全文获取类型
收费全文 | 1874篇 |
免费 | 95篇 |
国内免费 | 4篇 |
专业分类
1973篇 |
出版年
2023年 | 21篇 |
2022年 | 58篇 |
2021年 | 115篇 |
2020年 | 41篇 |
2019年 | 57篇 |
2018年 | 77篇 |
2017年 | 54篇 |
2016年 | 57篇 |
2015年 | 81篇 |
2014年 | 107篇 |
2013年 | 129篇 |
2012年 | 121篇 |
2011年 | 130篇 |
2010年 | 55篇 |
2009年 | 51篇 |
2008年 | 72篇 |
2007年 | 61篇 |
2006年 | 72篇 |
2005年 | 49篇 |
2004年 | 30篇 |
2003年 | 35篇 |
2002年 | 28篇 |
2001年 | 34篇 |
2000年 | 30篇 |
1999年 | 29篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1995年 | 6篇 |
1994年 | 20篇 |
1993年 | 11篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 9篇 |
1970年 | 7篇 |
1911年 | 7篇 |
排序方式: 共有1973条查询结果,搜索用时 0 毫秒
71.
A survey was conducted with the aim to document the indigenous information of Charkotli Hills, Batkhela District, Malakand,
Pakistan. The area has rich vegetation and a high potential for ethnobotanical utilization. Information was collected on various
traditional uses of 100 plants distributed over 49 families, of which 43 families were of dicot, 2 of monocot, 2 of pteridophyta,
and 1 of gymnosperms. Most plants have more than one local use. Sixty-six plants were found to be medicinal species, 21 fruit
and edible seed species, 11 furniture species, 18 fodder or forage species, 12 vegetable species, 12 fuel species, 11 thatching
and building species, 5 hedge or fencing species, 5 timber wood species, 5 poisonous plants, 3 species used in ketchup, 2
fixed oil yielding species, 2 miswak species, 2 species for making sticks for cattle and defense purposes, 2 species cultivated
for ornamental purposes, 2 species used as mehindi by girls, 1 irritant species, 1 species for the making of Salai (a little
stick for applying ‘surma’ to the eyes), 1 species for tanning, 1 species used as refresher in milk pots, 1 species giving
gum used as chewing gum, and 1 species used as insect repellent. The area is under heavy pressure of deforestation and overgrazing,
which have reduced the regeneration of woody plants. Proper ecological management is required to protect the wildlife and
ethnobotanical resources for the coming generations. 相似文献
72.
Hussain MA Naveed SA Sechi LA Ranjan S Alvi A Ahmed I Ranjan A Mukhopadhyay S Ahmed N 《PloS one》2008,3(1):e1481
Background
H. pylori causes gastritis and peptic ulcers and is a risk factor for the development of gastric carcinoma. Many of the proteins such as urease, porins, flagellins and toxins such as lipo-polysaccharides have been identified as potential virulence factors which induce proinflammatory reaction. We report immunogenic potentials of isocitrate dehydrogenase (ICD), an important house keeping protein of H. pylori.Methodology/Principal Findings
Amino acid sequences of H. pylori ICD were subjected to in silico analysis for regions with predictably high antigenic indexes. Also, computational modelling of the H. pylori ICD as juxtaposed to the E. coli ICD was carried out to determine levels of structure similarity and the availability of surface exposed motifs, if any. The icd gene was cloned, expressed and purified to a very high homogeneity. Humoral response directed against H. pylori ICD was detected through an enzyme linked immunosorbent assay (ELISA) in 82 human subjects comprising of 58 patients with H. pylori associated gastritis or ulcer disease and 24 asymptomatic healthy controls. The H. pylori ICD elicited potentially high humoral immune response and revealed high antibody titers in sera corresponding to endoscopically-confirmed gastritis and ulcer disease subjects. However, urea-breath-test negative healthy control samples and asymptomatic control samples did not reveal any detectable immune responses. The ELISA for proinflammatory cytokine IL-8 did not exhibit any significant proinflammatory activity of ICD.Conclusions/Significance
ICD of H. pylori is an immunogen which interacts with the host immune system subsequent to a possible autolytic-release and thereby significantly elicits humoral responses in individuals with invasive H. pylori infection. However, ICD could not significantly stimulate IL8 induction in a cultured macrophage cell line (THP1) and therefore, may not be a notable proinflammatory agent. 相似文献73.
