全文获取类型
收费全文 | 66228篇 |
免费 | 2919篇 |
国内免费 | 6419篇 |
专业分类
林业 | 7483篇 |
农学 | 9498篇 |
基础科学 | 5523篇 |
10474篇 | |
综合类 | 18024篇 |
农作物 | 3485篇 |
水产渔业 | 2658篇 |
畜牧兽医 | 11677篇 |
园艺 | 2284篇 |
植物保护 | 4460篇 |
出版年
2024年 | 168篇 |
2023年 | 598篇 |
2022年 | 1677篇 |
2021年 | 2454篇 |
2020年 | 2151篇 |
2019年 | 2213篇 |
2018年 | 1585篇 |
2017年 | 2268篇 |
2016年 | 2181篇 |
2015年 | 2964篇 |
2014年 | 2811篇 |
2013年 | 3315篇 |
2012年 | 4226篇 |
2011年 | 4390篇 |
2010年 | 3916篇 |
2009年 | 3582篇 |
2008年 | 3342篇 |
2007年 | 3242篇 |
2006年 | 3135篇 |
2005年 | 3730篇 |
2004年 | 2003篇 |
2003年 | 1601篇 |
2002年 | 1144篇 |
2001年 | 1165篇 |
2000年 | 1250篇 |
1999年 | 1655篇 |
1998年 | 1339篇 |
1997年 | 1119篇 |
1996年 | 1055篇 |
1995年 | 969篇 |
1994年 | 981篇 |
1993年 | 853篇 |
1992年 | 916篇 |
1991年 | 791篇 |
1990年 | 724篇 |
1989年 | 592篇 |
1988年 | 472篇 |
1987年 | 322篇 |
1986年 | 250篇 |
1985年 | 195篇 |
1984年 | 146篇 |
1983年 | 120篇 |
1979年 | 148篇 |
1975年 | 139篇 |
1974年 | 135篇 |
1973年 | 119篇 |
1972年 | 141篇 |
1971年 | 121篇 |
1968年 | 119篇 |
1967年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
41.
论城中村农民的现代化改造 总被引:4,自引:0,他引:4
针对当前我国城中村改造中存在的一些问题,以系统论为基础,对城中村改造工作的方向和改造工作应遵循的基本原则予以一定的分析,提出城中村改造工作的重点和关键所在是对城中村农民的现代化改造。进一步阐述了城中村农民的现代化改造对于推进城中村改造的重要意义。 相似文献
42.
43.
通过对豫南小麦当家品种鄂恩一号和种植多年的7023的对比观察,找出二者在生育规律上的差异,进而分析在栽培措施上的异同。与7023相比,鄂恩一号出叶速度快,容易形成壮苗;抽穗后绿叶保持时间较长,有利后期光合作用;年前分蘖数比例大,总分蘖及成穗数没有7023多;幼穗分化开始早,进程快,小穗数及穗粒数比较少;开花早,灌浆时间长,灌浆强度大,子粒大,千粒重高。基于这些特点,提出了十月下旬播种,三叶期、药隔形成期追肥,四分子期根外喷肥,加强后期管理等针对该品种特性的栽培措施。 相似文献
44.
M D Pérez Alenza E Tabanera L Pe?a 《Journal of the American Veterinary Medical Association》2001,219(8):1110-1114
OBJECTIVE: To determine epidemiologic, clinical, and pathologic characteristics of inflammatory mammary carcinoma (IC) in dogs. DESIGN: Retrospective study. ANIMALS: 33 dogs with IC and 153 dogs with malignant mammary tumors other than IC. PROCEDURES: Medical records were reviewed, and signalment, history, physical examination findings, and results of thoracic radiography and necropsy were obtained. RESULTS: 33 of 436 (7.6%) dogs examined at a veterinary teaching hospital because of dysplasia or tumors of the mammary glands and 33 of 186 (17.7%) dogs with at least 1 malignant tumor had IC. Thirty-two of the 33 dogs were sexually intact. Dogs with IC were significantly older than were dogs with other malignant mammary tumors, and in dogs with IC, the tumor was initially noticed a mean of 52 days after the beginning of the last observed estrus, whereas in dogs with other mammary tumors, the tumor was initially noticed a mean of 137 days after the beginning of the last observed estrus. Dogs with IC were more likely to be anorectic and to have generalized weakness, weight loss, and thoracic metastases. Dogs with IC survived a mean of 25 days with palliative treatment. Histologically, involvement of dermal lymphatic vessels was identified in 14 of 19 (74%) dogs with IC. Two clinical forms of IC (primary and secondary) were identified. Dogs with primary IC had a worse clinical condition. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that IC is an uncommon but distinct entity in dogs. A histologic finding of dermal lymphatic involvement should be considered a hallmark for the pathologic diagnosis of IC in dogs. 相似文献
45.
46.
47.
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
48.
阔叶红松林的生物量和营养元素含量的研究 总被引:6,自引:0,他引:6
一、研究内容和方法我们于1985—1987年对小兴安岭阔叶红松林的生物量进行了研究。生物量的测定是在凉水自然保护区的阔叶红松林内进行的。林龄220年,组成8红2椴,林分平均高23.1m,平均直径37.4cm。其中红松平均高27.2m,平均直径45.2cm,密度622株/ha,针 相似文献
49.
50.
在历史上,我国一直实行家庭养老方式,新中国成立以后,我国建立了城乡二元的养老保障制度,改革开放后又强化了这一制度;城乡二元养老保障制度产生的后果十分严重,它的存在导致我国城乡差距进一步扩大,许多农村老人晚境凄惨,国民经济的持续稳定发展也受到了严重影响。 相似文献