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121.
122.
Cores were collected from dominant pondcypress trees growing in a swamp that had received sewage effluent for 7 yr and a nearby control swamp to determine the combined effects of changes in nutrient supply and hydrologic regime on tree growth. The cores were used to measure two indices of tree growth: basal area increment (BAI) and relative basal area increment (RBAI, which accounts for differences in growth due to the size of teh tree) between 1970–1983 while one swamp remained untreated and the other received weekly additions of sewage effluent from 1974–1981. Throughout the whole period, the mean BAI and RBAI of pond-cypress trees in the untreated swamp remained unchanged, ranging between 5.55–6.38 cm2 yr–1 and 1.09–1.27% yr–1, respectively. In contrast, trees in the treated swamp increased their BAI approximately two-fold from 7.40 cm2 yr–1 prior to treatment to 14.83 cm2 yr–1 after the onset of treatment and maintained this rate of growth in the 2 yr period after cessation of treatment. Relative basal area increment showed a similar response, but the proportional increase due to treatment was less (1.5-fold factor) than for BAI. The response of pondcypress trees to the sewage effluent differed depending upon whether the trees were located in the deep or shallow water zones. Trees in the deep zone of the treated swamp had lower BAIs and RBAIs than those in the shallow zone during the treatment period, whereas in pre- and post-treatment periods growth indices were equal in both zones. No significant differences in growth between deep and shallow zones were observed during all three time periods in the control swamp. 相似文献
123.
Michael P. Lisanti Enrique Rodriguez-Boulan Alan R. Saltiel 《The Journal of membrane biology》1990,117(1):1-10
Conclusion Experimental evidence has accumulated over the past few years to suggest that the GPI protein anchor may play a broad role in the regulation of membrane protein function. The significant changes in the biophysical properties of proteins that are membrane-anchored through GPI in lieu of a hydrophobic transmembrane peptide indicates a variety phobic transmembrane peptide indicates a variety of potential new functions served by the anchor structure itself. Moreover, the number of structural variations within the family of GPI molecules indicates a further opportunity for subspecialization of such anchored proteins, especially regarding cellular localization, mobility, metabolism and susceptibility to enzymatically-induced release. It is likely that further exploration of the structure and function of the GPI anchor may reveal additional roles for this unusual mechanism of membrane-protein attachment. 相似文献
124.
正常情况下处于S期的CFU-S比例低于10%。氨甲酰胆碱(Cach 10~(-13)—10~(-9)mol/L)和Impromidine(Impro 10~(-9)—10~(-4)mol/L)在体外与小鼠骨髓细胞短时培育后,增加了CFU-S对细胞毒剂羟基脲的敏感性。反应最大时,9d和13dCFU-S的减少率分别是32.8和60.6%(Cach)以及38.4和49.5%(Impro)。这种效应可分别被胆碱能N受体阻断剂筒箭毒(10~(-6)mol/L)和组胺H_2受体阻断剂甲氰咪呱(10~(-6)mol/L)所阻断,表明9d和13d CFU-S表面胆碱能N受体和组胺H_2受体的密度或活性存在差别,再次证实了CFU-S是一个不均一的细胞群。 相似文献
125.
贵州普定白岩脚洞石片的初步研究 总被引:4,自引:3,他引:1
本文对贵州普定白岩脚洞遗址中所获的1220件石片进行了分类观察。根据石片背面石皮的保存情况,疤与疤之间的关系,背疤的受力部位与石片台面的关系等特征,可从一个侧面反映出石核的利用率较高。 相似文献
126.
SYED Z. HUSAIN F.L.S. PETAR D. MARIN EDOMIL ILI M. QAISER BRANIMIR PETCOVIC 《Botanical journal of the Linnean Society. Linnean Society of London》1990,103(1):59-80
HUSAIN, S. Z., MARIN, P. D., ŠILIĆ, Č., QAISER, M. & PETCOVIĆ, B., 1990. A micromorphological study of some representative genera in the tribe Saturejeae (Lamiaceae). The Old World genera in the tribe Saturejeae are usually distributed either in Europe and North Africa or in the temperate parts of Asia. The centres of distribution of investigated genera are mainly in the Mediterranean region. In taxonomic revisions very little reference is made to micromorphological characters, in particular, to nutlets and leaf indumentum, in spite of the stability of these characters. Scanning electron microscopy of nutlet surface and patterns of leaf indumentum show a wide range of variation, not only among genera, but also at lower levels of classification. In view of this, nutlet surface and leaf indumentum structure, as seen with the SEM, of representative species of eight genera in the tribe Saturejeae provides useful additional character combinations in delimiting these closely related genera. This study also supports Boissier's delimitation of sections Micromeria and Pseudomelissa. 相似文献
127.
