全文获取类型
收费全文 | 15940篇 |
免费 | 798篇 |
国内免费 | 21篇 |
专业分类
16759篇 |
出版年
2023年 | 111篇 |
2022年 | 273篇 |
2021年 | 421篇 |
2020年 | 253篇 |
2019年 | 257篇 |
2018年 | 398篇 |
2017年 | 431篇 |
2016年 | 497篇 |
2015年 | 673篇 |
2014年 | 742篇 |
2013年 | 1038篇 |
2012年 | 1141篇 |
2011年 | 1040篇 |
2010年 | 626篇 |
2009年 | 573篇 |
2008年 | 656篇 |
2007年 | 649篇 |
2006年 | 563篇 |
2005年 | 475篇 |
2004年 | 448篇 |
2003年 | 380篇 |
2002年 | 346篇 |
2001年 | 335篇 |
2000年 | 305篇 |
1999年 | 244篇 |
1998年 | 125篇 |
1997年 | 106篇 |
1996年 | 96篇 |
1995年 | 112篇 |
1994年 | 101篇 |
1993年 | 95篇 |
1992年 | 221篇 |
1991年 | 206篇 |
1990年 | 200篇 |
1989年 | 193篇 |
1988年 | 168篇 |
1987年 | 164篇 |
1986年 | 148篇 |
1985年 | 174篇 |
1984年 | 167篇 |
1983年 | 115篇 |
1982年 | 112篇 |
1981年 | 99篇 |
1980年 | 92篇 |
1979年 | 147篇 |
1978年 | 109篇 |
1977年 | 95篇 |
1974年 | 118篇 |
1973年 | 91篇 |
1972年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
161.
Aftab Ahamed Ajay Singh Owen P. Ward 《World journal of microbiology & biotechnology》2005,21(8-9):1577-1583
Summary While Aspergillus strains are also being considered as potential hosts for production of extracellular heterologous proteins, the proteases
produced by the host are highly problematic in that they typically modify and degrade the recombinant proteins. Culture-based
approaches for minimization of protease activity in culture supernatants of Aspergillus niger NRRL-3 included reduction or elimination of peptide nitrogen in the medium, preferential use of a defined salts medium rather
than a non-peptide nitrogen medium containing yeast-nitrogen base, supplementation of the medium with carboxymethylcellulose
and cultivation at pH 6.5 rather than 7.5. In general, increased proteolytic activity was observed after maximum biomass was
observed and biomass was declining suggesting the majority of protease activity was released by cell lysis. Carboxymethylcellulose
shifted mycelial morphology from pelleted to filamentous. Mycelium lysis in the centre of pellets, with resultant release
of intracellular proteases, would explain why filamentous cultures exhibited much lower proteolytic activity than pelleted
cultures. 相似文献
162.
Amod D. Kulkarni Viswanath Kiron Jan H. W. M. Rombout Monica F. Brinchmann Jorge M. O. Fernandes Naduvilamuriparampu S. Sudheer Bright I. S. Singh 《Proteomics》2014,14(13-14):1660-1673
White spot syndrome virus (WSSV) is a pathogen that causes considerable mortality of the farmed shrimp, Penaeus monodon. Candidate ‘vaccines’, WSSV envelope protein VP28 and formalin‐inactivated WSSV, can provide short‐lived protection against the virus. In this study, P. monodon was orally intubated with the aforementioned vaccine candidates, and protein expression in the gut of immunised shrimps was profiled. The alterations in protein profiles in shrimps infected orally with live‐WSSV were also examined. Seventeen of the identified proteins in the vaccine and WSSV‐intubated shrimps varied significantly compared to those in the control shrimps. These proteins, classified under exoskeletal, cytoskeletal, immune‐related, intracellular organelle part, intracellular calcium‐binding or energy metabolism, are thought to directly or indirectly affect shrimp's immunity. The changes in the expression levels of crustacyanin, serine proteases, myosin light chain, and ER protein 57 observed in orally vaccinated shrimp may probably be linked to immunoprotective responses. On the other hand, altered expression of proteins linked to exoskeleton, calcium regulation and energy metabolism in WSSV‐intubated shrimps is likely to symbolise disturbances in calcium homeostasis and energy metabolism. 相似文献
163.
Balan Biji Dhaulaniya Amit S. Varma Diksha A. Sodhi Kushneet K. Kumar Mohit Tiwari Manisha Singh Dileep Kumar 《Archives of microbiology》2021,203(1):13-30
Archives of Microbiology - Biofilms are structured microbial communities of single or multiple populations in which microbial cells adhere to a surface and get embedded in extracellular polymeric... 相似文献
164.
Chromosomal mapping and nucleotide sequence of a human DNA autonomously replicating sequence 总被引:1,自引:0,他引:1
A 1.1-kb human DNA fragment (ARSH1) capable of functioning as a putative origin of replication in yeast cells has been characterized both by in situ hybridization to human metaphase chromosomes and by DNA sequencing. Our hybridization studies show a preferential localization of ARSH1 in chromosome regions 1p34-36 and 2q34-37. DNA sequence analysis indicates that in addition to the consensus sequence required for ARS function in yeast cells, nuclear matrix-associated DNA motifs are also present in the 1.1-kb fragment. These results suggest that ARSH1 sequences may serve as points of anchorage to the nuclear matrix for chromosomes 1 and 2. 相似文献
165.
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
166.
