全文获取类型
收费全文 | 1949343篇 |
免费 | 194023篇 |
国内免费 | 2394篇 |
专业分类
2145760篇 |
出版年
2021年 | 18871篇 |
2018年 | 20830篇 |
2017年 | 19607篇 |
2016年 | 30671篇 |
2015年 | 44573篇 |
2014年 | 52803篇 |
2013年 | 79232篇 |
2012年 | 58568篇 |
2011年 | 52453篇 |
2010年 | 51423篇 |
2009年 | 50481篇 |
2008年 | 47136篇 |
2007年 | 46756篇 |
2006年 | 47880篇 |
2005年 | 48634篇 |
2004年 | 47507篇 |
2003年 | 44577篇 |
2002年 | 42284篇 |
2001年 | 66618篇 |
2000年 | 64867篇 |
1999年 | 56153篇 |
1998年 | 29648篇 |
1997年 | 29562篇 |
1996年 | 28391篇 |
1995年 | 26612篇 |
1994年 | 26084篇 |
1993年 | 25685篇 |
1992年 | 47977篇 |
1991年 | 46299篇 |
1990年 | 44693篇 |
1989年 | 44662篇 |
1988年 | 41369篇 |
1987年 | 39330篇 |
1986年 | 37033篇 |
1985年 | 38451篇 |
1984年 | 34474篇 |
1983年 | 30069篇 |
1982年 | 26588篇 |
1981年 | 24919篇 |
1980年 | 23379篇 |
1979年 | 31032篇 |
1978年 | 26616篇 |
1977年 | 24771篇 |
1976年 | 23334篇 |
1975年 | 24414篇 |
1974年 | 25842篇 |
1973年 | 25985篇 |
1972年 | 22790篇 |
1971年 | 20873篇 |
1970年 | 18197篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
The subcellular distribution of ATP, ADP, creatine phosphate and creatine has been analyzed by fast detergent fractionation of isolated frog heart cells. Digitonin fractionation (0.5 mg/ml, 10 s at 2 degrees C in 20 mM 4-morpholinepropanesulfonic acid/3 mM EDTA/230 mM mannitol medium) was used to separate mitochondria and myofilaments from cytosol. To separate myofilaments from the other cellular compartments. Triton X-100 was used (2%, 15 s in the same medium as digitonin). For either resting or beating cells the total cellular contents of ATP, ADP, creatine phosphate and creatine was similar, nevertheless the O2 consumption was 6-times higher. The compartmentation of these metabolites was also identical. Myofilaments contain 1.1 nmol ADP per mg total cellular proteins. In the cytosolic compartment the metabolite concentrations, all measured in nmol per mg total cellular proteins, were: ATP, 13; ADP, 0.25-0.05; creatine phosphate, 18.5 and creatine, 14. This indicated that the reaction catalyzed by creatine kinase was in a state of (or near) equilibrium. 相似文献
953.
A double antibody radioimmunoassay technique is described for the measurement of anti-zona antibodies in the peripheral plasma of marmosets actively immunized against intact cow zonae pellucidae. The method has been shown to be a reliable, repeatable indicator of antibody titer, enabling direct comparison of the response obtained between marmosets. This is the first report of a procedure describing the active immunization of a primate against zona antigens, and the first time a radioimmunoassay technique has been used to monitor profiles of anti-cow zona antibody production following active immunization. The method should prove to be a useful tool in the evaluation of zona antigens as agents for immunocontraception. 相似文献
954.
955.
Physicians with an interest in pain have long suggested that the poor complain more and have a higher prevalence of neuroticism than do higher social groups. This assumption was tested by analysing the pain patterns in 500 consecutive patients attending a pain relief clinic. Results implied that scores for presenting pain, anxiety, and depression were similar to all social groups. After treatment scores for residual pain were significantly lower in all social classes, with greatest reduction in classes III, IV, and V. Almost identical results were obtained in a subgroup of patients with cancer but not in a subgroup with sciatica. That patients from the lower social classes have a higher perception of pain and are more neurotic than other group is a myth, probably resulting from poor communication between clinicians and patients of dissimilar socioeconomic class. 相似文献
956.
957.
A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships. 相似文献
958.
L E Taplin J P Loveridge 《Comparative biochemistry and physiology. A, Comparative physiology》1988,89(3):443-448
1. Nile crocodiles, reared in fresh water and exposed acutely to seawater, suffer marked dehydration and hypernatraemia. Cloacal urine osmolarity and potassium concentration increased markedly but urine sodium remains low. 2. Hypernatraemia is increased when secretion from the lingual salt glands is prevented. 3. C. niloticus appears not to drink seawater. 4. Similarities in osmoregulatory response between estuarine and Nile crocodiles suggest that the lingual salt glands of C. niloticus are functional in salt water, playing an important role in sodium balance. 5. Significant differences in the function of the renal/cloacal complex of Alligator and Crocodylus emphasize further the differences between these two groups of crocodilian and provide support for the postulated marine ancestry of many or all of the Crocodylidae. 相似文献
959.
B Rayner M Matsukura F Morvan J S Cohen J L Imbach 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1989,310(3):61-64
Oligonucleotide analogs consisting exclusively of alpha-anomeric deoxynucleoside units bridged with phosphorothioate linkages have been synthesized and tested in vitro as antiviral agents against human immunodeficiency virus (HIV) in human T cells. Two 28-mers, an homopolymer alpha-S-dC28 and an oligomer alpha-S-anti-rev complementary to the initiation site of the regulatory viral gene rev exhibited antiviral activities comparable to those reported for the corresponding beta-anomeric phosphorothioate analogs. In contrast, a nuclease-resistant homopolymer, alpha-dC28 was inactive. Their preliminary results would indicate that the origin of oligonucleotide phosphorothioate anti-HIV activity is not exclusively correlated with their higher nuclease resistance. 相似文献
960.
C López-Otin A O Grubb E Méndez 《Biochemical and biophysical research communications》1983,117(1):202-209
An apparently novel human plasma and urinary protein of low molecular weight was isolated from several highly purified preparations of protein HC by gel chromatography and high voltage electrophoresis with a yield of about 8 mg/g. The protein has a molecular weight of about 20,000, neutral electrophoretic mobility at pH 6.5 and a high content of half-cystine. It is associated with a yellow-brown chromophore like protein HC and could be demonstrated in all investigated preparations of isolated human, rabbit and guinea-pig protein HC and alpha 1-microglobulin. 相似文献