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31.
Spontaneous Activation of Quiescent Uq Transposable Elements during Endosperm Development in Zea Mays 总被引:1,自引:1,他引:0
This study addresses the question of the activation of quiescent transposable elements in maize breeding lines. The a-ruq reporter allele of the Uq transposable element system expresses Uq activity (spots or sectors of spots in otherwise colorless aleurone tissue) when exposed to various genotypes of assorted maize inbred lines lacking any active Uq element. This activation of quiescent Uq elements occurs randomly during the growth of the endosperm. It is concluded that there are components in the genome that enhance the rare activation of quiescent Uq elements. Further, it seems that this activation occurs in the absence of any stress-inducing treatment, but that normal growth conditions provide sufficient stimulus for such activation. 相似文献
32.
Interactive roles of progesterone, prostaglandins, and collagenase in the ovulatory mechanism of the ewe 总被引:2,自引:0,他引:2
W J Murdoch T A Peterson E A Van Kirk D L Vincent E K Inskeep 《Biology of reproduction》1986,35(5):1187-1194
Interrelationships between production of progesterone (P4), prostaglandin (PG) E2 and PGF2 alpha, and collagenase by periovulatory ovine follicles and their possible involvements in the ovulatory process were investigated. Follicles were isolated from ovaries at intervals (0 to 24 h) after the initiation of the preovulatory surge of luteinizing hormone (LH). Progesterone and PGs within follicles were determined by radioimmunoassay. Digestion of radioactive collagen during coincubation with tissue homogenates was used to assess the production of a bioactive follicular collagenase(s). Follicular accumulation of PGs and P4 increased at 12 and 16 h, respectively, after the onset of the surge of LH; PGE2 then decreased at 20 h. Collagenolytic activity of follicular tissue increased at 20 h and was maximal at 24 h (during the time of follicular rupture). An inhibitor of synthesis of P4 (isoxazol) or PGs (indomethacin) was injected into the follicular antrum at 8 h. Isoxazol did not prevent the initial rise in PGs, but inhibited synthesis of PGF2 alpha at 16 h and therafter. Isoxazol negated the decline in PGE2 and increase in collagenolysis. Indomethacin did not influence synthesis of P4; however, it suppressed collagenolytic activity of follicular tissue. Ovaries with treated follicles were left in situ and observed for an ovulation point at 30 h. Isoxazol or indomethacin was a potent inhibitor of ovulation. The blockade of ovulation by isoxazol was reversed by systemic administration of P4 or PGF2 alpha, but not by PGE2. Reversal of the blockade by indomethacin was accomplished with PGE2 or PGF2 alpha. Collagenolytic activity of follicular tissue was likewise restored by such treatments.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
33.
Structure and regulation of the sheep metallothionein-Ia gene 总被引:6,自引:0,他引:6
Screening of a sheep genomic lambda library with a sheep metallothionein-I cDNA clone resulted in the isolation of a 13,200-base-pair fragment containing a metallothionein gene which DNA sequence analysis identified as the gene encoding the cloned cDNA. The two introns occur at identical positions to those in other mammalian metallothioneins but are considerably larger. The first intron contains a DNA element that is present in a related but not identical form in many places in the sheep genome. Comparison of the promoter sequences of this gene (sMT-Ia) with the promoters of metallothionein genes from other species identified a number of conserved regions which may be important in the regulation of this gene by heavy metals, glucocorticoids and alpha-interferon. In sheep fibroblasts, the levels of sMT-Ia mRNA was found to be maximally elevated (95-fold) in the presence of zinc or cadmium and elevated 30-fold in the presence of copper. Dexamethasone had no effect upon mRNA levels. Thus this gene shows a pattern of regulation similar to the human MT-If gene, but distinct from the other human and mouse metallothionein genes so far reported. 相似文献
34.
Inherited X-chromosome inverted tandem duplication in a male traced to a grandparental mitotic error. 总被引:1,自引:0,他引:1 下载免费PDF全文
S Schwartz M F Schwartz S R Panny C J Peterson E Waters M M Cohen 《American journal of human genetics》1986,38(5):741-750
A male infant was referred for cytogenetic evaluation because of dysmorphic features and developmental delay. In both lymphocytes and skin fibroblasts, a modal number of 46 chromosomes was obtained with an obvious elongation of the long arm of the X chromosome (Xq+). Studies of seven members in 3 generations of this family showed that the proband's mother, sister, and maternal grandmother were phenotypically normal carriers of this abnormal X chromosome. High resolution GTG- and RBG-banding defined the extra chromatin material as an inverted duplication of Xq21----Xq24. This was supported by an approximate twofold increase in alpha-galactosidase A activity, localized to Xq21----q24, observed in the proband's lymphocytes and fibroblasts. BrdU-incorporation studies of the mother's lymphocytes showed the abnormal X to be late replicating in all 100 cells studied and normal alpha-galactosidase A levels. Cytogenetic analysis of the maternal grandmother revealed cytogenetic mosaicism with one cell line containing the abnormal X (37%), and the other, a normal female karyotype (63%). This family is instructive since: (1) it represents only the second case of a dysmorphic male demonstrating a confirmed interstitial partial Xq duplication, and (2) the origin of this familial structural rearrangement has been traced to a grandparental mitotic error. 相似文献
35.
