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排序方式: 共有654条查询结果,搜索用时 15 毫秒
1.
The differentiation of spermatids in the marmoset (Callithrix jacchus, n = 9) testis is described here at the light-microscopic level employing serial semithin sections. The definition of 8 different phases of spermiogenesis, i.e. the formation of spermatids, is based upon the changes in the development of nucleus, acrosome and flagellum. 相似文献
2.
Vasant Chellappa Kendra N. Taylor Kathryn Pedrick Carlos Donado Ilka Arun Netravali Khaleda Haider Annaiah Cariappa Natasha F. Dalomba Shiv Pillai 《PloS one》2013,8(1)
Catalytically defective rare variants of Sialic acid Acetyl Esterase (SIAE) have previously been linked to autoimmunity. Studies presented here confirm that the M89V SIAE protein and all other products of common variant alleles of SIAE are catalytically normal. Although overexpressing transfected non-lymphoid cells secrete small amounts of SIAE that can associate with the cell surface, normal human lymphocytes do not exhibit cell surface SIAE, supporting genetic evidence in mice that indicates that this protein functions in a lymphocyte intrinsic manner. Analyses of the plasma proteome also indicate that SIAE is not secreted in vivo. A re-analysis exclusively of catalytically defective rare variant alleles of SIAE in subjects in which this gene was completely sequenced confirmed an association of SIAE with autoimmunity. A subset of catalytically defective rare variant SIAE alleles has previously been typed in a large genotyping study comparing a diverse group of disease subjects and controls; our re-analysis of this data shows that catalytically defective alleles are enriched in disease subjects. These data suggest that SIAE may be associated with autoimmunity and that further study of catalytically defective rare variant SIAE alleles in terms of autoimmune disease susceptibility is strongly warranted. 相似文献
3.
An insecticidal protein gene from Bacillus thuringiensis var. aizawal was cloned in Escherichia coli. The cloned gene expressed at a high level and the synthesized protein appeared as an insoluble, phase-bright inclusion in the cytoplasm. These inclusions were isolated by density gradient centrifugation, the isolated protein was activated in vitro by different proteloytic regimes and the toxicity of the resulting preparations was studied using insect cells grown in tissue culture. The inclusions consisted of a 130 kDa polypeptide which was processed to a protease-resist-ant 55 kDa protein by tryptic digestion. This preparation lysed lepidopteran (Choristoneura fumiferana) CFI ceils but not dipteran (Aedes albopictus) calls. When the crystal protein was activated by sequential treatment, first with trypsin and then with Aedes aegypti gut proteases, the resulting 53 kDa polypeptide was now toxic only to the dipteran cells and not to the lepidopteran cells. Thus the dual specificity of this var. aizawal toxin results from differential proteolytic processing of a single protoxin. The trypsin-activated preparation was weakly active against Spodoptera frugiperda cells. Membrane binding studies of the trypsin-activated toxin revealed a 68 kDa protein in the lepidopteran ceil membranes, which may be the receptor for this toxin. 相似文献
4.
Dr. Nuzha M. Al-Taho Sami H. Al-Amad Fadilah A. Al-Salameen Ekkehard Spanier Mohammad Z. Haider 《Current microbiology》1991,22(3):199-202
Fourteen recombinant plasmids were constructed by inserting fragments of pSAS, a naturally occurring plasmid ofMethylophilus spp. KISRI-5, into the multiple cloning sites of pUC19. Six recombinants and three knownEscherichia coli plasmids were used to transform three thermotolerant methylotrophic KISRI strains by use of an optimized protocol of electroporation. Analysis of transformants for plasmid DNA showed that all plasmids were stable in the methylotrophic hosts. These studies offer opportunities to developMethylophilus spp. as host-vector systems. 相似文献
5.
Mutagenesis has been used to investigate the toxicity and specificity of a larvicidal protein from Bacillus thuringiensis aizawai IC1 that is toxic to both lepidoptera and diptera and differs by only three residues from a monospecific lepidopteran toxin from B. thuringiensis berliner. Site-directed mutagenesis was used to investigate the contribution of these residues to the dual specificity of the aizawai protein. The results suggest that changes in the identity of residues adjacent to Arg544 and Arg567 on the C-terminal side may convert a monospecific toxin into a dual specificity toxin by altering the protease sensitivity of the arginyl peptide bond. A series of deletion mutants was constructed and their protein products analysed for toxicity in vitro and in vivo and for their ability to perturb phospholipid bilayers. The results indicate a different functional role for various protein segments in the toxin's mode of action and suggest that two separate regions close to the C terminus of the active toxin are important in conferring dual specificity on the aizawai IC1 toxin. A model suggesting a basis for the activity of monospecific and dual-specificity B. thuringiensis toxins is presented, which postulates that association of sequences at the C terminus of the active toxin with regions near the N terminus may be responsible for determining toxin specificity. 相似文献
6.
