全文获取类型
收费全文 | 1723篇 |
免费 | 107篇 |
国内免费 | 1篇 |
专业分类
林业 | 119篇 |
农学 | 63篇 |
基础科学 | 12篇 |
241篇 | |
综合类 | 283篇 |
农作物 | 64篇 |
水产渔业 | 221篇 |
畜牧兽医 | 646篇 |
园艺 | 59篇 |
植物保护 | 123篇 |
出版年
2023年 | 16篇 |
2022年 | 12篇 |
2021年 | 39篇 |
2020年 | 54篇 |
2019年 | 50篇 |
2018年 | 60篇 |
2017年 | 53篇 |
2016年 | 41篇 |
2015年 | 41篇 |
2014年 | 58篇 |
2013年 | 76篇 |
2012年 | 106篇 |
2011年 | 139篇 |
2010年 | 72篇 |
2009年 | 58篇 |
2008年 | 106篇 |
2007年 | 101篇 |
2006年 | 96篇 |
2005年 | 98篇 |
2004年 | 105篇 |
2003年 | 107篇 |
2002年 | 81篇 |
2001年 | 22篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 7篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1973年 | 10篇 |
排序方式: 共有1831条查询结果,搜索用时 10 毫秒
1.
The study reports farmers' attitudes andperceptions towards the ``barriers' and ``benefits' of automaticirrigation systems. Factor analysis was used to identify perceived ``barriers' and ``benefits' andthe impact of these on farmers' priority to adopt automation wasexamined. Results suggest that farmers'attitudes, particularly with respect to ``cost' and``lifestyle' influenced the priority given to adopting automaticirrigation systems. The area under pasturecultivation was also an importantdeterminant in the farmers' priority foradopting automatic irrigation systems. 相似文献
2.
Sidaway BK McLaughlin RM Elder SH Boyle CR Silverman EB 《American journal of veterinary research》2004,65(9):1216-1222
OBJECTIVE: To objectively evaluate the effect of transecting the tendon of the biceps brachii muscle (BBT), tendon of the infraspinatus muscle (IFS), or medial glenohumeral ligament (MGHL) on shoulder joint stability in canine cadavers. SAMPLE POPULATION: 81 forelimbs from mature dogs. PROCEDURE: Cadaver forelimbs were placed in a testing frame and axially preloaded with 4 kg of weight. Shoulder joint stability was tested in neutral joint position, flexion, and extension before and after transection of the BBT (n = 37), IFS (37), or MGHL (7). Humeral translation relative to the glenoid was induced by applying a 3-kg load in each of 3 directions (cranial, lateral, and medial) and quantitatively measured by use of an electromagnetic motion tracking system. Peak translational data were compared in each joint position before and after transection of the BBT, IFS, or MGHL. RESULTS: When tested in neutral position, the cranial, lateral, and medial translation of the humerus was significantly increased after BBT transection. In the flexed position, translation of the humerus in the cranial and lateral directions was significantly increased after BBT transection. In the extended position, the medial translation of the humerus was significantly increased after BBT transection. Complete medial luxation of all humeral heads occurred following transection of the MGHL. CONCLUSIONS AND CLINICAL RELEVANCE: The BBT contributes to passive shoulder joint stability in dogs, particularly in the neutral and flexed positions. It also provides medial stability during shoulder joint extension. Complete luxation of the joint occurs when the MGHL is transected. 相似文献
3.
关于饲料中的抗氧化剂 总被引:1,自引:0,他引:1
如今 ,许多饲料产品都以其抗氧化剂含量来促销。这样做的理由是 ,据说猪吃下抗氧化剂可保持自身健康 ,尤其是在猪遭受应激的时候 ,或者是猪面临疾病侵害的时候。因此 ,养猪者不禁要问 :这些抗氧化剂究竟是什么东西呢 ?吃这些东西怎么会有好处呢 ?这要从现代猪的代谢说起。现代猪在从活重30千克生长到 110千克期间 ,会以每天 340~ 4 5 0千克的速度合成瘦肉组织。为此 ,猪要通过大量的各种代谢过程将养分转化为机体物质。要平衡蛋白质的合成和分解 ,就需要高水平的代谢活动。代谢活动的水平在幼猪极高 ,例如 :体重 15千克的猪每2 8天就将心… 相似文献
4.
