全文获取类型
收费全文 | 819篇 |
免费 | 41篇 |
国内免费 | 1篇 |
出版年
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 10篇 |
2015年 | 14篇 |
2014年 | 25篇 |
2013年 | 81篇 |
2012年 | 41篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 19篇 |
2008年 | 30篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1971年 | 12篇 |
1970年 | 8篇 |
1969年 | 7篇 |
1968年 | 9篇 |
1967年 | 6篇 |
1960年 | 5篇 |
排序方式: 共有861条查询结果,搜索用时 24 毫秒
71.
P. K. Sarma, A. K. Chowhan, V. Agrawal and V. Agarwal Fine needle aspiration cytology in HIV‐related lymphadenopathy: experience at a single centre in north India Objective: Fine needle aspiration (FNA) is emerging as a rapid and minimally invasive tool in evaluating lymphadenopathy associated with human immunodeficiency virus (HIV). We evaluated the role of FNA in differentiating various causes of lymphadenopathy in patients with HIV and correlated the cytological diagnosis with CD4 counts. Methods: Seventy‐nine HIV‐positive patients (median age 35 years, 68 male) underwent ultrasound‐guided (n = 16) and unguided (n = 63) FNA from 1999 to 2006. Smears were stained with May–Grünwald–Giemsa, haematoxylin & eosin and Papanicolaou stains. Ziehl–Neelsen (ZN) staining for acid‐fast bacilli (AFB) was performed in all cases. Staining for fungus was performed whenever required. Results: The aspirates were adequate in 75 cases (95%). Non‐specific reactive hyperplasia was the most common FNA diagnosis (39, 52%) followed by granulomatous necrotizing lymphadenitis (15, 20%), necrotizing lymphadenitis (13, 17.3%) and granulomatous lymphadenitis (4, 5.2%). Fungal infection and non‐Hodgkin lymphoma (NHL) were seen in two patients each. ZN staining was positive for AFB in 25 (33.3%) cases. One of these was morphologically interpreted as reactive hyperplasia, 12 as necrotizing lymphadenitis and 12 as granulomatous necrotizing lymphadenitis. Both patients with NHL had CD4 counts below 100/dl. Necrotizing lymphadenitis and granulomatous lymphadenitis were significantly associated with CD4 counts below and above 200/dl, respectively (P = 0.0002). Conclusions: FNA is an important tool for assessing the cause of lymphadenopathy in HIV patients. Necrotizing inflammation is more often seen in patients with low CD4 counts. AFB are commonly found in necrotic aspirates with or without granulomas. However, a stain for AFB should be performed in all aspirates from HIV‐related lymphadenopathy including reactive hyperplasia. 相似文献
72.
We studied the response of Brachionus patulus to different concentrations of the heavy metal Pb in the presence and absence of sediments. We conducted acute (LC50) and chronic (life table demography and population growth) toxicity tests using sediment levels of 0, 30 and 280 mg l−1 (=0, 17 and 170 NTU) and Pb at 0, 0.06 and 0.6 mg l−1. Experiments were conducted at 20 ± 1°C on a horizontal shaker and algal food (Chlorella vulgaris) was added at a density of 1.0 × 106 cells ml−1. The median lethal concentration (LC50 ± 95% Confidence intervals) of PbCl2 for B. patulus was 6.15 ± 1.08 mg l−1. Age-specific survivorship and fecundity curves showed increase in turbidity level resulted in decreased survival and offspring
production of the rotifers. Increase in Pb concentration too had a negative effect on the survival and reproductive output
of B. patulus. Statistically, average lifespan, life expectancy at birth, gross and net reproductive rates and the rate of population increase
were all significantly influenced by the concentration of Pb, turbidity level as well as the interaction of Pb concentration × turbidity
level. Rotifers exposed to 170 NTU did not grow regardless of the heavy metal concentration in the medium. Similarly, B. patulus exposed to 0.6 mg l−1 Pb did not survive beyond 10 days regardless of the turbidity level in the medium. The rate of population increase of B. patulus derived from the growth experiments was negative in all treatments containing Pb as low as 0.06 mg l−1 or turbidity level as low as 17 NTU. In treatments containing Pb or sediments, there existed no relation between the egg
ratio and the population density.
Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont and R. Rico-Martínez
Advances in Rotifer Research 相似文献
73.