Mineral licks as a sodium source for Isle Royale moose 总被引:1,自引:0,他引:1
Summary Natural mineral licks and their use by moose (Alces alces) on Isle Royale National Park, Michigan, were studied during 1982–85. The distribution of known licks suggested that they occurred in association with glacial debris, primarily in the western portions of the island. Moose utilized mineral springs extensively during the spring-summer period, and at least 5 licks were used year-round. During summer, a pronounced diel pattern of moose visitation was apparent, with peak use occurring between 0400–0800 h. Although daytime lick use declined by late June, morning and evening use continued to be relatively high throughout the study period. Peak lick use coincided with leaf-emergence in spring. Moose continued to utilize mineral licks despite the availability of ponds containing aquatic plants. Sodium appeared to be the element attracting moose to licks where they ingest copious amounts of water. Observed sodium ingestion rates (0.35 g/min) at licks indicate that licks provide a more concentrated source of sodium compared to aquatic plants (0.023 g/min). Based on the data presented, we reject the conclusions of earlier workers that aquatic plants constitute the only significant source of sodium for Isle Royale moose. 相似文献
36.
Udo Wienand Ulrike Weydemann Ursula Niesbach-Klösgen Peter A. Peterson Heinz Saedler 《Molecular & general genetics : MGG》1986,203(2):202-207
Summary The c2 locus of Zea mays, identified as one of the genes affecting anthocyanin biosynthesis, was cloned using the transposable element En (Spm) as a gene tag. The Spm element present at the c2 locus in the autonomously mutating c2-m1 line was isolated using En1 element specific probes. Sequences flanking the element were identified as c2 locus specific and were used to clone the nonautonomous c2-m2 and wild-type alleles. The cloning and analysis of a cDNA complementary to the c2 locus provided evidence that this gene encodes the enzyme chalcone synthase. 相似文献
37.
Specific cell surface insulin binding to embryonic chick neural retina cells has been demonstrated in vivo. Kinetics of insulin binding as well as hormonal specificity were similar to those reported for other vertebrate cells and tissues, both neural and nonneural. When surface insulin binding to retinal cells was studied as a function of embryonic age, a developmental relationship was observed. Scatchard analysis revealed that the number of cell surface insulin receptors decreased approximately 75% between days 10 and 16 of embryonic development. Receptor affinities remained fairly constant for this period. 相似文献
38.
Abrogation of cell surface expression of human class I transplantation antigens by an adenovirus protein in Xenopus laevis oocytes 总被引:3,自引:1,他引:2
Class I transplantation antigens form complexes with a virus protein encoded in the early region E3 of the adenovirus-2 genome. The interaction between this viral glycoprotein, E19, and nascent human class I antigens has been examined by microinjecting purified mRNA into Xenopus laevis oocytes. Both E19 and the two class I antigen subunits, the heavy chain and beta 2-microglobulin (beta 2M), were efficiently translated. The heavy chains did not become terminally glycosylated, as monitored by endoglycosidase H digestion, and were not expressed on the oocyte surface unless they were associated with beta 2M. The E19 protein did not become terminally glycosylated, and we failed to detect this viral protein on the surface of the oocytes. Co-translation of heavy chain and E19 mRNA demonstrated that the two proteins associate intracellularly. However, neither protein appeared to be transported to the trans-Golgi compartment. Similar observations were made in adenovirus-infected HeLa cells. Heavy chains bound to beta 2M became terminally glycosylated in oocytes in the presence of low concentrations of E19. At high concentrations of the viral protein, no carbohydrate modifications and no cell surface expression of class I antigens were apparent. Thus, beta 2M and E19 have opposite effects on the intracellular transport of the heavy chains. These data suggest that adenovirus-2 may impede the cell surface expression of class I antigens to escape immune surveillance. 相似文献
39.
40.
Recognition of Superior Photosynthetic Efficiency in the Field Using the CO(2)-Depletion Technique 下载免费PDF全文
The relationship between CO2 exchange rate (CER) and growth of crops in the field was investigated in Connecticut Broadleaf tobacco (Nicotiana tabacum) using the CO2-depletion technique. A particular objective was to determine if modest (i.e. <10%) varietal differences could be distinguished in mean CER. Statistical analysis of numerous CER values obtained over a wide range of irradiances during the course of the season indicated that differences of as little as 7% in the mean CER between varieties would be significant (n ~400). The usefulness of the CO2-depletion technique in detecting modest differences in photosynthetic efficiency has thus been demonstrated. These results are discussed in relation to the prospects for introducing and detecting genetic traits which would diminish photorespiration and increase CER and growth. 相似文献