishwanath 《Molecular and cellular biochemistry》2010,338(1-2):69-76
This investigation aims to evaluate the antitumor and antioxidant potential of Chrysaora quinquecirrha (sea nettle) nematocyst venom on Ehrlich ascites carcinoma (EAC) tumor model. Tumor was induced in mice by intraperitoneal injection of EAC cells. The antitumor effect of sea nettle nematocyst venom (SNV) peptide was evaluated by assessing in vitro cytotoxicity, survival time, hematological, and antioxidant parameters. Intraperitoneal injection of SNV peptide increased the survival time of the EAC-bearing mice. The SNV peptide brought back the altered levels of the hematological and antioxidant parameters in a dose dependent manner in EAC-bearing mice. The results were comparable to that of the result obtained from the animals treated with the standard drug 5-fluorouracil (20 mg/kg bw). Thus, present study revealed that SNV peptide possessed significant antitumor and antioxidant activity. 相似文献
84.
Population dynamics of five different species of grasshopper were analyzed for the first time in Darjeeling (Lebong and Happy Valley) of the eastern Himalayan region of India. The study is based on the relationship between monthly samples collected using sweep nets for three years (March, 2005 to February, 2008) in relation to meteorological parameters (monthly average rainfall, monthly mean maximum and minimum temperatures). The population for each of the five species of grasshopper is plotted against the Aridity Ratio (A.R.). For all species, the population increases at lower A.R. values and then decreases exponentially at higher A.R. values. The exponentially decreasing part of the population is modeled using a simple formula. The monthly population of A. crenulata nymphs and adults in Lebong has also been modeled by iterative equations using A.R. and results compared satisfactorily with the sample data. These works show the possibility of forecasting grasshopper populations using a simple model and thereby easing the regulation process. 相似文献
85.
Ashis K. Mukherjee Tadi Satish Kumar Sudhir K. Rai Jetendra K. Roy 《Biotechnology and Bioprocess Engineering》2010,15(6):984-992
We report the statistical optimization of the immobilization of alkaline α-amylase [E.C. 3.2.1.1] from Bacillus alcalophilus onto nano-sized supermagnetic ironoxide nanoparticles (MNPs) for augmenting the cost effective industrial application of
MNP-bound α-amylase. Both Plackett-Burman factorial design and response surface methodology (RSM) were employed to screen
the influence of different parameters and the central effect of response on the α-amylase-iron oxide MNP binding process.
The high coefficient of determination (R2) and analysis of variance (ANOVA) of the quadratic model indicated the competence
of the proposed model. The size of the MNPs was confirmed by X-ray diffraction and scanning electron microscope analyses in
which Fourier transform infrared spectroscopy suggested immobilization of the enzyme on iron-oxide MNPs. A significant improvement
(∼ 26-fold) in specific activity, thermal and storage stability, and reusability of α-amylase after binding with iron-oxide
MNP reinforced the improved biotechnological potential of the α-amylase iron-oxide MNP bioconjugate compared to free α-amylase.
These results open new avenues for applying this MNP immobilized enzyme in different industrial sectors, notably in the paper
and brewing industries. 相似文献
86.
Guava (Psidium guajava L.), an important fruit crop of several tropical and sub-tropical countries, is facing several agronomic and horticultural
problems such as susceptibility to many pathogens, particularly guava wilting caused by Fusarium oxysporium psidii, low fruit growth, short shelf life of fruits, high seed content, and stress sensitivity. Conventional breeding techniques
have limited scope in improvement of guava owing to long juvenile period, self incompatibility, and heterozygous nature. Conventional
propagation methods, i.e., cutting, grafting or stool layering, for improvement of guava already exist, but the long juvenile
period has made them time consuming and cumbersome. Several biotechnological approaches such as genetic transformation may
be effective practical solutions for such problems and improvement of guava. The improvement of fruit trees through genetic
transformation requires an efficient regeneration system. During the past 2–3 decades, different approaches have been made
for in vitro propagation of guava. An overview on the in vitro regeneration of guava via organogenesis, somatic embryogenesis,
and synthetic seeds is presented. Organogenesis in several different genotypes through various explant selection from mature
tree and seedling plants has been achieved. Factors affecting somatic embryogenesis in guava have been reviewed. Production
of synthetic seeds using embryogenic propagules, i.e., somatic embryos and non-embryogenic vegetative propagules, i.e., shoot
tips and nodal segments have also been achieved. Development of synthetic seed in guava may be applicable for propagation,
short-term storage, and germplasm exchange, and distribution. An initial attempt for genetic transformation has also been
reported. The purpose of this review is to focus upon the current information on in vitro propagation and biotechnological
advances made in guava. 相似文献
87.
