全文获取类型
收费全文 | 1237篇 |
免费 | 53篇 |
专业分类
林业 | 58篇 |
农学 | 45篇 |
基础科学 | 17篇 |
246篇 | |
综合类 | 40篇 |
农作物 | 140篇 |
水产渔业 | 126篇 |
畜牧兽医 | 421篇 |
园艺 | 46篇 |
植物保护 | 151篇 |
出版年
2023年 | 16篇 |
2022年 | 49篇 |
2021年 | 59篇 |
2020年 | 56篇 |
2019年 | 82篇 |
2018年 | 52篇 |
2017年 | 78篇 |
2016年 | 59篇 |
2015年 | 42篇 |
2014年 | 48篇 |
2013年 | 90篇 |
2012年 | 78篇 |
2011年 | 77篇 |
2010年 | 52篇 |
2009年 | 40篇 |
2008年 | 47篇 |
2007年 | 36篇 |
2006年 | 42篇 |
2005年 | 46篇 |
2004年 | 31篇 |
2003年 | 21篇 |
2002年 | 31篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1290条查询结果,搜索用时 0 毫秒
71.
El-Sheekh Mostafa M. El-Naggar Amal H. Osman Mohamed E. H. Haieder Ayman 《Water, air, and soil pollution》2000,124(1-2):187-204
The effect of oil pollution on growth and metabolic activitiesof the fresh water algae Chlorella homosphaera and C.vulgaris was studied. The study was conducted on two locationsin the river Nile, one is oil polluted and the other is notpolluted. The assemblage of the different algal groups wasmonitored in both locations. Chlorophyta was more dominant thanCyanophyta and Bacillariophyta in both locations during allseasons except in winter when Bacillariophyta is the mostdominant group. The presence of crude oil or its refineryproducts (solar and lubricating) in the culture media of algaemarkedly influenced their growth, proteins and nucleic acidcontents. The toxicity of oil was a concentration dependent. Thelow concentrations stimulated growth, protein content andnucleic acids, whereas high concentrations had an inhibitoryeffect. Although DNA and RNA responded similarly to crude oil inthe two tested organisms, DNA showed more sensitivity than RNAto solar oil. Lubricating oil had a little phytotoxic effect onnucleic acids. Different species of algae response differentiallyto oil pollution; Chlorella vulgaris can be referred to asoil-sensitive, while Chlorella homosphaera can toleraterelatively higher concentrations of oil. 相似文献
72.
Abdelmonem Mohamed Amer 《Archives of Agronomy and Soil Science》2013,59(10):1179-1194
The purpose of this study was (1) to find a matching factor (u) between infiltration rate and hydraulic conductivity during steady-state infiltration, and (2) to propose equations based on infiltration and soil moisture-retention functions for prediction of the hydraulic conductivity K(θ) within the rapidly (non-capillary) drainable pores (RDP) and capillary-matrix pores of soils. The K(θ) of capillary pores was divided into K(θ)SDP, K(θ)WHP and K(θ)FCP within slowly drainable pores (SDP), water-holding pores (WHP) and fine capillary pores (FCP), respectively. Five soil profiles of calcareous sandy loam, alluvial saline and non-saline clay, located at the Nile Delta, were used to apply the proposed equations. The highest and the lowest values of K(θ)RDP were observed in calcareous and saline clay soil profiles, respectively. Values of K(θ)RDP remained higher than those for capillary pores in the studied soils. The predicted values of K(θ) in capillary and non-capillary pores classes were in the expected range for unsaturated hydraulic conductivity. Water sorptivity (S) was determined at initial unsaturated soil water conditions and calculated at steady-state infiltration (S w) using a derived equation. There was a decrease in S with an increase in soil water content; i.e. at steady-state infiltration, S decreased by 35–40% in calcareous soils and by 45–60% in alluvial clay soils. The parameter values of u and S w tended to be uniform in calcareous soils, but nonuniform in saline and non-saline clay soils. 相似文献
73.
74.
Ren L Medan MS Weng Q Jin W Li C Watanabe G Taya K 《The Journal of reproduction and development》2005,51(3):399-404
The objective of this study was to determine the immunolocalization of NGF and its receptors (TrkA and p75LNGFR) in the reproductive tract of the Japanese Shiba goats. Five adult goats were used in this study and sections of ovaries, uteri and oviducts were immunostained by the avidin-biotin-peroxidase complex method (ABC). The results showed that NGF and its receptors (TrkA and p75LNGFR) were expressed in granulosa cells, theca cells, interstitial cells and lutein cells in ovaries. Immunoreactions for NGF, TrkA and p75LNGFR were also detectable in epithelial cells and muscle cells of the ampulla and isthmus of the oviduct, and in epithelial cells and uterine glands of the uterus. These results strongly suggest autocrine and paracrine regulation of reproductive function by NGF in the reproductive tract of female Shiba goats. 相似文献
75.
