全文获取类型
收费全文 | 7287篇 |
免费 | 355篇 |
国内免费 | 6篇 |
专业分类
林业 | 491篇 |
农学 | 155篇 |
基础科学 | 38篇 |
1368篇 | |
综合类 | 1273篇 |
农作物 | 238篇 |
水产渔业 | 558篇 |
畜牧兽医 | 2807篇 |
园艺 | 203篇 |
植物保护 | 517篇 |
出版年
2023年 | 61篇 |
2022年 | 73篇 |
2021年 | 152篇 |
2020年 | 155篇 |
2019年 | 184篇 |
2018年 | 181篇 |
2017年 | 152篇 |
2016年 | 182篇 |
2015年 | 162篇 |
2014年 | 190篇 |
2013年 | 276篇 |
2012年 | 483篇 |
2011年 | 608篇 |
2010年 | 304篇 |
2009年 | 245篇 |
2008年 | 499篇 |
2007年 | 527篇 |
2006年 | 469篇 |
2005年 | 436篇 |
2004年 | 417篇 |
2003年 | 384篇 |
2002年 | 395篇 |
2001年 | 72篇 |
2000年 | 55篇 |
1999年 | 71篇 |
1998年 | 54篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 50篇 |
1994年 | 48篇 |
1993年 | 44篇 |
1992年 | 34篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 43篇 |
1988年 | 33篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 31篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1975年 | 14篇 |
1973年 | 22篇 |
1970年 | 12篇 |
排序方式: 共有7648条查询结果,搜索用时 390 毫秒
171.
Mattana Efisio Peguero Brígido Di Sacco Alice Agramonte Wilvin Encarnación Castillo Wilkin Rafael Jiménez Francisco Clase Teodoro Pritchard Hugh W. Gómez-Barreiro Pablo Castillo-Lorenzo Elena Terrero Encarnación Marianny Way Michael J. García Ricardo Ulian Tiziana 《New Forests》2020,51(4):705-721
New Forests - Native trees from the Caribbean were tested for seed desiccation responses, by adapting the “100-seed test” protocol. Ninety-seven seed lots of 91 species were collected... 相似文献
172.
Karlsson Anneli S. Lesch Michael Weihermüller Lutz Thiele Björn Disko Ulrich Hofmann Diana Vereecken Harry Spielvogel Sandra 《Journal of Soils and Sediments》2020,20(4):2067-2081
Journal of Soils and Sediments - Pesticide contamination of river waters is a global problem, and therefore, authorities regularly monitor the water quality status. Especially, flood events might... 相似文献
173.
Wang Hai Ta Na Jin Ke Ji Baoming Schellenberg Michael P. Wei Zhijun Wang Zhen 《Journal of Soils and Sediments》2020,20(3):1344-1356
Journal of Soils and Sediments - Fungi play an essential role in regulating the functioning of terrestrial ecosystems and are sensitive to climate change factors. Climate change incidents, such as... 相似文献
174.
175.
M. v. Cotta M. v. Cotta Mördes v. Pannewib Robert Rühn Paur v. Stelzl v. Deltheim Schulze Q. v. Mikleben Lreiherr v. Lflanteuffel Lreiherr v. Berg Qeitel M. Lreiherr v. Berg v. Michael H. C. Bär Baer A. Chieriod Berger Rettftadt Gekner Wlrici Lreiherr v. Schmerzing Sprenger Pommrich v. Strune Matufchka v. E. Q. Brunft Rnaudt Mördlinger Rnipping v. Mangenheim C. A. Baum L. Mehlborn G. v. Stieglik H. v. Biegefar C. Grebe v.n Baumbach Braun R. Blohmer 《European Journal of Forest Research》1865,9(1):322-324
Ohne Zusammenfassung
f. f?chf. Dberforftmeifter.
f. bahr. Regierungs- und Forftrath von Mürzburg.
f. preuk. Dberforftmeifter aus Breslau.
f. f?chf. Dberforftmeifter.
f. bahr. Regierungs- und Forftrath von Augsburg.
f. bahr. Regierungs- und Forftrath aus Regensburg.
Dberj?germeifter von Braunfchweig.
f. bahr. Regierungs- und Forftrath aus München.
f. f?chf. Dberf?rfter.
f. f?chf. Dberforftmeifter.
f. f?chf. Dberforftrath.
herz. braunfchweig. Forftmeifter von Blanfenburg.
Direftor der fürftlich Cfterhazh’fchen Herrfchaft Spoly Parsto.
fürftl. fondershauf. Dberfortmeifter.
f. bahr. Redierf?rfter don Schmarzenbach.
f. preuk. Dberf?rfter.
f. f. Forftrath aus Brekburg.
f. preuk. Dberf?rfter von Altruppin.
f. hann?v. Forftmeifter von Rienburg.
Forftmeifter in preuk. Schleften.
f. preuk. Dberforftmeifter von Berlin.
herz. aftenburg. Dberfortmeifter.
f. preuk. Dberf?rfter.
f. f?chf. Dberf?rfter.
f. ruff. Forftfomiff?r aus Marfchau.
f. preuk. Forftinfpeftor.
f. f?chf. Forftinfpeftor.
grokh. meimar. Forftinfpeftor von Martfuhl.
f. mürttb. Dberf?rfter und Brofeffor aus Hohenheim.
f. hannov. Forftmeifter aus Hammeln.
