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991.
The objective of this investigation was to evaluate the frequency of chromosomal aberrations expressed as micronuclei (MN)
in 4–8 cell embryos generated by gamma-irradiation of female mice in the absence and in the presence of vitamin C. Female
NMRI mice were whole body exposed to 4 Gy gamma-irradiation after intraperitoneal (i.p.) injection of pregnant mare’s serum
gonadotrophin (PMSG) followed by injection of human chorionic gonadotrophin (HCG) and mating with non-irradiated NMRI male
mice. Pregnant animals were sacrificed and embryos flushed from the oviducts and fixed on slides. Cells were treated for MN
observation using standard method. To investigate the protective effect of vitamin C (ascorbic acid) on the frequency of MN,
100 mg/kg vitamin C was i.p. injected 1 h before irradiation. Results show that the frequency of MN generated in the embryos
of irradiated mother compared to those of control in the non-irradiated group increased dramatically (P < 0.001). Frequency of MN in embryos generated in irradiated female mice treated with vitamin C dramatically and statistically
decreased relative to the frequency observed in the irradiation only group (P < 0.001). This decrease returned the combined treatment group to a level that was not statistically different from the controls
(P > 0.05). Thus, irradiation of preovulatory stage oocytes leads to stable chromosome abnormalities expressed as micronuclei
in successive preimplantation embryos. Vitamin C reduces these clastogenic effects of radiation in preovulatory oocytes and
thus the reduced frequency of MN in embryos is probably due to its antioxidation and radical scavenging properties. 相似文献
992.
Marcus Clauss Hanspeter Steinmetz Ulrike Eulenberger Pete Ossent Robert Zingg Jürgen Hummel Jean-Michel Hatt 《European Journal of Wildlife Research》2007,53(1):68-72
The digestive tract of elephants is surprisingly short compared to other herbivorous mammals. However, measurements relating
the length of the intestine to the body mass of the respective individual are rare. In this study, we report such data for
an African elephant and an Asian elephant. Our data support the hypothesis that Asian elephants have a longer intestinal tract
than their African counterparts. These findings are in accord with the observation of longer retention times and higher digestion
coefficients in Asian as compared to African elephants. This difference between the species could be the reflection of slightly
different ecological niches, with Asian elephants adapted to a natural diet with a higher proportion of grass. 相似文献
993.
In order to better understand the various pathways of sucrose and starch catabolism in the anther of lily (Lilium hybrida var. “Enchantment”), invertase (EC 3.2.1.26) and amylase (EC 3.2.1.1, EC 3.2.1.2) activities were measured separately in
different fractions (anther wall, locular fluid and microspore/pollen) and correlated with the sugar content during anther
development. Our findings showed significant differences among the fractions analyzed, suggesting that the regulation of sucrose
and starch catabolism could follow distinct pathways in each fraction. Glucose and fructose amounts progressively decreased
from anther wall to fluid and from fluid to microspore/pollen. Thus, the developing pollen could act as a sink for the carbohydrates
that reach the anther. In this sense, cell wall-bound invertases seem to play a major role in soluble sugar partitioning in
the different fractions of the anther. Sucrose concentration was found to be substantially higher in the locular fluid than
in the other fractions, indicating a probable site for storage. On the other hand, the anther wall tissues could have a buffering
function, storing nutrient surplus in starch grains and thus regulating the availability of soluble sugars in the whole anther.
All these results proved the advantages of the experimental model proposed here, as well as its usefulness to investigate
sugar metabolism in Lilium anthers. 相似文献
994.
We develop a comprehensive biogeochemical framework for understanding and quantitatively evaluating metals bio-protection
in sulfidic microbial systems. We implement the biogeochemical framework in CCBATCH by expanding its chemical equilibrium
and biological sub-models for surface complexation and the formation of soluble and solid products, respectively. We apply
the expanded CCBATCH to understand the relative importance of the various key ligands of sulfidic systems in Zn detoxification.
Our biogeochemical analysis emphasizes the relative importance of sulfide over other microbial products in Zn detoxification,
because the sulfide yield is an order of magnitude higher than that of other microbial products, while its reactivity toward
metals also is highest. In particular, metal-titration simulations using the expanded CCBATCH in a batch mode illustrate how
sulfide detoxifies Zn, controlling its speciation as long as total sulfide is greater than added Zn. Only in the absence of
sulfide does complexation of Zn to biogenic organic ligands play a role in detoxification. Our biogeochemical analysis conveys
fundamental insight on the potential of the key ligands of sulfidic systems to effect Zn detoxification. Sulfide stands out
for its reactivity and prevalence in sulfidic systems. 相似文献
995.
Michael J. W. Stokesbury Ronan Cosgrove Andre Boustany Daragh Browne Steven L. H. Teo Ronald K. O’Dor Barbara A. Block 《Hydrobiologia》2007,582(1):91-97
Pop-up satellite archival tags were attached to six Atlantic bluefin tuna (Thunnus thynnus) off the west coast of Ireland in autumn 2003 and 2004. The satellite tags measured pressure, ambient temperature and light
for the term of deployment. Radio pop-up satellite endpoint positions, light and sea surface temperature estimations of geolocation
indicate that two fish tagged minutes apart off the coast of County Donegal, migrated to the eastern and western Atlantic
Ocean over the following 8 months. The two fish were 5218 km apart at the termination of the experiment. After tagging in
September and popping up the following March and April, one fish had traveled to the western Atlantic while the other was
located in the waters off the southwest coast of Portugal. A third fish tagged off the coast of County Donegal in October
2004 moved into the Mediterranean Sea and was caught by a fishing vessel southeast of Malta on 11 June 2005. The results link
bluefin tuna feeding on European foraging grounds with known eastern breeding regions and western Atlantic waters. 相似文献
996.
