全文获取类型
收费全文 | 1225篇 |
免费 | 23篇 |
国内免费 | 94篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 7篇 |
2020年 | 17篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 13篇 |
2016年 | 8篇 |
2015年 | 23篇 |
2014年 | 27篇 |
2013年 | 43篇 |
2012年 | 23篇 |
2011年 | 39篇 |
2010年 | 57篇 |
2009年 | 76篇 |
2008年 | 68篇 |
2007年 | 74篇 |
2006年 | 73篇 |
2005年 | 43篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 33篇 |
2001年 | 35篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 42篇 |
1997年 | 27篇 |
1996年 | 47篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 19篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 31篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 20篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有1342条查询结果,搜索用时 78 毫秒
91.
Four types of tanycytes can be distinguished in the rat hypothalamus: 1 and 2 tanycytes establish an anatomical link between the ventricular cerebrospinal fluid (CSF) and the arcuate nucleus, whereas 1 and 2 tanycytes establish a link between CSF and portal blood. Endocytosis and transcytosis in these cells have been investigated by (1) immunocytochemistry with antibodies against molecular markers of the endocytotic and transcytotic pathways; (2) the administration of wheat germ agglutinin (WGA) into the ventricular or subarachnoidal CSF and following its internalisation by and its routing through tanycytes. The four populations of tanycytes show marked differences concerning the expression and subcellular location of proteins involved in endocytosis and transcytosis, such as clathrin, caveolin-1, Rab4 and ARF6. Thus, 1,2 tanycytes express caveolin-1 at the ventricular cell pole and at their terminals contacting the portal capillaries, whereas 1,2 tanycytes do not, suggesting that caveolae-dependant endocytosis does not occur in the latter and that, in 1,2 tanycytes, it may occur at both cell poles. In 1,2 tanycytes, clathrin is only expressed at the ventricular cell pole indicating that clathrin-dependant endocytosis operates for compounds present in the ventricular CSF and not for those exposed to the terminals. This agrees with the property of 1,2 tanycytes of internalising WGA through the ventricular cell pole but not through the terminals. The subcellular distribution in 1,2 tanycytes of WGA and of the proteins clathrin and Rab4 indicates that part of the internalised WGA follows the degradative pathway and part is sorted to a transcytotic pathway and that the transcytotic and the secretory pathways might intersect. Financial support was provided by grants 01/1050, from FIS, Spain (to J.L.B.) and 1030265, from FONDECYT, Chile (to E.M.R.) 相似文献
92.
Ohyama C Hosono M Nitta K Oh-eda M Yoshikawa K Habuchi T Arai Y Fukuda M 《Glycobiology》2004,14(8):671-679
Serum prostate-specific antigen (PSA) assay is widely used for detection of prostate cancer. Because PSA is also synthesized from normal prostate, false positive diagnosis cannot be avoided by the conventional serum PSA test. To apply the cancer-associated carbohydrate alteration to the improvement of PSA assay, we first elucidated the structures of PSA purified from human seminal fluid. The predominant core structure of N-glycans of seminal fluid PSA was a complex type biantennary oligosaccharide and was consistent with the structure reported previously. However, we found the sialic acid alpha2-3 galactose linkage as an additional terminal carbohydrate structure on seminal fluid PSA. We then analyzed the carbohydrate moiety of serum PSA from the patients with prostate cancer and benign prostate hypertrophy using lectin affinity chromatography. Lectin binding was assessed by lectin affinity column chromatography followed by determining the amount of total and free PSA. Concanavalin A, Lens culinaris, Aleuria aurantia, Sambucus nigra, and Maackia amurensis lectins were tested for their binding to the carbohydrates on PSA. Among the lectins examined, the M. amurensis agglutinin-bound fraction of free serum PSA is increased in prostate cancer patients compared to benign prostate hypertrophy patients. The binding of PSA to M. amurensis agglutinin, which recognizes alpha2,3-linked sialic acid, was also confirmed by surface plasmon resonance analysis. These results suggest that the differential binding of free serum PSA to M. amurensis agglutinin lectin between prostate cancer and benign prostate hypertrophy could be a potential measure for diagnosis of prostate cancer. 相似文献
93.
D.?EgamberdiyevaEmail author D.?Qarshieva K.?Davranov 《Journal of Plant Growth Regulation》2004,23(1):54-57
In this work the effect of inoculation with Bradyrhizobium japonicum S2492 on soybean (Glycine max (L) Merr) growth, nodulation and yield in nitrogen-deficient soil of Uzbekistan was studied. The field experiments were carried out in Tashkent Province of Uzbekistan in a randomized complete block design with four replicates of each treatment. The results revealed positive effects on growth, nodule number and yields of soybean after inoculation with B. japonicum S2492. The yield of soybean varieties was 48% higher for inoculated than for uninoculated plants. The effect of the inoculation was specific for variety but not for growth type. The protein and oil contents of seeds also increased after inoculation. It was concluded that B. japonicum S2492 can be considered as a biofertilizer for increasing the productivity of soybean in nitrogen-deficient soils in Uzbekistan. 相似文献
94.
95.