Progesterone receptors in feline mammary adenocarcinomas 总被引:1,自引:0,他引:1
S D Johnston D W Hayden D T Kiang B Handschin K H Johnson 《American journal of veterinary research》1984,45(2):379-382
Estradiol and progesterone receptors were measured in tumor cytosols from 3 intact and 4 neutered female cats with spontaneously occurring mammary adenocarcinomas. Serum from 2 of the intact cats which had been in estrus 4 and 4 to 6 weeks before tumor excision contained progesterone concentrations of 16.2 and 2.2 ng/ml, respectively; serum progesterone in the other cats was less than 2 ng/ml. Estradiol receptors were not detected in any cytosols. Progesterone receptors were detected in all of the cytosols, in concentrations ranging from 4.0 to 11.7 (mean = 7.2) fmol/mg of protein. Scatchard plot analysis of tumor cytosol from an 8th cat with mammary adenocarcinoma revealed presence of high affinity progesterone binding with a dissociation constant (Kd) of 3.47 nM. Tumor receptor content could not be correlated with stage of the estrous cycle nor with whether the cat was intact or neutered. 相似文献
5.
6.
Julia H Wilson Erik J Olson Edward W Haugen Luanne M Hunt Jennifer L Johnson David W Hayden 《Journal of veterinary diagnostic investigation》2006,18(6):615-619
Progressive multisystemic disease caused by Blastomyces dermatitidis was diagnosed in a 17-year-old Quarter horse broodmare. The mare had been treated unsuccessfully with antibiotics for mastitis 3 months postpartum. The disease progressed to exudative cutaneous lesions affecting the ventrum, pectoral region, and limbs accompanied by weight loss across several months. Yeast bodies were observed in swabs of the cutaneous exudate, suggesting a clinical diagnosis of blastomycosis. Following referral, pleural effusion, cavitated lung lesions, and hyperproteinemia were identified, and the mare was euthanized because of poor prognosis. Necropsy revealed extensive pyogranulomas in the mammary gland, skin, subcutaneous tissues, and lungs, accompanied by thrombi in major blood vessels of the lungs and hind limbs. Histologically, pyogranulomatous inflammation was evident in many tissues, and fungal organisms were seen in sections of mammary gland, skin, subcutis, pericardium, and lung. Blastomyces dermatitidis was cultured from mammary tissue, lungs, lymph node, and an inguinal abscess. Although blastomycosis is endemic in the area of origin of the mare in northwestern Wisconsin, the disease is extremely rare in horses and hence easily misdiagnosed. Unique features of this case included the extent of mammary gland involvement and the presence of thrombi in multiple sites. 相似文献
7.
8.
Skeletal muscle protein degradation, measured by urinary N tau-methylhistidine excretion, and circulating concentrations of growth hormone (GH), insulin (INS), and cortisol (CT) were monitored in steers before and after implantation with estradiol-17 beta (E2; 24 mg) and trenbolone acetate (TBA; 300 mg). Yearling crossbred steers (n = 43) were randomly assigned to four treatment groups in a 2 x 2 factorial arrangement: nonimplanted controls (C); TBA; E2; and TBA plus E2 (TBA+E2). A subgroup (Block 1) of 16 steers was bled on d -12, 31, and 72 after implanting. Deposition of skeletal muscle protein was markedly increased (P less than .001) by E2 and TBA+E2 treatment. This response occurred mainly within the first 40 d after implantation and declined (P less than .001) in concert with decreasing (P less than .01) concentration of serum E2. Anabolic steroid treatment did not affect the rate of skeletal muscle protein breakdown. There was no apparent relationship between reduced serum CT concentration (linear effect; P less than .01) in TBA-treated steers and skeletal muscle protein degradation rate. Blood concentration and pulse activity of INS were not affected by anabolic steroid administration. Both TBA- and TBA+E2-implanted steers displayed a linear decrease (P less than .05) in serum GH concentration over time, which was similar to C. Lowered mean GH concentration resulted from a reduction (TBA main effect; P less than .05) in pulse amplitude of GH. Unlike TBA, TBA+E2, and C, only E2 maintained serum GH concentrations over time. Although increased muscle protein deposition was evident in TBA+E2-treated steers, an obvious causal relationship between this response and circulating GH, INS, and CT was not revealed. These results do not support the concept that combined androgenic agent and estrogen administration effectively reduce bovine muscle protein degradation by static modulation of circulating endogenous anabolic and antianabolic hormones. 相似文献
9.
10.
Nadia Shihab Brian A. Summers Livia Benigni Andrew W. McEvoy Holger A. Volk 《Veterinary radiology & ultrasound》2013,54(3):278-282
A 3‐year‐old Labrador retriever was presented with acute onset seizures. Magnetic resonance imaging demonstrated an intra‐axial mass affecting the right temporal lobe of the brain. Surgical resection and histopathological findings were most consistent with a malignant peripheral nerve sheath tumor. After initial recovery, deterioration 3 months post surgery prompted euthanasia. Post‐mortem revealed a mass protruding from the ventral surface of the temporal lobe, encroaching upon the optic chiasm and invading the brain. Histopathology findings were again consistent with malignant peripheral nerve sheath tumor. Although rare, this tumor should be included as a possible differential diagnosis for intra‐axial brain masses in dogs. 相似文献