全文获取类型
收费全文 | 756775篇 |
免费 | 86440篇 |
国内免费 | 363篇 |
出版年
2016年 | 8385篇 |
2015年 | 11543篇 |
2014年 | 13511篇 |
2013年 | 20006篇 |
2012年 | 21849篇 |
2011年 | 22480篇 |
2010年 | 15270篇 |
2009年 | 14081篇 |
2008年 | 19970篇 |
2007年 | 20878篇 |
2006年 | 19551篇 |
2005年 | 18795篇 |
2004年 | 18537篇 |
2003年 | 18189篇 |
2002年 | 17702篇 |
2001年 | 32554篇 |
2000年 | 32790篇 |
1999年 | 26047篇 |
1998年 | 9163篇 |
1997年 | 9903篇 |
1996年 | 9284篇 |
1995年 | 9043篇 |
1994年 | 8803篇 |
1993年 | 8997篇 |
1992年 | 22689篇 |
1991年 | 22446篇 |
1990年 | 21897篇 |
1989年 | 21610篇 |
1988年 | 20041篇 |
1987年 | 19131篇 |
1986年 | 17841篇 |
1985年 | 18292篇 |
1984年 | 15254篇 |
1983年 | 13167篇 |
1982年 | 10188篇 |
1981年 | 9094篇 |
1980年 | 8657篇 |
1979年 | 14597篇 |
1978年 | 11458篇 |
1977年 | 10665篇 |
1976年 | 10163篇 |
1975年 | 11064篇 |
1974年 | 11803篇 |
1973年 | 11655篇 |
1972年 | 10722篇 |
1971年 | 9755篇 |
1970年 | 8328篇 |
1969年 | 8140篇 |
1968年 | 7461篇 |
1967年 | 6549篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
992.
993.
E. V. Smirnova L. A. Gordova N. M. Timofeeva G. G. Shcherbakov 《Journal of Evolutionary Biochemistry and Physiology》2005,41(1):47-53
Distribution of activities of disaccharidases (saccharase, maltase), amino- and dipeptidases, dipeptidyl peptidase IV (DPP) and alkaline phosphatase along the small intestine and of these hydrolases in liver and kidney, as well as distribution of the digestive enzyme activities between the membrane and cytosol fractions of enterocytes is characterized in adult 6-month old pigs. It has been shown that maximum of the studied enzyme activities, except for DPP, takes place in ileum. A higher level of the activities of the soluble form of saccharase, maltase, and aminopeptidase M and a less significant level of the activity of the glycyl-L-leucine dipeptidase soluble form in jejunum and ileum is found than those in rats and monkeys. The obtained data demonstrate the existence of the complex enzyme system in small intestine, liver, and kidney that participate in realization of nutritive and trophic-barrier functions.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 39–43.Original Russian Text Copyright © 2005 by Smirnova, Gordova, Timofeeva, Shcherbakov. 相似文献
994.
995.
The incidence of the parasitic disease trichomoniasis and its treatment in reintroduced and wild Pink Pigeons Columba mayeri 总被引:1,自引:0,他引:1
The recovery programme for the endangered Pink Pigeon Columba mayeri Prévost, 1843 of Mauritius has involved intensive management to promote rapid population growth. As the Pink Pigeon population has increased in size and distribution, disease problems have emerged that have affected wild and reintroduced birds. Trichomoniasis first appeared in the remnant wild population in 1992, and became established in a reintroduced subpopulation on the offshore island of Ile aux Aigrettes. We aimed to control the disease by treating individuals and, on Ile aux Aigrettes, by routinely treating the population with medicated drinking water. On Ile aux Aigrettes, 49% of squabs were clinically diseased and only 27% of all squabs survived without treatment. Treatment of squabs that were not clinically diseased improved survival from 36 to 82%, suggesting that subclinical infections also affected survival. Subclinical infections were demonstrated by microscopy in 22% of Pink Pigeons and 17% of exotic doves on Ile aux Aigrettes. Clinical disease was observed in 4.5% of adults and 3.1% of juveniles, but more juveniles than adults died from the disease. It is likely that Trichomoniasis and other diseases will continue to affect the Pink Pigeon's recovery and the species may require long-term management to counteract the effects of disease and other limiting factors. 相似文献
996.
