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951.
Fish gene mapping studies have identified several syntenic groups showing conservation over more than 400 million years of vertebrate evolution. In particular, Xiphophorus linkage group IV has been identified as a homolog of human chromosomes 15 and 19. During mammalian evolution, loci coding for glucosephosphate isomerase, peptidase D, muscle creatine kinase, and several DNA repair genes (ERCC1, ERCC2, and XRCC1) appear as a conserved syntenic group on human chromosome 19. When X. clemenciae and X. milleri PstI endonuclease-digested genomic DNA was used in Southern analysis with a human ERCC2 DNA repair gene probe, a strongly cross-hybridizing restriction fragment length polymorphism was observed. Backcrosses to X. clemenciae from X. milleri x X. clemenciae F1 hybrids allowed tests for linkage of the ERCC2-like polymorphism to markers covering a large proportion of the genome. Statistically significant evidence for linkage was found only for ERCC2L1 and CKM (muscle creatine kinase), with a total of 41 parents and 2 recombinants (4.7% recombination, chi 2 = 35.37, P less than 0.001); no evidence for linkage to GPI and PEPD in linkage group IV was detected. The human chromosome 19 synteny of ERCC2 and CKM thus appears to be conserved in Xiphophorus, while other genes located nearby on human chromosome 19 are in a separate linkage group in this fish. If Xiphophorus gene arrangements prove to be primitive, human chromosome 19 may have arisen from chromosome fusion or translocation events at some point since divergence of mammals and fishes from a common ancestor. 相似文献
952.
953.
This comparative study explores how low temperatures affect the mortality and growth of first generation hatchery-reared progeny
of subarctic populations of Arctic charr (Salvelinus alpinus L.) and European whitefish (Coregonus lavaretus L.). Replicate fish groups where held under simulated natural light regimes (70°N) at three constant temperatures (1, 3 and
6°C). The mortality of Arctic charr was low (≤1.4%) at all temperature treatments, whereas the mortality of whitefish increased
with decreasing temperature from 6% at 6°C to 33% at 1°C. The Arctic charr exhibited higher growth rates than whitefish at
all three temperature regimes. All groups of Arctic charr increased in weight, whereas whitefish held at 1°C did not gain
weight throughout the experimental period of 133 days. Arctic charr exhibited a large intraspecific variability in growth
leading to large variations in size-structure, whereas whitefish in contrast showed very homogenous growth and size-structure
patterns; a dissimilarity probably related to species-specific differences in antagonistic behaviour. Evidently, Arctic charr
are more cold water adapted than whitefish and are able to maintain growth at extremely low temperatures. Arctic charr thus
appear to be the most suitable species for aquaculture at low water temperatures. 相似文献
954.
Per Björntorp 《Experimental cell research》1983,149(1):277-287
Factors involved in the growth of adipose tissue were examined by testing interactions under cell culture conditions between cellular components of this tissue and plasma from overfed rats. The cellular factors were capillary fragments, endothelial cells during growth and after confluence, fibroblasts, adipocytes and adipose precursor cells before determination (adipoblasts) and after determination (preadipocytes). Multiplying adipose precursor cells stimulated markedly the multiplication of endothelial cells, while their own multiplication was inhibited. The stimulatory effect was partially transferred into the culture medium but not remaining in culture dishes conditioned by preceding cultures of adipose precursor cells, removed by Tris-EDTA buffer or mechanically. The activity was apparently not dependent on feeding conditions. Plasma from overfed rats did not affect endothelial or adipose precursor cell multiplication, but caused more rapid lipid filling of the latter. Endothelial cells facilitated lipid accumulation of preadipocytes. These results indicate that when adipose tissue is expanding by adipocyte multiplication capillarization is stimulated secondarily, being then capable of facilitating triglyceride accumulation in adipocytes. 相似文献
955.
Frede Østergaard Andersen Per Famme 《Journal of experimental marine biology and ecology》1983,66(1):89-92
A precise and rapid method is described for the determination of fresh weight of aquatic plants and animals. The determination of fresh weight is done gravimetrically with a spectrophotometric estimate of adherent water providing a correction for adherent water. 相似文献
956.
957.
Assessment of Production Conditions for Efficient Use of Escherichia coli in High-Yield Heterologous Recombinant Selenoprotein Synthesis 总被引:1,自引:0,他引:1 下载免费PDF全文
958.
959.
J Llopis A Lampreabe M López Frías F Perán N Blanco Martínez G Urbano M A Montellano 《Hormones et métabolisme》1990,22(2):71-74
The influence of i.m. administration to the mother of hydrocortisone acetate (doses of 0.4, 0.8 or 2.0 mg/100 g body weight/day) during the first 15 days of lactation on milk protein and lactose composition and serum levels of protein, glucose and insulin in dams and pups is studied. Total serum proteins and albumin/globulin ratio in dams were unchanged by treatment. The daily injection of 0.4 or 0.8 mg/100 g body weight failed to alter serum levels of glucose or insulin in dams, whereas a dose of 2.0 mg/100 g body weight led to a rise in glucemia (from 118 +/- 3.2 to 133 +/- 5.3) which was accompanied by a sharp change in insulinemia (from 40.7 +/- 4.1 to 83.6 +/- 6.9). All three doses raised protein levels in milk. The smallest increase was recorded with 2.0 mg/100 g body weight; this dose also reduced milk lactose content. Total serum proteins in pups rose slightly but nonsignificantly, and no significant effects were noted on albumin/globulin ratio or serum glucose and insulin levels. 相似文献
960.
A mixture of tritiated and deuterated gibberellin A9 (GA9 ) was injected into elongating shoots of Norway spruce [ Picea abies (L.) Karst.] grafts grown under environmental conditions that were either inductive (heat and drought, HD) or noninductive (cool and wet, CW) for flowering. The shoots were divided into needles and shoot stems. The metabolites were purified by high performance liquid chromatography (HPLC), detected by liquid scintillation counting of aliquots of collected fractions and identified by gas chromatography-mass spectrometry (GC-MS). Deuterated GA9 was converted to deuterated GA4 in both treatments. The major metabolite in the CW-treated material was GA51 . The HD-treated material did not convert GA9 to GA51 , but a cellulase-hydrolysable GA9 -conjugate was formed. The same metabolites were found in the shoot stems, though in smaller amounts. The amounts of detected metabolites were higher in the HD material, caused by a higher rate of metabolism and/or smaller losses of the metabolites during sample purification. The estimated amounts of endogenous GAs show that the HD-treated material contained higher amounts of GA9 but no differences in the amounts of GA4 were found. 相似文献