全文获取类型
收费全文 | 631篇 |
免费 | 44篇 |
专业分类
675篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 32篇 |
2012年 | 37篇 |
2011年 | 44篇 |
2010年 | 38篇 |
2009年 | 19篇 |
2008年 | 35篇 |
2007年 | 30篇 |
2006年 | 39篇 |
2005年 | 38篇 |
2004年 | 29篇 |
2003年 | 31篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 7篇 |
1968年 | 3篇 |
1967年 | 4篇 |
1966年 | 6篇 |
1965年 | 3篇 |
1948年 | 2篇 |
1914年 | 2篇 |
1911年 | 8篇 |
排序方式: 共有675条查询结果,搜索用时 0 毫秒
11.
The amount of calliphorin, its biosynthesis, and the levels of translatable calliphorin-mRNA have been determined during the postembryonic development of Calliphora vicina R.-D. The amount of calliphorin increases in early third-instar larvae, reaching maximal levels in 6-day-old animals. It continuously decreases during late larval and pupal development to approximately one-half of the maximal levels and abruptly sinks during eclosion. The biosynthesis of calliphorin takes place only in 3- to 5-day-old larvae. Poly(A)+-RNA has been translated into proteins in a wheat germ cell-free system. Calliphorin-mRNA can be detected in 3- to 7-day-old larvae; maximal concentrations are observed in 4- and 5-day-old animals. No calliphorin-mRNA can be detected in prepupae, pupae, or imagos. The biosynthesis of calliphorin in blowfly larvae stops before a decrease of translatable calliphorin-mRNA is observed. This finding raises the question of the mechanism of in vivo inactivation of this specific mRNA. 相似文献
12.
Muramyl dipeptide (MDP), a synthetic adjuvant, increased the primary response of CBA mice to sheep red blood cells (SRBC). In reconstituted irradiated recipients, cooperation between T and B lymphocytes was required for the expression of adjuvant activity and MDP increased the efficiency of SRBC-educated T cells. The role of T-derived lymphocytes in mediating the MDP adjuvant activity was also demonstrated in irradiated mice and in mice reconstituted with various splenic cellular types of donors which had received SRBC and MDP 24 hr earlier. In our experiments, the macrophage did not seem to be involved, since MDP did not increase the phagocytic capacity of peritoneal exudate cells and MDP- and SRBC-pretreated macrophages had no increased ability to induce an anti-SRBC immune response. These results demonstrate the importance of T lymphocytes as mediators of the adjuvant activity of MDP. 相似文献
13.
W.James Nelson Constantin E. Vorgias Peter Traub 《Biochemical and biophysical research communications》1982,106(4):1141-1147
A new method is described for the purification of the intermediate filament protein vimentin from Ehrlich ascites tumor cells using single-stranded DNA-cellulose affinity chromatography. The procedure is rapid and allows the large scale isolation of the protein. Partial characterization of vimentin shows that it has a molecular weight of 58000 and an apparent pI of 5.3. It can be degraded by the vimentin-specific, Ca2+-activated proteinase which results in the production of a characteristic set of degradation products. The vimentin also cross-reacts with the intermediate filament protein monoclonal antibody, α-IFA. 相似文献
14.
Constantin C. Chipev Miglena I. Angelova 《International journal of biological macromolecules》1983,5(4):252-253
The denaturation of short (145 base pairs) and long (about 8000 base pairs) DNA moelucules has been studied by adiabitic differential microcalorimetry in solutions with different NaCl content. It is found that the enthalpy of denaturation of short DNA is more sensitive to changes in Tm than that of long DNA. A comparison with other data is also given. 相似文献
15.
