全文获取类型
收费全文 | 1513篇 |
免费 | 82篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 41篇 |
2021年 | 73篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 75篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 76篇 |
2014年 | 100篇 |
2013年 | 90篇 |
2012年 | 101篇 |
2011年 | 75篇 |
2010年 | 52篇 |
2009年 | 54篇 |
2008年 | 77篇 |
2007年 | 78篇 |
2006年 | 55篇 |
2005年 | 50篇 |
2004年 | 58篇 |
2003年 | 43篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 32篇 |
1999年 | 17篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1597条查询结果,搜索用时 973 毫秒
991.
This article aims to study the thin film layer flowing on a vertical oscillating belt. The flow is considered to satisfy the constitutive equation of unsteady second grade fluid. The governing equation for velocity and temperature fields with subjected initial and boundary conditions are solved by two analytical techniques namely Adomian Decomposition Method (ADM) and Optimal Homotopy Asymptotic Method (OHAM). The comparisons of ADM and OHAM solutions for velocity and temperature fields are shown numerically and graphically for both the lift and drainage problems. It is found that both these solutions are identical. In order to understand the physical behavior of the embedded parameters such as Stock number, frequency parameter, magnetic parameter, Brinkman number and Prandtl number, the analytical results are plotted graphically and discussed. 相似文献
992.
Randomly amplified polymorphic DNA analysis of four different populations of the Indian major carp, Labeo rohita (Hamilton) 总被引:3,自引:0,他引:3
The level of genetic variation provides the raw material for selective improvement of a stock. Random amplified polymorphic DNA (RAPD) assay was used to assess the genetic variation in three rivers: the Halda, the Jamuna and the Padma as well as in one hatchery population of the commercially important Indian major carp, Labeo rohita. RAPD markers were amplified from DNA samples of 35 fish from each of the four populations using six decamer random primers. The polymorphic loci proportions were 0.33, 0.28, 0.28 and 0.26 and Nei's gene diversity values were 0.06, 0.07, 0.06 and 0.05 for the Halda, the Jamuna, the Padma and the hatchery populations, respectively. The pairwise population differentiation (FST) values indicated a low level of genetic differentiation between the population pairs. From the unweighted pair group method of arithmetic mean (UPGMA) dendrogram based on Nei's genetic distances a correlation between genetic affinities and geographical area was found. The populations were segregated into two groups: the Halda in one group and the Jamuna, the Padma and the hatchery in another group. Overall, the RAPD technique can be introduced as a tool in the population genetics of the rohu fish to provide information on their genetic stock structure. 相似文献
993.
Briseis Aschebrook-Kilfoy Maria Argos Brandon L. Pierce Lin Tong Farzana Jasmine Shantanu Roy Faruque Parvez Alauddin Ahmed Tariqul Islam Muhammad G. Kibriya Habibul Ahsan 《PloS one》2015,10(3)
Human fertility is a complex trait determined by gene-environment interactions in which genetic factors represent a significant component. To better understand inter-individual variability in fertility, we performed one of the first genome-wide association studies (GWAS) of common fertility phenotypes, lifetime number of pregnancies and number of children in a developing country population. The fertility phenotype data and DNA samples were obtained at baseline recruitment from individuals participating in a large prospective cohort study in Bangladesh. GWAS analyses of fertility phenotypes were conducted among 1,686 married women. One SNP on chromosome 4 was non-significantly associated with number of children at P <10-7 and number of pregnancies at P <10-6. This SNP is located in a region without a gene within 1 Mb. One SNP on chromosome 6 was non-significantly associated with extreme number of children at P <10-6. The closest gene to this SNP is HDGFL1, a hepatoma-derived growth factor. When we excluded hormonal contraceptive users, a SNP on chromosome 5 was non-significantly associated at P <10-5 for number of children and number of pregnancies. This SNP is located near C5orf64, an open reading frame, and ZSWIM6, a zinc ion binding gene. We also estimated the heritability of these phenotypes from our genotype data using GCTA (Genome-wide Complex Trait Analysis) for number of children (hg
2 = 0.149, SE = 0.24, p-value = 0.265) and number of pregnancies (hg
2 = 0.007, SE = 0.22, p-value = 0.487). Our genome-wide association study and heritability estimates of number of pregnancies and number of children in Bangladesh did not confer strong evidence of common variants for parity variation. However, our results suggest that future studies may want to consider the role of 3 notable SNPs in their analysis. 相似文献
994.
995.