A gene encoding β-glucosidase was cloned and over-expressed in Escherichia coli. Validamycin A was then biotransformed into validoxylamine A by using the resting recombinant cells. The biotransformation
yield reached 92% when the reaction was performed at 37°C for 1 h in the presence of 100 ml sodium phosphate buffer (0.1 M,
pH 7.0), 32 mM validamycin A and 0.71 mg dry cell w/ml. 相似文献
997.
Heather J. Robinson Gregor M. Cailliet David A. Ebert 《Environmental Biology of Fishes》2007,80(2-3):165-179
Feeding studies can provide researchers with important insights towards understanding potential fishery impacts on marine
systems. Raja rhina is one of the most common elasmobranch species landed in central and northern California demersal fisheries, yet life history
information is extremely limited for this species and aspects of its diet are unknown. Specimens of R. rhina were collected between September, 2002 and August, 2003 from fisheries-independent trawl surveys. Percent Index of Relative
Importance values indicated that the five most important prey items in 618 stomachs of R. rhina were unidentified teleosts (31.6% IRI), unidentified shrimps (19.6% IRI), unidentified euphausiids (10.9% IRI), Crangonidae
(7.4% IRI), and Neocrangon resima (6.0% IRI). There were significant dietary shifts with increasing skate total length and with increasing depths. Smaller
skates ate small crustaceans and larger skates ate larger fishes and cephalopods. With increasing depths, diet included bentho-pelagic
teleosts and more cephalopods and euphausiids. The findings of this study are consistent with previous researchers that report
similar diet shifts in skate species with size and depth. 相似文献
998.
Fang-fang Zhuan Zhen-feng Zhang Di-ping Xu Yan-hong Si Han-Zhong Wang Ghopur Mijit 《中国病毒学》2007,22(4):316-325
lacZa-mini-attTn7 was inserted into the intergenic region between the gG and gD genes in a PRV bacterial artificial chromosome (BAC) by homologous
recombination in E. coli. The resulting recombinant BAC (pBeckerZF1) was confirmed by PCR and sequencing. Green fluorescent protein (GFP) gene was
then transposed into pBeckerZF1 by transposon Tn7 to generate pBeckerZF2. Recombinant viruses vBeckerZF1 and vBeckerZF2 were
generated by transfection with the corresponding BAC pBeckerZF1 or pBeckerZF2. The titers and cytopathic effect (CPE) observed
for by vBeckerZF1 and vBeckerZF2 was comparable to that of the parental virus vBecker3. vBeckerZF2 was serial passaged for
five rounds in cell culture, and the mini-Tn7 insertion was stably maintained in viral genome. These results show that recombinant
viruses can be rapidly and reliably created by Tn7-mediated transposition. This technology should accelerate greatly the pace
at which recombinant PRV can be generated and, thus, facilitate the use of recombinant viruses for detailed mutagenic studies.
Foundation item: Key technologies R&D program (2006BAD06A01) from the Ministry of Science and Technology of China. 相似文献
999.
Both the Mississippi and Missouri rivers experienced major flooding in the spring and summer of 1993, inundating much of their
floodplains for long periods, and allowing fish access to vast but previously inaccessible benthic foraging areas. In response
to the latter, we hypothesized that flathead catfish (Pylodictis olivaris) would exhibit altered post-flooding growth as compared to like-aged fish whose lives were flood-free. To test this hypothesis,
we obtained the left pectoral fin spines from hoop-netted Mississippi River flathead catfish collected in the vicinity of
Crystal City, Missouri, USA, and conducted an individual-based back-calculated growth comparison of individuals captured pre-flood
(1991) and post-flood (1996). For like-aged cohorts, our back-calculated length-at-age data clearly show that the post-flooding
growth in 1996-collected fish was superior to that of the 1991-collected fish that had experienced less exceptional flow regimes.
This outcome suggests that increased forage or/and foraging opportunities can be a consequence of flooding, and that flathead
catfish are able to capitalize on this. The natural flooding regime of big rivers may thus be an important contributor to
the growth and success of certain fish species; consequently, modifying the river’s natural hydrograph and channel morphology
may be detrimental.
Handling editor: J. A. Cambray
An erratum to this article is available at . 相似文献
1000.
Gluconic acid (GA) is a multifunctional carbonic acid regarded as a bulk chemical in the food, feed, beverage, textile, pharmaceutical,
and construction industries. The favored production process is submerged fermentation by Aspergillus niger utilizing glucose as a major carbohydrate source, which accompanied product yield of 98%. However, use of GA and its derivatives
is currently restricted because of high prices: about US$ 1.20–8.50/kg. Advancements in biotechnology such as screening of
microorganisms, immobilization techniques, and modifications in fermentation process for continuous fermentation, including
genetic engineering programmes, could lead to cost-effective production of GA. Among alternative carbohydrate sources, sugarcane
molasses, grape must show highest GA yield of 95.8%, and banana must may assist reducing the overall cost of GA production.
These methodologies would open new markets and increase applications of GA.
Authors’ contributions OVS and RK are the sole contributors of this original review article. This review is based upon the published research in
the area of gluconic acid fermentation. 相似文献