全文获取类型
| 收费全文 | 386篇 |
| 免费 | 11篇 |
专业分类
| 林业 | 109篇 |
| 农学 | 8篇 |
| 78篇 | |
| 综合类 | 46篇 |
| 农作物 | 7篇 |
| 水产渔业 | 4篇 |
| 畜牧兽医 | 98篇 |
| 园艺 | 5篇 |
| 植物保护 | 42篇 |
出版年
| 2020年 | 5篇 |
| 2019年 | 5篇 |
| 2017年 | 9篇 |
| 2016年 | 7篇 |
| 2015年 | 7篇 |
| 2014年 | 12篇 |
| 2013年 | 9篇 |
| 2012年 | 15篇 |
| 2011年 | 20篇 |
| 2010年 | 10篇 |
| 2009年 | 8篇 |
| 2008年 | 30篇 |
| 2007年 | 20篇 |
| 2006年 | 20篇 |
| 2005年 | 12篇 |
| 2004年 | 16篇 |
| 2003年 | 3篇 |
| 2002年 | 10篇 |
| 2001年 | 4篇 |
| 2000年 | 6篇 |
| 1999年 | 3篇 |
| 1995年 | 3篇 |
| 1992年 | 3篇 |
| 1990年 | 4篇 |
| 1988年 | 5篇 |
| 1985年 | 3篇 |
| 1984年 | 3篇 |
| 1983年 | 3篇 |
| 1981年 | 3篇 |
| 1979年 | 5篇 |
| 1978年 | 4篇 |
| 1974年 | 3篇 |
| 1971年 | 3篇 |
| 1970年 | 5篇 |
| 1938年 | 4篇 |
| 1934年 | 4篇 |
| 1925年 | 7篇 |
| 1924年 | 3篇 |
| 1923年 | 4篇 |
| 1921年 | 5篇 |
| 1911年 | 5篇 |
| 1910年 | 2篇 |
| 1908年 | 3篇 |
| 1907年 | 5篇 |
| 1905年 | 2篇 |
| 1898年 | 2篇 |
| 1897年 | 2篇 |
| 1896年 | 2篇 |
| 1895年 | 3篇 |
| 1894年 | 2篇 |
排序方式： 共有397条查询结果，搜索用时 15 毫秒
11.
12.
Scaevola aemula is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties of S. aemula ‘New Wonder’ in response to photosynthetically active radiation (PAR), carbon dioxide concentration, and leaf temperature. Net CO2 assimilation rate (A) was responsive to CO2, exhibiting a saturation when intercellular CO2 concentration (Ci) was greater than 600 μmol mol−1. Net CO2 assimilation rate and dark respiration rate (Rd) were 23.1 and 2.3 μmol m−2 s−1, respectively, at 25 °C and PAR = 1500 μmol m−2 s−1. Net CO2 assimilation rates were similar at leaf temperatures between 20 and 30 °C but significantly reduced at 15 °C. These gas exchange results were used to test the extendibility of a coupled gas exchange model previously developed for cut-roses. Utilizing the gas exchange data measured at 25 °C leaf temperature, several model parameters were independently determined for S. aemula. Model predictions were then compared with observations at different leaf temperatures. The model predicted the rates of net CO2 assimilation and transpiration of S. aemula reasonably well. Without additional calibration, the model was capable of predicting the temperature dependence of net CO2 assimilation and transpiration rates. Applying the model to predict the effects of supplemental lighting and CO2 enrichment on canopy photosynthesis and transpiration rates, we show that this model could be a useful tool for examining environmental control options for S. aemula production in the greenhouse. 相似文献
13.
14.
Heinrich Wilhelm Weber 《Forstwissenschaftliches Centralblatt》1922,44(6):214-224
Ohne Zusammenfassung 相似文献
15.
H W Heinrich 《Archiv fuer experimentelle veterinaermedizin》1990,44(6):849-853
Several DNA viruses have recently emerged as useful eucaryotic vectors. The ability to incorporate large amounts of foreign DNA in the vaccinia virus genome without loss of infectivity, evidence to correct glycosylation and processing of expressed proteins and the wide host range of vaccinia virus all contribute to the versatility of this system as a research tool. The development of recombinant DNA technology and its use in genetic engineering has provided opportunities to construct DNA-recombinant viruses that can provide protection against a spectrum of diseases. A brief account is given of current developments and future prospects of DNA recombinant viruses, with particular reference to vaccinia virus. 相似文献
16.
17.