Jose Luis Gama-Flores Maria Elena Castellanos-Paez S. S. S. Sarma S. Nandini 《Hydrobiologia》2007,593(1):201-208
Heavy metals are widely recognized as potential toxic agents to zooplankton, yet experiments are usually performed with a
continuous exposure to the metal being analyzed. Here we describe experiments that examined the influence of pulsed exposure
of the heavy metals copper and cadmium to a parthenogenetic population of the planktonic rotifer Brachionus calyciflorus. Our protocol called for exposure durations of 3, 6, 12, and 24 h to either copper (as CuSO4) at concentrations of 0.0375, 0.075, 0.15 mg l−1 or cadmium (as CdCl2) at concentration of 0.025, 0.05, 0.1 mg l−1. Control animals were treated in similar ways but did not receive exposure to heavy metals. Four end points were used to
evaluate the outcome of exposure: population growth (r), body size, egg ratio, and egg hatching percent. Increase in heavy metal concentration and exposure time had an adverse
influence on the population growth of B. calyciflorus. However, while the response of B. calyciflorus was similar for both heavy metals, the magnitude of the impact of cadmium was more severe. Population growth varied depending
on which heavy metal was tested, as well as its concentration and the duration of exposure (r = 0.11–0.28 day−1). There was a significant reduction in lorica size of B. calyciflorus subjected to different exposure times and concentrations of both Cd and Cu. Egg ratios were inversely related to population
density in controls and in treatments involving Cu, but not for Cd. While nearly 100% of eggs hatched in the control treatments,
egg hatching in experimental treatments containing Cu, were reduced (range = 16–41%) depending on the exposure time and the
concentration.
Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez
Advances in Rotifer Research 相似文献
74.
Influence of recirculation on the performance of anaerobic sequencing batch biofilm reactor (AnSBBR) was studied in the process of treating hypersaline (total dissolved inorganic solids (TDIS) approximately 26 g/l) and low biodegradable (BOD/COD approximately 0.3) composite chemical wastewater. Significant enhancement in the substrate removal efficiency and biogas yield was observed after introducing the recirculation to the system. Maximum efficiency (COD removal efficiency - 51%; SDR - 3.14 kg COD/cum-day) was observed at recirculation to feed (R/F) ratio of 2 (OLR - 6.15 kg C OD/cum-day; HLR - 2.30 cum (liquid)/cum day; UFV(A) - 0.023 m/h). Subsequent increase of R/F to 3 (OLR - 6.15 kg COD/cum-day; HLR - 3.07cum (liquid)/cum-day; UFV(A) - 0.035 m/h) resulted in reduction in COD removal efficiency (32%; SDR - 1.97 kg COD/cum-day). The enhanced performance of the system due to the introduction of recirculation was attributed to the improvement in the mass transfer between the substrate present in the bulk liquid and the attached biofilm. The hydrodynamic behavior due to recirculation mode of operation reduced the concentration gradient (substrate inhibition) of substrate and reaction by-products (VFA) resulting in mixed flow conditions. 相似文献
75.
Prevalence of duodenal ulcer-promoting gene (dupA) of Helicobacter pylori in patients with duodenal ulcer in North Indian population 总被引:1,自引:0,他引:1
Arachchi HS Kalra V Lal B Bhatia V Baba CS Chakravarthy S Rohatgi S Sarma PM Mishra V Das B Ahuja V 《Helicobacter》2007,12(6):591-597
BACKGROUND: The duodenal ulcer (DU)-promoting gene (dupA) of Helicobacter pylori has been identified as a novel virulent marker associated with an increased risk for DU. The presence or absence of dupA gene of H. pylori present in patients with DU and functional dyspepsia in North Indian population was studied by polymerase chain reaction (PCR) and hybridization analysis. MATERIALS AND METHODS: One hundred and sixty-six patients (96 DU and 70 functional dyspepsia) were included in this study. In addition, sequence diversity of dupA gene of H. pylori found in these patients was analyzed by sequencing the PCR products jhp0917 and jhp0918 on both strands with appropriate primers. RESULTS: PCR and hybridization analyses indicated that dupA gene was present in 37.5% (36/96) of H. pylori strains isolated from DU patients and 22.86% (16/70) of functional dyspepsia patients (p < or = .05). Of these, 35 patients with DU (97.2%) and 14 patients with functional dyspepsia (81.25%) were infected by H. pylori positive for cagA genotype. Furthermore, the presence of dupA was significantly associated with the cagA-positive genotype (p < or = .02). CONCLUSION: Results of our study have shown that significant association of dupA gene with DU in this population. The dupA gene can be considered as a novel virulent marker for DU in this population. 相似文献
76.
