全文获取类型
收费全文 | 62535篇 |
免费 | 2834篇 |
国内免费 | 42篇 |
专业分类
林业 | 2516篇 |
农学 | 1645篇 |
基础科学 | 429篇 |
6150篇 | |
综合类 | 14758篇 |
农作物 | 2461篇 |
水产渔业 | 2346篇 |
畜牧兽医 | 31047篇 |
园艺 | 643篇 |
植物保护 | 3416篇 |
出版年
2017年 | 553篇 |
2016年 | 536篇 |
2014年 | 540篇 |
2013年 | 1863篇 |
2012年 | 1202篇 |
2011年 | 1436篇 |
2010年 | 913篇 |
2009年 | 877篇 |
2008年 | 1427篇 |
2007年 | 1389篇 |
2006年 | 1371篇 |
2005年 | 1386篇 |
2004年 | 1318篇 |
2003年 | 1391篇 |
2002年 | 1354篇 |
2001年 | 1493篇 |
2000年 | 1473篇 |
1999年 | 1206篇 |
1998年 | 531篇 |
1997年 | 538篇 |
1995年 | 596篇 |
1994年 | 573篇 |
1993年 | 561篇 |
1992年 | 1309篇 |
1991年 | 1395篇 |
1990年 | 1449篇 |
1989年 | 1488篇 |
1988年 | 1399篇 |
1987年 | 1356篇 |
1986年 | 1400篇 |
1985年 | 1373篇 |
1984年 | 1150篇 |
1983年 | 1005篇 |
1982年 | 718篇 |
1981年 | 688篇 |
1980年 | 644篇 |
1979年 | 1127篇 |
1978年 | 916篇 |
1977年 | 819篇 |
1976年 | 768篇 |
1975年 | 860篇 |
1974年 | 1126篇 |
1973年 | 1063篇 |
1972年 | 1128篇 |
1971年 | 1080篇 |
1970年 | 1022篇 |
1969年 | 874篇 |
1968年 | 710篇 |
1967年 | 844篇 |
1966年 | 693篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
Anatomical structures of shoulder joints of five adult cheetahs were examined by dissection, corrosion casts and radiography. The bones, capsules and auxiliary synovial devices were described, as well as ligaments and adjacent muscles. The cheetah shoulder has many similarities with the shoulder joint of the domestic cat, but also considerable differences. Proper osteological features were the large supraglenoid tubercle, the caudally directed coracoid process and the extension of the articular surface of the scapula to the lateral area of the supraglenoid tubercle. On the proximal end of the humerus the width of the head of humerus, the facet of infraspinatus muscle as a shallow cavity with the insertion of the infraspinatus muscle around it and two raised roughnesses on the proximal end of the tricipital line for the insertions of the lateral glenohumeral ligament and the teres minor muscle were noticeable. The insertion of the joint capsule was mainly on the glenoid labrum, only in part of the articular surface on the lateral area of the supraglenoid tubercle laterally on the scapula. The joint capsule formed a supra- and infraspinatus recess laterally, an intertubercular tendon sheet for the biceps brachii muscle cranially, and a bipartited subscapular recess medially. An extracapsular transverse ligament passing the intertubercular groove, a laterally capsular strengthening—called lateral glenohumeral ligament—and an intracapsular medial glenohumeral ligament could be found. The latter one was joined to the capsule by a mesoligament, dividing the subscapular recess into two pouches. 相似文献
982.
J. Kimura I. Habata H. Endo W. Rerkamnuaychoke M. Kurohmaru J. Yamada T. Nishida A. Tsukise 《Anatomia, histologia, embryologia》1998,27(3):147-153
The major salivary glands (parotid glands, monostomatic sublingual glands and submandibular glands) were obtained from hoary bamboo rats (Rhizomys purinosus) and fixed in Bouin's solution. Paraffin sections were subjected to a battery of staining methods including lectin staining for demonstration of complex carbohydrates. Among the three major salivary glands, unique histochemical features were observed in the submandibular gland. Different from most myomorpha species, submandibular glands of the hoary bamboo rats have two types of secretory cells in the secretory endpieces. One type of cells showed positive reactions with Alcian blue (AB)(pH2.5), periodic acid-Schiff (PAS) and some lectins (peanuts agglutinin, Griffonia simplicifolia I. Machura pomifera agglutinin). The granular ducts, which exist in animals belonging to suborder myomorpha, were not observed in the submandibular glands of this animal. 相似文献
983.
Deborah S. Greco Rod A.W. Rosychuk Gregory K. Ogilvie Lynn M. Harpold Camilla H. Van Liew 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(1):7-10
Thirty adult, client-owned dogs were diagnosed with hypothyroidism based on history, physical examination findings, hematologic and biochemical abnormalities, thyrotropin (TSH) response testing, endogenous canine thyrotropin (cTSH) concentration, or both, and total serum thryoxine concentration. All dogs received levothyroxine (L-thyroxine) at an initial dose of 22 μg/kg PO sid in either a tablet (13 dogs) or chewable form (17 dogs). Energy expenditure of each dog during apparent rest was estimated with an open-flow indirect calorimetry system by determining the rates of carbon dioxide production and oxygen consumption. Energy expenditure of apparent rest (EE) was lower in untreated hypothyroid dogs compared with reference values for EE. After treatment with L-thyroxine, EE of the hypothyroid dogs was significantly ( P < .05) higher than pretreatment values. 相似文献
984.
