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991.
Calcium changes and the response to methyl jasmonate in rice lodicules during anthesis 总被引:1,自引:0,他引:1
Summary. Potassium pyroantimonate precipitation was used to locate loosely bound calcium in rice (Oryza sativa L.) lodicules before and after anthesis, and flowering of panicles was accelerated by treatment with methyl jasmonate. From
1 day to 4 h before anthesis, the number of calcium precipitates in the cell walls and vacuole membranes decreased gradually,
whereas they increased remarkably in the cytoplasm and nucleolus. At the beginning of anthesis, the number of calcium granules
in lodicules reduced sharply, but there was a large accumulation of flocculent precipitates in the vacuoles. After anthesis,
the flocculent precipitates decreased in number until they disappeared, whereas the granular precipitates started to accumulate
once again. The rice florets treated with 2 mM methyl jasmonate were induced to open within 10–30 min and they then closed
0.5–1 h later. The nucleolus, cytoplasm, and vacuole membrane of the lodicule cells contained many calcium granules during
flowering, although the cell walls lacked calcium. At 1 h after treatment, the number of calcium granules had decreased, while
flocculent precipitates were regularly observed in the nondegenerated cells. At 6 h after treatment, calcium grains started
to reappear in the cell walls. These changes in calcium precipitates before and after anthesis indicate that the opening and
closing of florets correlates with the calcium level in lodicule cells. In addition, excised panicles, with florets judged
to be nearing anthesis, were soaked in 2–200 mM EGTA solution for 2 min after treatment with 2 mM methyl jasmonate. The results
indicate that EGTA had an antagonistic effect on the methyl jasmonate-induced floret opening in rice.
Correspondence and reprints: Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life
Sciences, Wuhan University, Wuhan 430072, People’s Republic of China. 相似文献
992.
Mechanisms of lysophosphatidic acid-induced increase in intracellular calcium in vascular smooth muscle cells 总被引:3,自引:0,他引:3
Although lysophosphatidic acid (LPA) is known to cause an increase in intracellular Ca2+ concentration ([Ca2+]i) in vascular smooth muscle cells (VSMCs), the mechanisms of [Ca2+]i mobilization by LPA are not fully understood. In the present study, the effect of LPA on [Ca2+]i mobilization in cultured A10 VSMCs was examined by Fura-2 fluorescence technique. The expression of LPA receptors was studied by immunostaining. LPA was observed to increase [Ca2+]i in a concentration-dependent manner; this increase was dependent on the concentration of extracellular Ca2+. Both sarcolemmal (SL) Na(+)-Ca2+ exchange inhibitors (amiloride, Ni2+ and KB-R7943) and Na(+)-H+ exchange inhibitor (MIA) as well as SL store-operated Ca2+ channel (SOC) antagonists (SK&F 96365, tyrphostin A9 and gadolinium), unlike SL Ca2+ channel antagonists (verapamil and diltiazem), inhibited the LPA-induced increase in [Ca2+]i. In addition, sarcoplasmic reticulum (SR) Ca2+ channel blocker (ryanodine), SR Ca2+ channel opener (caffeine), SR Ca2+ pump ATPase inhibitor (thapsigargin) and inositol 1,4,5-trisphosphate (InsP3) receptor antagonists (xestospongin and 2-aminoethoxydiphenyl borate) were found to inhibit the LPA-induced Ca2+ mobilization. Furthermore, phospholipase C (PLC) inhibitor (U 73122) and protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) attenuated the LPA-induced increase in [Ca2+]i. These results indicate that Ca2+ mobilization by LPA involves extracellular Ca2+ entry through SL Na(+)-Ca2+ exchanger, Na(+)-H+ exchanger and SL SOCs. In addition, ryanodine-sensitive and InsP(3)-sensitive intracellular Ca2+ pools may be associated with the LPA-induced increase in [Ca2+]i. Furthermore, the LPA-induced [Ca2+]i mobilization in VSMCs seems to be due to the activation of both PLC and PKC. 相似文献
993.
Saboury AA Atri MS Sanati MH Moosavi-Movahedi AA Haghbeen K 《International journal of biological macromolecules》2005,36(5):305-309
Thermodynamic analysis of calcium ions binding to human growth hormone (hGH) was done at 27 °C in NaCl solution, 50 mM, using different techniques. The binding isotherm for hGH-Ca2+ was obtained by two techniques of ionmetry, using a Ca2+-selective membrane electrode, and isothermal titration calorimetry. Results obtained by two ionmetric and calorimetric methods are in good agreement. There is a set of three identical and non-interacting binding sites for calcium ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 52 μM and −17.4 kJ/mol, respectively. Temperature scanning UV–vis spectroscopy was applied to elucidate the effect of Ca2+ binding on the protein stability, and circular dichroism (CD) spectroscopy was used to show the structural change of hGH due to the metal ion interaction. Calcium ions binding increase the protein thermal stability by increasing of the alpha helix content as well as decreasing of both beta and random coil structures. 相似文献
994.
