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排序方式: 共有802条查询结果,搜索用时 15 毫秒
1.
The paper deals with the analysis of 2 × 2 table measures and describes several new possibilities for applying them. An estimate is given for HELLMICH's asymmetric K-measure and a possible extension of the contingency concept in a special 2×2 case is presented. The concept introduced and the recommended computer application of the 2×2 table measures is supported by new results obtained for the relationship between jaw joint pains and noises examined earlier by F. SCHMID and C. ZSCHEGE. With a larger number of observations the opportunity arises for a deeper analysis of this dental problem using path analysis. The plan of evaluation and the conncetion between the variables examined is illustrated by a path-diagram. The association tables determined on the basis of the (C) values introduced during the examination of jaw joint disturbances using association analysis draw attention to the special role of the left side of mastication. The paper raises ideas for further generalisations and indicates where further research is needed.  相似文献   
2.
Observations on the behavior of living hominoids show generic differences in the use and posture of the wrist joint. Both orang-utans and hylobatids usually use the wrist in suspensory behaviors. However, orang-utans emphasize markedly adducted and flexed wrist postures, while hylobatids emphasize violent forearm and wrist rotation. African apes, especially the gorilla, use the wrist more frequently than other hominoids for terrestrial quadrupedal weight-bearing. Humans use the wrist less frequently for supportive purposes than do other hominoids. These behavioral differences correspond to structural specializations in the proximal carpal joint of each of the hominoid genera. Although each of the hominoid genera has apparently modified its proximal carpal joint best to serve its characteristic behaviors, all hominoids share a unique proximal carpal joint that permits approximately 160ℴ of forearm rotation. The hylobatid proximal carpal joint is specialized in exhibiting a marked development of those structures limiting forearm rotation, but it is in most respects the least derived— that is, closest to the nonhominoid anthropoids. Chimpanzees show a proximal carpal joint that is more generalized than those of the other great apes but more derived than that of hylobatids. The human and gorilla proximal wrist joints, on the other hand, show marked modifications for weight-bearing in terrestrial behaviors. Orang-utans have the most derived proximal carpal joint, which in many respects parallels that of the slow-climbing nonhominoid primates. The comparative anatomy and structural specializations of the wrist joint support (a) an early divergence of hylobatids from the common hominoid stock, (b) a common ancestry for gorillas and humans separate from the other hominoids, and (c) a long independent evolutionary period for orang-utans since their divergence from the common hominoid stock, or one that was marked by strong selection pressures for wrist specializations. Unfortunately, the generalized condition of the chimpanzee’s wrist joint and the very derived condition of the orang-utan wrist provide uncertain evidence as to which of the two was first to diverge from the common hominoid stock. Identification of hominoid wrist specializations as reflecting real phylogenetic relationships or parallelisms depends on how well the phytogeny inferred from wrist morphology accords with those arrived at from the study of other systems.  相似文献   
3.
This study considers the current concept of the mandible as a lever of the third order. The concept requires a fulcrum, and this function has been ascribed to the condyle region, but it tends to be overlooked that the fulcrum of a third-order lever in this case would sometimes have to bear a considerable stress. Certain changes, attributed to stress, have been observed in anatomical components of the articulation, but they cannot be explained in terms of the lever concept. They are accounted for by the changing anatomical relations in the working and contralateral sides during mandibular function. They arise from minor stress, especially when dental conditions indicate a period of abnormal function.  相似文献   
4.
Brassinosteroid (BR)-induced rice (Oriza sativa L.) lamina joint (RLJ) inclination and its relationship to indole-3-acetic acid (IAA) and ethylene were investigated using BR isolated from beeswax. The effect of BR on RLJ inclination was time- and concentration-dependent. Etiolated lamina were more sensitive to BR than green lamina. The BR-induced inclination was accompanied by increased lamina fresh weight, total water content, free-water content, proton extrusion and ethylene production, and decreased bound-water content. Lamina dry weight was not changed. The inclination was due to greater expansion of the adaxial cells relative to the dorsal cells in the lamina joint. This response was caused by BR and/or BR-induced signal(s) that were transported from the leaf sheath to the leaf blade. Both BR-induced RLJ inclination and ethylene production were inhibited by cobalt chloride (CoCl2), an inhibitor of ACC oxidase. BR-induced inclination was much higher than that of IAA, and was inhibited by high concentration of 2,3,5-triiodobenzoic acid (TIBA), an inhibitor of IAA transport. A synergistic effect was observed between BR and IAA. These results suggest that the effects of BR on RLJ inclination and pulvinus cell expansion may be resulted from BR-increased water potential and proton extrusion in the lamina. The BR-induced RLJ inclination may involve the action of ethylene but may be independent of IAA.Abbreviations BR brassinolide or brassinosteroid(s) - IAA indole-3-acetic acid - TIBA 2,3,5-triiodobenzoic acid - RLJ rice lamina joint  相似文献   
5.
