全文获取类型
收费全文 | 11378篇 |
免费 | 916篇 |
国内免费 | 768篇 |
专业分类
13062篇 |
出版年
2024年 | 20篇 |
2023年 | 214篇 |
2022年 | 398篇 |
2021年 | 633篇 |
2020年 | 396篇 |
2019年 | 514篇 |
2018年 | 536篇 |
2017年 | 341篇 |
2016年 | 512篇 |
2015年 | 713篇 |
2014年 | 793篇 |
2013年 | 916篇 |
2012年 | 1070篇 |
2011年 | 931篇 |
2010年 | 573篇 |
2009年 | 497篇 |
2008年 | 537篇 |
2007年 | 495篇 |
2006年 | 428篇 |
2005年 | 364篇 |
2004年 | 304篇 |
2003年 | 228篇 |
2002年 | 187篇 |
2001年 | 202篇 |
2000年 | 170篇 |
1999年 | 176篇 |
1998年 | 101篇 |
1997年 | 125篇 |
1996年 | 105篇 |
1995年 | 87篇 |
1994年 | 92篇 |
1993年 | 49篇 |
1992年 | 74篇 |
1991年 | 55篇 |
1990年 | 47篇 |
1989年 | 46篇 |
1988年 | 38篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Virological survey of rhesus monkeys in China 总被引:1,自引:0,他引:1
A virological survey of rhesus monkeys captured in China for 13 viruses and/or antibodies was performed. Antigens used were SFV, SF40, HSV-1, Sa11, measles, vaccinia, epidemic or simian hemorrhagic fever, Langat, Kunming, poliomyelitis, HIV, SV41 and rubella. Monkeys were from Sichuan, Hunan, Guizhou, Yunnan and Guangxi provinces. Antibody was detected to all the listed viruses except HIV, SV41 and rubella. Both SFV and SV40 were recovered from monkeys, but H. simiae, LCM and coxsackieviruses were not. 相似文献
113.
Aims The diversity–productivity relationship is one of the most critical questions in ecology and can be altered by environmental factors. Hydrological fluctuation affects growth of wetland plants, and such effects vary with plant species. Therefore, we hypothesized that hydrological fluctuation changes effects of species richness on productivity of wetland plant communities.Methods We constructed wetland plant communities consisting of three or six wetland plant species and subjected them to hydrological fluctuation (i.e. gradually changing water level) of two frequencies and two ranges, with unchanged water level as the control. We measured height, root and shoot dry mass of each plant at harvest.Important findings Hydrological fluctuation significantly decreased biomass of wetland plant communities, which was due to impacts of fluctuation range, but not those of fluctuation frequency. Community biomass was significantly higher when species richness was higher, and such an effect did not depend on hydrological fluctuation. Therefore, hydrological fluctuation can decrease the productivity of wetland plant communities but may not alter the diversity–productivity relationship. 相似文献
114.
115.
Haifang Yan Yun Luo Zhongrong Jiang Fei Wang Bo Zhou Qijiang Xu 《Plant Molecular Biology Reporter》2016,34(2):467-482
116.
Hershko DD Robb BW Luo GJ Hungness ES Hasselgren PO 《Journal of cellular biochemistry》2003,90(3):627-640
117.
Z. -L. Liu S. Yuan W. -J. Liu J. -B. Du W. -J. Tian M. -H. Luo H. -H. Lin 《Photosynthetica》2008,46(1):73-78
NYB is chlorophyll-less barley mutant, which is controlled by a recessive nuclear gene. The mutation mechanism is revealed. The
activities of enzymes transforming 5-aminolevulinic acid into protochlorophyllide were the same in both NYB and the wild type (WT), but the activity of the protochlorophyllide oxidoreductase (POR) in WT was much higher than that
of NYB. Most of the photosystem 2 apoproteins were present in both WT and NYB, suggesting that the capability of protein synthesis was probably fully preserved in the mutant. Thus chlorophyll (Chl) biosynthesis
in NYB was hampered at conversion form protochlorophyllide (Pchlide) into chlorophyllide. The open reading frame of porB gene in NYB was inserted with a 95 bp fragment, which included a stop codon. The NYB mutant is a very useful material for studies of Chl biosynthesis, chloroplast signalling, and structure of light-harvesting
POR-Pchlide complex (LHPP). 相似文献
118.
Yu. B. Akhanaev M. N. Berim X. Jiang D. A. Kutcherov L. Luo Yu. M. Malysh S. Ya. Reznik A. Kh. Saulich V. A. Sobolev Yu. S. Tokarev A. N. Frolov L. Zhang 《Entomological Review》2013,93(7):814-818
The beet webworm, Loxostege sticticalis L., is a very dangerous polyphagous insect pest whose outbreaks periodically occur in southern Russia and northern China. The aim of our work was to describe the photoperiodic response of beet webworm populations from western (Krasnodar Territory and Rostov Province) and eastern [Buryatia and China (Hebei Province)] parts of the pest range. The insects were reared under constant photoperiods of 12–18 h and constant temperatures of 19–25°C. Incidence of diapause at different photoperiods did not show any considerable geographic differences, and the critical day length at which 50% of prepupae arrested their development was about 14–15 h in all the populations studied at experimental temperatures. The results obtained agree with the hypothesis on the existence of an area (or areas) where the pest survives during adverse periods and wherefrom it spreads when an outbreak begins (Saulich et al., 1983; Goryshin et al., 1986). Presumably, the larger part of the pest native habitats (to the north of the steppe zone) is occupied by temporary populations, incapable of surviving for long periods without an inflow of migrants from more southerly steppe regions. 相似文献
119.
120.
Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity 总被引:1,自引:0,他引:1
Casein kinases are critical in cell division and differentiation across species. A rice cDNA fragment encoding a putative casein kinase I (CKI) was identified via cDNA macroarray under brassinosteroid (BR) treatment, and a 1939-bp full-length cDNA, OsCKI1, was isolated and found to encode a putative 463-aa protein. RT-PCR and Northern blot analysis indicated that OsCKI1 was constitutively expressed in various rice tissues and upregulated by treatments with BR and abscisic acid (ABA). Enzymatic assay of recombinant OsCKI1 proteins expressed in Escherichia coli showed that the protein was capable of phosphorylating casein. The physiological roles of OsCKI1 were studied through antisense transgenic approaches, and homozygous transgenic plants showed abnormal root development, including fewer lateral and adventitious roots, and shortened primary roots as a result of reduced cell elongation. Treatment of wild-type plants with CKI-7, a specific inhibitor of CKI, also confirmed these functions of OsCKI1. Interestingly, in transgenic and CKI-7-treated plants, exogenously supplied IAA could restore normal root development, and measurement of free IAA content in CKI-deficient primary and adventitious roots revealed altered auxin content, indicating that OsCKI1 is involved in auxin metabolism or that it may affect auxin levels. Transgenic plants were less sensitive than control plants to ABA or BR treatment during germination, suggesting that OsCKI1 may be involved in various hormone-signaling pathways. OsCKI1-GFP fusion studies revealed the localization of OsCKI1 to the nucleus, suggesting a possible involvement in regulation of gene expression. In OsCKI1-deficient plants, differential gene expression was investigated using cDNA chip technology, and results indicated that genes related to signal transduction and hormone metabolism were indeed with altered expression. 相似文献