全文获取类型
收费全文 | 14381篇 |
免费 | 1021篇 |
国内免费 | 113篇 |
专业分类
林业 | 1315篇 |
农学 | 593篇 |
基础科学 | 118篇 |
3639篇 | |
综合类 | 741篇 |
农作物 | 773篇 |
水产渔业 | 1457篇 |
畜牧兽医 | 5357篇 |
园艺 | 246篇 |
植物保护 | 1276篇 |
出版年
2023年 | 129篇 |
2022年 | 195篇 |
2021年 | 368篇 |
2020年 | 398篇 |
2019年 | 342篇 |
2018年 | 634篇 |
2017年 | 659篇 |
2016年 | 644篇 |
2015年 | 513篇 |
2014年 | 594篇 |
2013年 | 924篇 |
2012年 | 1155篇 |
2011年 | 1081篇 |
2010年 | 641篇 |
2009年 | 540篇 |
2008年 | 819篇 |
2007年 | 819篇 |
2006年 | 687篇 |
2005年 | 687篇 |
2004年 | 561篇 |
2003年 | 542篇 |
2002年 | 445篇 |
2001年 | 301篇 |
2000年 | 305篇 |
1999年 | 240篇 |
1998年 | 68篇 |
1997年 | 71篇 |
1996年 | 48篇 |
1995年 | 46篇 |
1994年 | 34篇 |
1993年 | 39篇 |
1992年 | 70篇 |
1991年 | 50篇 |
1990年 | 60篇 |
1989年 | 58篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 50篇 |
1985年 | 58篇 |
1984年 | 44篇 |
1983年 | 40篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1979年 | 37篇 |
1978年 | 32篇 |
1977年 | 31篇 |
1974年 | 31篇 |
1973年 | 46篇 |
1972年 | 32篇 |
1971年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Meat tins denoted as pork in natural juice, beef with bacon, luncheon meat and liver paté, all produced in a food-processing plant, were stored under definite conditions (temperature 21 degrees C, relative humidity 73%) for three years. Before the long-term storage and then in half-year intervals, the contents of the residues of chlorinated pesticides, including HCB (hexachlorobenzene), gamma-HCH (gamma isomer of hexachlorocyclohexane) and pp'DDE (1,1-dichloro-2,2-bis/p-chlorofenyl/-ethylene), were determined in the above-mentioned final products by the method of gas chromatography. As suggested by the records of the changes in the pesticide residue contents in the meat tins during their long-term storage, the average contents of all chlorinated carbohydrates gradually decrease with the length of storage and the "reduction" of residues varies with the kind of final product and with the pesticides. In HCB the reduction ranged from 18.4 to 34.4%, in gamma-HCH from 36.2 to 80.4% and in pp'DDE from 23.9 to 48.9%. 相似文献
13.
Morin M Sauvageau R Phaneuf JB Teuscher E Beauregard M Lagacé A 《The Canadian veterinary journal. La revue veterinaire canadienne》1984,25(12):440-442
Necropsy records of 36 sows with torsion of abdominal organs involving individually the stomach, the spleen, a liver lobe or the intestine were reviewed for the years 1970 to 1983, and the age, the clinical signs and the gross lesions were recorded. These acute abdominal accidents were characterized clinically by sudden death. Dry sows from large breeding units were affected. Twenty-six cases were diagnosed between January 1981 and December 1983 while only ten cases had been seen between 1970 and 1980. Gastric torsion was the most common condition (40% of the cases) and the other three conditions were equally represented (20% each). Management practises that could be responsible for the apparent increase in occurrence of this problem are discussed. 相似文献
14.
Transitional Cell Carcinoma of the Urinary Bladder in a Beluga Whale (Delphinapterus leucas) 总被引:1,自引:0,他引:1 下载免费PDF全文
Martineau D Lagacé A Massé R Morin M Béland P 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(10):297-302
A transitional cell carcinoma of the urinary bladder was found in a beluga whale stranded in the St. Lawrence middle estuary. Various organs of this animal were submitted to high resolution gas chromatography coupled with mass spectrometry analysis. High frequency of urinary bladder cancer in the human population of the same area and the presence of carcinogenic compounds in the marine environment of this animal are discussed.
