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71.
Bovine kidneys were found to contain about 78 ppm Zn and 0.78 ppm Cd. Approximately 45% of Zn and 60% of Cd were present in
the cytosol fraction. More than 95% of these two metals were bound to macromolecules. Both Zn- and Cd-protein complexes were
observed to be stable between pH 7 and 10.5. Separation and characterization of these proteins were carried out using several
chromatographic and electrophoretic techniques in conjunction with instrumental neutron activation analysis (INAA). The results
showed the presence of at least four Zn-binding proteins with mol wt>300,000, 260,000, 89,000, and 27,000 and at least three
Cd-binding proteins of mol wt>300,000, 32,000, and 13,000. 相似文献
72.
An epithermal neutron activation method is used to determine the concentration of mineral elements in human dental enamel.
A large number (252) of samples from ancient and modern origins are analyzed. The analytical results are mathematically processed
using a statistical multivariant method. This allows to differentiate deciduous from permanent teeth and decayed from sound
enamel. It is also possible to distinguish the teeth coming from two different necropoles. The origin and the localization
of determined elements in the mineralized part, or in the aqueous-organic part, of enamel is suggested. Their role, as witnessed
in the physiopathological phenomena of dental enamel, is discussed. 相似文献
73.
The major developments in the field of nuclear activation analysis, from 1936 to 1989, are discussed. The developments are
grouped into five consecutive time periods. The impact of various scientists on the development of the field in the first
35 years is also discussed. 相似文献
74.
By indirect immunofluorescence, using rabbit anti-heparin-binding placental protein (HBPP) antiserum, we studied HBPP expression by physiologically and non-physiologically (microsurgically) activated hamster gametes. Whereas mature gametes (sperm, metaphase II oocytes) were negative, in vivo conceived preimplantation embryos, from pronuclear to two- and four-cell stages, were HBPP positive. No HBPP was demonstrated in the zona pellucida, but HBPP-dependent immunofluorescence was localized in the perivitelline space. Oocytes incubated with hyaluronidase demonstrated variable responses from negative to positive. (Diluent or sperm) microinjected oocytes were all activated and HBPP positive within 4 h after stimulation. Thus neither activation by microinjection nor HBPP expression required paternal gametes. These kinetics suggest that HBPP may be a cortical granule secretogogue which can be applied to monitor oocyte responses during in vitro manipulations. 相似文献
75.
There is increasing evidence that Ca2+ release from sarcoplasmic reticulum (SR) of mammalian skeletal muscle is regulated or modified by several factors including
ionic composition of the myoplasm. We have studied the effect of Cl− on the release of Ca2+ from the SR of rabbit skeletal muscle in both skinned psoas fibers and in isolated terminal cisternae vesicles. Ca2+ release from the SR in skinned fibers was inferred from increases in isometric tension and the amount of release was assessed
by integrating the area under each tension transient. Ca2+ release from isolated SR was measured by rapid filtration of vesicles passively loaded with 45Ca2+. Ca2+ release from SR was stimulated in both preparations by exposure to a solution containing 191 mm choline-Cl, following pre-equilibration in Ca2+-loading solution that had propionate as the major anion. Controls using saponin (50 μg/ml), indicated that the release of
Ca2+ was due to direct action of Cl− on the SR rather than via depolarization of T-tubules. Procaine (10 mm) totally blocked Cl−- and caffeine-elicited tension transients recorded using loading and release solutions having ([Na+] + [K+]) × [Cl−] product of 6487.69 mm
2 and 12361.52 mm
2, respectively, and blocked 60% of Ca2+ release in isolated SR vesicles. Surprisingly, procaine had only a minor effect on tension transients elicited by Cl− and caffeine together. The data from both preparations suggests that Cl− induces a relatively small amount of Ca2+ release from the SR by activating receptors other than RYR-1. In addition, Cl− may increase the Ca2+ sensitivity of RYR-1, which would then allow the small initial release of Ca2+ to facilitate further release of Ca2+ from the SR by Ca2+-induced Ca2+ release.
Received: 6 February 1996/Revised: 17 July 1996 相似文献
76.
Swelling and Ca2+-activated Anion Conductances in C127 Epithelial Cells Expressing WT and ΔF508-CFTR
CFTR is a chloride channel that is required for fluid secretion and salt absorption in many exocrine epithelia. Mutations
in CFTR cause cystic fibrosis. CFTR expression influences some ion channels, but the range of channels influenced, the mechanism
of the interaction and the significance for cystic fibrosis are not known. Possible interactions between CFTR and other ion
channels were studied in C127 mouse mammary epithelial cell lines stably transfected with CFTR, ΔF508-CFTR, or vector. Cell
lines were compared quantitatively using an 125I efflux assay and qualitatively using whole-cell patch-clamp recording. As expected, 125I efflux was significantly increased by forskolin only in the CFTR line, and forskolin-stimulated whole-cell currents were
time- and voltage independent. All three lines responded to hypotonic challenge with large 125I efflux responses of equivalent magnitude, and whole-cell currents were outwardly rectified and inactivated at positive voltages.