Dberforftmeifter aus Sotha.
herz. altenburg. Dberf?rfter aus Hummelshain.
herz. altenburg. Revierf?rfter aus Milchwig.
herz. altenburg. geheimer Finanzrath und Dberforftmeifter.
herz. altenb. Dberforftmeifter aus Hummelshain.
grokh. f?chf. geheimer Dberforftrath aus Qifenach.
herz. naffau. Dberforftrath aus Miesbaden.
grokh. heff. Dberforftfefret?r aus Darmftadt.
f. f?chf. Dberforftmeifter. 相似文献
176.
Virginia Buechner-Maxwell Mark Crisman Michael Murray William Ley Geoffrey Saunders Amelia Walton 《Journal of Equine Veterinary Science》1996,16(9):375-379
Transtracheal wash and bronchoalveolar lavage are diagnostic techniques that have been adopted from human medicine for monitoring inflammatory changes in the airway of the horse. Transendoscopic biopsy has also proven to be a valuable tool for obtaining samples of the airway mucosa in human patients. A transendoscopic technique was developed in this study for obtaining a respiratory mucosal biopsy from standing, sedated horses. Six normal adult horses were sampled at eight-week intervals for a total of three sample periods. Horses were monitored for adverse effects of the technique and none were noted. Sample sites were completely healed after eight weeks with no gross or histologic abnormalities. Biopsy samples were 3 to 4 millimeters in diameter, and 17 of 18 samples provided interpretable histological sections. Methods for handling, staining and evaluating tissue were also developed. The results of this study demonstrated that airway mucosal biopsy is a safe, repeatable technique that can be performed in the sedated, standing horse. 相似文献
177.
Nakamura-Messenger K Messenger S Keller LP Clemett SJ Zolensky ME 《Science (New York, N.Y.)》2006,314(5804):1439-1442
Coordinated transmission electron microscopy and isotopic measurements of organic globules in the Tagish Lake meteorite shows that they have elevated ratios of nitrogen-15 to nitrogen-14 (1.2 to 2 times terrestrial) and of deuterium to hydrogen (2.5 to 9 times terrestrial). These isotopic anomalies are indicative of mass fractionation during chemical reactions at extremely low temperatures (10 to 20 kelvin), characteristic of cold molecular clouds and the outer protosolar disk. The globules probably originated as organic ice coatings on preexisting grains that were photochemically processed into refractory organic matter. The globules resemble cometary carbon, hydrogen, oxygen, and nitrogen (CHON) particles, suggesting that such grains were important constituents of the solar system starting materials. 相似文献
178.
Navarre WW Porwollik S Wang Y McClelland M Rosen H Libby SJ Fang FC 《Science (New York, N.Y.)》2006,313(5784):236-238
Horizontal gene transfer plays a major role in microbial evolution. However, newly acquired sequences can decrease fitness unless integrated into preexisting regulatory networks. We found that the histone-like nucleoid structuring protein (H-NS) selectively silences horizontally acquired genes by targeting sequences with GC content lower than the resident genome. Mutations in hns are lethal in Salmonella unless accompanied by compensatory mutations in other regulatory loci. Thus, H-NS provides a previously unrecognized mechanism of bacterial defense against foreign DNA, enabling the acquisition of DNA from exogenous sources while avoiding detrimental consequences from unregulated expression of newly acquired genes. Characteristic GC/AT ratios of bacterial genomes may facilitate discrimination between a cell's own DNA and foreign DNA. 相似文献
179.
新疆杨(Populus bolleana LAUCHE)是山西省北部乃至中国西北部重要的阔叶树造林树种,但目前发现只有雄性植株,它很可能是一个或几个无性系通过无性繁殖而大规模传播开来,基因变异狭窄,会给造林带来巨大的潜在危险。于2004年到2005年在山西省境内随机采集59个样树,在德国爱博斯瓦尔德大学(FH-Eberswalde)的生态实验室进行了同工酶分析。分析结果显示,在山西省境随机采样的59个新疆杨树中,88%的被猜测为是一个或同样的无性系。初步证实山西省境内的新疆杨造林基因变异有限,这就是说在山西境内新疆杨的造林潜在着巨大的风险。同时就避免或降低这种风险的可能性进行讨论。 相似文献
180.
Hu J Shibata Y Voss C Shemesh T Li Z Coughlin M Kozlov MM Rapoport TA Prinz WA 《Science (New York, N.Y.)》2008,319(5867):1247-1250
The tubular structure of the endoplasmic reticulum (ER) appears to be generated by integral membrane proteins, the reticulons and a protein family consisting of DP1 in mammals and Yop1p in yeast. Here, individual members of these families were found to be sufficient to generate membrane tubules. When we purified yeast Yop1p and incorporated it into proteoliposomes, narrow tubules (approximately 15 to 17 nanometers in diameter) were generated. Tubule formation occurred with different lipids; required essentially only the central portion of the protein, including its two long hydrophobic segments; and was prevented by mutations that affected tubule formation in vivo. Tubules were also formed by reconstituted purified yeast Rtn1p. Tubules made in vitro were narrower than normal ER tubules, due to a higher concentration of tubule-inducing proteins. The shape and oligomerization of the "morphogenic" proteins could explain the formation of the tubular ER. 相似文献