Growth of Pyrola rotundifolia ssp. maritima in relation to shade 总被引:2,自引:2,他引:0
128.
Tryptophan (Trp) surface topography of the red- and far-red-absorbing forms of phytochrome (Pr, Pfr) ofAvena sativa L. has been investigated by analyzing quenching of the two components of Trp fluorescence decay, in order to understand the
differences in the two forms at the molecular level. Stern-Volmer kinetic analysis of the quenching data for two cationic
surface quenchers, Cs+ and Tl+, showed strong quenching of the short component of the Pr fluorescence (Stern-Volmer constants,K
sv
, 27.2 and 21.4 M−1, respectively) relative to that of Pfr fluorescenceK
sv
, 10.4 and 12.3 M−1, respectively). The long component of the Trp fluorescence was quenched differentially by Cs+ and Tl+, withK
sv
of 9.0 and 19.8 M−1, respectively, for the Pr fluorescence andK
sv
of 13.7 and 8.7 M−1, respectively, for the Pfr fluorescence. The results indicate that the phytochrome Trp residues with short fluorescence lifetime
are more accessible to the cationic surface quenchers than those with long fluorescence lifetime. The data, taken together
with our earlier study (Singh et al. 1988, Biochim, Biophys. Acta936, 395–405), indicate that most, if not all the ten Trp residues of phytochrome, are fluorescent and exist in distinct groups
differing in their topography and microenvironment, and the peptide segment containing Trp-774 and Trp-778 within the 55-kilodalton
C-terminal domain of phytochrome also undergoes a subtle alteration in its surface topography during Pr→Pfr phototransformation.
This paper is dedicated to Professor Hans Mohr in commemoration of his 60th birthday 相似文献
129.
Spatiotemporal patterns of expression of the cell-surface arabinogalactan-protein epitope defined by monoclonal antibody JIM4 (J.P. Knox et al., 1989, Development 106, 47–56) have been characterized by indirect immunofluorescence during the process of somatic embryogenesis in Daucus carota L. The JIM 4 epitope (J4e) occurred on cells established in culture from hypocotyl explants which appeared to derive, at least in part, from the epidermal cells of the hypocotyl. Cultures maintained in the presence of 2,4-dichlorophenoxyacetic acid developed proembryogenic masses of which only infrequent cells at the surface expressed J4e. Sub-culture at a low cell density and withdrawl of the synthetic auxin resulted in an increase in J4e expression in most surface cells and most abundantly in surface layers of cells at the future shoot end of developing embryos. The transition to heart-shaped embryos occurred concurrently with the expression of J4e by groups of cells beneath the developing cotyledons, at the junction of the future root and shoot. At this stage, J4e was also expressed by a single well-defined layer of cells at the surface of the embryos. Advancement to the mature torpedo stage was accompanied by the expression of the epitope on cells forming two regions of the future stele and of cells associated with the cotyledonary provascular tissue characteristic of the carrot seedling. At this stage there was substantially less expression of the marker antigen by epidermal cells, although infrequent expression by isolated cells of the epidermis was maintained. The correlation of J4e expression with the development and distinction of plant tissue patterns during somatic embryogenesis indicates a role for plasma-membrane arabinogalactan proteins in these processes.Abbreviations AGP
arabinogalactan protein
- 2,4-D
2,4-di-chlorophenoxyacetic acid
- J4e
JIM 4 epitope
- PEM
proembryogenic mass
We thank Andrew Davis for photographic assistance and Roger Pennell for useful discussions. 相似文献
130.
一类阔叶树叶面积的通用公式测算法 总被引:2,自引:0,他引:2
本文在观察和测算的基础上,提出了一类阔叶树的叶形方程,并对方程进行积分,求出了计算这类阔叶树叶面积的通用公式。从1980年应用至今证明,用这个通用公式计算这类阔叶树的面积,方便、简捷、精度高,现介绍如下。 相似文献