Uddin S Hussain A Al-Hussein K Platanias LC Bhatia KG 《Biochemical and biophysical research communications》2004,320(3):932-938
We examined the functional role of the phosphatidylinositol 3'-kinase pathway in the growth and survival of cell lines of T-cell origin. Pharmacological inhibition of PI3'-kinase using LY294002 resulted in apoptosis of acute lymphoblastic T-cell leukemia (T-ALL) cell lines including CEM, Jurkat, and MOLT-4. On the other hand, the cutaneous T-cell lymphoma cell line HUT-78 was found to be refractory to LY294002- inducible apoptosis. Sensitivity or resistance to pharmacological inhibitors of PI3'-kinase correlated with tumor suppressor PTEN gene expression, as sensitive T-ALL cells do not express PTEN and have high level of activated AKT, in contrast to HUT-78 cells. Our data demonstrate that inhibition of PI3'-kinase results in dephosphorylation of AKT and partial inhibition of Bcl-xL expression in T-ALL cells, but not in HUT-78 cells. Interestingly, HUT-78 cells were also found to express higher levels of Bcl-xL protein as compared to T-ALL cells. Inhibition of PI3'-kinase also induces release of cytochrome c from mitochondria and activation of caspase-3 and PARP in all T-ALL cell lines tested, but not in HUT-78 cells. Taken altogether, our data demonstrate that the PI3'-kinase/AKT pathway plays a major role in the growth and survival of PTEN-null T-ALL cells, and identify this cascade as promising target for therapeutic intervention in acute T-cell leukemias. 相似文献
74.
Iqbal Ahmad Kiran Qadeer Saima Zahid Muhammad Ali Sheraz Tehmina Ismail Waqar Hussain Izhar Ahmad Ansari 《AAPS PharmSciTech》2014,15(5):1324-1333
The degradation kinetics of 5 × 10−5 M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0–8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kinetics and the values of the rate constants at pH 1.0–8.0 range from 0.08 to 1.05 × 10−5 s−1 and 0.22–7.62 × 10−5 s−1, respectively, in the presence of 0.25 × 10−3 M AH2. The t1/2 values of B12 and B12b range from 13.7 to 137.5 h and 2.5–87.5 h, respectively. The second-order rate constants for the interaction of AH2 with B12 and B12b are 0.05–0.28 × 10−2 and 1.10–30.08 × 10−2 M−1 s−1, respectively, indicating a greater effect of AH2 on B12b compared to that of B12. The kobs–pH profiles for both B12 and B12b show the highest rates of degradation around pH 5. The degradation of B12 and B12b by AH2 is affected by the catalytic effect of phosphate ions on the oxidation of AH2 in the pH range 6.0–8.0.KEY WORDS: ascorbic acid, cyanocobalamin, degradation, hydroxocobalamin, kinetics, two-component spectrometry 相似文献
75.
Hena Naqvi Syed Rizwan Hussain Mohammad Kaleem Ahmad Farzana Mahdi Shyam Pyari Jaiswar Satya Narayain Shankhwar Abbas Ali Mahdi 《Molecular biology reports》2014,41(2):573-579
Failure or severe difficulty in conceiving a child is surprisingly common, worldwide problem. Half of these cases are due to male factors with defects in sperm (1 in 15 men) being the single most common cause. Also about 60–75 % of male infertility cases are idiopathic, since the molecular mechanisms underlying the defects remain unknown. DNA methylation is crucial for spermatogenesis and high methylenetetrahydrofolate reductase (MTHFR) activity in adult testis than other organs in mouse, signifies its critical role in spermatogenesis. According to recent findings there is a correlation of epigenetic regulation of several imprinted genes with disturbed spermatogenesis and fertility. Consequently any change in the MTHFR gene sequence can modify the spermatogenesis including transmission of infertility to the carriers. The aim of the study is to analyze the distribution of the single nucleotide polymorphism C677T in the MTHFR gene in 637 North Indian infertile patients and 364 fertile North Indian men as controls by using PCR–RFLP technique and Chi Square test for statistical analysis. The average MTHFR 677CC, 677CT, 677TT genotype frequencies of total infertile men were 70.17, 24.17, 5.65 % in infertile men and 75.27, 21.7, 2.74 % in controls, respectively. The average frequency of the MTHFR 677T allele was 17.73 % in infertile men as compared to 13.59 % in controls. The statistical difference was significant. Disease risk was found 2.27-folds increased in patients who were carrying T allele. We found an association of C677T polymorphism with male infertility and that it may be a genetic risk factor for male infertility in North Indian population. 相似文献
76.
