全文获取类型
收费全文 | 1263篇 |
免费 | 84篇 |
国内免费 | 1篇 |
专业分类
1348篇 |
出版年
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 35篇 |
2014年 | 46篇 |
2013年 | 94篇 |
2012年 | 101篇 |
2011年 | 93篇 |
2010年 | 60篇 |
2009年 | 45篇 |
2008年 | 81篇 |
2007年 | 69篇 |
2006年 | 73篇 |
2005年 | 77篇 |
2004年 | 65篇 |
2003年 | 56篇 |
2002年 | 41篇 |
2001年 | 13篇 |
2000年 | 33篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1967年 | 5篇 |
1966年 | 3篇 |
排序方式: 共有1348条查询结果,搜索用时 0 毫秒
1.
Hiroyuki Kozu Isao Kobayashi Mitsutoshi Nakajima Kunihiko Uemura Seigo Sato Sosaku Ichikawa 《Food biophysics》2010,5(4):330-336
This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis.
We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric
walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function
defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity
of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly
affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to
gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately
20 s−1 in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass
transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The
visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric
walls with an intragastric fluid. 相似文献
2.
Aileen F. G. Bongat Rina Saksena Roberto Adamo Yukari Fujimoto Zenyu Shiokawa Dwight C. Peterson Koichi Fukase Willie F. Vann Pavol Kováč 《Glycoconjugate journal》2010,27(1):69-77
Using recombinant tetanus toxin HC fragment (rTT-HC) as carrier, we prepared multimeric bivalent immunogens featuring the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Ogawa, in combination with either the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Inaba, or a synthetic disaccharide tetrapeptide peptidoglycan fragment as adjuvant. The conjugation reaction
was effected by squaric acid chemistry and monitored in virtually real time by SELDI-TOF MS. In this way, we could prepare
well-defined immunogens with predictable carbohydrate–carrier ratio, whose molecular mass and the amount of each saccharide attached could be independently determined. The ability to prepare such neoglycoconjugates opens unprecedented possibilities
for preparation of conjugate vaccines for bacterial diseases from synthetic carbohydrates. 相似文献
3.
Cloning and sequencing of Schizosaccharomyces pombe DNA topoisomerase I gene, and effect of gene disruption. 总被引:18,自引:7,他引:11
We cloned the structural gene topl+ for Schizosaccharomyces pombe DNA topoisomerase I (topo I) by hybridization. An eight-fold increase of topo I relaxing activity was obtained in S. pombe cells transformed with multicopy plasmid with topl+ insert. Nucleotide sequence determination showed a hypothetical coding frame interrupted by two short introns, encoding a 812 residue polypeptide (M.W. 94,000), 43 residues longer than and 47% homologous to Saccharomyces cerevisiae topo I. We show that the topl (null) strain made by gene disruption is viable, although its generation time is 20% longer than that of wild type. The topl locus is mapped in the long arm of chromosome II, using the Leu+ marker integrated with the cloned topl+ sequence. We constructed a double mutant topl (null) top2 (ts) and found its defective phenotype similar to that of previously obtained topl (heat sensitive) top2 (ts). The other double mutant topl (null) top2 (cs), however, was lethal. Our results suggest that topl+ gene of S. pombe is dispensable only if topo II activity is abundant. 相似文献
4.
Calyculin A and okadaic acid: inhibitors of protein phosphatase activity 总被引:44,自引:0,他引:44
H Ishihara B L Martin D L Brautigan H Karaki H Ozaki Y Kato N Fusetani S Watabe K Hashimoto D Uemura 《Biochemical and biophysical research communications》1989,159(3):871-877
Calyculin A and okadaic acid induce contraction in smooth muscle fibers. Okadaic acid is an inhibitor of phosphatase activity and the aims of this study were to determine if calyculin A also inhibits phosphatase and to screen effects of both compounds on various phosphatases. Neither compound inhibited acid or alkaline phosphatases, nor the phosphotyrosine protein phosphatase. Both compounds were potent inhibitors of the catalytic subunit of type-2A phosphatase, with IC50 values of 0.5 to 1 nM. With the catalytic subunit of protein phosphatase type-1, calyculin A was a more effective inhibitor than okadaic acid, IC50 values for calyculin A were about 2 nM and for okadaic acid between 60 and 500 nM. The endogenous phosphatase of smooth muscle myosin B was inhibited by both compounds with IC50 values of 0.3 to 0.7 nM and 15 to 70 nM, for calyculin A and okadaic acid, respectively. The partially purified catalytic subunit from myosin B had IC50 values of 0.7 and 200 nM for calyculin A and okadaic acid, respectively. The pattern of inhibition for the phosphatase in myosin B therefore is similar to that of the type-1 enzyme. 相似文献
5.
H Ariyoshi E Shiba J Kambayashi M Sakon T Tsujinaka Y Uemura T Mori 《Biochemistry international》1991,23(6):1019-1033
Calpeptin (a cell permeable synthetic peptide calpain inhibitor) inhibited the generation of thromboxane B2 (TxB2) by the direct inhibition on Tx synthetase in platelets at the concentrations more than 30 microM. Calpeptin, its analogues and E-64d (EST) were further examined with regard to cell permiability and inhibitory spectra. Among all compounds, only calpeptin inhibited the degradation of substrate proteins of calpain with negligible effect on TxB2 generation in intact platelets at the concentrations less than 30 microM. These concentrations of calpeptin did not inhibit the platelet aggregation, the elevation of [Ca2+], nor the formation of inositol 1,4,5-trisphosphate (IP3) in thrombin or collagen activated platelets. These results indicate that calpain dose not participate in the process of platelet activation induced by thrombin or collagen. 相似文献
6.