Concurrent isolation of Edwardsiella tarda from various organs of this whale is also reported.
相似文献15.
Wolf J Vítek M Herrendörfer G Sumpf D 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》1994,111(1-6):209-212
SUMMARY: Correct equations are given to express the parameter estimates of four models for complete diallels as a function of the parameter estimates in the model of Eisen et al. (1983). In recent literature these equations have been partly incorrect. ZUSAMMENFASSUNG: Korrekte Gleichungen für den Vergleich von Modellen in der Diallelanalyse Für die Darstellung der Parametersch?tzwerte von vier Modellen für vollst?ndige Diallele als Funktion der Parametersch?tzwerte des Modells von Eisen et al. (1983), die in der Literatur teilweise fehlerhaft erfolgte, werden korrekte Formeln angegeben. 相似文献
16.
Summary On two occasions an anaplasm was isolated from sheep on the Dutch island of Ameland. The organism proved to be highly pathogenic for splenectomised sheep; a non-splenectomised animal recovered spontaneously after the packed cell volume had decreased by 40%. Treatment with oxytetracycline was effective. Its pathogenicity for goats appeared to be low, and the organism was apparently not infective to splenectomised cattle. This anaplasm differs from Anaplasma ovis in that less than 30% of the organisms are marginally situated in the red cell, as against over 70% in A. ovis; cross-immunity with A. ovis was incomplete and the latter appeared to be far more pathogenic to goats than the Dutch anaplasm, for which the name Anaplasma mesaeterum sp.n. is proposed. Its ultrastructure is similar to that of A. marginale and A. ovis. The vector is either Ixodes ricinus or Haemaphysalis punctata. Its practical importance remains to be ascertained. 相似文献
17.
Corné M. J. Pieterse Pierre J. G. M. de Wit Francine P. M. Govers 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(Z2):85-92
The fungal pathogenPhytophthora infestans is the causal organism of late blight, one of the most devastating diseases of potato. In the past, various aspects of the potato-P. infestans interaction have been studied extensively. In this paper we briefly review the current knowledge of the molecular events associated with the interaction and in addition we discuss a new approach for analyzing the molecular basis of pathogenicity ofP. infestans. 相似文献
18.
19.
Bacillary rickettsia-like organisms (BRLO) were found in the tick Dermacentor marginatus. They are gram-negative and differ from common bacteria and reckettsiae both in the cultivation conditions and morphology. BRLO are non-pathogenic for ticks and guinea pigs. In our studies they were isolated on half-engorged females of D. marginatus, on which they are still maintained. 相似文献
20.
J Marcaník J Kocisová K Bod'a T Pauer M Belák R Skarda 《Archives of Animal Nutrition》1976,26(11):757-763
Histological and histochemical studies were carried out on the gastro-intestinal mucosa of three experimental cows (roughages/maize silage) and three control animals. The animals were slaughtered on termination of the long-term trial. Mucosa samples were taken, for further study, from the rumen, the duodenum, the jejunum, the large intestine and the appendix. Histochemical analysis did not reveal any essential differences in the activities of non-specific esterase, alkaline and acid phosphatase and lactic acid dehydrogenase in the mucosa of the rumen, the large and the small intestine and the appendix of both the experimental animals and the controls. The experimental animals were found to exhibit a higher rate of glutamate-dehydrogenase activity in the ruminal mucosa and in the mucosa of the large and small intestine. A higher succinate dehydrogenase activity was observed in the ruminal mucosa of the experimental animals, relative to that of the controls, while the activity in the intestinal mucosa was decreased. Only slight changes were noted in the activity of the enzymatic systems tested. Electron microscopic studies did not reveal any differences in the ultrastructure of the epithelial cells of the ruminal mucosa in both the experimental animal and the controls. 相似文献