全文获取类型
收费全文 | 636篇 |
免费 | 22篇 |
专业分类
林业 | 34篇 |
农学 | 103篇 |
基础科学 | 15篇 |
167篇 | |
综合类 | 37篇 |
农作物 | 31篇 |
水产渔业 | 38篇 |
畜牧兽医 | 135篇 |
园艺 | 13篇 |
植物保护 | 85篇 |
出版年
2023年 | 9篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 47篇 |
2012年 | 27篇 |
2011年 | 43篇 |
2010年 | 19篇 |
2009年 | 24篇 |
2008年 | 26篇 |
2007年 | 36篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 8篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 4篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 15篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1971年 | 3篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有658条查询结果,搜索用时 0 毫秒
91.
Malignant activation of a K-ras oncogene in lung carcinoma but not in normal tissue of the same patient 总被引:27,自引:0,他引:27
E Santos D Martin-Zanca E P Reddy M A Pierotti G Della Porta M Barbacid 《Science (New York, N.Y.)》1984,223(4637):661-664
A single genetic alteration, a guanine-to-cytosine transversion, is responsible for the acquisition of malignant properties by K-ras genes of two human tumor cell lines established from carcinomas of the bladder (A1698) and lung (A2182). As a consequence, arginine instead of the normal glycine is incorporated into the K-ras-coded p21 proteins at amino acid position 12. This mutation creates a restriction enzyme polymorphism that can be used to screen human cells for transforming K-ras genes. This approach was used to identify the mutational event responsible for the malignant activation of a K-ras oncogene in a squamous cell lung carcinoma of a 66-year-old man; this point mutation was not present in either the normal bronchial or parenchymal tissue or in the blood lymphocytes. Hence, malignant activation of a ras oncogene appears to be specifically associated with the development of a human neoplasm. 相似文献
92.
The shoot apical meristem (SAM) is a collection of stem cells that resides at the tip of each shoot and provides the cells of the shoot. It is divided into functional regions. The central zone (CZ) at the tip of the meristem is the domain of expression of the CLAVATA3 (CLV3) gene, encoding a putative ligand for a transmembrane receptor kinase, CLAVATA1, active in cells of the rib meristem (RM), located just below the CZ. We show here that CLV3 restricts its own domain of expression (the CZ) by preventing differentiation of peripheral zone cells (PZ), which surround the CZ, into CZ cells and restricts overall SAM size by a separate, long-range effect on cell division rate. 相似文献
93.
Activation of the c-myb locus by viral insertional mutagenesis in plasmacytoid lymphosarcomas 总被引:32,自引:0,他引:32
G L Shen-Ong M Potter J F Mushinski S Lavu E P Reddy 《Science (New York, N.Y.)》1984,226(4678):1077-1080
94.
An economic evaluation of alternative pix application strategies for cotton production using GOSSYM/COMAX 总被引:2,自引:0,他引:2
The plant growth regulator pix (mepiquat chloride) is used extensively throughout the USA cotton belt to control excessive plant growth and to enhance early crop maturity in cotton production. Economic returns from pix use can vary greatly across different production environments. This study evaluates the economic returns to dryland cotton obtained from 12 different pix application strategies under two different soil types (Bosket sandy loam and Dundee silty clay loam) and three different weather conditions (normal, cold-wet, and hot-dry) in the Mississippi delta using simulated output from the GOSSYM/COMAX cotton management system. The most profitable pix application strategies varied by soil type. Also, economic returns were larger when using different pix application strategies for different weather conditions as opposed to using one pix application strategy for all weather conditions. 相似文献
95.
Fluid flows that are smooth at low speeds become unstable and then turbulent at higher speeds. This phenomenon has traditionally been investigated by linearizing the equations of flow and testing for unstable eigenvalues of the linearized problem, but the results of such investigations agree poorly in many cases with experiments. Nevertheless, linear effects play a central role in hydrodynamic instability. A reconciliation of these findings with the traditional analysis is presented based on the "pseudospectra" of the linearized problem, which imply that small perturbations to the smooth flow may be amplified by factors on the order of 10(5) by a linear mechanism even though all the eigenmodes decay monotonically. The methods suggested here apply also to other problems in the mathematical sciences that involve nonorthogonal eigenfunctions. 相似文献
96.
R A Kramer M D Schaber A M Skalka K Ganguly F Wong-Staal E P Reddy 《Science (New York, N.Y.)》1986,231(4745):1580-1584
The gag-pol gene of HTLV-III (human T-lymphotropic virus), the virus linked to AIDS (acquired immune deficiency syndrome), was expressed in yeast, and processing of the gag precursor into proteins of the same size as those in the virion was observed. Processing of the gag gene in yeast cells mimics the process that naturally occurs in mammalian cells during maturation of virions. Therefore it was possible to perform mutational analysis of the virus genome to localize the gene that codes for the protease function to the amino terminal coding region of the pol gene. Since this region overlaps the gag gene, it is likely that ribosomal frameshifting occurs from gag to pol. Antibodies in all of the AIDS patients' sera tested recognized the yeast synthesized gag proteins, although the sera showed differences in relative reactivity to the individual gag proteins and the precursor. This yeast system should be valuable not only for production of viral proteins for diagnostic or vaccine purposes but also for analysis of the genetics and biochemistry of viral gene functions--parameters that are difficult to study otherwise with this virus. 相似文献
97.