Escherichia coli supH suppressor: temperature-sensitive missense suppression caused by an anticodon change in tRNASer2. 总被引:12,自引:5,他引:7 下载免费PDF全文
S Thorbjarnardttir H Uemura T Dingermann T Rafnar S Thorsteinsdttir D Sll G Eggertsson 《Journal of bacteriology》1985,161(1):207-211
We describe the cloning and the DNA sequence of the Escherichia coli supH missense suppressor and of the supD60(Am) suppressor genes. supH is a mutant form of serU which codes for tRNASer2. The supH coding sequence differs from the wild-type sequence by a single nucleotide change which corresponds to the middle position of the anticodon. The CGA anticodon of wild-type tRNA and CUA anticodon of supD tRNA is changed to CAA in supH tRNA, which is expected to recognize the UUG leucine codon. We propose that the supH suppressor causes the insertion of serine in response to this codon. The temperature sensitivity caused by supH may be due to a conformation of the CAA anticodon in the supH tRNASer that is slightly different than that in the corresponding tRNALeu species. 相似文献
7.
Isolation and Characterization of Tonoplast from Chilling-Sensitive Etiolated Seedlings of Vigna radiata L 总被引:2,自引:0,他引:2 下载免费PDF全文
Tonoplasts were isolated in a high purity from etiolated young seedlings of Vigna radiata L. (mung bean) utilizing a sucrose density gradient system. The excised hypocotyls were homogenized in a sorbitol-buffer system and the 3,600 to 156,000g pellets obtained after the differential centrifugations were suspended in a sorbitol medium and loaded on a linear sucrose density gradient. After centrifugation at 89,000g for 2 hours, tonoplasts were banded at the sample load/sucrose interface. Assessed by electron microscopy and marker enzymes, the purity and the quantity were found to be sufficient for biochemical and biophysical analyses. The tonoplasts were associated with NO3−-sensitive and vana-date-insensitive ATPase. The tonoplast ATPase was stimulated by proton ionophores such as carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone and gramicidin D, suggesting a proton-pumping enzyme. In the presence of ATP and Mg2+, a proton gradient was formed in the isolated tonoplast vesicles as assessed by fluorescence quenching of quinacrine. The tonoplasts contained several kinds of mannosylated or glycosylated glycoproteins and a major protein (65 kilodaltons) which was unique to the membranes. 相似文献
8.
9.
Na+-dependent I- transport and I- counterflow were studied using phospholipid vesicles (P-vesicles) made of porcine thyroid plasma membranes and soybean phospholipid by sonication. 1) I- uptake by P-vesicles incubated in the presence of external Na+ was higher than that by P-vesicles incubated in choline+ instead of Na+. The vesicles exhibited Na+-dependent I- uptake. When P-vesicles were internally loaded with I- prior to incubation in Na+, a further increase in Na+-dependent I- uptake was observed, although the concentration of internal I- was very much higher than that outside. In the absence of external Na+, I- uptake by P-vesicles preloaded with I- was comparable to baseline uptake. 2) Na+-dependent I- uptake by P-vesicles not loaded with I- and enhanced Na+-dependent I- uptake by P-vesicles preloaded with I- were both inhibited by either of SCN- and ClO4- added outside the vesicles. 3) When P-vesicles were loaded with SCN- instead of I- and incubated in Na+, I- uptake by these vesicles was also higher than baseline Na+-dependent I- uptake. However, a ClO4- load did not result in an increase in I- uptake. These results indicate that Na+-dependent I- transport including Na+-dependent I- counterflow is specifically mediated by the thyroid I- carrier. SCN- - I- counterflow in addition to I- - I- counterflow occurs dependently on Na+, but ClO4- - I- counterflow does not. 相似文献
10.
Immunocytochemical localization of thrombomodulin in the aqueous humor passage of the rat eye 总被引:1,自引:1,他引:0
T. Daimon Mutsuyoshi Kazama Yukari Miyajima Masahiko Nakano 《Histochemistry and cell biology》1997,108(2):121-131
This report describes the distribution and localization of thrombomodulin (TM) in the rat eye by light and electron microscopic
immunocytochemistry. In addition to the endothelium of the entire vasculature, TM was found on the non-vascular structures
lining the cavities of the posterior and anterior chambers and the limbus. TM was localized on the basal, lateral, and apical
plasma membranes of the inner and outer ciliary epithelium, and the posterior iris epithelium in which there was no polarized
expression of TM. In the anterior chamber, TM was localized on the luminal surface of the corneal endothelium, but was negative
on the anterior border layer of the iris, which is composed of a discontinuous layer of fibroblasts and collagen fibers. Thus,
TM was present at sites of cell-to-cell contact. TM was also present on the endothelia of the trabecular meshwork and the
Schlemm’s canal in the limbus. TM was localized not only on the luminal plasma membrane, but also on the cytoplasmic giant
vacuoles in the endothelial cells of the Schlemm’s canal. These findings extend the importance of anticoagulant mechanisms
to the systems of secretion, circulation, and drainage of the aqueous humor.
Accepted: 18 March 1997 相似文献