全文获取类型
收费全文 | 264823篇 |
免费 | 16229篇 |
国内免费 | 17293篇 |
专业分类
林业 | 15862篇 |
农学 | 12123篇 |
基础科学 | 9639篇 |
27945篇 | |
综合类 | 106418篇 |
农作物 | 15755篇 |
水产渔业 | 11375篇 |
畜牧兽医 | 70802篇 |
园艺 | 15109篇 |
植物保护 | 13317篇 |
出版年
2024年 | 1558篇 |
2023年 | 4057篇 |
2022年 | 9010篇 |
2021年 | 9144篇 |
2020年 | 8578篇 |
2019年 | 8658篇 |
2018年 | 6894篇 |
2017年 | 10217篇 |
2016年 | 7151篇 |
2015年 | 10134篇 |
2014年 | 10884篇 |
2013年 | 14116篇 |
2012年 | 18400篇 |
2011年 | 19524篇 |
2010年 | 17727篇 |
2009年 | 16010篇 |
2008年 | 16623篇 |
2007年 | 15423篇 |
2006年 | 12862篇 |
2005年 | 10551篇 |
2004年 | 7226篇 |
2003年 | 5333篇 |
2002年 | 5365篇 |
2001年 | 5424篇 |
2000年 | 5139篇 |
1999年 | 2866篇 |
1998年 | 864篇 |
1997年 | 764篇 |
1995年 | 799篇 |
1994年 | 718篇 |
1992年 | 1593篇 |
1991年 | 1742篇 |
1990年 | 1659篇 |
1989年 | 1601篇 |
1988年 | 1479篇 |
1987年 | 1547篇 |
1986年 | 1599篇 |
1985年 | 1399篇 |
1984年 | 1188篇 |
1983年 | 1015篇 |
1979年 | 1055篇 |
1978年 | 829篇 |
1976年 | 711篇 |
1975年 | 746篇 |
1974年 | 1003篇 |
1973年 | 984篇 |
1972年 | 951篇 |
1971年 | 878篇 |
1970年 | 852篇 |
1969年 | 804篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Fish oil-induced yellow fat disease in rats. II. Enzyme histochemistry of adipose tissue 总被引:2,自引:0,他引:2
Adipose tissue in various stages of fish oil-induced yellow fat disease in the rat had the same acid phosphatase and 5-nucleotidase activity pattern as similar stages of the disorder in mink and pig. A weak acid phosphatase and 5-nucleotidase activity was seen in interstitial lipofuscin-laden macrophages in "stage M" yellow fat disease without fat cell degeneration. Activity of these macrophagic enzymes increased when there was fat cell degeneration ("stage S" and "stage E" yellow fat disease). This different phosphatase activity in the same cell type may result from phagocytosis of substrates with variable digestibility. Macrophages directly surrounding affected fat cells in steatitis areas ("stage S" and "stage E") had strong acid phosphatase and 5-nucleotidase activity. As in the pig, increased 5-nucleotidase activity was found in affected fat cells, which probably indicates plasma membrane damage. Increased nonspecific esterase activity occurred around affected fat cells. Only a small part of this esterase activity originated from inflammatory cells. This indicates that an increase of esterase activity in degenerating adipose tissue may be an endogeneous process in this tissue. 相似文献
993.
V Danielová D Málková J Minár B Rehse-Küpper Z Hájková J Halgos L Jedlicka 《Folia parasitologica》1978,25(2):187-190
In the years 1973 and 1975 mosquitoes and some other Diptera (Tabanidae, Simuliidae, Hippoboscidae) were tested for virus. 13,924 mosquitoes, 75 horseflies and 60 blackflies were processed in 1973. Five strains of Tahyna virus were isolated from mosquito species Aedes vexans. 3,378 mosquitoes and 12 sheep keds were tested for virus in 1975. Twelve strains of Calovo virus were isolated from Anopheles maculipennis and one strain of Tahyna virus was obtained from Aedes vexans mosquitoes. 相似文献
994.
L Cerva 《Folia parasitologica》1978,25(1):1-8
The effects of pH, various viscosity of the medium, changed ratio between the concentrations of dissolved and corpuscular components in the medium, and dissolved inorganic salts on the growth of axenic cultures of Naegleria fowleri and N. gruberi have been studied. The cultures were grown in liquid CALYG and BCS media. The pH optimum was 6.5 for N. fowleri and 6.0--6.5 for N. gruberi. No negative influence on the growth of N. fowleri was observed even at 0.5% concentration of highly viscous methylcellulose, whereas the growth of N. gruberi was distinctly inhibited by more than 0.2% of methycellulose. N. fowleri preferred the osmotorphic and N. gruberi phagotrophic nutrition in the given system of cultivation. The growth of both Naegleria species was inhibited by 0.1 N concentration of sodium chloride and potassium chloride without any significant difference in the tolerance. The inhibitory effect of these salts correlated primarily with the concentration of chloride anion. The ability to grow in a medium with increased viscosity and the preference for osmotrophic nutrtion are, besides the higher temperature optimum determined earlier, further characteristics of the pathogenic species N. fowleri. 相似文献
995.
