全文获取类型
收费全文 | 191376篇 |
免费 | 10555篇 |
国内免费 | 136篇 |
专业分类
林业 | 8018篇 |
农学 | 6676篇 |
基础科学 | 1294篇 |
24460篇 | |
综合类 | 30963篇 |
农作物 | 7546篇 |
水产渔业 | 9974篇 |
畜牧兽医 | 97815篇 |
园艺 | 2660篇 |
植物保护 | 12661篇 |
出版年
2019年 | 1952篇 |
2018年 | 2905篇 |
2017年 | 3355篇 |
2016年 | 3098篇 |
2015年 | 2599篇 |
2014年 | 3278篇 |
2013年 | 7662篇 |
2012年 | 5829篇 |
2011年 | 7279篇 |
2010年 | 4717篇 |
2009年 | 4837篇 |
2008年 | 7049篇 |
2007年 | 6595篇 |
2006年 | 6305篇 |
2005年 | 5720篇 |
2004年 | 5469篇 |
2003年 | 5568篇 |
2002年 | 5108篇 |
2001年 | 6234篇 |
2000年 | 6255篇 |
1999年 | 4905篇 |
1998年 | 2099篇 |
1997年 | 2088篇 |
1996年 | 1852篇 |
1995年 | 2199篇 |
1994年 | 1954篇 |
1993年 | 1841篇 |
1992年 | 3783篇 |
1991年 | 3982篇 |
1990年 | 3867篇 |
1989年 | 3848篇 |
1988年 | 3471篇 |
1987年 | 3432篇 |
1986年 | 3510篇 |
1985年 | 3369篇 |
1984年 | 2720篇 |
1983年 | 2425篇 |
1982年 | 1661篇 |
1979年 | 2525篇 |
1978年 | 1996篇 |
1977年 | 1634篇 |
1976年 | 1721篇 |
1975年 | 1876篇 |
1974年 | 2156篇 |
1973年 | 2143篇 |
1972年 | 2010篇 |
1971年 | 1902篇 |
1970年 | 1839篇 |
1969年 | 1852篇 |
1967年 | 1666篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Thyme ( Thymus vulgaris L.) plants were spaced at 15, 30 or 45 cm distances in a clay-loamy soil. They received different levels of nitrogen and phosphorus, besides a constant level of potassium. The results showed, that the wider spacing promoted the growth and production of herb and oil per plant, however dense cultivation significantly increased the yields of herb and oil per unit area. In all cases, the applied fertilization treatments significantly increased the productivity per unit area. Dense cultivation accompanied with higher levels of fertilization proved to be very usefull. The essential oil content was not influenced by either the plant spacing or fertilization treatments applied in this study. 相似文献
72.
73.
74.
S Katsuda H Hosomi M Shiomi Y Watanabe 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(4):669-673
Effects of atherosclerosis on the mean value and daily variation of arterial pressure were studied in 12 Watanabe-heritable hyperlipidemic (WHHL) rabbits aged 12 to 35 months and 25 normal Japanese white rabbits aged 6 to 30 months. A pressure catheter was inserted through the left subclavian artery under pentobarbital anesthesia. A few days after the catheterization, the mean arterial pressure (MAP) of the rabbits, which were active and in a good state of appetite, was recorded by an analogue-to-digital converter every second for about 6 hrs and stored in a computer. The mean (M) and standard deviation (SD) in the WHHL rabbit, calculated from each successive MAP record, ranged widely from 85.8 to 131.4 mmHg and 5.6 to 12.6 mmHg, respectively. There was no significant correlation between M and SD in the WHHL rabbit. M and variance (V) of MAP in the WHHL rabbit were significantly higher than those in the normal rabbit. M did not show any significant change with increasing ages, whereas SD increased significantly with aging in the WHHL rabbit. Concentrations of serum total cholesterol and triglyceride in the WHHL rabbit were 475 and 328 mg/dl, which were about nine and seven times as high as those in the normal rabbit, respectively. Macroscopic and histopathological examinations of the aorta revealed development and spread of sclerotic lesions with aging in the WHHL rabbit. We can conclude that development of atherosclerosis with aging in the WHHL rabbit causes malfunction of the baroreceptors, which contributes to hypertension and lability of arterial pressure. 相似文献
75.
