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991.
Shari L. Laprise 《Molecular biotechnology》2010,45(2):187-197
The “holy grail” of regenerative medicine is the identification of an undifferentiated progenitor cell that is pluripotent,
patient specific, and ethically unambiguous. Such a progenitor cell must also be able to differentiate into functional, transplantable
tissue, while avoiding the risks of immune rejection. With reports detailing aberrant genomic imprinting associated with assisted
reproductive technologies (ART) and reproductive cloning, the idea that human embryonic stem cells (hESCs) derived from surplus
in vitro fertilized embryos or nuclear transfer ESCs (ntESCs) harvested from cloned embryos may harbor dangerous epigenetic
errors has gained attention. Various progenitor cell sources have been proposed for human therapy, from hESCs to ntESCs, and
from adult stem cells to induced pluripotent stem cells (iPS and piPS cells). This review highlights the advantages and disadvantages
of each of these technologies, with particular emphasis on epigenetic stability. 相似文献
992.
There is a special emphasis today on integrating traditional healing within health services. However, most areas in which
there is a system of traditional healing have undergone colonization and a number of pressures suppressing tradition for hundreds
of years. The question arises as to how one can understand today’s tradition in light of earlier traditions. This article
is based on material collected in Sámi areas of Finnmark and Nord-Troms Norway; it compares local healing traditions with
what is known of earlier shamanic traditions in the area. The study is based on 27 interviews among healers and their patients.
The findings suggest that although local healing traditions among the Sámi in northern Norway have undergone major transformations
during the last several hundred years, they may be considered an extension of a long-standing tradition with deep roots in
the region. Of special interest are also the new forms tradition may take in today’s changing global society. 相似文献
993.
K Königsson K Törneke IV Engeland K Odensvik H Kindahl 《Acta veterinaria Scandinavica》2003,44(4):153
The pharmacokinetics and the prostaglandin (PG) synthesis inhibiting effect of flunixin were determined in 6 Norwegian dairy
goats. The dose was 2.2 mg/kg body weight administered by intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) routes
using a cross-over design. Plasma flunixin content was analysed by use of liquid chromatography and the PG synthesis was evaluated
by measuring plasma 15-ketodihydro-PGF2α by a radioimmuno-assay. Results are presented as median (range). The elimination half-lives (t1/2·λ) were 3.6 (2.0–5.0), 3.4 (2.6–6.8) and 4.3 (3.4–6.1) h for i.v., i.m. and p.o. administration, respectively. Volume of distribution
at steady state (Vdss) was 0.35 (0.23–0.41) L/kg and clearance (CL), 110 (60–160) mL/h/kg. The plasma concentrations after oral administration
showed a double-peak phenomenon with the two peaks occurring at 0.37 (0.25–1) and 3.5 (2.5–5.0) h, respectively. Both peaks
were in the same order of magnitude. Bioavailability was 79 (53–112) and 58 (35%–120)% for i.m. and p.o. administration, respectively.
15-Ketodihydro-PGF2α plasma concentrations decreased after flunixin administration independent of the route of administration. 相似文献
994.
Subspecific relationships of the European beaverCastor fiber have been obscured by failure to follow the rules of the International Code of Zoological Nomenclature and remain an open
issue. Inconsequence in the use of subspecies names caused a nomenclatural as well as a taxonomic confusion. We discuss these
controversial and incorrect nomenclatural decisions, and recognize 9 nominal subspecies of European beaver, bearing 9 available
names:C. f. fiber Linnaeus, 1758,C. f. galliae Geoffroy, 1803, C. f. albicus Matschie, 1907,C. f. vistulanus Matschie, 1907,C. f. pohlei Serebrennikov, 1929,C. f. birulai Serebrennikov, 1929,C. f. tuvinicus Lavrov, 1969,C. f. belorussicus Lavrov, 1981, andC. f. orientoeuropaeus Lavrov, 1981. 相似文献
995.
996.
