全文获取类型
收费全文 | 15227篇 |
免费 | 999篇 |
国内免费 | 250篇 |
专业分类
林业 | 1064篇 |
农学 | 811篇 |
基础科学 | 164篇 |
3478篇 | |
综合类 | 1172篇 |
农作物 | 936篇 |
水产渔业 | 1358篇 |
畜牧兽医 | 5897篇 |
园艺 | 343篇 |
植物保护 | 1253篇 |
出版年
2023年 | 99篇 |
2022年 | 169篇 |
2021年 | 311篇 |
2020年 | 304篇 |
2019年 | 331篇 |
2018年 | 503篇 |
2017年 | 557篇 |
2016年 | 552篇 |
2015年 | 436篇 |
2014年 | 545篇 |
2013年 | 886篇 |
2012年 | 985篇 |
2011年 | 1052篇 |
2010年 | 665篇 |
2009年 | 641篇 |
2008年 | 865篇 |
2007年 | 856篇 |
2006年 | 702篇 |
2005年 | 640篇 |
2004年 | 635篇 |
2003年 | 653篇 |
2002年 | 628篇 |
2001年 | 570篇 |
2000年 | 431篇 |
1999年 | 365篇 |
1998年 | 108篇 |
1997年 | 97篇 |
1996年 | 81篇 |
1995年 | 98篇 |
1994年 | 75篇 |
1993年 | 67篇 |
1992年 | 92篇 |
1991年 | 83篇 |
1990年 | 97篇 |
1989年 | 110篇 |
1988年 | 62篇 |
1987年 | 84篇 |
1986年 | 62篇 |
1985年 | 69篇 |
1984年 | 74篇 |
1983年 | 54篇 |
1982年 | 39篇 |
1979年 | 52篇 |
1978年 | 46篇 |
1977年 | 38篇 |
1976年 | 40篇 |
1974年 | 49篇 |
1973年 | 40篇 |
1972年 | 43篇 |
1971年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
G W De Lisle D M Collins H F Huchzermeyer 《The Onderstepoort journal of veterinary research》1992,59(2):163-165
Restriction endonuclease analysis and DNA hybridization revealed five ovine strains of Mycobacterium paratuberculosis from South Africa had identical DNA patterns to an ovine strain from Canada. Genetically this strain type has features in common with the two major groups of M. paratuberculosis. 相似文献
3.
Luc Van Ham Marc Vandevelde Miek Desmidt Mulenda Tshamala Luc De Schaepdrijver Daniel Mattheeuws 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(4):290-292
A central axonopathy in 2 male and 1 female Scottish Terrier puppies from 3 different but related litters is reported. Clinical signs consisting of severe whole-body tremors and ataxia were first detected at the age of 10 to 12 weeks. They worsened with activity and excitement and diminished during rest or sleep. Two dogs also had paraparesis. In 1 dog the neurological deficits progressed over several months. Neuropathological examination revealed widespread axonal changes, vacuolation, and gliosis in the white matter of the central nervous system. 相似文献
4.
B Hofírek P Horín M Granátová M Machatková J Franz I Svoboda J Blecha 《Veterinární medicína》1986,31(3):129-140
A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs. 相似文献
5.
6.
Protective activities of heat-inactivated (60 degrees C for 30 min) merthiolate preserved Bordetella bronchiseptica and B. pertussis bacterins were compared in intraperitoneally immunized mice challenged intracerebrally (i.p./i.c.) or intraperitoneally (i.p./i.p.). In the i.p./i.c. assay (Kendrick test), a B. pertussis bacterin protected mice against challenge with B. pertussis 18-323, as well as against phase I cytotoxic and non-cytotoxic strains of B. bronchiseptica. A B. bronchiseptica bacterin, prepared from a phase I cytotoxic strain, gave protection against two phase I B. bronchiseptica strains, irrespective of their cytotoxin-production. A non-cytotoxic phase I strain of B. bronchiseptica elicited protection against the homologous strain only. Neither cytotoxic nor non-cytotoxic B. bronchiseptica strains protected mice challenged with B. pertussis 18-323. Vaccines prepared from phase III strains of B. bronchiseptica were not protective at all against any of the challenge strains. No such differences in the protective activities of the bacterins could be detected by the i.p./i.p. method. They seem to cross-protect equally well. The results indicate that the Kendrick test may be useful in testing potency of different B. bronchiseptica bacterins. 相似文献
7.
A. T. Szabó 《Genetic Resources and Crop Evolution》2005,52(3):347
8.
S Cavirani C S Cabassi G Donofrio B De Iaco S Taddei C F Flammini 《Preventive veterinary medicine》2001,50(1-2):145-151
Although the seroprevalence of Chlamydia psittaci is widespread in Italian dairy herds, its role in inducing genital disorders has not been elucidated. We therefore set up a case-control study to compare seroprevalence to C. psittaci in an aborted-cow population and in a randomly selected control group in the province of Parma (the Po Valley of northern Italy). The true seroprevalence (45%) in aborted cows was significantly higher than that in the control group (24%) (adjusted odds ratio=2.53). 相似文献
9.
1962—1963年在四川省泸县地区进行油茶炭疽病的防治試驗。結果表明:采用营林措施(修除树上病部)和化学保护(噴射1∶1∶150波尔多液)的综合防治方法,病株防治效果可达89.77%,防止果病率达70.02%。严重病区,可在冬(12月)、春(2月)修除病部各一次(或可集中在2月进行),发病期間(4—8月)噴射波尔多液8—10次(条件不許可山区,也至少5次)。噴药宜連續性。上述措施,应进行2—3年。 相似文献
10.
The effects of sufficient milk intake as well as of 32 hours of fasting after birth, administration of actinomycin D (intraperitoneal application of 1 mg/kg five weight), and fasting in combination with actinomycin D on the development of body and liver weights, crude protein levels in homogenate and supernatant of liver, kidneys, and M. semitendinosus as well as on the activities of certain tissue enzymes were analysed with four groups of piglets (n = 4). Fasting, administration of actinomycin, and fasting in combination with actinomycin D resulted in rapid reduction in body and liver weights, while the crude protein levels in those tissues were not affected with significance. GOT and fructose-1,6-diphosphatase activities in supernatant from liver tended to decline under fasting conditions. The ATPase activity in the homogenate of the above tissues did not change in response to differentiated treatment. 相似文献