Sivakoti Ramana Ashis Kumar Biswas Amar Bahadur Singh Ajay Narendar Kumar Ahirwar Annangi Subba Rao 《International journal of phytoremediation》2015,17(4):363-368
The potential of an ornamental shrub Crown of thorns (Euphorbia milli) was evaluated for remediation of soil contaminated with Cr. The plant is one of the rare succulent ornamental shrubs with a slow to moderate growth rate and is capable of blooming almost year-round. The plant could tolerate well up to 75 mg of applied Cr and beyond that there was mortality of plants. Though the plant could not be classified as a hyperaccumulator, the plant was still very efficient in translocating Cr from roots to shoots as evident from the data on uptake and translocation efficiency values. The translocation efficiency of over 80% in our study demonstrates that a large proportion of Cr has been translocated to the harvestable biomass of the plant and therefore, this plant could be effectively recommended for the remediation of soils contaminated with low to medium level of contamination i.e., up to 50 mg/kg soil. 相似文献
167.
Ishwar Singh Upendra Kumar S. K. Singh Charu Gupta Madhulika Singh S. R. Kushwaha 《Physiology and Molecular Biology of Plants》2012,18(3):229-236
Germination and early seedling growth are important for establishment of maize because maize is chilling sensitive crop and low temperature during early period of growth can be detrimental to subsequent crop growth and productivity. Therefore, it is important to protect maize seedling from cold stress. A study was conducted on induced cold tolerance by 24-epibrassinoslide (EBR) at the Indian Agricultural Research Institute, New Delhi, India. Maize seedlings were raised in green house condition (25/18 °C day-night temperatures). Ten days old seedlings were treated with EBR (0.0, 0.01, 0.1, 1.0 and 10 μM) and then divided into two sets, one set was kept in greenhouse (25/18 °C day-night temperatures) and another was transferred to net house (cold stress). Data on various morpho-physiological traits was recorded after 7, 14 and 21 days of treatment. Exogenous application of 1.0 μM EBR had significant effect on growth and morpho-physiological traits under both conditions. The maize seedlings treated with EBR were more tolerant to cold stress than the untreated one. Significant increase in plant height, dry matter accumulation, chlorophyll content, total soluble proteins and starch contents was observed under both conditions, however, the results were more pronounced under cold stress. 1.0 μ M concentration being the most effective under both conditions. Maintenance of high tissue water content, reduced membrane injury index, increased total chlorophyll, soluble sugar and protein content were taken as the possible indicators of EBR induced chilling tolerance. 相似文献
168.
Background
The aim of this study was to investigate the anticancer activity and mechanism of action of Noscapine alone and in combination with Doxorubicin against triple negative breast cancer (TNBC).Methods
TNBC cells were pretreated with Noscapine or Doxorubicin or combination and combination index values were calculated using isobolographic method. Apoptosis was assessed by TUNEL staining. Female athymic Nu/nu mice were xenografted with MDA-MB-231 cells and the efficacy of Noscapine, Doxorubicin and combination was determined. Protein expression, immunohistochemical staining were evaluated in harvested tumor tissues.Results
Noscapine inhibited growth of MDA-MB-231 and MDA-MB-468 cells with the IC50 values of 36.16±3.76 and 42.7±4.3 µM respectively. The CI values (<0.59) were suggestive of strong synergistic interaction between Noscapine and Doxorubicin and combination treatment showed significant increase in apoptotic cells. Noscapine showed dose dependent reduction in the tumor volumes at a dose of 150–550 mg/kg/day compared to controls. Noscapine (300 mg/kg), Doxorubicin (1.5 mg/kg) and combination treatment reduced tumor volume by 39.4±5.8, 34.2±5.7 and 82.9±4.5 percent respectively and showed decreased expression of NF-KB pathway proteins, VEGF, cell survival, and increased expression of apoptotic and growth inhibitory proteins compared to single-agent treatment and control groups.Conclusions
Noscapine potentiated the anticancer activity of Doxorubicin in a synergistic manner against TNBC tumors via inactivation of NF-KB and anti-angiogenic pathways while stimulating apoptosis. These findings suggest potential benefit for use of oral Noscapine and Doxorubicin combination therapy for treatment of more aggressive TNBC. 相似文献169.
170.
Varunendra Singh Rawat Jasleen Kaur Sakshi Bhagwat Manisha Arora Pandit Charu Dogra Rawat 《Restoration Ecology》2023,31(1):e13688
Ecosystem degradation is a major environmental threat. Beyond conservation, restoration of degraded ecosystems is a prerequisite to reinstate their ability to provide essential services and benefits. Most of the restoration efforts focus on aboveground restoration, that is, plants, under the assumption that establishment of plant species will reestablish the faunal and microbial species. While this may be true for some cases, it is not a general rule. Reestablishment of microbial communities by dedicated efforts is also necessary for successful restoration, as cycling of essential nutrients for plant growth and decomposition of organic matter is dependent on them. The role of microbial fertilizers and efficient organisms used in agriculture needs to be explored in restoration. Testing of symbiotic interactions between potential plant growth-promoting Rhizobacteria and plants native to a degraded ecosystem can be conducted and utilized for successful establishment of plant species. However, utmost care must be taken while introducing new microbial species or non-native plant species to an area, as they can adversely affect the resident microbial community. Techniques like phospholipid fatty-acid analysis can be used for taxonomic identification of large microbial groups in non-degraded reference ecosystems before introducing microbial species into a degraded ecosystem. For use of microbes in restoration, more studies on microbe-plant interactions need to be conducted. For use of Soil Microbial Community (SMC) as indicators of restoration, their role and function in the ecology of the area need to be elucidated by employing all the available techniques. 相似文献