全文获取类型
收费全文 | 449607篇 |
免费 | 28287篇 |
国内免费 | 989篇 |
专业分类
478883篇 |
出版年
2018年 | 15473篇 |
2017年 | 14203篇 |
2016年 | 12225篇 |
2015年 | 5522篇 |
2014年 | 6870篇 |
2013年 | 9744篇 |
2012年 | 15091篇 |
2011年 | 24229篇 |
2010年 | 19783篇 |
2009年 | 15130篇 |
2008年 | 19978篇 |
2007年 | 21950篇 |
2006年 | 10823篇 |
2005年 | 10340篇 |
2004年 | 11014篇 |
2003年 | 10709篇 |
2002年 | 10447篇 |
2001年 | 16066篇 |
2000年 | 15856篇 |
1999年 | 12042篇 |
1998年 | 3824篇 |
1997年 | 3795篇 |
1996年 | 3434篇 |
1995年 | 3164篇 |
1992年 | 9551篇 |
1991年 | 9763篇 |
1990年 | 9494篇 |
1989年 | 9498篇 |
1988年 | 8770篇 |
1987年 | 8256篇 |
1986年 | 7530篇 |
1985年 | 7852篇 |
1984年 | 6340篇 |
1983年 | 5334篇 |
1982年 | 3616篇 |
1981年 | 3180篇 |
1980年 | 3133篇 |
1979年 | 5962篇 |
1978年 | 4646篇 |
1977年 | 4230篇 |
1976年 | 3993篇 |
1975年 | 4808篇 |
1974年 | 5313篇 |
1973年 | 5269篇 |
1972年 | 5026篇 |
1971年 | 4745篇 |
1970年 | 3901篇 |
1969年 | 3795篇 |
1968年 | 3554篇 |
1967年 | 3201篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
There are reported the results of certain measurements made on 158 human cadavers of both sexes. A series of main parameters are given, such as the distance between the superior mesenteric vein and on the one hand its confluence with other vessels and on the other hand the pancreas and the horizontal part of the duodenum: the distance between the superior mesenteric vein together with the portal vein, and the inferior caval vein; the diameters of the portal trunk and the confluence angle between the roots of the portal vein. The results reflect the possibility to perform a troncular portocaval anastomosis in at least 90 per cent of the cases. The authors' attention was, however, directed towards the anatomy of the superior mesenteric vein, as this vessel is preferred by some surgeons in the achievement of the portocaval anastomosis. 相似文献
952.
953.
The orientation of washed Escherichia coli bacteria in suspension induced by applied a.c. electric fields has been monitored by observing the accompanying changes in the intensity of light scattered by the suspension. The data enable the anisotropy of electrical polarisability deltaalpha to be determined. Changes in deltaalpha due to the addition of various antibiotics to the suspension have been measured as a function of both the antibiotic concentration and the temperature of the suspension. The results are taken to indicate that there is an accumulation of the antibiotic molecules at the bacterial surface. 相似文献
954.
T I Mercado 《Experimental parasitology》1973,34(1):142-147
In recent attempts to isolate the factor causing paralysis in rats infected with a mousepassed KBG 173 strain of Plasmodium berghei Splenectomy was employed. The effects of Splenectomy on the paralyzing syndrome are discussed in the present report. Paralysis was inhibited in rats splenectomized prior to inoculation. Serial bloodpassaging of the strain in the splenectomized host however, apparently enhanced its virulence. Spleen-intact rats used as controls exhibited a marked increase in incidence of paralysis. Rats splenectomized a day before paralysis became evident were paralyzed significantly more frequently than those splenectomized a day earlier, indicating the apparent requirement of an incubation period for the expression of the paralytic effect. The enhanced virulence did not appear to be related to the level of parasitemia of the splenectomized rats used as donors. The spleen appears to provide the optimal conditions required for the elaboration of the paralyzing factor. 相似文献
955.
In the frog intestine, both in vitro and in vivo, experiments were carried out in order to increase knowledge of the mechanism of sugar exit across the basolateral membrane of the enterocyte. The frog intestine was chosen because it lacks crypt cells and, consequently, any external fluid circuit mechanism during sugar transport can be avoided. Therefore, the sugar concentration in the absorbate collected on the serosal side is likely to be similar to that present underneath the basolateral membrane of the enterocyte. Under this condition, cell and absorbate sugar concentrations are similar; yet there is a concomitant net transintestinal sugar transport. Moreover, in in vivo experiments a net transintestinal sugar transport takes place even against a concentration difference. These results suggest that sugar exit across the basolateral membrane is not simply due to a chemically facilitated diffusion. 相似文献
956.
A A Sumarokov L A Nefedova I Iu Iaroshevskaia L V Salmin N A Ozeretskovski? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1977,(5):109-114
Prophylactic activity and side action of antiinfluenza lactoglobulin were studied under conditions of controlled epidemiological trial in 6361 persons during the epidemiological rise of influenza incidence. The data obtained pointed to the absence of any protective effect of antiinfluenza lactoglobulin. Marked allergenic properties of lactoglobulin and development of sensitization in the persons under observation were found during the study of the side-effect of the preparation. Thus, the absence of prophylactic efficacy and the sensitizing action of antiinfluenza lactoglobulin pointed to the inexpediency of its use for prophylactic and therapeutic purpose. 相似文献
957.
958.
Dolichyl phosphates of different chain length (C35, C55 , C75 , Dol-mixture of C90 , 95, 100, 105 and C110 ) were tested as lipid acceptors in transglycosylation reactions. In the absence of exogenously added dolichyl phosphates there were no differences in the rate of synthesis in liver of dolichyl phosphate mannose, dolichyl phosphate glucose and dolichyl pyrophosphate N-acetylglucosamine between normal and ethionine-treated animals. Addition of exogenous dolichyl phosphates of different chain length stimulated the synthesis of dolichyl phosphate mannose and dolichyl pyrophosphate N-acetyl-glucosamine 2 to 4 times depending on the chain length of dolichols , both in normal and ethionine-treated animals. In liver of ethionine-treated rats the formation of dolichyl phosphate glucose was not stimulated. Following ethionine treatment the concentration of free and esterified with fatty acids dolichols was increased. 相似文献
959.
960.