Background
Exposure to high dose radiation in combination with physical injuries such as burn or wound trauma can produce a more harmful set of medical complications requiring specialist interventions. Currently these interventions are unavailable as are the precise biomarkers needed to help both accurately assess and treat such conditions. In the present study, we tried to identify and explore the possible role of serum exosome microRNA (miRNA) signatures as potential biomarkers for radiation combined burn injury (RCBI).Methodology
Female B6D2F1/J mice were assigned to four experimental groups (n = 6): sham control (SHAM), burn injury (BURN), radiation injury (RI) and combined radiation skin burn injury (CI). We performed serum multiplex cytokine analysis and serum exosome miRNA expression profiling to determine novel miRNA signatures and important biological pathways associated with radiation combined skin-burn trauma.Principal Findings
Serum cytokines, IL-5 and MCP-1, were significantly induced only in CI mice (p<0.05). From 890 differentially expressed miRNAs identified, microarray analysis showed 47 distinct miRNA seed sequences significantly associated with CI mice compared to SHAM control mice (fold change ≥ 1.2, p<0.05). Furthermore, only two major miRNA seed sequences (miR-690 and miR-223) were validated to be differentially expressed for CI mice specifically (fold change ≥ 1.5, p<0.05).Conclusions
Serum exosome miRNA signature data of adult mice, following RCBI, provides new insights into the molecular and biochemical pathways associated with radiation combined skin-burn trauma in vivo. 相似文献996.
A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3) are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33–41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed. 相似文献
997.
Muhammad Idrees Rahu Syed Habib Ahmed Naqvi Nazakat Hussain Memon Muhammad Idrees Farhatullah Kandhro Navish Lodhi Pathan Md Nazirul Islam Sarker Muhammad Aqeel Bhutto 《Saudi Journal of Biological Sciences》2021,28(5):2867-2876
The aim of this study was to explore the effectiveness of different parts of J. curcas plant against some selected human pathogens as antimicrobial agent which are known to cause diseases and to check antioxidant and phytochemicals from different plant sections of J. curcas. Plant extracts were analyzed by quantification of antimicrobial and phytochemical compounds. This study reveals that 20% ethanol stem extract of J. curcas showed maximum antibacterial activity (40 ± 0.0 mm) against Klebsiella pneumonia. Water extract of root of J. curcas also inhibited E. coli (35.25 ± 0.35 mm). The growth of K. pneumonia and Agrobacterium tumifaciens were also ceased when ethanol extract of J. curcas root applied to check their potential as antimicrobial agent. The results also revealed that fungal species, Aspergillus niger, and Pencillium notatum noted the maximum antifungal activity in ethanol extract of flower and methanol extract of root (38.5 ± 0.7 mm) and (27.25 ± 0.35 mm) respectively. Phytochemicals and many secondary metabolites were present in J. curcas extracts such as alkaloids, steroids, tannins, glycosides, flavonoids, saponins, courmerin, and phenolic compounds. It also showed the highest density of color in the different parts of plant extract of J. curcas. Similarly, biochemical primary metabolites were observed at maximum amount of biochemical in different parts of J. curcas, and correlated with antimicrobial activity. The study concluded that J. curcas has great potential as antibacterial agent and cure various human pathogens. 相似文献
998.
Mohiminul Adib Rashedul Islam Monira Ahsan Arifur Rahman Mahmud Hossain Md Mustafizur Rahman Sultan M. Alshehri Mohsin Kazi Md Abdul Mazid 《Saudi Journal of Biological Sciences》2021,28(7):3893-3900
Tinosporide and 8-hydroxytinosporide isolated from Tinospora cordifolia were evaluated for acetylcholinesterase (AChE) and butylcholinesterase (BuChE) inhibitory activities. The structure of the compound was confirmed by spectroscopic analysis, whereas cholinesterase inhibition was investigated by Ellman method using donepezil as standard drug and the data were presented as IC50 (μg/ml ± SEM). Furthermore, donepezil, tinosporide and 8-hydroxytinosporide were executed for docking analysis. The results from the isolated compounds TC-16R confirmed as tinosporide promisingly inhibited AChE with IC50 value of 13.45 ± 0.144, whereas TC-19R confirmed as 8-hydroxytinosporide moderately inhibited AChE with IC50 value of 46.71 ± 0.511. In case of BuChE inhibition, the IC50 values were found to be 408.50 ± 17.197 and 317.26 ± 6.918 for tinosporide and 8-hydroxytinosporide, respectively. The in silico studies revealed that the ligand tinosporide fit with the binding sites and inhibited AChE. Overall, the study findings suggested that tinosporide would be a complementary noble molecule of donepezil which is correlated with its pharmacological activity through in vitro studies, while 8-hydroxytinosporide modestly inhibited BuChE and the results are very close to the standard donepezil. 相似文献
999.
