全文获取类型
收费全文 | 8528篇 |
免费 | 884篇 |
国内免费 | 8篇 |
出版年
2023年 | 47篇 |
2022年 | 75篇 |
2021年 | 261篇 |
2020年 | 163篇 |
2019年 | 196篇 |
2018年 | 193篇 |
2017年 | 165篇 |
2016年 | 230篇 |
2015年 | 393篇 |
2014年 | 424篇 |
2013年 | 509篇 |
2012年 | 607篇 |
2011年 | 593篇 |
2010年 | 369篇 |
2009年 | 326篇 |
2008年 | 445篇 |
2007年 | 448篇 |
2006年 | 375篇 |
2005年 | 391篇 |
2004年 | 356篇 |
2003年 | 305篇 |
2002年 | 307篇 |
2001年 | 102篇 |
2000年 | 77篇 |
1999年 | 87篇 |
1998年 | 97篇 |
1997年 | 50篇 |
1996年 | 46篇 |
1995年 | 47篇 |
1994年 | 42篇 |
1993年 | 50篇 |
1992年 | 78篇 |
1991年 | 57篇 |
1990年 | 65篇 |
1989年 | 58篇 |
1988年 | 47篇 |
1987年 | 51篇 |
1986年 | 50篇 |
1985年 | 44篇 |
1984年 | 50篇 |
1983年 | 40篇 |
1982年 | 56篇 |
1981年 | 55篇 |
1980年 | 54篇 |
1978年 | 54篇 |
1977年 | 39篇 |
1975年 | 44篇 |
1974年 | 49篇 |
1973年 | 50篇 |
1970年 | 39篇 |
排序方式: 共有9420条查询结果,搜索用时 15 毫秒
91.
Therapy of Staphylococcal Infections in Monkeys. IV. Further Comparison of Triacetyloleandomycin and Erythromycins 总被引:4,自引:2,他引:2 下载免费PDF全文
Intravenous inoculation of a penicillin-resistant, phage type 80/81 staphylococcus caused lethal infection in 8 of 15 untreated monkeys. Daily intragastric administration of 50 mg/kg of triacetyloleandomycin, erythromycin estolate, and erythromycin ethylsuccinate was followed by mortalities of 0 of 16, 3 of 16, and 3 of 10, respectively. At dose levels of 25 and 12.5 mg/kg, none of 7 and 4 of 7 receiving triacetyloleandomycin and erythromycin estolate, respectively, died, as compared to 3 of 4 deaths in controls. In vitro sensitivity data and serum antibacterial levels would suggest that triacetyloleandomycin would be the least effective therapeutically. However, this prediction was not fulfilled in these studies of experimental infections in monkeys wherein triacetyloleandomycin was a very effective antimicrobial agent. 相似文献
92.
93.
94.
E M Perkins 《American journal of physical anthropology》1968,29(3):349-364
The pigmy marmoset — Callithrix (= Cebuella) pygmaea Spix — is the second detailed study of the members of the family Callithricidae. It is closely allied to the red-mantled tamarin — Saguinus (=Tamarinus) fuscicollis illigeri Spix — and shares some of its characteristics with both Prosimii and Anthropoidea. The epidermis and dermis contain moderate numbers of concurrent, melanotic melanocytes. The dermis is rich in elastin. Hair follicles grow in groups of three or four over the general body surface, and one apocrine gland is associated with each grouping. Arrectores pilorum muscles are well developed. On the ventral ulnar wrist are sinus hairs associated with apocrine glands. Most hair follicles have nerve end-organs around them that are reactive for acetylcholinesterase and alkaline phosphatase. There is a large aggregation of sebaceous glands in the suprapubic region. The large sebaceous glands in the eyelid, face, and external genitalia are surrounded by cholinesterasereactive nerves. Apocrine glands are found over most of the hairy skin except the brow, scalp and back; a large grouping of them is present in the sternal region. Only the secretory coils of apocrine glands in the external genitalia are invested with butyrylcholinesterase-rich nerves. Eccrine glands are confined to the volar surfaces of the pes and manus. They have dark cells with abundant glycogen and clear cells with neither glycogen nor PAS-reactive material. The nerves around the eccrine secretory coil are reactive only for acetylcholinesterase. 相似文献
95.
96.
97.
The skin of the golden spider monkey (Ateles geoffroyi) has many histological and histochemical similarities to that of the woolly monkey (Lagothrix lagotricha) and howler monkey (Alouatta caraya); however, this monkey possesses certain peculiar properties such as large sebaceous glands, a combined distributional pattern of eccrine and apocrine sweat glands, and abundant alkaline phosphatase in the sebaceous glands, apocrine and eccrine sweat glands. In brief, the anatomical and histochemical properties of the skin of this animal are more similar to those of the howler monkey than to the woolly monkey. In addition, the skin of these three Ceboids falls phylogenetically between that of the Cercopithecoidea and Pithecoidea. 相似文献
98.
ALPHA-HYDROXYGLUTARIC ACID SYNTHETASE 总被引:5,自引:3,他引:2
99.
A COMPARISON OF THE CHANGES IN FINE STRUCTURE OF L CELLS DURING SINGLE CYCLES OF VIRAL MULTIPLICATION, FOLLOWING THEIR INFECTION WITH THE VIRUSES OF MENGO AND ENCEPHALOMYOCARDITIS 总被引:17,自引:4,他引:13 下载免费PDF全文
The virus of encephalomyocarditis (EMC), examined by the negative-contrast method, is indistinguishable from the serologically related Mengovirus. The particles are 270 to 280 A in diameter. The surface of EMC is composed of an undetermined number of subunits. Frequent sampling of infected cells was carried out throughout one-step cycles of viral multiplication to observe cytopathic changes occurring in L cells infected by these two related RNA viruses. EMC and Mengovirus, which multiply at equal rates, in most respects elicit similar alterations in cell fine structure. Rearrangement and changes in nuclear material accompanied by formation of small vesicles in the centrosphere region commence at 4 to 6 hours after infection. Thereafter a progressive degeneration of the nucleus and vesiculation of the cytoplasm are observed up to 18 to 20 hours. Increased numbers of small dense granules, indistinguishable from ribonucleoprotein particles, appear in the cytoplasm between 8 and 14 hours after infection. L cells infected with Mengovirus become permeable to Erythrocin more slowly than those infected with EMC. Only in the case of Mengovirus infection are large aggregates of dense material first observed in the cytoplasm at 8 hours, followed by the appearance of crystals probably composed of Mengovirus particles, at 12 hours. Differences in the rates of cell permeability after infection with EMC and Mengovirus are discussed in relation to formation of virus crystals and plaque-type mutants. 相似文献
100.
Crossing over frequency was determined for five marked regions covering most of a chromosome arm. The results of a 12th backcross were compared with previously published results from the noninbred f1. Exchange frequency increased significantly following inbreeding. Chiasma interference remained positieve, but was somewhat less intense in b12.Supported in part by Public Health Service Research Grants AI 01462 and GM 1882-01, by a National Science Foundation Faculty Fellowship to H. R. C., and by Public Health Service Research Career Award K6-GM-4899 to D. D. P.Technical Paper No. 2054, Oregon Agricultural Experiment Station, Corvallis. 相似文献