G Skogman  J Nilsson  P Gustafsson 《Gene》1983,23(2):105-115
The stability of different derivatives of plasmid vectors pBR322 and pACYC184 carrying the tryptophan operon of Escherichia coli was monitored in various media. It was found that in the absence of any special selective pressure, all plasmids were lost from the culture. The stability varied depending both on the orientation of the inserted tryptophan fragment and the growth media used. The pBR322::trp+ plasmids were lost at an average frequency of 0.3 to 0.8% per cell generation, while the pACYC184::trp+ plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost at a rate higher than 5%. In all cases the whole plasmid was lost, indicating a high stability of the plasmid::cloned DNA as such. To increase the stability of the cloning vectors, the partition locus of plasmid pSC101 was added to both the pBR322::trp+ and pACYC184::trp+ plasmids. The addition of this gene increased the replicon stability at least 3- to 10-fold, with the pBR322::trp+-par+ plasmids being the most stable. Also in this case, the stability was dependent on the plasmid type and on the growth medium. In no case was there a discoordinate loss of the antibiotic-resistance and tryptophan genes from the vectors.  相似文献   
6.
A novel plasmid vector that is able to replicate both in Escherichia coli and in Streptococcus sanguis is described. This 9.2-kb plasmid, designated pVA856, carries Cmr, Tcr and Emr determinants that are expressed in E. coli. Only the Emr determinant is expressed in S. sanguis. Both the Cmr and the Tcr of pVA856 may be insertionally inactivated. This plasmid affords several different cleavage-ligation strategies for cloning in E. coli followed by subsequent introduction of chimeras in to S. sanguis. In addition, we have modified a previously described E. coli-S. sanguis shuttle plasmid [pVA838; Macrina et al., Gene 19 (1982) 345–353], so that it is unable to replicate in S. sanguis. The utility of such a plasmid for cloning and selecting sequences enabling autonomous replication in S. sanguis is demonstrated.  相似文献   
7.
H Ohtsubo  B Vassino  T Ryder  E Ohtsubo 《Gene》1982,20(2):245-254
This paper describes a simple method for the isolation of small plasmids of various sizes from pSMI, a derivative of the resistance plasmid R 100. The method is based on the observation that a repressor-negative mutant of the ampicillin-resistance (ampr) transposon Tn3, Tn3 No. 5, mediates cointegration of a plasmid carrying Tn 3 No. 5 (pMB8::Tn 3 No. 5) into virtually any site on pSMI. The resulting cointegrate plasmids contain the pSMI sequence which is joined with the ampr gene of the Tn 3 mutant. This cointegration is so frequent that large cointegrate plasmids can be readily detected in the total plasmid DNA prepared from cells carrying pSMI and pMB8::Tn3 No. 5. We were able to isolate small plasmids of various sizes by digesting the total plasmid DNAs with restriction endonucleases which cut both pSM 1 and Tn3 No. 5 sequences present in the cointegrates and subsequently ligating the restriction fragment containing both the ampr gene and the region necessary for replication of pSMI. Analysis of these plasmids, named pBV plasmids, with restriction endonucleases and by nucleotide sequencing allowed us to determine regions necessary or unnecessary for replication, thus defining a minimal replication region of pSMI. The present method is generally useful for the isolation of small derivatives from any large plasmid for the study of genes and sites adjacent to or within the minimal replication region of the plasmid.  相似文献   
8.
9.
大豆对斜纹夜蛾幼虫抗性遗传的发展表达过程   总被引:10,自引:1,他引:10  
采用植物数量性状遗传体系分离分析方法,通过4个感抗杂交组合研究了在网室人工接入斜纹夜蛾幼虫的条件下大豆抗斜纹夜蛾植株反应发育过程的遗传。不论P1、P2、F1、F2、F2:3多世代联合分析或单个分离世代分析,结果均表明大豆对斜纹夜蛾幼虫的抗性为两对主基因 多基因遗传模式。但在大豆生长发育的不同时期,随害虫数量的变化,其抗虫性遗传呈动态变化过程。在两对主基因充分表达日期,主基因的遗传率较高,达70.40%-99.21%,环境影响较小;多基因遗遗传率较低,为0.00%-22.29%。  相似文献   
10.
The divide between attributional and consequential research perspectives partly overlaps with the long‐standing methodological discussions in the life cycle assessment (LCA) and input‐output analysis (IO) research communities on the choice of techniques and models for dealing with situations of coproduction. The recent harmonization of LCA allocations and IO constructs revealed a more diverse set of coproduction models than had previously been understood. This increased flexibility and transparency in inventory modeling warrants a re‐evaluation of the treatment of coproduction in analyses with attributional and consequential perspectives. In the present article, the main types of coproductions situations and of coproduction models are reviewed, along with key desirable characteristics of attributional and consequential studies. A concordance analysis leads to clear recommendations, which call for important refinements to current guidelines for both LCA/IO practitioners and database developers. We notably challenge the simple association between, on the one hand, attributional LCA and partition allocation, and on the one hand, consequential LCA and substitution modeling.  相似文献   
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