全文获取类型
收费全文 | 720篇 |
免费 | 53篇 |
专业分类
林业 | 15篇 |
农学 | 24篇 |
基础科学 | 3篇 |
54篇 | |
综合类 | 135篇 |
农作物 | 20篇 |
水产渔业 | 36篇 |
畜牧兽医 | 454篇 |
园艺 | 5篇 |
植物保护 | 27篇 |
出版年
2023年 | 6篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 32篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 24篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 33篇 |
2006年 | 34篇 |
2005年 | 36篇 |
2004年 | 22篇 |
2003年 | 23篇 |
2002年 | 28篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1993年 | 6篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 10篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1914年 | 4篇 |
1902年 | 4篇 |
排序方式: 共有773条查询结果,搜索用时 15 毫秒
211.
Clarke JM 《Science (New York, N.Y.)》1911,33(843):284-296
212.
Clarke FW 《Science (New York, N.Y.)》1909,30(762):161-171
213.
214.
215.
Particle-associated pollutants (totaling 10(7) metric tons per year) are introduced into the New York Bight by ocean dumping, estuarine discharge, sewage outfalls, eolian transport, and shipping waste and spillage. Oceanic and estuarine circulation processes dilute and transport the particles by a natural dispersal system that also tends to be highly distributive; particle-associated pollutants apparently seek the same sinks in the Hudson River shelf valley and intracoastal weltlands, regardless of their point of introduction. 相似文献
216.
217.
McDermott R Trabesinger AH Muck M Hahn EL Pines A Clarke J 《Science (New York, N.Y.)》2002,295(5563):2247-2249
We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesla and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for "pure J spectroscopy" as a diagnostic tool for the detection of molecules in low magnetic fields. 相似文献
218.
Vitamin D plays an important role in regulating calcium metabolism and in the development and maintenance of skeletal health of companion animals. There is also a growing interest in understanding the role vitamin D plays in non-skeletal health in both human and veterinary patients. This review provides an update of our current understanding of vitamin D biology in dogs and cats and gives an overview of how vitamin D metabolism can be assessed in companion animals. Congenital and acquired vitamin D disorders are then summarised before the review concludes with a summary of recent studies which have explored the role of vitamin D in the development and outcomes of non-skeletal diseases of dogs and cats. 相似文献
219.
We have recently presented a method for the determination of quickly reacting aluminium in natural waters based on kinetic discrimination in a flow system. This method has been further validated using both an isolated fulvic acid and natural humus-rich waters. Different reaction times were used, further clarifying the response of aluminium complexed with humic and fulvic acids. Equilibrium dialysis was also used as a reference method for comparison. With the reaction time used normally, 2.3 s, aluminium complexed with humic or fulvic acids was shown not to be measured with our method. These results suggest that our method may be used for studies of the complexation of aluminium with humic and fulvic acids. We have compared results from a series of solutions with varying concentrations of fulvic acids with calculations based on two different models obtained from complexation studies performed by potentiometric titrations and by equilibrium dialysis. The results show fair agreement and suggest that our method can be used for such studies. This approach is more sensitive and rapid than potentiometric titrations, enabling studies of humus interactions with aluminium at concentrations similar to those found in natural waters. 相似文献
220.
Dooley JJ Sage HD Clarke MA Brown HM Garrett SD 《Journal of agricultural and food chemistry》2005,53(9):3348-3357
Identification of 10 white fish species associated with U.K. food products was achieved using PCR-RFLP of the mitochondrial cytochrome b gene. Use of lab-on-a-chip capillary electrophoresis for end-point analysis enabled accurate sizing of DNA fragments and identification of fish species at a level of 5% (w/w) in a fish admixture. One restriction enzyme, DdeI, allowed discrimination of eight species. When combined with NlaIII and HaeIII, specific profiles for all 10 species were generated. The method was applied to a range of products and subjected to an interlaboratory study carried out by five U.K. food control laboratories. One hundred percent correct identification of single species samples and six of nine admixture samples was achieved by all laboratories. The results indicated that fish species identification could be carried out using a database of PCR-RFLP profiles without the need for reference materials. 相似文献