Glanders is highly contagious disease of equines, caused by Burkholderia mallei. The disease though rare, can be transmitted to humans. Here, we report a strategy for rapid detection of B. mallei from environmental samples. Different bacteriological media were evaluated and brain heart infusion broth medium with selective
supplements (BHIB-SS) of penicillin (200 U/ml) and crystal violet (1:10,00000) was found to support the maximum growth of
B. mallei even in the presence of other bacteria like Escherichia coli and Staphylococcus aureus. A polymerase chain reaction (PCR) and a DNA hybridization method was standardized for 823 bp specific dNA sequence of B. mallei. To enable the quicker and direct enrichment of B. mallei bacteria from environmental samples, an immunomagnetic separation (IMS) method was also standardized. Water, husk, grass
and gram samples were artificially contaminated by B. mallei bacteria and after enrichment of B. mallei in BHIB-SS, detection was carried out by PCR and DNA hybridization. PCR was found to be a better method of the two with a
detection limit of 104–106 CFU/ml (6 h enrichment in BHIB-SS) in water and other particulate matrices. Detection by PCR in the above samples without
enrichment in BHIBSS was carried out following IMS where the detection limit was about 1–2 log higher than PCR following enrichment
in BHIB-SS. We recommend PCR for 823 bp for detection of B. mallei from environmental samples either following enrichment in BHIB-SS or IMS. IMS-PCR method may be preferred in situations where
numbers of B. mallei bacteria are expected to be high and results are required in short time. 相似文献
88.
Shashi Kant Singh Manoj K. Rai Pooja Asthana L. Sahoo 《Acta Physiologiae Plantarum》2010,32(3):607-610
Nodal segments obtained from in vitro proliferated shoots of Eclipta alba (L.) Hassk, were encapsulated in calcium alginate beads for large-scale clonal propagation, short-term conservation and germplasm
exchange and distribution. The best gel complexation was achieved using 3% sodium alginate and 100 mM CaCl2·2H2O. Maximum percent response (100%) for conversion of encapsulated nodal segments into plantlets was obtained on 0.7% agar-solidified
full-strength MS medium containing 0.88 μM BAP. Encapsulated nodal segments could be stored at low temperature (4°C) up to
60 days with a survival frequency of 51.2%. The well-developed plantlets regenerated from encapsulated nodal segments were
hardened-off successfully with 90% survival frequency. 相似文献
89.
Sanjay Dwivedi R. D. Tripathi Sudhakar Srivastava Ragini Singh Amit Kumar Preeti Tripathi Richa Dave U. N. Rai Debasis Chakrabarty P. K. Trivedi R. Tuli B. Adhikari M. K. Bag 《Protoplasma》2010,245(1-4):113-124
The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29–167 mg kg?1 dw), as well as As transfer factor (4–45%). Grains retained the least level of As (0.7–3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05–0.12 mg kg?1 dw), whereas that of As was high (0.4–1.68 mg kg?1 dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas. 相似文献
90.
Chromium and its compounds may cause disturbance in the nutrient level of the plants. Iron, manganese, copper, and zinc are
essential nutrient elements and required for balanced growth and development of plants, but chromium uptake sometimes disturbed
their concentration in plants. Therefore, in the present paper, an effort has been made to observe the effect of different
levels of Cr on nutrient uptake of Phyllanthus amarus and Solanum nigrum, the medicinally important plants of indigenous systems of medicine having hepatoprotective and diuretic properties. The
study revealed that Cr causes significant changes in nutrient uptake as compared to control plants. Besides, Cr-treated plants
showed growth depression and decrease in fresh and dry weight too. With the increase in Cr supply, accumulation of Cr in roots
was increased significantly. Concentration of manganese and zinc was also increased. However, copper concentration in both
the plants seemed less affected by Cr. 相似文献