全文获取类型
收费全文 | 17886篇 |
免费 | 1063篇 |
国内免费 | 721篇 |
专业分类
林业 | 1701篇 |
农学 | 1477篇 |
基础科学 | 559篇 |
3518篇 | |
综合类 | 2067篇 |
农作物 | 818篇 |
水产渔业 | 1268篇 |
畜牧兽医 | 6276篇 |
园艺 | 427篇 |
植物保护 | 1559篇 |
出版年
2023年 | 178篇 |
2022年 | 280篇 |
2021年 | 509篇 |
2020年 | 463篇 |
2019年 | 400篇 |
2018年 | 646篇 |
2017年 | 787篇 |
2016年 | 765篇 |
2015年 | 676篇 |
2014年 | 748篇 |
2013年 | 1031篇 |
2012年 | 1165篇 |
2011年 | 1118篇 |
2010年 | 740篇 |
2009年 | 691篇 |
2008年 | 934篇 |
2007年 | 820篇 |
2006年 | 763篇 |
2005年 | 732篇 |
2004年 | 539篇 |
2003年 | 501篇 |
2002年 | 464篇 |
2001年 | 434篇 |
2000年 | 415篇 |
1999年 | 390篇 |
1998年 | 185篇 |
1997年 | 160篇 |
1996年 | 134篇 |
1995年 | 108篇 |
1994年 | 108篇 |
1993年 | 101篇 |
1992年 | 196篇 |
1991年 | 180篇 |
1990年 | 145篇 |
1989年 | 162篇 |
1988年 | 160篇 |
1987年 | 153篇 |
1986年 | 132篇 |
1985年 | 115篇 |
1984年 | 101篇 |
1983年 | 80篇 |
1981年 | 64篇 |
1979年 | 114篇 |
1978年 | 100篇 |
1977年 | 96篇 |
1976年 | 62篇 |
1974年 | 112篇 |
1973年 | 85篇 |
1972年 | 109篇 |
1971年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The crossreactivity of mouse monoclonal antibodies (MoAbs) (Tab. I) prepared against human HLA-DR and HLA-DP antigens was studied in various bovine cells: lymphocytes from lymph nodes and peripheral blood, adherent (B) and nonadherent (T) lymphocytes, monocytes, granulocytes and platelets. In the immunofluorescence test, MoAbs Bra13, Bra14, Bra20, Bra22, Bra30, Bra70, HL-38 reacted with bovine B lymphocytes and monocytes, but not with other tested cells (Tab. III, IV). These antibodies, except Bra22, were positive with B lymphocytes in the complement dependent cytotoxic test (Tab. II). The similarity of the bovine antigens and HLA-DR antigens determined by used MoAbs was also proved by immunoblotting. Monoclonal antibodies Bra38 and BraFB6 did not react with the bovine cells and separated antigens. The epitope (HLA-DR) recognized by the antibody Bra38 is probably absent in cattle. The presence of HLA-DP analogue determined by the antibody BraFB6 has not been confirmed. The crossreactive MoAbs could be used for the detection of B lymphocytes and macrophages in veterinary immunology. 相似文献
2.
The indirect fluorescent antibody test (IFAT) was compared with the enzyme-linked immunosorbent assay (ELISA) for the detection of specific antibodies to Sarcocystis sp. A set of 275 ovine blood samples was examined by both reactions. Cystozoites of Sarcocystis gigantea were used as the corpuscular antigen for the IFAT. For the diagnostics of sarcocystosis by the ELISA technique used the sandwich test of the antibody titration with a soluble antigen which was also prepared from S. gigantea macrocysts. Our studies confirmed that this antigen did not cross-react with Toxoplasma gondii. Titre 40 was determined as the limit one for the IFAT and titre 80 for the ELISA; which was confirmed by the direct detection of cysts in the muscles (Svobodová, 1989). The results of both methods are shown in Table I. 76.7% of the blood samples reacted positively in the IFAT and 83.6% in the ELISA. These methods were found to be suitable and can be utilized for the intravital routine diagnostics. 相似文献
3.
B Hofírek P Horín M Granátová M Machatková J Franz I Svoboda J Blecha 《Veterinární medicína》1986,31(3):129-140
A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs. 相似文献
4.
5.
A rapid and low cost procedure, the carbon immunoassay (CIA) test, was evaluated for the diagnosis of Toxoplasma gondii infections. Using a closely related parasite (Besnoitia jellisoni) as antigen, and homologous or heterologous immune sera, it was demonstrated by light and electron microscopy that CIA is a very reliable and specific test. As it is neither expensive nor time-consuming, it can be recommended for general and routine laboratory use. 相似文献
6.
L Várnagy 《Acta veterinaria Hungarica》1992,40(3):203-206
Fertile pheasant's eggs were treated with the insecticide Wofatox 50 EC (50% methyl-parathion) by injection technique on day 12 of the hatching period. Treatment consisted of inoculation of 0.1 ml of different concentrations of the insecticide into the air space of embryonated eggs. The following dose levels were employed: 0.00, 1.35, 13.5 and 135.0 mg/kg egg of active ingredient. Biochemical changes in the plasma were evaluated by micro (photometric) methods which rendered possible the determination of several blood plasma variables of the embryos. At the highest dose level applied, serum alkaline phosphatase (SAP) enzyme activity and inorganic P concentration of the treated embryos showed statistically differences (reduction) as compared to the control data. Macroscopic alterations were detected at necropsy. 相似文献
7.