Md. Obaidur Rahman Miho Sassa Natasha Parvin Md. Rashedul Islam Aya Yajima Erika Ota 《PLoS neglected tropical diseases》2021,15(3)
BackgroundMost of national schistosomiasis elimination programmes in Asia are relying on stool examination, particularly Kato Katz stool examination technique for regular transmission monitoring. However, the Kato-Katz technique has shown low sensitivity for the detection of light-intensity infections, and therefore highly sensitive diagnostic tools are urgently required to monitor prevalence of infection in low transmission settings. The objective of this systematic review was to evaluate and synthesize the performance of diagnostic tests for detecting Schistosoma japonicum and S. mekongi infection in people living in endemic areas.Methodology/Principal findingsWe comprehensively searched these nine electronic databases and other resources until July 2019, with no language or publication limits: PubMed, EMBASE, MEDLINE, Web of Science, BIOSIS Citation Index, HTA, CINAHL PLUS, The Cochrane Library, and PsycINFO. We included original studies that assessed diagnostic performance using antibody, antigen, and molecular tests with stool examination test as a reference standard. Two reviewers independently extracted a standard set of data and assessed study quality. We estimated the pooled estimates of sensitivity and specificity for each index test. We used diagnostic odds ratio to determine the overall accuracy and hierarchical summary receiver operating characteristics (HSROC) curve to assess the index tests performance.Fifteen studies (S. japonicum [n = 13] and S. mekongi [n = 2]) testing 15,303 participants were included in the review. Five studies reported performance of enzyme-linked immunosorbent assay (ELISA), seven studies reported indirect hemagglutination assay (IHA), and four studies reported polymerase chain reaction (PCR) for detecting S. japonicum. The pooled sensitivity and specificity were 0.93 (95% CI: 0.84–0.98) and 0.40 (95% CI: 0.29–0.53) for ELISA, 0.97 (95% CI: 0.90–0.99) and 0.66 (95% CI: 0.58–0.73) for IHA, and 0.89 (95% CI: 0.71–0.96) and 0.49 (95% CI: 0.29–0.69) for PCR respectively. A global summary indicated the best performance for IHA, closely followed by ELISA. We were unable to perform meta-analysis for S. mekongi due to insufficient number of studies.Conclusions/SignificanceIHA showed the highest detection accuracy for S. japonicum. Further studies are needed to determine the suitable diagnostic methods to verify the absence of transmission of S. mekongi and also to compare detection accuracy against more sensitive reference standards such as PCR. 相似文献
1000.
Md. Parvez Anwar Md. Ariful Islam Khalid A. K. M. Mominul Islam Sabina Yeasmin Sharif Ahmed Adel Hadifa Ismail A. Ismail Akbar Hossain Ayman EL Sabagh 《Phyton》2021,90(5):1491-1506
Seed priming has proved to be an effective pre-germination seed invigoration technique for different crops to
improve seed and seedling performance under different abiotic stresses. In Bangladesh, winter rice is very often
exposed to cold waves just after sowing in the nursery bed resulting in poor seed germination and seedling emergence, yellowish and thin seedlings production, and a very low survival rate. Seed priming may mitigate the cold
stress during seed germination and seedling emergence and helps in the quality seedling production of winter rice.
To evaluate the efficacy of different seed priming techniques in increasing seedling emergence, growth, vigor and
survivability of winter rice cultivars under cold stress, a pot experiment was conducted at the Department of Agronomy, Bangladesh Agricultural University during December 2018 to January 2019. The experiment comprised
two factors, (A) Winter rice variety namely, i) BRRI dhan29 and ii) BRRI dhan36; (B) Seed priming agent namely
i) Control (no priming), ii) 20000 ppm NaCl, iii) 30000 ppm NaCl, iv) 20000 ppm KCl, v) 30000 ppm KCl, vi)
20000 ppm CaCl2, vii) 30000 ppm CaCl2, viii) 50 ppm CuSO4, ix) 75 ppm CuSO4, x) 10000 ppm ZnSO4, xi)
15000 ppm ZnSO4, xii) 2 ppm Na2MoO4, xiii) 3 ppm Na2MoO4, xiv) 100 ppm PEG (Polyethylene glycol
4000) and xv) 150 ppm PEG. Seeds were sown on two different dates viz., 1st December and 1st January so that
seedlings are exposed to cold stress at different stages. The experiment was laid out in a completely randomized
design (CRD) with three replications. Results indicated that (in most of the cases) seed priming has a positive
impact on seedling emergence rate (%), root length, shoot length, root shoot ratio, root dry weight, shoot dry
weight, seedling dry weight and survival rate (%). Among the priming agents, KCl and CaCl2 performed best;
while priming with NaCl and PEG showed no advantages over no priming for both the sowing dates. In general,
BRRI dhan36 performed better than BRRI dhan29 in terms of seedling growth because of its higher tolerance to
cold stress. But, both the varieties performed similarly in terms of emergence rate and survival rate. Thus, priming
is an effective tool to increase seed germination, better seedling growth, and higher seedling survivability of winter
rice under cold stress, and KCl (20000 ppm) or CaCl2 (20000 ppm) can be considered as a viable priming agent. 相似文献