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991.
992.
This study was conducted to examine the hypothesis that nitric oxide (NO) affects prehatching development of bovine oocytes fertilized in vitro. In experiment 1, inseminated oocytes were cultured in a cumulus–granulosa cell (CG) coculture system to which 0.008 or 0.04 mM of sodium nitroprusside (SNP), a spontaneous NO releaser, was added at 18 or 60 hr postinsemination. Embryo development was greatly (P < 0.001) inhibited by the addition of SNP, regardless of time of addition or SNP concentration. In experiment 2, eight-cell embryos were cultured singly in a defined medium, to which 0.0016, 0.008, or 0.04 mM of SNP was added. Development to the blastocyst stage was greatly (P < 0.001) decreased after addition of SNP compared with no addition. Higher (P < 0.02) concentration of NO metabolites was found in developmentally arrested embryos than in developing embryos at 144 hr postinsemination (experiment 3). In experiment 4, blastocyst formation of oocytes cocultured with CGs was significantly (P < 0.02) increased after addition of hemoglobin (Hb, 1 μg/ml), an NO scavenger. Prehatching development of oocytes was significantly (P < 0.05) increased after addition of Hb at different time intervals (18, 60, or 144 hr postinsemination) in experiment 5. Embryo development was not enhanced by Hb addition to the culture medium in the absence of CGs (experiment 6). Prehatching development of eight-cell embryos derived from a Hb-containing culture system was not promoted by the further addition of Hb after transfer of the embryos to a defined and CG-free single-embryo culture system (experiment 7). In conclusion, NO, which may be secreted from CGs, has an inhibitory role in prehatching development of bovine oocytes fertilized in vitro, and use of an NO scavenger, Hb, in a coculture system enhances blastocyst formation. Mol. Reprod. Dev. 50:45–53, 1998. © 1998 Wiley-Liss, Inc. 相似文献
993.
《Cryobiology》2020
PurposeEmbryo cryopreservation represents a central procedure in in-vitro fertilization (IVF) programs. This report documents a Case of a successful pregnancy following the replacement of embryos that had to be re-vitrified due to the forced cancellation of the frozen embryo-transfer (FET).Principle resultsThe 37- year-old patient was referred to our Assisted Reproductive Technology (ART) unit for idiopathic infertility and recurrent implantation failures. The collection cycle resulted in 8 grade-A cleavage embryos (8–10 blastomeres), that were all vitrified to prevent ovarian hyperstimulation syndrome (OHSS). The first frozen embryo transfer (FET) ended in a biochemical pregnancy and the second in an ectopic pregnancy. In the third attempt, three embryos were warmed but the provider could not complete the transfer due to cervical stenosis. The two surviving embryos were therefore re-vitrified. The final FET attempt, 4 months later, was successful and ended with the live birth of a healthy female baby.ConclusionsThe transfer of re-vitrified twice-warmed embryos may represent a possible option when embryo transfer cannot be performed. 相似文献
994.
Rapid and repeatable shifts in life‐history timing of Rhagoletis pomonella (Diptera: Tephritidae) following colonization of novel host plants in the Pacific Northwestern United States 下载免费PDF全文
Monte Mattsson Glen R. Hood Jeffrey L. Feder Luis A. Ruedas 《Ecology and evolution》2015,5(24):5823-5837
Host shifts of phytophagous insect specialists to novel plants can result in divergent ecological adaptation, generating reproductive isolation and potentially new species. Rhagoletis pomonella fruit flies in eastern North America underwent a host shift ~160 ya from native downy hawthorn (Crataegus mollis) to introduced, domesticated apple (Malus domestica). Divergent selection on diapause phenology related to the earlier fruiting time of apples versus downy hawthorns resulted in partial allochronic reproductive isolation between the fly races. Here, we test for how rapid and repeatable shifts in life‐history timing are driving ecological divergence of R. pomonella in the Pacific Northwestern USA. The fly was introduced into the region via larval‐infested apples 40–65 ya and now attacks native black hawthorn (Crataegus douglasii) and introduced ornamental hawthorn (Crataegus monogyna), in addition to early‐ and late‐maturing apple varieties in the region. To investigate the life‐history timing hypothesis, we used a field‐based experiment to characterize the host‐associated eclosion and flight activity patterns of adults, and the feeding times of larvae at a field site in Vancouver, Washington. We also assessed the degree to which differences in host‐fruiting time generate allochronic isolation among apple‐, black hawthorn‐, and ornamental hawthorn‐associated fly populations. We conclude that host‐associated fly populations are temporally offset 24.4% to 92.6% in their seasonal distributions. Our results imply that R. pomonella possesses the capacity for rapid and repeatable shifts in diapause life history to match host‐fruiting phenology, which can generate ecologically based reproductive isolation, and potentially biodiversity in the process. 相似文献
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T.M. Osaili R.R. Shaker M.M. Ayyash A.A. Al-Nabulsi S.J. Forsythe 《Letters in applied microbiology》2009,48(4):408-412
Aims: To determine the survival and growth characteristics of Cronobacter species ( Enterobacter sakazakii ) in infant wheat-based formulas reconstituted with water, milk, grape juice or apple juice during storage.
