全文获取类型
收费全文 | 108810篇 |
免费 | 6529篇 |
国内免费 | 2623篇 |
专业分类
林业 | 5677篇 |
农学 | 3581篇 |
基础科学 | 1673篇 |
12866篇 | |
综合类 | 27343篇 |
农作物 | 4928篇 |
水产渔业 | 4890篇 |
畜牧兽医 | 48060篇 |
园艺 | 2810篇 |
植物保护 | 6134篇 |
出版年
2023年 | 740篇 |
2022年 | 1426篇 |
2021年 | 1699篇 |
2020年 | 1728篇 |
2019年 | 1867篇 |
2018年 | 2060篇 |
2017年 | 2633篇 |
2016年 | 2207篇 |
2015年 | 2409篇 |
2014年 | 2743篇 |
2013年 | 4551篇 |
2012年 | 4790篇 |
2011年 | 5421篇 |
2010年 | 4061篇 |
2009年 | 3764篇 |
2008年 | 4751篇 |
2007年 | 4586篇 |
2006年 | 4158篇 |
2005年 | 3732篇 |
2004年 | 3113篇 |
2003年 | 2896篇 |
2002年 | 2737篇 |
2001年 | 2993篇 |
2000年 | 3003篇 |
1999年 | 2160篇 |
1998年 | 833篇 |
1997年 | 731篇 |
1995年 | 779篇 |
1992年 | 1604篇 |
1991年 | 1803篇 |
1990年 | 1748篇 |
1989年 | 1711篇 |
1988年 | 1573篇 |
1987年 | 1611篇 |
1986年 | 1657篇 |
1985年 | 1475篇 |
1984年 | 1266篇 |
1983年 | 1081篇 |
1979年 | 1145篇 |
1978年 | 892篇 |
1977年 | 730篇 |
1976年 | 757篇 |
1975年 | 798篇 |
1974年 | 1067篇 |
1973年 | 1068篇 |
1972年 | 1011篇 |
1971年 | 944篇 |
1970年 | 918篇 |
1969年 | 875篇 |
1967年 | 757篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
M Steinhardt S Reimer U Bünger J Kutschke 《Archiv fuer experimentelle veterinaermedizin》1989,43(2):309-314
Comprehensive studies into domestic pigs and wild boars together with literature data provided a basis for an assessment of aerobic metabolic capacity (VO2max) of swine. The values quoted, from 20 to 94 ml/min-1/kg, had been due to several factors of methodological approach, growth, training, and nutrition as well as to pathophysiological aspects. For full capacity utilisation of VO2max, untrained pigs can be challenged at belt velocities between 0.8 and 1.8 m/s-1 and trained animals at 5 m/s-1. 相似文献
2.
3.
The isolation of (+)-totarol as active compound against Mycobacterium tuberculosis is reported from Chamaecyparis nootkatensis outerbark. 相似文献
4.
The morphology of 16–17 days old embryos from virgin heifers (VH) and repeat breeder heifers (RBH) was compared using light and electron microscopy. In addition some embryos transferred from one heifer category to the other were studied. Embryos from VH were elongated blastocysts and the oval embryonic disc had three germ layers. The ectoderm was stratified and many mitoses were seen. The endoderm lining the blastocoelic cavity consisted of almost squamous cells conjoined by tight junctions. Between the ectoderm and the endoderm the mesoderm had developed and expanded laterally and the coelom had formed. The trophoblastic cells adjacent do the embryonic disc were cylindrical, whereas those more peripheral located were cuboidal. The trophoblastic cells were conjoined by tight junctions and they had numerous long microvilli on their peripheral surface. Except in the embryonic disc region, the endodermal cells had filopodial processes towards the trophoblast. The embryos from RBH varied in appearance. One was similar to those from VH whereas the others were, more or less retarded, without formation of mesoderm. The smaller one consisted ot trophoblastic cells only. The transferred embryos (representing surviving embryos: 2 out of 9 in VH-RBH and 5 of 6 in RBH-VH) had a morphology similar to that of VH blastocytes two though, appeared somewhat retarded. It is suggested that the retarded embryos lack the ability to complete embryonic development and that the uterine environment of RBH is not favourable to sustain normal embryonic development. 相似文献
5.
A. Bhogal A. Bhogal M.A. Shepherd D.J. Hatch L. Brown S.C. Jarvis 《Soil Use and Management》2001,17(3):163-172
Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization. 相似文献
6.
W W Chan K Y Chen H Liu L S Wu J H Lin 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(10):1057-1062
Since the International Society of Veterinary Acupuncture (IVAS) was founded in 1974, acupuncture (AP) has received greater acceptance by veterinary professionals throughout the world. This article introduces some important animal diseases that respond well to AP therapy. These include resuscitation of small animals, treatment of anoestrous gilts and sows, bovine reproductive disease, canine vertebral problems and equine backpain, etc. Conventional medicine considers these to be difficult cases to treat. Veterinarians have become more aware of the benefits of AP especially for those diseases, thanks to the efforts of experienced practitioners and scientists, and the many published reports on veterinary AP that have introduced some good indications for AP therapy in veterinary practice. Possible mechanisms behind the effectiveness of AP are discussed. This article aims to introduce veterinarians to good indications for AP to initiate their interest in the practice of AP. Although this is a rapidly expanding field, a long march must begin with one step. We wish this article to be the shoes for such a march. For more information on veterinary AP, contact IVAS , P.O. Box 1478, Longmont, CO.. 80502, USA (http://www.ivas.org), or your national veterinary acupuncture society (http://www.komvet.at/ ivadkom/vapsocs.htm). 相似文献
7.
8.
9.
我国猪囊虫病的研究概况 总被引:2,自引:0,他引:2
囊虫病是一种危害严重的人兽共患病,在我国的发生率较高。近年来,我国学者在该病的流行病学、诊断方法、防制措施以及免疫预防等方面都进行了深入研究,本文就该病的研究进展进行了综述。 相似文献
10.