B.D. Nielsen PhD G.D. Potter PhD L.W. Greene PhD E.L. Morris DVM M. Murray-Gerzik MS W.B. Smith PhD M.T. Martin DVM 《Journal of Equine Veterinary Science》1998,18(3):190-200
This study was conducted to determine physiologic responses reflective of bone metabolism during the onset of training and to relate those responses to the mineral requirements of young racehorses. Ten previously untrained Quarter Horse geldings were put into race training. They were fed a diet balanced to meet NRC recommendations for young horses in training. Feed, feces and urine were collected, weighed and analyzed over the experiment to determine mineral balance. Radiographs were taken of the left front leg to determine mineral content of a cross-sectional area of the third metacarpal. Blood samples were taken to determine osteocalcin, parathyroid hormone, 25-hydroxyvitamin D, Ca and inorganic P concentrations. Horses were gentled to ride, trained to gallop on the track and maintained in training for four 28-day periods. Blood serum was collected every 14 day, while radiographs and 72-hr total collections of urine and feces were taken every 28 d. Radiographs demonstrated that mineral content was lowest at day 56 in the dorsal, palmar and medial cortices of the third metacarpal. Urinary Ca declined dramatically from day 0 to day 28, then remained constant to day 56, before decreasing at day 84. Fecal Ca peaked at day 28 and remained elevated above day 0 amounts until day 112. calcium retention was negative at day 0, became slightly positive by day 28 and increased through day 112. Phosphorus and Mg balance remained relatively unchanged throughout the duration of the study. This study demon-strated changes in the mineral content of the third metacarpal and Ca balance during early training and suggests that further studies be performed. 相似文献
985.
van Leengoed L Kluivers M Herbes R Langendijk P Stephany R van den Berg M Seinen W Grinwis G van der Lugt J Meulders F Geudeke T Verheijden J 《Tijdschrift voor diergeneeskunde》2002,127(17):516-519
Medroxyprogesterone acetate (MPA)-contaminated feed arrested the onset of farrowing, and induced post-lactational anoestrus in sows. Sixty percent of the sows developed cystic ovaries after weaning following exposure to pharmaceutical waste of MPA in glucose syrup. This waste ended up in acidified feed of by-products of a sow farm, and proved to be the cause of the disorders. Analysis by thin layer chromatography and Gas Chromatography/Mass Spectrometry of renal fat from 10 slaughter sows demonstrated residues of 2.5-8 ppb of MPA. Within the European Union use of MPA is illegal as growth promoter in production animals, and therefore MPA-exposed farms were placed under official control by the general inspection service. Clinical signs and diagnostic procedures of the initial case are presented and the role of the veterinary practitioner in detecting potential food safety hazards is discussed. 相似文献
986.
987.
Kaaden OR Eichhorn W Essbauer S 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2002,49(1):3-6
There is continual variation in viral epidemics regarding clinical symptoms, duration and disappearance, and the emergence of new diseases. This can be observed in both human and animal diseases. This evolution of virus diseases is mainly related to three factors: aetiological agent, host and environment. As far as genetic alterations of the virus are concerned, two major mechanisms are involved: mutations such as recombination and reassortment; and selection for resistance or susceptibility. This review focuses on the epidemiology of newly emerged virus diseases in man and animals, such as acquired immunodeficiency syndrome, haemorraghic fevers, bovine spongiform encephalopathy, canine haemorraghic disease and respiratory syndrome in horses. 相似文献
988.
Evaluation of the complement fixation test for the diagnosis of pleuropneumonia of swine caused by Haemophilus pleuropneumoniae. 总被引:4,自引:6,他引:4 下载免费PDF全文
Evaluation of diagnostic sensitivity and specificity was based on test results of 346 sera from pigs known to be infected and 139 sera from pigs known not to be infected. All sera were tested with a monospecific antigen (serotype 1) and a polyspecific antigen (serotypes 1-5). The sensitivity of the polyspecific antigen was approximately 85% at serum dilution 1:2 and was significantly higher than the monospecific antigen at all serum dilution levels. The specificity of the two antigen preparations was not significantly different at any dilution and increased from approximately 78% to 1:2 to 100% at 1:128. When pigs from herds with unknown incidence of infection were studied, it was found that a high proportion seroconverted, presumably as a response to subclinical infection. However, the antibody titres waned rapidly. This indicated that seroreaction expresses current or recent infection. Thus, the complement fixation test provides a reliable means of diagnosing pleuropneumonia of pigs and might be useful as a tool to control this disease. 相似文献
989.
Effect of injecting amino acids into the egg on embryonic and subsequent growth in the domestic fowl
W. K. Al‐Murrani 《British poultry science》1982,23(2):171-174
1. The growing embryo uses about 1% of the total protein available in the egg during the first week of incubation.
2. Injecting the growing embryo with amino acids equivalent to the amount of protein used resulted in higher weight of chicks at all stages up to 56 d. 相似文献
990.
Serum from most sheep subjected to a single jugular bleeding, repeated bleeding or an intraperitoneal injection of yeast and repeated bleeding, showed an increase in the titre of a serum component called serum factor. Serum factor reached a peak titre 2 to 5 days after treatment started. For some sheep, the titre was elevated for a 9- to 12-day period whereas for others the titre dropped markedly on day 7 followed by a rise on day 9. Serum factor reacts with sheep erythrocytes sensitised with rabbit antibody (sheep E-rabbit A). Serum factor can be detected on sheep E-rabbit A using guinea-pig antiserum that reacts with sheep complement (C). Serum factor is inactivated by heating at 56 degrees C for 30 minutes, but is only partially inactivated at 50 degrees C for 30 minutes. The reaction of serum factor with sheep E-rabbit A is inhibited by chelators of Ca++ and/or Mg++. Serum factor appears to be related to the sheep C system. Preliminary results suggest it may he a component of the classical pathway of sheep C, possibly the second component, C2. 相似文献