Chinopoulos C Starkov AA Grigoriev S Dejean LM Kinnally KW Liu X Ambudkar IS Fiskum G 《Journal of bioenergetics and biomembranes》2005,37(4):237-247
Mitochondria contribute to cytosolic Ca2+ homeostasis through several uptake and release pathways. Here we report that 1,2-sn-diacylglycerols (DAGs) induce Ca2+ release from Ca2+-loaded mammalian mitochondria. Release is not mediated by the uniporter or the Na+/Ca2+ exchanger, nor is it attributed to putative catabolites. DAGs-induced Ca2+ efflux is biphasic. Initial release is rapid and transient, insensitive to permeability transition inhibitors, and not accompanied by mitochondrial swelling. Following initial rapid release of Ca2+ and relatively slow reuptake, a secondary progressive release of Ca2+ occurs, associated with swelling, and mitigated by permeability transition inhibitors. The initial peak of DAGs-induced Ca2+ efflux is abolished by La3+ (1 mM) and potentiated by protein kinase C inhibitors. Phorbol esters, 1,3-diacylglycerols and 1-monoacylglycerols do not induce mitochondrial Ca2+ efflux. Ca2+-loaded mitoplasts devoid of outer mitochondrial membrane also exhibit DAGs-induced Ca2+ release, indicating that this mechanism resides at the inner mitochondrial membrane. Patch clamping brain mitoplasts reveal DAGs-induced slightly cation-selective channel activity that is insensitive to bongkrekic acid and abolished by La3+. The presence of a second messenger-sensitive Ca2+ release mechanism in mitochondria could have an important impact on intracellular Ca2+ homeostasis. 相似文献
995.
We investigated the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, and Hf)
and the effect of Ca on their uptake in carrots (Daucus carota cv. U.S. harumakigosun) by the radioactive multitracer technique. The experimental results suggested that Na, Mg, K, and
Rb competed for the functional groups outside the cells in roots with Ca but not for the transporter-binding sites on the
plasma membrrane of the root cortex cells. In contrast, Y, Ce, Pm, and Gd competed with Ca for the transporters on the plasma
membrane. The selectivity, which was defined as the value obtained by dividing the concentration ratio of an elemental pair,
K/Na, Rb/Na, Be/Sr, and Mg/Sr, in the presence of 0.2 and 2 ppm Ca by that of the corresponding elemental pair in the absence
of Ca in the solution was estimated. The selectivity of K and Rb in roots was increased in the presence of Ca. The selectivity
of Be in roots was not affected, whereas the selectivity of Mg was increased by Ca. These observations suggest that the presence
of Ca in the uptake solution enhances the selectivity in the uptake of metabolically important elements against unwanted elements. 相似文献
996.
Although increasing evidence shows the nutritional benefits of calcium fructoborate (CF) on animals and humans, its action
mechanism has not been clearly identified. The present study aims to investigate the possible antioxidant function of CF.
Based on its efficiency in skin wound healing, the authors tested whether CF possesses antioxidant properties on human keratinocytes
cultures, in a complete serum-free medium (KMK-2; Sigma). The cells treated with CF (0–450 nmol/culture medium) were exposed
to exogenous 100 μmol of hydrogen peroxide to mimic the oxidative stress. The changes in general cell oxidant production evaluated
with dihydrorhodamine-123 showed that the intracellular reactive oxygen species (ROS) were markedly reduced by preincubation
with CF. The maximum antioxidant activity was notice at 90 nmol CF. To assess the reactivity of CF on ROS, we analyzed its
ability to inhibit the superoxide-dependent auto-oxidation of pyrogallol. The CF inhibited the pyrogallol auto-oxidation depending
on time and concentration, which suggests its possible role as a superoxide radical scavenger. Taken together, our results
indicate that CF has antioxidant activity, which could have clinical significance in protecting cells from oxidant-induced
injury. A hypothetic mechanism for the antioxidant activity of CF is proposed. 相似文献
997.
Haider MZ Habeeb Y Al-Nakkas E Al-Anzi H Zaki M Al-Tawari A Al-Bloushi M 《Journal of biomedical science》2005,12(5):815-818
Summary Idiopathic generalized epilepsies (IGEs) are the most common types of epilepsy in childhood and adolescence. A variety of
data suggest that IGEs have a predominant genetic etiology. Recently, a number of gene mutations have been found to be associated
with various types of epilepsy in mainly the Caucasian populations. The objective of this study was to investigate the association
of three different candidate genes with IGE in Kuwaiti Arab children. This study includes 123 Kuwaiti patients with a confirmed
diagnosis of epilepsy. Most of the patients have had a diagnostic EEG with generalized spike-wave discharges (GSWs). All patients
were evaluated by using a validated seizure questionnaire. The clinical type of epilepsy was determined by a trained neurologist/pediatrician.
