全文获取类型
收费全文 | 123179篇 |
免费 | 6045篇 |
国内免费 | 7285篇 |
专业分类
林业 | 10229篇 |
农学 | 12820篇 |
基础科学 | 6301篇 |
17590篇 | |
综合类 | 28119篇 |
农作物 | 5199篇 |
水产渔业 | 4671篇 |
畜牧兽医 | 40842篇 |
园艺 | 2756篇 |
植物保护 | 7982篇 |
出版年
2022年 | 1794篇 |
2021年 | 2795篇 |
2020年 | 2657篇 |
2019年 | 2594篇 |
2018年 | 2414篇 |
2017年 | 3078篇 |
2016年 | 2958篇 |
2015年 | 3514篇 |
2014年 | 3437篇 |
2013年 | 5853篇 |
2012年 | 5527篇 |
2011年 | 6167篇 |
2010年 | 5242篇 |
2009年 | 4869篇 |
2008年 | 5289篇 |
2007年 | 5691篇 |
2006年 | 5300篇 |
2005年 | 4854篇 |
2004年 | 3026篇 |
2003年 | 2835篇 |
2002年 | 2483篇 |
2001年 | 2933篇 |
2000年 | 3243篇 |
1999年 | 3194篇 |
1998年 | 2290篇 |
1997年 | 2013篇 |
1996年 | 1843篇 |
1995年 | 1874篇 |
1994年 | 1684篇 |
1993年 | 1595篇 |
1992年 | 2069篇 |
1991年 | 2033篇 |
1990年 | 1848篇 |
1989年 | 1679篇 |
1988年 | 1516篇 |
1987年 | 1386篇 |
1986年 | 1323篇 |
1985年 | 1251篇 |
1984年 | 1010篇 |
1983年 | 952篇 |
1979年 | 902篇 |
1978年 | 701篇 |
1976年 | 711篇 |
1975年 | 714篇 |
1974年 | 866篇 |
1973年 | 842篇 |
1972年 | 812篇 |
1971年 | 727篇 |
1970年 | 769篇 |
1969年 | 733篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
L S Pelan-Mattocks B A Pesch M E Kehrli 《American journal of veterinary research》2001,62(11):1740-1744
OBJECTIVE: To develop an efficient and reliable method that accurately differentiates bovine lymphocytes from monocytes in leukograms. SAMPLE POPULATION: Blood samples from 30 healthy cows and 1 calf with bovine leukocyte adhesion deficiency. PROCEDURE: Flow cytometric analysis of intracellular complexity and CD45 expression on bovine leukocytes was compared with results for conventional light microscopy methods. Verification of leukocyte subpopulations determined by intracellular complexity and CD45 expression was conducted, using 2-color phenotypic analysis with selected monoclonal antibodies. RESULTS: The CD45 and side-scatter properties of bovine leukocytes clearly differentiated cell types, including neutrophils, eosinophils, monocytes, and lymphocytes. CONCLUSIONS AND CLINICAL RELEVANCE: This is a rapid assay that is simple to use. More importantly, it is more accurate than the conventional method that involves the use of blood slides and light microscopy, because of the ability of the assay to readily distinguish bovine monocytes and lymphocytes. Rapid preparation of samples and short analysis times allow for efficient and reliable examination of a large number of samples, and the task of viewing slides by light microscopy is eliminated. The labor-savings benefit of this procedure is most apparent in research environments that require frequent processing of batches of blood samples. 相似文献
42.
用淋巴细胞杂交瘤技术研制成4株沙门氏菌属特异单抗CB8,de7,cc6,DD4,在免疫转印试验中,证实它们所识别的抗原表位位于鞭毛蛋白上,ELISA相加试验及竞争试验显示,CB8和cc6与de7,DD4识别的抗原表位不同,表明鞭毛蛋白的属共同抗原具有多种表位的特性。用胰蛋白酶消化鞭毛蛋白,SDS-PAGE结果出现两条新带,分子量分别为42000(F42),27000(F27),长时间消化,最终只剩下F27条带,它可抵制该酶的消化。对该酶切样品的免疫转印结果表明,沙门氏菌鞭毛蛋白属共同抗原表位出现于F42和F27上,而相应的沙门氏菌分型H抗原单抗或因子血清识别的表位也在F42和F27上都得到了证实。这为沙门氏菌鞭毛蛋白抗原的多样性及结构和功能研究提供了证据。 相似文献
43.
张桂 《湖南农业大学学报(自然科学版)》1996,23(5)
讨论了一类与区域分解算法有关的空间分解问题,将二阶问题的已有的空间分解结果推广到四阶问题的相应空间中。还证明了一致重迭性条件与Badea条件的等价性。 相似文献
44.
姜瘟病是中国生姜生产上发生较为普遍的病害,是由青枯劳尔氏菌(Ralstoniasolanacearum)引起的。此病原菌寄主范围广,可侵染44个科300多种植物。菌体短杆状,在TZC选择性培养基上培养出现白边较宽和白边较窄的两种菌落。菌系划分为5个生理小种和5个生化型,中国的姜瘟菌主要属生理小种1号,生物型属II、III、IV。此病害是一种较难防治的土传病害,在高温、高湿、雨水多、氮肥过量的情况下发生较为严重。中国植病工作者对此病害作了大量的研究工作,对中国姜瘟病的病原菌、发病规律、及防治等研究进展作一综述。 相似文献
45.
张国栋 《绿色中国(综合版)》2006,(5):10-10
在美国费城,有一位名叫John Wanamaker的大老板曾说过这样一句话:“我敢肯定我花在广告上的钱,有一半是被浪费掉了。但问题是,我不知道是哪一半。” 相似文献
46.
47.
B J Hawkins 《Veterinary Clinics of North America: Small Animal Practice》1986,16(5):835-849
Success in veterinary dentistry lies in good home care and regular, thorough dental prophylaxis. The removal of supragingival and subgingival calculus must be accomplished before periodontal disease can be controlled. When gingival sulcus depths exceed 4 or 5 mm, the gingivae must be excised or reflected to allow proper treatment of the pocket area. Antibiotic therapy should be instituted in the extensively involved veterinary dental patient. 相似文献
48.
49.
50.
In New Zealand, the brushtail possum (Trichosurus vulpecula) is the principal wildlife vector of bovine tuberculosis. Control of infected possum populations contributes to the control of tuberculosis in domestic livestock. Vaccination is potentially a complementary strategy to population control, but to be cost-effective, administration of the vaccine to possums would need to be from an appropriately designed automatic vaccinator. Possums themselves would activate the vaccinator so that it would deliver an aerosol spray of vaccine. There would be no direct way to prevent possums receiving multiple doses of vaccine. This study examined the effect on protective immunity of repeated vaccination. Captive possums were vaccinated with BCG strain pasteur 1173P2 either 12 times at weekly intervals, twice at 6-weekly intervals, or once. Vaccination was by a combination of intranasal aerosol and conjunctival instillation. Eight weeks after the last dose of vaccine, all possums were challenged intratracheally with Mycobacterium bovis strain 83/6235. Vaccination induced a significant immune response as measured by the lymphocyte proliferation assay (LPA). A significant level of protection, as measured by the response to challenge, developed in all the vaccinated possum groups, but protection was greatest in the group vaccinated 12 times. It was concluded that protection would be enhanced if vaccinations were repeated at short intervals (weekly), but no benefit or detriment resulted from revaccination after longer intervals (1-2 months). 相似文献