全文获取类型
收费全文 | 3675篇 |
免费 | 173篇 |
国内免费 | 27篇 |
专业分类
3875篇 |
出版年
2024年 | 11篇 |
2023年 | 82篇 |
2022年 | 183篇 |
2021年 | 312篇 |
2020年 | 156篇 |
2019年 | 180篇 |
2018年 | 248篇 |
2017年 | 154篇 |
2016年 | 221篇 |
2015年 | 268篇 |
2014年 | 287篇 |
2013年 | 286篇 |
2012年 | 291篇 |
2011年 | 244篇 |
2010年 | 159篇 |
2009年 | 141篇 |
2008年 | 136篇 |
2007年 | 122篇 |
2006年 | 85篇 |
2005年 | 78篇 |
2004年 | 46篇 |
2003年 | 41篇 |
2002年 | 28篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1968年 | 1篇 |
排序方式: 共有3875条查询结果,搜索用时 0 毫秒
121.
Ritu Gupta Imran Kazmi Muhammad Afzal Ruqaiyah Khan Mohit Chauhan Fahad A. Al-Abbasi Aftab Ahmad Firoz Anwar 《Molecular and cellular biochemistry》2013,384(1-2):279-285
Sulfonamides have been reported to possess substantial antitumor activity as they act as carbonic anhydrase inhibitors. In addition, selenium appears to have a protective effect at various stages of cancer due to its antioxidant property, enhanced carcinogen detoxification, inhibition of cell invasion, and by inhibiting angiogenesis. Here, in the present study we aimed to evaluate and synergize the cytotoxic activity of sulfonamide and selenium (SM+SE) as effective therapy in the treatment of DENA-induced HCC. Hepatocarcinogeneis was induced by a single intraperitoneal injection of diethylnitrosamine (DENA) (200 mg/kg) in phosphate buffer. 30 Male Wistar rats used in this study were divided randomly into five equal groups (n = 6). DENA-administered animals showed significant alteration (p < 0.001) in liver-specific enzymes—glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), alkaline phosphatase (ALP), and Alpha fetoproteins (AFP), and also induced severe histopathological changes in the hepatic tissues. Interestingly, treatment with (SE+SE) (SM 30 mg/kg + SE 3 mg/kg) significantly reduced (P < 0.001, P < 0.001, P < 0.001, P < 0.001) the elevated AFP, SGOT, SGPT, and ALP levels, respectively, suggesting that combination therapy of SM+SE has a potential to treat DENA-induced liver damage. 相似文献
122.
Regulation in Plant Stress Tolerance by a Potential Plant Growth Regulator, 5-Aminolevulinic Acid 总被引:4,自引:0,他引:4
Exogenous application of different plant growth regulators is a well-recognized strategy to alleviate stress-induced adverse effects on different crop plants by regulating a variety of physiobiochemical processes such as photosynthesis, chlorophyll biosynthesis, nutrient uptake, antioxidant metabolism, and protein synthesis, which are directly or indirectly involved in the mechanism of stress tolerance. Of various environmental factors, salinity, drought, and extreme temperature (low or high) considerably diminish plant growth and yield by modulating endogenous levels as well as signaling pathways of plant hormones. Of various plant hormones/regulators, a potential plant growth regulator, 5-aminolevulinic acid (ALA), is known to be effective in counteracting the injurious effects of various abiotic stresses in plants. Until now the mechanisms behind ALA regulation of growth under stress have not been fully elucidated. It is also not yet clear how far growth and yield in different crops can be promoted by exogenous application of ALA and whether this ALA-induced growth and yield promotion is cost-effective. Thus, in this review we discuss at length the effects of ALA in regulating growth and development in plants under a variety of abiotic stress conditions, including salinity, drought, and temperature stress. Furthermore, advances in the functional and regulatory interactions of this plant growth regulator with plant stress tolerance, as well as the effective mode of exogenous application of ALA in inducing stress tolerance in plants are also comprehensively discussed in this review. In the future, overaccumulation of ALA in plants through manipulation of gene(s) could enhance plant stress tolerance. Thus, genetic manipulation of plants with the goal of attaining increased synthesis/accumulation of ALA and hence improved stress tolerance under stress conditions is an important area for research. 相似文献
123.