Molybdenum supply increases root system growth of winter wheat by enhancing nitric oxide accumulation and expression of NRT genes 总被引:1,自引:0,他引:1
Imran Muhammad Sun Xuecheng Hussain Saddam Rana Muhammad Shoaib Saleem Muhammad Hamzah Riaz Muhammad Tang Xiangru Khan Imran Hu Chengxiao 《Plant and Soil》2021,462(1-2):235-244
Plant and Soil - Success in agronomic biofortification of maize and wheat is highly variable. This study aimed to elucidate the differences in uptake and translocation of foliar-applied zinc (Zn)... 相似文献
77.
78.
Sainz B Barretto N Martin DN Hiraga N Imamura M Hussain S Marsh KA Yu X Chayama K Alrefai WA Uprichard SL 《Nature medicine》2012,18(2):281-285
Hepatitis C virus (HCV) is a leading cause of liver disease worldwide. With ~170 million individuals infected and current interferon-based treatment having toxic side effects and marginal efficacy, more effective antivirals are crucially needed. Although HCV protease inhibitors were just approved by the US Food and Drug Administration (FDA), optimal HCV therapy, analogous to HIV therapy, will probably require a combination of antivirals targeting multiple aspects of the viral lifecycle. Viral entry represents a potential multifaceted target for antiviral intervention; however, to date, FDA-approved inhibitors of HCV cell entry are unavailable. Here we show that the cellular Niemann-Pick C1-like 1 (NPC1L1) cholesterol uptake receptor is an HCV entry factor amendable to therapeutic intervention. Specifically, NPC1L1 expression is necessary for HCV infection, as silencing or antibody-mediated blocking of NPC1L1 impairs cell culture-derived HCV (HCVcc) infection initiation. In addition, the clinically available FDA-approved NPC1L1 antagonist ezetimibe potently blocks HCV uptake in vitro via a virion cholesterol-dependent step before virion-cell membrane fusion. Moreover, ezetimibe inhibits infection by all major HCV genotypes in vitro and in vivo delays the establishment of HCV genotype 1b infection in mice with human liver grafts. Thus, we have not only identified NPC1L1 as an HCV cell entry factor but also discovered a new antiviral target and potential therapeutic agent. 相似文献
79.
80.
Rohanah Hussain Christopher L. Joannou Giuliano Siligardi 《International journal of peptide research and therapeutics》2006,12(3):269-273
Microbes are increasingly developing defensive mechanisms against known drugs via mutations. There are signs of emergence of superbugs immune to most known antibiotics available. The need for a new class of drugs to counteract this problem is of paramount importance for continued general well being of mankind. A new class of drugs, antimicrobial peptides, has not been fully exploited primarily due to high cytotoxicity, poor lipophilicity preventing systemic distribution and stability. We have synthesised 9-amino acid residue cationic peptides RH01 and RH02 lipidated with myristoyl and octyl groups respectively. These peptides exhibited potent antimicrobial activity and low cytotoxicity. The lipopeptide RH01 has antimicrobial activity against a broad range of microorganisms including bacteria, yeast and filamentous fungi with greatest activity toward Gram-positive bacteria, including S. aureus MRSA stain, MIC’s ranging between 2–8 μM. The MIC for Gram-negative bacteria was higher ranging from between 30–250 μM. RH01 also had antimicrobial activity towards fungi showing good activity against the pathogenic yeast Candida albicans but was less active towards the filamentous fungi Aspergillus niger. The antimicrobial activity of RH01 as a measure of Ki(50) for E. coli and S. aureus was 35–60 μM and 3–7 μM, respectively. In-house data showed the compound is bactericidal even at higher bacteria concentration. The octylated lipopeptide RH02 has similar activities towards S. aureus (3.3 μM) and E coli (53.3 μM) as the myristolated RH01. There was no haemolytic activity of the lipopeptide RH01 towards human blood. Acute intravenous toxicity study in mice showed that both RH01 and RH02 induced no macroscopic abnormalities at their highest non-lethal dose of 75 mg/kg and 150 mg/kg bodyweight, respectively.Australian Peptide Conference Issue. 相似文献