Intra- and inter-specific effects of cotton, soybean, and clover on the time until death of Helicoverpa zea (Boddie) and Heliothis virescens (F.) larvae lethally infected with H. zea nucleopolyhedrovirus (HzSNPV) were evaluated in the laboratory. In the first test, on second instar only, the time until death of lethally infected larvae of both species differed with the plant tissues (vegetative or reproductive) and plant species. The total viral activity produced per larva in LC(50) units (occluded viral bodies (OBs) per larva/LC(50) in OBs/mm(2) of diet surface) was greater from H. virescens larvae fed vegetative than reproductive tissues of all host plants, but from H. zea virus production was greater only when fed vegetative tissue of soybean. In a second test that compared second and fourth instar H. virescens on cotton, total viral activity from larvae treated in both instars was greater when fed vegetative than reproductive tissues. Results of these tests suggest that the ability of host plants to influence baculovirus disease is more complex than previously believed. When examining the epizootic potential of a baculovirus, more attention must be given to the effects of the host plant on the insect-virus interactions. 相似文献
96.
Molecular species of glycinin in some soybean cultivars 总被引:3,自引:0,他引:3
A(4) polypeptide-containing (Shirotsurunoko and York) and A(4) polypeptide-lacking (Raiden and Suzuyutaka) soybean cultivars were used to investigate the heterogeneity of glycinin molecular species. Purification of glycinin by DEAE-Toyopearl column chromatography afforded molecular species eluting before the glycinin fraction. Analysis of this fraction by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and sucrose density gradient centrifugation indicated that this protein consisted of A(1) and A(2) polypeptides. The A(4)-containing soybean cultivars contained less of this protein than the A(4)-lacking soybean cultivars, as exhibited by the size of the early peak appearing during column chromatography. Alkaline PAGE and N-terminal amino acid sequence analysis confirmed that the A(1)- and A(2)-rich molecular species in the A(4) polypeptide-lacking cultivars consisted of the A(1a) and A(2) polypeptides. Estimation of the molecular mass by gel permeation chromatography and multi-angle laser light scattering (GPC-MALLS) indicated that the A(1a)- and A(2)-rich molecular species were similar to a monomer of glycinin. 相似文献
97.
Sonication-assisted Agrobacterium-mediated transformation of soybean [Glycine max (L.) Merrill] embryogenic suspension culture tissue 总被引:12,自引:0,他引:12
Successful transformation of plant tissue using Agrobacterium relies on several factors including bacterial infection, host recognition, and transformation competency of the target tissue.
Although soybean [Glycine max (L.) Merrill] embryogenic suspension cultures have been transformed via particle bombardment, Agrobacterium-mediated transformation of this tissue has not been demonstrated. We report here transformation of embryogenic suspension
cultures of soybean using “Sonication-Assisted Agrobacterium-mediated Transformation” (SAAT). For SAAT of suspension culture tissue, 10–20 embryogenic clumps (2–4 mm in diameter) were
inoculated with 1 ml of diluted (OD600nm 0.1–0.5) log phase Agrobacterium and sonicated for 0–300 s. After 2 days of co-culture in a maintenance medium containing 100 μM acetosyringone, the medium was removed and replaced with fresh maintenance medium containing 400 mg/l Timentin?. Two weeks after SAAT, the tissue was placed in maintenance medium containing 20 mg/l hygromycin and 400 mg/l Timentin?, and the medium was replenished every week thereafter. Transgenic clones were observed and isolated 6–8 weeks following SAAT.
When SAAT was not used, hygromycin-resistant clones were not obtained. Southern hybridization analyses of transformed embryogenic
tissue confirmed T-DNA integration.
Received: 22 August 1997 / Revision received: 22 October 1997 / Accepted: 11 November 1997 相似文献
98.
The interaction between Urtica dioica agglutinin (UDA) and N-acetylglucosamine (GlcNAc) and its (1-4)-linked oligomers was studied by fluorescence titration and isothermal titration microcalorimetry. UDA possesses one significant binding site that can be measured calorimetrically. This site is composed of three subsites, each subsite accommodating one GlcNAc residue. The interaction is enthalpically driven, and the binding area of UDA is characterized by a H of interaction for a given oligosaccharide considerably smaller than that of wheat germ agglutinin (WGA), despite the fact that they both belong to a family of proteins composed entirely of hevein domains. Relatively high Cp values of the UDA-carbohydrate interactions and more favorable entropy term compared to WGA suggest that binding of the carbohydrate ligands by UDA has a higher hydrophobic component than that of WGA. 相似文献
99.
The pyrolysis reactions of soybean oils have been studied. The pyrolytic products were analyzed by GC–MS and FTIR and show the formation of olefins, paraffins, carboxylic acids and aldehydes. Several kinds of catalysts were compared. It was found that the amounts of carboxylic acids and aldehydes were significantly decreased by using base catalysts such as Na2CO3 and K2CO3. The low acid value pyrolytic products showed good cold flow properties and good solubility in diesel oil at low temperature. The results presented in this work have shown that the pyrolysis of soybean oils generates fuels that have chemical composition similar to petroleum based fuels. 相似文献
100.
AFM observation of single,functioning ionotropic glutamate receptors reconstituted in lipid bilayers
Nahoko Kasai Chandra S. Ramanujan Ichiro Fujimoto Akiyoshi Shimada John F. Ryan Keiichi Torimitsu 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010