Muhammad Saqib Javaid Akhtar Ghulam Abbas Muhammad Nasim 《Acta Physiologiae Plantarum》2013,35(9):2761-2768
Salinity and drought are important agro-environmental problems occurring separately as well as together with the combined occurrence increasing with time due to climate change. Screening of bread wheat genotypes against salinity or drought alone is common; however, little information is available on the response of wheat genotypes to a combination of these stresses. This study investigates the response of a salt-resistant (SARC-1) and a salt-sensitive (7-Cerros) wheat genotype to drought at different growth stages under non-saline (ECe 2.1 dS m?1) and saline soil (ECe 15 dS m?1) conditions. Drought was applied by withholding water for 21 days at a particular growth stage viz. tillering, booting, and grain filling stages. At booting stage measurements regarding water relations, leaf ionic composition and photosynthetic attributes were made. At maturity grain yield and different yield, components were recorded. Salinity and drought significantly decreased grain yield and different yield components with a higher decrease in the case of combined stress of salinity × drought. The complete drought treatment (drought at tillering + booting + grain filling stages) was most harmful for wheat followed by drought at booting stage and grain filling–tillering stages, respectively. The salt-resistant wheat genotype SARC-1 performed better than the salt-sensitive genotype 7-Cerros in different stress treatments. A decrease in the water and turgor potentials, photosynthetic and transpiration rates, stomatal conductance, leaf K+, and increased leaf Na+ were the apparent causes of growth and yield reduction of bread wheat due to salinity, drought, and salinity × drought. 相似文献
124.
Fungal degradation of low rank coal has appeared as an alternative technique for exploitation of non-fuel options. A fungal isolate, MW1, was isolated and coal sample was subjected to fungal pretreatment. The residual coal was processed for extraction of humic acid for determining the effect of such pretreatment. Extracted humic acid was analyzed on the basis of elemental composition and spectroscopy. Fungal pretreatment caused improvement in oxygen content, E4/E6 ratio, and absorption bands related to humic materials. Conclusively, pretreatment resulted in improving chemical attributes of humic acid molecule, thus, warranting supplementary high-tech investigations for the optimization of process upscale. 相似文献
125.
Syed Ghulam Musharraf Arslan Ali Naik Tameem Khan Maria Yousuf Muhammad Iqbal Choudhary 《Steroids》2013,78(2):171-181
Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to investigate the effect of different substitutions introduced during metabolism on fragmentation patterns of four anabolic steroids including methyltestosterone, methandrostenolone, cis-androsterone and adrenosterone, along with their metabolites. Collision-induced dissociation (CID) analysis was performed to correlate the major product ions of 19 steroids with structural features. The analysis is done to portray metabolic alteration, such as incorporation or reduction of double bonds, hydroxylations, and/or oxidation of hydroxyl moieties to keto functional group on steroidal skeleton which leads to drastically changed product ion spectra from the respective classes of steroids, therefore, making them difficult to identify. The comparative ESI-MS/MS study also revealed some characteristic peaks to differentiate different steroidal metabolites and can be useful for the unambiguous identification of anabolic steroids in biological fluid. Moreover, LC–ESI-MS/MS analysis of fermented extract of methyltestosterone, obtained by Macrophomina phaseolina was also investigated. 相似文献
126.
Haitao Li Muhammad Younas Xiaofeng Wang Xuemin Li Lin Chen Bo Zhao Xun Chen Jinsong Xu Fan Hou Baohua Hong Gang Liu Hongyang Zhao Xueli Wu Hongzhi Du Jiangsheng Wu Kede Liu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2013,126(4):937-947
Brassica napus (AACC) is a recent allotetraploid species evolved through hybridization between two diploids, B. rapa (AA) and B. oleracea (CC). Due to extensive genome duplication and homoeology within and between the A and C genomes of B. napus, most SSR markers display multiple fragments or loci, which limit their application in genetics and breeding studies of this economically important crop. In this study, we collected 3,890 SSR markers from previous studies and also developed 5,968 SSR markers from genomic sequences of B. rapa, B. oleracea and B. napus. Of these, 2,701 markers that produced single amplicons were putative single-locus markers in the B. napus genome. Finally, a set of 230 high-quality single-locus SSR markers were established and assigned to the 19 linkage groups of B. napus using a segregating population with 154 DH individuals. A subset of 78 selected single-locus SSR markers was proved to be highly stable and could successfully discriminate each of the 45 inbred lines and hybrids. In addition, most of the 230 SSR markers showed the single-locus nature in at least one of the Brassica species of the U’s triangle besides B. napus. These results indicated that this set of single-locus SSR markers has a wide range of coverage with excellent stability and would be useful for gene tagging, sequence scaffold assignment, comparative mapping, diversity analysis, variety identification and association mapping in Brassica species. 相似文献
127.