Bovine cumulus-oocyte complexes (COCs) were aspirated from antral follicles (3–6 mm in diameter). COCs with a compact multilayered cumulus investment were cultured for 9, 13 and 24 hours, respectively, and processed for scanning or transmission electron microscopy after different periods of culture including a 0 hour control group. In all 0 hour control COCs initial formation of cumulus cell projections, blebs and microvilli were observed. The start of cumulus-oocyte disconnection in cattle was observed after 9 hours of in vitro culture. These connections were almost completely discrupted after 13 hours, when a continuous production of extracellular matrix was observed. The full expansion of corona radiata cells was not observed even after 24 hours. Some cumulus oophorus cells were bound together with junctions of the zonula adherens type after 24 hours when extracellular matrix was found only in deeper layers. The full expansion of corona radiata cells was not the prerequisite for disconnection of cumulus-oocyte complex. Inhalt: Kumulus oophorus Expansion von in vitro kultivierten Rinderoozyten: Eine SEM und TEM Untersuchung Kumulus-Oozyten-Komplexe (COC) von Rindern wurden aus antralen Follikeln aspiriert (Durchmesser 3–6 mm). COC's mit kompakten mehrschichtigen Kumulus wurden für 9, 13 und 24 Stunden kultiviert und für die Scanner- oder Transmissionselektronenmikroskopie vorbereitet. Verschiedene Kulturzeiten incl. einer 0-Stundengruppe als Kontrolle wurden untersucht. In allen Kontroll COC's wurden beginnende Formationen yon Kumuluszellprojektionen, Bläschen und Mikrovilli beobachtet. Nach 9-stündiger in vitro Kultur begann die Lösung zwischen Kumulus und Oozyte. Die Verbindungen waren nach 13 Stunden vollständig unterbrochen, wobei eine kontinuierliche Produktion extrazellulärer Matrix beobachtet wurde. Eine vollständige Expansion der Corona radiata Zellen wurde auch nicht nach 24 Stunden beobachtet. Nach 24 Stunden waren einige Cumulus Oophorus Zellen über Verbindungen des Zonula adherens Typs verknüpft, wobei extrazelluläre Matrix nur in den tieferen Zellschichten gefunden wurde. Eine vollständige Kumulusexpansion ist keine Voraussetzung für die Auflösung des Kumulus-Oozyten-Komplexes. 相似文献
8.
The heterogenicity of Cowdria ruminantium stocks: cross-immunity and serology in sheep and pathogenicity to mice 总被引:2,自引:0,他引:2
J L Du Plessis L Van Gas J A Olivier J D Bezuidenhout 《The Onderstepoort journal of veterinary research》1989,56(3):195-201
Ten stocks of Cowdria ruminantium (Ball 3, Breed, Comoro, Germishuys, Kümm, Kwanyanga, Mali, Mara, Nonile and Welgevonden) were compared from a cross-immunity, serological and mouse pathogenicity point of view. They were found to differ in varying degrees. Except for the Ball 3, Comoro and Germishuys stocks that were similar but not identical, there was no pattern in the antigenic diversity of the 10 stocks. The Welgevonden stock emerged as the stock that elicits an immunity against most of the South African stocks. The inability of the reference Ball 3 stock to protect sheep against no fewer than 6 other stocks questions the advisability of retaining this stock as the vaccine stock. The antigenic diversity of the 10 stocks could not be correlated with the antibody levels detected with the indirect fluorescent antibody test, since the sera against all 10 stocks reacted positively to the Kümm stock antigen and the variation in titres was not stock-related. 相似文献
9.
The utilization of dietary lysine for protein synthesis is affected by the digestibility of protein-bound lysine, by its intestinal resorption and by its oxidative catabolism. The approach chosen in this paper enables a comparison of the cumulative effect of these processes on the utilization of free and protein-bound lysine, respectively. The principle of the approach is based on a quantification of the expiration of 14C-labelled carbon dioxide after an oral administration of a diet, which contains L-(U-14C)-lysine either as a free amino acid or bound to yeast proteins. During an adaptation phase cockerels of the Japanese quail received a diet based mainly on ground wheat and wheat gluten. This diet was supplemented either with yeast proteins or with a mixture of L-amino acids which simulates the composition of the yeast proteins. In the main experiment the expiration of labelled carbon dioxide was measured during 240 minutes after the administration of the corresponding labelled diets. Just before treatment the animals were either in the postprandial phase or in a state of slight hunger. The maximum of expiration of labelled carbon dioxide occurred around the 60th minute after administration of the corresponding labelled diets. The cumulative expiration of labelled carbon dioxide, expressed in per cent of the radioactive dose used, amounts to 15.5% and 14.3% for free and protein-bound lysine, respectively. The utilization of both forms of lysine in the Japanese quail is lower than in broilers. 相似文献
10.
The fertility of male coypu sperm following seminal vesicle extirpation was investigated using the penetration test into the egg of Syrian golden hamster (Mesocricetus auratus). Ejaculates were obtained from five males by means of electro-ejaculation under halothane narcosis. The results of the zona-free hamster eggs (ZFHE) penetration test showed that the ejaculates of all the surgically treated coypu males were fertile and that ZFHE value fluctuated from 54 to 76.6%. The results obtained in experiments with natural mating revealed that the extirpation of male coypu seminal vesicles did not affect their fertility. In total 47 foetuses were found post mortem in ten coypu females covered by surgically treated males, which on average represented 4.7 foetuses per female. 相似文献