76.
Journal of Crop Science and Biotechnology - Priming is a safe, easy, and effective way to increase plant tolerance against stress. This research aims to study the metabolic status of the... 相似文献
77.
Haney SAMIR Kazuaki SASAKI Eman AHMED Aly KAREN Kentaro NAGAOKA Mohamed EL SAYED Kazuyoshi TAYA Gen WATANABE 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(5):549-556
Although color Doppler ultrasonography has been used to evaluate testicular blood flow in
many species, very little has been done in goat. Eight male Shiba goats were exposed to a
single intramuscular injection of either gonadotropin-releasing hormone (GnRH group; 1
µg/kg BW) or human chorionic gonadotropin (hCG group; 25 IU/kg BW).
Plasma testosterone (T), estradiol (E2) and inhibin (INH) were measured just before (0 hr)
and at different intervals post injection by radioimmunoassay. Testis volume (TV) and
Doppler indices, such as resistive index (RI) and pulsatility index (PI) of the
supratesticular artery, were measured by B-mode and color Doppler ultrasonography,
respectively. The results indicated an increase in testicular blood flow in both groups,
as RI and PI decreased significantly (P<0.05), but this increase was
significant higher and earlier in hCG group (1 hr) than in the GnRH group (2 hr). A high
correlation was found for RI and PI with both T (RI, r= −0.862; PI, r= −0.707) and INH in
the GnRH group (RI, r=0.661; PI, r=0.701). However, a significant
(P<0.05) correlation was found between E2 and both RI (r= −0.610) and
PI (r= −0.763) in hCG group. In addition, TV significantly increased and was highly
correlated with RI in both groups (GnRH, r= −0.718; hCG, r= −0.779). In conclusion, hCG
and GnRH may improve testicular blood flow and TV in Shiba goats. 相似文献
78.
Anti-uveal melanoma activity-guided fractionation of the MeOH extract of Acacia nilotica pods resulted in the isolation of the new compound gallocatechin 5-O-gallate (5) in addition to methyl gallate (1), gallic acid (2), catechin (3), catechin 5-O-gallate (4), 1-O-galloyl-β-D-glucose (6), 1,6-di-O-galloyl-β-D-glucose (7) and digallic acid (8). The structures of the isolated compounds were elucidated on the basis of HRESIMS, NMR spectroscopy and CD data. In addition to uveal melanoma, the antiproliferative activities of the isolated compounds and the related compound epigallocatechin 3-O-gallate (EGCG) were evaluated against cutaneous melanoma, ovarian cancer, glioblastoma and normal retinal pigmented cells. 相似文献
79.
Irrigation rate and plant density effects on yield and water use efficiency of drip-irrigated corn 总被引:3,自引:0,他引:3
Salah E. El-Hendawy Essam A. Abd El-Lattief Mohamed S. Ahmed Urs Schmidhalter 《Agricultural Water Management》2008,95(7):836-844
The efficient use of water by modern irrigation systems is becoming increasingly important in arid and semi-arid regions with limited water resources. This study was conducted for 2 years (2005 and 2006) to establish optimal irrigation rates and plant population densities for corn (Zea mays L.) in sandy soils using drip irrigation system. The study aimed at achieving high yield and efficient irrigation water use (IWUE) simultaneously. A field experiment was conducted using a randomized complete block split plot design with three drip irrigation rates (I1: 1.00, I2: 0.80, and I3: 0.60 of the estimated evapotranspiration), and three plant population densities (D1: 48,000, D2: 71,000 and D3: 95,000 plants ha−1) as the main plot and split plot, respectively. Irrigation water applied at I1, I2 and I3 were 5955, 4762 and 3572 m3 ha−1, respectively. A 3-day irrigation interval and three-way cross 310 hybrid corn were used. Results indicated that corn yield, yield components, and IWUE increased with increasing irrigation rates and decreasing plant population densities. Significant interaction effects between irrigation rate and plant population density were detected in both seasons for yield, selected yield components, and IWUE. The highest grain yield, yield components, and IWUE were found for I1D1, I1D2, or I2D1, while the lowest were found for I3D2 or I3D3. Thus, a high irrigation rate with low or medium plant population densities or a medium irrigation rate with a low plant population density are recommended for drip-irrigated corn in sandy soil. Crop production functions with respect to irrigation rates, determined for grain yield and different yield components, enable the results from this study to be extrapolated to similar agro-climatic conditions. 相似文献
80.