The study also include 100 controls, the control subjects were children which did not have any history of neurological disorders.
Blood samples were collected from all patients and control subjects after taking informed consent. DNA was isolated and analyzed
by molecular methods. A FokI polymorphism in neuronal nicotinic acetylcholine receptor alpha-4 subunit (CHRNA4) gene was detected by PCR-RFLP method.
A missense mutation (Ser248Phe) in CHRNA4 gene was analyzed by PCR-RFLP using HpaII. A C121W mutation in sodium-channel beta-1 subunit (SCN1B) gene was screened by a PCR-RFLP method using HinPI. A 2-bp deletion in Cystatin B gene was detected by PCR-RFLP using XcmI. The incidence of three FokI polymorphism genotypes in Kuwaiti IGE patients was 1,1 (85%), 1,2 (14%) and 2,2 (1%) respectively. The missense mutation
Ser248Phe of CHRNA4 gene was not detected at all in Kuwaiti IGE patients. The C387G transversion resulting in C121W change
in third exon of the SCN1B gene was detected in 3/123 patients (2%). The patients carrying this mutation also exhibited febrile
seizures. The incidence of 2 bp deletion in the cystatin B gene was found to be 4% (5/123 IGE patients). The data obtained
from molecular analysis show a lack of association between three candidate genes and clinical expression of IGE in Kuwaiti
Arab children. This is completely different from the findings reported from Caucasian populations of France, Australia and
USA in which case a strong association has been reported between IGE and these genes.
To whom corresspondence should be addressed. Tel: +965-5319486; Fax: +965-5338940; E-mail: haider@hsc.edu.kw 相似文献
998.
Calcium signaling system in plants 总被引:4,自引:0,他引:4
S. S. Medvedev 《Russian Journal of Plant Physiology》2005,52(2):249-270
999.
The role of anion channels and Ca2+ in addition to K+ channels in the physiological volume regulation of murine spermatozoa 总被引:1,自引:0,他引:1
Studies in the human, transgenic mice, and cattle indicate that sperm cell volume regulation plays an important role in male fertility as spermatozoa encounter a hypo-osmotic challenge upon ejaculation into the female tract. Physiological regulatory volume decrease (RVD) was examined using flow cytometry in murine sperm released into incubation medium mimicking uterine osmolality and including putative channel inhibitors. The involvement of K+ channels was indicated by the recovery of volume regulation by the K+ ionophore valinomycin in defective sperm from infertile transgenic mice, and from blockage of RVD by quinine in normal sperm. However, in neither case was the recovery complete. The involvement of volume-sensitive osmolyte and anion channels (VSOAC) were investigated using blockers effective in other cell types. NPPB (5-nitro-2(3-phenylpropylamino) benzoic acid) and tamoxifen inhibited RVD but SITS (4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulphonic acid) at 0.4 and 1 mM had no effect whereas DIDS (di-isothiocyanato-stilbene-2,2'-disulphonic acid) at 1 mM enhanced RVD. Verapamil, but not another P-glycoprotein antagonist cyclosporin, caused sperm swelling which persisted in the presence of valinomycin, in Ca2+-free medium and in the presence of thapsigargin, but swelling was abolished by the Ca2+ ionophore A23187. Nifedipine was slightly effective in blocking RVD. Analysis by Western blotting failed to reveal ClC-2 and ClC-3 members of the chloride channel family in murine or rat sperm proteins despite signal bands in positive tissue controls. These findings implicate the involvement of some unidentified VSOAC in sperm volume regulation, which is probably Ca+-dependent. 相似文献
1000.
Miranda K Vercesi AE Catisti R De Souza W Rodrigues CO Docampo R 《The Journal of eukaryotic microbiology》2005,52(1):55-60
The use of digitonin to permeabilize the plasma membrane of promastigotes of Phytomonas francai allowed the identification of two non-mitochondrial Ca(2+) compartments; one sensitive to ionomycin and vanadate (neutral or alkaline), possibly the endoplasmic reticulum, and another sensitive to the combination of nigericin plus ionomycin (acidic), possibly the acidocalcisomes. A P-type (phospho-intermediate form) Ca(2+)-ATPase activity was found to be responsible for intracellular Ca(2+) transport in these cells, with no evidence of a mitochondrial Ca(2+) transport activity. ATP-driven acidification of internal compartments in cell lysates and cells mechanically permeabilized was assayed spectrophotometrically with acridine orange. This activity was inhibited by low concentrations of vanadate and digitonin, was insensitive to bafilomycin A(1), and stimulated by Na(+) ions. Taken together, our results indicate that P-type ATPases are involved in intracellular Ca(2+) and H(+) transport in promastigotes of P. francai. 相似文献