Unexpectedly, basal 125I efflux was significantly smaller in the ΔF508-CFTR cell line than in either the CFTR or control cell lines (P < 0.0001), and the magnitude of the efflux response to ionomycin was largest in the vector cell line and smallest in the
cell line expressing ΔF508-CFTR (P < 0.01). Whole-cell responses to ionomycin had a linear instantaneous I-V relation and activated at depolarizing voltages. Forskolin responses showed simple summation with responses to ionomycin
or hypotonic challenge. Thus, we found no evidence for interactions between CFTR and the channels responsible for swelling-mediated
responses. Differences were found in basal and ionomycin-stimulated efflux, but these may arise from variations in the clonally
selected cell lines that are unrelated to CFTR expression.
Received: 15 November 1995/Revised: 16 February 1996 相似文献
77.
Cathepsin B (EC 3.4.22.1) was purified from buffalo liver. The enzyme activity against-benzoyl-dl-arginine-naphthylamme (BANA) was substantially reduced by heat (above 37C) and by nondenaturing concentrations of urea (3 M) and guanidine hydrochloride (1 M). Cathepsin B was significantly activated by 1.5 mM EDTA alone. The activation of the enzyme was further enhanced in the presence of thiol compounds, e.g., cysteine thioglycolic acid, 2,3-dimercapto-1-propenol, and dithioerythritol (DTE). The minimum concentration of the thiol compound required for optimal activation of cathepsin B was found to be lowest (0.2 mM) for DTE. The BANA hydrolyzing activity of cathepsin B was substantially reduced by Cu2+ (20–200M) and Ca2+ (30–250 mM) as well as by thiol blocking reagents, e.g., iodoacetate, 5,5-dithiobis(2-nitro-benzoic acid) (DTNB), andp-hydroxymercuribenzoate (pHMB). The enzyme activity was completely abolished when the molar ratio of the reagent: cathepsin B was close to 1. The number of free sulfhydryl groups in cathepsin B was determined to be 2 by titration against DTNB and pHMB. Modification of one free thiol group of cathepsin B resulted in complete loss of BANA hydrolyzing activity. 相似文献
78.
Barley leaf protoplasts were incubated in light or darkness in the presence of various inhibitors, metabolites or weak acids/bases. Nitrate reductase (NR) and phosphoenolpyruvate carboxylase (PEPCase) were rapidly extracted from the protoplasts and assayed under sub-optimal conditions, i.e. in the presence of Mg2+ and malate, respectively. Under these conditions changes in activities are thought to reflect changes in the phosphorylation states of the enzymes. The NR was activated by illumination to 90% of its maximal activity within 10 min. Photosynthetic electron transport appeared necessary for light activation of NR since activation was inhibited by the photosynthetic electron-transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and, additionally, an electron acceptor (HCO
3
-
) was required. The PEPCase was also activated by light. However, this activation was not prevented by DCMU or lack of HCO
3
-
. Loading of protoplasts in the dark with a weak acid resulted in activation of both NR and PEPCase. For NR, full activation was completed within 5 min, whereas for PEPCase a slower, modest activation continued for at least 40 min. Incubation of protoplasts with a weak base also gave activation of PEPCase, but not of NR. On the contrary, base loading counteracted light activation of NR. Since several treatments tested resulted in the modulation of either NR or PEPCase activity, but not both, signal transduction cascades leading to changes in activities appear to be very different for the two enzymes.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron)
- DMO
5,5-dimethyl-2,4 oxazolidinedione
- NR
nitrate reductase
- PEPCase
Phosphoenolpyruvate carboxylase
This work was supported by the Norwegian Research Council by a Grant to C.L: L.H.S. was supported by the Biotechnology and Biological Sciences Research Council. 相似文献
79.
ZHU JINGDE 《Cell research》1995,(1)
INTanDUCTI0NMyeloidcelldifferentiati0n,inwhichmultip0tentialprogenitorcellsarec0nvertedint00neofthesixmaturedifferentiatedcells,i.e.,erythr0cytes,platelets(megakary-ocytes),macr0phages,neutr0phils,e0sinophilsandbas0phils,involvestemporalre-gulati0nofexpression0fanumberoflineage-anddifferentiationstage-specificgenes.Understandingthedevel0pmentalspecificationoflineageaJswellasmaturationstageassociatedpatterns0fgeneexpressioninmyel0idcelldifferentiationrequiresanin-sightintothecontrol0findivid… 相似文献
80.
INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti… 相似文献