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121.
Kumar A Dasaradhi PV Chauhan VS Malhotra P 《Biochemical and biophysical research communications》2004,317(1):38-45
Falcipain-2 is one of the principal hemoglobinases of Plasmodium falciparum, a human malaria parasite. It has a typical papain family cysteine protease structural organization, a large pro-domain, a mature domain with conserved active site amino acids. Pro-domain of falcipain-2 also contains two important conserved motifs, "GNFD" and "ERFNIN." The "GNFD" motif has been shown to be responsible for correct folding and stability in case of many papain family proteases. In the present study, we carried out site-directed mutagenesis to assess the roles of active site residues and pro-domain residues for the activity of falcipain-2. Our results showed that substitutions of putative active site residues; Q36, C42, H174, and N204 resulted in complete loss of falcipain-2 activity, while W206 and D155 mutants retained partial/complete activity in comparison to the wild type falcipain-2. Homology modeling data also corroborate the results of mutagenesis; Q36, C42, H174, N204, and W206 residues form the active site loop of the enzyme and D155 lie outside the active pocket. Substitutions in the pro-region did not affect the activity of falcipain-2. This implies that falcipain-2 shares active site residues with other members of papain family, however pro-region of falcipain-2 does not play any role in the activity of enzyme. 相似文献
122.
Immune responses to asexual blood-stages of malaria parasites 总被引:6,自引:0,他引:6
The blood stage of the malaria parasite's life cycle is responsible for all the clinical symptoms of malaria. The development of clinical disease is dependent on the interplay of the infecting parasite with the immune status and genetic background of the host. Following repeated exposure to malaria parasites, individuals residing in endemic areas develop immunity. Naturally acquired immunity provides protection against clinical disease, especially severe malaria and death from malaria, although sterilizing immunity is never achieved. Given the absence of antigen processing in erythrocytes, immunity to blood stage malaria parasites is primarily conferred by humoral immune responses. Cellular and innate immune responses play a role in controlling parasite growth but may also contribute to malaria pathology. Here, we analyze the natural humoral immune responses acquired by individuals residing in P. falciparum endemic areas and review their role in providing protection against malaria. In addition, we review the dual potential of cellular and innate immune responses to control parasite multiplication and promote pathology. 相似文献
123.
Prashant Singh Chauhan Naresh Kumar Satti Krishan Avtar Suri Musarat Amina Sarang Bani 《Chemico-biological interactions》2010,185(1):66-72
Many herbs and spices are known to modulate the immune system and have been shown to restore the immunity in immuno-compromised individuals. Spices generally used to increase the taste and flavor of food also has the history of usage as an ayurvedic medicine. Therefore to explore the health modulating effects of Cuminum cyminum and to identify the active compound, immunomodulatory properties were evaluated using flowcytometry and ELISA in normal and immune-suppressed animals. C. cyminum and compound 1 stimulated the T cells and Th1 cytokines expression in normal animals. Swiss albino mice subjected to Cyclosporine-A induced immune-suppression were dosed orally with C. cyminum (25, 50, 100 and 200 mg/kg) on consecutive days. The results showed that administration significantly increased T cells (CD4 and CD8) count and Th1 predominant immune response in a dose dependent manner thereby suggesting immunomodulatory activity through modulation of T lymphocytes expression. In restraint stress induced immune-suppressed animals, compound 1 countered the depleted T lymphocytes, decreased the elevated corticosterone levels and size of adrenal glands and increased the weight of thymus and spleen. Based on the data we may conclude that C. cyminum is a potent immunomodulator and may develop as a lead to recover the immunity of immuno-compromised individuals. 相似文献
124.
125.
Mycobacterium tuberculosis cells growing in macrophages are filamentous and deficient in FtsZ rings
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Chauhan A Madiraju MV Fol M Lofton H Maloney E Reynolds R Rajagopalan M 《Journal of bacteriology》2006,188(5):1856-1865
FtsZ, a bacterial homolog of tubulin, forms a structural element called the FtsZ ring (Z ring) at the predivisional midcell site and sets up a scaffold for the assembly of other cell division proteins. The genetic aspects of FtsZ-catalyzed cell division and its assembly dynamics in Mycobacterium tuberculosis are unknown. Here, with an M. tuberculosis strain containing FtsZ(TB) tagged with green fluorescent protein as the sole source of FtsZ, we examined FtsZ structures under various growth conditions. We found that midcell Z rings are present in approximately 11% of actively growing cells, suggesting that the low frequency of Z rings is reflective of their slow growth rate. Next, we showed that SRI-3072, a reported FtsZ(TB) inhibitor, disrupted Z-ring assembly and inhibited cell division and growth of M. tuberculosis. We also showed that M. tuberculosis cells grown in macrophages are filamentous and that only a small fraction had midcell Z rings. The majority of filamentous cells contained nonring, spiral-like FtsZ structures along their entire length. The levels of FtsZ in bacteria grown in macrophages or in broth were comparable, suggesting that Z-ring formation at midcell sites was compromised during intracellular growth. Our results suggest that the intraphagosomal milieu alters the expression of M. tuberculosis genes affecting Z-ring formation and thereby cell division. 相似文献
126.
