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991.
Irradiation of the kinetochore region of PtK2 chromosomes by laser light of 532 nm was used to study the function of the kinetochore region in chromosome movement and
to create artificial micronuclei in cells. When the sister kinetochores of a chromosome were irradiated at prometaphase, the
affected chromosome detached from the spindle and exhibited no further directed movements for the duration of mitosis. The
chromatids of the chromosome remained attached to one another until anaphase, at which point they separated. No poleward movement
of the chromatids was observed, and at telophase they passively moved to one of the daughter cells and were enclosed in a
micronucleus. The daughter cell containing the micronucleus was then isolated by micromanipulation and followed through subsequent
mitoses. At the next mitosis, two chromosomes, each with two chromatids, condensed in the micronucleus. These chromosomes
did not attach to the spindle and showed chromatid separation, but no poleward movements at anaphase. They were again enclosed
in micronuclei at telophase. The third generation mitosis was similar to the second.
Occasionally, both the irradiation-produced and naturally occurring micronuclei exhibited no chromosome condensation at mitosis.
Feulgenstained monolayers of PtK2 cells with naturally occurring micronuclei showed that some micronuclei stain positive for DNA and others do not. This finding
raises questions about the fate of chromosomes in a micronucleus. 相似文献
992.
Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity (
), in accord with the culture cell density. At low cell density
poise, whereas at confluency it increases to
poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in
cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates
similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin
receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the
erythropoiesis pathway. 相似文献
993.
The object of this study was to determine the kinetics of chromosome decondensation during the G1 period of the HeLa cell cycle. HeLa cells synchronized in the G1 period following the reversal of mitotic block were fused with Colcemid-arrested mitotic HeLa cells at 1.5, 3, 5, and 7 h
after the reversal of N2O block. The resulting prematurely condensed chromosomes (PCC) were classified into six categories depending on the degree
of their condensation. The frequency of occurrence of each category was plotted as a function of time after mitosis. The results
of this study indicate that the process of chromosome decondensation, initiated during the telophase of mitosis continues
throughout the G1 period without any interruption, thus the chromatin reaches an ultimate state of decondensation by the end of G1 period, when DNA synthesis is initiated. 相似文献
994.
S. A. Weiss T. L. Lester S. S. Kalter R. L. Heberling 《In vitro cellular & developmental biology. Plant》1980,16(7):616-628
Summary Chemically defined media SFRE-199-1 for the growth and SFRE-199-2 for the maintenance of primary baboon kidney (Bak) cell
cultures were formulated by supplementing medium M199 with insulin, sodium pyruvate, zinc sulfate, and increasing arginine-HCl,
cysteine, cystine,l-glutamine,l-glutamic acid, glycine, histidine, tyrosine, and glucose to maximally active nontoxic concentrations. For prolonged maintenance
of the cells, physiological pH control, and blocking of excessive lactic acid accumulation in the spent medium of the cell
cultures, it was necessary to supplement the medium containing Earle's balanced salts withd-(+) galactose.
The cells grew and were maintained equally well on glass or polystyrene surfaces. Selenium, when added to growth medium or
substituted for insulin and zinc sulfate, did not stimulate cell growth. Electron microscopy showed that numerous dense particles,
approximately 250 to 400 ? in diameter, with the appearance of glycogen, were found throughout the cytoplasm in the cells
grown in SFRE-199-1 and maintained in SFRE-199-2. Echovirus types 1 to 3, poliovirus types 1 to 3, coxsackievirus types B2,
B4, B5,Herpesvirus hominis type 1, simian herpesvirusH. simiae and SA8, and simian adenovirus SV34 when titrated in primary Bak cells and grown and maintained in SFRE-199-1 and 2, respectively,
developed titers comparable to those obtained in conventionally grown and maintained cells.
This study was supported in part by National Institute of Health Grant RR00361 and World Health Organization Grant V4/181/38.
This laboratory serves as the NIH/WHO Collaborating Center for Reference and Research in Simian Viruses. 相似文献
995.
Selective isolation and culture of a proliferating epithelial cell population from the hamster trachea 总被引:7,自引:0,他引:7
William E. Goldman Joel B. Baseman 《In vitro cellular & developmental biology. Plant》1980,16(4):313-319
Summary A reliable cell isolation technique was developed to allow the cultivation of cells from the hamster respiratory tract. Repeated
thermolysin treatments and gradient centrifugation yielded a cell culture completely free from contamination by fibroblasts.