Methods and Results: Infant wheat-based formulas were reconstituted with water, ultra high temperature milk, pasteurized grape or apple juices. The reconstituted formulas were inoculated with Cronobacter sakazakii and Cronobacter muytjensii and stored at 4, 25 or 37°C for up to 24 h. At 25 and 37°C, Cronobacter grew more (>5 log10 ) in formulas reconstituted with water or milk than those prepared with grape or apple juices ( c. 2–3 log10 ). The organism persisted, but did not grow in any formulas stored at 4°C. Formulas reconstituted with water and milk decreased from pH 6·0 to 4·8–5·0 after 24 h, whereas the pH of the formulas reconstituted with fruit juices remained at their initial pH values, c. pH 4·8–5·0.
Conclusions: Cronobacter sakazakii and C. muytjensii can grow in reconstituted wheat-based formulas. If not immediately consumed, these formulas should be stored at refrigeration temperatures to reduce the risk of infant infection.
Significance and Impact of the Study: The results of this study will be of use to regulatory agencies and infant formula producers to recommend storage conditions that reduce the growth of Cronobacter in infant wheat-based formulas. 相似文献
Methods and Results: Infant wheat-based formulas were reconstituted with water, ultra high temperature milk, pasteurized grape or apple juices. The reconstituted formulas were inoculated with Cronobacter sakazakii and Cronobacter muytjensii and stored at 4, 25 or 37°C for up to 24 h. At 25 and 37°C, Cronobacter grew more (>5 log
Conclusions: Cronobacter sakazakii and C. muytjensii can grow in reconstituted wheat-based formulas. If not immediately consumed, these formulas should be stored at refrigeration temperatures to reduce the risk of infant infection.
Significance and Impact of the Study: The results of this study will be of use to regulatory agencies and infant formula producers to recommend storage conditions that reduce the growth of Cronobacter in infant wheat-based formulas. 相似文献
998.
999.
1000.
The development of ovules and embryo sacs in Ostrya virginiana was studied for
the first time. Most ovaries had two ovules which were anatropous, unitegmic and crassinucellate. The ovule usually possessed several archesporial ceils which divided periclinally into the upper parietal cell and the lower sporogenous cell. The sporogenous cell functioned directly as megaspore mother cell. The tetrad of megaspores was linear in arrangement, and
every megaspore might be functional. One ovule often contained 2- 6 embryo sacs and the
embryo sac belongs to Polygonum type. It can be concluded from the present data that all
ovules among the genera of the Betulaceae are unitegrnic. There are more groups with the
phenomenon of multiple embryo sacs in anemophic plants such as Betulaceae, Casuarinaceae,
Graminae, Jnglandaceae, Myricaceae, Simaroubaceae, Ulmaceae, than in entomophilous
plants. Multiple embryo sacs also occur among some parasitic plants and saprophytes, e.g.
Orobanchaceae, Cassytha in Lauraceae, Cuscuta in Convolvulaceae and Utricularia in Lentibulariaceae. It may be inferred that the characteristic of multiple embryo sacs be an evolutionary adaptation of those plants with lower pollination rate to increase the rate of fertilization. Finally, a comparison of embryological characters among the genera of the Betulaceae
shows that the family is of a number of common embryological characters, such as multicellular archesporium, multiple embryo sacs in one ovule, and a long interval between pollination
and fertilization. The diversity and systematic significance of several embryological characters
among the “higher” hamamelid families are also discussed. It is still hard to explain the phy-logenetic relationships among those families clearly only with. 相似文献