D Stavri D Niculescu H Stavri E Tip?rescu S Constantin I Fuiorea A Basacopol 《Archives roumaines de pathologie expérimentales et de microbiologie》1990,49(4):323-329
206 sera collected from different groups of subjects were analyzed by immunoenzymatic methods regarding the content of Mycobacterium tuberculosis specific antibodies and mycobacterial antigens. The results underlined that two assays offered improved serologic diagnosis of tuberculosis over a single antibody test. BCG vaccination interferes with serologic tests for tuberculosis when polyspecific antibodies or mixture of common and specific antigens are used as immunologic reagents. A mycobacterial antigens circadian variation in correlation with vesperal fever in tuberculous patients was not revealed. The mycobacterial antigens seem to become undetectable, in sera, after 6 months of efficient treatment. 相似文献
16.
17.
The chlorophyll repair potential of mature Cucumis chloroplasts incubated in a simple Tris-HCI/sucrose medium is described. The chloroplasts were isolated from green, fully expanded Cucumis cotyledons which were capable of chlorophyll repair. This was evidenced by a functional chlorophyll biosynthetic pathway in the mature tissue. The biosynthesis of protochlorophyllide from exogenous δ-aminolevulinic acid was used as a marker for the operation of the chlorophyll biosynthetic chain between δ-aminolevulinic acid and protochlorophyllide. The conversion of exogenous protochlorophyllide into chlorophyll a was used as a marker for the operation of the chlorophyll pathway beyond protochlorophyllide. It appeared from these studies that contrary to published reports, unfortified fully developed Cucumis chloroplasts incubated in Tris-HCl/sucrose without the addition of cofactors exhibited a partial and limited chlorophyll repair capability. Their net tetrapyrrole biosynthetic competence from δ-aminolevulinic acid was confined to the accumulation of coproporphyrin. No net tetrapyrrole biosynthesis beyond coproporphyrin was observed. However, the plastids were capable of incorporating small amounts of δ-amino-[4-14C]levulinic acid into [14C] protochlorophyllide but were incapable of converting exogenous protochlorophyllide into chlorophyll. After prolonged incubation of the unfortified chloroplasts in the dark, a fluorescent protochlorophyllide-like compound accumulated. This compound [Cp (E430-F631)] exhibited a soret excitation maximum at 430 nm (E430) and a fluorescence emission maximum at 631 nm (F631) in methanol/acetone (4 : 1, v/v). Cp (E430-F631) was shown to be neither protochlorophyllide nor zinc-protochlorophyllide but an enzymatic degradation product of chlorophyll. The exact chemical identity of this compound has not yet been determined. 相似文献
18.
Constantin Munteanu Mariana Rotariu Marius-Alexandru Turnea Aurelian Anghelescu Irina Albadi Gabriela Dogaru Sînziana Calina Siliteanu Elena Valentina Ionescu Florentina Carmen Firan Anca Mirela Ionescu Carmen Oprea Gelu Onose 《Current issues in molecular biology》2022,44(8):3378
Diabetes mellitus (DM) is a frequent medical problem, affecting more than 4% of the population in most countries. In the context of diabetes, the vascular endothelium can play a crucial pathophysiological role. If a healthy endothelium—which is a dynamic endocrine organ with autocrine and paracrine activity—regulates vascular tone and permeability and assures a proper balance between coagulation and fibrinolysis, and vasodilation and vasoconstriction, then, in contrast, a dysfunctional endothelium has received increasing attention as a potential contributor to the pathogenesis of vascular disease in diabetes. Hyperglycemia is indicated to be the major causative factor in the development of endothelial dysfunction. Furthermore, many shreds of evidence suggest that the progression of insulin resistance in type 2 diabetes is parallel to the advancement of endothelial dysfunction in atherosclerosis. To present the state-of-the-art data regarding endothelial dysfunction in diabetic micro- and macroangiopathy, we constructed this literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We interrogated five medical databases: Elsevier, PubMed, PMC, PEDro, and ISI Web of Science. 相似文献
19.
Constantin Regel 《Plant Systematics and Evolution》1948,95(1):102-123
Ohne ZusammenfassungDer folgende Artikel hätte in den Beiheften zum Botanischen Centralblatt erscheinen sollen, war auch schon gesetzt worden, sein Erscheinen wurde dann aber durch die Kriegsereignisse verhindert. 相似文献
20.