128.
Adel Shalata Maria C. Ramirez Robert J. Desnick Nolan Priedigkeit Christoph Buettner Claudia Lindtner Mohammed Mahroum Muhammad Abdul-Ghani Feng Dong Nazik Arar Olga Camacho-Vanegas Rui Zhang Sandra C. Camacho Ying Chen Mwafaq Ibdah Ralph DeFronzo Virginia Gillespie Kevin Kelley Brian D. Dynlacht Sehyun Kim Marc J. Glucksman Zvi U. Borochowitz John A. Martignetti 《American journal of human genetics》2013
129.
Mahim Khan Muhammad Qasim Usman Ali Ashfaq Sobia Idrees Masoud Shah 《Bioinformation》2013,9(14):710-714
Background:
HCV has become a leading cause of liver cirrhosis and hepatocellular carcinoma and is a major health concern worldwide. To date,
there is no vaccine available in the market to tackle this disease, therefore there is a strong need to develop antiviral compounds
that can target all genotypes of HCV with the same efficiency. Medicinal plants have low cost and are less toxic therefore, extracts
of medicinal plants can serve as important antiviral agents against HCV. This study was designed to screen phytochemicals of
Accacia nilotica to find a potent drug candidate that can inhibit HCV infection effectively.Results:
Docking of NS3/4A protease and Flavonoids of Accacia nilotica revealed that most of the flavonoids bound deeply with the active
site of NS3/4A protease. Compound 01 showed a high ranking on docking score. All other compounds also showed reliable
docking scores and had interactions with the binding cavity of NS3/4A protease, suggesting them as a potent drug candidate to
block HCV replication.Conclusion:
To recognize binding interactions of Accacia nilotica phytochemicals with NS3/4A protease, molecular docking was performed to
find potential inhibitor against NS3/4A protease of HCV. After post docking analysis, important interactions were found between
active compounds and active site of NS3/4A protease. It can be concluded from the study that phytochemicals of Accacia nilotica
may serve as a potential drug candidate with relatively simple structural changes against HCV NS3/4A protease. 相似文献
130.
Yong Seong Lee Yun Serk Park Muhammad Anees Young Cheol Kim Yong Hwan Kim 《Biocontrol Science and Technology》2013,23(12):1427-1441
Lysobacter capsici YS1215 is a soil-borne strain that could inhibit the growth of phytopathogenic fungi, including Phytophthora capsici, Rhizoctonia solani and Fusarium oxysporum, as well as root-knot nematodes. The effect of different concentrations of bacterial culture filtrate (BCF) of L. capsici YS1215 on the mortality of second-stage juveniles (J2) of Meloidogyne incognita was studied using 24-well plates. The J2 mortality increased with increasing concentrations of BCF. YS1215 also produces gelatinases in the culture filtrate. To study its role in nematicidal activities, the partial purification and the characterisation of gelatinolytic proteins were done from the culture medium of the YS1215. The partially purified proteins showed three clear bands with molecular weights estimated using zymography to be 255.7, 232.1 and 146.4 kDa. The optimal pH and temperature for the proteins were 8.0 and 40°C, respectively. The activity of the proteins was inhibited by ethylenediaminetetraacetic acid, FeCl3 and 1,10-phenanthroline, whereas it was activated by MnCl2. The proteins may belong to the group of metalloproteases. Moreover, the proteins could hydrolyse skimmed milk, collagen, gelatin and bovine serum albumin (BSA) as substrates, but not casein. The proteins could induce 75% J2 mortality in five days and degrade the J2 bodies. The present study demonstrates the role of the gelatinolytic proteins in the nematicidal potential of L. capsici YS1215. 相似文献