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881.
G. Bradd Witt Lindi J. Berghammer Robert J. S. Beeton Eugene J. Moll 《Austral ecology》2000,25(3):260-267
This paper explores the potential of a new method of reconstructing historical vegetation change in the Australian rangelands. Historical monitoring of rangeland vegetation has been so deficient that it is not possible to determine whether a long‐term trend toward degradation has occurred (as is often assumed) or, indeed, if it is continuing to occur. Because long‐term records are unavailable any attempt to monitor vegetation retrospectively must be based on proxy measures rather than direct observation. Where historical data are lacking an integration of palaeoecological, archaeological and ecological methods is required to reconstruct the past. Our research is based on a detailed analysis of sheep faeces deposited near a shearing shed in the semiarid rangelands of south‐west Queensland between the late 1930s and the mid‐1990s. The faeces in these deposits represent the diet of sheep in the days leading up to the property’s annual shearing and as such are a potentially useful index to changes in vegetation. Results indicate significant changes in the diet of sheep since the late 1940s. The potential of this method, and its limitations, are discussed. Long‐term records are critical in understanding issues of sustainability in land management and it is intended that this paper will stimulate further research into historical vegetation change in rangelands. 相似文献
882.
E. Schulze Martin Witt M. Kasper Clemens W. G. M. Löwik Richard H. W. Funk 《Histochemistry and cell biology》1999,111(1):61-69
Until now, many extracellular matrix proteins, e.g. osteopontin and osteonectin, have been used to determine a cell’s osteogenic
maturation. The disadvantage in evaluation of these proteins is their relative wide-ranging appearance throughout the osteogenic
differentiation process. Thus, the aim of this study was to establish an immunohistochemical setup using E11, a marker that
binds selectively to cells of the late osteogenic cell lineage. In addition, the histochemical expression of the bone matrix
proteins osteonectin, osteopontin and fibronectin was compared to that of E11 using monoclonal antibodies. For light microscopical
detection of osteogenic markers in cultured cells we developed a simple paraffin technique using a fibrin glue as embedding
medium. This allows the handling of cultured cells such as a tissue sample and includes the use of stored biological specimens
for further immunohistochemical experiments. We used newborn rat calvariae for whole tissue preparations and for isolation
and cultivation of bone cells. In addition, we included the rat osteosarcoma cell line ROS 17/2.8 in this study. For the first
time, we have localised E11 in osteocytes of rat calvaria preparations at the electron microscopical level. E11 was detected
at plasma membranes of osteocytes and their processes, but not at those of osteoblasts. Accompanying experiments with cultured
newborn rat calvaria cells and ROS 17/2.8 cells revealed E11 reactivity on a subset of cells. The results obtained confirm
the suitability of the differentiation marker E11 as a sensitive instrument for the characterisation of bone cell culture
systems.
Accepted: 25 August 1998 相似文献
883.
B. J. Trask Heather Mefford Ger van den Engh Hillary F. Massa Ramesh C. Juyal Lorraine Potocki Brenda Finucane Dianne N. Abuelo David R. Witt Ellen Magenis Antonio Baldini Frank Greenberg James R. Lupski P. I. Patel 《Human genetics》1996,98(6):710-718
We have used bivariate flow karyotyping to quantify the deletions involving chromosome 17 in sixteen patients with Smith-Magenis
syndrome (SMS). The fluorescence intensities of mitotic chromosomes stained with Hoechst 33258 and chromomycin were quantified
in a dual-beam flow cytometer. For each patient, the position of the peak representing the deleted chromosome 17 was compared
to those of the normal homologs of an unaffected parent. The patients could be classified into four groups based on the size
of their deletions. The deletions ranged from ∼9–10 Mb (∼10–11% of the chromosome) to below the detection limit of the technique
(2 Mb). Different deletion sizes were detected among patients whose high-resolution banding results were similar. Some deletions
detected by banding were not detected by flow analyses. Deletion estimates are largely consistent with the results of molecular
analyses. Patients with larger deletions that extend into band 17p12 have abnormal electrophysiologic studies of peripheral
nerves. Deletion size does not appear to correlate with the degree of mental retardation, presence of behavioral abnormalities,
craniofacial anomalies or common skeletal findings in SMS. By identifying patients with varying deletion sizes, these data
will aid the construction of a long-range deletion-based map of 17p11.2 and identification of the genes involved in this syndrome.
Received: 19 March 1996 / Revised: 21 June 1996 相似文献
884.
H. Taina Darius Catherine Dauga Patrick A. D. Grimont Eliane Chungue Paul M. V. Martin 《The Journal of eukaryotic microbiology》1998,45(6):619-627
ABSTRACT The diversity of symbiotic dinoflagellates (SD) from seven coral species ( Fungia scutaria, Fungia paumotensis, Lep-tastrea transversa, Pavona cactus, Pocillopora verrucosa, Montastrea curia , and Acropora fonnosa ) was studied in a restricted geographical area, the Lagoon of Arue on the island of Tahiti. Their diversity was explored by small subunit ribosomal RNA gene (SSU rDNA) restriction fragment length polymorphism (RFLP). After a nested amplification with SD specific primers, RFLP analyses were performed directly and after a cloning step. The diversity of these different SSU rDNA was estimated in respect to possible technical artifacts. In an axenic culture of SD from the coral Galaxea fascicularis , both heterogeneous SSU rDNAs and artifact molecules were observed as in our SD samples. According to the number of patterns observed, corals Fungia paumotensis, Leptastrea transversa. Pavona cactus, Montastrea curia, and Acropora fonnosa contained one class of SD SSU rDNAs. whereas Fungia scutaria and Pocillopora verrucosa contained three and two classes of SD SSU rDNAs respectively. In the limited geographic area studied. SD from different coral species shared the same pattern, except SD from Montastrea curta , which showed a unique pattern. In addition to the possibility of SD flux among different coral species, specific mechanisms could also be involved in the establishment of a symbiosis. 相似文献
885.