全文获取类型
收费全文 | 127682篇 |
免费 | 3304篇 |
国内免费 | 2850篇 |
出版年
2023年 | 386篇 |
2022年 | 452篇 |
2021年 | 1751篇 |
2020年 | 1133篇 |
2019年 | 1398篇 |
2018年 | 12831篇 |
2017年 | 11343篇 |
2016年 | 8688篇 |
2015年 | 2716篇 |
2014年 | 2786篇 |
2013年 | 3007篇 |
2012年 | 7391篇 |
2011年 | 15502篇 |
2010年 | 13594篇 |
2009年 | 9608篇 |
2008年 | 11417篇 |
2007年 | 12809篇 |
2006年 | 1687篇 |
2005年 | 1702篇 |
2004年 | 2020篇 |
2003年 | 1918篇 |
2002年 | 1554篇 |
2001年 | 957篇 |
2000年 | 868篇 |
1999年 | 701篇 |
1998年 | 400篇 |
1997年 | 369篇 |
1996年 | 369篇 |
1995年 | 340篇 |
1994年 | 339篇 |
1993年 | 247篇 |
1992年 | 376篇 |
1991年 | 312篇 |
1990年 | 320篇 |
1989年 | 268篇 |
1988年 | 208篇 |
1987年 | 187篇 |
1986年 | 153篇 |
1985年 | 135篇 |
1984年 | 129篇 |
1983年 | 112篇 |
1982年 | 79篇 |
1981年 | 60篇 |
1979年 | 74篇 |
1978年 | 54篇 |
1977年 | 52篇 |
1975年 | 64篇 |
1973年 | 50篇 |
1972年 | 287篇 |
1971年 | 310篇 |
排序方式: 共有10000条查询结果,搜索用时 963 毫秒
991.
992.
Cobra venom (Naja naja atra) and its fractions obtained by ammonium sulfate precipitation were subjected to chromatography on CM-Cellulose colum. A highly purified cobrotoxin obtained by the repeated chromatography on preparative CM-Cellulose column was 6.7 times more toxic than the original cobra venom. The toxin was detoxified by a bifunctional reagent, glutaraldehyde, to about 99.8% and utilized for immunization in animals. Mice received 4 weekly immunization with detoxified cobrotoxin and challenged one week after the last injection showed 60% protection in rabbits by immunization with detoxified cobrotoxin reached 360 LD50 neutralizing level against the cobra venom within 30 days. The results indicate that it is feasible and promising to prepare potent antivenin in animals by glutaraldehyde-treated cobrotoxin. 相似文献
993.
The H-2.7 antigen in normal mouse serum can be passively adsorbed to H-2.7– erythrocytes in 10 percent sucrose (low ionic strength) solution. This antigen can also be stripped off the H-2.7+ erythrocytes under the same conditions provided the H-2.7+normal serum is absent. The stripped red blood cells can regain the H-2.7 antigen upon reincubation with H-2.7+ normal serum. The attachment of the H-2.7 antigen to erythrocytes probably occurs via a specific receptor.Abbreviations used in this paper BSA
bovine serum albumin
- B10
C57BL/10Sn
- HA
hemagglutination
- LIS
low ionic strength solution
- NMS
normal mouse serum
- PBS
phosphate-buffered saline
- PVP
polyvinylpyrrolidone
- RBCs
red blood cells 相似文献
994.
Shyi Yi Huang Charles W. Berry Joseph T. Newman William H. Cooper Nannepaga Y. Zachariah 《Mycopathologia》1979,67(1):55-58
Rabbits were employed as experimental models to evaluate a solid-phase radioimmunoassay (RIA) method for the diagnosis of systemic candidiasis. Ten rabbits were inoculated subcutaneously to mimic superficial candidiasis and were found to produce no antibodies to Candida as determined by both immunodiffusion and RIA procedures. However, 94 per cent of 18 rabbits systemically infected by intravenous injection of Candida cells were observed to produce antibody as assessed by the RIA technique. These data encourage further tests with human sera and the continued development of this RIA procedure as a useful tool in the early serodiagnosis of systemic candidiasis. 相似文献
995.
Interferon induction by mismatched analogues of polyinosinic acid . polycytidylic acid [(Ix,U)n.(C)n]. 总被引:1,自引:0,他引:1 下载免费PDF全文
Interruption of the (I)n strand of (I)n.(C)n by unpaired bases [(U)] yielded mismatched analogues, (Ix,U)n.(C)n which were still effective as inducers of interferon, provided the I:U ratio (x) was equal or greater than 10. In highly sensitive interferon-induction systems such as primary rabbit kidney cells and human skin fibroblasts superinduced with cycloheximide and actinomycin D, (I10,U)n.(C)n and (I50,U)n.(C)n proved nearly as active as (I)n.(C)n. By virtue of their increased susceptibility to degradation by nucleases, (Ix,U)n.(C)n complexes with 10 less than or equal to x less than or equal to 50 may be expected not to persist as long in biological fluids as (I)n.(C)n, hence to induce fewer side effects. 相似文献
996.
In previous studies on the quaternary structure of Na+,K+-ATPase, cupric-phenanthroline complex (CP) has been used for the cross-linking of the enzyme subunits. Here we show that the same products obtained in the presence of CP (α,α-dimer, α,β-dimer, and products of higher molecular weight) are also obtained when the enzyme is exposed to Cu2+ without o-phenanthroline. The α,β-dimer (but not the α,α-dimer) is dissociated in the presence of EDTA; indicating that this product is not the result of the covalent cross-linking of the subunits through a disulfide bond. The nature of the α,α-dimer remains to be determined. The findings suggest that the results of “cross-linking” experiments with CP should be interpreted with caution until the products are more clearly identified. 相似文献
997.
A patient with cervical carcinoma was found to have selective IgA deficiency. The intact cell-mediated immunity, normal levels of IgG and IgM, and the absence of serum and salivary IgA established the diagnosis. Contrary to those of normal persons, salivary IgM was elevated and salivary IgA was not detectable in this patient. The patient had no signs attributable to IgA deficiency, but she always had dryness of the mouth. The association between cervical carcinoma and selective IgA deficiency was discussed. 相似文献
998.
999.
1000.