7.
The effects of theophylline (a phosphodiesterase inhibitor) and cAMP on 17α, 20ß-dihydroxy-4-pregnen-3-one-induced germinal vesicle breakdown was investigatedin vitro in catfish (Clarias batrachus) oocytes. Folliculated oocytes incubated with 17α, 20ß-dihydroxy-4-pregnen-3-one at the concentration of 1 μg/ml induced 93.2 ± 2.23% germinal vesicle breakdown. When the oocytes were prestimulated with 17α,20ß-dihydroxy-4-pregnen-3-one for 6 h and then treated with different concentrations of theophylline, there was a significant drop in the frequency of germinal vesicle breakdown at the concentrations 2.0, 1.5 and 1.0 mM. However, theophylline was found to be incapable of inhibiting germinal vesicle breakdown at its lowest concentration (0.5 inM). In the time course study, significant inhibition of germinal vesicle breakdown was recorded when 1 mM theophylline was added up to 30 h of 17α,20ß-dihydroxy-4-pregnen-3-one Stimulation but the inhibitory effect of theophylline gradually (time dependent manner) declined if the stimulatory time of 17α,20ß-dihydroxy-4-pregnen-3-one was increased. A similar inhibition of germinal vesicle breakdown was also recorded with various concentrations of cAMP. Except 0.5 mM, all the higher concentrations of cAMP significantly inhibited 17α,20ß-dihydroxy-4-pregnen-3-one induced germinal vesicle breakdown. 相似文献
8.
The interspecific interactions of Meloidogyne javanica with races 1, 2, 3, and 4 of M. incognita on tomato were determined. Impacts of the interactions on fecundity and morphometrics of females were also examined. Mutually inhibitory interactions occurred between M. javanica and the races of M. incognita, but the negative interactions did not reflect in plant growth. Numbers of root galls, egg masses, mature females, total population, fecundity, and reproduction factor declined in concomitant treatments, but the morphometrics of the females remained unaltered. In general, mutual suppressive effects in all parameters were smaller for M. javanica than M. incognita, but some variations occurred among the races of M. incognita. Race 2 appeared to be more competitive than other races. The interaction between the species was not intense; therefore, the species coexist in mixed populations in agricultural fields. 相似文献
9.
The effects of five different gonadotropins and homologous pituitary homogenate (HP) on germinal vesicle breakdown (GVBD) were investigated in vitro using folliculated oocytes of Clarias batrachus. Among all the gonadotropins, salmon gonadotropin (SG-G100) was the most potent in vitro inducer of oocyte maturation. At concentrations of 1, 0.1, 0.01 and 0.001 microgram/ml it induced 86.98 +/- 2.71, 68.74 +/- 2.85, 44.56 +/- 1.75 and 25.90 +/- 2.36% GVBD. Next to SG-G100 in inducing GVBD was luteinizing hormone (LH) which was consistently found to be effective at all the concentrations used. Human chorionic gonadotropin was also found to be effective at all the concentrations but when compared to SG-G100 and LH, it was less effective. Follicle stimulating hormone and pregnant mare serum gonadotropin were found to be effective at higher concentrations but were ineffective at the lowest concentration. HP treatment resulted in a significant number of GVBD at all the three concentrations used. 相似文献
10.
H G Goslar B Hilscher S G Haider N Hofmann D Passia W Hilscher 《The journal of histochemistry and cytochemistry》1982,30(12):1268-1274
Two forms of human Sertoli cell disorders were characterized enzyme histochemically from the testicular biopsy material of infertile and subfertile patients. Sertoli cell asthenia: a slight injury of the Sertoli cell with exfoliation of individual germ cells; marked by the rarefaction of reaction zones of thiamine pyrophosphatase (TPPase) and a decrease in lactate dehydrogenase (LDH). Sertoli cell insufficiency: severe Sertoli cell damage with the formation of a "puff" and a heavy exfoliation of germ cells (dislocation of Sertoli cell nucleus and cytoplasm along with the related germ cells into the lumen of seminiferous tubule); marked by a heterogeneous activity pattern of TPPase, the disappearance of LDH, maintenance of a slightly weakened activity of alkaline phosphatase, and an increase of acid phosphatase. In the case of Sertoli-cell-only syndrome, the high prismatic Sertoli cells showed strong acid phosphatase activity with scattered weak TPPase reaction, whereas the flat or cube-like Sertoli cells exhibited weak acid phosphatase activity with only one small round reaction zone of TPPase in each cell. In addition, the frequency of the occurrence of Sertoli cell asthenia, Sertoli cell insufficiency, and Sertoli-cell-only syndrome is reported, and its correlation with the andrological diseases discussed. 相似文献