Soil carbon saturation: concept,evidence and evaluation 总被引:20,自引:0,他引:20
Catherine E. Stewart Keith Paustian Richard T. Conant Alain F. Plante Johan Six 《Biogeochemistry》2007,86(1):19-31
Current estimates of soil C storage potential are based on models or factors that assume linearity between C input levels
and C stocks at steady-state, implying that SOC stocks could increase without limit as C input levels increase. However, some
soils show little or no increase in steady-state SOC stock with increasing C input levels suggesting that SOC can become saturated with respect to C input. We used long-term field experiment data to assess alternative hypotheses of soil carbon storage
by three simple models: a linear model (no saturation), a one-pool whole-soil C saturation model, and a two-pool mixed model
with C saturation of a single C pool, but not the whole soil. The one-pool C saturation model best fit the combined data from
14 sites, four individual sites were best-fit with the linear model, and no sites were best fit by the mixed model. These
results indicate that existing agricultural field experiments generally have too small a range in C input levels to show saturation
behavior, and verify the accepted linear relationship between soil C and C input used to model SOM dynamics. However, all
sites combined and the site with the widest range in C input levels were best fit with the C-saturation model. Nevertheless,
the same site produced distinct effective stabilization capacity curves rather than an absolute C saturation level. We conclude
that the saturation of soil C does occur and therefore the greatest efficiency in soil C sequestration will be in soils further
from C saturation.
相似文献
Catherine E. StewartEmail: |
997.
Renata Jurišić Grubešić Sanda Vladimir-Knežević Dario Kremer Zdenka Kalodera Jadranka Vuković 《Biologia》2007,62(2):148-156
Micromorphological investigation of the types, dimensions and distribution of characteristic trichomes in leaves and stems
in Teucrium L. species (T. arduini L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb.) distributed in Croatia was carried out as part of the taxonomical study of the genus Teucrium. Secretory types of hairs, peltate and capitate hairs were observed on the epidermis of stems and leaves of all investigated
species. Non-secretory, acicular hairs were almost completely lacking on stems of T. scordium subsp. scordioides. Flagelliform hairs were not found in T. flavum and T. polium. Cladose hairs were present only in T. polium. The largest micromorphological variability was established between wild and cultivated samples of T. arduini and T. scordium subsp. scordioides, while cultivated and wild specimens of T. polium were almost identical. Differences were primarily observed in trichome dimensions and much less in micromorphological features. 相似文献
998.
Population dynamics of wireworms (Coleoptera,Elateridae) in arable land after abandonment 总被引:1,自引:0,他引:1
The community of elaterid larvae of three sites (field and two fallows), representing different stages of secondary succession,
were studied using soil sampling from 1986 to 1993. All three sites were abandoned arable land: a field cultivated until 1991,
a fallow I abandoned in 1986, and a fallow II abandoned about 1976. The fallow II was used as a meadow after abandonment and
was regularly mown until 1985, when cultivation stopped. Six species of Elateridae larvae were found at all three study sites.
In the field, Agriotes obscurus, Athous niger, Athous subsuscus, Dalopius marginatus and Athous vittatus were found, A. niger and A. obscurus being the most abundant species. During cultivation, larval densities were very low, however, larval abundance increased
up to 8.8 ± 8.3 ind. m-2 when cultivation stopped. Only small A. obscurus larvae were found during cultivation, whereas larval size increased after abandonment. In fallow I A. obscurus, A. niger, A. subsuscus, D. marginatus, and Agrypnus murinus were found and the average annual abundance fluctuated between 0.8 ± 1.4 to 40.8 ± 10.9 ind. m-2 with A. obscurus being the most abundant species. Fallow II supported the highest densities of wireworms from all plots studied (71.2±35.2
to 280.0±24.8 ind. m-2). A. obscurus, A. niger, A. subsuscus and D. marginatus were found in fallow II. The abundance of all larval Elateridae as well as the dominant species A. obscurus decreased during the study period, while simultaneously the occurrence of small sized A. obscurus larvae decreased. The frequency of cultivation and time elapsed since last cultivation appeared to be the most important
factors affecting elaterid occurrence in the field and fallow I. In fallow II, the decrease in abundance correlates with the
accumulation of a dense litter layer, which may correspond with soil surface structure, plant community changes or predator
pressure. 相似文献
999.
The influence of depth,site exposure and season on the intensity of iceberg scouring in nearshore Antarctic waters 总被引:2,自引:3,他引:2
Ice scour disturbance has a significant effect on the physical and biological characteristics of polar benthos. A series of
grids, each consisting of 25 markers, were deployed along depth transects and replicated at two contrasting study sites at
Adelaide Island, West Antarctic Peninsula. Markers were surveyed and replaced every 3 months for 2 years in order to assess
the frequency and intensity of iceberg impacts. Depth, site, season and year were all highly significant factors influencing
ice scouring frequency. We observed a high variation in the duration of winter fast ice between sites and years, which had
a marked effect on ice scouring frequency. The ecological effects of the disturbance regime are likely to include depth zonation
of benthic assemblages, patchiness of communities at varying stages of recovery and the near denudation of sessile fauna in
the shallow subtidal.
相似文献
Dan A. SmaleEmail: |
1000.