The synthesis and characterization of rare-earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) thiocyanate adducts with tripiperidinophosphine oxide (tpppO) with general formula (RE)(SCN)3(tpppO)3 are reported. Conductance measurements in acetonitrile indicate the non-electrolytic nature of the complexes. Infrared absorption spectra evidence that the SCN− ion coordinates through the nitrogen atom (isothiocyanate form) and that tpppO coordinates through the phosphoryl oxygen. X-ray powder patterns suggest the existence of three different crystal forms: (1) La; (2) an isomorphous series including Ce, Nd and Pr; and (3) another isomorphous series, including Sm, Gd, Eu, Ho, Er, Tb, Lu and Y. The visible spectra of the Nd adduct and the calculated parameters β = 0.98, b1/2 = 0.072 and δ = 1.06 indicate that the metal-ligand bonds are essentially electrostactic. The emission spectra of the Eu compound showed 5D0 → 7FJ bands (J = 0, 1, 2), suggesting a C3v symmetry for the coordination polyhedron. The lifetime of the 5D0 state is 1.28 ms. The emission spectra of the Tb complex presented 5D4 → 7FJ bands (J = 4, 5, 6) and the Dy complex showed the 4F9/2 → 6H13/2 band. The structure of the Pr complex showed that the coordination polyhedron is a trigonal antiprism, with the isothiocyanate anions in one base and three tpppO ligands in the other. Thermal analyses (TG-DTG) were carried out for the Ce, Nd and Gd adducts. Mass losses start between 250 and 334 °C. The final residues at 1300 °C are the corresponding phosphates. 相似文献
997.
Sotiris K. Hadjikakou Constantinos D. Antoniadis Maciej Kubicki Spyros Karkabounas 《Inorganica chimica acta》2005,358(10):2861-2866
A novel water stable, antimony(III) complex with the heterocyclic thioamide; 2-mercapto-pyrimidine (pmtH), of formula [Sb(pmt)3] · 0.5(CH3OH), has been synthesized and characterized by elemental analysis, 1H, 13C NMR and FT-IR spectroscopic techniques. Crystal structure of the molecule has been determined by X-ray diffraction at ambient conditions. The compound [C12H9N6S3Sb · 0.5(CH3OH)] is monoclinic, space group P21/c, a = 7.0646(7), b = 16.3767(14), c = 14.7265(13) Å, β = 92.016(7)°, Z = 4. In complex, three sulfur and three nitrogen atoms from thione ligands form a distorted pendagonal pyramidal geometry around antimony(III). The toxicity of the compound against tumor pleiomorphic cells, which has been isolated from a leiomyosarcoma tumor in the Wistar rat (chemical carcinogenesis using BaP) was studied in vitro. The results show that the compound did not destroy or prevent multiplication in vitro in leiomyosarcoma cells in low doses. The influence of the compound in the platelet aggregation, which correlates with the above tumor cells enhanced metastatic potential, has also been studied. The anti-metastatic capability study shows that the compound inhibited cancer cell induced aggregation up to the value of 10% in all mM concentrations tested. 相似文献
998.
The biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) transmits pathogens to both livestock and wildlife. Biting midge surveillance relies heavily on light traps for collection; however, little is known about the light spectra preferences of C. sonorensis midges. A light assay arena was constructed and light‐emitting diodes (LEDs) of various light spectra were used as light sources to evaluate midge photoattraction. A comparison of responses to light spectra indicated the highest proportions of C. sonorensis were attracted to ultraviolet (UV) light and that midges differentiated 10‐nm differences in wavelength. Stronger intensities of UV light resulted in greater attraction. Midges exhibited both sugar‐seeking and escape behaviours under different conditions of sugar supplementation before and during the experiment. These behaviours occurred with lights of 355 nm and 365 nm in wavelength. Based on the results of this study, the attraction of C. sonorensis to light traps can be improved through the use of bright LEDs at 355 nm or 365 nm. 相似文献
999.