全文获取类型
收费全文 | 13269篇 |
免费 | 1797篇 |
国内免费 | 4篇 |
专业分类
15070篇 |
出版年
2022年 | 143篇 |
2021年 | 283篇 |
2020年 | 168篇 |
2019年 | 185篇 |
2018年 | 229篇 |
2017年 | 214篇 |
2016年 | 313篇 |
2015年 | 503篇 |
2014年 | 556篇 |
2013年 | 598篇 |
2012年 | 868篇 |
2011年 | 809篇 |
2010年 | 452篇 |
2009年 | 434篇 |
2008年 | 620篇 |
2007年 | 641篇 |
2006年 | 538篇 |
2005年 | 514篇 |
2004年 | 458篇 |
2003年 | 422篇 |
2002年 | 370篇 |
2001年 | 313篇 |
2000年 | 300篇 |
1999年 | 243篇 |
1998年 | 157篇 |
1997年 | 134篇 |
1996年 | 117篇 |
1995年 | 137篇 |
1994年 | 140篇 |
1993年 | 128篇 |
1992年 | 229篇 |
1991年 | 195篇 |
1990年 | 207篇 |
1989年 | 236篇 |
1988年 | 338篇 |
1987年 | 203篇 |
1986年 | 153篇 |
1985年 | 168篇 |
1984年 | 140篇 |
1983年 | 130篇 |
1982年 | 108篇 |
1981年 | 103篇 |
1980年 | 110篇 |
1979年 | 126篇 |
1978年 | 114篇 |
1977年 | 127篇 |
1976年 | 97篇 |
1975年 | 93篇 |
1974年 | 109篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
The incidence and the clinical course of patients suffering from sickle-cell syndrome (Hb SS; Hb SC; Hb S thal) in England and Wales are not known. In 1979 an ad hoc committee was formed to investigate these problems. Initially, a questionnaire was sent to 227 haematologists in England and Wales to determine the number of cases in these countries. The replies have indicated that 1367 cases were seen in 1978 and 1979. Probably this may represent only half the total number of cases. From this survey it has been possible to draw up a composite map showing the location of patients, which has provided a basis to determine the clinical course of the disease, and for further studies into the complications and management of sickle-cell disease in England and Wales. From a second questionnaire preliminary data about the general management and mortality in England and Wales have been recorded. 相似文献
103.
104.
105.
Composition, stability and electrolyte permeability of Golgi membranes from lactating-rat mammary gland. 总被引:1,自引:1,他引:0 下载免费PDF全文
1. Golgi membrane vesicles, isolated from lactating-rat mammary gland and greatly enriched in galactosyltransferase (EC 2.4.1.22), contained over 40 separate bands of protein, including some periodic acid)(Schiff-staining material and free thiol groups, when analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. 2. The membrane lipids were enriched in phosphatidylcholine, phosphatidylethanolamine and unesterified cholesterol. 3. Membrane fluidity, as monitored by the fluorescence polarization of 1,6-diphenylhexa-1,3,5-triene, increased linearly over 5-37 degrees C. 4. The vesicle membranes were impermeable to lactose over a wide pH range, but admitted electrolytes of molecular weight below about 300. 5. These properties are discussed with respect to other cellular membranes and the secretion of milk products. 相似文献
106.
107.
108.
Summary Total lipids were extracted from 161 redpolls (Acanthis spp.) collected each month of the year from October 1962 to September 1963, in interior Alaska. A lipid index (Weight of ether extract x100/live body weight) was calculated for each sample. Lipids were also extracted from sections of pectoral muscle, livers and hearts representing each month.Body weight and lipid index were significantly positively correlated being highest in January and lowest in September. Total lipid content was significantly inversely correlated with air temperature; the high autumn and spring pre-migratory lipid peaks of migratory species were only weakly expressed in the redpolls. Liver lipid showed a significant annual variation being highest in December and lowest in August, while lipid from heart and pectoral muscle did not vary seasonally.Five birds were held in captivity during spring and summer at a constant temperature of 22°C. Food consumption was 5.1 g/day or 22.4 kcal. The caloric value of the most extensively utilized natural food, birch seed (Betula papyrifera), was determined (5.4–5.5 kcal/g dry wt). When esophageal diverticulae are full (2.0 g wet wt) of birch seeds, the resulting energy yield may sustain an individual for only a fraction of a 24 h winter day in contrast to other arctic herbivores (e.g. ptarmigan, Lagopus sp.) in which a full crop may suffice for the full 24 h period. 相似文献
109.
Zone sedimentation through sucrose gradients was used for preparing Rhizobium bacteroids from lupin nodules and for separating them into slowly and rapidly sedimenting fractions. 相似文献
110.
Factors influencing the interaction between Candida albicans and the polyenoic antibiotics nystatin and amphotericin B have been investigated using a K+-specific electrode to measure polyene-mediated efflux of cellular K+. In batch cultures, sensitivity was a function of culture age. Using continuous (chemostat) cultures, the influence of growth-limiting substrate, specific growth rate, growth temperature and growth pH were examined. Carbon-limited cultures showed the highest sensitivity of those substrates tested, and susceptibility increased with growth rate. Within the range 22 to 42 degrees C, growth at lower temperatures resulted in increased sensitivity, whilst a similar trend was observed when the growth pH of cultures was reduced. Further, under the conditions tested, there were considerable variations in free intracellular K+ concentrations. 相似文献