Heinrich W. K. Müller 《Journal of pest science》1960,33(7):99-101
Zusammenfassung Auf Grund seiner ausgezeichneten Tiefenwirkung und einer noch ausreichenden Dauerwirkung hat sich der Oleo-Phosphorsäureester in Versuchen gegen die Erdbeermilbe und in einem praktischen Einsaß gegen einen Erdbeerwickler als brauchbares Akarizid bzw. Insektizid erwiesen. Er wird daher auf Grund der weiteren guten Erfahrungen mit dieser Wirkstoffzubereitung im Kern- und Steinobstbau auch gegen andere wichtige Erdbeerschädlinge, insbesondere gegen Rote Spinne und Erdbeerblattlaus als wichtigen Virusüberträger, empfohlen. Der Oleo-Phosphorsäureester wird zu einer Art Universalmittel, wenn durch ihn auch noch Erdbeerstengel- und-blütenstecher erfaßt werden, vielleicht sogar auch parasitische Nematoden (Stengel- und Blattä lchen). Gegen freilebende (ektoparasitische) Nematoden werden vorerst weiterhin nur die Spezialmittel zur Bodenentseuchung in Betracht kommen.Eine einmalige Sprißung, etwa zehn Tage vor der Erdbeerblüte, mit Folidol-Öl 0,5%, 10001 je ha, und eine weitere Sprißung bald nach der Ernte mit 2000 I je ha werden daher im allgemeinen als ausreichend für die Bekämpfung tierischer Schädlinge im Erdbeeranbau betrachtet. Nur gegen die Blatt- und Stengelälchen wird noch eine zusäßliche Behandlung bei Blattaustrieb im Frühjahr notwendig sein.Hygienische Bedenken bestehen zunächst bei dem Einsaß des Oleo-Phosphorsäureesters vor der Erdbeerblüte nicht; in umfangreichen Testen konnte keine merkliche Geschmacksbeeinflussung durch den Wirkstoff festgestellt werden. Auch die Karenzzeit (etwa 14 Tage) dürfte bei rechtzeitigem Einsaß vor der Blüte mit mindestens 6 Wochen bis zur Ernte reichlich bemessen sein. Nachbarkulturen, die früh geerntet werden, z. B. Frühgemüse, dürfen vom Sprißstrahl oder von Abtrift selbstverständlich nicht betroffen werden.Thiodan wird als Mittel gegen die Erdbeermilbe und andere Erdbeerschädlinge kaum in Betracht kommen, da es bei einer Vorblütenspritzung eine schon merkliche Geschmacksbeeinflussung der Erdbeerfrüchte hinterlä ßt. 相似文献
18.
Mayada Gwida Maged El-Ashker Falk Melzer Mohamed El-Diasty Mohamed El-Beskawy Heinrich Neubauer 《Irish veterinary journal》2015,69(1):3
Background
Bovine brucellosis remains one of the most prevalent zoonotic infections affecting dairy cattle in developing countries where the applied control programs often fail. We analyzed the epidemiologic pattern of bovine brucellosis in a dairy cattle herd that showed several cases of abortions after regular vaccination with RB51 (B. abortus vaccine). In 2013 thirty dairy cows, from a Holstein-Friesian dairy herd with a population of 600 cattle, aborted five months post vaccination by a regular RB51 vaccine. Blood samples were drawn from milking cows and growing heifers, as well as heifers and cows pregnant up to 6 months. These samples were collected in June 2013 (n?=?257) and May 2014 (n?=?263) and were tested by real time (rt)-PCR as well as serological tests, in particular Rose Bengal Test (RBT), Enzyme-Linked Immunosorbent Assays (ELISA) and Fluorescence Polarization Assay. Tissue specimens were also collected from an aborted fetus and cultured. Isolates were subjected to bacteriological typing tests at the genus and species levels.Results
Five months post vaccination with RB51 vaccine, Brucella (B.) DNA was detected in blood samples of cows by rt-PCR. The serological tests also revealed the spread of Brucella field strains within the herd in 2013. Four Brucella isolates were recovered from specimens collected from the aborted fetus. These isolates were typed as follows: one B. abortus RB51 vaccine strain and three isolates of B. abortus field strain. The seropositive cows with positive rt-PCR might indicate an infection by the Brucella field strain; while the positive rt-PCR results from seronegative animals may either be due to circulating RB51 vaccine DNA in vaccinated animals or to circulating field strain in infected animals before seroconversion.Conclusion
The results herein suggest that PCR can be a good supplementary tool in an outbreak situation, if an assay is available that can differentiate vaccine and field strains with a high analytical sensitivity. We recommend using RBT and ELISA in parallel in outbreak situations, to identify as many infected animals as possible during the initial screenings. This test procedure should be repeated for at least three successive negative tests, with one month interval.19.
Luke Randall Katharina Heinrich Robert Horton Lucy Brunton Matthew Sharman Victoria Bailey-Horne Meenaxi Sharma Ian McLaren Nick Coldham Chris Teale Jeff Jones 《Research in veterinary science》2014
Waste milk samples from 103 farms in England and Wales were examined for the presence of β-lactam antibiotics and ESBL-producing Enterobacteriaceae. Approximately 10 months after the initial sampling, further waste milk, environmental and faecal samples from farms shown to be positive for CTX-M Escherichia coli were investigated further. Isolates with an ESBL phenotype were tested by PCR for the presence of blaCTX-M, blaOXA, blaSHV and blaTEM genes. Isolates positive for blaCTX-M were sequenced to determine CTX-M type. Representative isolates were further examined by PFGE, plasmid replicon typing and serotyping. Of particular interest, 21.4% of waste milk samples contained residues of the cephalosporin cefquinome, which was significantly associated with CTX-M bacteria. Such bacteria occurred in 5.8% of the waste milk samples (including 3.9% CTX-M E. coli). CTX-M types identified were 1, 14, 14b and 15, but none of the E. coli were serotype O25, the serotype of the human pandemic strain. 相似文献
20.
Bulk stomatal resistance of Vicia faba and its dependence on soil water content Bulk stomatal resistance of beans (Vicia faba L.,) as a function of soil water content was estimated for 41 days by comparison of potential transpiration, determined from meteorological data, and actual transpiration, determined from soil water losses. The resistance of beans is about 46 s/m if soil water content is above 70 % of available field capacity and increases strongly in dryer situations. This behaviour can be described by an exponential function. 相似文献