全文获取类型
收费全文 | 432596篇 |
免费 | 48752篇 |
国内免费 | 155篇 |
专业分类
481503篇 |
出版年
2018年 | 3986篇 |
2016年 | 5391篇 |
2015年 | 7096篇 |
2014年 | 8374篇 |
2013年 | 11548篇 |
2012年 | 13142篇 |
2011年 | 13584篇 |
2010年 | 9327篇 |
2009年 | 8618篇 |
2008年 | 12440篇 |
2007年 | 12907篇 |
2006年 | 12135篇 |
2005年 | 11565篇 |
2004年 | 11622篇 |
2003年 | 10918篇 |
2002年 | 10723篇 |
2001年 | 17597篇 |
2000年 | 17588篇 |
1999年 | 14061篇 |
1998年 | 5135篇 |
1997年 | 5365篇 |
1996年 | 4999篇 |
1995年 | 4706篇 |
1994年 | 4567篇 |
1993年 | 4623篇 |
1992年 | 11721篇 |
1991年 | 11679篇 |
1990年 | 11449篇 |
1989年 | 11022篇 |
1988年 | 10606篇 |
1987年 | 10198篇 |
1986年 | 9480篇 |
1985年 | 9348篇 |
1984年 | 7847篇 |
1983年 | 6784篇 |
1982年 | 5252篇 |
1981年 | 4709篇 |
1980年 | 4550篇 |
1979年 | 7516篇 |
1978年 | 5952篇 |
1977年 | 5477篇 |
1976年 | 5279篇 |
1975年 | 5665篇 |
1974年 | 6384篇 |
1973年 | 6255篇 |
1972年 | 5837篇 |
1971年 | 5295篇 |
1970年 | 4675篇 |
1969年 | 4629篇 |
1968年 | 4467篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
Résumé Les auteurs ont étudié 750 bactéries lactiques isolées de vins, en utilisant les tests et le système de classification de Rogosa et Sharpe. Parmi ce grand nombre de souches vingt-trois appartiennent au groupe des bacilles homolactiques et font l'objet du présent travail. Elles se répartissent de la façon suivante: 9 souches de Lactobacillus plantarum, 2 souches de Lactobacillus casei var. casei, 4 souches de Lactobacillus casei var. alactosus et 8 souches de Streptobacterium non classées, différentes des espèces précédentes.Les auteurs discutent la valcur de cette classification, lorsqu'on se place au point de vue technologique. Ils montrent qu'elle s'applique mal aux bactéries lactiques isolées de milieux fermentés acides comme le vin. Elle a peu d'intérêt pratique, car elle ne permet pas de repérer une souche et de prévoir par sa position systématique les constituants du vin que cette souche est susceptible de métaboliser.
A study of some homofermentative lactic acid bacteria isolated from wines
Summary The authors have studied 750 strains of lactic acid bacteria isolated from wines. In this study the test and classification of Rogosa and Sharpe were used. Of the strains mentioned 23 belonged to the homolactie bacteria, including 9 strains of Lactobacillus plantarum, 2 strains of Lactobacillus casei var. casei, 4 strains of Lactobacillus casei var. alactosus, and 8 strains of a non-identified Streptobacterium species.The authors discuss the value of the classification mentioned from the point of view of wine technology. They conclude that it cannot be applied in the case of lactic acid bacteria isolated from acid fermentation products such as wine. It is only of little practical interest because it does not render the identification of the strains possible, nor does it permit a prediction of the wine constituents which the strains concerned are able to metabolize.相似文献
944.
The urea washout (UWT) modification of the intravenous pyelogram was used to study 146 hypertensive patients in order to detect the presence of significant renovascular abnormalities. A positive result was obtained in 55 patients and direct confirmation of main renal artery stenoses by selective renal arteriography was obtained in 26. Bilateral abnormalities were confirmed in seven of the 26 patients. No false-negative results were encountered. The usefulness of this test as a comprehensive screening test is outlined. It demonstrated a high degree of accuracy in the diagnosis of significant unilateral or bilateral main renal artery stenosis in addition to the detection of diffuse intrarenal arteriolar disease. It was of value in the postoperative assessment of operative repair of main renal artery defects. The urea washout test embodies both an anatomical and a physiological approach in the roentgen diagnosis of curable renovascular hypertension. The altered physiology resulting from significant main renal artery stenosis makes possible the use of the urea washout intravenous pyelogram. The value of other forms of intravenous pyelography is described. 相似文献
945.
946.
Marshall E. Landay Robert W. Wheat Norman F. Conant Edwin P. Lowe 《Mycopathologia》1967,33(3-4):225-232
Summary The results of this study indicated that antigens prepared from the three morphological phases ofCoccidioides immitis differed in their complement fixing activity with anti-Histoplasma capsulatum pooled serum. Spherule antigens were serologically less active in tests with the anti-H. capsulatum pooled serum than antigens prepared from arthrospores and from mycelium.Antigenic determinants which are common toC. immitis andH. capsulatum appeared to be located on the intact arthrospore cellular surface but not on the surface of spherule cells.Part of a dissertation submitted to the Graduate School of Duke University in partial fulfillment of requirements for the Ph. D. degree.This work was supported by contract with the Department of the Army, Fort Detrick, Frederick, Maryland.In conducting the research reported herein, the investigators adhered to Guide for Laboratory Animal Facilities and Care established by the Committee on the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, NAS-NRC. 相似文献
947.
948.
The fermentation of uniformly labeled glucose-C14, glucose-1-C14, -2-C14, and -6-C14, xylose-1-C14, cellulose-1-C14, -2-C14, and -6-C14, and lactate-2-C14 by rumen fluids from cows fed all-hay, hay and concentrate (50:50), and all-concentrate diets was investigated. The results obtained suggested that the Embden-Meyerhof glycolytic pathway is the major pathway of hexose utilization, that the major pathway of xylose fermentation involves hexose synthesis, and that the contributions of the nonrandomizing (acrylate) pathway of propionate formation during glucose, xylose, and cellulose fermentations are 4.5, 8.0, and 10.5%, and 24.6, 25.8, and 17.2%, respectively, by rumen fluids from the cows fed all-hay and all-concentrate rations. 相似文献
949.
Curtis E. Meyer 《Applied microbiology》1966,14(4):511-512
The isolation and characterization of antibiotic U-21,963 are discussed. This compound is a highly unsaturated monobasic acid with the molecular formula C(9)H(7)NO(3). The molecular weight is 177. It is dextrorotatory, [alpha](D) = +138 degrees , and has a pK(a) of 5.1. The ultraviolet absorption spectrum, which showed a maximum at 223 mmu (epsilon = 15,115), indicates unsaturation alpha-beta to the carboxyl group, and the infrared spectrum suggests the presence of an acetylenic group. Explosive decomposition of U-21,963 at 97 C conforms with the latter. U-21,963 is relatively insoluble in water, but readily soluble in ethyl alcohol, acetone, and halogenated hydrocarbons. 相似文献
950.