Kumar R Tripathi V Ahmad M Nath N Mir RA Chauhan SS Luthra K 《Cellular immunology》2012,272(2):230-241
Chemokine receptors CXCR7 and CXCR4 bind to the same ligand stromal cell derived factor-1alpha (SDF-1α/CXCL12). We assessed the downstream signaling pathways mediated by CXCL12-CXCR7 interaction in Jurkat T cells. All experiments were carried out after functionally blocking the CXCR4 receptor. CXCL12, on binding CXCR7, induced phosphorylation of extra cellular regulated protein kinases (ERK 1/2) and Akt. Selective inhibition of each signal demonstrated that phosphorylated ERK 1/2 is essential for chemotaxis and survival of T cells whereas activation of Akt promotes only cell survival. Another interesting finding of this study is that CXCL12-CXCR7 interaction under normal physiological conditions does not activate the p38 pathway. Furthermore, we observed that the CXCL12 signaling via CXCR7 is Giα independent. Our findings suggest that CXCR7 promotes cell survival and does not induce cell death in T cells. The CXCL12 signaling via CXCR7 may be crucial in determining the fate of the activated T cells. 相似文献
127.
S. P. Tiwari Deepika Yadav Pradeep Kumar D. K. Chauhan 《Plant Systematics and Evolution》2012,298(4):723-730
A comparative study of Taxodium distichum
(L.) Rich. and Taxodium mucronatum
Ten. was carried out on the basis of pollen morphology and wood anatomy by light and scanning electron microscopy. We describe
a detailed analysis of the anatomical characteristics of the wood, including the tracheids, ray parenchyma, axial parenchyma
and number of cross-field pits. Palynological characters were also studied to reveal the shape, size and ultrastructure of
the pollen grains. These studies give taxonomic support for the recognition of T. distichum and T. mucronatum as two different species. 相似文献
128.
Ahmadi F McLoughlin IV Chauhan S ter-Haar G 《Progress in biophysics and molecular biology》2012,108(3):119-138
Low-frequency (LF) ultrasound (20-100 kHz) has a diverse set of industrial and medical applications. In fact, high power industrial applications of ultrasound mainly occupy this frequency range. This range is also used for various therapeutic medical applications including sonophoresis (ultrasonic transdermal drug delivery), dentistry, eye surgery, body contouring, the breaking of kidney stones and eliminating blood clots. While emerging LF applications such as ultrasonic drug delivery continue to be developed and undergo translation for human use, significant gaps exist in the coverage of safety standards for this frequency range. Accordingly, the need to understand the biological effects of LF ultrasound is becoming more important. This paper presents a broad overview of bio-effects and safety of LF ultrasound as an aid to minimize and control the risk of these effects. Its particular focus is at low intensities where bio-effects are initially observed. To generate a clear perspective of hazards in LF exposure, the mechanisms of bio-effects and the main differences in action at low and high frequencies are investigated and a survey of harmful effects of LF ultrasound at low intensities is presented. Mechanical and thermal indices are widely used in high frequency diagnostic applications as a means of indicating safety of ultrasonic exposure. The direct application of these indices at low frequencies needs careful investigation. In this work, using numerical simulations based on the mathematical and physical rationale behind the indices at high frequencies, it is observed that while thermal index (TI) can be used directly in the LF range, mechanical index (MI) seems to become less reliable at lower frequencies. Accordingly, an improved formulation for the MI is proposed for frequencies below 500 kHz. 相似文献
129.
Durgesh Kumar Tripathi Vijay Pratap Singh Dharmendra Kumar Devendra Kumar Chauhan 《Acta Physiologiae Plantarum》2012,34(1):279-289
Hydroponic experiments were conducted to investigate the role of exogenous silicon (Si) addition in increasing hexavalent
chromium (Cr VI) tolerance in rice seedlings. Rice seedlings were grown under 100 μM Cr(VI) stress without or with 10 μM Si.
Chromium treatment decreased growth, photosynthetic pigments and protein, which was accompanied by a significant increase
in Cr accumulation and lipid peroxidation (as malondialdehyde; MDA). However, Si addition alleviated Cr toxicity and promoted
growth of rice by decreasing Cr accumulation, root-to-shoot Cr transport and MDA level. Contents of macro (Mg, Ca and K) as
well as micronutrients (Zn and Fe) were decreased by Cr except Mn while Si addition prevented decrease in these nutrients
induced by Cr. Antioxidant capacity and total phenolic contents were decreased by Cr while these indices improved by Si addition.
Treatment of Cr decreased the length of leaf epidermal cells and stomatal frequency, and adversely affected chloroplasts containing
mesophyll cells and integrity of xylem and phloem, and Si addition minimized these abnormalities. However, frequency of root
hairs was increased by Cr treatment. Results showed that exogenous Si addition enhanced Cr(VI) tolerance in rice seedlings
by decreasing Cr accumulation, root-to-shoot Cr transport and MDA level, and by increasing content of some mineral elements
(K, Fe and Zn) and antioxidant capacity compared to the Cr treatment alone. 相似文献
130.