Serum progesterone concentrations and alkaline phosphatase (ALP) activity of blood neutrophils were determined in 3 groups of cows (n = 5 each) on days 1 and 2 and then at 3-day intervals up to 32 days post-partum. Group I cows had a normal delivery, Group II cows had dexamethasone-induced parturition and Group III cows were subjected to a caesarian section. All cows in Group III and 2 cows in Group II retained their fetal membranes. Mean serum progesterone concentrations declined the second day after calving (to < 0.67 ng/ml) and remained at low levels (< 0.54 ng/ml) throughout the observation period, except for the values in Group III, which were elevated on day 16 (0.94 ng/ml), declined again on day 26 (0.46 ng/ml) and peaked (1.05 ng/ml) on day 32 portpartum. Significant (P < 0.01) differences were found between serum progesterone concentrations on day 1 and on each of the other sampling days in Groups I and III. Day X parturition group interaction was significant (P < 0.05) for the progesterone concentrations. No significant differences were found between the overall means of ALP activity of blood neutrophils in the 3 parturition groups nor between days of the experiment. No significant correlation was found between serum progesterone concentrations and ALP activity values of blood PMN during the first 32 days post-partum. Inhalt: Serum Progesteron Konzentrat und Aktivität der alkalischen Phosphatase in neutrophilen Blutzellen bei Küken mit normalem und abnormalen Geburtsverlauf Serum-Progesteronkonzentrationen und alkalische Phosphatase- (ALP) Aktivität von neutrophilen Granulozysten, nach der Abkalbung am Tag 1 und 2 und dann im Abstand von 3 Tagen bis zum 32. Tag p.p. bei Kühen untersucht, die in drei Untersuchungsgruppen (n = 5) eingeteilt waren. Gruppe I kalbte normal ab, in Gruppe II wurde die Geburt durch Dexamethason eingeleitet, und Kälber der Gruppe III wurden via Kaiserschnitt gewonnen. Alle Tiere der Gruppe III und 2 Kühe der Gruppe II wiesen Nachgeburtsverhaltungen auf Der mittlere Serum-Progesterongehalt sank am 2. Tag p.p. auf < 0,67 ng/ml ab und blieb auf niederigem Niveau (< 0,54 ng/ml) während der gesamten Untersuchungs-periode. Lediglich in Gruppe III, mit erhöhten Werten (0,94 ng/ml) an Tag 16 p.p., sanken die Werte wieder an Tag 26 p.p. (0,46 ng/ml) und erreichten einen Maximalwert an Tag 32 p.p. mit 1,05 ng/ml. Signifikante (P 0,01) Unterschiede in der Serum-Progesteronkonrentration wurden zwischen Tag 1 p.p. und allen anderen Untersuchungstagen in den Gruppen I und III gefunden. Interaktionen zwischen den Gruppen für Tag X waren signifikant (P 0,05). Keine signifikanten Unterschiede wurden für den Gesamtmittelwert der ALP-Aktivität in den neutrophilen Granulorysten zwischen den Gruppen und im Vergleich der Untersuchungstage gefunden. Es wurden auch keine signifikanten Korrelationen zwischen den Serum-Progesteronkonzentrationen und der ALP-Aktivität der PMN während der ersten 32 Tage p.p. nachgewiesen. 相似文献
76.
S C Haskins 《Journal of the American Veterinary Medical Association》1992,200(12):1945-1946
77.
78.
T Tsuboi Y Kanazawa T Syoji S Tokuhisa 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(6):1179-1181
Bovine follicular oocytes collected from bovine ovaries were exposed to bovid herpesvirus 1 (BHV-1). After washings, these oocytes were cultured to mature. As a result BHV-1 could not be removed from the oocytes and could replicate in the oocytes with cumulus cells, but not in the oocytes without the cells. Moreover, the specific fluorescence for BHV-1 was detected in the cumulus cells by a indirect immunofluorescent technique. Therefore these findings suggested BHV-1 could be absorbed in the oocytes but the replication of BHV-1 was done in the cumulus cells. 相似文献
79.
A W Mills 《Veterinary Clinics of North America: Small Animal Practice》1992,22(6):1297-1307
The impact and relevance of dentistry in a general feline practice is detailed. Hospital policy and protocol are described for client education, preanesthetic evaluation, dental procedures, and recall programs. A discussion of commonly observed feline dental problems is included. 相似文献
80.
Eleven hybridoma cell lines producing monoclonal antibodies (MAbs) against intact budgerigar fledgling disease (BFD) virions were produced and characterized. These antibodies were selected for their ability to react with BFD virions in an enzyme-linked immunosorbent assay. Each of these antibodies was reactive in the immunofluorescent detection of BFD virus-infected cells. These antibodies immunoprecipitated intact virions and specifically recognized the major capsid protein, VP1, of the dissociated virion. The MAbs were found to preferentially recognize native BFD virus capsid protein when compared with denatured virus protein. These MAbs were capable of detecting BFD virus protein in chicken embryonated cell-culture lysates by dot-blot analysis. 相似文献