全文获取类型
收费全文 | 151334篇 |
免费 | 8589篇 |
国内免费 | 94篇 |
专业分类
林业 | 5429篇 |
农学 | 4487篇 |
基础科学 | 987篇 |
17188篇 | |
综合类 | 28246篇 |
农作物 | 5974篇 |
水产渔业 | 7264篇 |
畜牧兽医 | 79061篇 |
园艺 | 1799篇 |
植物保护 | 9582篇 |
出版年
2018年 | 1937篇 |
2017年 | 2260篇 |
2016年 | 2066篇 |
2015年 | 1820篇 |
2014年 | 2212篇 |
2013年 | 5693篇 |
2012年 | 4099篇 |
2011年 | 5007篇 |
2010年 | 3188篇 |
2009年 | 3271篇 |
2008年 | 4814篇 |
2007年 | 4589篇 |
2006年 | 4418篇 |
2005年 | 4078篇 |
2004年 | 3922篇 |
2003年 | 3967篇 |
2002年 | 3746篇 |
2001年 | 4846篇 |
2000年 | 4797篇 |
1999年 | 3793篇 |
1998年 | 1564篇 |
1997年 | 1524篇 |
1996年 | 1415篇 |
1995年 | 1732篇 |
1994年 | 1554篇 |
1993年 | 1512篇 |
1992年 | 3239篇 |
1991年 | 3386篇 |
1990年 | 3200篇 |
1989年 | 3283篇 |
1988年 | 2998篇 |
1987年 | 3189篇 |
1986年 | 3252篇 |
1985年 | 3104篇 |
1984年 | 2485篇 |
1983年 | 2192篇 |
1982年 | 1541篇 |
1981年 | 1353篇 |
1979年 | 2207篇 |
1978年 | 1830篇 |
1977年 | 1581篇 |
1976年 | 1492篇 |
1975年 | 1605篇 |
1974年 | 2017篇 |
1973年 | 2080篇 |
1972年 | 1993篇 |
1971年 | 1870篇 |
1970年 | 1784篇 |
1969年 | 1612篇 |
1967年 | 1409篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
A D Shipp 《Journal of veterinary dentistry》1991,8(3):4-6
Crown reduction is a sterile endodontic procedure indicated for reducing the crown height of teeth. The procedure is used primarily on canine teeth as a disarming technique in aggressive biting pets or to treat traumatic occlusion. Recommendations for using this technique for biting pets are described. 相似文献
72.
C M Honnas 《Veterinary Clinics of North America: Equine Practice》1991,7(3):695-722
Several surgical conditions affecting the foot can be successfully managed with the horse standing. Many factors affect the clinician's choice of whether to perform surgery with the horse standing or anesthetized. Temperament or pregnancy of the horse and economics may influence the decision to perform surgery with the horse standing. This article discusses several foot conditions that can be treated successfully in the ambulatory horse. 相似文献
73.
For practical reasons, a large volume (i.e. 5 ml) of frozen boar semen per insemination dose is desirable, but successful freezing has not been achieved, since optimal cooling rates have not yet been established. Post-thaw motility and the acrosome intep'ty of semen from four boars frozen with a programmable freezin machine, in mini-(0.25 ml), maxi-(5 ml) plastic straws and in 10 × 5 cm PVC- or Teflon FEP-plastic bags (0.35 – 0.12 mm thick, 5 ml) was studied. The freezing of the semen was monitored using thermocouples placed in the straws and the bags. The freezing curve started from +5°C, at a rate of −3°C/min, to – 6°C, it was held for 1 min at −6°C, and was followed by further drop to −100°C at a rate of −20°C/min, with subsequent storage in LN2 . The bags had a much shorter freezing point plnteau, compared to the maxi-straws. Post-thaw sperm motility was significantly higher when semen was frozen in mini-straws or in bags than in maxi-straws. The freezing procedure did not cause major acrosomal damages, significantly more normal apical ridges being present in the bags and mini-straws than in the maxi-straws. This in vitro evaluation indicates that the freezing method employed is satisfactory for freezing large volumes of boar semen into plastic bags . 相似文献
74.
D G Powell 《Veterinary Clinics of North America: Equine Practice》1991,7(1):27-52
The diagnosis of any viral respiratory disease relies on laboratory procedures to isolate the virus and demonstrate a significant rise in serum antibody titers. To isolate viruses from the upper respiratory tract, it is imperative that nasopharyngeal swabs are obtained from animals in the early acute stage of illness, i.e., during the pyrexic phase when the virus is replicating. Nasopharyngeal swabs must be placed in a virus transport medium and forwarded immediately to the laboratory at refrigerated temperature. Equine influenza, rhinopneumonitis, and equine viral arteritis are the three viral infections causing outbreaks of respiratory disease in North America. African horse sickness, although foreign to North America, could be introduced despite stringent horse importation regulations. Specific antiviral therapy is not available to treat viral respiratory disease in the horse. A variety of inactivated and modified live vaccines, however, are available to prevent clinical disease and the spread of infection caused by the common viral respiratory pathogens. A considerable amount of research is underway to enhance the potency and duration of immunity of the present vaccines against influenza and rhinopneumonitis. This research is directed at defining and characterizing the importance of specific glycoprotein antigens on the surface of the virus, which trigger the various host immune responses, and determining whether they are stimulatory or suppressive. 相似文献
75.
Individual antigens of goats 总被引:1,自引:0,他引:1
76.
As anaerobic sampling and culture techniques improved, the documented prevalence of anaerobic bacteria in periodontal disease has increased. The anaerobic bacteria have become more well-known in humans and consequently in dogs, since this species is a major model in periodontal studies. A review of the literature related to anaerobic flora is described. 相似文献
77.
RNA was extracted from single or small groups of ovine ovarian follicles after treatment of ewes with FSH and/or LH. The content of mRNA for the alpha-inhibin and beta A-inhibin subunits was analyzed by hybridization with specific cDNA probes. All ewes were treated with progestin vaginal pessaries to suppress spontaneous preovulatory follicle maturation and ewes were given three intramuscular injections of gonadotropins at 8-hr intervals starting 24 hr prior to collection of ovaries. In experiment I, both Schering-FSH and NIDDK-oFSH-17 (oFSH) significantly increased alpha- and beta A-inhibin mRNA per ewe in 2-5 mm follicles and tended to increase alpha- and beta A-inhibin mRNA in large (greater than 5 mm) follicles. In experiment II, oFSH and NIDDK-oLH-25 (oLH) were administered in a 2X2 factorial arrangement. Separate administration of oFSH or oLH increased (P less than .05) the alpha-inhibin mRNA concentration in large follicles. alpha-inhibin mRNA concentration in 4-5 mm follicles was also increased by oFSH but was decreased by oLH. Concomitant treatment with oFSH and oLH did not change alpha-inhibin mRNA concentrations from those measured in oFSH treated ewes. In experiment II, beta A mRNA concentrations followed a pattern similar to that of alpha A mRNA, but the differences were not statistically significant. We conclude that, in the ewe, exogenous FSH increases the concentration of inhibin mRNA in the whole follicle. The ability of exogenous oLH to alter expression of the inhibin subunit genes may depend upon the stage of follicle maturation. 相似文献
78.
79.
80.