A minialurized method of determining the toxicity of pesticides to large numbers or soil mitroorganisms is described. Bacteria. actinomycetes, yeasts, fungi and algae can be used as test organisms. A modification of the method allows determination of minimum inhibitory concentrations of pesticides to specific microorganisms. Some results obtained with herbicides are presented. Microméthodex pour éprauver la toxicité des pesticides vis-á-vis des micro-organismes Une micromethode pour determiner la toxicité des pesticides vis-á-vis de nombreux micro-organismes du sol est décrite. Des bactéries. des actinomycetes, des levures. des champignons et des algues peuvent ëtre utilisés comme organismes-tesis. Une modifitation de la méthode permel les determinations des concentrations minimales inhibitrices des pesticides vis-á-vis des micro-organismes specifiques. Quelques resultats obtenus avec des herbicides sont présentés. Miniaturisierte Methoden zur Prüf'ung der Toxizitüt von Pflan- zenhehandlumgsmit teln auf Mikraorganismen Es wird einc miniaturisierte Methode zur BestimmungderToxi- zität von Pfianzenbehandlungsmitteln für groβe Zablen von Bodenmikroorganismen beschrieben, Als Testorganismen können Bakterien. Actinomyceten. Hefen, Pilze und Algen benutzi werden. Eine Modifizierung der Methode gestattet die Bestimmung der Minimum-Hemmkonzentration von Pflanzen- behandlungsmitteln auf spezielle Mikroorganismen. Einige Ergebnisse, die mit Herbiziden erarbeitel wurden. sind darge-stellt. 相似文献
996.
997.
The absorption, distribution, and metabolic fate of [14C]ethephon in flue-cured tobacco (Nicotiana tabacum L.) was studied using autoradiography, thin-layer chromatography, high-voltage paper electrophoresis, and liquid scintillation spectrometry. Labeled ethephon penetrated mature leaf tissue easily and was translocated primarily in an acropetal direction. No 14C activity was detected in any other plant part except the treated leaf. The first day after treatment, most of the translocated 14C was detected in the midrib, and after 2 days radioactivity was noticed in veinal areas distal to the point of application. Four days later, however, 14C was detected in slight amounts only in the midrib, indicating that [14C]ethephon was rapidly degraded by the leaf tissue. Depending on leaf position on the stalk, as much as 92% of the radioactivity had disappeared from the leaf tissue during the first day after treatment, and as little as 5% of the applied radioactivity was recovered 4 days later. Methanol-extracted plant residues contained insignificant amounts of 14C. All of the 14C in methanol extracts was present in the form of a labeled compound with an Rf value corresponding to that of ethephon, indicating the absence of any detectable metabolites of the parent compound. Smoke analysis of cigarettes showed that more [14C]ethylene than 14CO2 was recovered in the main stream, whereas the trend was reversed in the case of side stream smoke. 相似文献
998.
1. Urea supplementation of low‐protein (125 g/kg) conventional‐type diets for layers, whether containing fish meal or not, did not appear advantageous.
2. Supplementation of the low‐protein diet with aspartic acid did not affect egg production rate or efficiency.
3. Soyabean meal supplementation of the low‐protein diet increased egg weight significantly whereas aspartic acid did not. 相似文献
999.
1000.
C Graul V Wildenhahn L Lyhs W Lohse 《Archiv fuer experimentelle veterinaermedizin》1976,30(5):643-650
Two experimental groups and series were compared (leghorns and broilers as well as two age groups of broilers) for their adaptive responses to repeated noise application. The noise was 100 dB and applied daily 30 minutes. The reference for comparison was the plasma-11-hydroxycorticosteroid concentration (11-OHKS). The results differed somewhat from those obtained earlier from one first short-time noise application, in that the rise in plasma glucocorticosteroid concentrations dropped from 431 to 210 per cent of the initial values in adult leghorns exposed to repeated noise stress over seven days. Adult broilers, however, did not exhibit any difference in the magnitude of rise of 11-OHKS concentrations by comparison between first and seven days of repeated stress. The initial values, however, were reached earlier by repeated noise application. 相似文献