Tulika Sarma Athanasia Koutsouris Jiang Zhu Yu Aleksandar Krbanjevic Thomas J. Hope Mark M. Rasenick 《The Journal of biological chemistry》2015,290(16):10045-10056
Signals that activate the G protein Gαs and promote neuronal differentiation evoke Gαs internalization in rat pheochromocytoma (PC12) cells. These agents also significantly increase Gαs association with microtubules, resulting in an increase in microtubule dynamics because of the activation of tubulin GTPase by Gαs. To determine the function of Gαs/microtubule association in neuronal development, we used real-time trafficking of a GFP-Gαs fusion protein. GFP-Gαs concentrates at the distal end of the neurites in differentiated living PC12 cells as well as in cultured hippocampal neurons. Gαs translocates to specialized membrane compartments at tips of growing neurites. A dominant-negative Gα chimera that interferes with Gαs binding to tubulin and activation of tubulin GTPase attenuates neurite elongation and neurite number both in PC12 cells and primary hippocampal neurons. This effect is greatest on differentiation induced by activated Gαs. Together, these data suggest that activated Gαs translocates from the plasma membrane and, through interaction with tubulin/microtubules in the cytosol, is important for neurite formation, development, and outgrowth. Characterization of neuronal G protein dynamics and their contribution to microtubule dynamics is important for understanding the molecular mechanisms by which G protein-coupled receptor signaling orchestrates neuronal growth and differentiation. 相似文献
77.
78.
Kamal A Reddy MK Ramaiah MJ Rajender Reddy JS Srikanth YV Dastagiri D Bharathi EV Pushpavalli SN Sarma P Pal-Bhadra M 《Bioorganic & medicinal chemistry》2011,19(8):2565-2581
A series of new estradiol linked pyrrolo[2,1-c][1,4]benzodiazepine (E(2)-PBD) conjugates (3a-f, 4a-f and 5a-f) with different linker architectures including a triazole moiety have been designed and synthesized. All the 18 compounds have been evaluated for their anticancer activity and it is observed that some of the compounds particularly 4c-e and 5c,d exhibited significant anticancer activity. The detailed biological aspects relating to the cell cycle effects and tubulin depolymerization activity have been examined with a view to understand the mechanism of action of these conjugates. Among all these conjugates, one of the compound 5c could be considered as the most effective compound particularly against MCF-7 breast cancer cell line. 相似文献
79.
Aspergillus fumigatus is an opportunistic fungus which causes pulmonary complications in humans and animals. The clinical spectrum observed with A. fumigatus is attributed to the multifunctional nature of its antigens. Lack of understanding on the molecular processes and complexity of the fungus have spurred interest in the identification and characterization of its antigens/allergens with biological activities and virulence functions. For identification of some of these antigens/allergens, a cDNA library of A. fumigatus was screened with antibodies of allergic bronchopulmonary aspergillosis (ABPA) patients. One of the reactive clones was sequenced and observed to have an open reading frame of 1095 nucleotides corresponding to a polypeptide of 364 amino acids. The nucleotide and deduced amino acid sequence showed significant homology with the protein disulfide isomerase (PDI) superfamily. The expressed recombinant fusion protein exhibited specific IgG and IgE binding with antibodies present in ABPA patients' sera. The recombinant protein in vitro catalyzed folding of scrambled RNase. The probable epitopic regions of the deduced amino acid sequence were mapped by algorithmic analysis. This is the first report of isolation of a gene encoding a member of the PDI family from A. fumigatus. The PDI superfamily of proteins may play an important role in the protein folding mechanisms of A. fumigatus antigens/allergens for their interaction with the host. 相似文献
80.
Kamal N Chowdhury S Madan T Sharma D Attreyi M Haq W Katti SB Kumar A Sarma PU 《Molecular and cellular biochemistry》2005,275(1-2):223-231
The role of tryptophan (Trp17) in immunoreactivity of P1, the diagnostically relevant peptide from a major allergen/antigen of Aspergillus fumigatus, was evaluated by chemically modifying tryptophanyl residue of P1. In BIAcore kinetic studies, unmodified P1 showed a 100-fold higher binding with ABPA (Allergic Bronchopulmonary Aspergillosis) patients’ IgG [KD (equilibrium dissociation constant) = 2.74 e−8 ± 0.13 M] than the controls’ IgG (KD = 2.97 e−6± 0.14 M), whereas chemically-modified P1 showed similar binding [KD patients’ IgG = 3.25 e−7± 0.16 M, KD controls’ IgG = 3.86 e−7± 0.19 M] indicating loss of specific immunoreactivity of P1 on tryptophan modification. Modified P1 showed loss of specific binding to IgE and IgG antibodies of ABPA patients in ELISA (Enzyme-Linked Immunosorbent Assay). The study infers that tryptophan residue (Trp17) is essential for immunoreactivity of P1. 相似文献