98.
Jose Antony Appidi Krishna Reddy Arun Sudhagar Hari Krishna Vungurala Luke A Roy 《Journal of the World Aquaculture Society》2021,52(1):155-170
The suitability of inland saline groundwater as a medium to culture juvenile cobia, Rachycentron canadum, was assessed. In the first experiment, juvenile cobia stocked in raw (unamended) saline groundwater at salinities of 5, 10, and 15 g/L exhibited complete mortality after 108, 176, and 195 hr, respectively. The second experiment evaluated the rearing of juvenile cobia (mean weight ~9.23 ± 0.12 g) in potassium (K+)‐amended saline groundwater (100% K+ fortified) and reconstituted seawater at salinities of 5, 10, and 15 g/L to assess growth and osmoregulation in distinct culture media. Following 60 days of culture, all fish survived the experimental period. Final mean bodyweight of cobia reared in K+‐amended saline groundwater (103.2–115.8 g) and seawater (111.2–113.8 g) of different salinities did not vary significantly (p > .05). No differences (p > .05) were observed in specific growth rate, weight gain (%), and feed conversion ratio between treatment groups. Serum osmolality increased with salinity and was significantly higher (p < .05) for fish in K+‐amended saline groundwater (353–361 mOsmol/Kg) than in reconstituted seawater (319–332 mOsmol/Kg), although differences were not observed between salinities by water type. Cobia stocked in saline groundwater of different salinities were osmoregulating normally, and the higher values observed may be because of variations in ionic composition and other interfering ions in saline groundwater. Trial results suggest that juvenile cobia can achieve optimal growth in K+‐amended saline groundwater of low and intermediate salinities. 相似文献
99.
Dhara C. Dixit C. R. K. Reddy Nikunj Balar Poornima Suthar Tejal Gajaria Devesh K. Gadhavi 《Journal Of Aquatic Food Product Technology》2018,27(1):61-79
Eight tropical marine macro algae were investigated for in-vitro antioxidant, antibacterial, and biochemical properties. The moisture content [% DW (dry weight)] ranged from 7.21 to 14.72%; ash, 24.92 to 47.04%; lipids, 0.73 to 2.67%; protein, 4.56 to 12.59%; and carbohydrate, 30.1 to 48.51%. The % sum of polyunsaturated fatty acids (PUFAs) ranged from 21.71 to 78.22%, while omega-6/omega-3 (ω6/ω3) ratio was from 0 to 2.08, which remained within the prescribed World Health Organization (WHO) standards (<10). The % sum of essential amino acids (EAAs) ranged from 86.18 to 204.66, and Na/K ratio ranged from 0.37 to 2.85. The extracts exhibited significant (P < 0.05) values for total phenol (7.25–16.0 µg PGE mg–1 DW) and total flavonoid (4.06–15.63 µg QE mg–1 DW) at 200 µg/ml. Antibacterial activity was tested against the selected food spoilage and pathogenic bacteria. The principal component analysis (PCA) confirmed a positive correlation between total phenolic content, 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging activities, and ferric reducing antioxidant power (FRAP), which supports the integration of seaweeds as ingredients in functional foods. 相似文献
100.
Faisal Rashid Sofi S. M. Zofair Vijay Kumar Reddy Surasani K. K. Sabha Nissar Rajkumar Ratankumar Singh 《Journal Of Aquatic Food Product Technology》2013,22(3):253-263
Fatty fish have been recognized as potential raw material for production of minced meat; however, they are prone to oxidation and further deterioration. In the present study, the effect of washing and antioxidant (tannic acid) treatment on the quality of minced meat of Trachurus trachurus (horse mackerel) during frozen storage was observed. Minced meat of Trachurus trachurus was divided into three lots (T0, T1, and T2). T1 was washed with cold water, T2 with cold water containing tannic acid (100 mg/kg), and T0 was not washed. All the lots were frozen at ?40°C and stored at ?20 ± 2°C for 125 days and were subjected to biochemical, microbiological, and sensory evaluation at regular intervals of 25 days. The antioxidant treatment with tannic acid at the dosage used was found effective in minimizing the rancidity problems of minced meat (T2), compared to T0 and T1. During the whole period of storage, samples from T2 showed good quality in terms of microbiological, biochemical, and sensory analysis compared to T1 and T0. 相似文献