Viable cells could be isolated from as little tissue as a single hamster trachea, but in vitro proliferation occurred only
if the hamster was less than 4 months of age. The cultured cells could be repeatedly passaged and subcultured for weeks by
employing normal tissue culture techniques. Morphologically, the monolayers appeared to be a homogeneous population of epithelial
cells, and successful cloning of freshly isolated single cells resulted in apparently identical cultures. The epithelial origin
of these cells was also suggested by continued growth in minimum essential medium withd-valine substituted forl-valine. The relative ease with which this cell type can be isolated, cultured, and manipulated in vitro should encourage
its application as a model of the respiratory epithelium.
This research was supported by Public Health Service Grant P50-HL 19171 and Research Career Development Award 1-K04-AI 00178
to J. B. B. 相似文献
996.
997.
Jason Yang Raphael Guzman James Richards S. Nandi 《In vitro cellular & developmental biology. Plant》1980,16(6):502-506
Summary Mammary tumor epithelial cells from BALB/cfC3H mice were dispersely embedded inside the collagen gels in Ham's F-12 medium
containing horse serum. A sustained cell growth leading to a 5- to 10-fold increase in cell number over initial level was
observed in less than 2 weeks. The extent of this growth was found to be dependent on serum concentration. However, addition
of various protein and steroid hormones, both singly and in combination, to low-serum-containing medium failed to achieve
a comparable level of growth to that promoted by higher serum concentration. Mammary tumor cells can now be consistently propagated
in primary culture.
This investigation was supported by Grants CA05388 and CA09041 awarded by the National Cancer Institute, Department of Health,
Education and Welfare, and by cancer research funds of the University of California. 相似文献
998.
Asynchronous 9L cells were separated into relatively homogeneously-sized populations using centrifugal elutriation with both
a conventional collection method and a long collection method. A substantial increase in the homogeneity of the volume distributions
and in the degree of synchrony of the separated fractions was obtained using the long collection method. Autoradiographic
data indicated that fractions containing ≥97% G1 cells, ≥80% S cells, and 70–75% G2 cells could be routinely recovered with this procedure. Recovery in these fractions varied from 5 to 8% of the total number
of cells elutriated. The colony forming efficiency (CFE) of cells from fractions representing each phase of the cell cycle
was a constant 60–70%, which was comparable to the 60–80% usually found for asynchronous 9L cells. The percentage of cells
in the G1, S, and G2 phases in the elutriated fractions was more accurately determined from the volume distribution than from computer fits of
the DNA histogram obtained from flow cytometry. In general, the degree of synchrony was related to the coefficient of variation
(CV) of the volume distributions of the elutriated fractions. The CV was about 14% for all elutriated fractions. When the
≥97% G1 population was allowed to progress to S and G2, the CVs were about 17 and 20.2%, respectively. Thus, the best nonperturbing method for obtaining synchronous 9L cells in
the S or G2 phases was direct elutriation with the long collection method. 相似文献
999.
Cytochrome P-448 from Saccharomyces cerevisiae in permeabilized whole cell, microsomal fraction and in a highly purified reconstituted benzopyrene-3-monooxygenase (EC 1.14.14.1) system have been immobilized on various supports. Calcium alginate was found to be especially useful and the kinetics of hydroxylation were close to that of the free enzyme system with all three forms of enzyme, even with permeabilized whole yeast cells (V max of 664 pmol 3-hydroxybenzo(a)pyrene produced per h per nmol cytochrome P-448 compared with 1000 for free highly purified reconstituted enzyme system). Only the highly purified reconstituted form was successfully immobilized by BrCN-activated Sepharose-4B or by acrylamide. Both of these supports stabilized the highly purified reconstituted cytochrome P-448 benzopyrene-3-monooxygenase activity in prolonged storage at 4°C. Applications for various immobilized enzymes and cells are assessed. 相似文献
1000.
Bo Mattiasson Per-Olof Larsson Lennarth Lindahl Peter Sahlin 《Enzyme and microbial technology》1982,4(3):153-157
A vitamin B1 (thiamin)-sensitive electrode has been devised by combining an oxygen electrode with a yeast-containing membrane. The assembly was used for assaying thiamin at concentrations down to 10?11 gl?1. The analytical procedure developed should allow the measurement of 10–20 samples per hour. The performance of the yeast electrode was improved when alginate membranes reinforced with a nylon network were used. An apparatus for preparing such membranes is described together with a magnetic membrane holder facilitating handling of membranes in combination with electrodes. 相似文献